1) Massive black hole binaries form during galaxy mergers and evolve through dynamical friction and 3-body interactions with stars until reaching separations of ~0.01 pc where gravitational wave emission takes over.
2) Gas dynamics may also drive black hole binaries to smaller separations for coalescence.
3) Black hole binary coalescence timescales are typically long, on the order of billions of years, which has implications for gravitational wave detection and triple black hole interactions.
Periodic mass extinctions_and_the_planet_x_model_reconsideredSérgio Sacani
The 27 Myr periodicity in the fossil extinction record has been con-
firmed in modern data bases dating back 500 Myr, which is twice the time
interval of the original analysis from thirty years ago. The surprising regularity
of this period has been used to reject the Nemesis model. A second
model based on the sun’s vertical galactic oscillations has been challenged
on the basis of an inconsistency in period and phasing. The third astronomical
model originally proposed to explain the periodicity is the Planet
X model in which the period is associated with the perihelion precession
of the inclined orbit of a trans-Neptunian planet. Recently, and unrelated
to mass extinctions, a trans-Neptunian super-Earth planet has been proposed
to explain the observation that the inner Oort cloud objects Sedna
and 2012VP113 have perihelia that lie near the ecliptic plane. In this
Letter we reconsider the Planet X model in light of the confluence of the
modern palaeontological and outer solar system dynamical evidence.
Key Words: astrobiology - planets and satellites - Kuiper belt:
general - comets: general
Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of
1011.5 K. Relativistic boosting can increase its observed value, but apparent brightness temperatures
much in excess of 1013 K are inaccessible using ground-based very long baseline interferometry (VLBI)
at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission
RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as
small as 26 µas (2.7 light months) and brightness temperature in excess of 1013 K. These measurements
challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive
black holes and require a much higher Doppler factor than what is determined from jet apparent
kinematics.
Keywords: galaxies: active — galaxies: jets — radio continuum: galaxies — techniques: interferometric
— quasars: individual (3C 273)
Young remmants of_type_ia_supernovae_and_their_progenitors_a_study_of_snr_g19_03Sérgio Sacani
Type Ia supernovae, with their remarkably homogeneous light curves and spectra, have been used as
standardizable candles to measure the accelerating expansion of the Universe. Yet, their progenitors
remain elusive. Common explanations invoke a degenerate star (white dwarf) which explodes upon
reaching close to the Chandrasekhar limit, by either steadily accreting mass from a companion star
or violently merging with another degenerate star. We show that circumstellar interaction in young
Galactic supernova remnants can be used to distinguish between these single and double degenerate
progenitor scenarios. Here we propose a new diagnostic, the Surface Brightness Index, which can
be computed from theory and compared with Chandra and VLA observations. We use this method
to demonstrate that a double degenerate progenitor can explain the decades-long
ux rise and size
increase of the youngest known Galactic SNR G1.9+0.3. We disfavor a single degenerate scenario.
We attribute the observed properties to the interaction between a steep ejecta prole and a constant
density environment. We suggest using the upgraded VLA to detect circumstellar interaction in
the remnants of historical Type Ia supernovae in the Local Group of galaxies. This may settle the
long-standing debate over their progenitors.
Subject headings: ISM: supernova remnants | radio continuum: general | X-rays: general | bi-
naries: general | circumstellar matter | supernovae: general | ISM: individual
objects(SNR G1.9+0.3)
We discovered two transient events in the Kepler eld with light curves that strongly suggest they
are type II-P supernovae. Using the fast cadence of the Kepler observations we precisely estimate
the rise time to maximum for KSN2011a and KSN2011d as 10.50:4 and 13.30:4 rest-frame days
respectively. Based on ts to idealized analytic models, we nd the progenitor radius of KSN2011a
(28020 R) to be signicantly smaller than that for KSN2011d (49020 R) but both have similar
explosion energies of 2.00:3 1051 erg.
The rising light curve of KSN2011d is an excellent match to that predicted by simple models of
exploding red supergiants (RSG). However, the early rise of KSN2011a is faster than the models
predict possibly due to the supernova shockwave moving into pre-existing wind or mass-loss from the
RSG. A mass loss rate of 10 4 M yr 1 from the RSG can explain the fast rise without impacting
the optical
ux at maximum light or the shape of the post-maximum light curve.
No shock breakout emission is seen in KSN2011a, but this is likely due to the circumstellar inter-
action suspected in the fast rising light curve. The early light curve of KSN2011d does show excess
emission consistent with model predictions of a shock breakout. This is the rst optical detection of
a shock breakout from a type II-P supernova.
