2 research outputs found
The evolution of the bi-modal colour distribution of galaxies in SDSS groups
We analyse colour distributions for several samples of galaxies in
groups drawn from the Fourth Data Release of the Sloan Digital Sky Survey. For
all luminosity ranges and environments considered the colour distributions are
well described by the sum of two Gaussian functions. We find that the fraction
of galaxies in the red sequence is an increasing function of group virial mass.
We also study the evolution of the galaxy colour distributions at low redshift,
in the field and in groups for galaxies brighter than
, finding significant evidence of recent evolution in the
population of galaxies in groups. The fraction of red galaxies monotonically
increases with decreasing redshift, this effect implies a much stronger
evolution of galaxies in groups than in the field.Comment: 7 pages, 6 figures, submited to MNRAS after minor revisio
Galactic conformity at few Mpc scales
The environment within dark matter haloes can quench the star formation of
galaxies. However, environmental effects beyond the virial radius of haloes
( 1 Mpc) are less evident. An example is the debated correlation
between colour or star formation in central galaxies and neighbour galaxies in
adjacent haloes at large separations of several Mpc, referred to as two-halo
galactic conformity. We use two galaxy catalogues generated from different
versions of the semi-analytic model SAG applied to the MDPL2 cosmological
simulation and the IllustrisTNG300 cosmological hydrodynamical simulation to
study the two-halo conformity by measuring the quenched fraction of
neighbouring galaxies as a function of the real-space distance from central
galaxies. We find that low-mass central galaxies in the vicinity of massive
systems ( 10 ) out to 5
Mpc are preferentially quenched compared to other central galaxies at
fixed stellar mass or fixed host halo mass at ~
0. In all the galaxies catalogues is consistent that the low-mass ( or ) central galaxies in the vicinity of groups and clusters of galaxies
mostly produce the two-halo galactic conformity. On average, the quenched
low-mass central galaxies are typically much closer to massive haloes than
star-forming central galaxies of the same mass (by a factor of ~5). Our results
support that the environmental influence of massive haloes can extend beyond
the virial radius and affect nearby low-mass central galaxies.Comment: 17 pages, 12 Figures. Submitted to MNRA