Organized chaos: scatter in the relation between stellar mass and halo mass in small galaxies

We use Local Group galaxy counts together with the ELVIS N-body simulations to explore the relationship between the scatter and slope in the stellar mass versus halo mass relation at low masses, M... 10 super( 5)-10 super( 8) M... Assuming models with lognormal scatter about a median relation of the...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2017-01, Vol.464 (3), p.3108-3108
Main Authors: Garrison-Kimmel, Shea, Bullock, James S, Boylan-Kolchin, Michael, Bardwell, Emma
Format: Article
Language:English
Subjects:
Astronomy
Comparative analysis
Correlation analysis
Counting
Dwarf stars
Galactic halos
Galaxies
Halos
Mathematical models
Scatter
Simulation
Star & galaxy formation
Stellar mass
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Summary:We use Local Group galaxy counts together with the ELVIS N-body simulations to explore the relationship between the scatter and slope in the stellar mass versus halo mass relation at low masses, M... 10 super( 5)-10 super( 8) M... Assuming models with lognormal scatter about a median relation of the form M... M..., the preferred log-slope steepens from a ... 1.8 in the limit of zero scatter to a ... 2.6 in the case of 2 dex of scatter in M... at fixed halo mass. We provide fitting functions for the best-fitting relations as a function of scatter, including cases where the relation becomes increasingly stochastic with decreasing mass. We show that if the scatter at fixed halo mass is large enough (... 1 dex) and if the median relation is steep enough (a ... 2), then the 'too-big-to-fail' problem seen in the Local Group can be self-consistently eliminated in about ~5-10 per cent of realizations. This scenario requires that the most massive subhaloes host unobservable ultra-faint dwarfs fairly often; we discuss potentially observable signatures of these systems. Finally, we compare our derived constraints to recent high-resolution simulations of dwarf galaxy formation in the literature. Though simulation-to-simulation scatter in M... at fixed Mhalo is large among different authors (~2 dex), individual codes produce relations with much less scatter and usually give relations that would overproduce local galaxy counts. (ProQuest: ... denotes formulae/symbols omitted.)
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stw2564