The characterization of_the_gamma_ray_signal_from_the_central_milk_way_a_comp...Sérgio Sacani
Past studies have identified a spatially extended excess of ∼1-3 GeV gamma rays from the region
surrounding the Galactic Center, consistent with the emission expected from annihilating dark
matter. We revisit and scrutinize this signal with the intention of further constraining its characteristics
and origin. By applying cuts to the Fermi event parameter CTBCORE, we suppress the tails
of the point spread function and generate high resolution gamma-ray maps, enabling us to more
easily separate the various gamma-ray components. Within these maps, we find the GeV excess
to be robust and highly statistically significant, with a spectrum, angular distribution, and overall
normalization that is in good agreement with that predicted by simple annihilating dark matter
models. For example, the signal is very well fit by a 36-51 GeV dark matter particle annihilating to
b
¯b with an annihilation cross section of σv = (1−3)×10−26 cm3
/s (normalized to a local dark matter
density of 0.4 GeV/cm3
). Furthermore, we confirm that the angular distribution of the excess is
approximately spherically symmetric and centered around the dynamical center of the Milky Way
(within ∼0.05◦
of Sgr A∗
), showing no sign of elongation along the Galactic Plane. The signal is
observed to extend to at least ' 10◦
from the Galactic Center, disfavoring the possibility that this
emission originates from millisecond pulsars.
We present long-baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of
the 870 m continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that
trace millimeter-sized particles down to spatial scales as small as 1 AU (20 mas). These data reveal
a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli
(1{6AU) with modest contrasts (5{30%). We associate these features with concentrations of solids
that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima.
No signicant non-axisymmetric structures are detected. Some of the observed features occur near
temperatures that may be associated with the condensation fronts of major volatile species, but the
relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the
so-called zonal
ows). Other features, particularly a narrow dark annulus located only 1 AU from the
star, could indicate interactions between the disk and young planets. These data signal that ordered
substructures on AU scales can be common, fundamental factors in disk evolution, and that high
resolution microwave imaging can help characterize them during the epoch of planet formation.
Keywords: protoplanetary disks | planet-disk interactions | stars: individual (TW Hydrae)
3d modeling of_gj1214b_atmosphere_formation_of_inhomogeneous_high_cloouds_and...Sérgio Sacani
Uma equipe de cientistas da Universidade de Washington e da Universidade de Toronto foram os primeiros a simular nuvens exóticas em 3D na atmosfera de um exoplaneta.
O objeto em questão, é o GJ 1214b, um exoplaneta chamado de mini-Netuno que foi descoberto, seis anos atrás pelos astrônomos no Harvard-Smithsonian Center for Astrophysics.
Também conhecido como Gliese 1214b, esse mundo tem cerca de 2.7 vezes o diâmetro da Terra e uma massa quase 7 vezes maior que a massa do nosso planeta. Ele está localizado a cerca de 52 anos-luz de distância na constelação de Ophiuchus.
O planeta orbita a estrela anã vermelha, GJ 1214, a cada 38 horas, a uma distância de 1.3 milhões de milhas.
De acordo com estudos prévios, o planeta tem uma atmosfera rica em água ou hidrogênio com extensas nuvens.
“Deve existir altas nuvens ou uma névoa orgânica na atmosfera – como nós observamos em Titã. Sua temperatura atmosférica excede o ponto de fusão da água”, disse o Dr. Benjamin Charnay, um dos membros da equipe da Universidade de Washington.
Evidence for the_thermal_sunyaev-zeldovich_effect_associated_with_quasar_feed...Sérgio Sacani
Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar
catalogue, spanning redshifts 0.5–3.5, we derive the mean millimetre and far-infrared
quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology
Telescope and Herschel-Spectral and Photometric Imaging REceiver data. We
constrain the form of the far-infrared emission and find 3σ–4σ evidence for the thermal
Sunyaev-Zel’dovich (SZ) effect, characteristic of a hot ionized gas component with
thermal energy (6.2 ± 1.7) × 1060 erg. This amount of thermal energy is greater than
expected assuming only hot gas in virial equilibrium with the dark matter haloes of
(1 − 5) × 1012h
−1M that these systems are expected to occupy, though the highest
quasar mass estimates found in the literature could explain a large fraction of this
energy. Our measurements are consistent with quasars depositing up to (14.5±3.3) τ
−1
8
per cent of their radiative energy into their circumgalactic environment if their typical
period of quasar activity is τ8 × 108 yr. For high quasar host masses, ∼ 1013h
−1M,
this percentage will be reduced. Furthermore, the uncertainty on this percentage is
only statistical and additional systematic uncertainties enter at the 40 per cent level.
The SEDs are dust dominated in all bands and we consider various models for dust
emission. While sufficiently complex dust models can obviate the SZ effect, the SZ
interpretation remains favoured at the 3σ–4σ level for most models.
