The diversity of the circumgalactic medium around z = 0 Milky Way-mass galaxies from the Auriga simulations. Issue 1 (21st June 2019)

• Record Type: Journal Article
• Authors: Hani, Maan H; Ellison, Sara L; Sparre, Martin; Grand, Robert J J; Pakmor, Rüediger; Gomez, Facundo A; Springel, Volker
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 488:Issue 1(2019)
• Page Start: 135
• Page End: 152
• Publication Date: 2019-06-21
• Subjects: methods: numerical -- galaxies: evolution -- galaxies: haloes; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz1708
• Languages: English
• ISSNs: 0035-8711

Abstract

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 ${\sim } 5$ to $90{{\ \rm per\ cent}}$ . 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.