Most stars form in multiple-star systems. For a better understanding of their formation processes, it is important to
resolve the individual protostellar components and the surrounding envelope and disk material at the earliest
possible formation epoch, because the formation history can be lost in a few orbital timescales. Here we present
Atacama Large Millimeter/submillimeter Array observational results of a young multiple protostellar system,
IRAS 04239+2436, where three well-developed large spiral arms were detected in the shocked SO emission.
Along the most conspicuous arm, the accretion streamer was also detected in the SO2 emission. The observational
results are complemented by numerical magnetohydrodynamic simulations, where those large arms only appear in
magnetically weakened clouds. Numerical simulations also suggest that the large triple spiral arms are the result of
gravitational interactions between compact triple protostars and the turbulent infalling envelope.
MUSE sneaks a peek at extreme ram-pressure stripping events. I. A kinematic s...Sérgio Sacani
- MUSE observations of the galaxy ESO137-001 reveal an extended gaseous tail over 30 kpc long traced by H-alpha emission, providing evidence of an extreme ram pressure stripping event as the galaxy falls into the massive Norma galaxy cluster.
- Analysis of the H-alpha kinematics and stellar velocity field show that ram pressure has removed the interstellar medium from the outer disk while the primary tail is still fed by gas from the galaxy center, with gravitational interactions not appearing to be the main mechanism of gas removal.
- The stripped gas retains evidence of the disk's rotational velocity out to around 20 kpc downstream, indicating the galaxy is moving radially along the plane of the sky, while
This document describes observations of the galaxy ESO137-001 using the MUSE instrument on the VLT. The key points are:
1) MUSE observations reveal an extended gas tail stretching over 30 kpc from the galaxy, tracing ongoing ram pressure stripping as it falls into the Norma galaxy cluster.
2) Analysis of the gas kinematics and stellar velocity field show that ram pressure has removed the interstellar medium from the outer disk while the primary tail is still fed by gas from the galaxy center.
3) The stripped gas retains evidence of the disk's rotational velocity out to 20 kpc downstream, indicating the galaxy is moving radially through the cluster. Beyond this the gas shows greater turbulence,
Dust-trapping Vortices and a Potentially Planet-triggered Spiral Wake in the ...Sérgio Sacani
The radial drift problem constitutes one of the most fundamental problems in planet formation theory, as it predicts
particles to drift into the star before they are able to grow to planetesimal size. Dust-trapping vortices have been
proposed as a possible solution to this problem, as they might be able to trap particles over millions of years,
allowing them to grow beyond the radial drift barrier. Here, we present ALMA 0 04 resolution imaging of the pretransitional
disk of V1247 Orionis that reveals an asymmetric ring as well as a sharply confined crescent structure,
resembling morphologies seen in theoretical models of vortex formation. The asymmetric ring (at 0 17 = 54 au
separation from the star) and the crescent (at 0 38 = 120 au) seem smoothly connected through a one-armed
spiral-arm structure that has been found previously in scattered light. We propose a physical scenario with a planet
orbiting at ∼0 3 ≈ 100 au, where the one-armed spiral arm detected in polarized light traces the accretion stream
feeding the protoplanet. The dynamical influence of the planet clears the gap between the ring and the crescent and
triggers two vortices that trap millimeter-sized particles, namely, the crescent and the bright asymmetry seen in the
ring. We conducted dedicated hydrodynamics simulations of a disk with an embedded planet, which results in
similar spiral-arm morphologies as seen in our scattered-light images. At the position of the spiral wake and the
crescent we also observe 12CO(3-2) and H12CO+ (4-3) excess line emission, likely tracing the increased scaleheight
in these disk regions.
Fleeting Small-scale Surface Magnetic Fields Build the Quiet-Sun CoronaSérgio Sacani
Arch-like loop structures filled with million Kelvin hot plasma form the building blocks of the quiet-Sun corona.
Both high-resolution observations and magnetoconvection simulations show the ubiquitous presence of magnetic
fields on the solar surface on small spatial scales of ∼100 km. However, the question of how exactly these quietSun coronal loops originate from the photosphere and how the magnetic energy from the surface is channeled to
heat the overlying atmosphere is a long-standing puzzle. Here we report high-resolution photospheric magnetic
field and coronal data acquired during the second science perihelion of Solar Orbiter that reveal a highly dynamic
magnetic landscape underlying the observed quiet-Sun corona. We found that coronal loops often connect to
surface regions that harbor fleeting weaker, mixed-polarity magnetic field patches structured on small spatial
scales, and that coronal disturbances could emerge from these areas. We suggest that weaker magnetic fields with
fluxes as low as 1015 Mx and/or those that evolve on timescales less than 5 minutes are crucial to understanding
the coronal structuring and dynamics.
The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with...Sérgio Sacani
The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with Blue Profiles
(ASSEMBLE) aims to investigate the process of mass assembly and its connection to high-mass star
formation theories in protoclusters in a dynamic view. We observed 11 massive (Mclump ≳ 103 M⊙),
luminous (Lbol ≳ 104 L⊙), and blue-profile (infall signature) clumps by ALMA with resolution of
∼2200–5500 au (median value of 3500 au) at 350 GHz (870 µm). 248 dense cores were identified, including 106 cores showing protostellar signatures and 142 prestellar core candidates. Compared to
early-stage infrared dark clouds (IRDCs) by ASHES, the core mass and surface density within the
ASSEMBLE clumps exhibited significant increment, suggesting concurrent core accretion during the
evolution of the clumps. The maximum mass of prestellar cores was found to be 2 times larger than
that in IRDCs, indicating that evolved protoclusters have the potential to harbor massive prestellar
cores. The mass relation between clumps and their most massive core (MMCs) is observed in ASSEMBLE but not in IRDCs, which is suggested to be regulated by multiscale mass accretion. The
mass correlation between the core clusters and their MMCs has a steeper slope compared to that
observed in stellar clusters, which can be due to fragmentation of the MMC and stellar multiplicity.
We observe a decrease in core separation and an increase in central concentration as protoclusters
evolve. We confirm primordial mass segregation in the ASSEMBLE protoclusters, possibly resulting
from gravitational concentration and/or gas accretion.
This document summarizes the results of a 180 ks Chandra-LETGS observation of Mrk 509 as part of a larger multi-wavelength campaign. The observation detected several absorption features in the X-ray spectrum originating from an ionized absorber, including ions with three distinct ionization degrees. The lowest ionized component is slightly redshifted and not in pressure equilibrium with the others, likely belonging to the host galaxy's interstellar medium. The other two components are outflowing at velocities of around -200 and -455 km/s. Simultaneous HST-COS observations detected 13 UV kinematic components, and at least three can be associated with the X-ray components, providing evidence that the UV and X-
The identification of_93_day_periodic_photometric_variability_for_yso_ylw_16aSérgio Sacani
This study identifies a 93 day periodic photometric variability in the Class I young stellar object (YSO) YLW 16A in the Rho Ophiuchus star forming region. Light curve analysis reveals variations of ~0.5 magnitudes in the Ks band over this period. The authors propose a triple system model consisting of an inner binary with a 93 day period eclipsed by a warped circumbinary disk, with a tertiary companion at ~40 AU responsible for warping the disk. This model is similar to one previously proposed for another YSO, WL 4, and may indicate such triple systems with eclipsing disks are common around young stars. Understanding these systems can provide insights into stellar and planetary formation and evolution.
Uma espetacular colisão de galáxias foi descoberta além da Via Láctea. O sistema mais próximo já descoberto, a identificação foi anunciada por uma equipe de astrônomos liderada pelo Professor Quentin Parker da Universidade de Hong Kong e pelo Professor Albert Zijlstra na Universidade de Manchester.
A galáxia está a 30 milhões de anos-luz de distância, o que significa que ela é relativamente próxima. Ela foi chamada de Roda de Kathryn, em homenagem à sua semelhança com o famoso fogo de artifício e também em homenagem à esposa do coautor do trabalho.
Esses sistemas são muito raros e nascem da colisão entre duas galáxias de tamanhos similares. As ondas de choque geradas na colisão comprimem o reservatório de gás em cada galáxia e disparam a formação de novas estrelas. Isso cria um espetacular anel de intensa emissão, e ilumina o sistema, do mesmo modo que a Roda Catherine ilumina a noite num show de fogos de artifício.
As galáxias crescem através de colisões, mas é raro registrar esse processo acontecendo, e é extremamente raro ver o anel da colisão em progresso. Pouco mais de 20 sistemas com anéis completos são conhecidos.
MUSE sneaks a peek at extreme ram-pressure stripping events. I. A kinematic s...Sérgio Sacani
- MUSE observations of the galaxy ESO137-001 reveal an extended gaseous tail over 30 kpc long traced by H-alpha emission, providing evidence of an extreme ram pressure stripping event as the galaxy falls into the massive Norma galaxy cluster.
- Analysis of the H-alpha kinematics and stellar velocity field show that ram pressure has removed the interstellar medium from the outer disk while the primary tail is still fed by gas from the galaxy center, with gravitational interactions not appearing to be the main mechanism of gas removal.
- The stripped gas retains evidence of the disk's rotational velocity out to around 20 kpc downstream, indicating the galaxy is moving radially along the plane of the sky, while
This document describes observations of the galaxy ESO137-001 using the MUSE instrument on the VLT. The key points are:
1) MUSE observations reveal an extended gas tail stretching over 30 kpc from the galaxy, tracing ongoing ram pressure stripping as it falls into the Norma galaxy cluster.
2) Analysis of the gas kinematics and stellar velocity field show that ram pressure has removed the interstellar medium from the outer disk while the primary tail is still fed by gas from the galaxy center.
