This document analyzes the orientations of 130 planetary nebulae (PNe) in the Galactic Bulge to investigate whether there is a preferred alignment. It finds that while the full sample shows a uniform distribution, the bipolar PNe exhibit a non-uniform distribution with a mean orientation along the Galactic plane at a 90 degree position angle, significant at the 0.001 level. This indicates that the orbital planes of binary systems in old stars are oriented perpendicular to the Galactic plane, likely due to strong magnetic fields during star formation that influenced the angular momentum vectors.
A nearby yoiung_m_dwarf_with_wide_possibly_planetary_m_ass_companionSérgio Sacani
This document summarizes the identification of two young objects, TYC 9486-927-1 and 2MASS J21265040−8140293, as a likely very wide binary system. It presents revised astrometry showing they have common proper motion. Spectroscopy of the secondary yields a radial velocity consistent with the primary. Analysis of lithium absorption and kinematics suggests an age range of 10-45 Myr, with the secondary having an estimated mass in the planetary mass regime. If confirmed, this would be the widest known exoplanet system at over 4500 AU separation.
Probing the innermost_regions_of_agn_jets_and_their_magnetic_fields_with_radi...Sérgio Sacani
Desde 1974, observações feitas com o chamado Long Baseline Interferometry, ou VLBI, combinaram sinais de um objeto cósmico recebidos em diferentes rádio telescópios espalhados pelo globo para criar uma antena com o tamanho equivalente à maior separação entre elas. Isso fez com que fosse possível fazer imagens com uma nitidez sem precedentes, com uma resolução 1000 vezes melhor do que Hubble consegue na luz visível. Agora, uma equipe internacional de astrônomos quebrou todos os recordes combinando 15 rádio telescópios na Terra e a antena de rádio da missão RadioAstron, da agência espacial russa, na órbita da Terra. O trabalho, liderado pelo Instituto de Astrofísica de Andalucía, o IAA-CSIC, forneceu novas ideias sobre a natureza das galáxias ativas, onde um buraco negro extremamente massivo engole a matéria ao redor enquanto simultaneamente emite um par de jatos de partículas de alta energia e campos magnéticos a velocidades próximas da velocidade da luz.
Observações feitas no comprimento de onda das micro-ondas são essenciais para explorar esses jatos, já que os elétrons de alta energia se movendo em campos magnéticos são mais proficientes em produzir micro-ondas. Mas a maioria das galáxias ativas com jatos brilhantes estão a bilhões de anos-luz de distância da Terra, de modo que esses jatos são minúsculos no céu. Desse modo a alta resolução é essencial para observar esses jatos em ação e então revelar fenômenos como as ondas de choque e a turbulência que controla o quanto de luz é produzida num dado tempo. “Combinando pela primeira vez rádio telescópios na Terra com rádio telescópios no espaço, operando na máxima resolução, tem permitido que a nossa equipe crie uma antena que tem um tamanho equivalente a 8 vezes o diâmetro da Terra, correspondendo a 20 micro arcos de segundo”, disse José L; Gómez, o líder da equipe no Instituto de Astrofísica de Andalucía, IAA-CSIC.
This document summarizes a blind HI survey of the southern Milky Way zone of avoidance conducted with the Parkes radio telescope. The survey detected 883 galaxies at Galactic longitudes 212° < l < 36° and latitudes |b| < 5° to a sensitivity of 6 mJy per 27 km/s channel. Fifty-one percent of detections had known optical/near-infrared counterparts, while 27% had new counterparts identified. The survey delineated large-scale structures in the Puppis and Great Attractor regions for the first time. Several newly identified galaxy concentrations and clusters were revealed that help trace the Great Attractor Wall.
The document describes measurements of the proper motion of the Andromeda Galaxy (M31) using Hubble Space Telescope imaging data from multiple fields observed at two epochs separated by 5-7 years. Background galaxies in the images are used as stationary reference objects to measure the displacement of thousands of M31 stars between epochs. This allows determining M31's absolute proper motion with an accuracy of 12 microarcseconds per year, providing crucial information about M31 and the Local Group's dynamics and future evolution.
Spectral and morphological_analysis_of_the_remnant_of_supernova_1987_a_with_a...Sérgio Sacani
The document provides a spectral and morphological analysis of the remnant of Supernova 1987A using data from the Australia Telescope Compact Array (ATCA) and the Atacama Large Millimeter/submillimeter Array (ALMA). ALMA images from 94 GHz to 672 GHz reveal non-thermal synchrotron and thermal dust emission components. The analysis shows a decreasing east-west asymmetry with frequency, attributed to shorter synchrotron lifetimes at high frequencies. Across the radio to far-infrared transition, excess emission is seen that could be due to a second synchrotron component, implying a pulsar wind nebula in the remnant interior.
Probing the jet_base_of_blazar_pks1830211_from_the_chromatic_variability_of_i...Sérgio Sacani
This document summarizes ALMA observations of the blazar PKS 1830-211 taken over multiple epochs in 2012. The blazar is lensed by a foreground galaxy, producing two resolved images (NE and SW) separated by 1". The observations were taken at frequencies corresponding to 350-1050 GHz in the blazar rest frame. Analysis of the flux ratio between the two images over time and frequency revealed a remarkable frequency-dependent behavior, implying a "chromatic structure" in the blazar jet. This is interpreted as evidence for a "core-shift effect" caused by plasmon ejection very near the base of the jet. The observations provide a unique probe of activity in the region where plasma acceleration occurs in blazar
The closest known_flyby_of_a_star_to_the_solar_systemSérgio Sacani
The closest known flyby of a star to the solar system was a low-mass binary star system called WISE J072003.20-084651.2, also known as "Scholz's star". By integrating the orbits of this 0.15 solar mass binary system and the Sun, astronomers found that it passed within 0.25 parsecs (52,000 AU) of the Sun about 70,000 years ago, within the outer bounds of the Oort Cloud. This is the closest encounter with a star to the solar system that has been well-constrained in distance and velocity. While the flyby likely had a negligible impact on long-period comets from the Oort Cloud, it highlights the possibility
This document summarizes the detection of a super-Earth planet orbiting the star GJ 832. Radial velocity data from three telescopes revealed a planet, GJ 832c, with an orbital period of 35.68 days and a minimum mass of 5.4 Earth masses. GJ 832c has a low eccentricity orbit of 0.18 near the inner edge of the star's habitable zone. However, given its large mass, the planet likely has a massive atmosphere that could render it uninhabitable. The GJ 832 system resembles a miniature version of our solar system, with an interior potentially rocky planet and a distant gas giant.
A nearby yoiung_m_dwarf_with_wide_possibly_planetary_m_ass_companionSérgio Sacani
This document summarizes the identification of two young objects, TYC 9486-927-1 and 2MASS J21265040−8140293, as a likely very wide binary system. It presents revised astrometry showing they have common proper motion. Spectroscopy of the secondary yields a radial velocity consistent with the primary. Analysis of lithium absorption and kinematics suggests an age range of 10-45 Myr, with the secondary having an estimated mass in the planetary mass regime. If confirmed, this would be the widest known exoplanet system at over 4500 AU separation.
Probing the innermost_regions_of_agn_jets_and_their_magnetic_fields_with_radi...Sérgio Sacani
Desde 1974, observações feitas com o chamado Long Baseline Interferometry, ou VLBI, combinaram sinais de um objeto cósmico recebidos em diferentes rádio telescópios espalhados pelo globo para criar uma antena com o tamanho equivalente à maior separação entre elas. Isso fez com que fosse possível fazer imagens com uma nitidez sem precedentes, com uma resolução 1000 vezes melhor do que Hubble consegue na luz visível. Agora, uma equipe internacional de astrônomos quebrou todos os recordes combinando 15 rádio telescópios na Terra e a antena de rádio da missão RadioAstron, da agência espacial russa, na órbita da Terra. O trabalho, liderado pelo Instituto de Astrofísica de Andalucía, o IAA-CSIC, forneceu novas ideias sobre a natureza das galáxias ativas, onde um buraco negro extremamente massivo engole a matéria ao redor enquanto simultaneamente emite um par de jatos de partículas de alta energia e campos magnéticos a velocidades próximas da velocidade da luz.
Observações feitas no comprimento de onda das micro-ondas são essenciais para explorar esses jatos, já que os elétrons de alta energia se movendo em campos magnéticos são mais proficientes em produzir micro-ondas. Mas a maioria das galáxias ativas com jatos brilhantes estão a bilhões de anos-luz de distância da Terra, de modo que esses jatos são minúsculos no céu. Desse modo a alta resolução é essencial para observar esses jatos em ação e então revelar fenômenos como as ondas de choque e a turbulência que controla o quanto de luz é produzida num dado tempo. “Combinando pela primeira vez rádio telescópios na Terra com rádio telescópios no espaço, operando na máxima resolução, tem permitido que a nossa equipe crie uma antena que tem um tamanho equivalente a 8 vezes o diâmetro da Terra, correspondendo a 20 micro arcos de segundo”, disse José L; Gómez, o líder da equipe no Instituto de Astrofísica de Andalucía, IAA-CSIC.
This document summarizes a blind HI survey of the southern Milky Way zone of avoidance conducted with the Parkes radio telescope. The survey detected 883 galaxies at Galactic longitudes 212° < l < 36° and latitudes |b| < 5° to a sensitivity of 6 mJy per 27 km/s channel. Fifty-one percent of detections had known optical/near-infrared counterparts, while 27% had new counterparts identified. The survey delineated large-scale structures in the Puppis and Great Attractor regions for the first time. Several newly identified galaxy concentrations and clusters were revealed that help trace the Great Attractor Wall.
The document describes measurements of the proper motion of the Andromeda Galaxy (M31) using Hubble Space Telescope imaging data from multiple fields observed at two epochs separated by 5-7 years. Background galaxies in the images are used as stationary reference objects to measure the displacement of thousands of M31 stars between epochs. This allows determining M31's absolute proper motion with an accuracy of 12 microarcseconds per year, providing crucial information about M31 and the Local Group's dynamics and future evolution.
Spectral and morphological_analysis_of_the_remnant_of_supernova_1987_a_with_a...Sérgio Sacani
The document provides a spectral and morphological analysis of the remnant of Supernova 1987A using data from the Australia Telescope Compact Array (ATCA) and the Atacama Large Millimeter/submillimeter Array (ALMA). ALMA images from 94 GHz to 672 GHz reveal non-thermal synchrotron and thermal dust emission components. The analysis shows a decreasing east-west asymmetry with frequency, attributed to shorter synchrotron lifetimes at high frequencies. Across the radio to far-infrared transition, excess emission is seen that could be due to a second synchrotron component, implying a pulsar wind nebula in the remnant interior.
Probing the jet_base_of_blazar_pks1830211_from_the_chromatic_variability_of_i...Sérgio Sacani
This document summarizes ALMA observations of the blazar PKS 1830-211 taken over multiple epochs in 2012. The blazar is lensed by a foreground galaxy, producing two resolved images (NE and SW) separated by 1". The observations were taken at frequencies corresponding to 350-1050 GHz in the blazar rest frame. Analysis of the flux ratio between the two images over time and frequency revealed a remarkable frequency-dependent behavior, implying a "chromatic structure" in the blazar jet. This is interpreted as evidence for a "core-shift effect" caused by plasmon ejection very near the base of the jet. The observations provide a unique probe of activity in the region where plasma acceleration occurs in blazar
The closest known_flyby_of_a_star_to_the_solar_systemSérgio Sacani
The closest known flyby of a star to the solar system was a low-mass binary star system called WISE J072003.20-084651.2, also known as "Scholz's star". By integrating the orbits of this 0.15 solar mass binary system and the Sun, astronomers found that it passed within 0.25 parsecs (52,000 AU) of the Sun about 70,000 years ago, within the outer bounds of the Oort Cloud. This is the closest encounter with a star to the solar system that has been well-constrained in distance and velocity. While the flyby likely had a negligible impact on long-period comets from the Oort Cloud, it highlights the possibility
This document summarizes the detection of a super-Earth planet orbiting the star GJ 832. Radial velocity data from three telescopes revealed a planet, GJ 832c, with an orbital period of 35.68 days and a minimum mass of 5.4 Earth masses. GJ 832c has a low eccentricity orbit of 0.18 near the inner edge of the star's habitable zone. However, given its large mass, the planet likely has a massive atmosphere that could render it uninhabitable. The GJ 832 system resembles a miniature version of our solar system, with an interior potentially rocky planet and a distant gas giant.
Water vapour absorption_in_the_clear_atmosphere_of_a_neptune_sized_exoplanetSérgio Sacani
This document summarizes research on the transmission spectrum of the exoplanet HAT-P-11b, a Neptune-sized planet. Observations from the Hubble Space Telescope and Spitzer Space Telescope detected water vapor absorption in the planet's atmosphere at a wavelength of 1.4 micrometers. Analysis of the spectrum indicates the atmosphere is predominantly clear down to 1 mbar and has a hydrogen abundance similar to solar values. Atmospheric modeling suggests a metallicity around 190 times that of the Sun's, in agreement with core accretion planet formation theories. This makes HAT-P-11b the smallest exoplanet to date with a detected molecular signature in its atmosphere, providing new insights into the composition and formation of Neptune-sized
The Internal Structure of Asteroid (25143) Itokawa as Revealed by Detection o...WellingtonRodrigues2014
- The authors detected an acceleration in the rotation rate of asteroid (25143) Itokawa through photometric observations spanning 2001 to 2013.
- By measuring rotational phase offsets between observed and modeled lightcurves, they found a YORP acceleration of 3.54 ± 0.38 × 10−8 rad day−2, equivalent to a decrease in the asteroid's rotation period of about 45 ms per year.
- Thermophysical modeling of the detailed shape model from the Hayabusa spacecraft could not reconcile the observed YORP strength unless the asteroid's center of mass is shifted by about 21 m along its long axis. This suggests Itokawa has two components with different densities that merged, either from a
Evidence for a_distant_giant_planet_in_the_solar_systemSérgio Sacani
A descoberta de um novo planeta, atualmente não é uma manchete que chama tanto assim a atenção das pessoas. Muito disso, graças ao Telescópio Espacial Kepler, que já descobriu quase 2000 exoplanetas e todo instante uma nova descoberta é anunciada, certo? Mais ou menos, a descoberta anunciada hoje, dia 20 de Janeiro de 2016, é um pouco diferente, pois não se trata de um exoplaneta, e sim de um novo planeta no Sistema Solar, e esse é um fato que intriga os astrônomos a muitos e muitos anos.
Porém, temos que ir com calma com esses anúncios. No artigo aceito para publicação no The Astronomical Journal (artigo no final do post), os autores, Mike Brown e Konstantin Batygin, do Instituto de Tecnologia da Califórnia, apresentaram o que eles dizem ser evidências circunstâncias fortes para a existência de um grande planeta ainda não descoberto, talvez, com uma massa 10 vezes a massa da Terra, orbitando os confins do nosso Sistema Solar, muito além da órbita de Plutão. Os cientistas inferiram sua presença, por meio de anomalias encontradas nas órbitas de seis objetos do chamado Cinturão de Kuiper.
O objeto, que os pesquisadores estão chamando de Planeta Nove, não chega muito perto do Sol, no ponto mais próximo da sua órbita ele fica a 30.5 bilhões de quilômetros, ou seja, cinco vezes a distância entre o Sol e Plutão. Apesar do seu grande tamanho, ele é muito apagado, e por isso ninguém até o momento conseguiu observá-lo.
Não existe ainda uma confirmação observacional da descoberta, mas as evidências são tão fortes que fizeram com que outros especialistas como Chad Trujilo do Observatório Gemini no Havaí e David Nesvorny, do Southwest Research Institute em Boulder no Colorado, ficassem impressionados e bem convencidos de que deve mesmo haver um grande planeta nas fronteiras da nossa vizinhança cósmica.
The document presents observations of the starburst galaxy NGC 253 using near-infrared imaging and spectroscopy as well as mid-infrared spectroscopy. The observations are used to derive physical properties of the starburst such as the star formation rate, stellar population, and evolutionary stage. Evolutionary synthesis modeling is applied to interpret the observations and show that the starburst in NGC 253 is in a late phase, has been ongoing for 20-30 million years, and is consistent with a modified Salpeter initial mass function.
Todo mundo sabe que os raios produzidos pela Estrela da Morte em Guerra nas Estrelas não pode existir na vida real, porém no universo existem fenômenos que as vezes conseguem superar até a mais surpreendente ficção.
A galáxia Pictor A, é um desses objetos que possuem fenômenos tão espetaculares quanto aqueles exibidos no cinema. Essa galáxia localiza-se a cerca de 500 milhões de anos-luz da Terra e possui um buraco negro supermassivo no seu centro. Uma grande quantidade de energia gravitacional é lançada, à medida que o material cai em direção ao horizonte de eventos, o ponto sem volta ao redor do buraco negro. Essa energia produz um enorme jato de partículas que viajam a uma velocidade próxima da velocidade da luz no espaço intergaláctico, chamado de jato relativístico.
Para obter imagens desse jato, os cientistas usaram o Observatório de Raios-X Chandra, da NASA várias vezes durante 15 anos. Os dados do Chandra, apresentados em azul nas imagens, foram combinados com os dados obtidos em ondas de rádio a partir do Australia Telescope Compact Array, e são aparesentados em vermelho nas imagens.
Confirmation of the_ogle_planet_signature_and_its_characteristics_with_lens_s...Sérgio Sacani
O Telescópio Espacial Hubble e o Observatório W. M. Keck, no Havaí, fizeram confirmações independentes de um exoplaneta orbitando sua estrela central de uma distância bem grande. O planeta foi descoberto através de uma técnica chamada de microlente gravitacional.
Essa descoberta traz uma nova peça para o processo de caçada de exoplanetas: para descobrir planetas longe de suas estrelas, como Júpiter e Saturno estão do Sol. Os resultados obtidos pelo Hubble e pelo Keck apareceram em dois artigos da edição de 30 de Julho de 2015 do The Astrophysical Journal.
