Supernova Feedback and the Hot Gas Filling Fraction of the Interstellar Medium

Miao Li; Jeremiah P. Ostriker; Renyue Cen; Greg L. Bryan; Thorsten Naab

doi:10.1088/0004-637X/814/1/4

paper

Supernova Feedback and the Hot Gas Filling Fraction of the Interstellar Medium

arXiv:1506.07180 · doi:10.1088/0004-637X/814/1/4

Abstract

Supernovae (SN), the most energetic stellar feedback mechanism, are crucial for regulating the interstellar medium (ISM) and launching galactic winds. We explore how supernova remnants (SNRs) create a multiphase medium by performing 3D hydrodynamical simulations at various SN rates, $S$ , and ISM average densities, $n ˉ$ . The evolution of a SNR in a self-consistently generated three-phase ISM is qualitatively different from that in a uniform or a two-phase warm/cold medium. By travelling faster and further in the low-density hot phase, the domain of a SNR increases by $> 1 0^{2.5}$ . Varying $n ˉ$ and $S$ , we find that a steady state can only be achieved when the hot gas volume fraction $f_{V, hot} ≲ 0.6 \pm 0.1$ . Above that level, overlapping SNRs render connecting topology of the hot gas, and the ISM is subjected to thermal runaway. Photoelectric heating (PEH) has a surprisingly strong impact on $f_{V, hot}$ . For $\bar{n}\gtrsim 3 \cm-3 $, a reasonable PEH rate is able to suppress the thermal runaway. Overall, we determine the critical SN rate for the onset of thermal runaway to be $S_{\rm{crit}} = 200 (\bar{n}/1\cm-3)^k (E_{\rm{SN}}/10^{51}\erg)^{-1} \kpc^{-3} \myr-1$, where $k = (1.2, 2.7)$ for $n ˉ \leq 1$ and $> 1\cm-3 $, respectively. We present a fitting formula of the ISM pressure $P (n ˉ$ , $S$ ), which can be used as an effective equation of state in cosmological simulations. Despite the 5 orders of magnitude span of $(n ˉ, S)$ , the average Mach number varies little: $M \approx 0.5 \pm 0.2, 1.2 \pm 0.3, 2.3 \pm 0.9$ for the hot, warm and cold phases, respectively.

57 pages, 16 figures, 3 tables. ApJ accepted

Supernova Feedback and the Hot Gas Filling Fraction of the Interstellar Medium

Abstract

References in corpus (29)

Cited by in corpus (50)