132 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
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
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