Exocometary gas in_th_hd_181327_debris_ringSérgio Sacani
An increasing number of observations have shown that gaseous debris discs are not an
exception. However, until now we only knew of cases around A stars. Here we present the first
detection of 12CO (2-1) disc emission around an F star, HD 181327, obtained with ALMA
observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric
disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with
radiative transfer calculations we study the dust and CO mass distribution. We find the dust is
distributed in a ring with a radius of 86:0 0:4 AU and a radial width of 23:2 1:0 AU. At
this frequency the ring radius is smaller than in the optical, revealing grain size segregation
expected due to radiation pressure. We also report on the detection of low level continuum
emission beyond the main ring out to 200 AU. We model the CO emission in the non-LTE
regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging
between 1:2 10 6 M and 2:9 10 6 M, depending on the gas kinetic temperature and
collisional partners densities. The CO densities and location suggest a secondary origin, i.e.
released from icy planetesimals in the ring. We derive a CO cometary composition that is
consistent with Solar system comets. Due to the low gas densities it is unlikely that the gas is
shaping the dust distribution.
Periodic mass extinctions_and_the_planet_x_model_reconsideredSérgio Sacani
The 27 Myr periodicity in the fossil extinction record has been con-
firmed in modern data bases dating back 500 Myr, which is twice the time
interval of the original analysis from thirty years ago. The surprising regularity
of this period has been used to reject the Nemesis model. A second
model based on the sun’s vertical galactic oscillations has been challenged
on the basis of an inconsistency in period and phasing. The third astronomical
model originally proposed to explain the periodicity is the Planet
X model in which the period is associated with the perihelion precession
of the inclined orbit of a trans-Neptunian planet. Recently, and unrelated
to mass extinctions, a trans-Neptunian super-Earth planet has been proposed
to explain the observation that the inner Oort cloud objects Sedna
and 2012VP113 have perihelia that lie near the ecliptic plane. In this
Letter we reconsider the Planet X model in light of the confluence of the
modern palaeontological and outer solar system dynamical evidence.
Key Words: astrobiology - planets and satellites - Kuiper belt:
general - comets: general
Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of
1011.5 K. Relativistic boosting can increase its observed value, but apparent brightness temperatures
much in excess of 1013 K are inaccessible using ground-based very long baseline interferometry (VLBI)
at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission
RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as
small as 26 µas (2.7 light months) and brightness temperature in excess of 1013 K. These measurements
challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive
black holes and require a much higher Doppler factor than what is determined from jet apparent
kinematics.
Keywords: galaxies: active — galaxies: jets — radio continuum: galaxies — techniques: interferometric
— quasars: individual (3C 273)
Young remmants of_type_ia_supernovae_and_their_progenitors_a_study_of_snr_g19_03Sérgio Sacani
Type Ia supernovae, with their remarkably homogeneous light curves and spectra, have been used as
standardizable candles to measure the accelerating expansion of the Universe. Yet, their progenitors
remain elusive. Common explanations invoke a degenerate star (white dwarf) which explodes upon
reaching close to the Chandrasekhar limit, by either steadily accreting mass from a companion star
or violently merging with another degenerate star. We show that circumstellar interaction in young
Galactic supernova remnants can be used to distinguish between these single and double degenerate
progenitor scenarios. Here we propose a new diagnostic, the Surface Brightness Index, which can
be computed from theory and compared with Chandra and VLA observations. We use this method
to demonstrate that a double degenerate progenitor can explain the decades-long
ux rise and size
increase of the youngest known Galactic SNR G1.9+0.3. We disfavor a single degenerate scenario.
We attribute the observed properties to the interaction between a steep ejecta prole and a constant
density environment. We suggest using the upgraded VLA to detect circumstellar interaction in
the remnants of historical Type Ia supernovae in the Local Group of galaxies. This may settle the
long-standing debate over their progenitors.
Subject headings: ISM: supernova remnants | radio continuum: general | X-rays: general | bi-
naries: general | circumstellar matter | supernovae: general | ISM: individual
objects(SNR G1.9+0.3)
We discovered two transient events in the Kepler eld with light curves that strongly suggest they
are type II-P supernovae. Using the fast cadence of the Kepler observations we precisely estimate
the rise time to maximum for KSN2011a and KSN2011d as 10.50:4 and 13.30:4 rest-frame days
respectively. Based on ts to idealized analytic models, we nd the progenitor radius of KSN2011a
(28020 R) to be signicantly smaller than that for KSN2011d (49020 R) but both have similar
explosion energies of 2.00:3 1051 erg.
The rising light curve of KSN2011d is an excellent match to that predicted by simple models of
exploding red supergiants (RSG). However, the early rise of KSN2011a is faster than the models
predict possibly due to the supernova shockwave moving into pre-existing wind or mass-loss from the
RSG. A mass loss rate of 10 4 M yr 1 from the RSG can explain the fast rise without impacting
the optical
ux at maximum light or the shape of the post-maximum light curve.
