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An analysis of the evolving comoving number density of galaxies in hydrodynamical simulations

Torrey, Paul and Wellons, Sarah and Machado, Francisco and Griffen, Brendan and Nelson, Dylan and Rodriguez-Gomez, Vicente and McKinnon, Ryan and Pillepich, Annalisa and Ma, Chung-Pei and Vogelsberger, Mark and Springel, Volker and Hernquist, Lars (2015) An analysis of the evolving comoving number density of galaxies in hydrodynamical simulations. Monthly Notices of the Royal Astronomical Society, 454 (3). pp. 2770-2786. ISSN 0035-8711.

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We present an analysis of the evolving comoving cumulative number density of galaxy populations found in the Illustris simulation. Cumulative number density is commonly used to link galaxy populations across different epochs by assuming that galaxies preserve their number density in time. Our analysis allows us to examine the extent to which this assumption holds in the presence of galaxy mergers or when rank ordering is broken owing to variable stellar growth rates. Our primary results are as follows: (1) the inferred average stellar mass evolution obtained via a constant comoving number density assumption is systematically biased compared to the merger tree results at the factor of ∼2(4) level when tracking galaxies from redshift z = 0 to 2(3); (2) the median number density evolution for galaxy populations tracked forward in time is shallower than for galaxy populations tracked backward; (3) a similar evolution in the median number density of tracked galaxy populations is found regardless of whether number density is assigned via stellar mass, stellar velocity dispersion, or halo mass; (4) explicit tracking reveals a large diversity in the stellar and dark matter assembly histories that cannot be captured by constant number density analyses; (5) the significant scatter in galaxy linking methods is only marginally reduced (∼20 per cent) by considering additional physical galaxy properties. We provide fits for the median evolution in number density for use with observational data and discuss the implications of our analysis for interpreting multi-epoch galaxy property observations.

Item Type:Article
Related URLs:
URLURL TypeDescription
Torrey, Paul0000-0002-5653-0786
Rodriguez-Gomez, Vicente0000-0002-9495-0079
Pillepich, Annalisa0000-0003-1065-9274
Vogelsberger, Mark0000-0001-8593-7692
Springel, Volker0000-0001-5976-4599
Hernquist, Lars0000-0001-6950-1629
Additional Information:© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 August 21. Received 2015 August 17; in original form 2015 July 8. First published online October 14, 2015. We thank the anonymous referee for the careful reading of our manuscript and the valuable comments that have improved the paper. PT acknowledges support from NASA ATP Grant NNX14AH35G. SW is supported by the National Science Foundation Graduate Research Fellowship under grant number DGE1144152. FM acknowledges support from the MIT UROP program. RM acknowledges support from the DOE CSGF under grant number DE-FG02-97ER25308. AP acknowledges support from the HST grant HST-AR-13897. Support for C-PM is provided in part by the Miller Institute for Basic Research in Science, University of California Berkeley. VS acknowledges support by the DFG Research Centre SFB-881 The Milky Way System through project A1, and by the European Research Council under ERC-StG EXAGAL-308037. LH acknowledges support from NASA grant NNX12AC67G and NSF grant AST-1312095. The Illustris-1 simulation was run on the CURIE supercomputer at CEA/France as part of PRACE project RA0844, and the SuperMUC computer at the Leibniz Computing Centre, Germany, as part of GCS-project pr85je. The further simulations were run on the Harvard Odyssey and CfA/ITC clusters, the Ranger and Stampede supercomputers at the Texas Advanced Computing Center through XSEDE, and the Kraken supercomputer at Oak Ridge National Laboratory through XSEDE. The analysis presented in this paper was conducted on the joint MIT-Harvard computing cluster supported by MKI and FAS.
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1144152
Massachusetts Institute of Technology (MIT)UNSPECIFIED
Department of Energy (DOE)DE-FG02-97ER25308
Miller Institute for Basic Research in ScienceUNSPECIFIED
Deutsche Forschungsgemeinschaft (DFG)SFB-881
European Research Council (ERC)EXAGAL-308037
Harvard UniversityUNSPECIFIED
Subject Keywords:methods: numerical – galaxies: abundances – cosmology: theory
Issue or Number:3
Record Number:CaltechAUTHORS:20160205-135035111
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Official Citation:Paul Torrey, Sarah Wellons, Francisco Machado, Brendan Griffen, Dylan Nelson, Vicente Rodriguez-Gomez, Ryan McKinnon, Annalisa Pillepich, Chung-Pei Ma, Mark Vogelsberger, Volker Springel, and Lars Hernquist An analysis of the evolving comoving number density of galaxies in hydrodynamical simulations MNRAS (December 11, 2015) Vol. 454 2770-2786 doi:10.1093/mnras/stv1986 First published online October 14, 2015
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64283
Deposited By: George Porter
Deposited On:08 Feb 2016 18:44
Last Modified:09 Mar 2020 13:19

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