A grande maioria dos exoplanetas catalogados são aqueles localizados bem perto de suas estrelas, isso acontece porque as técnicas atuais de se caçar exoplanetas favorecem a descoberta de planetas com curtos períodos orbitais. Mas esse não é o caso da técnica de microlente gravitacional, que pode encontrar planetas mais frios e mais distantes com órbitas de longo período que outros métodos não são capazes de detectar.
High-resolution UV/Optical/IR Imaging of Jupiter in 2016–2019Sérgio Sacani
Imaging observations of Jupiter with high spatial resolution were acquired beginning in 2016, with a cadence of 53
days to coincide with atmospheric observations of the Juno spacecraft during each perijove pass. The Wide Field
Camera 3 (WFC3) aboard the Hubble Space Telescope (HST) collected Jupiter images from 236 to 925 nm in 14
filters. The Near-Infrared Imager (NIRI) at Gemini North imaged Jovian thermal emission using a lucky-imaging
approach (co-adding the sharpest frames taken from a sequence of short exposures), using the M′ filter at 4.7 μm.
We discuss the data acquisition and processing and an archive collection that contains the processed WFC3 and
NIRI data (doi:10.17909/T94T1H). Zonal winds remain steady over time at most latitudes, but significant
evolution of the wind profile near 24°N in 2016 and near 15°S in 2017 was linked with convective superstorm
eruptions. Persistent mesoscale waves were seen throughout the 2016–2019 period. We link groups of lightning
flashes observed by the Juno team with water clouds in a large convective plume near 15°S and in cyclones near
35°N–55°N. Thermal infrared maps at the 10.8 micron wavelength obtained at the Very Large Telescope show
consistent high brightness temperature anomalies, despite a diversity of aerosol properties seen in the HST data.
Both WFC3 and NIRI imaging reveal depleted aerosols consistent with downwelling around the periphery of the
15°S storm, which was also observed by the Atacama Large Millimeter/submillimeter Array. NIRI imaging of
the Great Red Spot shows that locally reduced cloud opacity is responsible for dark features within the vortex. The
HST data maps multiple concentric polar hoods of high-latitude hazes.
Toward a new_distance_to_the_active_galaxy_ngc4258Sérgio Sacani
This document reports on measurements of centripetal accelerations of maser spectral components in the active galaxy NGC 4258 using data from 51 epochs spanning 1994 to 2004. Accelerations of high-velocity maser emission indicate an origin within 13 degrees of the disk midline. Accelerations do not support a model of trailing shocks from spiral arms but find evidence of spiral structure with a wavelength of 0.75 mas. Accelerations of low-velocity emission are consistent with originating from a concave region where the thin disk is tangent to the line of sight.
A magnetar-powered X-ray transient as the aftermath of a binary neutron-star ...Sérgio Sacani
Mergers of neutron stars are known to be associated with short γ-ray
bursts1–4
. If the neutron-star equation of state is sufficiently stiff
(that is, the pressure increases sharply as the density increases), at
least some such mergers will leave behind a supramassive or even a
stable neutron star that spins rapidly with a strong magnetic field5–8
(that is, a magnetar). Such a magnetar signature may have been
observed in the form of the X-ray plateau that follows up to half
of observed short γ-ray bursts9,10. However, it has been expected
that some X-ray transients powered by binary neutron-star mergers
may not be associated with a short γ-ray burst11,12. A fast X-ray
transient (CDF-S XT1) was recently found to be associated with a
faint host galaxy, the redshift of which is unknown13. Its X-ray and
host-galaxy properties allow several possible explanations including
a short γ-ray burst seen off-axis, a low-luminosity γ-ray burst at
high redshift, or a tidal disruption event involving an intermediatemass black hole and a white dwarf13. Here we report a second X-ray
transient, CDF-S XT2, that is associated with a galaxy at redshift
z = 0.738 (ref. 14). The measured light curve is fully consistent with
the X-ray transient being powered by a millisecond magnetar. More
intriguingly, CDF-S XT2 lies in the outskirts of its star-forming host
galaxy with a moderate offset from the galaxy centre, as short γ-ray
bursts often do15,16. The estimated event-rate density of similar
X-ray transients, when corrected to the local value, is consistent
with the event-rate density of binary neutron-star mergers that is
robustly inferred from the detection of the gravitational-wave event
GW170817.
We present long-baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of
the 870 m continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that
trace millimeter-sized particles down to spatial scales as small as 1 AU (20 mas). These data reveal
a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli
(1{6AU) with modest contrasts (5{30%). We associate these features with concentrations of solids
that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima.
No signicant non-axisymmetric structures are detected. Some of the observed features occur near
temperatures that may be associated with the condensation fronts of major volatile species, but the
relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the
so-called zonal
ows). Other features, particularly a narrow dark annulus located only 1 AU from the
star, could indicate interactions between the disk and young planets. These data signal that ordered
substructures on AU scales can be common, fundamental factors in disk evolution, and that high
resolution microwave imaging can help characterize them during the epoch of planet formation.
Keywords: protoplanetary disks | planet-disk interactions | stars: individual (TW Hydrae)
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of
1011.5 K. Relativistic boosting can increase its observed value, but apparent brightness temperatures
much in excess of 1013 K are inaccessible using ground-based very long baseline interferometry (VLBI)
at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission
RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as
small as 26 µas (2.7 light months) and brightness temperature in excess of 1013 K. These measurements
challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive
black holes and require a much higher Doppler factor than what is determined from jet apparent
kinematics.
Keywords: galaxies: active — galaxies: jets — radio continuum: galaxies — techniques: interferometric
— quasars: individual (3C 273)
1) The document analyzes data from the SuperWASP-South telescope to classify four stars - VSX013997, 017283, 026353, and 091251.
2) The author cleaned the raw data, used Period04 to identify pulsation frequencies for each star, and created phased light curves to classify the stars.
3) Based on the periods, amplitudes, and light curve shapes, the author classified three stars as RRab subtype RR Lyrae variables and one star as a rotating ellipsoidal variable.
This document summarizes research on determining temperatures, luminosities, and masses of the coldest known brown dwarfs. The key findings are:
1) Precise distances were measured for a sample of late-T and Y dwarfs using Spitzer Space Telescope astrometry, allowing accurate calculation of absolute fluxes, luminosities, and temperatures.
2) Y0 dwarfs were found to have temperatures of 400-450 K, significantly warmer than previous estimates, and masses of 5-20 times Jupiter's mass.
3) While having similar temperatures, Y dwarfs showed diverse spectral energy distributions, suggesting temperature alone does not determine spectra. Physical properties like gravity, clouds and chemistry also influence spectra.
The open cluster_ngc6520_and_the_nearby_dark_molecular_cloud_barnard_86Sérgio Sacani
This document presents optical photometry and CO observations of the open cluster NGC 6520 and nearby dark molecular cloud Barnard 86. Analysis of the optical data finds the cluster radius is 1.0±0.5 arcmin, smaller than previous estimates. The cluster age is estimated to be 150±50 Myr with reddening of EB−V =0.42±0.10. The distance from the Sun is estimated to be 1900±100 pc, larger than previous estimates. CO observations are used to derive basic properties of Barnard 86 under the assumption it lies at the same distance as the cluster.
Observation of Bose–Einstein condensates in an Earth-orbiting research labSérgio Sacani
Quantum mechanics governs the microscopic world, where low mass and momentum
reveal a natural wave–particle duality. Magnifying quantum behaviour to
macroscopic scales is a major strength of the technique of cooling and trapping
atomic gases, in which low momentum is engineered through extremely low
temperatures. Advances in this feld have achieved such precise control over atomic
systems that gravity, often negligible when considering individual atoms, has
emerged as a substantial obstacle. In particular, although weaker trapping felds
would allow access to lower temperatures1,2
, gravity empties atom traps that are too
weak. Additionally, inertial sensors based on cold atoms could reach better
sensitivities if the free-fall time of the atoms after release from the trap could be made
longer3
. Planetary orbit, specifcally the condition of perpetual free-fall, ofers to lift
cold-atom studies beyond such terrestrial limitations. Here we report production of
rubidium Bose–Einstein condensates (BECs) in an Earth-orbiting research laboratory,
the Cold Atom Lab. We observe subnanokelvin BECs in weak trapping potentials with
free-expansion times extending beyond one second, providing an initial
demonstration of the advantages ofered by a microgravity environment for
cold-atom experiments and verifying the successful operation of this facility. With
routine BEC production, continuing operations will support long-term investigations
of trap topologies unique to microgravity4,5
, atom-laser sources6
, few-body physics7,8
and pathfnding techniques for atom-wave interferometry9–12
WHERE IS THE FLUX GOING? THE LONG-TERM PHOTOMETRIC VARIABILITY OF BOYAJIAN’S ...Sérgio Sacani
We present ∼ 800 days of photometric monitoring of Boyajian’s Star (KIC 8462852) from the AllSky
Automated Survey for Supernovae (ASAS-SN) and ∼ 4000 days of monitoring from the All Sky
Automated Survey (ASAS). We show that from 2015 to the present the brightness of Boyajian’s Star
has steadily decreased at a rate of 6.3 ± 1.4 mmag yr−1
, such that the star is now 1.5% fainter than it
was in February 2015. Moreover, the longer time baseline afforded by ASAS suggests that Boyajian’s
Star has also undergone two brightening episodes in the past 11 years, rather than only exhibiting a
monotonic decline. We analyze a sample of ∼ 1000 comparison stars of similar brightness located in
the same ASAS-SN field and demonstrate that the recent fading is significant at & 99.4% confidence.
The 2015 − 2017 dimming rate is consistent with that measured with Kepler data for the time period
from 2009 to 2013. This long-term variability is difficult to explain with any of the physical models
for the star’s behavior proposed to date
New results from_an_old_friend_the_crab_nebula _and_its_pulsarSérgio Sacani
1. Recent Chandra observations of the Crab Nebula system show that the southern jet has evolved over time, with changes in position, width, and spectrum as a function of distance from the pulsar.
2. Chandra images reveal that the pulsar is not centered within the inner ring, suggesting that the ring may lie on the pulsar's axis of symmetry but at a latitude of about 5 degrees.
3. Phase-resolved spectroscopy of the pulsar with Chandra shows similarities in the variation of X-ray and gamma-ray spectral indices with pulse phase, posing a challenge to theoretical models.
4. Chandra observations were used to search for an X-ray signature of the site
Imaging the dust_sublimation_front_of_a_circumbinary_diskSérgio Sacani
Aims. We present the first near-IR milli-arcsecond-scale image of a post-AGB binary that is surrounded by hot circumbinary dust.
Methods. A very rich interferometric data set in six spectral channels was acquired of IRAS 08544-4431 with the new RAPID camera
on the PIONIER beam combiner at the Very Large Telescope Interferometer (VLTI). A broadband image in the H-band was reconstructed
by combining the data of all spectral channels using the SPARCO method.
Results. We spatially separate all the building blocks of the IRAS 08544-4431 system in our milliarcsecond-resolution image. Our
dissection reveals a dust sublimation front that is strikingly similar to that expected in early-stage protoplanetary disks, as well as an
unexpected flux signal of 4% from the secondary star. The energy output from this companion indicates the presence of a compact
circum-companion accretion disk, which is likely the origin of the fast outflow detected in H.
Conclusions. Our image provides the most detailed view into the heart of a dusty circumstellar disk to date. Our results demonstrate
that binary evolution processes and circumstellar disk evolution can be studied in detail in space and over time.
The benefit of hindsight in observational science - Retrospective seismologica...Elizabeth Entwistle
This document discusses a new technique called retrospective seismology that allows seismic recordings to be obtained at times before, during, or after a seismometer was physically installed using seismic interferometry theory. As an example, the document constructs seismograms from two past earthquakes using data from a seismometer installed afterwards. This allows novel information to be obtained about both the earth structure and earthquake sources. The key is that ambient seismic noise recordings can be used to synthesize deterministic signals from earthquake sources. This counterintuitive finding provides a new way to retrospectively observe seismic events.
High precision abundances_of_the_old_solar_twin_insights_on_li_depletion_from...Sérgio Sacani
- The document presents the results of a chemical abundance analysis of the old solar twin star HIP 102152 (8.2 Gyr) and the younger solar twin 18 Sco (2.9 Gyr) using high-resolution UVES spectra.
- Abundances of 21 elements were derived for HIP 102152 with precisions up to 0.004 dex relative to the Sun. The metallicity of HIP 102152 was found to be nearly solar at [Fe/H] = -0.013.
- Elemental abundances as a function of condensation temperature reveal a solar abundance pattern for HIP 102152, unlike most solar twins. Its pattern most closely matches the Sun. The Li abundance
Dissecting x ray_emitting_gas_around_the_center_of_our_galaxySérgio Sacani
1) The Chandra X-ray Observatory was used to observe the supermassive black hole at the center of the Milky Way, Sgr A*, for a total of 3 megaseconds.
2) The observations revealed extended X-ray emission around Sgr A* that aligns spatially with a surrounding disk of massive stars.
3) Spectral analysis ruled out low-mass stars as the origin of the X-ray emission and instead found evidence that the emission is from a radiatively inefficient accretion flow onto the black hole, with an outflow present.
Water vapour absorption_in_the_clear_atmosphere_of_a_neptune_sized_exoplanetSérgio Sacani
This document summarizes research on the transmission spectrum of the exoplanet HAT-P-11b, a Neptune-sized planet. Observations from the Hubble Space Telescope and Spitzer Space Telescope detected water vapor absorption in the planet's atmosphere at a wavelength of 1.4 micrometers. Analysis of the spectrum indicates the atmosphere is predominantly clear down to 1 mbar and has a hydrogen abundance similar to solar values. Atmospheric modeling suggests a metallicity around 190 times that of the Sun's, in agreement with core accretion planet formation theories. This makes HAT-P-11b the smallest exoplanet to date with a detected molecular signature in its atmosphere, providing new insights into the composition and formation of Neptune-sized
The Internal Structure of Asteroid (25143) Itokawa as Revealed by Detection o...WellingtonRodrigues2014
- The authors detected an acceleration in the rotation rate of asteroid (25143) Itokawa through photometric observations spanning 2001 to 2013.
- By measuring rotational phase offsets between observed and modeled lightcurves, they found a YORP acceleration of 3.54 ± 0.38 × 10−8 rad day−2, equivalent to a decrease in the asteroid's rotation period of about 45 ms per year.
- Thermophysical modeling of the detailed shape model from the Hayabusa spacecraft could not reconcile the observed YORP strength unless the asteroid's center of mass is shifted by about 21 m along its long axis. This suggests Itokawa has two components with different densities that merged, either from a
Evidence for a_distant_giant_planet_in_the_solar_systemSérgio Sacani
A descoberta de um novo planeta, atualmente não é uma manchete que chama tanto assim a atenção das pessoas. Muito disso, graças ao Telescópio Espacial Kepler, que já descobriu quase 2000 exoplanetas e todo instante uma nova descoberta é anunciada, certo? Mais ou menos, a descoberta anunciada hoje, dia 20 de Janeiro de 2016, é um pouco diferente, pois não se trata de um exoplaneta, e sim de um novo planeta no Sistema Solar, e esse é um fato que intriga os astrônomos a muitos e muitos anos.
Porém, temos que ir com calma com esses anúncios. No artigo aceito para publicação no The Astronomical Journal (artigo no final do post), os autores, Mike Brown e Konstantin Batygin, do Instituto de Tecnologia da Califórnia, apresentaram o que eles dizem ser evidências circunstâncias fortes para a existência de um grande planeta ainda não descoberto, talvez, com uma massa 10 vezes a massa da Terra, orbitando os confins do nosso Sistema Solar, muito além da órbita de Plutão. Os cientistas inferiram sua presença, por meio de anomalias encontradas nas órbitas de seis objetos do chamado Cinturão de Kuiper.
O objeto, que os pesquisadores estão chamando de Planeta Nove, não chega muito perto do Sol, no ponto mais próximo da sua órbita ele fica a 30.5 bilhões de quilômetros, ou seja, cinco vezes a distância entre o Sol e Plutão. Apesar do seu grande tamanho, ele é muito apagado, e por isso ninguém até o momento conseguiu observá-lo.
Não existe ainda uma confirmação observacional da descoberta, mas as evidências são tão fortes que fizeram com que outros especialistas como Chad Trujilo do Observatório Gemini no Havaí e David Nesvorny, do Southwest Research Institute em Boulder no Colorado, ficassem impressionados e bem convencidos de que deve mesmo haver um grande planeta nas fronteiras da nossa vizinhança cósmica.
The document presents observations of the starburst galaxy NGC 253 using near-infrared imaging and spectroscopy as well as mid-infrared spectroscopy. The observations are used to derive physical properties of the starburst such as the star formation rate, stellar population, and evolutionary stage. Evolutionary synthesis modeling is applied to interpret the observations and show that the starburst in NGC 253 is in a late phase, has been ongoing for 20-30 million years, and is consistent with a modified Salpeter initial mass function.
Todo mundo sabe que os raios produzidos pela Estrela da Morte em Guerra nas Estrelas não pode existir na vida real, porém no universo existem fenômenos que as vezes conseguem superar até a mais surpreendente ficção.
A galáxia Pictor A, é um desses objetos que possuem fenômenos tão espetaculares quanto aqueles exibidos no cinema. Essa galáxia localiza-se a cerca de 500 milhões de anos-luz da Terra e possui um buraco negro supermassivo no seu centro. Uma grande quantidade de energia gravitacional é lançada, à medida que o material cai em direção ao horizonte de eventos, o ponto sem volta ao redor do buraco negro. Essa energia produz um enorme jato de partículas que viajam a uma velocidade próxima da velocidade da luz no espaço intergaláctico, chamado de jato relativístico.
Para obter imagens desse jato, os cientistas usaram o Observatório de Raios-X Chandra, da NASA várias vezes durante 15 anos. Os dados do Chandra, apresentados em azul nas imagens, foram combinados com os dados obtidos em ondas de rádio a partir do Australia Telescope Compact Array, e são aparesentados em vermelho nas imagens.