No shock breakout emission is seen in KSN2011a, but this is likely due to the circumstellar inter-
action suspected in the fast rising light curve. The early light curve of KSN2011d does show excess
emission consistent with model predictions of a shock breakout. This is the rst optical detection of
a shock breakout from a type II-P supernova.
The characterization of_the_gamma_ray_signal_from_the_central_milk_way_a_comp...Sérgio Sacani
Past studies have identified a spatially extended excess of ∼1-3 GeV gamma rays from the region
surrounding the Galactic Center, consistent with the emission expected from annihilating dark
matter. We revisit and scrutinize this signal with the intention of further constraining its characteristics
and origin. By applying cuts to the Fermi event parameter CTBCORE, we suppress the tails
of the point spread function and generate high resolution gamma-ray maps, enabling us to more
easily separate the various gamma-ray components. Within these maps, we find the GeV excess
to be robust and highly statistically significant, with a spectrum, angular distribution, and overall
normalization that is in good agreement with that predicted by simple annihilating dark matter
models. For example, the signal is very well fit by a 36-51 GeV dark matter particle annihilating to
b
¯b with an annihilation cross section of σv = (1−3)×10−26 cm3
/s (normalized to a local dark matter
density of 0.4 GeV/cm3
). Furthermore, we confirm that the angular distribution of the excess is
approximately spherically symmetric and centered around the dynamical center of the Milky Way
(within ∼0.05◦
of Sgr A∗
), showing no sign of elongation along the Galactic Plane. The signal is
observed to extend to at least ' 10◦
from the Galactic Center, disfavoring the possibility that this
emission originates from millisecond pulsars.
We present long-baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of
the 870 m continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that
trace millimeter-sized particles down to spatial scales as small as 1 AU (20 mas). These data reveal
a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli
(1{6AU) with modest contrasts (5{30%). We associate these features with concentrations of solids
that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima.
No signicant non-axisymmetric structures are detected. Some of the observed features occur near
temperatures that may be associated with the condensation fronts of major volatile species, but the
relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the
so-called zonal
ows). Other features, particularly a narrow dark annulus located only 1 AU from the
star, could indicate interactions between the disk and young planets. These data signal that ordered
substructures on AU scales can be common, fundamental factors in disk evolution, and that high
resolution microwave imaging can help characterize them during the epoch of planet formation.
Keywords: protoplanetary disks | planet-disk interactions | stars: individual (TW Hydrae)
3d modeling of_gj1214b_atmosphere_formation_of_inhomogeneous_high_cloouds_and...Sérgio Sacani
Uma equipe de cientistas da Universidade de Washington e da Universidade de Toronto foram os primeiros a simular nuvens exóticas em 3D na atmosfera de um exoplaneta.
O objeto em questão, é o GJ 1214b, um exoplaneta chamado de mini-Netuno que foi descoberto, seis anos atrás pelos astrônomos no Harvard-Smithsonian Center for Astrophysics.
Também conhecido como Gliese 1214b, esse mundo tem cerca de 2.7 vezes o diâmetro da Terra e uma massa quase 7 vezes maior que a massa do nosso planeta. Ele está localizado a cerca de 52 anos-luz de distância na constelação de Ophiuchus.
O planeta orbita a estrela anã vermelha, GJ 1214, a cada 38 horas, a uma distância de 1.3 milhões de milhas.
De acordo com estudos prévios, o planeta tem uma atmosfera rica em água ou hidrogênio com extensas nuvens.
“Deve existir altas nuvens ou uma névoa orgânica na atmosfera – como nós observamos em Titã. Sua temperatura atmosférica excede o ponto de fusão da água”, disse o Dr. Benjamin Charnay, um dos membros da equipe da Universidade de Washington.
Evidence for the_thermal_sunyaev-zeldovich_effect_associated_with_quasar_feed...Sérgio Sacani
Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar
catalogue, spanning redshifts 0.5–3.5, we derive the mean millimetre and far-infrared
quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology
Telescope and Herschel-Spectral and Photometric Imaging REceiver data. We
constrain the form of the far-infrared emission and find 3σ–4σ evidence for the thermal
Sunyaev-Zel’dovich (SZ) effect, characteristic of a hot ionized gas component with
thermal energy (6.2 ± 1.7) × 1060 erg. This amount of thermal energy is greater than
expected assuming only hot gas in virial equilibrium with the dark matter haloes of
(1 − 5) × 1012h
−1M that these systems are expected to occupy, though the highest
quasar mass estimates found in the literature could explain a large fraction of this
energy. Our measurements are consistent with quasars depositing up to (14.5±3.3) τ
−1
8
per cent of their radiative energy into their circumgalactic environment if their typical
period of quasar activity is τ8 × 108 yr. For high quasar host masses, ∼ 1013h
−1M,
this percentage will be reduced. Furthermore, the uncertainty on this percentage is
only statistical and additional systematic uncertainties enter at the 40 per cent level.