3) The stripped gas retains evidence of the disk's rotational velocity out to 20 kpc downstream, indicating the galaxy is moving radially through the cluster. Beyond this the gas shows greater turbulence,
Dust-trapping Vortices and a Potentially Planet-triggered Spiral Wake in the ...Sérgio Sacani
The radial drift problem constitutes one of the most fundamental problems in planet formation theory, as it predicts
particles to drift into the star before they are able to grow to planetesimal size. Dust-trapping vortices have been
proposed as a possible solution to this problem, as they might be able to trap particles over millions of years,
allowing them to grow beyond the radial drift barrier. Here, we present ALMA 0 04 resolution imaging of the pretransitional
disk of V1247 Orionis that reveals an asymmetric ring as well as a sharply confined crescent structure,
resembling morphologies seen in theoretical models of vortex formation. The asymmetric ring (at 0 17 = 54 au
separation from the star) and the crescent (at 0 38 = 120 au) seem smoothly connected through a one-armed
spiral-arm structure that has been found previously in scattered light. We propose a physical scenario with a planet
orbiting at ∼0 3 ≈ 100 au, where the one-armed spiral arm detected in polarized light traces the accretion stream
feeding the protoplanet. The dynamical influence of the planet clears the gap between the ring and the crescent and
triggers two vortices that trap millimeter-sized particles, namely, the crescent and the bright asymmetry seen in the
ring. We conducted dedicated hydrodynamics simulations of a disk with an embedded planet, which results in
similar spiral-arm morphologies as seen in our scattered-light images. At the position of the spiral wake and the
crescent we also observe 12CO(3-2) and H12CO+ (4-3) excess line emission, likely tracing the increased scaleheight
in these disk regions.
Fleeting Small-scale Surface Magnetic Fields Build the Quiet-Sun CoronaSérgio Sacani
Arch-like loop structures filled with million Kelvin hot plasma form the building blocks of the quiet-Sun corona.
Both high-resolution observations and magnetoconvection simulations show the ubiquitous presence of magnetic
fields on the solar surface on small spatial scales of ∼100 km. However, the question of how exactly these quietSun coronal loops originate from the photosphere and how the magnetic energy from the surface is channeled to
heat the overlying atmosphere is a long-standing puzzle. Here we report high-resolution photospheric magnetic
field and coronal data acquired during the second science perihelion of Solar Orbiter that reveal a highly dynamic
magnetic landscape underlying the observed quiet-Sun corona. We found that coronal loops often connect to
surface regions that harbor fleeting weaker, mixed-polarity magnetic field patches structured on small spatial
scales, and that coronal disturbances could emerge from these areas. We suggest that weaker magnetic fields with
fluxes as low as 1015 Mx and/or those that evolve on timescales less than 5 minutes are crucial to understanding
the coronal structuring and dynamics.
The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with...Sérgio Sacani
The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with Blue Profiles
(ASSEMBLE) aims to investigate the process of mass assembly and its connection to high-mass star
formation theories in protoclusters in a dynamic view. We observed 11 massive (Mclump ≳ 103 M⊙),
luminous (Lbol ≳ 104 L⊙), and blue-profile (infall signature) clumps by ALMA with resolution of
∼2200–5500 au (median value of 3500 au) at 350 GHz (870 µm). 248 dense cores were identified, including 106 cores showing protostellar signatures and 142 prestellar core candidates. Compared to
early-stage infrared dark clouds (IRDCs) by ASHES, the core mass and surface density within the
ASSEMBLE clumps exhibited significant increment, suggesting concurrent core accretion during the
evolution of the clumps. The maximum mass of prestellar cores was found to be 2 times larger than
that in IRDCs, indicating that evolved protoclusters have the potential to harbor massive prestellar
cores. The mass relation between clumps and their most massive core (MMCs) is observed in ASSEMBLE but not in IRDCs, which is suggested to be regulated by multiscale mass accretion. The
mass correlation between the core clusters and their MMCs has a steeper slope compared to that
observed in stellar clusters, which can be due to fragmentation of the MMC and stellar multiplicity.
We observe a decrease in core separation and an increase in central concentration as protoclusters
evolve. We confirm primordial mass segregation in the ASSEMBLE protoclusters, possibly resulting
from gravitational concentration and/or gas accretion.
This document summarizes the results of a 180 ks Chandra-LETGS observation of Mrk 509 as part of a larger multi-wavelength campaign. The observation detected several absorption features in the X-ray spectrum originating from an ionized absorber, including ions with three distinct ionization degrees. The lowest ionized component is slightly redshifted and not in pressure equilibrium with the others, likely belonging to the host galaxy's interstellar medium. The other two components are outflowing at velocities of around -200 and -455 km/s. Simultaneous HST-COS observations detected 13 UV kinematic components, and at least three can be associated with the X-ray components, providing evidence that the UV and X-
The identification of_93_day_periodic_photometric_variability_for_yso_ylw_16aSérgio Sacani
This study identifies a 93 day periodic photometric variability in the Class I young stellar object (YSO) YLW 16A in the Rho Ophiuchus star forming region. Light curve analysis reveals variations of ~0.5 magnitudes in the Ks band over this period. The authors propose a triple system model consisting of an inner binary with a 93 day period eclipsed by a warped circumbinary disk, with a tertiary companion at ~40 AU responsible for warping the disk. This model is similar to one previously proposed for another YSO, WL 4, and may indicate such triple systems with eclipsing disks are common around young stars. Understanding these systems can provide insights into stellar and planetary formation and evolution.
Uma espetacular colisão de galáxias foi descoberta além da Via Láctea. O sistema mais próximo já descoberto, a identificação foi anunciada por uma equipe de astrônomos liderada pelo Professor Quentin Parker da Universidade de Hong Kong e pelo Professor Albert Zijlstra na Universidade de Manchester.
A galáxia está a 30 milhões de anos-luz de distância, o que significa que ela é relativamente próxima. Ela foi chamada de Roda de Kathryn, em homenagem à sua semelhança com o famoso fogo de artifício e também em homenagem à esposa do coautor do trabalho.
Esses sistemas são muito raros e nascem da colisão entre duas galáxias de tamanhos similares. As ondas de choque geradas na colisão comprimem o reservatório de gás em cada galáxia e disparam a formação de novas estrelas. Isso cria um espetacular anel de intensa emissão, e ilumina o sistema, do mesmo modo que a Roda Catherine ilumina a noite num show de fogos de artifício.
As galáxias crescem através de colisões, mas é raro registrar esse processo acontecendo, e é extremamente raro ver o anel da colisão em progresso. Pouco mais de 20 sistemas com anéis completos são conhecidos.
The xmm newton-view_of_the_central_degrees_of_the_milk_waySérgio Sacani
Novas imagens do Observatório de Raios-X XMM-Newton da ESA revelaram alguns dos processos mais intensos que acontecem no coração da nossa Via Láctea.
As fontes brilhantes e pontuais que se destacam por toda imagem indicam os sistemas estelares binários onde uma das estrelas atingiu o final de sua vida, desenvolvendo para um objeto compacto e denso – uma estrela de nêutrons ou um buraco negro.
A região central da Via Láctea também contém jovens estrelas e aglomerados estelares e algumas dessas fontes são visíveis como pontos brancos e vermelhos brilhando na imagem, que se espalha por 1000 anos-luz.
A maior parte da ação ocorre no centro, onde nuvens difusas de gás estão sendo cavadas por ventos poderosos soprados por estrelas jovens, bem como por supernovas.
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
A High-mass, Young Star-forming Core Escaping from Its Parental FilamentSérgio Sacani
We studied the unique kinematic properties in massive filament G352.63-1.07 at 103 au spatial scale with the dense
molecular tracers observed with the Atacama Large Millimeter/submillimeter Array. We find the central massive
core M1 (12 Me) being separated from the surrounding filament with a velocity difference of
- =- - v vsys 2 km s 1 and a transverse separation within 3″. Meanwhile, as shown in multiple dense-gas
tracers, M1 has a spatial extension closely aligned with the main filament and is connected to the filament toward
both its ends. M1 thus represents a very beginning state for a massive, young star-forming core escaping from the
parental filament, within a timescale of ∼4000 yr. Based on its kinetic energy (3.5 × 1044 erg), the core escape is
unlikely solely due to the original filament motion or magnetic field but requires more energetic events such as a
rapid intense anisotropic collapse. The released energy also seems to noticeably increase the environmental
turbulence. This may help the filament to become stabilized again.
The wonderful complexity_of_the_mira_ab_systemSérgio Sacani
The ALMA observations of the Mira AB binary system reveal an amazingly complex circumstellar environment shaped by multiple dynamical processes. In the blue wing of the CO emission line, opposing large arcs form a bubble structure around Mira A, possibly created by the wind from Mira B blowing into Mira A's expanding envelope. In the main line component, spiral arcs are seen around Mira A that appear relatively flat and oriented in the orbital plane. An accretion wake is also visible trailing Mira B. The companion is marginally resolved with a separation of 0.487 arcseconds from Mira A.
Alma observations of_the_hh46_47_molecular_outflowSérgio Sacani
ALMA observations of the HH 46/47 molecular outflow reveal striking differences between the blue and red lobes. The blue lobe morphology and kinematics are consistent with entrainment by a wide-angle wind, while the red lobe shows a more complex structure with evidence of entrainment by both a wide-angle wind and collimated episodic winds. Three major clumps along the red lobe axis have velocity distributions consistent with prompt entrainment by periodic mass ejection episodes occurring every few hundred years. Position-velocity cuts show velocity gradients increasing toward the outflow axis, inconsistent with outflow rotation.
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.
This document summarizes a study that identified 195 compact elliptical galaxies across different environments using data from optical and ultraviolet sky surveys. The researchers constructed the sample by selecting galaxies that were outliers from the universal color-magnitude relation and had small sizes and high stellar velocity dispersions based on spectral modeling. They found that 7 of the galaxies were isolated, not belonging to any known galaxy groups. For these isolated galaxies, the researchers identified possible host galaxies located up to 3.3 Mpc away. The stellar populations of the isolated compact elliptical galaxies were found to be similar to those in galaxy groups and clusters, suggesting a common formation mechanism.
Galaxy growth in a massive halo in the first billion years of cosmic historySérgio Sacani
According to the current understanding of cosmic structure formation, the precursors of the most massive structures in the Universe began to form shortly after the Big Bang, in regions corresponding to the largest fluctuations in the cosmic density field1–3. Observing these structures during their period of active growth and assembly—the first few hundred million years of the Universe—is challenging because it requires surveys that are sensitive enough to detect the distant galaxies that act as signposts for these structures and wide enough to capture the rarest objects. As a result, very few such objects have been detected so far4,5. Here we report observations of a far-infrared-luminous object at redshift 6.900 (less than 800 million years after the Big Bang) that was discovered in a wide-field survey6. High-resolution imaging shows it to be a pair of extremely massive star-forming galaxies. The larger is forming stars at a rate of 2,900 solar masses per year, contains 270 billion solar masses of gas and 2.5 billion solar masses of dust, and is more massive than any other known object at a redshift of more than 6. Its rapid star formation is probably triggered by its companion galaxy at a projected separation of 8 kiloparsecs. This merging companion hosts 35 billion solar masses of stars and has a star-formation rate of 540 solar masses per year, but has an order of magnitude less gas and dust than its neighbour and physical conditions akin to those observed in lower-metallicity galaxies in the nearby Universe7. These objects suggest the presence of a dark-matter halo with a mass of more than 100 billion solar masses, making it among the rarest dark-matter haloes that should exist in the Universe at this epoch.
