The distinct stellar-to-halo mass relations of satellite and central
  galaxies: insights from the IllustrisTNG simulations
  We study the stellar-to-halo mass relation (SHMR) for central and satellite
galaxies with total dynamical masses above 10^10.5 Msun using the suite of
cosmological magneto-hydrodynamical simulations IllustrisTNG. In particular, we
quantify environmental effects on satellite populations from TNG50, TNG100, and
TNG300 located within the virial radius of group- and cluster-like hosts with
total masses of 10^12-15.2 Msun. At fixed stellar mass, the satellite SHMR
exhibits a distinct shift towards lower dynamical mass compared to the SHMR of
centrals. Conversely, at fixed dynamical mass, satellite galaxies appear to
have larger stellar-to-total mass fractions than centrals by up to a factor of
a few. The systematic deviation from the central SHMR is larger for satellites
in more massive hosts, at smaller cluster-centric distances, with earlier
infall times, and that inhabit higher local density environments; moreover, it
is in place already at early times (z < 2). Systematic environmental effects
might contribute to the perceived galaxy-to-galaxy variation in the measured
SHMR when galaxies cannot be separated into satellites and centrals. The SHMR
of satellites exhibits a larger scatter than centrals, over the whole range of
dynamical mass (by up to 0.8 dex). The shift of the satellite SHMR results
mostly from tidal stripping of their dark matter, which affects satellites in
an outside-in fashion: the departure of the satellite SHMR from the centrals'
relation diminishes for measurements of dynamical mass in progressively smaller
apertures. Finally, we provide a family of fitting functions for the SHMR
predicted by IllustrisTNG.