The SEDs are dust dominated in all bands and we consider various models for dust
emission. While sufficiently complex dust models can obviate the SZ effect, the SZ
interpretation remains favoured at the 3σ–4σ level for most models.
Exocometary gas in_th_hd_181327_debris_ringSérgio Sacani
An increasing number of observations have shown that gaseous debris discs are not an
exception. However, until now we only knew of cases around A stars. Here we present the first
detection of 12CO (2-1) disc emission around an F star, HD 181327, obtained with ALMA
observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric
disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with
radiative transfer calculations we study the dust and CO mass distribution. We find the dust is
distributed in a ring with a radius of 86:0 0:4 AU and a radial width of 23:2 1:0 AU. At
this frequency the ring radius is smaller than in the optical, revealing grain size segregation
expected due to radiation pressure. We also report on the detection of low level continuum
emission beyond the main ring out to 200 AU. We model the CO emission in the non-LTE
regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging
between 1:2 10 6 M and 2:9 10 6 M, depending on the gas kinetic temperature and
collisional partners densities. The CO densities and location suggest a secondary origin, i.e.
released from icy planetesimals in the ring. We derive a CO cometary composition that is
consistent with Solar system comets. Due to the low gas densities it is unlikely that the gas is
shaping the dust distribution.
First emergence of cold accretion and supermassive star formation in the earl...Sérgio Sacani
We investigate the first emergence of the so-called cold accretion, the accretion flows deeply penetrating a halo, in the early
universe with cosmological N-body/SPH simulations. We study the structure of the accretion flow and its evolution within
small halos with . 108 M with sufficiently high spatial resolutions down to ∼ 1 pc scale. While previous studies only
follow the evolution for a short period after the primordial cloud collapse, we follow the long-term evolution until the cold
accretion first appears, employing the sink particle method. We show that the cold accretion emerges when the halo mass
exceeds ∼ 2.2×107 M {(1 + 𝑧) /15}
−3/2
, the minimum halo masses above which the accretion flow penetrates halos. We further
continue simulations to study whether the cold accretion provides the dense shock waves, which have been proposed to give
birth to supermassive stars (SMSs). We find that the accretion flow eventually hits a compact disc near the halo centre, creating
dense shocks over a wide area of the disc surface. The resulting post-shock gas becomes dense and hot enough with its mass
comparable to the Jeans mass 𝑀J ∼ 104−5 M, a sufficient amount to induce the gravitational collapse, leading to the SMS
formation.
JOURNEY OF THE UNIVERSE FROM BIRTH TO REBIRTH WITH INSIGHT INTO THE UNIFIED I...SURAJ KUMAR
In this paper it has been tried to propose a hypothesis for Universe life cycle from its birth to death along with a cyclic view into its rebirth referring to the concept of Cosmic Microwave Background Radiation, Spiral Structure of Galaxies and Spiral Structure of Elementary Particles. It has been tried to inherit the behaviour of Big Bang in consensus with the proposals of Steady State Cosmology within the vicinity of all modern ongoing researches. It also provides a unified approach for various force interactions of particles through the intrinsic behaviours of Spiral Structure of Elementary Particles. The inverse relation between mass of particle and rate of change of cross section of spiral arms gives us a distinct view of gravitational interactions. Also the orientation of the curl of spiral differentiate the electromagnetic interaction when has revolution and electroweak interaction when has rotational curl. Strong interaction can be described through the phase differences of particles with charge not in multiple of ½. This paper also describes the process for formation off composite particles and the atomic structure through various dynamics of interactions by spiral structured particles.
In this talk I explain (a) what observations speak
for the hypothesis of dark matter, (b) what observations speak for the hypothesis of modified gravity, and (c) why it is a mistake
to insist that either hypothesis on its own must explain all
the available data. The right explanation, I will argue,
is instead a suitable combination of dark matter and modified
gravity, which can be realized by the idea that dark matter
has a superfluid phase.
Big Bang Theory & Other Recent Sciences || 2014 - Dr. Mahbub Khaniqra tube
RECENT SCIENCES
Big Bang, Dark Matter, Dark Energy, Black Hole, Neutrino, God Particle, Higgs Field, Graviton, Expansion of Universe, and Search for Life elsewhere in the Cosmos
Fundamental principle of information to-energy conversion.Fausto Intilla
Abstract. - The equivalence of 1 bit of information to entropy was given by Landauer in 1961 as kln2, k the Boltzmann constant. Erasing information implies heat dissipation and the energy of 1 bit would then be (the
Landauer´s limit) kT ln 2, T being the ambient temperature. From a quantum-cosmological point of view the minimum quantum of energy in the universe corresponds today to a temperature of 10^-29 ºK, probably forming a cosmic background of a Bose condensate [1]. Then, the bit with minimum energy today in the Universe is a quantum of energy 10^-45 ergs, with an equivalent mass of 10^-66 g. Low temperature implies low energy per bit and, of course, this is the way for faster and less energy dissipating computing devices. Our conjecture is this: the possibility of a future access to the CBBC (a coupling/channeling?) would mean a huge
jump in the performance of these devices.