Confirmation of the_ogle_planet_signature_and_its_characteristics_with_lens_s...Sérgio Sacani
O Telescópio Espacial Hubble e o Observatório W. M. Keck, no Havaí, fizeram confirmações independentes de um exoplaneta orbitando sua estrela central de uma distância bem grande. O planeta foi descoberto através de uma técnica chamada de microlente gravitacional.
Essa descoberta traz uma nova peça para o processo de caçada de exoplanetas: para descobrir planetas longe de suas estrelas, como Júpiter e Saturno estão do Sol. Os resultados obtidos pelo Hubble e pelo Keck apareceram em dois artigos da edição de 30 de Julho de 2015 do The Astrophysical Journal.
A grande maioria dos exoplanetas catalogados são aqueles localizados bem perto de suas estrelas, isso acontece porque as técnicas atuais de se caçar exoplanetas favorecem a descoberta de planetas com curtos períodos orbitais. Mas esse não é o caso da técnica de microlente gravitacional, que pode encontrar planetas mais frios e mais distantes com órbitas de longo período que outros métodos não são capazes de detectar.
High-resolution UV/Optical/IR Imaging of Jupiter in 2016–2019Sérgio Sacani
Imaging observations of Jupiter with high spatial resolution were acquired beginning in 2016, with a cadence of 53
days to coincide with atmospheric observations of the Juno spacecraft during each perijove pass. The Wide Field
Camera 3 (WFC3) aboard the Hubble Space Telescope (HST) collected Jupiter images from 236 to 925 nm in 14
filters. The Near-Infrared Imager (NIRI) at Gemini North imaged Jovian thermal emission using a lucky-imaging
approach (co-adding the sharpest frames taken from a sequence of short exposures), using the M′ filter at 4.7 μm.
We discuss the data acquisition and processing and an archive collection that contains the processed WFC3 and
NIRI data (doi:10.17909/T94T1H). Zonal winds remain steady over time at most latitudes, but significant
evolution of the wind profile near 24°N in 2016 and near 15°S in 2017 was linked with convective superstorm
eruptions. Persistent mesoscale waves were seen throughout the 2016–2019 period. We link groups of lightning
flashes observed by the Juno team with water clouds in a large convective plume near 15°S and in cyclones near
35°N–55°N. Thermal infrared maps at the 10.8 micron wavelength obtained at the Very Large Telescope show
consistent high brightness temperature anomalies, despite a diversity of aerosol properties seen in the HST data.
Both WFC3 and NIRI imaging reveal depleted aerosols consistent with downwelling around the periphery of the
15°S storm, which was also observed by the Atacama Large Millimeter/submillimeter Array. NIRI imaging of
the Great Red Spot shows that locally reduced cloud opacity is responsible for dark features within the vortex. The
HST data maps multiple concentric polar hoods of high-latitude hazes.
Toward a new_distance_to_the_active_galaxy_ngc4258Sérgio Sacani
This document reports on measurements of centripetal accelerations of maser spectral components in the active galaxy NGC 4258 using data from 51 epochs spanning 1994 to 2004. Accelerations of high-velocity maser emission indicate an origin within 13 degrees of the disk midline. Accelerations do not support a model of trailing shocks from spiral arms but find evidence of spiral structure with a wavelength of 0.75 mas. Accelerations of low-velocity emission are consistent with originating from a concave region where the thin disk is tangent to the line of sight.
A magnetar-powered X-ray transient as the aftermath of a binary neutron-star ...Sérgio Sacani
Mergers of neutron stars are known to be associated with short γ-ray
bursts1–4
. If the neutron-star equation of state is sufficiently stiff
(that is, the pressure increases sharply as the density increases), at
least some such mergers will leave behind a supramassive or even a
stable neutron star that spins rapidly with a strong magnetic field5–8
(that is, a magnetar). Such a magnetar signature may have been
observed in the form of the X-ray plateau that follows up to half
of observed short γ-ray bursts9,10. However, it has been expected
that some X-ray transients powered by binary neutron-star mergers
may not be associated with a short γ-ray burst11,12. A fast X-ray
transient (CDF-S XT1) was recently found to be associated with a
faint host galaxy, the redshift of which is unknown13. Its X-ray and
host-galaxy properties allow several possible explanations including
a short γ-ray burst seen off-axis, a low-luminosity γ-ray burst at
high redshift, or a tidal disruption event involving an intermediatemass black hole and a white dwarf13. Here we report a second X-ray
transient, CDF-S XT2, that is associated with a galaxy at redshift
z = 0.738 (ref. 14). The measured light curve is fully consistent with
the X-ray transient being powered by a millisecond magnetar. More
intriguingly, CDF-S XT2 lies in the outskirts of its star-forming host
galaxy with a moderate offset from the galaxy centre, as short γ-ray
bursts often do15,16. The estimated event-rate density of similar
X-ray transients, when corrected to the local value, is consistent
with the event-rate density of binary neutron-star mergers that is
robustly inferred from the detection of the gravitational-wave event
GW170817.
We present long-baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of
the 870 m continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that
trace millimeter-sized particles down to spatial scales as small as 1 AU (20 mas). These data reveal
a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli
(1{6AU) with modest contrasts (5{30%). We associate these features with concentrations of solids
that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima.
No signicant non-axisymmetric structures are detected. Some of the observed features occur near
temperatures that may be associated with the condensation fronts of major volatile species, but the
relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the
so-called zonal
ows). Other features, particularly a narrow dark annulus located only 1 AU from the
star, could indicate interactions between the disk and young planets. These data signal that ordered
substructures on AU scales can be common, fundamental factors in disk evolution, and that high
resolution microwave imaging can help characterize them during the epoch of planet formation.
Keywords: protoplanetary disks | planet-disk interactions | stars: individual (TW Hydrae)
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of
1011.5 K. Relativistic boosting can increase its observed value, but apparent brightness temperatures
much in excess of 1013 K are inaccessible using ground-based very long baseline interferometry (VLBI)
at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission
RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as
small as 26 µas (2.7 light months) and brightness temperature in excess of 1013 K. These measurements
challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive
black holes and require a much higher Doppler factor than what is determined from jet apparent
kinematics.
Keywords: galaxies: active — galaxies: jets — radio continuum: galaxies — techniques: interferometric
— quasars: individual (3C 273)
1) The document analyzes data from the SuperWASP-South telescope to classify four stars - VSX013997, 017283, 026353, and 091251.
2) The author cleaned the raw data, used Period04 to identify pulsation frequencies for each star, and created phased light curves to classify the stars.
3) Based on the periods, amplitudes, and light curve shapes, the author classified three stars as RRab subtype RR Lyrae variables and one star as a rotating ellipsoidal variable.
This document summarizes research on determining temperatures, luminosities, and masses of the coldest known brown dwarfs. The key findings are:
1) Precise distances were measured for a sample of late-T and Y dwarfs using Spitzer Space Telescope astrometry, allowing accurate calculation of absolute fluxes, luminosities, and temperatures.
2) Y0 dwarfs were found to have temperatures of 400-450 K, significantly warmer than previous estimates, and masses of 5-20 times Jupiter's mass.
3) While having similar temperatures, Y dwarfs showed diverse spectral energy distributions, suggesting temperature alone does not determine spectra. Physical properties like gravity, clouds and chemistry also influence spectra.
The open cluster_ngc6520_and_the_nearby_dark_molecular_cloud_barnard_86Sérgio Sacani
This document presents optical photometry and CO observations of the open cluster NGC 6520 and nearby dark molecular cloud Barnard 86. Analysis of the optical data finds the cluster radius is 1.0±0.5 arcmin, smaller than previous estimates. The cluster age is estimated to be 150±50 Myr with reddening of EB−V =0.42±0.10. The distance from the Sun is estimated to be 1900±100 pc, larger than previous estimates. CO observations are used to derive basic properties of Barnard 86 under the assumption it lies at the same distance as the cluster.
Observation of Bose–Einstein condensates in an Earth-orbiting research labSérgio Sacani
Quantum mechanics governs the microscopic world, where low mass and momentum
reveal a natural wave–particle duality. Magnifying quantum behaviour to
macroscopic scales is a major strength of the technique of cooling and trapping
atomic gases, in which low momentum is engineered through extremely low
temperatures. Advances in this feld have achieved such precise control over atomic
systems that gravity, often negligible when considering individual atoms, has
emerged as a substantial obstacle. In particular, although weaker trapping felds
would allow access to lower temperatures1,2
, gravity empties atom traps that are too
weak. Additionally, inertial sensors based on cold atoms could reach better
sensitivities if the free-fall time of the atoms after release from the trap could be made
longer3
. Planetary orbit, specifcally the condition of perpetual free-fall, ofers to lift
cold-atom studies beyond such terrestrial limitations. Here we report production of
rubidium Bose–Einstein condensates (BECs) in an Earth-orbiting research laboratory,
the Cold Atom Lab. We observe subnanokelvin BECs in weak trapping potentials with
free-expansion times extending beyond one second, providing an initial
demonstration of the advantages ofered by a microgravity environment for
cold-atom experiments and verifying the successful operation of this facility. With
routine BEC production, continuing operations will support long-term investigations
of trap topologies unique to microgravity4,5
, atom-laser sources6
, few-body physics7,8
and pathfnding techniques for atom-wave interferometry9–12
WHERE IS THE FLUX GOING? THE LONG-TERM PHOTOMETRIC VARIABILITY OF BOYAJIAN’S ...Sérgio Sacani
We present ∼ 800 days of photometric monitoring of Boyajian’s Star (KIC 8462852) from the AllSky
Automated Survey for Supernovae (ASAS-SN) and ∼ 4000 days of monitoring from the All Sky
Automated Survey (ASAS). We show that from 2015 to the present the brightness of Boyajian’s Star
has steadily decreased at a rate of 6.3 ± 1.4 mmag yr−1
, such that the star is now 1.5% fainter than it
was in February 2015. Moreover, the longer time baseline afforded by ASAS suggests that Boyajian’s
Star has also undergone two brightening episodes in the past 11 years, rather than only exhibiting a
monotonic decline. We analyze a sample of ∼ 1000 comparison stars of similar brightness located in
the same ASAS-SN field and demonstrate that the recent fading is significant at & 99.4% confidence.
The 2015 − 2017 dimming rate is consistent with that measured with Kepler data for the time period
from 2009 to 2013. This long-term variability is difficult to explain with any of the physical models
for the star’s behavior proposed to date
New results from_an_old_friend_the_crab_nebula _and_its_pulsarSérgio Sacani
1. Recent Chandra observations of the Crab Nebula system show that the southern jet has evolved over time, with changes in position, width, and spectrum as a function of distance from the pulsar.
2. Chandra images reveal that the pulsar is not centered within the inner ring, suggesting that the ring may lie on the pulsar's axis of symmetry but at a latitude of about 5 degrees.
3. Phase-resolved spectroscopy of the pulsar with Chandra shows similarities in the variation of X-ray and gamma-ray spectral indices with pulse phase, posing a challenge to theoretical models.
4. Chandra observations were used to search for an X-ray signature of the site
Imaging the dust_sublimation_front_of_a_circumbinary_diskSérgio Sacani
Aims. We present the first near-IR milli-arcsecond-scale image of a post-AGB binary that is surrounded by hot circumbinary dust.
Methods. A very rich interferometric data set in six spectral channels was acquired of IRAS 08544-4431 with the new RAPID camera
on the PIONIER beam combiner at the Very Large Telescope Interferometer (VLTI). A broadband image in the H-band was reconstructed
by combining the data of all spectral channels using the SPARCO method.
Results. We spatially separate all the building blocks of the IRAS 08544-4431 system in our milliarcsecond-resolution image. Our
dissection reveals a dust sublimation front that is strikingly similar to that expected in early-stage protoplanetary disks, as well as an
unexpected flux signal of 4% from the secondary star. The energy output from this companion indicates the presence of a compact
circum-companion accretion disk, which is likely the origin of the fast outflow detected in H.
Conclusions. Our image provides the most detailed view into the heart of a dusty circumstellar disk to date. Our results demonstrate
that binary evolution processes and circumstellar disk evolution can be studied in detail in space and over time.
The benefit of hindsight in observational science - Retrospective seismologica...Elizabeth Entwistle
This document discusses a new technique called retrospective seismology that allows seismic recordings to be obtained at times before, during, or after a seismometer was physically installed using seismic interferometry theory. As an example, the document constructs seismograms from two past earthquakes using data from a seismometer installed afterwards. This allows novel information to be obtained about both the earth structure and earthquake sources. The key is that ambient seismic noise recordings can be used to synthesize deterministic signals from earthquake sources. This counterintuitive finding provides a new way to retrospectively observe seismic events.
High precision abundances_of_the_old_solar_twin_insights_on_li_depletion_from...Sérgio Sacani
- The document presents the results of a chemical abundance analysis of the old solar twin star HIP 102152 (8.2 Gyr) and the younger solar twin 18 Sco (2.9 Gyr) using high-resolution UVES spectra.
- Abundances of 21 elements were derived for HIP 102152 with precisions up to 0.004 dex relative to the Sun. The metallicity of HIP 102152 was found to be nearly solar at [Fe/H] = -0.013.
- Elemental abundances as a function of condensation temperature reveal a solar abundance pattern for HIP 102152, unlike most solar twins. Its pattern most closely matches the Sun. The Li abundance
Dissecting x ray_emitting_gas_around_the_center_of_our_galaxySérgio Sacani
1) The Chandra X-ray Observatory was used to observe the supermassive black hole at the center of the Milky Way, Sgr A*, for a total of 3 megaseconds.
2) The observations revealed extended X-ray emission around Sgr A* that aligns spatially with a surrounding disk of massive stars.
3) Spectral analysis ruled out low-mass stars as the origin of the X-ray emission and instead found evidence that the emission is from a radiatively inefficient accretion flow onto the black hole, with an outflow present.
1) The Tunable Laser Spectrometer on the Curiosity rover measured methane in the Martian atmosphere on six occasions and found no detection of methane, with an upper limit of 1.3 parts per billion.
2) This contradicts previous orbital and ground-based observations over the last decade that reported detectable methane plumes containing tens of parts per billion of methane.
3) The low measured methane level is not consistent with calculations of methane dispersal from previous large plume detections and suggests methane is being destroyed more rapidly than can be explained by current models.
The document is a scientific paper published in 1972 that consists of the same citation repeated multiple times without any other substantive information. In 3 sentences or less, it is difficult to summarize the content and purpose of the document since it only contains a repeated citation without any other details.
Human and natural_influences_on_the_changing_thermal_structure_of_the_atmosphereSérgio Sacani
This document analyzes human and natural influences on changing atmospheric temperature patterns based on climate model simulations and satellite observations. The key findings are:
1) Both climate model simulations including human factors and satellite data show widespread tropospheric warming and stratospheric cooling over the past several decades.
2) These temperature changes are unlikely to be due to internal variability or natural external factors alone, based on comparisons to model runs with only natural forcings.
3) The observed temperature pattern matches that expected from increased greenhouse gases more closely than patterns from alternative forcings, providing evidence of a human influence on atmospheric temperatures.
Modelling element abundances_in_semi_analytic_models_of_galaxy_formationSérgio Sacani
This document summarizes a new implementation of detailed chemical enrichment modeling in the Munich semi-analytic model of galaxy formation (L-Galaxies). The new implementation tracks the delayed enrichment of 11 heavy elements from stellar winds, supernovae type II, and supernovae type Ia. It considers different supernovae type II yield sets and three supernovae type Ia delay-time distributions. The results are compared to observational data on local star-forming galaxies, Milky Way disc G dwarfs, and local elliptical galaxies. Overall, the best model matches require a power-law supernovae type Ia delay-time distribution, supernovae type II yields accounting for prior mass loss, and some direct ejection
The x-ray diffraction analysis of soil samples from Rocknest at Gale Crater on Mars revealed:
1) Crystalline components including plagioclase, olivine, augite, pigeonite, and minor amounts of other phases.
2) 27±14% of the soil was amorphous material, likely containing multiple iron-bearing and volatile phases including possibly hisingerite.
3) The crystalline components are similar to martian basalts and meteorites, while the amorphous component is similar to soils on Earth like those on Mauna Kea, Hawaii.
The ChemCam instrument on the Curiosity rover identified two main soil types on Mars - a fine-grained mafic soil and a coarse-grained felsic soil locally derived. The mafic soil is similar to widespread martian soils and dust, and possesses a ubiquitous hydrogen signature from hydrated amorphous phases. This hydration may account for a significant fraction of hydrogen detected globally on Mars. ChemCam analyses did not reveal water vapor exchange between the soil and atmosphere. The observations provide constraints on the nature and hydration of amorphous phases in the soil.
A rigid and_weathered_ice_shell_on_titanSérgio Sacani
- Saturn's moon Titan likely has a global subsurface ocean beneath an ice shell 50-200 km thick.
- Analysis of gravity and topography data at long wavelengths shows a strong inverse correlation, indicating a rigid ice shell at least 40 km thick.
- A rigid shell is required to support hundreds of meters of surface erosion/deposition as observed, ruling out an actively convecting shell.
- The results suggest Titan's ice shell has undergone substantial erosion over geological timescales, with implications for its internal structure and composition.
Its official voyager_has_left_the_solar_systemSérgio Sacani
1) After 36 years of traveling away from Earth, the Voyager 1 spacecraft may have finally crossed into interstellar space based on new data.
2) In August 2012, Voyager 1 detected a sharp drop in cosmic rays from inside the heliosphere and an increase in cosmic rays from outside, but the magnetic field did not change direction as expected. This led to debate over whether it had truly crossed the boundary.
3) In April 2013, Voyager detected plasma oscillations at a frequency implying a plasma density 80 times higher than inside the heliosphere, suggesting it had crossed into interstellar space in August 2012. While some researchers still disagree, this is now the consensus of the Voyager team.
Inference of homogeneous_clouds_in_an_exoplanet_atmosphereSérgio Sacani
1) New visible and infrared observations of the exoplanet Kepler-7b were analyzed to determine its atmospheric properties and detect the presence of clouds.
2) The observations found a westward shift in Kepler-7b's optical phase curve and placed upper limits on its thermal emission that remained undetected in Spitzer bandpasses.
