A theory of the interstellar medium - Three components regulated by supernova explosions in an inhomogeneous substrate

“These parameters are consistent with the warm component of the ISM of McKee & Ostriker (1977).”

“This injection of mechanical energy into the ISM is the origin of the Hot Intercloud Medium (HIM) and a source of turbulent pressure that supports the gas disk and the clouds therein against self-gravity and gravitational collapse in the host galaxy’s potential (McKee & Ostriker 1977).”

“…forming so-called (super)bubble structures with scales of tens to thousands of parsecs over timescales of tens of millions of years (e.g., McKee & Ostriker 1977; Mac Low & McCray 1988; Oey & Clarke 1997; Weisz et al. 2009a, 2009b; Bagetakos et al. 2011; Keller et al. 2014, 2015, 2016;…”

“Observations of H i velocities perpendicular to the disk (vz) are necessary for studies of both the interstellar medium (ISM; McKee & Ostriker 1977; Kulkarni & Heiles 1988; Braun & Walterbos 1992; Braun 1997) and disk dynamics (Oort 1932; Rupen 1989; Lockman&Gehman1991;Merrifield 1993;Malhotra…”

“By using the theoretical models of McKee & Ostriker (1977) and Efstathiou (2000), they predict the mass outflow rate Ṁw and the wind velocity vw at blow out as a function of the star formation rate Ṁ⋆ of the host galaxy, Ṁw = 133 ( Ṁ⋆ 100M⊙ yr −1 )0.71 K M⊙ yr −1, (8) vw = 623 ( Ṁ⋆ 100M⊙ yr…”

“…considerably complicated nature of interstellar medium, which can be modeled as three phase structure (““ hot ÏÏ, ““ warm ÏÏ, and ““ cool ÏÏ gas) by McKee & Ostriker (1977), would not be so simply modeled by the ““ sticky particle ÏÏ method in which gaseous dissipation is modeled by ad hoc…”

“At the conductive interfaces, nonequilibrium ionization effects can increase the cooling up to an effective value β ∼ 10 (Borkowski et al. 1990; McKee & Ostriker 1977).”

“Note that in our model hot gas is any gas that is not cold, i.e., it corresponds to the sum of the warm and hot phases of the ISM in the usual three-phase description (McKee & Ostriker 1977; Klessen & Glover 2016).”

“For example, supernova remnants interact with the interstellar medium (McKee & Ostriker 1977).”

“Molecular clouds belong to the densest and coldest parts of the Milky Way interstellar medium (Field et al. 1969; McKee & Ostriker 1977).”

“Disk galaxies have a complex, multi-phase and inhomogeneous ISM (McKee & Ostriker 1977; Hopkins et al. 2012; Hill et al. 2012; Gent et al. 2013) that may modify the evolution of SNRs (Martizzi et al. 2015; Li et al. 2015).”

“Furthermore, fractal clouds are very di†erent from the structures used as input for the global, quasi-equilibrium models of the ISM, such as those of McKee & Ostriker (1977), Cox (1990), and their close relatives, in which the H I disk has a smooth, warm, thick component containing isolated cooler…”

“But if DLAs are multiphase media in which the CNM andWNM are in pressure equilibrium, wewould expect a similar fraction of DLA sight lines to intersect each phase if, by analogy with the Galaxy ISM, they have comparable area covering factors (McKee & Ostriker 1977).”

“Cooling is suppressed for particles within a radius computed via the blastwave solution of McKee & Ostriker (1977) and for a timescale of a few 10 Myr, which corresponds to the snowplow phase.”

“However, thanks to the many theoretical (McKee & Ostriker 1977; Wolfire et al. 2003) and observational (Gibson et al. 2000; Heiles & Troland 2003; Dickey et al. 2003; Strasser & Taylor 2004) studies on the Galactic ISM carried out in the last decades, we have formed a good understanding of the…”

“Our results also have the implication that the development of a high-P power-law tail is not exclusive to supernova-driven models, such as the McKee & Ostriker (1977) model, and that pure advective driving can generate approximate power-law tails in low-γe flows at sufficiently high Mach numbers.”

“…bythe extreme densities observed around Kepler (∼ 2− 100 cm−3), which, at& 500 pc out of the galactic plane, should have surrounding densities of< 10−2 cm−3 (McKee & Ostriker 1977), as well as the nitrogen overabundance seen in optical spectra (Blair et al. 1991), and high (∼ 200 km s−1) blueshift.”

“…the ISM equation of state: effectively the pressure support attributed to feedback loops in the ISM such as star formation, supernovae, stellar winds, radiation pressure, cosmic rays and other sources; see e.g. McKee & Ostriker 1977; Springel & Hernquist 2003; Thompson, Quataert & Murray 2005).”

