Unifying X-ray scaling relations from galaxies to clusters
Abstract
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 haloes. We stack the X-ray emission from these haloes, as a function of the stellar mass of the central galaxy, 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⊙ (M500 ≈ 1012.6 M⊙). Over this range, the X-ray luminosity can be fit by a power law, either of stellar mass or of halo mass. From this, we infer a single unified scaling relation between mass and LX which applies for galaxies, groups, and clusters. This relation has a slope steeper than expected for self-similarity, showing the importance of non-gravitational heating. Assuming this non-gravitational heating is predominately due to AGN feedback, the lack of a break in the relation shows that AGN feedback is tightly self-regulated and fairly gentle, in agreement with the predictions of recent high-resolution simulations. Our relation is consistent with established measurements of the LX-LK relation for elliptical galaxies as well as the LX-M500 relation for optically selected galaxy clusters. However, our LX-M500 relation has a normalization more than a factor of 2 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 for mass-selected clusters.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- June 2015
- DOI:
- 10.1093/mnras/stv437
- arXiv:
- arXiv:1409.6965
- Bibcode:
- 2015MNRAS.449.3806A
- Keywords:
-
- galaxies: clusters: general;
- galaxies: groups: general;
- galaxies: haloes;
- X-rays: galaxies;
- X-rays: galaxies: clusters;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 23 pages, 11 figures, accepted to MNRAS