http://arxiv.org/abs/1712.02797
Galactic conformity is the phenomenon whereby galaxy properties exhibit larger correlations across distance than what would be expected if these properties only depended on halo mass. We perform a comprehensive study of conformity at low redshift using a galaxy group catalogue from the SDSS DR7 spectroscopic sample. We study correlations both between central galaxies and their satellites (1-halo conformity), and between central galaxies in separate haloes (2-halo conformity). We use two statistics, quenched fractions and the marked correlation function, to probe for conformity in three galaxy properties, $(g-r)$ colour, specific star formation rate, and S\’ersic index. We assess the statistical significance of conformity signals with a suite of mock galaxy catalogues that have no built-in conformity, but contain the same group-finding and mass assignment errors as the real data. In the case of 1-halo conformity, quenched fractions show strong signals at all group masses. However, these signals are equally strong in our mock catalogues, indicating that the conformity signal is spurious and likely entirely caused by systematic errors from group-finding. This result calls into question previous claims of 1-halo conformity detection. The marked correlation function reveals a significant detection of radial segregation within massive groups, but no evidence of conformity. In the case of 2-halo conformity, quenched fractions show no significant evidence of conformity once compared with our mock catalogues, in agreement with recent studies that have cast doubt on the validity of past detections. In contrast, the marked correlation function reveals a highly significant signal in low mass groups for scales of 0.8-4 $h^{-1}\textrm{Mpc}$, possibly representing the first robust detection of 2-halo conformity.
V. Calderon, A. Berlind and M. Sinha
Mon, 11 Dec 17
14/62
Comments: 18 pages, 8 figures, submitted to MNRAS