Diffuse X-ray emission from star forming galaxies

Abstract

We study the diffuse X-ray luminosity ($L_X$) of star forming galaxies using 2-D axisymmetric hydrodynamical simulations and analytical considerations of supernovae (SNe) driven galactic outflows. We find that the mass loading of the outflows, a crucial parameter for determining the X-ray luminosity, is constrained by the availability of gas in the central star forming region, and a competition between cooling and expansion. We show that the allowed range of the mass loading factor can explain the observed scaling of $L_X$ with star formation rate (SFR) as $L_X\propto$ SFR${}^2$ for SFR $\gtrsim 1$ M${}_{\odot }$yr${}^{-1}$, and a flatter relation at low SFRs. We also show that the emission from the hot circumgalactic medium (CGM) in the halo of massive galaxies can explain the sub-linear behaviour of the $L_X-$SFR relation as well as a large scatter in the diffuse X-ray emission for low SFRs ($\lesssim$ few M${}_{\odot }$yr${}^{-1}$). Our results point out that galaxies with small SFRs and large diffuse X-ray luminosities are excellent candidates for detection of the elusive CGM.

5 pages, 4 figures, Accepted for publication in ApJL

References in corpus (6)

• PLUTO: a Numerical Code for Computational Astrophysics
• The COS-Halos Survey: Physical Conditions and Baryonic Mass in the Low-Redshift Circumgalactic Medium
• The COS-Dwarfs Survey: The Carbon Reservoir Around sub-L* Galaxies
• Iron line and diffuse hard X-ray emission from the starburst galaxy M82
• Long way to go: how outflows from large galaxies propagate through the hot halo gas
• CMB distortion from circumgalactic gas

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• Self-ionizing galactic winds
• Interactions between Ultra-High-Energy Particles and Protogalactic Environments
• Interaction of the Galactic-Centre Super Bubbles with the Gaseous Disc
• Diagnostics of Gaseous Halo of the Milky Way by a Shock Wave from the Galactic Centre
• Constraints on precipitation-limited hot halos from massive galaxies to galaxy clusters
• Soft X-ray line emission from hot gas in intervening galaxy halos and diffuse gas in the cosmic web