The Expansion of the X-Ray Nebula Around η CarSérgio Sacani
1. The author analyzes over 20 years of Chandra X-ray images to measure for the first time the expansion of the X-ray nebula around η Carinae.
2. A combined Chandra image reveals a faint, nearly uniform elliptical shell surrounding the X-ray bright ring, with a similar orientation and shape as the Homunculus nebula but about 3 times larger.
3. The author measures proper motions of brighter regions associated with the X-ray emitting ring, such as the S-ridge and W-arc. Motions are consistent with optical studies of ejecta from the 1840s Great Eruption.
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
This document summarizes a 1.3 mm continuum survey of protoplanetary disks in the 2-3 Myr old IC348 star cluster using the Submillimeter Array. 10 disks out of 85 young stars were detected with masses ranging from 2-6 Jupiter masses. This distribution is shifted to lower masses by a factor of 20 compared to younger regions like Taurus and Ophiuchus. The results reveal a rapid decline in the number of small dust grains in disks after 1 Myr, likely due to grain growth. The few detected disks may be the best candidates in IC348 to study planet formation.
Kinematics and simulations_of_the_stellar_stream_in_the_halo_of_the_umbrella_...Sérgio Sacani
This document summarizes a study of the stellar stream and substructures around the Umbrella Galaxy (NGC 4651). Deep imaging and spectroscopy were used to characterize the properties and kinematics of the stream. Tracer objects like globular clusters and planetary nebulae were identified and found to delineate a kinematically cold feature in position-velocity space. Dynamical modeling suggests the stream originated from the tidal disruption of a dwarf galaxy on a highly eccentric orbit about 6-10 billion years ago. This work demonstrates the feasibility of using discrete tracers to recover the kinematics and model the dynamics of low surface brightness stellar streams around distant galaxies.
Creation of cosmic structure in the complex galaxy cluster merger abell 2744Sérgio Sacani
Abell 2744 is one of the most actively merging galaxy clusters known, appearing to have "dark", "ghost", "bullet", and "stripped" substructures of around 1014 solar masses each. The cluster shows a complex phenomenology that will challenge simulations to reproduce. The authors present a detailed strong lensing, weak lensing, and X-ray analysis of Abell 2744, identifying 34 strongly lensed images around the massive Southern core and producing the most detailed mass map to date. They find evidence that the Southern core and Northwestern substructure are post-merger systems similar to the Bullet Cluster viewed from an angle, and derive a new constraint on the self-interaction cross section of dark matter particles. They
AT2023fhn (the Finch): a Luminous Fast Blue Optical Transient at a large offs...Sérgio Sacani
Luminous Fast Blue Optical Transients (LFBOTs) - the prototypical example being AT 2018cow - are a rare class of events
whose origins are poorly understood. They are characterised by rapid evolution, featureless blue spectra at early times, and
luminous X-ray and radio emission. LFBOTs thus far have been found exclusively at small projected offsets from star-forming
host galaxies. We present Hubble Space Telescope, Gemini, Chandra and Very Large Array observations of a new LFBOT,
AT 2023fhn. The Hubble Space Telescope data reveal a large offset (> 3.5 half-light radii) from the two closest galaxies, both
at redshift 𝑧 ∼ 0.24. The location of AT 2023fhn is in stark contrast with previous events, and demonstrates that LFBOTs can
occur in a range of galactic environments.
This document presents a multiwavelength analysis of the merging galaxy cluster MACS J0416.1-2403 using observations from Chandra, JVLA, GMRT, and Hubble Space Telescope. The cluster consists of two main subclusters, NE and SW, separated by about 250 kpc. Chandra observations reveal the NE subcluster has a compact core and X-ray cavity, but is not a cool core. A density discontinuity is detected about 450 kpc southwest of the SW subcluster, likely caused by an interaction with a less massive structure detected in lensing maps. For both subclusters, the dark matter and gas components are well-aligned, suggesting MACS J0416.1-2403
A measurement of_the_black_hole_mass_in_ngc_1097_using_almaSérgio Sacani
Artigo descreve a maneira como os astrônomos usaram pela primeira vez o ALMA para medir a massa de um buraco negro supermassivo no interior de uma galáxias espiral barrada.
X-RAY MEASUREMENTS OF THE PARTICLE ACCELERATION PROPERTIES AT INWARD SHOCKS I...Sérgio Sacani
We present new evidence that the bright non-thermal X-ray emission features in the interior of the Cassiopeia A
supernova remnant (SNR) are caused by inward moving shocks based on Chandra and NuSTAR observations. Several
bright inward-moving filaments were identified using monitoring data taken by Chandra in 2000–2014. These inwardmoving shock locations are nearly coincident with hard X-ray (15–40 keV) hot spots seen by NuSTAR. From proper
motion measurements, the transverse velocities were estimated to be in the range ∼2,100–3,800 km s−1
for a distance of
3.4 kpc. The shock velocities in the frame of the expanding ejecta reach values of ∼5,100–8,700 km s−1
, slightly higher
than the typical speed of the forward shock. Additionally, we find flux variations (both increasing and decreasing) on
timescales of a few years in some of the inward-moving shock filaments. The rapid variability timescales are consistent
with an amplified magnetic field of B ∼ 0.5–1 mG. The high speed and low photon cut-off energy of the inward-moving
shocks are shown to imply a particle diffusion coefficient that departs from the Bohm regime (k0 = D0/D0,Bohm ∼ 3–8)
for the few simple physical configurations we consider in this study. The maximum electron energy at these shocks is
estimated to be ∼8–11 TeV, smaller than the values of ∼15–34 TeV inferred for the forward shock. Cassiopeia A is
dynamically too young for its reverse shock to appear to be moving inward in the observer frame. We propose instead
that the inward-moving shocks are a consequence of the forward shock encountering a density jump of & 5–8 in the
surrounding material.
Evidence for a_complex_enrichment_history_of_the_stream_from_fairall_9_sightlineSérgio Sacani
This study analyzes absorption spectra of the Magellanic Stream (MS) toward the quasar Fairall 9, obtained using the Hubble Space Telescope Cosmic Origins Spectrograph (HST/COS) and the Very Large Telescope Ultraviolet and Visible Echelle Spectrograph (VLT/UVES). The spectra reveal absorption from multiple velocity components of the MS, indicating multiphase gas. Surprisingly, the sulfur abundance is found to be high ([S/H] = -0.30), five times higher than other MS sightlines, while the nitrogen abundance is lower ([N/H] = -1.15). This points to a complex enrichment history, where the gas toward Fair
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.
More Related Content
Similar to Triple Spiral Arms of a Triple Protostar System Imaged in Molecular Lines
The xmm newton-view_of_the_central_degrees_of_the_milk_waySérgio Sacani
Novas imagens do Observatório de Raios-X XMM-Newton da ESA revelaram alguns dos processos mais intensos que acontecem no coração da nossa Via Láctea.
As fontes brilhantes e pontuais que se destacam por toda imagem indicam os sistemas estelares binários onde uma das estrelas atingiu o final de sua vida, desenvolvendo para um objeto compacto e denso – uma estrela de nêutrons ou um buraco negro.
A região central da Via Láctea também contém jovens estrelas e aglomerados estelares e algumas dessas fontes são visíveis como pontos brancos e vermelhos brilhando na imagem, que se espalha por 1000 anos-luz.
A maior parte da ação ocorre no centro, onde nuvens difusas de gás estão sendo cavadas por ventos poderosos soprados por estrelas jovens, bem como por supernovas.
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
A High-mass, Young Star-forming Core Escaping from Its Parental FilamentSérgio Sacani
We studied the unique kinematic properties in massive filament G352.63-1.07 at 103 au spatial scale with the dense
molecular tracers observed with the Atacama Large Millimeter/submillimeter Array. We find the central massive
core M1 (12 Me) being separated from the surrounding filament with a velocity difference of
- =- - v vsys 2 km s 1 and a transverse separation within 3″. Meanwhile, as shown in multiple dense-gas
tracers, M1 has a spatial extension closely aligned with the main filament and is connected to the filament toward
both its ends. M1 thus represents a very beginning state for a massive, young star-forming core escaping from the
parental filament, within a timescale of ∼4000 yr. Based on its kinetic energy (3.5 × 1044 erg), the core escape is
unlikely solely due to the original filament motion or magnetic field but requires more energetic events such as a
rapid intense anisotropic collapse. The released energy also seems to noticeably increase the environmental
turbulence. This may help the filament to become stabilized again.
The wonderful complexity_of_the_mira_ab_systemSérgio Sacani
The ALMA observations of the Mira AB binary system reveal an amazingly complex circumstellar environment shaped by multiple dynamical processes. In the blue wing of the CO emission line, opposing large arcs form a bubble structure around Mira A, possibly created by the wind from Mira B blowing into Mira A's expanding envelope. In the main line component, spiral arcs are seen around Mira A that appear relatively flat and oriented in the orbital plane. An accretion wake is also visible trailing Mira B. The companion is marginally resolved with a separation of 0.487 arcseconds from Mira A.
Alma observations of_the_hh46_47_molecular_outflowSérgio Sacani
ALMA observations of the HH 46/47 molecular outflow reveal striking differences between the blue and red lobes. The blue lobe morphology and kinematics are consistent with entrainment by a wide-angle wind, while the red lobe shows a more complex structure with evidence of entrainment by both a wide-angle wind and collimated episodic winds. Three major clumps along the red lobe axis have velocity distributions consistent with prompt entrainment by periodic mass ejection episodes occurring every few hundred years. Position-velocity cuts show velocity gradients increasing toward the outflow axis, inconsistent with outflow rotation.
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.
This document summarizes a study that identified 195 compact elliptical galaxies across different environments using data from optical and ultraviolet sky surveys. The researchers constructed the sample by selecting galaxies that were outliers from the universal color-magnitude relation and had small sizes and high stellar velocity dispersions based on spectral modeling. They found that 7 of the galaxies were isolated, not belonging to any known galaxy groups. For these isolated galaxies, the researchers identified possible host galaxies located up to 3.3 Mpc away. The stellar populations of the isolated compact elliptical galaxies were found to be similar to those in galaxy groups and clusters, suggesting a common formation mechanism.
