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

“This is applicable to a shell expanding from the pressure of a hot interior, such as an old supernova remnant (McKee & Ostriker 1977).”

“If the low-density interstellar medium has a filling factor fH= 0.7, as suggested by McKee & Ostriker (1977), Equation (5) gives a birthrate of one in 240 yr.”

“For radiative SNRs, McKee & Ostriker (1977) and Blinnikov et al. (1982) obtained the diameter evolution with a slope of 2/7, in the form of ( D pc ) = 1.42 ( E n0 )5/21 ( t yr )2/7 , (3) where n0 is the original number density of uniform interstellar medium (ISM).”

“The Interstellar Medium (ISM) can be described as an inhomogeneous ensemble of three phases (McKee & Ostriker 1977).”

“The horizontal dotted lines indicate the specific thermal energy of cold gas with T∞=104 K and hot gas with T∞ = 106 K more appropriate for massive halos (McKee & Ostriker 1977; Springel & Hernquist 2003; Pelupessy et al. 2007).”

“Although it has long been known (see e.g. McKee & Ostriker 1977) that supernova (SN) explosions can inject large amounts of kinetic and thermal energy into the galactic interstellar medium (ISM), only more recently has the importance of this phenomenon as a source of pressure support and…”

“Kepler, located well out of the Galactic plane where densities are∼ 10−2.5 −10−3 cm−3 (McKee & Ostriker 1977), has a high systemic velocity of∼ 300 km s−1.”

“As it is now well established, the atomic interstellar medium is thermally bistable as predicted by detailed computations of thermal balance (Field, Goldsmith, and Habing 1969; McKee and Ostriker 1977; Wolfire et al. 1995, 2003).”

“McKee & Ostriker (1977) explored the interaction of an SNR with an inhomogeneous ambient medium.”

“We also find that most of the UFO energy is carried away by hot low density gas escaping the innermost regions of the host via paths of least resistance, which exists in the clumpy ISM in abundance (e.g., McKee & Ostriker 1977).”

“Each supernova deposits 1051 erg of energy into the ISM within a blast radius described by McKee & Ostriker (1977).”

“The hot volume phase occupies most of the volume inside the host, while the cold medium probably carries most of the gaseous mass (McKee & Ostriker 1977; Fall & Rees 1985).”

“The interplay of stars and their surrounding gas leads to the presence of distinct phases in the interstellar medium (ISM) of galaxies (e.g., Field et al. 1969; McKee & Ostriker 1977).”

“The interaction of shocks from supernovae with density inhomogeneities – clouds – can give rise to compression, rarefaction, vaporization, and acceleration of these inhomogeneities [McKee & Ostriker(1977)].”

“…scales and injecting different amounts of kinetic energy into the medium; among these, supernova (SN) explosions are thought to be the dominant agent, at least in the star forming regions of galaxies (McKee & Ostriker 1977; Norman & Ferrara 1996; MacLow 2004; de Avillez & Breitschwerdt 2007).”

“…stars (e.g. McKee 1995; Wiseman & Ho 1998; Pudritz & Fiege 2000), but also on the phase structure and energetics of the ISM on galactic scales (e.g. McKee & Ostriker 1977; Norman & Ferrara 1996) and on the thermodynamics and enrichment of the inter-galactic medium (IGM) on scales of several Mpc…”

“The ISM has multiple components with a range of temperatures and densities (McKee & Ostriker 1977).”

“This could be the result of either a close physical association between the H I and H II (McKee & Ostriker 1977) or large scale organized motions of the interstellar medium along this sightline (Walters & Cox 2001).”

“…a problem, however, we believe it to be located in a medium with density n0 <∼ 1.0 × 10 −2 cm−3 and since a large fraction of the ISM is believed to consist of low density coronal gas (e.g. McKee & Ostriker 1977), SNRs expanding into such regions will be undetectable (e.g. Kafatos et al. 1980).”

“Due to their large overpressures with respect to the intercloud medium, such structures cannot be accommodated in any abundance in the standard McKee & Ostriker (1977) model of the ISM.”

“Yet, we know that the interstellar medium in galaxies is very clumpy, with molecular gas clouds having average sizes in the 10-100 pc range, and filling factors of a few percent are estimated for the cold dense phase (McKee & Ostriker 1977).”

“The ISM is modeled as multiphase in nature, with cold clouds embedded in a hotter, pressure-confining ISM (e.g. McKee & Ostriker 1977; Springel & Hernquist 2003).”

