An assessment of the "too big to fail" problem for field dwarf galaxies
  in view of baryonic feedback effects
  Recent studies have established that extreme dwarf galaxies --whether
satellites or field objects-- suffer from the so called "too big to fail"
(TBTF) problem. Put simply, the TBTF problem consists of the fact that it is
difficult to explain both the measured kinematics of dwarfs and their observed
number density within the LCDM framework. The most popular proposed solutions
to the problem involve baryonic feedback processes. For example, reionization
and baryon depletion can decrease the abundance of halos that are expected to
host dwarf galaxies. Moreover, feedback related to star formation can alter the
dark matter density profile in the central regions of low-mass halos. In this
article we assess the TBTF problem for field dwarfs, taking explicitly into
account the baryonic effects mentioned above. We find that 1) reionization
feedback cannot resolve the TBTF problem on its own, because the halos in
question are too massive to be affected by it, and that 2) the degree to which
profile modification can be invoked as a solution to the TBTF problem depends
on the radius at which galactic kinematics are measured. Based on a literature
sample of about 90 dwarfs with interferometric observations in the 21cm line of
atomic hydrogen (HI), we conclude that the TBTF problem persists despite
baryonic effects. However, the preceding statement assumes that the sample
under consideration is representative of the general population of field
dwarfs. In addition, the unexplained excess of dwarf galaxies in LCDM could be
as small as a factor of ~ 1.8, given the current uncertainties in the
measurement of the galactic velocity function. Both of these caveats highlight
the importance of upcoming uniform surveys with HI interferometers for
advancing our understanding of the issue.
