The diversity of the circumgalactic medium around z = 0 Milky Way-mass galaxies from the Auriga simulations
Abstract
Galaxies are surrounded by massive gas reservoirs (i.e. the circumgalactic medium; CGM) which play a key role in their evolution. The properties of the CGM, which are dependent on a variety of internal and environmental factors, are often inferred from absorption line surveys which rely on a limited number of single lines-of-sight. In this work we present an analysis of 28 galaxy haloes selected from the Auriga project, a cosmological magneto-hydrodynamical zoom-in simulation suite of isolated Milky Way-mass galaxies, to understand the impact of CGM diversity on observational studies. Although the Auriga haloes are selected to populate a narrow range in halo mass, our work demonstrates that the CGM of L⋆ galaxies is extremely diverse: column densities of commonly observed species span ∼3 - 4 dex and their covering fractions range from {∼ } 5 to 90{{ per cent}}. Despite this diversity, we identify the following correlations: 1) the covering fractions (CF) of hydrogen and metals of the Auriga haloes positively correlate with stellar mass, 2) the CF of H I, C IV, and Si II anticorrelate with active galactic nucleus luminosity due to ionization effects, and 3) the CF of H I, C IV, and Si II positively correlate with galaxy disc fraction due to outflows populating the CGM with cool and dense gas. The Auriga sample demonstrates striking diversity within the CGM of L⋆ galaxies, which poses a challenge for observations reconstructing CGM characteristics from limited samples, and also indicates that long-term merger assembly history and recent star formation are not the dominant sculptors of the CGM.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- September 2019
- DOI:
- 10.1093/mnras/stz1708
- arXiv:
- arXiv:1907.04336
- Bibcode:
- 2019MNRAS.488..135H
- Keywords:
-
- methods: numerical;
- galaxies: evolution;
- galaxies: haloes;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Monthly Notices of the Royal Astronomical Society 488 (2019) 135-152