3) The data suggests Kepler-7b has optically thick, high-altitude clouds located west of the substellar point, composed possibly of silicates. The clouds help explain Kepler-7b's unusually high geometric albedo and visible flux that cannot be attributed to thermal emission or molecular hydrogen scattering alone.
Swiging between rotation_and_accretion_power_in_a_millisecond_binary_pulsarSérgio Sacani
This document discusses the discovery of a millisecond X-ray pulsar, IGR J18245-2452, located in the globular cluster M28. The pulsar was previously known as the radio millisecond pulsar PSR J1824-2452I. Observations found that the pulsar alternates between accretion-powered and rotation-powered states on timescales of years, providing direct evidence that these two states cycle in recycled pulsars. When accreting, the pulsar shows X-ray pulsations and luminosity characteristic of other accreting millisecond pulsars. When not accreting, it had previously been detected as a radio pulsar. This demonstrates the evolutionary link between low-mass X
Mapping the three_dimensional_density_of_the_galactic_bulge_with_vvv_red_clum...Sérgio Sacani
This document summarizes a study that mapped the three-dimensional density distribution of the Galactic bulge using red clump giant stars identified in the VISTA Variables in the Via Lactea (VVV) survey. The authors constructed extinction maps and used the red clump stars to estimate line-of-sight density distributions by deconvolving the intrinsic luminosity function. Assuming an 8-fold mirror symmetry, they used the line-of-sight densities to construct a 3D density map covering the inner (2.2 × 1.4 × 1.1)kpc of the bulge/bar. The resulting density distribution shows a highly elongated bar with an exponential fall off and axis ratios characteristic of a strongly boxy/pe
In situ observations_of_interstellar_plasma_with_voyager_1Sérgio Sacani
Voyager 1 detected electron plasma oscillations beginning in April 2013 at a frequency corresponding to an electron density of 0.08 cm-3. This provides evidence that Voyager 1 has crossed into the nearby interstellar plasma, as the density is much higher than what is expected in the heliosheath. Comparison with radio emissions detected in 1992 suggests Voyager 1 has encountered a smoothly increasing plasma density ramp, as the frequency drift matches what was observed remotely. Estimating the shock propagation speed that would be required to produce the 1992 drift indicates a plausible speed of 40 km/s.
Curiosity at gale_crater_characterization_and_analysis_of_the_rocknest_sand_s...Sérgio Sacani
The Rocknest sand shadow analyzed by the Curiosity rover on Mars was similar to coarse-grained ripples analyzed by previous rovers. It consisted of an upper layer of very coarse sand grains armoring the surface, underlain by finer grains. Analysis found the sand was around 55% crystalline material of basaltic composition and 45% amorphous iron-rich glass. This amorphous component contained the volatiles detected and was similar to soils analyzed at other Mars sites, implying the materials were locally derived from similar basaltic sources globally on Mars.
The Curiosity rover analyzed samples of Martian fines from the Rocknest site using its Sample Analysis at Mars (SAM) instrument suite. SAM detected water, sulfur dioxide, carbon dioxide, and oxygen as the major gases released when heating the fines. The water content and release temperature suggest the water is bound in amorphous materials. Much of the carbon dioxide was likely released from the decomposition of fine-grained iron or magnesium carbonates. Elevated levels of deuterium indicate recent interaction with the atmosphere. Several simple organic compounds were detected but are not definitively of Martian origin.
The petrochemistry of_jake_m_a_martian_mugeariteSérgio Sacani
The rock "Jake_M" was the first rock analyzed by Curiosity on Mars. It has a distinct chemical composition compared to other known Martian rocks. Jake_M has a basaltic composition but is alkaline, with over 15% normative nepheline content. Its chemical makeup is similar to terrestrial mugearites, fractionated alkaline rocks found at ocean islands and rifts. This suggests Jake_M formed through extensive fractional crystallization of an alkaline magma at elevated pressure, possibly with water. The discovery of an alkaline rock expands the diversity of known Martian igneous compositions.
Studies of ngc_6720_with_calibrated_hst_wfc3_emission_line_filter_imagesSérgio Sacani
This study uses calibrated Hubble Space Telescope images of the Ring Nebula (NGC 6720) taken 12.925 years apart to measure tangential motions within the nebula. Individual features were measured in nitrogen emission line images as well as dark knots seen against oxygen emission. The results indicate that the nebula is expanding homologously, but at a faster rate along its major axis. Dark knots were found to expand more slowly than the nebular gas. The tangential motion measurements allow estimates of the nebula's distance and dynamic age to be about 720 pc and 4000 years, respectively.
Extended x ray emission in the h i cavity of ngc 4151- galaxy-scale active ga...Sérgio Sacani
The document summarizes the discovery of diffuse soft X-ray emission extending about 2 kpc from the active nucleus of NGC 4151, filling the cavity of H i material. The X-ray emission has a luminosity of about 1039 erg s-1 and can be fit with either a thermal plasma model with a temperature of around 0.25 keV, or a photoionized model. This interaction between the AGN and interstellar medium implies the last episode of high nuclear activity occurred relatively recently, around 104 years ago.
Solving the Multimessenger Puzzle of the AGN-starburst Composite Galaxy NGC 1068Sérgio Sacani
Multiwavelength observations indicate that some starburst galaxies show a dominant nonthermal contribution from
their central region. These active galactic nuclei (AGN)-starburst composites are of special interest, as both
phenomena on their own are potential sources of highly energetic cosmic rays and associated γ-ray and neutrino
emission. In this work, a homogeneous, steady-state two-zone multimessenger model of the nonthermal emission
from the AGN corona as well as the circumnuclear starburst region is developed and subsequently applied to the
case of NGC 1068, which has recently shown some first indications of high-energy neutrino emission. Here, we
show that the entire spectrum of multimessenger data—from radio to γ-rays including the neutrino constraint—can
be described very well if both, starburst and AGN corona, are taken into account. Using only a single emission
region is not sufficient.
The origin and_motion_of_pulsar_in_simeis_147Sérgio Sacani
This document summarizes a study measuring the parallax and proper motion of the pulsar PSR J0538+2817 located within the supernova remnant S147 using VLBA radio astrometry over multiple epochs. They determine a distance of 1.47+0.42 kpc and a high transverse velocity of 400+114 km/s for the pulsar. A small extended X-ray nebula is also detected around the pulsar. The proper motion direction suggests the pulsar was born near the geometric center of the remnant and has since moved away, with an inferred kinematic age of around 40,000 years.
X-rays from a Central “Exhaust Vent” of the Galactic Center ChimneySérgio Sacani
Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of
linear X-ray-emitting features located within the southern portion of the Galactic center chimney,
and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.08◦
, b = −1.42◦
. The
surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology which may
have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the
feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma
components, possibly a sign of shock compression or heating of the interstellar medium by outflowing
material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this
plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a
sequence of accretion events onto the Galactic Black Hole may be a plausible quasi-continuous energy
source to sustain the observed morphology
Chiotelis Ioannis, Theodoropoulou Maria, “Searching for Black Holes. Photometry in our Classrooms”, Hellenic Conference on Innovating STEM Education, 16-18 December 2016, Athens, Greece.
This document summarizes the results of a deep near-infrared survey of the Carina Nebula complex using the HAWK-I instrument on the VLT. The survey imaged an area of 0.36 square degrees down to magnitudes of J=23, H=22, and Ks=21, detecting over 600,000 infrared sources. Color-magnitude diagrams of the sources were analyzed to determine properties of the low-mass stellar population such as ages and masses. The survey found that about 3200 sources have masses above 1 solar mass, consistent with expectations from the initial mass function. It also found that about half of the young stars in Carina are in a widely distributed, non-clustered configuration. Six
Measurement of Jupiter’s asymmetric gravity fieldSérgio Sacani
The gravity harmonics of a fluid, rotating planet can be decomposed
into static components arising from solid-body rotation and dynamic
components arising from flows. In the absence of internal dynamics,
the gravity field is axially and hemispherically symmetric and is
dominated by even zonal gravity harmonics J2n that are approximately
proportional to qn, where q is the ratio between centrifugal
acceleration and gravity at the planet’s equator1
. Any asymmetry in the
gravity field is attributed to differential rotation and deep atmospheric
flows. The odd harmonics, J3, J5, J7, J9 and higher, are a measure of the
depth of the winds in the different zones of the atmosphere2,3
. Here
we report measurements of Jupiter’s gravity harmonics (both even
and odd) through precise Doppler tracking of the Juno spacecraft
in its polar orbit around Jupiter. We find a north–south asymmetry,
which is a signature of atmospheric and interior flows. Analysis of
the harmonics, described in two accompanying papers4,5
, provides
the vertical profile of the winds and precise constraints for the depth
of Jupiter’s dynamical atmosphere.
The internal structure_of_asteroid_itokawa_as_revealed_by_detection_of_yorp_s...Sérgio Sacani
The study detected an acceleration in the rotation rate of asteroid (25143) Itokawa through long-term photometric monitoring between 2001-2013. By measuring rotational phase offsets between observed and modeled lightcurves, a YORP acceleration of 3.54 ± 0.38 × 10−8 rad day−2 was measured, equivalent to a decrease in the asteroid's rotation period of about 45 ms per year. Thermophysical analysis of the detailed shape model from the Hayabusa spacecraft found that the center-of-mass must be offset by about 21 m along the long axis to reconcile the observed and theoretical YORP strengths, suggesting Itokawa is composed of two separate bodies with densities of 1750 ± 110 kg m
Visible spectra of (474640) 2004 VN112–2013 RF98 with OSIRIS at the 10.4 m GT...Sérgio Sacani
The existence of significant anisotropies in the distributions of the directions of perihelia and
orbital poles of the known extreme trans-Neptunian objects (ETNOs) has been used to claim
that trans-Plutonian planets may exist. Among the known ETNOs, the pair (474640) 2004
VN112–2013 RF98 stands out. Their orbital poles and the directions of their perihelia and their
velocities at perihelion/aphelion are separated by a few degrees, but orbital similarity does
not necessarily imply common physical origin. In an attempt to unravel their physical nature,
visible spectroscopy of both targets was obtained using the OSIRIS camera-spectrograph at the
10.4 m Gran Telescopio Canarias (GTC). From the spectral analysis, we find that 474640–2013
RF98 have similar spectral slopes (12 versus 15 per cent/0.1 µm), very different from Sedna’s
but compatible with those of (148209) 2000 CR105 and 2012 VP113. These five ETNOs belong
to the group of seven linked to the Planet Nine hypothesis. A dynamical pathway consistent
with these findings is dissociation of a binary asteroid during a close encounter with a planet
and we confirm its plausibility using N-body simulations. We thus conclude that both the
dynamical and spectroscopic properties of 474640–2013 RF98 favour a genetic link and their
current orbits suggest that the pair was kicked by a perturber near aphelion
The canarias einstein_ring_a_newly_discovered_optical_einstein_ringSérgio Sacani
This document reports the discovery of a newly discovered optical Einstein ring (ER) called the "Canarias Einstein Ring". It was discovered serendipitously in imaging data from the Dark Energy Camera. Follow-up spectroscopy with the Gran Telescopio CANARIAS confirmed the nature of the system, with the lens being an early-type galaxy at a redshift of z=0.581 and the source being a starburst galaxy at z=1.165. Analysis of the system determined the Einstein radius to be 2.16 arcseconds and the total enclosed mass producing the lensing effect to be 1.86 ± 0.23 × 1012 solar masses.
The atacama cosmology_telescope_measuring_radio_galaxy_bias_through_cross_cor...Sérgio Sacani
A radiação cósmica de micro-ondas aponta para a matéria escura invisível, marcando o ponto onde jatos de material viajam a velocidades próximas da velocidade da luz, de acordo com uma equipe internacional de astrônomos. O principal autor do estudo, Rupert Allison da Universidade de Oxford apresentou os resultados no dia 6 de Julho de 2015 no National Astronomy Meeting em Venue Cymru, em Llandudno em Wales.
Atualmente, ninguém sabe ao certo do que a matéria escura é feita, mas ela é responsável por cerca de 26% do conteúdo de energia do universo, com galáxias massivas se formando em densas regiões de matéria escura. Embora invisível, a matéria escura se mostra através do efeito gravitacional – uma grande bolha de matéria escura puxa a matéria normal (como elétrons, prótons e nêutrons) através de sua própria gravidade, eventualmente se empacotando conjuntamente para criar as estrelas e galáxias inteiras.
Muitas das maiores dessas são galáxias ativas com buracos negros supermassivos em seus centros. Alguma parte do gás caindo diretamente na direção do buraco negro é ejetada como jatos de partículas e radiação. As observações feitas com rádio telescópios mostram que esses jatos as vezes se espalham por milhões de anos-luz desde a galáxia – mais distante até mesmo do que a extensão da própria galáxia.
Os cientistas esperam que os jatos possam viver em regiões onde existe um excesso de concentração da matéria escura, maior do que o da média. Mas como a matéria escura é invisível, testar essa ideia não é algo tão direto.
A young protoplanet_candidate_embedded_in_the_circumstellar_disk_of_hd100546Sérgio Sacani
This document summarizes observations of HD100546 using high-contrast imaging techniques. A faint emission source was detected near the star at a projected separation of about 47 AU. The position of the source coincides with a deficit in polarization observed from the circumstellar disk. This suggests a physical link between the source and the disk. Considering various scenarios, the authors favor interpreting the source as a young protoplanet currently forming within the disk. Follow-up observations could distinguish between different possible explanations for the observed features. If confirmed, it would be a unique opportunity to study giant planet formation within an optically thick disk.
Is Betelgeuse Really Rotating? Synthetic ALMA Observations of Large-scale Con...Sérgio Sacani
The evolved stages of massive stars are poorly understood, but invaluable constraints can be derived from spatially resolved observations of nearby red supergiants, such as Betelgeuse. Atacama Large Millimeter/submillimeter Array (ALMA) observations of Betelgeuse showing a dipolar velocity field have been interpreted as evidence for a projected rotation rate of about 5 km s−1. This is 2 orders of magnitude larger than predicted by single-star evolution, which led to suggestions that Betelgeuse is a binary merger. We propose instead that large-scale convective motions can mimic rotation, especially if they are only partially resolved. We support this claim with 3D CO5BOLDsimulations of nonrotating red supergiants that we postprocessed to predict ALMA images and SiO spectra. We show that our synthetic radial velocity maps have a 90% chance of being falsely interpreted as evidence for a projected rotation rate of 2 km s−1 or larger for our fiducial simulation. We conclude that we need at least another ALMA observation to firmly establish whether Betelgeuse is indeed rapidly rotating. Such observations would also provide insight into the role of angular momentum and binary interaction in the late evolutionary stages. The data will further probe the structure and complex physical processes in the atmospheres of red supergiants, which are immediate progenitors of supernovae and are believed to be essential in the formation of gravitational-wave sources.
Know the star_know_the_planet_discovery_of_l_ate_type_companions_to_two_exopl...Sérgio Sacani
This document summarizes the discovery of additional late-type stellar companions to two exoplanet host stars, HD 2638 and 30 Ari B, using adaptive optics imaging. For both systems, the companions were found to share common proper motion with the primaries, indicating they are physically associated. The estimated orbital periods of the new companions are 130 years for HD 2638 and 80 years for 30 Ari B. This makes 30 Ari B the second confirmed quadruple star system known to host an exoplanet. The discoveries provide additional examples of how binary companions can influence exoplanet dynamics and formation.
This document summarizes a study that uses U-band photometry to determine photometric distances to young stars in the inner Galactic disk. The study focuses on the line of sight towards the Galactic longitude of 314 degrees. Photometric data is collected and calibrated using two open clusters in the field. Three groups of stars are detected at distances of 1.5, 2.5, and 5.1 kpc, which are consistent with the Carina-Sagittarius and Scutum-Crux spiral arms. The use of U-band photometry is shown to be an effective method for characterizing young star populations and making predictions about spiral structure in the Milky Way.
Eccentricity from transit_photometry_small_planets_in_kepler_multi_planet_sys...Sérgio Sacani
Artigo descreve estudo que mostra que a órbita dos exoplanetas terrestres são na sua maioria órbitas circulares, o que é bom para se procurar por vida e o que vem causando uma revolução no entendimento sobre os sistemas de exoplanteas.
This summarizes a scientific study on long-distance quantum teleportation between two laboratories separated by 55 meters but connected by 2 kilometers of fiber optic cable. The key points are:
1) Researchers teleported quantum states (qubits) carried by photons at 1.3 micrometer wavelengths onto photons at 1.55 micrometer wavelengths between the two laboratories.
2) The qubits were encoded in time-bin superpositions and entanglement rather than polarization to make them more robust against decoherence in optical fibers.
3) A partial Bell state measurement was performed using linear optics at the receiving end to probabilistically teleport the quantum states over the long distance.
1. This document describes a multiwavelength campaign on the Seyfert 1 galaxy Mrk 509 using five satellites and two ground-based facilities.
2. The campaign aims to study several open questions about active galactic nuclei (AGN), including the location and physics of outflows from AGN, the nature of continuum emission, the geometry and physical state of the X-ray broad emission line region, and the Fe-K line complex.
3. The observations cover more than five decades in frequency, from 2 μm to 200 keV, and include a simultaneous set of deep XMM-Newton and INTEGRAL observations over seven weeks. This allows the authors to disentangle different components and study time variability
Similar to Alignment of th_angular_momentum_vectors_of_planetary_nebulae_in_the_galactic_bulge (20)
Compositions of iron-meteorite parent bodies constrainthe structure of the pr...Sérgio Sacani
Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System,and they preserve information about conditions and planet-forming processes in thesolar nebula. In this study, we include comprehensive elemental compositions andfractional-crystallization modeling for iron meteorites from the cores of five differenti-ated asteroids from the inner Solar System. Together with previous results of metalliccores from the outer Solar System, we conclude that asteroidal cores from the outerSolar System have smaller sizes, elevated siderophile-element abundances, and simplercrystallization processes than those from the inner Solar System. These differences arerelated to the formation locations of the parent asteroids because the solar protoplane-tary disk varied in redox conditions, elemental distributions, and dynamics at differentheliocentric distances. Using highly siderophile-element data from iron meteorites, wereconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across theprotoplanetary disk within the first million years of Solar-System history. CAIs, the firstsolids to condense in the Solar System, formed close to the Sun. They were, however,concentrated within the outer disk and depleted within the inner disk. Future modelsof the structure and evolution of the protoplanetary disk should account for this dis-tribution pattern of CAIs.
