86 research outputs found
Measuring the growth rate of structure with Type IA Supernovae from LSST
We investigate measuring the peculiar motions of galaxies up to using
Type Ia supernovae (SNe Ia) from LSST, and predict the subsequent constraints
on the growth rate of structure. We consider two cases. Our first is based on
measurements of the volumetric SNe Ia rate and assumes we can obtain
spectroscopic redshifts and light curves for varying fractions of objects that
are detected pre-peak luminosity by LSST (some of which may be obtained by LSST
itself and others which would require additional follow-up). We find that these
measurements could produce growth rate constraints at that
significantly outperform those using Redshift Space Distortions (RSD) with DESI
or 4MOST, even though there are fewer objects. For our second
case, we use semi-analytic simulations and a prescription for the SNe Ia rate
as a function of stellar mass and star formation rate to predict the number of
LSST SNe IA whose host redshifts may already have been obtained with the
Taipan+WALLABY surveys, or with a future multi-object spectroscopic survey. We
find and SN Ia with host redshifts for these cases
respectively. Whilst this is only a fraction of the total LSST-detected SNe Ia,
they could be used to significantly augment and improve the growth rate
constraints compared to only RSD. Ultimately, we find that combining LSST SNe
Ia with large numbers of galaxy redshifts will provide the most powerful probe
of large scale gravity in the regime over the coming decades.Comment: 12 pages, 1 table, 5 figures. Accepted for publication in ApJ. The
Fisher matrix forecast code used in this paper can be found at:
https://github.com/CullanHowlett/PV_fisher. Updated to fix error in Eq. 1
(thanks to Eric Linder for pointing this out
Cosmic queuing: Galaxy satellites, building blocks and the hierarchical clustering paradigm
We study the properties of building blocks (BBs; i.e. accreted satellites) and surviving satellites of present-day galaxies using the semi-analytic model of galaxy formation SAG ('semi-analytic galaxies') in the context of a concordance Λ cold dark matter (ΛCDM) cosmology. We consider large number of dark matter (DM) halo merger trees spanning a wide range of masses (~1 × 1010-2.14 × 1015 M⊙). We find higher metallicities for BBs with respect to surviving satellites, an effect produced by the same processes behind the build up of the mass-metallicity relation. We prove that these metallicity differences arise from the higher peak height in the density fluctuation field occupied by BBs and central galaxies which have collapsed into a single object earlier than surviving satellites. BBs start to form stars earlier, during the peak 3/13/2011 ΛCDM, and build up half of their final stellar mass (measured at the moment of disruption) up to four times faster than surviving satellites. Surviving satellites keep increasing their stellar masses rather quiescently down to z ≃ 1. The difference between the metallicities of satellites, BBs and central galaxies depends on the host DM halo mass, in a way that can be used as a further test for the concordance cosmology.Facultad de Ciencias Astronómicas y GeofÃsica
The physical drivers of gas turbulence in simulated disc galaxies
We use the EAGLE cosmological simulations to study the evolution of the
vertical velocity dispersion of cold gas, , in central disc
galaxies and its connection to stellar feedback, gravitational instabilities,
cosmological gas accretion and galaxy mergers. To isolate the impact of
feedback, we analyse runs that turn off stellar and (or) AGN feedback in
addition to a run that includes both. The evolution of and its
dependence on stellar mass and star formation rate in EAGLE are in good
agreement with observations. Galaxies hosted by haloes of similar virial mass,
, have similar values even in runs where feedback is
absent. The prevalence of local instabilities in discs is uncorrelated with
at low redshift and becomes only weakly correlated at high redshifts
and in galaxies hosted by massive haloes. correlates most strongly
with the specific gas accretion rate onto the disc as well as with the degree
of misalignment between the inflowing gas and the disc's rotation axis. These
correlations are significant across all redshifts and halo masses, with