“An analytic model of a point-source explosion exhibits η = 2/7 in the absence of radiative cooling in the hot bubble (McKee & Ostriker 1977).”

“This hot gas is the result of feedback from supernovae, massive star winds, and radiation pressure (McKee & Ostriker 1977; Chevalier & Clegg 1985; Strickland et al. 2000).”

“…which are then allowed to cool radiatively, but only after a cooling shut-off time equal to the survival time of the hot low-density shell of the SN (McKee & Ostriker 1977; in ErisBH) or twice that (in Eris2k), in order to prevent the gas from quickly radiating away the SN energy because of the…”

“SN explosions can heat and expel gas from molecular clouds, drive turbulence in the interstellar medium (ISM), and produce galactic scale outflows (McKee & Ostriker 1977; Chevalier & Clegg 1985; Strickland & Stevens 2000; McKee & Ostriker 2007).”

“Similarly, cooling and heating processes have been studied in the context of the structure of the interstellar medium (ISM; McKee & Ostriker 1977), and the dense solar corona which hosts solar prominences and coronal rain (see Antolin 2020 for a review).”

“We know, for instance, that the interstellar medium is kept in a stable at three phase state due to thermal feedback processes (McKee & Ostriker 1977).”

“In the multiphase model by McKee & Ostriker (1977) the cavities of the ISM contain low-density hot gas.”

“For the ISM density distributions we will use volume filling fractions of fhot ≈ 70%, fwarm ≈ 25%, and fcold ≈ 5% for the hot, warm, and cold phases respectively (McKee & Ostriker 1977).”

“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).”

“…ISM by comparing the relative strengths of various emission lines with pre- dictions from atomic physics (e.g., Sargent & Searle 1970; Searle & Sargent 1972; Pagel et al. 1979; McKee & Ostriker 1977; McGaugh 1991; Zaritsky et al. 1994; Kewley & Dopita 2002; Pilyugin & Thuan 2005; Berg et al. 2015).”

“The code accounts for radiative cooling of the gas (Katz et al. 1996; Davé et al. 1999), and a multiphase description of the ISM that includes cold clouds in pressure equilibrium with a hot, diffuse gas (e.g. McKee & Ostriker 1977; see also Springel & Hernquist 2003a).”

“This model was developed later by McKee & Ostriker (1977), who suggested a three-component model of the interstellar medium based on X-ray observations.”

“Interactions between massive stars and the interstellar medium (ISM) have led to the derivation of a multi-phase ISM model (McKee & Ostriker 1977) and have been used to explain the disk-halo connection in a galaxy (Norman & Ikeuchi 1989).”

“The SNe, which we have not included in our simulations, generate a third, hottest phase (McKee & Ostriker 1977) and drive more realistic turbulence than what we assumed.”

“…has indicated that the diffuse interstellar medium (ISM) is highly structured on scales below 1 pc, contrary to earlier theoretical expectations (McKee & Ostriker 1977) and observations which had suggested an apparent minimum cloud size (e.g. Crovisier, E-mail: kts@ras.org.uk † Present address:…”

“…hit by shocks with 4 Obviously other works examining different types of massloading in diffuse sources, for example through thermal conduction (e.g. McKee & Ostriker 1977; Chièze & Lazareff 1981; White & Long 1991; Pittard, Hartquist & Dyson 2001b; Pittard, Hartquist & Ashmore 2003a; Pittard et…”

“In the case of SNae type II, radiative cooling is disabled for twice the survival time of the hot low-density shell of the SN (McKee & Ostriker 1977).”

“In the model of the Galactic ISM of McKee & Ostriker (1977) the mean separation between individual HI clouds λ is of the order of 88 pc. Applied to our problem there exist two obvious limits for the response of these clouds distributed in the Galactic disk to a flare of Sgr A∗ depending on its…”

“It is now accepted fully that large portion of cold neutral medium (CNM) is colder (Heiles & Troland 2003) than the predictions of the threephase ISM model (McKee & Ostriker 1977).”

“…(H I) and inversely on the spin temperature (Ts), which is known to follow the gas kinetic temperature in the CNM (Field 1959; Bahcall & Ekers 1969; McKee & Ostriker 1977; Wolfire et al. 1995; Roy et al. 2006), and can be coupled to the gas kinetic temperature via theLyman − α radiation field in…”

“They employed the multiphase ISM model for supernova evolution by McKee & Ostriker (1977) and Efstathiou (2000) to construct a model for galactic winds in the context of starburst galaxies.”