Signatures of wave erosion in Titan’s coastsSérgio Sacani
The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it isunclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theo-retical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion,but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titanremain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively dis-cern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combinelandscape evolution models with measurements of shoreline shape on Earth to characterize how differentcoastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that theshorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded bywaves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates atfetch lengths of tens of kilometers.
SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole⋆Sérgio Sacani
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
�
)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
�
Ca-rich population. Although such an object is too red for any low-
�
cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
�
) with
Λ
CDM. Therefore unlike low-
�
Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
�
truly diverge from their low-
�
counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...Sérgio Sacani
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...Sérgio Sacani
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDSSérgio Sacani
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
Anti-Universe And Emergent Gravity and the Dark UniverseSérgio Sacani
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional ‘dark’ gravitational force describing the ‘elastic’ response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton’s constant and the Hubble acceleration scale a0 = cH0, and provide evidence for the fact that this additional ‘dark gravity force’ explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
[OReilly Superstream] Occupy the Space: A grassroots guide to engineering (an...Jason Yip
The typical problem in product engineering is not bad strategy, so much as “no strategy”. This leads to confusion, lack of motivation, and incoherent action. The next time you look for a strategy and find an empty space, instead of waiting for it to be filled, I will show you how to fill it in yourself. If you’re wrong, it forces a correction. If you’re right, it helps create focus. I’ll share how I’ve approached this in the past, both what works and lessons for what didn’t work so well.
The Microsoft 365 Migration Tutorial For Beginner.pptxoperationspcvita
This presentation will help you understand the power of Microsoft 365. However, we have mentioned every productivity app included in Office 365. Additionally, we have suggested the migration situation related to Office 365 and how we can help you.
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Conversational agents, or chatbots, are increasingly used to access all sorts of services using natural language. While open-domain chatbots - like ChatGPT - can converse on any topic, task-oriented chatbots - the focus of this paper - are designed for specific tasks, like booking a flight, obtaining customer support, or setting an appointment. Like any other software, task-oriented chatbots need to be properly tested, usually by defining and executing test scenarios (i.e., sequences of user-chatbot interactions). However, there is currently a lack of methods to quantify the completeness and strength of such test scenarios, which can lead to low-quality tests, and hence to buggy chatbots.
To fill this gap, we propose adapting mutation testing (MuT) for task-oriented chatbots. To this end, we introduce a set of mutation operators that emulate faults in chatbot designs, an architecture that enables MuT on chatbots built using heterogeneous technologies, and a practical realisation as an Eclipse plugin. Moreover, we evaluate the applicability, effectiveness and efficiency of our approach on open-source chatbots, with promising results.
Main news related to the CCS TSI 2023 (2023/1695)Jakub Marek
An English 🇬🇧 translation of a presentation to the speech I gave about the main changes brought by CCS TSI 2023 at the biggest Czech conference on Communications and signalling systems on Railways, which was held in Clarion Hotel Olomouc from 7th to 9th November 2023 (konferenceszt.cz). Attended by around 500 participants and 200 on-line followers.
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The videorecording (in Czech) from the presentation is available here: https://youtu.be/WzjJWm4IyPk?si=SImb06tuXGb30BEH .
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Chris Jones, Director of Product Management at BrainChip , presents the “Temporal Event Neural Networks: A More Efficient Alternative to the Transformer” tutorial at the May 2024 Embedded Vision Summit.
The expansion of AI services necessitates enhanced computational capabilities on edge devices. Temporal Event Neural Networks (TENNs), developed by BrainChip, represent a novel and highly efficient state-space network. TENNs demonstrate exceptional proficiency in handling multi-dimensional streaming data, facilitating advancements in object detection, action recognition, speech enhancement and language model/sequence generation. Through the utilization of polynomial-based continuous convolutions, TENNs streamline models, expedite training processes and significantly diminish memory requirements, achieving notable reductions of up to 50x in parameters and 5,000x in energy consumption compared to prevailing methodologies like transformers.
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What is an RPA CoE? Session 1 – CoE VisionDianaGray10
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HCL Notes and Domino License Cost Reduction in the World of DLAUpanagenda
Webinar Recording: https://www.panagenda.com/webinars/hcl-notes-and-domino-license-cost-reduction-in-the-world-of-dlau/
The introduction of DLAU and the CCB & CCX licensing model caused quite a stir in the HCL community. As a Notes and Domino customer, you may have faced challenges with unexpected user counts and license costs. You probably have questions on how this new licensing approach works and how to benefit from it. Most importantly, you likely have budget constraints and want to save money where possible. Don’t worry, we can help with all of this!
We’ll show you how to fix common misconfigurations that cause higher-than-expected user counts, and how to identify accounts which you can deactivate to save money. There are also frequent patterns that can cause unnecessary cost, like using a person document instead of a mail-in for shared mailboxes. We’ll provide examples and solutions for those as well. And naturally we’ll explain the new licensing model.
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Alignment of th_angular_momentum_vectors_of_planetary_nebulae_in_the_galactic_bulge
1. arXiv:1307.5711v1[astro-ph.SR]22Jul2013 Mon. Not. R. Astron. Soc. 000, 000–000 (0000) Printed 23 July 2013 (MN LATEX style file v2.2)
Alignment of the Angular Momentum Vectors of Planetary
Nebulae in the Galactic Bulge
B. Rees and A. A. Zijlstra
Jodrell Bank Centre for Astrophysics, The Alan Turing Building, School of Physics and Astronomy,
The University of Manchester, Oxford Road, Manchester M13 9PL, UK
23 July 2013
ABSTRACT
We use high-resolution H α images of 130 planetary nebulae (PNe) to investigate
whether there is a preferred orientation for PNe within the Galactic Bulge. The orien-
tations of the full sample have an uniform distribution. However, at a significance level
of 0.01, there is evidence for a non-uniform distribution for those planetary nebulae
with evident bipolar morphology. If we assume that the bipolar PNe have an unimodal
distribution of the polar axis in Galactic coordinates, the mean Galactic position angle
is consistent with 90◦
, i.e. along the Galactic plane, and the significance level is better
than 0.001 (the equivalent of a 3.7σ significance level for a Gaussian distribution).
The shapes of PNe are related to angular momentum of the original star or stellar
system, where the long axis of the nebula measures the angular momentum vector.
In old, low-mass stars, the angular momentum is largely in binary orbital motion.
Consequently, the alignment of bipolar nebulae that we have found indicates that the
orbital planes of the binary systems are oriented perpendicular to the Galactic plane.
We propose that strong magnetic fields aligned along the Galactic plane acted during
the original star formation process to slow the contraction of the star forming cloud in
the direction perpendicular to the plane. This would have produced a propensity for
wider binaries with higher angular momentum with orbital axes parallel to the Galactic
plane. Our findings provide the first indication of a strong, organized magnetic field
along the Galactic plane that impacted on the angular momentum vectors of the
resulting stellar population.
Key words: planetary nebulae: general - Galaxy: bulge - Galaxy: centre - binaries:
general - galaxies: magnetic fields.
1 INTRODUCTION
Planetary nebulae (PNe) are the ionized ejecta from evolved
stars. They form when a low to intermediate-mass star, as-
cending the Asymptotic Giant Branch, ejects its envelope
in a phase of pulsational instability. The remaining stellar
core evolves to high temperatures and ionizes the expand-
ing ejecta, before its nuclear burning ceases and the star
becomes a white dwarf (Herwig 2005; van Winckel 2003).
PNe show a variety of morphologies; they range
from round to strongly elliptical, together with bipolar
and (infrequently) irregular shapes (Corradi & Schwarz
1995; Balick & Frank 2002; Parker et al. 2006). The
origin of those morphologies is disputed. The main
contenders are binarity and magnetic fields (de Marco
2009; Blackman 2009). Magnetic fields have been
detected in PNe (Sabin, Zijlstra & Greaves 2007;
Vlemmings & van Langevelde 2008; G´omez et al. 2009) but
may not be strong enough to affect the outflows. Soker
(2006) has argued that magnetic fields also require binary
companions for their origin. If so, ultimately, in either case,
the morphology is related to angular momentum in the
stellar system and the major axis of the nebula traces the
direction of the angular momentum vector.
Weidmann & D´ıaz (2008) have reported that PNe in
the direction of the Galactic centre may have a preferential
orientation, in terms of an excess population at one partic-
ular orientation. An alignment between adjacent but unre-
lated PNe is unexpected. However, if the orientation of a
PN traces the angular momentum vector of the progenitor
system, such an effect could originate from the formation
of the stellar population. But the orientations could also be
influenced by some external factor, for instance the Galactic
magnetic field. This has been argued to be important for
supernova remnants (Gaensler 1998).
Studies of the orientation of PNe have been car-
ried out for over thirty years with conflicting results
(Schwarz, Monteiro & Peterson 2008). There has been no
convincing evidence for an alignment among nearby Galac-
tic PNe, although there have been some claims for
a preferential alignment of the polar axis with the
Galactic plane (Melnick & Harwit 1975). The evidence of
Weidmann & D´ıaz (2008) is based on a sample of 440 PNe
that were either bipolar, or elliptical with a major to minor
axis ratio greater than 1.2 : 1 of which 262 were in the direc-
c 0000 RAS
2. 2 B. Rees
tion of the Galactic centre. Within that group they found an
excess of PNe with galactic position angle (GPA) ∼ 100◦
.
In this paper we use a morphological survey of 130 PNe
likely to be in the Galactic Bulge to test this claim. As only
19 objects are in common with Weidmann & D´ıaz (2008),
this provides an independent test of the potential alignment.
The whole of the area containing our sample of PNe lies
within one of the four regions (the Galactic Centre) stud-
ied by Weidmann & D´ıaz (2008). A number of our objects
would not be classified as elongated by those authors and
the higher angular resolution of our sample enables us to
use objects with a smaller angular size than is permitted in
their sample.
2 THE OBSERVATIONS
The initial sample of PNe images consisted of 161 objects
observed in 2003 using the EMMI instrument of the Euro-
pean Southern Observatory (ESO) 3.5 m New Technology
Telescope (NTT) and 37 objects observed in 2002 and 2003
using the Planetary Camera of the WFPC2 of the HST (pro-
grammes 71.D-0448(A) and 9356 respectively). After remov-
ing foreground objects as described below, the final Bulge
sample used in this paper contained 96 NTT objects and 34
HST objects.
The HST targets were selected as a random subset of
compact PNe in the direction of the Bulge. We selected all
PNe listed in the Strasbourg-ESO catalog of Galactic plan-
etary nebulae (Acker et al. 1992), with a listed diameter of
4 arcsec or less, or no known diameter. Every second object
from this list was selected for an HST SNAPshot program.
Of the 60 objects selected, just over half were observed.
The observations utilized the F656N filter (2.2 nm wide at
656.4 nm)1
. The exposure times were about 120 seconds.
The images have a pixel size of 0.046 arcsec.
The NTT sample was selected from the larger neb-
ulae in and towards the Galactic Bulge. The NTT ob-
servations utilized the #654 H α filter (3.3 nm wide at
655.4 nm). The images have a pixel size of 0.33 arcsec
(Gonzalez, Brilliant & Pompei 2006). The seeing was typ-
ically better than 1.5 arcsec and the exposure times were
mostly 60 s but a few were of 30, 120, 180, 240 and 300
seconds.
In the region studied, 80 per cent of the selected objects
are expected to belong to the Galactic Bulge (Zijlstra 1990)
leaving few foreground nebulae in the sample. However, we
removed PNe from the sample if they were likely foreground
(or background) objects, not related to the Bulge, on the
basis of the following criteria:
1 The PN lies beyond 10◦
of the Galactic centre in terms
of Galactic longitude and latitude.
2 The PN has a measured component of length of more
than 35 arcsec; see Acker, Peyaud & Parker (2006).
3 Where a radio flux at 5 GHz was available for the PN,
for that flux to lie outside the interval (4.2 mJy, 59.1 mJy)
(Si´odmiak & Tylenda 2001; Acker et al. 1992).
It should be noted that PNe remained in the sample unless
there was data that could be used to exclude them. Where
1 WFPC2 Filter Wavelengths in the HST Archive, Koeke-
moer, A and Brammer, G; Space Telescope Science Institute;
http://www.stsci.edu/hst/wfpc2/documents/wfpc2 filters archive.html;
accessed 07/05/10
two catalogues gave conflicting radio fluxes the PN was re-
tained in the sample if one of those sets of data permitted
it.
The NTT images were deconvolved using the
LUCY/WAVE algorithm in the ESO/MIDAS package before de-
termining the PNe morphologies and orientations. The HST
images did not require deconvolution.
We define three morphological categories: bipolar, po-
lar, and non-polar. We had no irregular PNe for which we
could fix an orientation. PNe with one or more lobes, or
the remnants of lobes, generally at the 1 per cent intensity
level were classified as having a bipolar morphology. The
bipolar class conforms in the main to that usually used, see
Corradi & Schwarz (1995). We also followed those authors in
not using a separate round class and classifying what might
be considered as round PNe as elliptical. Due to the high
resolution of the images we were able to split the elliptical
category into two distinct classes. A PN was categorized as
having a polar morphology if its image showed no lobes but
the intensity distribution above 10 per cent of the peak flux
level showed internal structure thus assisting in the identifi-
cation of the polar axis. The remaining PNe were classified
as non-polar. Fig. 1 shows examples from each of the classes.
The PN orientation was taken to be that of the polar
or major axis of the PN as measured from North to East
in the image, and converted to Galactic coordinates. The
angle was estimated by eye over the range [0◦
, 180◦
) with
the assistance of the ruler tool in the NASA HEASARC fv
system. The polar angle of a bipolar PN was determined
by the alignment of the lower intensity interior of its cen-
tral shell and the direction of its lobes. The polar angle of
a non-polar PN was taken to be that of the major axis at
the 10% level, basically the main symmetry axis of the neb-
ula as suggested in Corradi, Aznar & Mampaso (1998) and
Weidmann & D´ıaz (2008). For the polar PN, the direction
of a central cavity and/or low intensity regions suggesting
the direction of mass loss was used to assist in the deter-
mination of the polar angle. We used the alignments in the
high intensity structures to determine the polar angles of the
bipolar remnants, except that for PN G 359.8+05.2 we took
the alignment to be perpendicular to that of the high inten-
sity structure. Isophote plots of the bipolar PNe, including
the bipolar remnants, overlaid with lines indicating the PN
orientation and the uncertainty in that orientation are pro-
vided online. Only PNe whose orientation could readily be
determined were included in the sample. Note that projec-
tion effects were not taken into account, i.e. the angles were
measured in the plane of the sky, as we have no informa-
tion of structure along the line of sight. The orientations
for the polar and non-polar PNe were taken to have ran-
dom uncertainties of 2◦
. Initially we also used that value
for the uncertainties in the orientations of the bipolar PNe.
However, to ensure that the evidence of alignment that we
obtained in the statistical tests for those PNe was not down
to using uncertainties that were too small we repeated the
tests on the bipolar PNe using more carefully measured un-
certainties. For the bipolar PNe we used an uncertainty that
is the maximum of:
(i) the estimated population standard deviation of re-
peated measurements of the orientation of the PN;
(ii) the arctangent of the reciprocal of the PN’s tip-to-tip
length in pixels (to allow for a minimum of 1 pixel variation
to account for the image resolution); and
(iii) 2◦
.
c 0000 RAS, MNRAS 000, 000–000
3. Alignment of the Angular Momentum Vectors of Planetary Nebulae in the Galactic Bulge 3
Figure 1. Examples of the classifications of the PNe. PN G 000.2-01.9 was classified as bipolar and PN G 002.7-04.8 was classified as
multilobed bipolar. PN G 003.2-06.2 was also classified as bipolar, i.e point symmetry does not form a class of its own, as was PN G
359.8+05.2, a bipolar remnant, i.e. our bipolar category includes those PNe deemed to be the remnants of bilobed or multilobed PNe.
PN G 352.6+03.0 was classified as polar as it has no lobes and the contours suggest less material in the north and south directions. PN
G 001.7-05.7 shows no internal structure and was classified as non-polar. The greyscale has black as high flux density. The isophotes
are shown in red and are based on 10 per cent intervals of the peak PN flux density. The tick marks on the images without a scale bar
indicate separations of 5 arcsec and those images have north to the top and east to the left.
c 0000 RAS, MNRAS 000, 000–000
4. 4 B. Rees
Overall, 68 of the observed PNe were rejected due to the
selection criteria, imaging problems or uncertain orientation.
The data set that remained consisted of 130 PNe split into
the subsamples described above.
It should be noted that 19 of the PNe, just under one
sixth of our final sample, are also in the analysis presented
in Weidmann & D´ıaz (2008). According to our criteria, 5 of
those 19 are bipolar, 10 polar and 4 non-polar.
The formula presented in Corradi, Aznar & Mampaso
(1998) and the galactic coordinates quoted in SIMBAD for
each PN were used to convert the measured polar angles
(PA) of the PNe to galactic position angles (GPA). Both sets
of values are shown in Table 1 and plots of the orientations
of the PNe in the sample and main subsamples are shown
in Fig. 2.
3 THE ANALYSIS
The analysis was performed using MatlabR
, MathematicaR
and CircStat, the circular statistics toolbox for Matlab,
(Berens 2009). The full sample and the subsamples of bipo-
lar, elliptical, polar and non-polar PNe were analysed as
were subsamples of them based on a split north and south,
and east and west of the Galactic Centre.
The orientation angles occupied almost the whole semi-
circular range so an angle of 1◦
modulo 180◦
is closer to
an angle of 175◦
than it is to one of 10◦
. Consequently the
circular nature of the data could not be ignored. Circular
statistics techniques were used to investigate its distribu-
tion and the statistical tests needed to be invariant under a
rotation of the axes.
