Astrophysics of the Diffuse Universe

Dopita, Michael A.; Sutherland, Ralph S.

doi:10.1007/978-3-662-05866-4

Cited by 293 publications

(335 citation statements)

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“…The MAPPINGS II code extended the earlier code to include many new atoms, ions, and physical processes by Sutherland & Dopita (1993). The MAPPINGS III code was further extended to include dust heating (Dopita & Sutherland 2000) and its non-equilibrium heating and IR emission (Groves et al 2004(Groves et al , 2006Dopita et al 2005). The earlier version of the MAPPINGS IV code was described by Dopita et al (2013), and included improved treatment of temperature-dependent collision strengths, and line excitation and recombination under a κ−distribution of electrons (Nicholls et al 2012), as well as in the simple Maxwell-Boltzmann case.…”

Section: The Mappings Codementioning

confidence: 99%

“…In the literature one can find many expressions for the Rankine-Hugoniot flow equations (Rankine 1870;Hugoniot 1887), both for isentropic (reversible) flows and for entropy producing shock solutions (Cox 1972;Shull & McKee 1979;McKee & Hollenbach 1980;Bertschinger 1986;Innes et al 1987;Shapiro et al 1992;Dopita & Sutherland 1996). Some of the many forms which have been used can also be seen in the NACA Techical Report 1135(1953 .…”

Section: Solving For the Shocked Flowmentioning

confidence: 99%

“…Whilst the coupled ionisation-cooling balance equations are readily solved in the cooling and recombination zones of the shock, the optical/IR emission line spectrum also depends on the ionisation state, temperature and magnetic pressure of the gas entering the shock. For fast shocks (Dopita & Sutherland 1996;Allen et al 2008), the ionisation and temperature of this gas is entirely determined by the ionising UV photons produced in the cooling zone of the shock, which run ahead to pre-ionize the incoming medium. For shocks with velocities v s 150km/s, the velocity of the ionisation front is appreciably greater than the shock velocity, and an equilibrium H II region develops in the precursor medium.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Preionization in Radiative Shocks. I. Self-consistent Models

Sutherland

Dopita

2017

ApJS

Self Cite

126

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In this paper we treat the pre-ionisation problem in shocks over the velocity range 10 < v s < 1500 km/s in a self-consistent manner. We identify four distinct classes of solution controlled by the value of the shock precursor parameter, Ψ = Q/v s , where Q is the ionization parameter of the UV photons escaping upstream. This parameter determines both the temperature and the degree of ionisation of the gas entering the shock. In increasing velocity the shock solution regimes are cold neutral precursors (v s 40 km/s), warm neutral precursors (40 v s 75 km/s), warm partly-ionized precursors (75 v s 120 km/s), and fast shocks in which the pre-shock gas is in photoionisation equilibrium, and is fully ionized. The main effect of a magnetic field is to push these velocity ranges to higher values, and to limit the post-shock compression. In order to facilitate comparison with observations of shocks, we provide a number of convenient scaling relationships for parameters such as post-shock temperature, compression factors, cooling lengths, and Hβ and X-ray luminosity.

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Section: The Mappings Codementioning

confidence: 99%

Section: Solving For the Shocked Flowmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of Preionization in Radiative Shocks. I. Self-consistent Models

Sutherland

Dopita

2017

ApJS

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126

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“…For example, (Meurer et al 2009) argue that the formation of dense bound clusters is inhibited in regions of low mass surface density because the midplane pressure in the disk influences internal cloud pressures (see e.g. Dopita & Sutherland 2003). If massive stars form via competitive accretion (Larson 1973), in which interactions between protostars drive mass segregation and subsequent gas accretion in high density cluster cores, protostars in low-density clusters would suffer fewer interactions and accrete less mass, inhibiting the growth of high-mass stars (e.g.…”

Section: Introductionmentioning

confidence: 99%

Star-forming Environments throughout the M101 Group

Watkins¹,

Mihos²,

Harding³

2017

ApJ

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We present a multiwavelength study of star formation within the nearby M101 Group, including new deep Hα imaging of M101 and its two companions. We perform a statistical analysis of the Hα to FUV flux ratios in H II regions located in three different environments: M101's inner disk, M101's outer disk, and M101's lower mass companion galaxy NGC 5474. We find that, once bulk radial trends in extinction are taken into account, both the median and scatter in F Hα /F FUV in H II regions are invariant across all of these environments. Also, using Starburst99 models, we are able to qualitatively reproduce the distributions of F Hα /F FUV throughout these different environments using a standard Kroupa IMF, hence we find no need to invoke truncations in the upper mass end of the IMF to explain the young star-forming regions in the M101 Group even at extremely low surface density. This implies that star formation in low density environments differs from star formation in high density environments only by intensity and not by cloud-to-cloud physics.

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“…The total emissivity for free-free and free-bound emission taken from Dopita & Sutherland (2003) is ν = 4πn e n p γ c exp(−hν/kT g )…”

Section: Nebula and Line Emissionmentioning

confidence: 99%

First stars and the extragalactic background light: how recentγ-ray observations constrain the early universe

Kneiske

Mazin

2009

A&A

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Context. The formation of the first stars (Population III; PopIII) marks the end of the dark ages of the universe, a subject of lively scientific debate. Not (yet) accessible to direct observations, this early stage of the universe is mostly studied via theoretical calculations and numerical simulations. An indirect window is provided by integrated present day observables such as the metal abundance or the diffuse extragalactic photon fields. Aims. We aim to derive constraints on the properties of the PopIII and low metallicity Population II (LM PopII) stars utilizing limits on the density of the extragalactic background light (EBL), recently derived from very-high-energy (E > 100 GeV; VHE) observations. Methods. A model calculation for the evolving EBL density produced by PopIII/LM PopII stars is presented. The model utilizes stellar population spectra (SPS) for zero and low metallicity stars and accounts for the changing emission of an aging stellar population. Emission from the dense HII regions surrounding the stars (nebula) is included. The resulting EBL density for different scenarios (metallicity, star formation rate, initial mass function) is compared to the limit on the EBL density. The potential for detecting a cut-off in HE/VHE spectra is discussed. Results. Assuming a maximum contribution from PopIII/LM PopII stars to the EBL density of 5 nW m −2 s −1 at 2 μm, a limit on the star formation rate (SFR) of the first stars of 0.3 to 3 M Mpc −3 yr −1 in the redshift range 7−14 is derived. The limit depends on the assumed shape of the SFR and metallicity. Conclusions. The EBL can be used as a probe to investigate the properties of PopIII/LM PopII stars. Limits on the EBL density derived from VHE observations can provide constraints on the parameters of the these stars, in particular the star formation rate.

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Astrophysics of the Diffuse Universe

Cited by 293 publications

References 0 publications

Effects of Preionization in Radiative Shocks. I. Self-consistent Models

Effects of Preionization in Radiative Shocks. I. Self-consistent Models

Star-forming Environments throughout the M101 Group

First stars and the extragalactic background light: how recentγ-ray observations constrain the early universe

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