misaligned accretion being the primary driver of high gas turbulence at
redshifts and for halo masses . Galaxy mergers increase , but because they are rare in
our sample, they play only a minor role in its evolution. Our results suggest
that the turbulence of cold gas in EAGLE discs results from a complex interplay
of different physical processes whose relative importance depends on halo mass
and redshift.Comment: 22 pages, 12 figures. Accepted for publication in MNRA
Exploring binary black hole mergers and host galaxies with {\sc Shark} and COMPAS
In this work, we explore the connection between the gravitational wave (GW)
merger rates of stellar-mass binary black holes (BBH) and galaxy properties. We
do this by generating populations of stars using the binary synthesis code
COMPAS and evolving them in galaxies from the semi-analytic galaxy formation
model {\sc Shark}, to determine the number of mergers occurring in each
simulation time-step. We find that large, metal-rich galaxies with high star
formation rates are more likely to have gravitational wave (GW) events compared
to younger, more metal poor galaxies. Our simulation with the default input
parameters predicts a higher local merger rate density compared to the third
gravitational wave transient catalogue (GWTC-3) prediction from LIGO, VIRGO and
KAGRA. This is due to short coalescence times, low metallicities and an high
formation rate of stars at low redshift in the galaxy simulation, which
produces more BBHs that merge within the age of the Universe compared to
observations. We identify alternate remnant mass models that more accurately
reproduce the observed volumetric rate and provide updated fits to the merger
rate distribution as a function of redshift. We then investigate the relative
fraction of GW events in our simulation volume that are in observable host
galaxies from different upcoming photometric and spectroscopic surveys,
determining which of those are more ideal for tracing host galaxies with high
merger rates. The implications of this work can be utilised for numerous
applications, including for constraining stellar evolution models, better
informing follow-up programs, and placing more informative priors on potential
host galaxies when measuring cosmological parameters such as the Hubble
constant.Comment: 19 pages, 16 figures - Will be submitted to MNRA
Identifying the disc, bulge, and intra-halo light of simulated galaxies through structural decomposition
We perform a structural decomposition of galaxies identified in three
cosmological hydrodynamical simulations by applying Gaussian Mixture Models
(GMMs) to the kinematics of their stellar particles. We study the resulting
disc, bulge, and intra-halo light (IHL) components of galaxies whose host dark
matter haloes have virial masses in the range --
. Our decomposition technique isolates galactic discs
whose mass fractions, , correlate strongly with common
alternative morphology indicators; for example, is approximately
equal to , the fraction of stellar kinetic energy in
co-rotation. The primary aim of our study, however, is to characterise the IHL
of galaxies in a consistent manner and over a broad mass range, and to analyse
its properties from the scale of galactic stellar haloes up to the
intra-cluster light. Our results imply that the IHL fraction, ,
has appreciable scatter and is strongly correlated with galaxy morphology: at
fixed stellar mass, the IHL of disc galaxies is typically older and less
massive than that of spheroids. Above ,
we find, on average, , albeit with considerable
scatter. The transition radius beyond which the IHL dominates the stellar mass
of a galaxy is roughly for , but increases strongly towards higher masses. However, we find that
no alternative IHL definitions -- whether based on the ex-situ stellar
fraction, or the stellar mass outside a spherical aperture -- reproduce our
dynamically-defined IHL fractions.Comment: 17 pages, 12 figures, submitted to MNRA
Dynamic equilibrium sets atomic content of galaxies across cosmic time
We analyze 88 independent high-resolution cosmological zoom-in simulations of
disk galaxies in the NIHAO simulations suite to explore the connection between
the atomic gas fraction and angular momentum of baryons throughout cosmic time.