As the orientations are axial rather than vector, the
angles range only over 180 degrees. These were doubled to
bring them to modulo 360◦
for much of the analysis, see
Fisher (1995).
As an initial step, finger plots of the distribution of the
GPA and rose plots (a circular form of bar chart) of the
doubled angles were produced for all the samples. The finger
plots provide the fine detail of the information and avoid the
possibly misleading effects of grouping that can occur with
any type of histogram. The plots for the overall sample and
the main subsamples are presented in Figs. 3 and 4.
Quantile–quantile (Q–Q) plots (a type of probability-
probability plot) of the data for each sample were also pre-
pared (Fisher 1995) and those for the whole sample and the
morphological subsamples are shown in Fig. 5. The plots are
extended below (0,0) and above (1,1) with mirrored data
from the other end of the plot. This extension is designed to
avoid any misleading effect due to the linear representation
of circular data. Points from an uniform distribution would
lie on a 45◦
line from the bottom left to top right of such
a plot. Departures from that angle indicate departures from
uniformity.
The mean GPA values were derived in the usual way for
axial data i.e. as a vector summation over 360◦
then halved.
A Rayleigh test, a Hodges-Ajne test, a Kuiper test and
a Watson U2
test for a null hypothesis of uniformity against
an alternative hypothesis of non-uniformity were made. The
Kuiper test has the advantage that it tests for random-
ness against any other alternative whereas the Rayleigh
test assumes an unimodal alternative (Fisher 1995). How-
ever, if the alternative is a von Mises distribution (also
known as the Circular Normal Distribution), the Rayleigh
test is the most powerful invariant test for uniformity
(Bogdan, Bogdan & Futschik 2002). The Hodges-Ajne test
counts numbers on arbitrary semi-circles and checks for an
excess on one side of the circle. It can also be used for sam-
ples from any distribution (Jammalamadaka & SenGupta
2001; Hoenen & Gnaspini 1999; Protheroe 1985) and is use-
ful when a peak in the number of events is likely to be
confined to one half of the angular range. Rayleigh tests
for the same null hypothesis against alternative hypotheses
of an unimodal distribution with mean angles of 90◦
(i.e.
along the Galactic Plane) and 100◦
, the angle of the excess
found by Weidmann & D´ıaz (2008), were also performed.
The p–values for the Kuiper and Watson U2
tests were ob-
tained using Mathematica’s ‘DistributionFitTest’. We ini-
tially used CircStat (Berens 2009) to obtain the p–values
for the Hodges-Ajne test but we then modified the proce-
dure to work in Mathematica as using one statistical pack-
age for all the statistical tests for uniformity simplified boot-
strapping2
. The Rayleigh tests used the formulae presented
in Fisher (1995). The tests are right tail (one-sided excess)
tests, where small p–values would lead us to reject H0.
In order to check the effect of the uncertainties in
the orientations, the full area tests were repeated after
adding randomly selected values from a N 0, σ2
distribu-
tion, where σ is the uncertainty. This process was repeated
100 000 times. We also used bootstrapping to produce a sam-
pling distribution of the p-values. We repeated this with
each of the bootstrapped angles adjusted by a value from
its N 0, σ2
distribution (a smoothed bootstrap).
4 RESULTS
It can already be seen from the rose plots in Figs. 3 and 4
that the plot for the bipolar PNe is less balanced than those
for the other classifications.
Some indications of the uniformity of the distributions
of the GPA can be seen from the Q–Q plots in Fig. 5. The
deviations from the 45◦
line tend to increase as the sample
size decreases, a situation that can also be seen in the plots
for the area subsamples. However, the bipolar sample and its
area subsamples have greater deviations than do the ellip-
tical sample and its area subsamples. Note the pronounced
deviation from a 45◦
slope at approximately (0.5,0.5) in the
plot for the bipolar data sample.
The p–values obtained for the single sample tests are
listed in Table 2 as are the sample sizes. In all five tests the
null hypothesis, H0, is that the distribution of the GPA is
uniform (i.e. when the angles are doubled to cover the full
circle it is isotropic). The alternative hypothesis, H1, for the
four tests for uniformity is simply that the distribution is
not uniform. H1 for the Rayleigh tests against the mean are
those of an unimodal distribution with a mean angle of 90◦
(i.e. along the Galactic Plane) or of 100◦
(i.e the angle of
the excess found by Weidmann & D´ıaz (2008)).
The results for the bipolar PNe are shown in Table 3.
Bootstrapping increases the mean p–value but reduces the
median value. Estimates of the median p-values for the GPA
for the whole area samples of the three morphologies and the
two combined samples are presented in Table 4. They were
obtained from derived from the bootstrapped plus N 0, σ2
uncertainty runs. It can be seen that the results for the bipo-
2 Bootstrapping is a process in which new samples of the same
size are manufactured by sampling from the original sample with
replacement (Efron 1979)
c 0000 RAS, MNRAS 000, 000–000
6. 6 B. Rees
l / °
b/°
all (130)
−10−50510
−10
−5
0
5
10
l / °
b/°
bipolar (44)
−10−50510
−10
−5
0
5
10
l / °
b/°
elliptical (86)
−10−50510
−10
−5
0
5
10
l / °
b/°
polar (55)
−10−50510
−10
−5
0
5
10
l / °
b/°
non−polar (31)
−10−50510
−10
−5
0
5
10
Figure 2. The GPA of the PNe in the samples. They are plotted on a background of contour plots of the 21 cm radio continuum
polarization angles in the Galactic Bulge which are based on data (Testori, Reich & Reich 2008) obtained from Max-Planck-Institut
f¨ur Radioastronomie Survey Sampler (available from: http://www.mpifr-bonn.mpg.de/survey.html). The polarization angles are with
respect to the Galactic North Pole and their magnitudes are indicated by the scale bar at the bottom right. We discuss the use of that
polarization data in §4.
c 0000 RAS, MNRAS 000, 000–000
7. Alignment of the Angular Momentum Vectors of Planetary Nebulae in the Galactic Bulge 7
30
210
60
240
90
270
120
300
150
330
180 0
all (130)
5
10
15
30
210
60
240
90
270
120
300
150
330
180 0
all (130)
30
210
60
240
90
270
120
300
150
330
180 0
bipolar (44)
2
4
6
8
30
210
60
240
90
270
120
300
150
330
180 0
bipolar (44)
30
210
60
240
90
270
120
300
150
330
180 0
elliptical (86)
2
4
6
8
30
210
60
240
90
270
120
300
150
330
180 0
elliptical (86)
Figure 3. Finger plots of the GPA and the rose plots of the doubled GPA for the whole sample, the bipolar PNe and the elliptical
(polar and non-polar) PNe over the whole area. Each dot on a finger plot represents a GPA in the subsample. The radial scale on the
rose plots indicates the number of objects.
c 0000 RAS, MNRAS 000, 000–000
8. 8 B. Rees
30
210
60
240
90
270
120
300
150
330
180 0
polar (55)
2
4
6
30
210
60
240
90
270
120
300
150
330
180 0
polar (55)
30
210
60
240
90
270
120
300
150
330
180 0
non−polar (31)
1
2
3
4
5
30
210
60
240
90
270
120
300
150
330
180 0
non−polar (31)
Figure 4. Finger plots of the GPA and the rose plots of the doubled angles for the polar and non-polar PNe over the whole area. Each
dot on a finger plot represents a GPA in the subsample. The radial scale on the rose plots indicates the number of objects.
lar PNe can be considered as significant at, at worst, the
0.005 significance level.
Runs were also performed for the GPA of the bipolar
sample with the uncertainties increased by 5, 10 and 20 de-
grees in order to check the effects of larger uncertainties. As
expected, increasing the uncertainties increases the proba-
bility that the GPA for the sample come from a randomly
orientated population of bipolar Bulge PNe. The results are
presented in Table 5. The median p–values for uncertain-
ties increased by no more than 10◦
are all below 0.01 with
those for the tests against the specified mean orientations be-
low 0.001. With added 20◦
uncertainties the Rayleigh tests
against the alternative hypotheses of unimodal distributions
with mean values of 90◦
and 100◦
respectively, still produce
p–values 0.01. Any increase in the uncertainties above
those estimated from the measurements would need to be
large in order to change our conclusions.
We note that the NTT images were taken at a fixed
equatorial orientation while the HST images have a random
orientation. Instrumental effects could only have introduced
Equatorial alignments for the NTT images for which we find
no evidence. The conversion from Equatorial to Galactic co-
ordinates gives some rotation of the polar direction across
the area of the Bulge. We therefore repeated the tests for
uniformity of the bipolar PNe using the observed (equato-
rial) PA in order to check for the effect of the conversion
on the p–values. Those results are shown in Table 6. For all
but the Hodges-Ajne test, the median p–values for the boot-
strapped plus N 0, σ2
distributions are larger than those
for the GPA. The non-random nature of the bipolar orien-
tations is therefore an attribute of the Galactic coordinates,
and is not introduced by the Equatorial coordinates.
Our statistical analysis having determined that the
bipolar PNe have a distribution of their orientations that
is unlikely to be random we searched for a possible cause.
We used data from the Max-Planck-Institut f¨ur Ra-
dioastronomie’s Survey Sampler and the circ corrcc function
in CircStat to check for a relationship between the GPA of
the PNe and the Galactic magnetic field using 21 cm polar-
ization angles in the Galactic Bulge from the Villa Elisa sur-
vey as a tracer for the field (Testori, Reich & Reich 2008).
The correlations obtained between the polarization angles
and the GPA of the sample and main subsamples have co-
efficients that lie in the interval (−0.13, 0.21). The low mag-
c 0000 RAS, MNRAS 000, 000–000
9. Alignment of the Angular Momentum Vectors of Planetary Nebulae in the Galactic Bulge 9
−0.5 0 0.5 1 1.5
−0.4
−0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
uniform quantiles
samplequantiles
all (130)
−0.5 0 0.5 1 1.5
−0.4
−0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
uniform quantiles
samplequantiles
bipolar (44)
−0.5 0 0.5 1 1.5
−0.4
−0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
uniform quantiles
samplequantiles
elliptical (86)
−0.5 0 0.5 1 1.5
−0.4
−0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
uniform quantiles
samplequantiles polar (55)
−0.5 0 0.5 1 1.5
−0.4
−0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
uniform quantiles
samplequantiles
non−polar (31)
Figure 5. The extended quantile-quantile (Q–Q) plots for the full sample and the principal subsamples over the whole area. Q-Q plots
for the bipolar PNe in the North, South, East and West subsamples are available online.
c 0000 RAS, MNRAS 000, 000–000
10. 10 B. Rees
Table 2. The data for the PNe samples and area sub-samples together with the p–values for the single sample tests. The angles are
shown rounded to the nearest 1◦ and the p–values have been quoted to the first significant digit. The p–values derived for the non-polar
south-west subsample have been excluded as the sample size of 3 indicates that they are not meaningful. The null hypothesis (H0) for
all the tests is that the distribution of the GPA is uniform. East (E), west (W), north (N) and south (S) are with respect to Galactic
coordinates on either side of 0◦longitude and latitude.
p–values
Class Area sample mean Tests for Uniformity Rayleigh Test
size GPA H1: the distribution is not uniform H1: an unimodal mean GPA of:
/ ◦ Rayleigh Hodges-Ajne Kuiper Watson U2 90◦ 100◦
All All 130 95 0.3 0.4 0.3 0.2 0.06 0.06
Bipolar All 44 93 0.0008 0.02 0.0002 0.006 0.00009 0.0001
Elliptical All 86 176 0.8 0.9 0.5 0.7 0.2 0.3
Polar All 55 158 0.9 0.9 0.6 0.7 0.4 0.4
Non-polar All 31 8 0.7 0.9 0.9 0.9 0.2 0.2
All E 72 70 0.6 0.5 0.8 0.8 0.2 0.3
All W 58 109 0.2 0.4 0.1 0.1 0.06 0.03
All N 61 107 0.1 0.3 0.1 0.1 0.04 0.02
All S 69 63 0.7 0.9 0.8 0.7 0.3 0.4
All NE 28 99 0.3 0.8 0.6 0.5 0.07 0.06
All NW 33 114 0.3 0.5 0.3 0.3 0.2 0.08
All SE 44 40 0.5 0.6 0.5 0.6 0.4 0.3
All SW 25 100 0.5 0.9 0.4 0.5 0.1 0.1
Bipolar E 21 88 0.08 0.2 0.1 0.05 0.01 0.02
Bipolar W 23 97 0.008 0.1 0.005 0.01 0.001 0.001
Bipolar N 19 101 0.006 0.05 0.002 0.009 0.001 0.0006
Bipolar S 25 84 0.05 0.1 0.04 0.02 0.009 0.02
Bipolar NE 8 92 0.02 0.06 0.02 0.02 0.002 0.003
Bipolar NW 11 111 0.1 0.1 0.08 0.1 0.07 0.03
Bipolar SE 13 75 0.7 0.5 0.6 0.4 0.2 0.3
Bipolar SW 12 87 0.02 0.06 0.03 0.03 0.003 0.007
Elliptical E 51 24 0.7 0.9 0.9 0.8 0.3 0.2
Elliptical W 35 148 0.6 0.5 0.4 0.5 0.3 0.5
Elliptical N 42 129 0.8 0.9 0.8 0.9 0.4 0.4
Elliptical S 44 11 0.5 0.8 0.5 0.5 0.1 0.1
Elliptical NE 20 136 0.9 0.9 1. 1. 0.5 0.4
Elliptical NW 22 124 0.9 0.9 0.6 0.8 0.4 0.4
Elliptical SE 31 29 0.4 0.7 0.7 0.4 0.2 0.1
Elliptical SW 13 159 0.4 0.5 0.6 0.5 0.2 0.3
Polar E 33 21 1. 1. 0.6 0.7 0.5 0.5
Polar W 22 155 0.8 0.9 0.8 0.9 0.3 0.4
Polar N 26 41 0.9 0.9 0.9 0.9 0.5 0.4
Polar S 29 147 0.7 0.7 0.6 0.6 0.4 0.5
Polar NE 14 62 0.9 0.7 0.9 1. 0.4 0.5
Polar NW 12 22 0.9 1. 0.9 1. 0.4 0.3
Polar SE 19 160 1. 1. 0.7 0.7 0.4 0.4
Polar SW 10 143 0.5 0.5 0.5 0.5 0.4 0.5
Non-polar E 18 24 0.4 0.5 0.5 0.4 0.2 0.1
Non-polar W 13 140 0.7 0.9 0.5 0.7 0.4 0.4
Non-polar N 16 129 0.3 0.8 0.4 0.3 0.4 0.2
Non-polar S 15 27 0.05 0.07 0.08 0.08 0.08 0.02
Non-polar NE 6 143 0.5 0.2 0.3 0.4 0.4 0.5
Non-polar NW 10 119 0.5 0.5 0.4 0.4 0.3 0.2
Non-polar SE 12 34 0.08 0.06 0.1 0.1 0.2 0.07
Non-polar SW 3 4
nitudes of the correlation coefficients suggest that there is
little, if any, relationship between the orientation of PNe and
the current Galactic magnetic field. It should, however, be
noted that the result does not allow for depolarization due
to Faraday rotation (Testori, Reich & Reich 2008) and that
the wavelength of the Villa Elisa survey is too long to avoid
that effect. Moreover the resolution of the survey is too low
to match the locations of the PNe with sufficient precision so
we are unable to come to any conclusion regarding a possible
relationship.
As any effect from external magnetic fields is likely to
become more pronounced with the age of a PN we also de-
cided to look for any relationship between the lobe lengths of
the bipolar nebulae and their orientation. We measured the
lengths of the PN from lobe tip to lobe tip at (for the most
part) 1 per cent of the peak intensity level. Linear regression
(the procedure g02ca of The NAG Toolbox for MATLAB)
was used to test for any relationship between GPA and that
length. Plots of the relationship between PN orientation and
PNe size are shown in Fig. 6. A plot of the orientation of
the bipolar PNe against radial velocity is provided as Fig. 7
and those for the polar and non-polar PNe are provided
c 0000 RAS, MNRAS 000, 000–000
11. Alignment of the Angular Momentum Vectors of Planetary Nebulae in the Galactic Bulge 11
Table 3. Sampling distributions of the p–values for the GPA of the bipolar PNe sample. There were 100 000 such samples for each of: the
measured value plus a randomly selected N 0, σ2 value where σ is the uncertainty in the PN orientation, a bootstrapped selection from
the measured values with duplicates adjusted by adding multiples of 10−8 degrees and the bootstrapped selection plus the randomly
selected N 0, σ2 value. Quoted uncertainties in the statistics are based on the distribution of 100 subsamples of size 1 000 where that
distribution is judged to be Normal using an Anderson–Darling test at a 0.5 significance level.
