Intergalactic dust and its photoelectric heating

Abstract

We have examined the dust photoelectric heating in the intergalactic medium (IGM). The heating rate in a typical radiation field of the IGM is represented by ${\Gamma }_{\mathrm{pe}}=1.2\times 10^{-34}$ erg s${}^{-1}$ cm${}^{-3}$ $(\mathcal{D}/10^{-4})(n_{\mathrm{H}}/10^{-5}\mathrm{c}{\mathrm{m}}^{-3}{)}^{4/3}(J_{\mathrm{L}}/10^{-21}\mathrm{erg}{\mathrm{s}}^{-1}\mathrm{c}{\mathrm{m}}^{-2}\mathrm{H}{\mathrm{z}}^{-1}\mathrm{s}{\mathrm{r}}^{-1}{)}^{2/3}(T/10^4\mathrm{K}{)}^{-1/6}$, where $\mathcal{D}$ is the dust-to-gas mass ratio, $n_{\mathrm{H}}$ is the hydrogen number density, $J_{\mathrm{L}}$ is the mean intensity at the hydrogen Lyman limit of the background radiation, and $T$ is the gas temperature, if we assume the new X-ray photoelectric yield model by Weingartner et al. (2006) and the dust size distribution in the Milky Way by Mathis, Rumpl, & Nordsieck (1977). This heating rate dominates the HI and HeII photoionization heating rates when the hydrogen number density is less than $\sim 10^{-6}$ cm${}^{-3}$ if $\mathcal{D}=10^{-4}$ which is 1% of that in the Milky Way, although the heating rate is a factor of 2--4 smaller than that with the old yield model by Weingartner & Draine (2001). The grain size distribution is very important. If only large ($\ge 0.1$ $\mu$m) grains exist in the IGM, the heating rate is reduced by a factor of $\simeq 5$. Since the dust heating is more efficient in a lower density medium relative to the photoionization heating, it may cause an inverted temperature--density relation in the low density IGM suggested by Bolton et al. (2008). Finally, we have found that the dust heating is not very important in the mean IGM before the cosmic reionization.

Earth, Planets and Space, special issue "Cosmic Dust" in press (paper presented in 5th annual meeting of the Asia-Oceania Geosciences Society, "Cosmic Dust" session); 16 pages and 6 figures

References in corpus (18)

• Equation of State of the Photoionized Intergalactic Medium
• Dust emission from the most distant quasars
• Freshly Formed Dust in the Cassiopeia A Supernova Remnant as Revealed by the Spitzer Space Telescope
• The Chemistry of the Early Universe
• Metal Enrichment of the Intergalactic Medium at z=3 by Galactic Winds
• Possible evidence for an inverted temperature-density relation in the intergalactic medium from the flux distribution of the Lyman-alpha forest
• Mixing Metals in the Early Universe
• Dust Destruction in Fast Shocks of Core-Collapse Supernova Remnants in the Large Magellanic Cloud
• Photoelectric Emission from Dust Grains Exposed to Extreme Ultraviolet and X-ray Radiation
• IGM metal enrichment through dust sputtering
• Cosmological Constant or Intergalactic Dust? Constraints from the Cosmic Far Infrared Background
• Measuring the properties of extragalactic dust and implications for the Hubble diagram
• The Impact of Cosmic Dust on Supernova Cosmology
• Photoelectric heating for dust grains at high redshifts
• Extinction curves expected in young galaxies
• Amount of intergalactic dust: constraints from distant supernovae and thermal history of intergalactic medium
• Infrared Emission from Intracluster Dust Grains and Constraints on Dust Properties
• Dust Distribution during Reionization