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.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
Remote Sensing and Computational, Evolutionary, Supercomputing, and Intellige...University of Maribor
Slides from talk:
Aleš Zamuda: Remote Sensing and Computational, Evolutionary, Supercomputing, and Intelligent Systems.
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Inter-Society Networking Panel GRSS/MTT-S/CIS Panel Session: Promoting Connection and Cooperation
https://www.etran.rs/2024/en/home-english/
Nucleophilic Addition of carbonyl compounds.pptxSSR02
Nucleophilic addition is the most important reaction of carbonyls. Not just aldehydes and ketones, but also carboxylic acid derivatives in general.
Carbonyls undergo addition reactions with a large range of nucleophiles.
Comparing the relative basicity of the nucleophile and the product is extremely helpful in determining how reversible the addition reaction is. Reactions with Grignards and hydrides are irreversible. Reactions with weak bases like halides and carboxylates generally don’t happen.
Electronic effects (inductive effects, electron donation) have a large impact on reactivity.
Large groups adjacent to the carbonyl will slow the rate of reaction.
Neutral nucleophiles can also add to carbonyls, although their additions are generally slower and more reversible. Acid catalysis is sometimes employed to increase the rate of addition.
ANAMOLOUS SECONDARY GROWTH IN DICOT ROOTS.pptxRASHMI M G
Abnormal or anomalous secondary growth in plants. It defines secondary growth as an increase in plant girth due to vascular cambium or cork cambium. Anomalous secondary growth does not follow the normal pattern of a single vascular cambium producing xylem internally and phloem externally.
DERIVATION OF MODIFIED BERNOULLI EQUATION WITH VISCOUS EFFECTS AND TERMINAL V...Wasswaderrick3
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LOW FREQUENCY GW SOURCES: Chapter II: Massive black hole binary cosmic evolution and dynamics - Alberto Sesana
1. LOW FREQUENCY GW
SOURCES:
Chapter II:
Massive black hole binary
cosmic evolution and dynamics
Alberto Sesana
(University of Birmingham)
2.
3. According to our best cosmological models, we live in a CDM UniverseCDM Universe. The energy
content of the Universe is 27% in the form of ordinary matter (~3% baryons, ~24% dark
matter) and 73% in the form of a cosmological constant (or Dark energy, or whatever),
which would be responsible of the accelerated expansion.
Cosmology in two slidesCosmology in two slides
4. The age of the Universe is ~14Gyr, during this time its size has expanded from a
singularity to ~1028
cm.
Usually cosmologists describe the epochs of the Universe in terms of redshift:
which describe how much the photons
emitted at a given time are redshifted,
because of the expansion, when they
arrive on the Earth.
The redshift of a photon is related to
the size of the Universe at the moment
of its emission through:
A given redshift correspond to a
specific time in the past:
z=0 today
z=1 ~8Gyr ago
z=6 ~13Gyr ago (age of the Universe
<1Gyr!)
5. Observational factsObservational facts
1- In all the cases where the inner core of a galaxy has been resolved (i.e.
In nearby galaxies), a massive black hole (MBH) has been found in the
center.
2- MBHs are believed to be the central engines of Quasars: the only viable
model to explain this cosmological objects is by means of gas accretion
onto a MBH.
3- Quasars have been discovered at z~7,
their inferred masses are ~109
solar masses!
THERE WERE 109
SOLAR MASS BHs
WHEN THE UNIVERSE WAS <1Gyr OLD!!!
Our aim is to understandOur aim is to understand
the MBH formation andthe MBH formation and
evolution and to assessevolution and to assess
the consequences for GWthe consequences for GW
astronomyastronomy
6.
7.
8.
9. Cosmological structure formationCosmological structure formation
The Universe after the Big Bang was not completely uniform
The matter content was (and is) dominated by dark matter. The ratio
dark matter/baryonic matter is ~10:1
Gravitational instabilities due to non uniform matter distribution cause
the matter to condense until small regions become gravitationally bound
These regions then decouple themselves from the global expansion
of the universe and collapse, forming what we call the first galactic
minihalos.
The baryonic matter feels the gravitational potential of these halos and
falls at their center, forming the first protogalaxies
This halos continuously form during the cosmic history and merge with
each other in what we call the hierarchical scenario for galaxy formation.
(Binney & Tremaine, 1987, chapter 9)
10. Halo formation: spherical collapseHalo formation: spherical collapse
Consider a flat, matter dominated Universe, and consider a region which
is slightly denser than the mean density.
The self-gravitational force of the sphere depends only on the matter
inside the sphere itself (Birkhoff's theorem), and the overdensity behaves
like a small closed Universe.