Galaxy growth in a massive halo in the first billion years of cosmic historySérgio Sacani
According to the current understanding of cosmic structure formation, the precursors of the most massive structures in the Universe began to form shortly after the Big Bang, in regions corresponding to the largest fluctuations in the cosmic density field1–3. Observing these structures during their period of active growth and assembly—the first few hundred million years of the Universe—is challenging because it requires surveys that are sensitive enough to detect the distant galaxies that act as signposts for these structures and wide enough to capture the rarest objects. As a result, very few such objects have been detected so far4,5. Here we report observations of a far-infrared-luminous object at redshift 6.900 (less than 800 million years after the Big Bang) that was discovered in a wide-field survey6. High-resolution imaging shows it to be a pair of extremely massive star-forming galaxies. The larger is forming stars at a rate of 2,900 solar masses per year, contains 270 billion solar masses of gas and 2.5 billion solar masses of dust, and is more massive than any other known object at a redshift of more than 6. Its rapid star formation is probably triggered by its companion galaxy at a projected separation of 8 kiloparsecs. This merging companion hosts 35 billion solar masses of stars and has a star-formation rate of 540 solar masses per year, but has an order of magnitude less gas and dust than its neighbour and physical conditions akin to those observed in lower-metallicity galaxies in the nearby Universe7. These objects suggest the presence of a dark-matter halo with a mass of more than 100 billion solar masses, making it among the rarest dark-matter haloes that should exist in the Universe at this epoch.
The Expansion of the X-Ray Nebula Around η CarSérgio Sacani
1. The author analyzes over 20 years of Chandra X-ray images to measure for the first time the expansion of the X-ray nebula around η Carinae.
2. A combined Chandra image reveals a faint, nearly uniform elliptical shell surrounding the X-ray bright ring, with a similar orientation and shape as the Homunculus nebula but about 3 times larger.
3. The author measures proper motions of brighter regions associated with the X-ray emitting ring, such as the S-ridge and W-arc. Motions are consistent with optical studies of ejecta from the 1840s Great Eruption.
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
This document summarizes a 1.3 mm continuum survey of protoplanetary disks in the 2-3 Myr old IC348 star cluster using the Submillimeter Array. 10 disks out of 85 young stars were detected with masses ranging from 2-6 Jupiter masses. This distribution is shifted to lower masses by a factor of 20 compared to younger regions like Taurus and Ophiuchus. The results reveal a rapid decline in the number of small dust grains in disks after 1 Myr, likely due to grain growth. The few detected disks may be the best candidates in IC348 to study planet formation.
Kinematics and simulations_of_the_stellar_stream_in_the_halo_of_the_umbrella_...Sérgio Sacani
This document summarizes a study of the stellar stream and substructures around the Umbrella Galaxy (NGC 4651). Deep imaging and spectroscopy were used to characterize the properties and kinematics of the stream. Tracer objects like globular clusters and planetary nebulae were identified and found to delineate a kinematically cold feature in position-velocity space. Dynamical modeling suggests the stream originated from the tidal disruption of a dwarf galaxy on a highly eccentric orbit about 6-10 billion years ago. This work demonstrates the feasibility of using discrete tracers to recover the kinematics and model the dynamics of low surface brightness stellar streams around distant galaxies.
Creation of cosmic structure in the complex galaxy cluster merger abell 2744Sérgio Sacani
Abell 2744 is one of the most actively merging galaxy clusters known, appearing to have "dark", "ghost", "bullet", and "stripped" substructures of around 1014 solar masses each. The cluster shows a complex phenomenology that will challenge simulations to reproduce. The authors present a detailed strong lensing, weak lensing, and X-ray analysis of Abell 2744, identifying 34 strongly lensed images around the massive Southern core and producing the most detailed mass map to date. They find evidence that the Southern core and Northwestern substructure are post-merger systems similar to the Bullet Cluster viewed from an angle, and derive a new constraint on the self-interaction cross section of dark matter particles. They
AT2023fhn (the Finch): a Luminous Fast Blue Optical Transient at a large offs...Sérgio Sacani
Luminous Fast Blue Optical Transients (LFBOTs) - the prototypical example being AT 2018cow - are a rare class of events
whose origins are poorly understood. They are characterised by rapid evolution, featureless blue spectra at early times, and
luminous X-ray and radio emission. LFBOTs thus far have been found exclusively at small projected offsets from star-forming
host galaxies. We present Hubble Space Telescope, Gemini, Chandra and Very Large Array observations of a new LFBOT,
AT 2023fhn. The Hubble Space Telescope data reveal a large offset (> 3.5 half-light radii) from the two closest galaxies, both
at redshift 𝑧 ∼ 0.24. The location of AT 2023fhn is in stark contrast with previous events, and demonstrates that LFBOTs can
occur in a range of galactic environments.
This document presents a multiwavelength analysis of the merging galaxy cluster MACS J0416.1-2403 using observations from Chandra, JVLA, GMRT, and Hubble Space Telescope. The cluster consists of two main subclusters, NE and SW, separated by about 250 kpc. Chandra observations reveal the NE subcluster has a compact core and X-ray cavity, but is not a cool core. A density discontinuity is detected about 450 kpc southwest of the SW subcluster, likely caused by an interaction with a less massive structure detected in lensing maps. For both subclusters, the dark matter and gas components are well-aligned, suggesting MACS J0416.1-2403
A measurement of_the_black_hole_mass_in_ngc_1097_using_almaSérgio Sacani
Artigo descreve a maneira como os astrônomos usaram pela primeira vez o ALMA para medir a massa de um buraco negro supermassivo no interior de uma galáxias espiral barrada.
X-RAY MEASUREMENTS OF THE PARTICLE ACCELERATION PROPERTIES AT INWARD SHOCKS I...Sérgio Sacani
We present new evidence that the bright non-thermal X-ray emission features in the interior of the Cassiopeia A
supernova remnant (SNR) are caused by inward moving shocks based on Chandra and NuSTAR observations. Several
bright inward-moving filaments were identified using monitoring data taken by Chandra in 2000–2014. These inwardmoving shock locations are nearly coincident with hard X-ray (15–40 keV) hot spots seen by NuSTAR. From proper
motion measurements, the transverse velocities were estimated to be in the range ∼2,100–3,800 km s−1
for a distance of
3.4 kpc. The shock velocities in the frame of the expanding ejecta reach values of ∼5,100–8,700 km s−1
, slightly higher
than the typical speed of the forward shock. Additionally, we find flux variations (both increasing and decreasing) on
timescales of a few years in some of the inward-moving shock filaments. The rapid variability timescales are consistent
with an amplified magnetic field of B ∼ 0.5–1 mG. The high speed and low photon cut-off energy of the inward-moving
shocks are shown to imply a particle diffusion coefficient that departs from the Bohm regime (k0 = D0/D0,Bohm ∼ 3–8)
for the few simple physical configurations we consider in this study. The maximum electron energy at these shocks is
estimated to be ∼8–11 TeV, smaller than the values of ∼15–34 TeV inferred for the forward shock. Cassiopeia A is
dynamically too young for its reverse shock to appear to be moving inward in the observer frame. We propose instead
that the inward-moving shocks are a consequence of the forward shock encountering a density jump of & 5–8 in the
surrounding material.
Evidence for a_complex_enrichment_history_of_the_stream_from_fairall_9_sightlineSérgio Sacani
This study analyzes absorption spectra of the Magellanic Stream (MS) toward the quasar Fairall 9, obtained using the Hubble Space Telescope Cosmic Origins Spectrograph (HST/COS) and the Very Large Telescope Ultraviolet and Visible Echelle Spectrograph (VLT/UVES). The spectra reveal absorption from multiple velocity components of the MS, indicating multiphase gas. Surprisingly, the sulfur abundance is found to be high ([S/H] = -0.30), five times higher than other MS sightlines, while the nitrogen abundance is lower ([N/H] = -1.15). This points to a complex enrichment history, where the gas toward Fair
Similar to Triple Spiral Arms of a Triple Protostar System Imaged in Molecular Lines (20)
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.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
ESR spectroscopy in liquid food and beverages.pptxPRIYANKA PATEL
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
Travis Hills of MN is Making Clean Water Accessible to All Through High Flux ...Travis Hills MN
By harnessing the power of High Flux Vacuum Membrane Distillation, Travis Hills from MN envisions a future where clean and safe drinking water is accessible to all, regardless of geographical location or economic status.
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...Scintica Instrumentation
Targeting Hsp90 and its pathogen Orthologs with Tethered Inhibitors as a Diagnostic and Therapeutic Strategy for cancer and infectious diseases with Dr. Timothy Haystead.
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
Current Ms word generated power point presentation covers major details about the micronuclei test. It's significance and assays to conduct it. It is used to detect the micronuclei formation inside the cells of nearly every multicellular organism. It's formation takes place during chromosomal sepration at metaphase.
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdfSelcen Ozturkcan
Ozturkcan, S., Berndt, A., & Angelakis, A. (2024). Mending clothing to support sustainable fashion. Presented at the 31st Annual Conference by the Consortium for International Marketing Research (CIMaR), 10-13 Jun 2024, University of Gävle, Sweden.
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
The cost of acquiring information by natural selectionCarl Bergstrom
This is a short talk that I gave at the Banff International Research Station workshop on Modeling and Theory in Population Biology. The idea is to try to understand how the burden of natural selection relates to the amount of information that selection puts into the genome.
It's based on the first part of this research paper:
The cost of information acquisition by natural selection
Ryan Seamus McGee, Olivia Kosterlitz, Artem Kaznatcheev, Benjamin Kerr, Carl T. Bergstrom
bioRxiv 2022.07.02.498577; doi: https://doi.org/10.1101/2022.07.02.498577
2. and its comparisons with numerical simulations (Section 3).
We discuss the effect of the magnetic field on multiple
formation and the implications of close multiple protostars for
planet formation in Section 4, and the final conclusion is given
in Section 5.
