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Satellite Dwarf Galaxies in a Hierarchical Universe: Infall Histories, Group Preprocessing, and Reionization

Wetzel, Andrew R. and Deason, Alis J. and Garrison-Kimmel, Shea (2015) Satellite Dwarf Galaxies in a Hierarchical Universe: Infall Histories, Group Preprocessing, and Reionization. Astrophysical Journal, 807 (1). Art. No. 49 . ISSN 0004-637X.

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In the Local Group (LG), almost all satellite dwarf galaxies that are within the virial radius of the Milky Way (MW) and Andromeda (M31) exhibit strong environmental influence. The orbital histories of these satellites provide the key to understanding the role of the MW/M31 halo, lower-mass groups, and cosmic reionization on the evolution of dwarf galaxies. We examine the virial-infall histories of satellites with M_star = 10^(3-9) M_⊙ using the Exploring the Local Volume in Simulations suite of cosmological zoom-in dissipationless simulations of 48 MW/M31-like halos. Satellites at z = 0 fell into the MW/M31 halos typically 5-8 Gyr ago at z = 0.5-1. However, they first fell into any host halo typically 7-10 Gyr ago at z = 0.7-1.5. This difference arises because many satellites experienced “group preprocessing” in another host halo, typically of M_vir ~ 10^(10-12) M_⊙, before falling into the MW/M31 halos. Satellites with lower mass and/or those closer to the MW/M31 fell in earlier and are more likely to have experienced group preprocessing; half of all satellites with M_star < 10^6 M_⊙ were preprocessed in a group. Infalling groups also drive most satellite–satellite mergers within the MW/M31 halos. Finally, none of the surviving satellites at z = 0 were within the virial radius of their MW/M31 halo during reionization (z > 6), and only <4% were satellites of any other host halo during reionization. Thus, effects of cosmic reionization versus host-halo environment on the formation histories of surviving dwarf galaxies in the LG occurred at distinct epochs, separated typically by 2-4 Gyr, so they are separable theoretically and, in principle, observationally.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Wetzel, Andrew R.0000-0003-0603-8942
Deason, Alis J.0000-0001-6146-2645
Garrison-Kimmel, Shea0000-0002-4655-8128
Additional Information:© 2015 The American Astronomical Society. Received 29 December 2014; accepted for publication 20; April 2015; Published 30 June 2015. We thank the Aspen Center for Physics, supported in part by the National Science Foundation, for the hospitality and stimulating environment during the preparation of this paper. We thank Erik Tollerud, Dan Weisz, and Laura Sales for useful discussions. We also thank the anonymous reviewer for useful comments. A.R.W. gratefully acknowledges support from the Moore Center for Theoretical Cosmology and Physics at Caltech. A.J.D. is supported by NASA through Hubble Fellowship grant HST-HF-51302.01, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555.
Group:Moore Center for Theoretical Cosmology and Physics
Funding AgencyGrant Number
Caltech Moore Center for Theoretical Cosmology and PhysicsUNSPECIFIED
NASA Hubble FellowshipHST-HF-51302.01
Subject Keywords:cosmology: theory; galaxies: dwarf; galaxies: groups: general; galaxies: interactions; Local Group; methods: numerical
Issue or Number:1
Record Number:CaltechAUTHORS:20150820-102154818
Persistent URL:
Official Citation:Satellite Dwarf Galaxies in a Hierarchical Universe: Infall Histories, Group Preprocessing, and Reionization Andrew R. Wetzel et al. 2015 ApJ 807 49
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59787
Deposited By: Jason Perez
Deposited On:20 Aug 2015 21:46
Last Modified:09 Mar 2020 13:18

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