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A quantitative explanation of the observed population of Milky Way satellite galaxies | | Sergey E. Koposov
; Jaiyul Yoo
; Hans-Walter Rix
; David H. Weinberg
; Andrea V. Macciò
; Jordi Miralda-Escudé
; | | Date: |
14 Jan 2009 | | Abstract: | We revisit the well known discrepancy between the observed number of Milky
Way (MW) dwarf satellite companions and the predicted population of cold dark
matter (CDM) sub-halos, in light of the dozen new low luminosity satellites
found in SDSS imaging data and our recent calibration of the SDSS satellite
detection efficiency, which implies a total population far larger than these
dozen discoveries. We combine a dynamical model for the CDM sub-halo population
with simple, physically motivated prescriptions for assigning stellar content
to each sub-halo, then apply observational selection effects and compare to the
current observational census. As expected, models in which the stellar mass is
a constant fraction F(Omega_b/Omega_m) of the sub-halo mass M_sat at the time
it becomes a satellite fail for any choice of F. However, previously advocated
models that invoke suppression of gas accretion after reionization in halos
with circular velocity v_c <~ 35 km/s can reproduce the observed satellite
counts for -15 < M_V < 0, with F ~ 10^{-3}. Successful models also require
strong suppression of star formation BEFORE reionization in halos with v_c <~
10 km/s; models without pre-reionization suppression predict far too many
satellites with -5 < M_V < 0. Our models also reproduce the observed stellar
velocity dispersions ~ 5-10 km/s of the SDSS dwarfs given the observed sizes of
their stellar distributions, and model satellites have M(<300 pc) ~ 10^7 M_sun
as observed even though their present day total halo masses span more than two
orders of magnitude. Our modeling shows that natural physical mechanisms acting
within the CDM framework can quantitatively explain the properties of the MW
satellite population as it is presently known, thus providing a convincing
solution to the ’missing satellite’ problem. | | Source: | arXiv, 0901.2116 | | Services: | Forum | Review | PDF | Favorites | |
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