test method mean standard quantiles
deviation median 16% 84%
Rayleigh measured + N 0, σ2 0.00123±0.00002 0.00065±0.00002 0.00109±0.00002 0.00066±0.00001 0.00178±0.00004
bootstrapped 0.013±0.002 0.046±0.007 0.00050±0.00008 0.000007±0.000002 0.012±0.002
bootstrapped + N 0, σ2 0.015±0.002 0.051±0.007 0.0006 0.00001 0.015±0.002
Hodges-Ajne measured + N 0, σ2 0.02 0.0137±0.0003 0.02 0.007 0.05
bootstrapped 0.025±0.002 0.058±0.006 0.007 0.0001 0.05
bootstrapped + N 0, σ2 0.025±0.002 0.062±0.007 0.002 0.0001 0.05
Kuiper measured + N 0, σ2 0.00089±0.00003 0.00095±0.00007 0.00059±0.00002 0.00022±0.00001 0.00149±0.00006
bootstrapped 0.0017±0.0003 0.009±0.003 0.00003 0.0000002 0.0009
bootstrapped + N 0, σ2 0.0026±0.0005 0.01 0.00007 0.0000009±0.0000002 0.002
Watson U2 measured + N 0, σ2 0.00650±0.00003 0.00076±00002 0.00651±0.00003 0.00573±0.00003 0.00725±0.00004
bootstrapped 0.0066±0.0005 0.015±0.003 0.0045±0.0002 0.0000006 0.0086±0.0001
bootstrapped + N 0, σ2 0.0082±0.0007 0.020±0.004 0.0051±0.0002 0.00002 0.009±0.0002
Rayleigh measured + N 0, σ2 0.000134±0.000002 0.000080±0.000003 0.000120±0.000003 0.000069±0.000002 0.000204±0.000005
H1: 90◦ bootstrapped 0.0032±0.0005 0.015±0.003 0.00008±0.00001 0.0000012±0.0000003 0.0024±0.0004
unimodal bootstrapped + N 0, σ2 0.0039±0.0006 0.017±0.004 0.0001 0.000002 0.0031±0.0005
Rayleigh measured + N 0, σ2 0.000200±0.000004 0.000110±0.000005 0.000175±0.000003 0.000105±0.000002 0.000290±0.000007
H1: 100◦ bootstrapped 0.0054±0.0007 0.023±0.004 0.00012±0.00002 0.000001 0.004
unimodal bootstrapped + N 0, σ2 0.0062±0.0008 0.025±0.004 0.00016±0.00003 0.000002 0.0050±0.0008
Table 4. The median p–values for the GPA of the five single sample tests. The values and their uncertainties were obtained by
bootstrapping the GPA and adding a randomly selected N 0, σ2 value, where σ is the uncertainty in the PN orientation for the bipolar
PNe and 2◦ for the other PNe. The median has been used due to the distributions of the p–values being skewed. There were 100 000
bootstraps. The samples of 100 000 were each split into subsamples of 1 000 and the mean and standard deviation of the median p-value
obtained. Where the distribution of the medians was judged to be Normal using an Anderson–Darling test at a 0.5 significance level
its standard deviation was used as the uncertainty, otherwise the p–value has been quoted to the first significant digit. The mean GPA
quoted is that of the original sample.
median p–values
Class sample mean Tests for Uniformity Rayleigh Test with H1:
size GPA
Rayleigh Hodges-Ajne Kuiper Watson U2 an unimodal mean GPA of:
/ ◦ 90◦ 100◦
All 130 95 0.17±0.01 0.1 0.038±0.003 0.082±0.005 0.063±0.005 0.061±0.005
Bipolar 44 93 0.0006 0.002 0.00007 0.0051±0.0002 0.0001 0.00016±0.00003
Elliptical 86 176 0.40±0.02 0.3 0.16±0.01 0.22±0.01 0.205±0.009 0.214±0.009
Polar 55 158 0.47±0.01 0.4 0.152±0.008 0.194±0.008 0.264±0.008 0.264±0.008
Non-polar 31 8 0.39±0.02 0.5 0.24±0.01 0.29±0.01 0.186±0.008 0.183±0.008
online. The Pearson product-moment correlation coefficient
from the linear regression of the GPA against length are -
0.009 for the bipolar GPA against lobe length, 0.02 for the
polar GPA against polar length and -0.005 for the non-polar
GPA against the length along the major axis. We thus find
no relationship between nebular age and orientation.
We also used linear regression to check for
any relationship between the PN orientation and
its radial or expansion velocity. The radial veloc-
ities were obtained from Durand, Acker & Zijlstra
(1998); Malaroda, Levato & Galliani (2006);
Beaulieu, Dopita & Freeman (1999); Acker et al. (1992)
and the expansion velocities from Gesicki & Zijlstra (2007)
and K. Gesicki (private communication). The correlation
coefficients for the GPA against the radial velocity lie in
the interval (-0.1,0.08) with that for the bipolar PNe being
-0.092. The correlation coefficients for the GPA against
expansion velocity lie in the interval (-0.2,0.3). Therefore
there appears to be no relationship between orientation and
either velocity.
Some caution is required when considering this analysis
in that the angles were measured in the plane of the sky and
no adjustment to allow for projection effects was attempted.
We do not have the additional data to derive the extent of
the PNe along the line of sight. The fact that the data is
two dimensional has two effects: First, it raises the possi-
bility that some bipolar PNe were observed approximately
along the lobes and consequently misclassified. Secondly, if
we consider the angles of the PNe taken from the Galactic
North Pole, through the lobe-to-lobe axis of PN towards the
Galactic Plane the true angles will be more concentrated to-
wards 90◦
. This can readily be seen by considering the GPA
as lying on the diagonal of the front (rear) face of a cuboid
with the PN stretching from the bottom right of that face
to the top left of the rear (front) face see Fig. 8. From the
figure we can see that:
r cos θ = l cos ψ (1)
c 0000 RAS, MNRAS 000, 000–000
12. 12 B. Rees
Table 5. The effect of uncertainties in the orientations on the sampling distributions of the p–values for the GPA of the bipolar PNe
sample. The results indicated to have 0◦ additional uncertainty are those shown in the third row for each test in Table 3. They are for
100 000 bootstrapped selections from the measured values to which were added values randomly selected from a N 0, σ2 distribution,
where σ is the uncertainty in the PN orientation. Those results are compared to three further sets of 100 000 for which σ was increased
by values of 5, 10 and 20◦ respectively. Quoted uncertainties in the statistics are based on the distribution of 100 subsamples of size
1 000 where that distribution is judged to be Normal using an Anderson–Darling test at a 0.5 significance level.
test added mean standard quantiles
uncertainty/◦ deviation median 16% 84%
Rayleigh 0 0.015±0.002 0.051±0.007 0.0006 0.00001 0.015±0.002
5 0.021±0.002 0.067±0.007 0.001 0.00002 0.025±0.003
10 0.038±0.003 0.100±0.008 0.003 0.00005 0.018±0.05
20 0.106±0.006 0.190±0.009 0.018±0.002 0.00037±0.00009 0.22±0.02
Hodges-Ajne 0 0.025±0.002 0.062±0.007 0.002 0.0001 0.05
5 0.029±0.002 0.075 0.002 0.0001 0.05
10 0.043±0.003 0.102±0.008 0.007 0.0001 0.05
20 0.103±0.006 0.179±0.008 0.02 0.0006 0.2
Kuiper 0 0.0026±0.0005 0.01 0.00007 0.0000009±0.0000002 0.002
5 0.0071±0.0008 0.028±0.005 0.00027±0.00004 0.000004 0.0066±0.0009
10 0.016±0.002 0.051±0.006 0.0008 0.000012±0.000003 0.02
20 0.050±0.004 0.111±0.007 0.0052±0.0007 0.00009±0.00002 0.085±0.009
Watson U2 0 0.0082±0.0007 0.020±0.004 0.0051±0.0002 0.00002 0.009±0.0002
5 0.0132±0.0009 0.03 0.0062±0.0002 0.0012±0.0002 0.01
10 0.024±0.002 0.060±0.007 0.0074±0.0002 0.0024±0.0003 0.03
20 0.067±0.004 0.126±0.007 0.01 0.0050±0.0003 0.12±0.01
Rayleigh 0 0.0039±0.0006 0.017±0.004 0.0001 0.000002 0.0031±0.0005
H1: 90◦ 5 0.006 0.024±0.004 0.0002 0.000004 0.0056±0.0007
unimodal 10 0.013±0.001 0.041±0.004 0.00058±0.00008 0.000009±0.000002 0.014±0.002
20 0.047±0.003 0.093±0.004 0.006 0.0001 0.090±0.008
Rayleigh 0 0.0062±0.0008 0.025±0.004 0.00016±0.00003 0.000002 0.0050±0.0008
H1: 100◦ 5 0.0088±0.0009 0.032±0.004 0.00032±0.00005 0.000004 0.009±0.001
unimodal 10 0.02 0.05 0.0008±0.0001 0.00001 0.019±0.002
20 0.052±0.003 0.097±0.004 0.007 0.0001 0.104±0.009
Table 6. Sampling distributions of the p–values for the PA of the bipolar PNe sample. There were 100 000 such samples for each of: the
measured value plus a randomly selected N 0, σ2 value where σ is the uncertainty in the PN orientation, a bootstrapped selection from
the measured values with duplicates adjusted by adding multiples of 10−8 degrees and the bootstrapped selection plus the randomly
selected N 0, σ2 value. Quoted uncertainties in the statistics are based on the distribution of 100 subsamples of size 1 000 where that
distribution is judged to be Normal using an Anderson–Darling test at a 0.5 significance level.
test method mean standard quantiles
deviation median 16% 84%
Rayleigh measured + N 0, σ2 0.00228±0.00004 0.00115±0.00004 0.00204±0.00004 0.00126±0.00003 0.00328±0.00008
bootstrapped 0.019±0.002 0.060±0.007 0.0010±0.0001 0.00002 0.022±0.003
bootstrapped + N 0, σ2 0.022±0.002 0.066±0.007 0.0012±0.0002 0.00002 0.026±0.003
Hodges-Ajne measured + N 0, σ2 0.0310±0.0005 0.02 0.02 0.02 0.05
bootstrapped 0.031±0.002 0.071±0.005 0.007 0.0001 0.05
bootstrapped + N 0, σ2 0.037±0.002 0.082±0.006 0.007 0.0006 0.05
Kuiper measured + N 0, σ2 0.00117±0.00005 0.001 0.00074±0.00003 0.00026±0.00001 0.0020±0.0001
bootstrapped 0.0024±0.0004 0.012±0.004 0.00006 0.0000004 0.002
bootstrapped + N 0, σ2 0.0038±0.0006 0.017±0.004 0.0001 0.000001 0.0030±0.0003
Watson U2 measured + N 0, σ2 0.00721±0.00003 0.00076±0.00002 0.00722±0.00003 0.00645±0.00004 0.00796±0.00003
bootstrapped 0.0087±0.0006 0.020±0.003 0.0053±0.0002 0.0002 0.0093±0.0002
bootstrapped + N 0, σ2 0.0105±0.0008 0.025±0.004 0.0058±0.0002 0.0008±0.0002 0.01
r sin α sin θ = l sin ψ (2)
and
l r (3)
where l and r are the observed and actual lengths of the PN,
and ψ, θ and α are the GPA, the angle from Galactic North
to the axis of the PN and the angle of the axis of the PN
projected onto the Galactic Plane from the PN’s Galactic
longitude, respectively. We also have
r rmax (4)
where rmax is the maximum permitted PN length of 35 arc-
sec, see §2. From equation 1 we can see that the value of
the angle from Galactic North to the PN axis is closer to
90◦
than is the GPA.
c 0000 RAS, MNRAS 000, 000–000
13. Alignment of the Angular Momentum Vectors of Planetary Nebulae in the Galactic Bulge 13
0 5 10 15 20 25 30 35
0
50
100
150
200
250
300
350
lobe length / arcsec
GPA/°
0 5 10 15
0
50
100
150
200
250
300
350
polar length / arcsec
GPA/°
0 2 4 6 8 10 12
0
50
100
150
200
250
300
350
major axis length / arcsec
GPA/°
Figure 6. The GPA of the PNe plotted against the lobe to lobe dimensions of the 44 bipolar PNe (red, top left), the polar lengths of the
55 polar PNe (blue, bottom left) and the lengths along the major axis of the 31 non-polar PNe (green, bottom right). The PNe appear
twice in order to emphasize the axial nature of the angular data, once for the GPA and once for the GPA plus 180◦. The horizontal
lines at 100◦and 280◦are to allow comparison with the angle of excess found by Weidmann & D´ıaz (2008). The uncertainties forming
the error bars for the lengths are dominated by the pixelation and are taken to be 1 s.d.
Due to the rotation of the Bulge it seems reasonable
to assume that the orientations of the projections onto the
Galactic Plane are random. We created 100 000 possible
samples based on our bipolar samples where, for each sam-
ple, the true length of each PN was estimated based on a
random angle in the range [0,180) degrees that was taken
as the (axial) orientation of its projection onto the Galac-
tic Plane. Equations 1 to 3, the PN’s GPA and its pro-
jected length on the sky, and the maximum permitted PN
length were used to ensure the validity of the angle on the
Plane. We used the measured PN lengths of Rees, Zijlstra
and Gesicki (in preparation) and the maximum permitted
PN length of 35 arcsec (neither the observed nor maximum
length changes due to the change in coordinates). The pro-
cess was repeated for each PN until a ‘valid’ angle on the
Plane was obtained whereupon the value of θ obtained from
equation 1 was used as the angle from Galactic North down
to the axis of the PN. The randomness of the angles in the
sample was then checked using the same tests as in §3. The
results are shown in Table 7 and suggest that the distri-
bution of the angles from North is not random. Note that
this process did not involve bootstrapping. Histograms of
the derived angles are provided online.
5 DISCUSSION
5.1 Alignment
We divide the sample of PNe into three separate morpholog-
ical categories. The statistics tell us that one of those cate-
gories, the bipolar PNe, shows evidence for alignment with
the Galactic Plane while the other two appear to have ran-
c 0000 RAS, MNRAS 000, 000–000
14. 14 B. Rees
Table 7. The p–values for the deprojected angles from Galactic North to the axes of the bipolar PNe sample. They are for 100 000
samples made up as follows. A random angle in the range [0,180) degrees was produced for each PN and used as the (axial) orientation
when projection onto the Galactic Plane. The equations in §4 together with the PN’s GPA, its projected length on the sky as measured
from the observations, and a maximum permitted ‘true’ PN length of 35 arcsec, see §2, were used to ensure the validity of the angle on
the Plane. The process was repeated until a ‘valid’ angle on the Plane was obtained whereupon the angle from Galactic North down to
the axis of the PN obtained from equation 1 was used as the sample value for the PN. The null hypothesis (H0) for all the tests is that
the distribution of the angles of the nebular axes from Galactic North is uniform. Quoted uncertainties in the statistics are based on
the distribution of 100 subsamples of size 1 000 where that distribution is judged to be Normal using an Anderson–Darling test at a 0.5
significance level. The mean angle from Galactic North was estimated as 91.10 ± 0.04◦.
test mean standard quantiles
deviation median 16% 84%
Rayleigh 3 × 10−6 5 × 10−6 8.3±0.6 × 10−7 1.2±0.1 × 10−7 4.3±0.3 × 10−6
H1: non-uniform
Hodges-Ajne 1.5±0.1 × 10−4 3.9±0.6 × 10−4 3 × 10−5 4 × 10−6 1 × 10−4
Kuiper 7.1±0.4 × 10−6 1.4±0.1 × 10−5 2.3±0.2 × 10−6 3 × 10−7 1.22±0.08 × 10−5
Watson U2 6 × 10−5 2.5±0.2 × 10−4 < 10−7 < 10−7 < 10−7
Rayleigh 2 × 10−7 4 × 10−7 6 × 10−8 9 × 10−9 3.3±0.03 × 10−7
H1: unimodal, 90◦ mean
−200 −100 0 100 200
0
20
40
60
80
100
120
140
160
180
radial velocity/ km s
−1
GPA/°
Figure 7. The GPA of the 44 bipolar PNe plotted against their
Radial Velocities.The uncertainties forming the error bars for the
radial velocities are taken from the catalogues. The figures for the
polar and non-polar PNe are available online.
dom alignments. Our result for the bipolar PNe appears to
be in reasonable conformity with that for the elongated PNe
in the Galactic Centre region of Weidmann & D´ıaz (2008).
The GPA of the full sample of 130 PNe has an uniform
distribution even with a significance level of 0.01 as used by
Weidmann & D´ıaz (2008). This is also true for the samples
of 55 polar, 31 non-polar and 86 elliptical (combined polar
and non-polar) PNe and is the case for all the statistical
tests for uniformity, see Tables 2 and 4.
A different result arises when we consider the bipolar
subsample. If we restrict ourself to the measured values with
no added uncertainties and no bootstrapping (Table 2), the
Kuiper and Rayleigh tests for uniformity against a simple
non-uniform alternative allow us to reject the null hypothesis
of uniformity of the sample at a 0.001 significance level, the
Watson U2
test does so at the 0.01 level.
The Hodges-Ajne test does not let us reject uniformity.
That test counts numbers on arbitrary semi-circles on the
α
ψ
θ
α
l
r
N
0˚
E
Figure 8. A schematic of the 3D situation. The axis of the PN
is denoted by the blue line, its length by r and the angle from
Galactic North to the axis by θ. The projection onto the sky has
its axis denoted by the red line, its length by l and the GPA by
ψ. The projection onto the Galactic Plane is shown by the dotted
blue line and its angle from 0◦by α. That line and its angle are
repeated on the top face of the cuboid to clarify the derivation of
the angle in the text. Similar schematics are valid for a PN with
ψ > 90◦ and/or α > 90◦.
full circle and checks for an excess on one side. It has low
resolution for a sample size of 44 as an increase or decrease
of 1 in the minimum number on a semicircle can cause a
large change in the p–value. A minimum of 11 angles on the
semicircle produces a p–value of 0.02 whereas values of 10
and 12 produce p–values of 0.01 and 0.05 respectively. In
effect there is a problematical step change in the p–values.
The test also has higher standard deviations for the p–values
than do the other tests for all the categories in Tables 3, 6
and 5. This suggests that it has less discriminatory value
than other tests and we therefore place more weight on the
results from them.
The Rayleigh tests for uniformity against the alterna-
tive of an unimodal distribution with mean values of 90◦
(i.e. along the Galactic Plane) and 100◦
both produce p–
values below 0.0002. Fisher (1995) points out that tests with
a simple non-uniformity alternative may not be very good
at detecting something specific like unimodality whereas a
c 0000 RAS, MNRAS 000, 000–000
15. Alignment of the Angular Momentum Vectors of Planetary Nebulae in the Galactic Bulge 15
test designed to detect that attribute may not be very good
at detecting other types of non-uniformity. This difference
might explain the difference in the results. The finger plots
and rose plots of the bipolar sample indicate that it is rea-
sonable to make an assumption of unimodality for it, which
supports the use of the Rayleigh test against unimodal dis-
tributions.
The median p–values given in Table 4 confirm the ba-
sic result. Two of the tests for uniformity against a simple
non-uniform alternative allow us to reject the null hypoth-
esis of uniformity of the bipolar sample at the 0.001 (99.9
per cent) significance level and the other two do so at the
0.01 (99 per cent) significance level. The Rayleigh tests for
uniformity against unimodal distributions with mean values
of 90◦
and 100◦
both allow us to reject the null hypothesis
of uniformity of the bipolar sample at the 0.0002 (99.98 per
cent) significance level.