“Star formation: star formation follows the approach set out in SH03, where a gas particle above a density threshold of nH = 0.13 cm−3 is modelled as a fraction of cold clouds embedded in a warm ionized medium, following McKee & Ostriker (1977).”

“In fact, it is expected that the interstellar medium (ISM) can be in a multi-temperature phase7 (e.g., McKee & Ostriker 1977; 7 It is also known that hot gas in other systems such as galaxy groups or clusters can be multi-temperature (e.g., Buote et al. Muno et al. 2004; Randall et al. 2006).”

“…several ways the energy inputs from the OB stars can modify the physical environment and chemistry of the host complex in which they reside (e.g., McKee & Ostriker 1977), and therefore can trigger the formation of a new generation of stars in the complex (e.g., Elmegreen & Lada 1977; Bertoldi &…”

“Taking this into account, our predicted hydrogen upper limit is still well below the columns expected for CNM clouds (1020−1021 cm−2; McKee & Ostriker 1977) and also below the mean column density of Na I detected towards 3C 225: 〈log(NNaI/cm −2)〉 = 11.7 (Meyer et al. 2006).”

“McKee & Ostriker (1977) postulated that the multiphase nature of the ISM is regulated predominantly by supernova explosions, and indeed it is such events that we c© 0000 RAS, MNRAS 000, 1–13 have in mind when we insert star-formation induced feedback into our simulations.”

“In models of the multiphase ISM that assume thermal pressure equilibrium between phases (Field, Goldsmith, & Habing 1969; McKee & Ostriker 1977; Wolfire et al. 1995), this is predicted to have a temperature of approximately 8000 K, high enough to collisionally dissociate H2.”

“…in the ‘explosive’ and ‘hot’ models (postulated by Ostriker & Cowie 1981 and Berman & Suchkov 1991, respectively) where the SN explosions and galactic wind are the process of star formation self-regulation in young galaxies (see also McKee & Ostriker 1977; Heckman et al. 1990; Lı́pari et al. 1994).”

“Mass and energy is exchanged between these phases in a way similar to as in Yepes et al. (1997), crudely describing the complicated physical processes thought to regulate star formation in the interstellar medium (McKee & Ostriker 1977).”

“Given the galactic SN rate, the hot medium (T ∼ 106 K) created by SN shocks can occupy a large volume (Cox & Smith 1974; McKee & Ostriker 1977) and break out the disk (Shapiro & Field 1976).”

“This phase is called the snowplow phase, and the radius depends on the amount of injected energy, the density of the medium, and how much of the energy is radiated away (Weaver et al. 1977; McKee & Ostriker 1977; Cooper et al. 2008; ?”

“Among the most significant findings is the fact that a substantial fraction of the CNM lies below the canonical 100 K temperature predicted by phased ISM models (Field et al. 1969; McKee & Ostriker 1977) for maintaining pressure balance.”

“Heiles & Troland (2003) indicate that a model of CNM cores contained in WNM envelopes, as suggested in McKee & Ostriker (1977), provides a good description of the data toward many sources.”

“We note that the ISM in the NIHAO simulations is very different from the one of McKee & Ostriker (1977), based on the assumptions of different phases in pressure equilibrium.”

“McKee & Ostriker (1977) set the lower limit to a cl = a l = 0.5 pc.”

“Gas particles that are sufficiently dense to become Jeans unstable (n > 0.13 cm−3) are treated as a two-phase interstellar medium (ISM) consisting of hot gas that condenses into cold star-forming clouds via a thermal instability (McKee & Ostriker 1977).”

“For an ISM which is shaped by expanding bubbles driven by stellar feedback, the separation is set by the scale on which the bubbles depressurise, which is the scale height of the disc (McKee & Ostriker 1977; Hopkins et al. 2012).”

“Multiple components of gas with varying densities and temperatures coexist (Field et al. 1969; Cox & Smith 1974; McKee & Ostriker 1977), animated by turbulence that pervades the whole volume (Elmegreen & Scalo 2004).”

“1 I N T RO D U C T I O N Feedback from massive stars is a fundamental process regulating the energetics and dynamics of the interstellar medium (ISM; e.g. McKee & Ostriker 1977; Leitherer, Robert & Drissen 1992; Gazol-Patiño & Passot 1999; Korpi et al. 1999; Wada, Spaans & Kim 2000).”

“Cold gas1 is likely to co-exist with the hot phase in the form of pressure-confined clouds, by analogy with the multiphase model of the interstellar medium (ISM) (McKee & Ostriker 1977).”

“However, this approach does not take into account the fact that the residence time of the dust in the clumps can be shortened by the thermal evaporation of the clouds (Cowie and McKee 1977) and by the capability of the grains to escape from the cloud due to their ballistic velocities.”

