Colour and infall time distributions of satellite galaxies in simulated Milky-Way analogs

Kavli Affiliate: Andrey Kravtsov

| First 5 Authors: Yue Pan, Christine M. Simpson, Andrey Kravtsov, Facundo A. Gómez, Robert J. J. Grand

| Summary:

We compare here the colours of simulated satellite galaxies from the Auriga
project to observed satellite galaxies from the Exploration of Local VolumE
Satellites (ELVES) Survey of satellite galaxies around local Milky Way
analogues. Our goal is to understand the origin of the observed colour
distribution and star-forming properties of ELVES satellites. We find that the
satellite populations in the Auriga simulations, which was originally designed
to model Milky Way-like host galaxies, resemble the populations in ELVES in
their luminosity function, quenched fraction, and colour-magnitude
distribution. We find that satellites transition from blue colours to red
colours at the luminosity range $-15 lesssim M_g lesssim -12$ in both the
simulations and observations and we show that this shift is driven by
environmental effects in the simulations. We also demonstrate that the colour
distribution in both simulations and observations can be decomposed into two
populations based on their morphological type or star-forming status that are
statistically distinct. In the simulations, these two populations also have
statistically distinct infall time distributions. The transition in
star-forming state appears to be consistent between Auriga and ELVES but in
contrast with the Satellites Around Galactic Analogs (SAGA) survey. The
comparison presented here seems to indicate that this tension is resolved by
the improved target selection of ELVES, but there are still tensions in
understanding the colours of faint galaxies, of which ELVES appears to have a
significant population of faint blue satellites not recovered in Auriga.

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