We did not pursue the results for any of the area sub-
samples using bootstrapping. However, the basic results,
shown in Table 2, suggest that the non-random nature of the
orientations is not due to some localized subset of the bipo-
lar PNe. At the 0.01 significance level, the Rayleigh, Kuiper
and Watson U2
tests indicate that the orientations of the
bipolar PNe are not random for either the West or North
subsamples. The Rayleigh tests for uniformity against the
alternative of an unimodal distribution with mean values of
90◦
(i.e. along the Galactic Plane) and 100◦
also permit us
to reject uniformity for some of the bipolar area subsamples
at that significance level. We can do so for the West, North,
North East and South West subsamples for both those mean
orientations and for the South and East subsamples for the
90◦
mean orientation.
Corradi, Aznar & Mampaso (1998) found little evi-
dence for alignments of PNe within the Galaxy. However,
their sample of 209 PNe were spread around the Galaxy
in terms of Galactic longitude and contained only 12 Bulge
PNe. Weidmann & D´ıaz (2008) found an excess of elongated
PNe toward the Galactic Centre that are oriented at 100◦
.
As our sample and theirs have only 19 objects in common,
of which only five are bipolar in our classification, we have
an independent test of a potential alignment. We have re-
stricted our study to PNe in the Bulge and, having taken
the factors listed above into account, we consider that there
is evidence that the GPA of the bipolar PNe in the Galactic
Bulge do not have an uniform distribution. That is, that the
two-dimensional orientation of the bipolar PNe in the Galac-
tic Bulge is not random. Moreover, we find evidence of an
alignment with a mean approximately along the Galactic
Plane.
PN orientations are expected to be independent of each
other because a PN’s shape is set by processes internal to the
originating star or stellar system. A mechanism is required.
5.2 Orientation Changes After PN Ejection
The velocity graphs in Fig. 7 together with the small Pear-
son product-moment correlation coefficients for the radial
and expansion velocity regressions suggest that there is no
relationship between PN orientation and either PN radial
velocity or PN expansion velocity. Similarly, Fig. 6 together
with low Pearson product-moment correlation coefficients
suggest that there is no relationship between PN orienta-
tion and size. In particular, the plot for the bipolar PNe in
Fig. 6 together with a Pearson product-moment correlation
coefficient of -0.009 from a simple linear regression of the
GPA against the PNe angular size from lobe tip to lobe tip,
demonstrates that the orientation of bipolar PNe is not re-
lated to lobe length. The variation in distance to the PNe is
unlikely to be such as to change that conclusion.
The lobe length of a bipolar PN is related to the age of
the PN. The lack of relation between orientation and lobe
length suggests that the orientation is set during the youth
of the PN or before it has formed. There is no evidence that
the orientation changes during the PN evolution. The ex-
pansion velocity tends to be higher for higher-mass central
stars (although this may not be important for the old stellar
population of the Galactic Bulge), or for emission-line cen-
tral stars (Gesicki et al. 2006). These aspects are not shown
to be related to the orientation. We also found no evidence
that orientation is related to radial velocity.
It has been suggested that magnetic fields in the in-
terstellar medium (ISM) elongate stellar wind bubbles and
that this is important in the production of bilateral super-
nova remnants (Gaensler 1998). In the case of PNe however,
that magnetic field can have little effect during the forma-
tion of the nebula due to the small size scales involved (the
wind acceleration region is located within 1–10 AU from
the star) and the high densities in the wind. Moreover, this
mechanism would not explain why the alignment is found
only for bipolar PNe.
5.3 Angular momentum
The currently favoured view for shaping non-spherical PNe
is that of binary interactions (de Marco 2009) . In this
model, either an AGB star provides spherical ejecta and its
interactions with a binary companion shapes those ejecta, or
a close binary forms a common envelope leading to aspheri-
cal ejecta (Zijlstra 2007). Stellar magnetic fields also provide
possible shaping mechanisms, however Soker (2006) argues
that sufficiently strong fields still require a companion to
continuously spin up the envelope.
The distinction between bipolar and other PNe is likely
related to the amount of angular momentum available for
shaping. The angular momentum available for shaping is
set by a balance between the orbital angular momentum and
the efficiency of the transfer of momentum. Bipolar nebulae
show dense tori which shape the polar flows. They may arise
from intermediate (∼1 yr) and short-period ( 0.1 yr) bina-
ries. Shorter period binaries form common-envelope systems
and nebulae ejected by them often show thin rings rather
than dense tori (Zijlstra 2007), possibly related to the lower
angular momentum available in close systems. For common
envelope systems the momentum transfer efficiency will be
100%; the percentage is lower for wider systems. The widest
binaries ( 10 yr) show spiral features but do not form bipo-
lar nebulae (Maercker et al. 2012).
Although the orbit of a star around the Galaxy may
change due to interactions with other bodies, the angular
momentum vector of the stellar system tends to remain sta-
ble. The Kozai–Lidov mechanism (a three-body interaction)
(Shappee & Thompson 2013) could prevent the retention of
any alignment of binary systems that occurs during the early
stages of star formation i.e. it could randomize the align-
ments. However, any method of alignment of the PNe in
the later stages of the lives of the systems that form them
would then be required to operate over kiloparsec distances
and appears implausible. Consequently, given that we have
found an alignment, that alignment must have originated
during the formation of the stars.
c 0000 RAS, MNRAS 000, 000–000
16. 16 B. Rees
5.4 A proposed mechanism
The dense molecular clouds within about 4◦
of the Galac-
tic centre tend to have their magnetic fields aligned along
the Galactic plane (Morris 1998) and these fields are quite
uniform and strong. If that was also the case for the Bulge
at the time of its star formation, a propensity for the stars
which form the bipolar PNe to align with the magnetic field
of the cloud from which they themselves are formed could
provide an explanation for the non-random distribution of
the PNe orientations.
A strong magnetic field embedded in a star-forming
cloud slows the contraction of star-forming cores along the
direction perpendicular to the magnetic field (Tang et al.
2009). The material around the collapsing young stellar
objects may be expected to contract more quickly along
the magnetic field. If a binary forms in the thus-flattened
cloud, the separation will on average be larger perpendicu-
lar to the field. As wider binaries carry more angular mo-
mentum, this gives a preferential angular momentum vec-
tor of the binary population along the magnetic field. So
the stronger the field, the greater is the propensity towards
forming wide binaries with orbits perpendicular to that field.
Whether this occurs in reality is controversial. Hydrody-
namical models indicate that for larger fields (∼ 80 µG),
outflows indeed become oriented along the magnetic field
lines (Matsumoto, Nakazato & Tomisaka 2006). Also, the
3D MHD simulations of Nakamura & Li (2008) appear to
show that star formation in relatively diffuse clouds con-
taining strong magnetic fields is controlled by those fields,
not by turbulence.
The evidence for orientation of stellar rotation axes
along interstellar magnetic field lines in nearby-clusters is
not conclusive. While the T Tauri stars FU Ori and DR
Tau have their stellar axes aligned with the larger mag-
netic field direction (Vink et al. 2005), other studies sug-
gest that the orientation of young stellar objects in a clus-
ter is random (M´enard & Duchˆene 2004; Jackson & Jeffries
2010). However, no studies have been made on possible
alignment of binary orbits within young clusters. Binary
orbits carry far more angular momentum than does stel-
lar rotation, and the result from the Galactic Bulge PNe
could indicate that the alignment survives only in binary
systems. We can also not exclude the possibility that mag-
netic fields within the Bulge during its formation were
considerable stronger than those in the Solar neighbour-
hood. Matsumoto, Nakazato & Tomisaka (2006) show that
the strength of the field is an important parameter, with
alignment occurring above 80 µG.
The alignment of bipolar PNe suggests that there was
an alignment of stellar systems in the Bulge at the time of
the formation of the stars, most clearly seen for those ob-
jects with the largest angular momentum. That alignment
lies approximately along the Galactic plane. This implies
that the binary systems in the Galactic Bulge have angular
momentum vectors that are preferentially aligned along the
Galactic plane. There is strong evidence for cylindrical ro-
tation in the Bulge, with angular momentum perpendicular
to the Galactic plane (Howard et al. 2009). We thus have
the counter-intuitive situation that binary systems out of
which bipolar PNe are formed have their angular momen-
tum vector perpendicular to that of the Bulge in which they
formed.
In conclusion, we have evidence that the orientation of
bipolar PNe in the Bulge is not random. The argument that
we use is that the angular momentum vectors are aligned.
This effect is likely to date from the origin of the central
stars of the PNe. Interstellar magnetic fields at the time of
the formation of the Bulge provide a possible mechanism.
6 SUMMARY
We have classified 130 PNe that we consider to be in the
Galactic Bulge into three morphological categories. For each
of those PNe, we determined a position angle for the polar
direction and converted that to an angle from Galactic north
to Galactic east. We then undertook a statistical analysis
of those angles and found that for one of the morphological
classes, the bipolar class, there is evidence for a non-random
distribution of the angles at significance levels equivalent to
that between 2.3σ and 3.7σ (depending on the test used)
for a Gaussian distribution. The mean orientation is aligned
approximately to that of the galactic plane. On the basis
that the orientation of the bipolar nebulae is independent
of their size we propose a mechanism for the production of
that non-random distribution of orientations.
The debate on the main shaping mechanism in PNe has
concentrated on binarity and magnetic fields. Currently, bi-
nary systems are seen as the dominant effect (this may be
of course be influenced by the fact that binaries are easier
to detect than magnetic fields), with magnetic fields having
a secondary role. The hypothesis put forward in this paper
is that the alignment of bipolar planetary nebulae can be
understood if star formation in the Bulge occurred in the
presence of strong magnetic fields oriented along the Galac-
tic plane and if the parameters of the binary systems them-
selves are in part the product of magnetic fields present at
their origin. This reverses again cause and effect. The long
debate has shown that both effects are difficult to separate,
and are to a significant degree intertwined.The estimated
ages of stars in the Bulge vary with estimates from 8 to
∼13 Gyr (Rich 2001; Minniti & Zoccali 2008; Bensby et al.
2010). The claim in this paper is that this interaction be-
tween field and binarity dates back to the processes acting
during the origin of the stars, a form of archaeomagnetism
of the early Universe.
We are of the view that a similar analysis should be
performed on high resolution observations of a much larger
sample of bipolar PNe in the Galactic Bulge.
ACKNOWLEDGEMENTS
We thank Clive Dickinson for discussions on the available
polarization data for the Galactic Bulge and Iain McDonald
for discussions on the projections.
This research has made use of the SIMBAD database,
and the VizieR catalogue access tool, CDS, Strasbourg,
France.
REFERENCES
Acker A., Marcout J., Ochsenbein F., Stenholm B.,
Tylenda R., 1992, Strasbourg - ESO catalogue of galac-
tic planetary nebulae. Part 1; Part 2. Garching: European
Southern Observatory
Acker A., Peyaud A. E. J., Parker Q., 2006, in Barlow M. J.,
M´endez R. H., eds., IAU Symposium, Vol. 234, Planetary
Nebulae in our Galaxy and Beyond, p. 355
Balick B., Frank A., 2002, ARA&A, 40, 439
c 0000 RAS, MNRAS 000, 000–000
17. Alignment of the Angular Momentum Vectors of Planetary Nebulae in the Galactic Bulge 17
Beaulieu S. F., Dopita M. A., Freeman K. C., 1999, ApJ,
515, 610
Bensby T. et al., 2010, A&A, 512, A41
Berens P., 2009, Journal of Statistical Software, 31, 1
Blackman E. G., 2009, in Strassmeier K. G., Kosovichev
A. G., Beckman J., eds., IAU Symposium, Vol. 259, Cos-
mic Magnetic Fields: from Planets, to Stars and Galaxies,
p. 35
Bogdan M., Bogdan K., Futschik A., 2002, Annals of the
Institute of Statistical Mathematics, 54, 29
Corradi R. L. M., Aznar R., Mampaso A., 1998, MNRAS,
297, 617
Corradi R. L. M., Schwarz H. E., 1995, A&A, 293, 871
de Marco O., 2009, PASP, 121, 316
Durand S., Acker A., Zijlstra A., 1998, A&AS, 132, 13
Efron B., 1979, The Annals of Statistics, 7, 1
Fisher N. I., 1995, Statistical Analysis of Circular Data.
Cambridge University Press, Cambridge
Gaensler B. M., 1998, ApJ, 493, 781
Gesicki K., Zijlstra A. A., 2007, A&A, 467, L29
Gesicki K., Zijlstra A. A., Acker A., G´orny S. K.,
Gozdziewski K., Walsh J. R., 2006, A&A, 451, 925
G´omez Y., Tafoya D., Anglada G., Miranda L. F., Torrelles
J. M., Patel N. A., Hern´andez R. F., 2009, ApJ, 695, 930
Gonzalez J.-F., Brilliant S., Pompei E., 2006, EMMI: The
ESO Multi-Mode Instrument, User’s Manual, 5th edn. Eu-
ropean Southern Observatory, doc. No. LSO-MAN-ESO-
40100-0001/5.3
Herwig F., 2005, ARA&A, 43, 435
Hoenen S., Gnaspini P., 1999, The Journal of Arachnology,
27, 159
Howard C. D. et al., 2009, ApJL, 702, L153
Jackson R. J., Jeffries R. D., 2010, MNRAS, 402, 1380
Jammalamadaka S. R., SenGupta A., 2001, Topics In Cir-
cular Statistics. World Scientific, Singapore
Maercker M. et al., 2012, Nature, 490, 232
Malaroda S., Levato H., Galliani S., 2006,
Stellar radial velocities bibliographic catalog;
from vizier service, cds, strasbourg, france.
http://cdsarc.u-strasbg.fr/viz-bin/VizieR?-meta.foot&-source=III/249
Matsumoto T., Nakazato T., Tomisaka K., 2006, ApJL,
637, L105
Melnick G., Harwit M., 1975, MNRAS, 171, 441
M´enard F., Duchˆene G., 2004, A&A, 425, 973
Minniti D., Zoccali M., 2008, in Bureau M., Athanassoula
E., Barbuy B., eds., IAU Symposium, Vol. 245, Formation
and Evolution of Galaxy Bulges, p. 323
Morris M., 1998, in Y. Sofue, ed., IAU Symposium, Vol.
184, The Central Regions of the Galaxy and Galaxies, p.
331
Nakamura F., Li Z.-Y., 2008, ApJ, 687, 354
Parker Q. A. et al., 2006, MNRAS, 373, 79
Protheroe R. J., 1985, in F. C. Jones, ed., International
Cosmic Ray Conference, Vol. 3, International Cosmic Ray
Conference, p. 485
Rich R. M., 2001, in von Hippel T., Simpson C., Manset
N., eds., Astronomical Society of the Pacific Conference
Series, Vol. 245, Astrophysical Ages and Times Scales, p.
216
Sabin L., Zijlstra A. A., Greaves J. S., 2007, MNRAS, 376,
378
Schwarz H. E., Monteiro H., Peterson R., 2008, ApJ, 675,
380
Shappee B. J., Thompson T. A., 2013, ApJ, 766, 64
Si´odmiak N., Tylenda R., 2001, A&A, 373, 1032
Soker N., 2006, PASP, 118, 260
Tang Y.-W., Ho P. T. P., Koch P. M., Girart J. M., Lai
S.-P., Rao R., 2009, ApJ, 700, 251
Testori J. C., Reich P., Reich W., 2008, A&A, 484, 733
van Winckel H., 2003, ARA&A, 41, 391
Vink J. S., Drew J. E., Harries T. J., Oudmaijer R. D.,
Unruh Y., 2005, MNRAS, 359, 1049
Vlemmings W. H. T., van Langevelde H. J., 2008, A&A,
488, 619
Weidmann W. A., D´ıaz R. J., 2008, PASP, 120, 380
Zijlstra A. A., 1990, A&A, 234, 387
Zijlstra A. A., 2007, Baltic Astronomy, 16, 79
c 0000 RAS, MNRAS 000, 000–000
18. arXiv:1307.5711v1[astro-ph.SR]22Jul2013 1
1 CONTOUR PLOTS
Figure 9. Greyscale images of the bipolar PNe, each overlaid with isophotes of its lobes together with lines indicating the measured PA
and its uncertainty. The images are in negative form and those observed using the NTT were deconvolved. The maximum isophote is
at 10 per cent of the peak PN intensity in the image and the isophotes are at 1 per cent intervals of that intensity. Each NTT plot has
North at the top and East at the left whereas the HST plots have their orientations marked on them. Tick marks on the plots are at 5
arcsec intervals. Scale bars are shown on those plots without tick marks.
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19. 2
Figure 9 – continued
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20. 3
Figure 9 – continued
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21. 4
Figure 9 – continued
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22. 5
Figure 9 – continued
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23. 6
Figure 9 – continued
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24. 7
Figure 9 – continued
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25. 8
Figure 9 – continued
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27. 10
−250 −200 −150 −100 −50 0 50 100 150 200
0
20
40
60
80
100
120
140
160
180
radial velocity / km s−1
GPA/°
polar
−200 −150 −100 −50 0 50 100 150 200 250
0
20
40
60
80
100
120
140
160
180
radial velocity / km s−1
GPA/°
non−polar
Figure 11. The GPA of the polar and non-polar PNe plotted against their Radial Velocities. The uncertainties forming the error bars
for the radial velocities are taken from the catalogues.
50 100 150
angle °
0.01
0.02
0.03
0.04
0.05
0.06
p
50 100 150
angle °
0.002
0.004
0.006
0.008
p
Figure 12. The histogram for the derived angles from the North Galactic Pole to the axes of the bipolar PNe is shown on the left. The
peaks correspond to the GPA. The angles on the Galactic Plane used to derive the angles from the North are shown in the histogram
on the right. Note the departure from uniformity in the distribution of those angles due to the constraints of the measured PN lengths,
the maximum PN length and the GPA. Note also that only a subset of those angles will apply to each PN. There are 440 000 entries
contributing to each histogram and the area of each histogram is 1.
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