“According to the classical theory, an SNR evolves through four different phases in its passage to the point where it merges with the ambient ISM (Woltjer 1972; McKee & Ostriker 1977; Dopita & Sutherland 2003; Draine 2011).”

“…the clumpy surface of the Local Bubble suggests that the distribution of dense gas and young stars is self-organized by super-nova feedback, as predicted by theory and simulations (Cox & Smith 1974; McKee & Ostriker 1977; Whitworth et al. 1994; Dawson 2013; Inutsuka et al. 2015; Kim et al. 2017).”

“There are smaller, comparable contributions from the diffuse WIM, which has an average density well below 1 cm−3 (McKee & Ostriker 1977; Reynolds 1991; Cox 2005; Hill et al. 2007), and from the CNM , and a vanishing contribution of the WNM.”

“Such a multiphase treatment of the interstellar medium is motivated by McKee & Ostriker (1977) (see also Johansson & Efstathiou 2006).”

“It is believed that physical conditions in the neutral gas associated with normal galaxies are influenced by the radiative and mechanical feedback from the in situ star formation activity (McKee & Ostriker 1977).”

“As the blastwave model of feedback assumes that supernova cavities last longer in low-pressure and high-density environments (McKee & Ostriker 1977) more particles have their cooling shut-off for longer time periods and the amount of ejected gas is increased.”

“…1–100 pc (see review by Dale 2015, and later references in this section), collectively cause the thermal phases of the interstellar medium (ISM, e.g. McKee & Ostriker 1977; Gatto et al. 2017) and even drive flows out of galaxies (see review on galactic winds by Veilleux, Cecil & Bland-Hawthorn…”

“…with a 30 circularz p 2 Gaussian beam. description of the ISM that includes cold clouds in pressure equilibrium with hot, diffuse gas (e.g., McKee & Ostriker 1977), and a prescription for star formation constrained by the Schmidt/Kennicutt laws (Kennicutt 1998; Schmidt 1959; see Springel &…”

“However, due to their large overpressures with respect to the intercloud medium, such small-scale condensations cannot be accommodated in any abundance by the standard McKee & Ostriker (1977) pressure equilibrium model for the ISM.”

“On the other hand it is not clear that (i) in the three-phase McKee-Ostriker model (McKee & Ostriker 1977), photons from the Galactic UV background penetrate sufficiently deep in the WNM and (ii) even if 101 102 103 104 -40 -20 0 20 40 T s (K ) vLSR (km s -1) -0.004 -0.002 0.000 0.002 0.004 O pt ic…”

“1 of McKee & Ostriker (1977)] is expected to form at the edges of supernova remnants and super-bubbles containing the hot ionized medium (HIM).”

“Famous twophase and three-phase models of the interstellar medium (ISM) were born out of the studies of thermal instabilities (Field et al. 1969; McKee & Ostriker 1977).”

“We have selected a snapshot data (at t =0.29 Myr after the shock compression) before the filament evolves into supercritical and shows gravitational collapse (that happens at t = 0.44 Myr).”

“They presented results for a small (R = 5 pc) isolated cloud in a McKee & Ostriker (1977) type model of cool cloudlets in a hot medium of large filling factor.”

“As in the usual three-phases model of the ISM (McKee & Ostriker 1977), three stable branches can be seen in Figure 5a, i.e. cold, dense gases (10 ρ 105M⊙ pc −3 and Tg 10 2 K), warm gases at Tg ∼ 104 K, and hot, diffuse gases at Tg ∼ 106 K and ρ 0.1M⊙ pc−3.”

“On the other hand, the timescale between physical disturbances in the ISM (i.e. the typical time interval between significant pressure fluctuations) due to the propagation of supernova shocks is≈ 4× 105 yr (McKee & Ostriker 1977; Wolfire et al. 1995).”

“In order for our simulations to resemble the real interstellar medium (ISM) as closely as possible, our heating and cooling solutions should be able to replicate the three-phase ISM (McKee & Ostriker 1977; Cox 2005), where we have equal pressure solutions for a quasi-static hot medium and warm and cold media.”

“The diffuse gas in the ISM is observed to be in three dominant phases: a cold phase (T ∼ 100 K), a warm phase (T ∼ 104 K) and a hot phase (T ∼ 106 K) (McKee & Ostriker 1977).”

“We model supernova feedback using the blastwave formalism described in McKee & Ostriker (1977) and implemented in our simulations as in Stinson et al. (2006).”

“Components of the interstellar medium, taken from [29, 30].”

“The structure and evolution of the interstellar medium (ISM) is largely dependent upon the thermal processes taking place (Goldsmith et al. 1969; de Jong 1977; McKee & Ostriker 1977; Draine 1978; Ferriere et al. 1988).”