“More recent models for the interstellar medium include a high filling factor, hot ionized medium at 106 K, which results from supernovae explosions (McKee & Ostriker 1977).”

“Throughout the ISM, Hi exists in a “multi-phase” state, characterized by two thermally-stable phases in pressure equilibrium (Field et al. 1969; McKee & Ostriker 1977; Wolfire et al. 2003): the cold neutral medium (CNM) and warm neutral medium (WNM).”

“SNe are important across many astrophysical domains, serving as sources of momentum and energy (McKee & Ostriker 1977; Li et al. 2015), turbulence (Elmegreen & Scalo 2004; Joung & Mac Low 2006), cosmic rays (Baade & Zwicky 1934; Ginzburg & Syrovatskii 1964; Blandford & Eichler 1987; Drury 2012),…”

“The McKee & Ostriker (1977) model of the ISM predicts an association between cold H i gas and ionized medium: “whenever there is a cold cloud along a given line of sight, at a given velocity, there should be warm ionized material as well at the same velocity4”.”

“Several models were developed in the past to descibe the multi-phase ISM (e. g., McKee & Ostriker 1977; Yepes et al. 1997; Gnedin 1998; Klypin 1998; Hultman & Pharasyn 1999; Stinson et al. 2006).”

“…as a power law, with the low– and high–mass slopes usually taken as reflecting the suppression of star formation by supernova (e.g. Larson 1974; McKee & Ostriker 1977; Joung & Mac Low 2006) and by AGN feedback (e.g. Croton et al. 2006; Bower et al. 2006), respectively, in the low– and…”

“Li et al. (2015) placed a SN in a classical three-phase ISM of McKee & Ostriker (1977), with clouds consisting of cold cores and warm envelopes embedded in a volume-filling hot diffuse medium.”

“Theoretical models, as originally proposed by e.g. Field et al. (1969) and McKee & Ostriker (1977) and refined by several authors subsequently, predict a number of phases in pressure equilibrium.”

“Such regions represent the hot ionized medium component of the ISM (McKee & Ostriker 1977; Cox 2005) and have a volume filling factor of around 60 per cent in the sub-grid from the MHD simulation (i.e. |z| < 2 kpc), in good agreement with other observational and theoretical studies of the ISM (e.g.…”

“If we assume that CTB 109 is in cooling phase rather than Sedovphase, the time dependence of the radius becomesR∝ t2/7 (McKee & Ostriker, 1977).”

“On the theoretical side, the role of supernovae in setting the phase structure and porosity of the ISM has been recognized for decades (McKee & Ostriker 1977).”

“Since the ISM around N 158 shows Hα emission, its temperature is probably around 8000 K, typical of the warm ionised medium (McKee & Ostriker 1977), resulting in a speed of sound of ∼9.2 km s−1.”

“We set the lower bound for cloud radii at 0.4 pc, the theoretical lower limit on the size of small clouds found by McKee & Ostriker (1977).”

“They are common across the Galaxy, and abundantly detected in large-scale H I surveys such as GASS (McClure-Griffiths et al. 2006), CGPS (Gibson et al. 2000, 2005), and SGPS (Kavars et al. 2003, 2005).”

“In the traditional picture of the ISM, supernova driven turbulence leads to a hot, diffuse third phase (Cox & Smith 1974; Mckee & Ostriker 1977).”

“However the conclusions of this paper are not dependent on the internal structure of these sub–galaxies or their detailed star formation rates, which will both be sensitive to the detailed physics of a multiphase ISM and the mechanisms of star formation.”

“While such data have so far been used to test global models of the ISM (McKee & Ostriker 1977; Korpi et al. 1999; Kim et al. 2001; de Avillez & Breitschwerdt 2004; Balsara et al. 2004; Balsara & Kim 2005; Avillez & Breitschwerdt 2005; Mac Low et al. 2005; Tilley & Balsara 2006), it is also possible…”

“…end of a broad distribution of cold, neutral clouds—at column densities much lower than those expected both from theoretical models of the ISM (e.g., McKee & Ostriker 1977) and from previous 21 cm emission/absorption observations (e.g., Heiles & Troland 2003); they may be numerous enough to…”