Properties of the circumgalactic medium in simulations compared to observations

Rubens E. G. Machado, Patricia B. Tissera, Gastão B. Lima Neto, Laerte Sodré Jr

Published 2017-10-24Version 1

Galaxies are surrounded by extended gaseous halos which store significant fractions of chemical elements. These are syntethized by the stellar populations and later ejected into the circumgalactic medium (CGM) by different mechanism, of which supernova feedback is considered one of the most relevant. We explore the properties of this metal reservoir surrounding star-forming galaxies in a cosmological context aiming to investigate the chemical loop between galaxies and their CGM, and the ability of the subgrid models to reproduce observational results. Using cosmological hydrodynamical simulations, we analyse the gas-phase chemical contents of galaxies with stellar masses in the range $10^{9} - 10^{11}\,{\rm M}_{\odot}$. We estimate the fractions of metals stored in the different CGM phases, and the predicted OVI and SiIII column densities within the virial radius. We find roughly $10^{7}\,{\rm M}_{\odot}$ of oxygen in the CGM of simulated galaxies having $M_{\star}{\sim}10^{10}\,{\rm M}_{\odot}$, in fair agreement with the lower limits imposed by observations. The $M_{\rm oxy}$ is found to correlate with $M_{\star}$, at odds with current observational trends but in agreement with other numerical results. The estimated profiles of OVI column density reveal a substantial shortage of that ion, whereas SiIII, which probes the cool phase, is overpredicted. The analysis of the relative contributions of both ions from the hot, warm and cool phases suggests that the warm gas ($ 10^5~{\rm K} < T < 10^6~{\rm K}$) should be more abundant in order to bridge the mismatch with the observations, or alternatively, that more metals should be stored in this gas-phase. Adittionally, we find that the X-ray coronae around the simulated galaxies have luminosities and temperatures in decent agreement with the available observational estimates. [abridged]