2. ALMA Observations and Results
IRAS 04239+2436 was observed using ALMA during
Cycle 3 (2015.1.00397.S; PI: Jeong-Eun Lee) on 2016 August
16 UT. Five spectral windows in Band 7 were set to cover
several molecular lines, such as SO 88–77 (344.31061200
GHz), HCN 4–3 (354.50547590 GHz), HCO+
4–3
(356.73422300 GHz), and SO2 104,6–103,7 (356.75518930
GHz).10
The source velocity was VLSR = 6.5 km s−1
(Fuller &
Ladd 2002). The bandwidths and spectral resolutions were
117.19 MHz and 122.070 kHz (∼0.1 km s−1
) for the SO line
and 468.75 MHz and 244.141 kHz (∼0.2 km s−1
) for the other
three. 40 12 m antennas were used in the C40-4 configuration,
with baselines in the range from 21.4 m to 3.1 km. The total
observing time on source was 29.8 minutes.
The data were initially calibrated using the CASA 4.7.0
pipeline (McMullin et al. 2007). The nearby quasar J0510
+1800 was used as a bandpass and phase calibrator, and the
quasar J0238+1636 was used as an amplitude calibrator. Self-
calibration was applied for better imaging. The continuum
image with Briggs weighting (robust = 0.5) is used for the self-
calibration. Two phase calibrations with “inf” and “60 s”
intervals are applied, which increases the signal-to-noise ratio
of the continuum image by a factor of 5. The molecular line
images were produced by the clean task within CASA with
natural weighting. The synthesized beams are 0 184 × 0 119,
0 201 × 0 124, 0 180 × 0 119, and 0 202 × 0 125,
respectively, for SO, SO2, HCN, and HCO+
, with position
angles (PAs) of 10°
.1, 19°
.5, 11°
.4, and 19°
.5. The rms noise
levels (σ) for the SO, SO2, HCN, and HCO+
images are 3.5,
4.45, 4.15, and 4.17 mJy beam−1
, respectively. The moment
maps of the molecular lines were generated by the immoments
task using a threshold of 6σ. The continuum image was
produced by using line-free channels with uniform weighting.
The synthesized beam is 0 14 × 0 08, with a PA of 4°
.3, and
the rms noise level is 0.15 mJy beam−1
.
The ALMA observation (Figures 1, 2, and 3) of IRAS 04239
+2436 reveals two compact continuum sources corresponding
to Sources A and B, without any continuum emission
associated with the circumbinary material or beyond the
circumbinary scale (∼100 au). Unlike the continuum image,
the molecular line emission shows an extended gas structure up
to 400 au; the HCO+
emission distributes mainly along the
bipolar outflow cavities (see Figure 4), while the SO line
emission distributes along several arm structures (Figures 1 and
3). The most prominent features are the large extended (∼400
au) multiple-arm (at least three) structures traced by the SO line
emission. In contrast, the HCN and SO2 emissions are detected
only toward Source B (Figure 2), which is known as a
secondary in the NIR images.
The large SO molecular spiral arms probably connect the
envelope directly to the circumstellar disks around each stellar
component. The arms can be developed by the gravitational
torque induced by the dynamical interactions of the binary or
multiple protostars (Offner et al. 2010; Matsumoto et al.
2015b). This dynamical process generates shocks, and
molecular gas can be excited by shocks to produce detectable
emission along spiral arms. A recent study of the sulfur
chemistry induced by the accretion shocks (van Gelder et al.
2021) demonstrated that even a low shock velocity (∼3 km
s−1
) in dense (n ∼ 107
cm−3
) gas can greatly enhance the
abundances of SO and SO2 via the chemical process initiated
by the desorption of CH4. In the physical conditions developed
by low-velocity shocks, H2S or OCS can also be sublimated
from grain surfaces and subsequently react with H, OH, and O2
to form SO (Millar 1993; Esplugues et al. 2014). Therefore, the
SO emission detected along the large arm structures in IRAS
Figure 1. The SO integrated intensity (a) and velocity dispersion (b) maps. The white (a) and black (b) contours depict the continuum emission distribution. The
ellipse in the lower left corner represents the beam size. The contour levels and the beam size of the continuum image are the same in all figures. The SO integrated
intensity map shows a strong flow-like structure toward Source B, and the velocity dispersion also increases toward Source B. The individual line profiles can be found
in Figure 3; the SO lines around Source B are very broad, while the line intensity itself peaks at the flow-like structure beneath Source B. The integrated intensity is
proportional to the column density multiplied by the excitation temperature in the molecular gas, and thus it increases rapidly toward the central source. The peak
intensity of the SO line is more sensitive to the excitation temperature of the molecule, so it better traces the shocked gas along the spiral arms, as presented in
Figure 12(a).
10
The molecular line information is adopted from the Cologne Database for
Molecular Spectroscopy (Müller et al. 2005) and the Jet Propulsion Laboratory
(Pickett et al. 1998) molecular databases.
2
The Astrophysical Journal, 953:82 (13pp), 2023 August 10 Lee et al.
3. 04239+2436 is likely originated by shocks generated by
gravitational interaction between the infalling envelope and the
orbital motion of the triple system (see Section 3). In contrast,
the large dusty arms are not detected around IRAS 04239
+2436, probably because of the low dust column density along
the spiral arms at scales of several hundreds of astronomical
units in the envelope.
3. Numerical Simulations
The arm structures confined within dense circumbinary disks
toward several binary or multiple systems have been detected
in the dust continuum (Alves et al. 2019; Diaz-Rodriguez et al.
2022). Theoretical simulations (Bate & Bonnell 1997; Matsu-
moto et al. 2019b) of a binary system interacting only with a
circumbinary disk have shown that two main arms, one of
which is connected to each stellar component, are developed,
with the secondary component accreting more mass to result in
an equal-mass binary at the end. However, IRAS 04239+2436
is likely a triple protostellar system that presents very clear
triple arms. In fact, the spiral arms developed by triples in a
turbulent envelope (Matsumoto et al. 2015b) have more
branches with diverse curvatures compared to the spiral arms
developed inside the circumbinary disk (Matsumoto et al.
2019b). Therefore, in order to explain the observed multiple-
arm structures in IRAS 04239+2436, we have reanalyzed a
hydrodynamic (HD) simulation of a fragmenting turbulent
filamentary cloud that forms a multiple stellar system
(Matsumoto et al. 2015b). The adaptive mesh refinement
(AMR) technique can zoom into one core where multiple
protostars are forming (Figure 5).
As an initial condition of the simulation, we consider a
filamentary cloud in an equilibrium state, in which the thermal
pressure supports the cloud against self-gravity in the
computational domain of (1.56 pc)3
. When we assume
isothermal gas of T = 10 K and an infinite cloud length, the
density distribution is given by R R R
1
0 0
2 2
( ) [ ( ) ]
/
r r
= + -
(Stodólkiewicz 1963; Ostriker 1964), where R denotes the
cylindrical radius. The scale height of the filament, R0 =
0.05 pc, is chosen based on the observation from the Hershel
survey of the filamentary cloud (Arzoumanian et al. 2011).
The density on the filamentary axis is given by
c GR
2 1.45 10 g cm
s
0
2
0
2 19 3
( )
r p
= = ´ - -
(the corresp-
onding number density is n0 = 3.79 × 104
cm−3
), where the
isothermal sound speed is cs = 0.19 km s−1
for gas of 10 K. We
impose turbulence with a power spectrum of P(k) ∝ k−4
as the
initial condition, according to the observed size–linewidth
relation of σ(λ) ∝ λ1/2
(Larson 1981), where k, σ, and λ are a
wavenumber, the line width, and the length scale, respectively.
The average Mach number of turbulence over the computa-
tional domain is unity.
Figure 2. The peak intensity map and the intensity-weighted velocity map of HCN J = 4–3 ((a) and (b)) and SO2 ((c) and (d)). The maps were generated using a
threshold of 6σ (0.024 and 0.03 Jy beam−1
for HCN and SO2, respectively). The contours show the continuum emission at 857 μm. The HCN emission appears only
in Source B. The SO2 emission traces the accreting gas toward Source B. The ellipse in the upper left corner represents the beam size.
3
The Astrophysical Journal, 953:82 (13pp), 2023 August 10 Lee et al.
4. The calculation was performed by the AMR code SFU-
MATO (Matsumoto 2007), assuming the barotropic equation
of state, P c 1
s
2
cr
7 5
( ) [ ( ) ]
r r r r
= + , where the critical density
is set at ρcr = 10−13
g cm−3
(Masunaga et al. 1998). The self-
gravity of the gas is taken into account, and the magnetic fields
are ignored for the HD simulations. Using the AMR technique,
the grid is refined during the course of the calculation, so that
the Jeans length of a dense region is resolved by at least eight
cells (Truelove et al. 1997). In order to mimic protostar
formation, a sink particle is introduced where the density
reaches ρsink = 10−11
g cm−3
and several conditions for particle
creation are satisfied (Matsumoto et al. 2015a). Each sink
particle accretes the gas around it within the sink radius,
2.45 au, increasing the mass.
The evolution of the cloud is as follows. The turbulence
disturbs the filamentary cloud, which fragments into cloud cores,
because of the gravitational instability (Figure 5(a)). The cloud
cores undergo gravitational collapse (Figures 5(b)–(c)); at the
center of this, fragmentation produces four protostars (sink
particles) in total; and, eventually, three protostars survive
(Figure 5(e)). Figure 5 shows a snapshot at tp = 2.41 × 104
yr,
where tp is the time that has elapsed since the first protostar
formation. At this stage, the three protostars exhibit stable orbits,
with a close pair with a separation of 20 au (Figure 5(f)) and an
outer protostar with a wide separation of 120–200 au. As shown
in Figure 5(d), the gravitational interaction between the
protostars and the infalling envelope gas produces long spiral
arms on a scale of several hundreds of astronomical units.
Figure 3. The SO 88 − 77 spectral grid map of IRAS 04239+2436. The background gray image is the SO peak intensity map with a threshold of 6σ (= 0.02 Jy
beam−1
). The blue contours show the two continuum sources, Source A (the eastern source) and Source B (the western source) at 857 μm. The contours are 6, 18, and
36 mJy beam−1
. The vertical dotted lines in each grid indicate the source velocity of 6.5 km s−1
. The broad SO line profiles are detected around Source B. The open
ellipse in the lower right corner represents the beam size.
4
The Astrophysical Journal, 953:82 (13pp), 2023 August 10 Lee et al.