11. The typical halo mass is
an increasing function of
time: bottom-up or
HIERARCHICAL
structure formation!
The halo mass function
evolves in time (redshift)
with larger halos forming
at lower redshifts (later
times).
12. What happens to the baryons? In the early Universe most of the baryonic
matter is in form of hot atomic (H) or molecular (H2
) Hydrogen.
Baryons need to cool down (i.e.
loose energy) in order to condense
in dense structures and form
stars.
The only way to cool down is
through transition between
different atomic or molecular
levels.
We need to excite high energy
levels to radiate this energy away.
The only way is collisional
excitation: we need high
temperatures!!!
Atomic Hydrogen can cool only at
temperatures>104
K, while H2
can
cool already at 103
K.
13. The halo virial temperature is a function of the halo mass. At high z, we
need M>106
solar masses to cool H2
, and M>108
solar masses to cool H.
Such massive halos
correspond to high sigma
peaks of the density fluctuation
field (nevermind). This means
that are quite RARE!
BOTTOM LINE: BARION
CONDENSATION IS POSSIBLE
IN FAIRLY MASSIVE RARE
HALOS AT REDSHIFT ~20.
14. Heger & Woosley 2002
H2 cooling T=103
K z=30 MDM=106
M⊙
Subsonic collapse
No fragmentation
Formation of VMSs
Intermediate mass
seed BHs
Seed BH formation from POPIII stars
15. Seed BH formation from direct collapse
A seed BH can directly form following the collapse of a giant gas cloud.
Two problems:
1- you need to dissipate the angular momentum of the cloud
Angular momentum can halt the collapse when the rotational support
equals the gravitational binding energy
You need J~0, or an efficient way to dissipate J.
2- you need to avoid star formation
a-if you form stars you have less gas to feed the BH
b-stars are collisionless: you don't dissipate J efficiently anymore
c-supernovae blow away gas.
2
16. It turns out that both scenarios are viable, and form BH seeds in
relatively massive halos (107
-109
solar masses) at high redshift.
POPIII SCENARIO:
-seed BH mass~102
solar masses
-at redshift 15-20
DIRECT COLLAPSE SCENARIO:
-seed BH mass~104
-105
solar masses
-at redshift 15-10
17. HIERARCHICAL GALAXY EVOLUTION…
From De Lucia et al. 2006
According to the Hierarchical scenario, protogalaxies formed in the first
halos at high redshift merge feel each other gravitational attraction and
merge together to form the galaxies we see today in the local Universe
18.
19. ...+ MBH
- BULGE RELATIONS...
Massive black holes (MBHs) are ubiquitous in the galaxy centres.
In the last decade, tight relation have been discovered, correlating the
MBH mass with the host galaxy bulge mass (Magorrian et al. 1998) and with
the host bulge velocity dispersion (Gebhardt et al. 2000, Ferrarese & Merrit
2000). This relation are a clear hint of a
coevolution of MBHs and host galaxies.
20. GENERAL FRAMEWORK:
> The halo hierarchy can be traced
backwards by means of EPS Monte-Carlo
merger tree.
The semi-analytic code follows the
accretion and the dynamical history of
BHs in every single branch of the tree
The adopted threshold for density peaks
hosting a seed ensures an occupation
fraction of order unity today for halos
more massive than 1011
M
Z=0
Z=20
Binary merger trees starting at z=20
In a CDM cosmology
(Volonteri, Haardt & Madau 2003)
…= HIERARCHICAL MBH EVOLUTION
21. Accretion
During mergers, gravitational instabilities drive cold gas toward the galactic nucleus,
this gas can form a thin disk around the MBH, starting the accretion process.
Now consider a flux of proton with density being accreted onto a BH of mass M. The
accreting material emits radiation with a luminosity L. Equating the gravitational force
(acting on the accreting material) to the force due to the radiation pressure (exerted
by the outward radiation emitted by the accretion disk itself)
one found an equilibrium condition (in the spherical limit), which is commonly known
as Eddington accretion limit, described by the Eddington luminosity:
LEDD
=1.38X1038
erg/s for a solar mass BH and scales as the BH mass. A 109
solar mass
MBH shines with a luminosity of about 1047
erg/s (1014
Suns or 1000 MWs)!!!!!
This imply an accretion in mass given by:
MBHs CAN EFFICIENTLY
INCREASE THEIR MASS!!!!!!
22. Accretion
During mergers, gravitational instabilities drive cold gas toward the galactic nucleus,
this gas can form a thin disk around the MBH, starting the accretion process.
Now consider a flux of proton with density being accreted onto a BH of mass M. The
accreting material emits radiation with a luminosity L. Equating the gravitational force
(acting on the accreting material) to the force due to the radiation pressure (exerted
by the outward radiation emitted by the accretion disk itself)
one found an equilibrium condition (in the spherical limit), which is commonly known
as Eddington accretion limit, described by the Eddington luminosity:
LEDD
=1.38X1038
erg/s for a solar mass BH and scales as the BH mass. A 109
solar mass
MBH shines with a luminosity of about 1047
erg/s (1014
Suns or 1000 MWs)!!!!!
