TY - JOUR
T1 - No assembly required
T2 - Mergers are mostly irrelevant for the growth of low-mass dwarf galaxies
AU - Fitts, Alex
AU - Boylan-Kolchin, Michael
AU - Bullock, James S.
AU - Weisz, Daniel R.
AU - El-Badry, Kareem
AU - Wheeler, Coral
AU - Faucher-Giguère, Claude André
AU - Quataert, Eliot
AU - Hopkins, Philip F.
AU - Kereš, Dušan
AU - Wetzel, Andrew
AU - Hayward, Christopher C.
N1 - Funding Information:
MBK and AF acknowledge support from the National Science Foundation (grant AST-1517226). MBK was also partially supported by NASA through HST grants AR-12836, AR-13888, AR- 13896, AR-14282, AR-14554, GO-12914, and GO-14191 awarded by the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555. JSB was supported by NSF AST-1518291, HST-AR-14282, and HST-AR- 13888. Support for PFH was provided by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, and NSF Collaborative Research Grant #1411920 and CAREER grant #1455342. CAFG was supported by NSF through grants AST- 1412836, AST-1517491, AST-1715216, and CAREER award AST- 1652522, and by NASA through grant NNX15AB22G. DRW is supported by a fellowship from the Alfred P. Sloan Foundation. EQ was supported by NASA ATP grant 12-APT12-0183, a Simons Investigator award from the Simons Foundation, and the David and Lucile Packard Foundation. DK was supported by NSF grant AST- 1715101 and the Cottrell Scholar Award from the Research Corporation for Science Advancement. AW was supported by a Caltech- Carnegie Fellowship, in part through theMoore Center for Theoretical Cosmology and Physics at Caltech, and by NASA through grant HST-GO-14734 from STScI. This work used computational resources of the University of Texas atAustin and the TexasAdvanced Computing Center (TACC; http://www.tacc.utexas.edu), the NASA Advanced Supercomputing (NAS) Division and the NASA Center for Climate Simulation (NCCS) through allocations SMD-15-5902, SMD-15-5904, SMD-16-7043, and SMD-16-6991, and the Extreme Science and Engineering Discovery Environment (XSEDE, via allocations TG-AST110035, TG-AST130039, and TG-AST140080), which is supported by National Science Foundation grant number OCI-1053575.
Funding Information:
MBK and AF acknowledge support from the National Science Foundation (grant AST-1517226). MBK was also partially supported by NASA through HST grants AR-12836, AR-13888, AR-13896, AR-14282, AR-14554, GO-12914, and GO-14191 awarded by the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555. JSB was supported by NSF AST-1518291, HST-AR-14282, and HST-AR-13888. Support for PFH was provided by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, and NSF Collaborative Research Grant #1411920 and CAREER grant #1455342. CAFG was supported by NSF through grants AST-1412836, AST-1517491, AST-1715216, and CAREER award AST-1652522, and by NASA through grant NNX15AB22G. DRW is supported by a fellowship from the Alfred P. Sloan Foundation. EQ was supported by NASA ATP grant 12-APT12-0183, a Simons Investigator award from the Simons Foundation, and the David and Lucile Packard Foundation. DK was supported by NSF grant AST-1715101 and the Cottrell Scholar Award from the Research Corporation for Science Advancement. AW was supported by a Caltech-Carnegie Fellowship, in part through the Moore Center for Theoretical Cosmology and Physics at Caltech, and by NASA through grant HST-GO-14734 from STScI. This work used computational re- sources of the University of Texas at Austin and the Texas Advanced Computing Center (TACC; http://www.tacc.utexas.edu), the NASA Advanced Supercomputing (NAS) Division and the NASA Center for Climate Simulation (NCCS) through allocations SMD-15-5902, SMD-15-5904, SMD-16-7043, and SMD-16-6991, and the Extreme Science and Engineering Discovery Environment (XSEDE, via allocations TG-AST110035, TG-AST130039, and TG-AST140080), which is supported by National Science Foundation grant number OCI-1053575.
Publisher Copyright:
© 2018 The Author(s). Published by Oxford University Press on behalf of The Royal Astronomical Society.
PY - 2018/9/1
Y1 - 2018/9/1
N2 - We investigate the merger histories of isolated dwarf galaxies based on a suite of 15 highresolution cosmological zoom-in simulations, all with masses of Mhalo ≈ 1010M⊙ (and M* ~ 105 - 107M⊙) at z= 0, from the Feedback in Realistic Environments project. The stellar populations of these dwarf galaxies at z= 0 are formed essentially entirely 'in situ': over 90 per cent of the stellar mass is formed in the main progenitor in all but two cases, and all 15 of the galaxies have > 70 per cent of their stellar mass formed in situ. Virtually all galaxy mergers occur prior to z~ 3, meaning that accreted stellar populations are ancient. On average, our simulated dwarfs undergo five galaxy mergers in their lifetimes, with typical pre-merger galaxy mass ratios that are less than 1:10. This merger frequency is generally comparable to what has been found in dissipationless simulations when coupled with abundance matching. Two of the simulated dwarfs have a luminous satellite companion at z= 0. These ultra-faint dwarfs lie at or below current detectability thresholds but are intriguing targets for nextgeneration facilities. The small contribution of accreted stars makes it extremely difficult to discern the effects of mergers in the vast majority of dwarfs either photometrically or using resolved-star colour-magnitude diagrams (CMDs). The important implication for near-field cosmology is that star formation histories (SFHs) of comparably massive galaxies derived from resolved CMDs should trace the build-up of stellar mass in one main system across cosmic time as opposed to reflecting the contributions of many individual SFHs of merged dwarfs.
AB - We investigate the merger histories of isolated dwarf galaxies based on a suite of 15 highresolution cosmological zoom-in simulations, all with masses of Mhalo ≈ 1010M⊙ (and M* ~ 105 - 107M⊙) at z= 0, from the Feedback in Realistic Environments project. The stellar populations of these dwarf galaxies at z= 0 are formed essentially entirely 'in situ': over 90 per cent of the stellar mass is formed in the main progenitor in all but two cases, and all 15 of the galaxies have > 70 per cent of their stellar mass formed in situ. Virtually all galaxy mergers occur prior to z~ 3, meaning that accreted stellar populations are ancient. On average, our simulated dwarfs undergo five galaxy mergers in their lifetimes, with typical pre-merger galaxy mass ratios that are less than 1:10. This merger frequency is generally comparable to what has been found in dissipationless simulations when coupled with abundance matching. Two of the simulated dwarfs have a luminous satellite companion at z= 0. These ultra-faint dwarfs lie at or below current detectability thresholds but are intriguing targets for nextgeneration facilities. The small contribution of accreted stars makes it extremely difficult to discern the effects of mergers in the vast majority of dwarfs either photometrically or using resolved-star colour-magnitude diagrams (CMDs). The important implication for near-field cosmology is that star formation histories (SFHs) of comparably massive galaxies derived from resolved CMDs should trace the build-up of stellar mass in one main system across cosmic time as opposed to reflecting the contributions of many individual SFHs of merged dwarfs.
KW - Dark matter
KW - Galaxies: dwarf
KW - Galaxies: evolution
KW - Galaxies: formation
KW - Galaxies: star formation
KW - Galaxies: structure
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U2 - 10.1093/mnras/sty1488
DO - 10.1093/mnras/sty1488
M3 - Article
AN - SCOPUS:85051564475
SN - 0035-8711
VL - 479
SP - 319
EP - 331
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 1
ER -