5. In this simulation, all the protostars except for the first one
are formed by disk fragmentation. Figure 6 shows the time
sequence for the formation of protostars and the evolution of
their orbits. The first protostar forms in a filamentary structure
caused by the turbulence within the cloud core (Figure 6(a)).
The protostar has a circumstellar disk and the disk fragments to
form a second protostar (Figure 6(b)). Then the third and fourth
protostars form in succession, one of which merges with the
other, and eventually three protostars survive (Figures 6(c)–
(e)). The triple stars show chaotic orbits in the early stages, but
the orbits gradually stabilize (Figures 6(f)–(h)). The stage of the
simulation when the overall spiral arm structures are matched
well with the observation is tp = 1.95 × 104
yr.
The protostars are assigned an ID number in the order of
formation. Protostar 1 has the most massive disk, with the
highest mass and accretion rate (Figure 7). In contrast,
protostars 0 and 2 have low accretion rates and smaller masses.
Protostars 0 and 2 form a close binary. Due to a small
separation between them, the disks are truncated by dynamical
encounters intermittently. These encounters bring about small
disks and low accretion rates and also the misalignment of the
disks, as shown in Figure 8 (Bate et al. 2010; Bate 2018),
which has been considered as a resulting phenomenon of
turbulent fragmentation in the early evolutionary stage of
binary formation (Lee et al. 2017).
The interaction between the triplets and the infalling
envelope excites the arms. The velocity structure of the arms
is shown in Figure 9. In Figure 9(b), the diffuse arms shown to
the upper right of the figure have positive radial velocity
(outward velocity), while the prominent arms on the left side
have negative radial velocity (infall velocity). The infall
velocity along the arms reaches 1–1.5 km s−1
, and the arm
structure can be described as infalling streamers, which are
narrow structures that asymmetrically feed gas from the
envelope to the scale of the circumstellar disks (e.g., Pineda
et al. 2020; Bianchi et al. 2022; Thieme et al. 2022). The spiral
arms also have rotation velocity. The arm extending from the
south of the triplets has a high rotation velocity due to the
gravity of the protostar (Figure 9(c)). Quantitative velocity
analysis along the arm is described in Section 4.2.
Figure 10 shows the shock velocity and density associated
with the arms. When the arms are accelerated by the
gravitational torque, the shock velocity exceeds 3 km s−1
(Figure 10(a)). Because an arm accelerated to ∼1 km s−1
collides with the infalling gas with ∼1 km s−1
in the envelope,
the shock velocity may reach 3 km s−1
. While the arms
propagate into the infalling envelope, the shock velocity
decreases to 1.5–2 km s−1
. The number density in the arms
exceeds 107–8
cm−3
(Figure 10(b)). Such velocities and
densities of the arms can enhance the SO abundance along
the arms (van Gelder et al. 2021).
4. Discussion
4.1. A Triple Protostellar System, IRAS 04239+2436
The mid-IR light curve of IRAS 04239+2436 shows a
periodicity of ∼8 yr (Figure 11), which is further strong
evidence of unresolved close binary interaction within this
system, and thus indicative oftriple protostars. The anticipated
orbital period of the resolved binary is about 270 yr. The finely
collimated strong jet and series of jet knots of Source A in
IRAS 04239+2436 invoke the existence of disks fueled from a
bigger mass reservoir, i.e., the circumbinary disk or envelope
(Jørgensen et al. 2022), despite the small sizes of the
circumstellar disks truncated by the very close binary
interaction within Source A (Reipurth et al. 2000;
Reipurth 2000). In addition, the time intervals between the
observed jet knots are consistent with the unresolved close
binary orbit (Reipurth et al. 2000).
In the NIR images, Source A, which is likely an unresolved
very close binary, as mentioned above, is brighter than Source
B. However, the comparison with the numerical simulation
suggests that Source B is the more massive component
(Figures 7 and 12), with a larger disk (Figure 8), which can
obscure the NIR emission effectively. Another triple system
with spirals, L1448 IRS3B (Tobin et al. 2016), also shows that
the dimmer component is more massive; unlike IRAS 04239
+2436, the more massive one is the close binary in L1448
IRS3B. The HCN line emission is detected only toward Source
B, consistently supporting the existence of a very massive disk
around Source B (Figure 2(b)), which is likely actively
accreting gas along spiral arm 2 (Figures 3 and 12(a)).
According to the simulation (see Figure 8), the column density
of the larger disk is higher, resulting in its mass being higher
than the other two close disks by a factor of 100. In addition,
the accretion rate in the primary is higher than those of the
secondary and tertiary by more than a factor of 3. This higher
accretion rate to the more massive protostar heats its disk more
efficiently. As a result, the HCN line intensity, which is
proportional to the column density and temperature, is strong
enough to be detected in Source B.
This accretion streamer associated with Source B and arm 2
is traced by another shock tracer, the SO2 emission
(Figures 2(c)–(d)), as well as the broad SO line profiles around
Source B (see Figure 1(b) and the broadened line profiles in
Figure 3). In contrast, the 857 μm continuum fluxes toward
Sources A (51.5 ± 0.3 mJy) and B (52.8 ± 0.3 mJy) are
comparable. This could be due to the continuum optical depth.
Figure 4. The SO intensity-weighted velocity map (colors) and the HCO+
integrated intensity map (contours). The contour levels are 4.0, 5.5, 6.5, 7.5,
and 10.0 σ (σ = 0.017 Jy beam−1
). The SO emission traces the spiral arm
structures, while the HCO+
emission traces the outflow cavity walls. The blue
(PA = 59°) and red (PA = 226°) arrows indicate the directions of the [Fe II]
1.644 μm jet of HH 300 (Reipurth et al. 2000).
5
The Astrophysical Journal, 953:82 (13pp), 2023 August 10 Lee et al.
6. In the massive disk around Source B, grains easily grow to
millimeter sizes and become optically thick at millimeter
wavelengths (Harsono et al. 2018; Lee et al. 2019). As a result,
the submillimeter emission may not trace the total disk mass, as
shown in the ALMA observation of L1448 IRS3B (Tobin
et al. 2016).
4.2. Comparison between Observations and Simulations
While the total protostellar mass and their separation are
greater than those observed toward IRAS 04239+2436 (Lee
et al. 2016), we emphasize that the overall arm features
(Figure 12) and their kinematics (Figure 13) produced by the
simulation are very similar to the observed ones. Figure 13
compares the kinematics between observations (solid lines) and
simulations (dashed lines) along the spiral arms to show that
the simulated dynamical process governs the observed arm
structures. In Figure 12, the total gas distribution is presented
for the simulation, while the observed arm structures in IRAS
04239+2436 are revealed by the SO emission, which traces the
shocked gas. The peak intensities of the continuum in the
circumstellar disks are about 40 mJy beam−1
, and the rms noise
level is about 0.1 mJy beam−1
. In order to detect the spiral arms
in the dust continuum, the column density of the spiral arms
must be greater than 1% of the peak column density of the
circumstellar disks. While the column densities of the
simulated spiral arms are lower than that, they satisfy well
the physical conditions for the SO chemistry (van Gelder et al.
2021), as seen in Figure 10.
Figure 13(a) presents the velocity at the peak intensity
position (hereafter, the peak velocity) along each spiral arm
feature in the SO emission as a function of deprojected radius
(the symbols connected by solid colored lines). The source
velocity is VLSR = 6.5 km s−1
, adopted from C18
O 1–0 and
C17
O 1–0 observations (Fuller & Ladd 2002). The peak
intensity positions were measured on the peak intensity map of
SO 88–77, which is deprojected by an inclination angle of 55°
and a PA of 140° (Figure 13(b)). Because a circumbinary disk
has not been detected, we assume 55° and 140°, based on the
inclination (50°–61°) and PA (137°–145°) measured from the
continuum sources. We also assume that all the spiral arms are
on the same plane. For a deprojected radius from 0 1 to 2 7, in
steps of 0 1, an intensity profile along the azimuthal direction
was extracted and the peak intensity position was measured. At
each deprojected radius, the line-of-sight velocity (Vlos) was
derived from the SO 88–77 data cube. In Figure 13(b), the peak
intensity positions of each arm are marked by symbols in
different colors that represent their velocities as given by a
color bar. The center position is the center of mass of Sources
A and B, on the assumption of equal mass. As seen in the
Figure 5. Column density distribution along the y-direction on six different scales at the last stage of the simulation (t = 6.97 × 105
yr and tp = 2.41 × 104
yr). The
color scales show the column density on a logarithmic scale. The crosses show the positions of the protostars, which are labeled with identification numbers. The
column density was obtained by extracting the cubic region from the entire data. Note that each panel shows different size scales.
6
The Astrophysical Journal, 953:82 (13pp), 2023 August 10 Lee et al.
7. Figure 6. Disk fragmentation at the center of the cloud core. Eight representative snapshots are shown. The upper panels (a)–(d) show the formation stages of
protostars 1–4 from left to right. The lower panels show the stages of (e) the merger of protostars 1 and 3, (f) the forming of a close binary pair, (g) the exchanging of
the pair, and (h) reaching an almost steady orbit. The color scale shows the column density distribution on a logarithmic scale, obtained from a box of (200 au)3
. The
protostars are labeled with identification numbers in the order of formation epoch. Each panel shown is centered on the center of mass of the protostars.
Figure 7. Masses of the protostars as a function of time after the first protostar formation. The number associated with each line indicates the identification number of
each protostar. The dashed lines show the relationships of the mass accretion rates M c G
13 s
3
=
and c G
3 s
3
, for comparison. Sink particles 0 and 2 constitute the close
binary pairs.
7
The Astrophysical Journal, 953:82 (13pp), 2023 August 10 Lee et al.
8. figure, the peak positions mostly well trace the spiral arm
features, but arms 2 and 3 are not clearly distinguishable in the
inner region (r 0 7 or r 100 au) where SO emission is the
brightest, and the two arms are likely overlapped or colliding.
Considering the complex emission around the center and the
angular resolution (∼0 1) of the observation, the peak velocity
at r < 70 au may not be reliable.
Figure 13(a) also presents the velocities of the arms derived
from our simulation (dashed colored lines) and the Keplerian
rotation (black lines) for comparison. Since the total mass and
separations among the companions from the simulation are
larger than those of IRAS 04239+2436 by a factor of 2, the
deprojected radii of the simulation are scaled by a half in the
figure. As the overall arm features of IRAS 04239+2436 and
the simulation are similar (Figure 12), their velocity profiles
also show similar trends (Figure 13(a)). The velocity of the
arms is not explained by a single Keplerian rotation curve,
although arms 1 and 2, beyond 100 au, roughly trace the
Keplerian rotation caused by the mass between 0.6 Me and
0.15 Me. In addition, the observed structure of arm 1 beyond
1 5 is not fitted by a polynomial function simultaneously with
the inner part of the arm as presented in Figure 13(b).
