88 research outputs found
PROVABGS: The Probabilistic Stellar Mass Function of the BGS One-percent Survey
We present the probabilistic stellar mass function (pSMF) of galaxies in the DESI Bright Galaxy Survey (BGS), observed during the One-percent Survey. The One-percent Survey was one of DESI’s survey validation programs conducted from 2021 April to May, before the start of the main survey. It used the same target selection and similar observing strategy as the main survey and successfully observed the spectra and redshifts of 143,017 galaxies in the r 100 × more galaxies. Moreover, we present the statistical framework for subsequent population statistics measurements using BGS, which will characterize the global galaxy population and scaling relations at low redshifts with unprecedented precision
PROVABGS: The Probabilistic Stellar Mass Function of the BGS One-Percent Survey
We present the probabilistic stellar mass function (pSMF) of galaxies in the
DESI Bright Galaxy Survey (BGS), observed during the One-Percent Survey. The
One-Percent Survey was one of DESI's survey validation programs conducted from
April to May 2021, before the start of the main survey. It used the same target
selection and similar observing strategy as the main survey and successfully
observed the spectra and redshifts of 143,017 galaxies in the
magnitude-limited BGS Bright sample and 95,499 galaxies in the fainter surface
brightness and color selected BGS Faint sample over . We derive pSMFs
from posteriors of stellar mass, , inferred from DESI photometry and
spectroscopy using the Hahn et al. (2022a; arXiv:2202.01809) PRObabilistic
Value-Added BGS (PROVABGS) Bayesian SED modeling framework. We use a
hierarchical population inference framework that statistically and rigorously
propagates the uncertainties. Furthermore, we include correction weights
that account for the selection effects and incompleteness of the BGS
observations. We present the redshift evolution of the pSMF in BGS as well as
the pSMFs of star-forming and quiescent galaxies classified using average
specific star formation rates from PROVABGS. Overall, the pSMFs show good
agreement with previous stellar mass function measurements in the literature.
Our pSMFs showcase the potential and statistical power of BGS, which in its
main survey will observe >100 more galaxies. Moreover, we present the
statistical framework for subsequent population statistics measurements using
BGS, which will characterize the global galaxy population and scaling relations
at low redshifts with unprecedented precision.Comment: 25 pages, 12 figures; data used to generate figures is available at
https://doi.org/10.5281/zenodo.8018936; submitted to Ap
DESI Observations of the Andromeda Galaxy: Revealing the Immigration History of our Nearest Neighbor
We present DESI observations of the inner halo of M31, which reveal the
kinematics of a recent merger - a galactic immigration event - in exquisite
detail. Of the 11,416 sources studied in 3.75 hour of on-sky exposure time,
7,438 are M31 sources with well measured radial velocities. The observations
reveal intricate coherent kinematic structure in the positions and velocities
of individual stars: streams, wedges, and chevrons. While hints of coherent
structures have been previously detected in M31, this is the first time they
have been seen with such detail and clarity in a galaxy beyond the Milky Way.
We find clear kinematic evidence for shell structures in the Giant Stellar
Stream, the Northeast Shelf and Western Shelf regions. The kinematics are
remarkably similar to the predictions of dynamical models constructed to
explain the spatial morphology of the inner halo. The results are consistent
with the interpretation that much of the substructure in the inner halo of M31
is produced by a single galactic immigration event 1 - 2 Gyr ago. Significant
numbers of metal-rich stars ([Fe/H]) are present in all of the detected
substructures, suggesting that the immigrating galaxy had an extended star
formation history. We also investigate the ability of the shells and Giant
Stellar Stream to constrain the gravitational potential of M31, and estimate
the mass within a projected radius of 125 kpc to be . The results herald a
new era in our ability to study stars on a galactic scale and the immigration
histories of galaxies.Comment: 45 pages, 22 figures, 8 tables; Astrophysical Journal in press; Data
at https://zenodo.org/record/697749
DESI Observations of the Andromeda Galaxy: Revealing the Immigration History of our Nearest Neighbor
The DESI One-Percent Survey: Exploring the Halo Occupation Distribution of Luminous Red Galaxies and Quasi-Stellar Objects with AbacusSummit
We present the first comprehensive Halo Occupation Distribution (HOD)
analysis of the DESI One-Percent survey Luminous Red Galaxy (LRG) and
Quasi-Stellar Object (QSO) samples. We constrain the HOD of each sample and
test possible HOD extensions by fitting the redshift-space galaxy 2-point
correlation functions in 0.15 < r < 32 Mpc/h in a set of fiducial redshift
bins. We use AbacusSummit cubic boxes at Planck 2018 cosmology as model
templates and forward model galaxy clustering with the AbacusHOD package. We
achieve good fits with a standard HOD model with velocity bias, and we find no
evidence for galaxy assembly bias or satellite profile modulation at the
current level of statistical uncertainty. For LRGs in 0.4 < z < 0.6, we infer a
satellite fraction of fsat = 11+-1%, a mean halo mass of log10 Mh =
13.40+0.02-0.02, and a linear bias of blin = 1.93+0.06-0.04. For LRGs in 0.6 <
z < 0.8, we find fsat = 14+-1%, log10 Mh = 13.24+0.02-0.02, and blin =
2.08+0.03-0.03. For QSOs, we infer fsat = 3+8-2%, log10 Mh = 12.65+0.09-0.04,
and blin = 2.63+0.37-0.26 in redshift range 0.8 < z < 2.1. Using these fits, we
generate a large suite of high-fidelity galaxy mocks. We also study the
redshift-evolution of the DESI LRG sample from z = 0.4 up to z = 1.1, revealing
significant and interesting trends in mean halo mass, linear bias, and
satellite fraction.Comment: Submitted to MNRAS, comments welcom
The DESI Bright Galaxy Survey: Final Target Selection, Design, and Validation
Over the next 5 yr, the Dark Energy Spectroscopic Instrument (DESI) will use 10 spectrographs with 5000 fibers on the 4 m Mayall Telescope at Kitt Peak National Observatory to conduct the first Stage IV dark energy galaxy survey. At z 10 million galaxies spanning 14,000 deg2 . In this work, we present and validate the final BGS target selection and survey design. From the Legacy Surveys, BGS will target an r 80% fiber assignment efficiency. Finally, BGS Bright and BGS Faint will achieve >95% redshift success over any observing condition. BGS meets the requirements for an extensive range of scientific applications. BGS will yield the most precise baryon acoustic oscillation and redshift-space distortion measurements at z < 0.4. It presents opportunities for new methods that require highly complete and dense samples (e.g., N-point statistics, multitracers). BGS further provides a powerful tool to study galaxy populations and the relations between galaxies and dark matter
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