This imply an accretion in mass given by:
MBHs CAN EFFICIENTLY
INCREASE THEIR MASS!!!!!!
23. The natural timescale related to accretion is the Eddington timescale:
This defines the basic equation of mass growth via accretion
Although often set to 0.1, ε is in fact an important parameter that
depends on the spin. What is it?
β=3 for a Sch. BH, β=1 for a max spinning BH and prograde accretion.
The GR calculation gives
No problem accreting
MBHs to 109
solar
masses by z=0, but
what about z>7 QSOs?
24. Evidence that MBHs grow mostly via radiative efficient accretion comes
from the Soltan argument (1982).
By measuring the luminosity function of quasars, one can compute the
energy density due to the light emitted by accreting MBHs
An energy density corresponds to
an accreted mass density via
The luminosity function of quasars can be measured empirically so that
the estimate of the accreted mass density can be compared to the
current mass density in MBHs (which can be also measured):
About half quasars are obscured! Which brings the two estimates to
match quite well.
31. I-Dynamical friction: 10kpc-1pc
Consider a BH with mass MBH
moving with velocity V in a surrounding
distribution of field star with a density *
and a Maxwellian velocity
distribution with dispersion . The drag exerted by the stars on the BH is
given by:
- in the limit V->0 this force is proportional to V
- in the limito of V>> this force is proportional to 1/V2
- the drag is maximum for V=
In a gaseous medium the formula is similar:
but now is the gas speed of sound.
Again the drag is maximum when V=cs
, and is comparable to the stellar
case.
32. Dynamical friction is initially very efficient in shrinking the binary, but on
parsec scales the mechanism is no longer efficient:
BINARY STALLING? (Probably not)
From Milosavljevic & Merritt 2001
From Colpi & Dotti 2009
33. II-II-The hardening phase:The hardening phase:
““final parsec problem”. 1pc-0.01pcfinal parsec problem”. 1pc-0.01pc
Dynamical frictionDynamical friction is efficient in driving the two
BHs to a separation of the order
The ratio can be written as
GW emissionGW emission takes over at separation of the order
34. 3-body interactions3-body interactions
Y
X
Z
>> MBHB M1>M2 on a keplerian orbit with
semimajor axis a and eccentricity e
>> incoming star with m
*
<<M2 and velocity v
A star on a intersecting orbit receive a kick taking away from the binary
an amount of energy of the order .
This energy, and the relative angular momentum carried away, cam be
used to define dimensionless rate that describe the evolution of the
binary.
35. HARDENING RATE
Quinlan 1996
ECCENTRICITY GROWTH RATE
MASS EJECTION RATE
Hardening of the binaryHardening of the binary
This equations are derived in the approximation that the stellar
background DOES NOT CHANGE during the binary evolution!!!!
But ‘loss cone depletion’ is a potential problem (trlx
> TH
)
36. Reasonable agreement if the evolution is rescaled with ρ and σ at the
binary influence radius
AS & Khan 2015 (See also Vasiliev et al. 2015)
Compare:
-'realistic' mergers with N-body simulations
-semianalytic models including scattering of bound and unbound stars
37. The binary spends most of its
time at the transition separation
Assuming an isothermal sphere
and a simple M-sigma relation
Triaxiality of the merger remnant
keeps the ‘loss cone full’ and the
hardening rate ~constant
The evolution of the binary can be
simply obtained by combining
stellar and GW hardening
38. A MBHB In a merger remnant evolve as if it was immersed in
an homogeneous background of stars with with ρ and σ
taken at the influence radius of the merger remnant
We can then assume a Dehnen density profile
Connect the MBHB mass to the stellar mass via standard M-galaxy
relations; get the scale radius from observations
39. ...and compute the coalescence timescale for typical galaxy properties
as a function of the MBHB mass
Coalescence timescales
are fairly long:
*bending of GW spectrum
in the PTA band might not
be an issue unless binaries
gets very eccentric (might
be likely)
*Gyr coalescence timescale
open interesting scenarios
like triple interactions
40. Gas inflows with a constant
accretion rate. Its change in
angular momentum is
The binary acts as a dam
holding the gas at rgap
.
Therefore is injecting in the
disk an angular momentum
equal and opposite to the
above
Therefore the angular momentum
of the binary also evolve as
Using and assuming that the mass ratio does not change
one get the equation
The binary makes ~3 e-folds by accreting a mass
equal to mu. Assuming Eddington limited
accretion this happens in ~4 x 107
yrs. (Dotti+15)
Circumbinary disk-driven binariesCircumbinary disk-driven binaries