Note that Figure 13(a) displays the line-of-sight velocity,
which is a composite of the infall velocity and the rotation
velocity. In contrast, Figure 14(a) shows the infall velocity and
rotation velocity separately along the arms, based on the
Figure 8. The zoomed-in snapshot images toward the triple system at two time steps. We chose the later time step that best describes the spiral features of IRAS 04239
+2436. At the earlier time step, one of the very close binaries shows a misaligned disk rotation axis, while the misalignment is reduced at the later time step. The mass
of the massive disk is 20% of the central stellar mass, while the less massive disks have masses as low as 1% of the central stellar masses.
Figure 9. Face-on views of the distributions of (a) column density, (b) radial velocity, and (c) rotation velocity excess from the Keplerian rotation, at the stage shown
in Figure 12(c). The arrows in the left panel show the velocity distribution. All the velocity distributions are measured as a relative velocity with respect to the
barycenter of the three protostars, and the density-weighted averages of the velocities are projected onto the midplane in all the panels.
8
The Astrophysical Journal, 953:82 (13pp), 2023 August 10 Lee et al.
9. simulation with 3D velocity components. The location of the
arms in the simulation is depicted in Figure 14(b). Arm 1
(represented by the red lines in Figure 14(a)) has a considerable
infall velocity, which is comparable to, but less than, the
rotation velocity in the range of 150 au R 300 au. Arms 2
and 3 (blue and green lines) exhibit considerably larger infall
velocity than rotation velocity in the outer part where
R 100 au. Therefore, arms 1, 2, and 3 are classified as
infalling streamers, but their infall velocities are less than the
freefall velocity (black solid line). In the inner region where
R 100 au, all the arms exhibit rotation velocities that exceed
the infall velocities and the Keplerian velocity (black dashed
line) due to the gravitational torque from the orbiting
protostars.
4.3. Multiple Formation and Magnetic Field Strength
A magnetic field must be weak to form a multiple stellar
system via the fragmentation of a cloud core or a disk (Machida
et al. 2005). To test the effect of the magnetic field on the
Figure 10. Shock velocity associated with the arms (left) and number density distribution (right). The data are rotated so that they are oriented in a face-on view. The
shock velocity is measured as a velocity jump in the horizontal direction. The maximum velocity jump along the z-direction (the line of sight) is shown. The right
panel shows the maximum number density along the z-direction. The contour levels are n = 107
, 108
, 109
, and 1010
cm−3
in the right panel. The arrows in both panels
show the density-weighted velocity distribution. A typical stage that exhibits the shock velocity is shown here and is different from the stage in Figure 12(c).
Figure 11. The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) light curves of IRAS 04239+2436 at 3.4 (W1; red) and 4.6 (W2; blue) μm. We
used the NEOWISE-R Single Exposure (L1b) Source Table available at the NASA/IPAC Infrared Science Archive (NEOWISE Team 2023). The periodograms of
these light curves present a periodicity of ∼8 yr (gray sinusoidal curves) both in W1 and W2. This period might be associated with bright [Fe II] jet knots spaced with
∼1″ (Reipurth et al. 2000). We adopted the method developed by a variability study of young stellar objects (Park et al. 2021) for the construction of the NEOWISE
light curves and periodogram analysis, except for including newly released data points for the most recent four epochs.
9
The Astrophysical Journal, 953:82 (13pp), 2023 August 10 Lee et al.
10. formation of multiples and the following development of large
spiral arms, we also ran magnetohydrodynamic (MHD)
simulations, varying the initial magnetic field strength, and
present the results in Figure 15.
The initial condition and numerical models are the same as
those of the HD model, but the magnetic fields are included.
Uniform magnetic fields perpendicular to the filamentary cloud
are imposed as the initial condition, because recent observa-
tions have suggested that dense filaments tend to have
perpendicular magnetic fields (Pattle et al. 2022). Three models
with the initial magnetic field strengths of 1, 5, and 10 μG are
considered. The magnetic field strength is often described in
terms of the mass-to-flux ratio, and the critical magnetic field
strength (Nakano & Nakamura 1978; Tomisaka et al. 1988) is
estimated as Bcr = 2πG1/2
Σ = 20 μG for our models. The
initial magnetic field strengths of 1, 5, and 10 μG are therefore
0.05, 0.25, and 0.5Bcr, respectively (corresponding to the
nondimensional mass-to-flux ratios of μ = 20, 4, and 2). Thus,
only magnetically supercritical clouds are considered here. For
an MHD scheme, we adopted Boris-HLLD (Matsumoto et al.
2019a), which allows us to follow a long-term evolution, even
in cases of strong magnetic fields. The ohmic dissipation is
considered according to previous simulations (Matsumoto 2011;
Matsumoto et al. 2017). The MHD scheme has second-order
accuracy in space to maintain numerical stability, while the HD
scheme has third-order accuracy.
The MHD models exhibit similar evolution to the HD
model; the filamentary cloud fragments into cloud cores, which
undergo gravitational collapse. A multiple- or single-star
system forms at the center of the cloud core, depending on
the initial magnetic field strength. Models with weaker
magnetic fields tend to form multiple systems with more
companions (Figure 15) and to have more prominent and more
extended arms (Figure 16). The models with 0, 1, 5, and 10 μG
form the systems consisting of three (triple), four (quadruple),
two (binary), and one (single) stars, respectively.
According to our MHD simulations, the natal cloud of IRAS
04239+2436 must have a very weak magnetic field, with a
nondimensional mass-to-flux ratio larger than μ = 2–4, to form
a multiple system. Recent observations of the submillimeter
dust emission polarization also show that the strong magnetic
field in large filamentary structures is weakened down to the
magnetically supercritical condition at small core scales (Doi
et al. 2021). The present observation provides more strong
Figure 12. Comparisons between observations and simulations. (a) The SO 88–77 peak intensities in units of mJy beam−1
and (b) the velocities of the intensity peaks
in units of km s−1
toward IRAS 04239+2436. The source velocity is VLSR = 6.5 km s−1
. The SO peak intensity and velocity maps were generated using a threshold of
6σ (0.02 Jy beam−1
). The contours in (a) and (b) present the continuum emission at 857 μm. (c) The gas column density distribution and (d) the velocity distribution
of the numerical HD simulation. The arms that are clearly identifiable are named in (a), and the arms that may correspond to the simulation are marked in (c). The
white dots (c) and crosses (d) mark the positions of the three protostars. The simulation was rotated and projected consistently with IRAS 04239+2436.
10
The Astrophysical Journal, 953:82 (13pp), 2023 August 10 Lee et al.
11. observational evidence of the reduced effect of the magnetic
field in a star-forming dense core (Eswaraiah et al. 2021).
4.4. Planet Formation in Multiple Protostellar Systems
Accumulating evidence suggests that the planet-forming
environment around multiple systems must be very different,
generally more hostile, from that around single stars. Continuum
observations show that dust disks in binary systems are smaller
in size (Zagaria et al. 2021a), as dust grains drift inward faster in
those disks (Zagaria et al. 2021b) and due to tidal truncation. The
disk gas also likely dissipates faster in multiple systems, owing
to higher accretion rates (Zagaria et al. 2022). Disks in
binary systems have not only a limited amount of dust grains,
but also a limited time to form planets. The smaller the
separation, the worse the prospects; the dust continuum fluxes
also tend to increase with the separation between companions
(Zagaria et al. 2021a). These facts about disks are consistent with
facts about the outcomes: the frequency of planets in close
(<100 au) binary systems is low compared to those in wide
binaries or around single stars (Kraus et al. 2016; Ngo et al.
2016; Fontanive et al. 2019; Marzari & Thebault 2019). We now
add to the difficulties by finding evidence for interaction
between disks and the envelope at the protostellar stage. In
IRAS 04239+2436, which is a close binary/multiple system
Figure 13. Kinematics of the spiral arms of IRAS 04239+2436. (a) Peak velocities (relative to source velocity) along the spiral arms. The colored solid lines with
symbols are the velocities at the peak intensity positions of the spiral arm features (Figure 12) of IRAS 04239+2436. The filled symbols are the velocities at the
positions used for the polynomial fittings, as presented with the solid black curves in (b). The colored dashed lines are the velocities of the arm features from the
simulation, where the deprojected radii are scaled by a half to match the total mass of the companions. The black lines are the Keplerian rotation curves of 0.15 Me
(solid), 0.30 Me (dotted), and 0.60 Me (dashed). (b) Peak intensity positions and velocities of the spiral arms (colors) on the deprojected peak intensity map of SO 88–
77 (gray image). The symbol “×” marks the center position defined by the center of mass of the two continuum sources, assuming an equal mass. The black solid lines
indicate the polynomial fitting results over the peak intensity positions that may belong to the arm structures with coherent kinematics. Gray circles are drawn from
0 5 to 2 5 in steps of 0 5.
Figure 14. (a) Infall and rotation velocity distribution along the arms as a function of radius for the simulation. For comparison, black lines are shown for the freefall
velocity (solid) and the Keplerian rotation velocity (dashed) for the total mass of the sink particles in the simulation (0.71Me). The radius is scaled to fit Figure 13(b).
(b) Configuration of the spiral arms (red curves) for the simulation, which is shown in the face-on view. Each spiral arm is labeled with an ID number. The color scale
shows the column density distribution, but the gas with a density higher than n 10 cm
min
8 3
= - is shown.
11
The Astrophysical Journal, 953:82 (13pp), 2023 August 10 Lee et al.
12. with very small (<10 au) continuum disks, planet formation may
have been negatively impacted by the interactions. For all these
reasons, IRAS 04239+2436 is not a likely place for planet
formation.
5. Conclusions
Although most stars form in multiple-star systems, their
formation process is still controversial. In contrast to the single-
star formation process, dynamical interactions take place not
only among the protostars, but also between the central
compact objects and the infalling gaseous envelope. Because
the accretion history can be lost in a few orbital timescales, it is
important to capture the signatures of these dynamical
interactions by zooming into such a system at the earliest
possible formation epoch in order to better understand the
formation process of multiple-star systems. According to our
high-resolution and high-sensitivity ALMA observation, IRAS
04239+2436, which has been known as a protostellar binary
system, shows clear triple spiral arms surrounding a young
potentially triple protostellar system in the SO line emission.