The study is motivated by the analytic model of \citet{obreschkow16}, which
predicts a relation between the atomic gas fraction and the
global atomic stability parameter , where and
are the mass and specific angular momentum of the galaxy (stars+cold gas) and
is the velocity dispersion of the atomic gas. We show that the
simulated galaxies follow this relation from their formation () to
present within dex. To explain this behavior, we explore the
evolution of the local Toomre stability and find that -- of the
atomic gas in all simulated galaxies is stable at any time. In other words,
throughout the entire epoch of peak star formation until today, the timescale
for accretion is longer than the timescale to reach equilibrium, thus resulting
in a quasi-static equilibrium of atomic gas at any time. Hence, the evolution
of depends on the complex hierarchical growth history primarily
via the evolution of . An exception are galaxies subject to strong
environmental effects.Comment: 12 pages, 7 figures; accepted to Ap
Host galaxy-active galactic nucleus alignments in the Sloan Digital Sky Survey Data Release 7
We determine the intrinsic shapes and orientations of 27450 types I and II active galactic nucleus (AGN) galaxies in the spectroscopic sample of the Sloan Digital Sky Survey Data Release 7 by studying the distribution of projected axial ratios of AGN hosts. Our aim is to study possible alignments between the AGN and host galaxy systems (e.g. the accretion disc and the galaxy angular momentum) and the effect of dust obscuration geometry on the AGN type. We define control samples of non-AGN galaxies that mimic the morphology, colour, luminosity and concentration distributions of the AGN population, taking into account the effects of dust extinction and reddening. Assuming that AGN galaxies have the same underlying 3D shape distribution as their corresponding control samples, we find that the spiral and elliptical type I AGN populations are strongly skewed towards face-on galaxies, while elliptical and spiral type II AGN populations are skewed towards edge-on orientations. These findings rule out random orientations for AGN hosts at high confidence for type I spirals (δχ2≈ 230) and type II ellipticals (δχ2≈ 15), while the signal for type I ellipticals and type II spirals is weaker (δχ2≈ 3 and ≈6, respectively). We obtain a much stronger tendency for the type II spirals to be edge-on when just high [O III] equivalent width (EW) AGN are considered, suggesting that >20 per cent of low [O III] EW edge-on type II AGN may be missing from the optical sample. Galactic dust absorption of the broad-line region alone cannot explain the observed inclination angle and projected axial ratio distributions of types I and II Seyfert galaxies, implying that obscuration by a small-scale circumnuclear torus is necessary. These results favour a scenario in which the angular momentum of the material which feeds the black hole retains a memory of its original gas source at least to some small, non-negligible degree.Facultad de Ciencias Astronómicas y GeofÃsicasInstituto de AstrofÃsica de La Plat
Host galaxy-active galactic nucleus alignments in the Sloan Digital Sky Survey Data Release 7
We determine the intrinsic shapes and orientations of 27450 types I and II active galactic nucleus (AGN) galaxies in the spectroscopic sample of the Sloan Digital Sky Survey Data Release 7 by studying the distribution of projected axial ratios of AGN hosts. Our aim is to study possible alignments between the AGN and host galaxy systems (e.g. the accretion disc and the galaxy angular momentum) and the effect of dust obscuration geometry on the AGN type. We define control samples of non-AGN galaxies that mimic the morphology, colour, luminosity and concentration distributions of the AGN population, taking into account the effects of dust extinction and reddening. Assuming that AGN galaxies have the same underlying 3D shape distribution as their corresponding control samples, we find that the spiral and elliptical type I AGN populations are strongly skewed towards face-on galaxies, while elliptical and spiral type II AGN populations are skewed towards edge-on orientations. These findings rule out random orientations for AGN hosts at high confidence for type I spirals (δχ2≈ 230) and type II ellipticals (δχ2≈ 15), while the signal for type I ellipticals and type II spirals is weaker (δχ2≈ 3 and ≈6, respectively). We obtain a much stronger tendency for the type II spirals to be edge-on when just high [O III] equivalent width (EW) AGN are considered, suggesting that >20 per cent of low [O III] EW edge-on type II AGN may be missing from the optical sample. Galactic dust absorption of the broad-line region alone cannot explain the observed inclination angle and projected axial ratio distributions of types I and II Seyfert galaxies, implying that obscuration by a small-scale circumnuclear torus is necessary. These results favour a scenario in which the angular momentum of the material which feeds the black hole retains a memory of its original gas source at least to some small, non-negligible degree.Facultad de Ciencias Astronómicas y GeofÃsicasInstituto de AstrofÃsica de La Plat
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