Abstract
Supernovae are the most energetic among stellar feedback processes, and are
crucial for regulating the interstellar medium (ISM) and launching galactic
winds. We explore how supernova remnants (SNRs) create a multiphase medium by
performing high resolution, 3D hydrodynamical simulations at various SN rates,
\$S\$, and ISM average densities, \$n\$. We find that 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 traveling faster and
further in the cooling-inefficient hot phase, the spatial-temporal domain of a
SNR is enlarged by \$>10^2.5\$ in a hot-dominated multiphase medium (HDMM)
compared to the uniform case. We then examine the resultant ISM as we vary \$n\$
and \$S\$, finding that a steady state can only be achieved when the hot gas
volume fraction \$0.60.1\$. Above that, overlapping SNRs render
connecting topology of the hot gas, and such a HDMM is subjected to thermal
runaway with growing pressure and \fvh. Photoelectric heating (PEH) has a
surprisingly strong impact on \fvh. For \$n 3 cm^-3\$, a reasonable PEH
rate is able to suppress the ISM from undergoing thermal runaway. Overall, we
determine that the critical SN rate for the onset of thermal runaway is roughly
\$S\_crit = 200 (n/1cm^-3)^k (E\_SN/10^51 erg)^-1 kpc^-3 Myr^-1\$,
where k=(1.2,2.7) for \$n\$ < 1 and >1 cm\$^-3\$, respectively. We present a
fitting formula of the ISM pressure \$P(n, S)\$, which can be used as an
effective equation of state in cosmological simulations. The observed
velocities of OB stars imply that the core collapse SN are almost randomly
located on scales \$łesssim\$ 150 pc. Despite the 5 orders of magnitude span of
\$(n,S)\$, the average Mach number shows very small variations: \$M 0.5\pm
0.2, 1.20.3, 2.30.9\$ for the hot, warm and cold phases, respectively.
Users
Please
log in to take part in the discussion (add own reviews or comments).