2014/09/30 by Michael E. Anderson, Massimo Gaspari, Simon D. M. White +2 · 1 citation
Physics and Astronomy · #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stv437
23 pages, 11 figures, accepted to MNRAS
arxiv created 2015/02/27 · arxiv updated 2015/06/23
We examine a sample of ∼ 250 000 "locally brightest galaxies" selected from the Sloan Digital Sky Survey to be central galaxies within their dark matter halos. These were previously stacked by the Planck Collaboration to measure the Sunyaev-Zel'dovich signal as a function of central galaxy stellar mass. Here, we stack the X-ray emission from these halos using data from the ROSAT All-Sky Survey. We detect emission across almost our entire sample, including emission which we attribute to hot gas around galaxies spanning a range of 1.2 dex in stellar mass (corresponding to nearly two orders of magnitude in halo mass) down to M* = 1010.8 M\odot (M500 ≈ 1012.6 M\odot). Over this range, the X-ray luminosity can be fit by a power-law, either of stellar mass or of halo mass. A single unified scaling relation between mass and LX applies for galaxies, groups, and clusters. This relation has a steeper slope than expected for self-similarity, in contrast to the YSZ-M500 relation, showing the importance of non-gravitational heating. If this heating is predominantly due to AGN feedback, the lack of a break in our relation suggests that AGN feedback is tightly self-regulated and fairly gentle, in agreement with recent high-resolution simulations. Our results are consistent with earlier measurements of the LX-LK relation for elliptical galaxies and of the LX-M500 relation for optically-selected galaxy clusters. However, our LX-M500 relation lies more than a factor of two below most previous relations based on X-ray-selected cluster samples. We argue that optical selection offers a less biased view of the LX-M500 relation.