The spiral arms traced by shocked SO gas act as accretion
flows over 400 au in length from the large-scale envelope to the
50 au scale stellar system. The imaging results are compared
with the numerical MHD simulations of analogous systems.
While both magnetic fields and turbulence are important to
shaping the natal molecular cloud, our numerical simulations
suggest that the multiple asymmetric arms may be character-
istic of multiple protostars forming in regions of weak magnetic
fields.
Acknowledgments
ALMA is a partnership of ESO (representing its member
states), NSF (USA), and NINS (Japan), together with NRC
(Canada), NSC and ASIAA (Taiwan), and KASI (Republic of
Korea), in cooperation with the Republic of Chile. The Joint
ALMA Observatory is operated by ESO, AUI/NRAO, and
NAOJ. This paper makes use of the following ALMA data:
ADS/JAO.ALMA#2015.1.01397.S. J.E.L. is supported by a
National Research Foundation of Korea (NRF) grant funded by
the Korea government (MSIT; grant No. 2021R1A2C1011718).
D.H. is supported by the Centre for Informatics and Computa-
tion in Astronomy (CICA) and grant No. 110J0353I9 from the
Figure 15. Comparison of the surface density distributions among the HD/MHD models with initial magnetic field strengths of 0 G, 1 μG, 5 μG, and 10,μG, from left
to right. The upper panels and lower panels display the (1000 au)2
and (200 au)2
regions, respectively. The models produce triple stars (0 G model), quadruple stars (1,
μG model), binary stars (5 μG model), and a single star (10 μG model). The HD model (0 G) shown here is calculated using the second-order accuracy scheme, rather
than the third-order accuracy scheme, to ensure a fair comparison with the MHD models.
Figure 16. The maximum extent of the column density distribution as a
function of initial magnetic field for given thresholds of the column density
(Nth) for the models shown in Figure 15, indicating the maximum extent of the
spiral streamers/arms for each model. The maximum extent is determined by
measuring the longest distance between the gas structure with a column density
higher than Nth and the center of mass of the protostars.
12
The Astrophysical Journal, 953:82 (13pp), 2023 August 10 Lee et al.
13. Ministry of Education of Taiwan. D.H. acknowledges support
from the Ministry of Science of Technology of Taiwan through
grant No. 111B3005191. Numerical computations were carried
out in part on XC50 (ATERUI II) at the Center for
Computational Astrophysics (CfCA), National Astronomical
Observatory of Japan. T.M. is supported by JSPS KAKENHI
grant Nos. JP23K03464, JP18H05437, and JP17K05394. This
publication also makes use of data products from NEOWISE,
which is a project of the Jet Propulsion Laboratory/California
Institute of Technology, funded by the Planetary Science
Division of the National Aeronautics and Space Administra-
tion.K.T. was supported by JSPS KAKENHI grant No.
JP20H05645.
Facility: ALMA.
Software: CASA (McMullin et al. 2007), SFUMATO
(Matsumoto 2007).
ORCID iDs
Jeong-Eun Lee https:/
/orcid.org/0000-0003-3119-2087
Tomoaki Matsumoto https:/
/orcid.org/0000-0002-
8125-4509
Hyun-Jeong Kim https:/
/orcid.org/0000-0001-9263-3275
Seokho Lee https:/
/orcid.org/0000-0002-0226-9295
Daniel Harsono https:/
/orcid.org/0000-0001-6307-4195
Jaehan Bae https:/
/orcid.org/0000-0001-7258-770X
Neal J. Evans II https:/
/orcid.org/0000-0001-5175-1777
Shu-ichiro Inutsuka https:/
/orcid.org/0000-0003-4366-6518
Ken’ichi Tatematsu https:/
/orcid.org/0000-0002-8149-8546
Jae-Joon Lee https:/
/orcid.org/0000-0003-0894-7824
Daniel Jaffe https:/
/orcid.org/0000-0003-3577-3540
References
Alves, F. O., Caselli, P., Girart, J. M., et al. 2019, Sci, 366, 90
Arzoumanian, D., André, P., Didelon, P., et al. 2011, A&A, 529, L6
Bate, M. R. 2018, MNRAS, 475, 5618
Bate, M. R., & Bonnell, I. A. 1997, MNRAS, 285, 33
Bate, M. R., Lodato, G., & Pringle, J. E. 2010, MNRAS, 401, 1505
Bianchi, E., López-Sepulcre, A., Ceccarelli, C., et al. 2022, ApJL, 928, L3
Diaz-Rodriguez, A. K., Anglada, G., Blázquez-Calero, G., et al. 2022, ApJ,
930, 91
Doi, Y., Tomisaka, K., Hasegawa, T., et al. 2021, ApJL, 923, L9
Esplugues, G. B., Viti, S., Goicoechea, J. R., & Cernicharo, J. 2014, A&A,
567, A95
Eswaraiah, C., Li, D., Furuya, R. S., et al. 2021, ApJL, 912, L27
Fontanive, C., Rice, K., Bonavita, M., et al. 2019, MNRAS, 485, 4967
Fuller, G. A., & Ladd, E. F. 2002, ApJ, 573, 699
Greene, T. P., & Lada, C. J. 1996, ApJ, 461, 345
Harsono, D., Bjerkeli, P., van der Wiel, M. H. D., et al. 2018, NatAs, 2,
646
Jørgensen, J. K., Kuruwita, R. L., Harsono, D., et al. 2022, Natur, 606,
272
Kratter, K. M., Matzner, C. D., Krumholz, M. R., & Klein, R. I. 2010, ApJ,
708, 1585
Kraus, A. L., Ireland, M. J., Huber, D., Mann, A. W., & Dupuy, T. J. 2016, AJ,
152, 8
Larson, R. B. 1981, MNRAS, 194, 809
Lee, J.-E., Lee, S., Baek, G., et al. 2019, NatAs, 3, 314
Lee, J.-E., Lee, S., Dunham, M. M., et al. 2017, NatAs, 1, 0172
Lee, S., Lee, J.-E., Park, S., et al. 2016, ApJ, 826, 179
Machida, M. N., Matsumoto, T., Hanawa, T., & Tomisaka, K. 2005, MNRAS,
362, 382
Marzari, F., & Thebault, P. 2019, Galax, 7, 84
Masunaga, H., Miyama, S. M., & Inutsuka, S.-i. 1998, ApJ, 495, 346
Matsumoto, T. 2007, PASJ, 59, 905
Matsumoto, T. 2011, PASJ, 63, 317
Matsumoto, T., Dobashi, K., & Shimoikura, T. 2015a, ApJ, 801, 77
Matsumoto, T., Machida, M. N., & Inutsuka, S.-i. 2017, ApJ, 839, 69
Matsumoto, T., Miyoshi, T., & Takasao, S. 2019a, ApJ, 874, 37
Matsumoto, T., Onishi, T., Tokuda, K., & Inutsuka, S. I. 2015b, MNRAS Lett.,
449, L123
Matsumoto, T., Saigo, K., & Takakuwa, S. 2019b, ApJ, 871, 36
McMullin, J. P., Waters, B., Schiebel, D., Young, W., & Golap, K. 2007, in
ASP Conf. Ser. 376, Astronomical Data Analysis Software and Systems
XVI, ed. R. A. Shaw, F. Hill, & D. J. Bell (San Francisco, CA: ASP), 127
Millar, T. J. 1993, in Dust and Chemistry in Astronomy, ed. T. J. Millar &
D. A. Williams (Philadelphia, PA: Institute of Physics Publishing), 249
Moe, M., & Kratter, K. M. 2018, ApJ, 854, 44
Müller, H. S. P., Schlöder, F., Stutzki, J., & Winnewisser, G. 2005, JMoSt,
742, 215
Nakano, T., & Nakamura, T. 1978, PASJ, 30, 671
NEOWISE Team 2023, NEOWISE-R Single Exposure (L1b) Source Table,
IPAC, doi:10.26131/IRSA144
Ngo, H., Knutson, H. A., Hinkley, S., et al. 2016, ApJ, 827, 8
Offner, S. S. R., Kratter, K. M., Matzner, C. D., Krumholz, M. R., &
Klein, R. I. 2010, ApJ, 725, 1485
Offner, S. S. R., Moe, M., Kratter, K. M., et al. 2022, arXiv:2203.10066
Ostriker, J. 1964, ApJ, 140, 1056
Park, W., Lee, J.-E., Contreras Peña, C., et al. 2021, ApJ, 920, 132
Pattle, K., Fissel, L., Tahani, M., Liu, T., & Ntormousi, E. 2022, arXiv:2203.
11179
Pickett, H. M., Poynter, R. L., Cohen, E. A., et al. 1998, JQSRT, 60, 883
Pineda, J. E., Segura-Cox, D., Caselli, P., et al. 2020, NatAs, 4, 1158
Reipurth, B. 2000, AJ, 120, 3177
Reipurth, B., Yu, K. C., Heathcote, S., Bally, J., & Rodríguez, L. F. 2000, AJ,
120, 1449
Stodólkiewicz, J. S. 1963, AcA, 13, 30
Takakuwa, S., Saigo, K., Matsumoto, T., et al. 2017, ApJ, 837, 86
Thieme, T. J., Lai, S.-P., Lin, S.-J., et al. 2022, ApJ, 925, 32
Tobin, J. J., Kratter, K. M., Persson, M. V., et al. 2016, Natur, 538, 483
Tomisaka, K., Ikeuchi, S., & Nakamura, T. 1988, ApJ, 335, 239
Truelove, J. K., Klein, R. I., McKee, C. F., et al. 1997, ApJL, 489, L179
van Gelder, M. L., Tabone, B., van Dishoeck, E. F., & Godard, B. 2021, A&A,
653, A159
Zagaria, F., Clarke, C. J., Rosotti, G. P., & Manara, C. F. 2022, MNRAS,
512, 3538
Zagaria, F., Rosotti, G. P., & Lodato, G. 2021a, MNRAS, 507, 2531
Zagaria, F., Rosotti, G. P., & Lodato, G. 2021b, MNRAS, 504, 2235
13
The Astrophysical Journal, 953:82 (13pp), 2023 August 10 Lee et al.