TY - JOUR
T1 - Intergalactic dust and its photoelectric heating
AU - Inoue, Akio K.
AU - Kamaya, Hideyuki
N1 - Funding Information:
Acknowledgments. We appreciate comments from the reviewers, B. T. Draine and M. M. Abbas, which improved the quality of this paper very much. We are grateful to the conveners of the session “Cosmic Dust” in the 5th annual meeting of the Asia-Oceania Geosciences Society for organizing the interesting workshop. AKI is also grateful to all members of the Department of Physics, Nagoya University, especially the Ω Laboratory led by Tsutomu T. Takeuchi, for their hospitality during this work. AKI is supported by KAKENHI (the Grant-in-Aid for Young Scientists B: 19740108) by The Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan.
PY - 2010
Y1 - 2010
N2 - We have examined dust photoelectric heating in the intergalactic medium (IGM). The heating rate in a typical radiation field of the IGM is represented by Tpe = 1.2 x 10-34 erg s-1 cm-3 (P/10-4)(72h/10-5 cm-3)4/3(J L/10-21 ergs-1 cm-2 Hz-1 sr-1)2/3(T/104 K)-1/6, where D is the dust-to-gas mass ratio, nh is the hydrogen number density, Jl 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 et al. (1977). This heating rate dominates the HI and Hell photoionization heating rates when the hydrogen number density is less than ∼10-6 cm-3 if 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 and Draine (2001). The grain size distribution is very important. If only large (≥0.1 μm) grains exist in the IGM, the heating rate is reduced by a factor of ≃5. Since 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, as suggested by Bolton et al. (2008). Finally, we have found that dust heating is not very important in the mean IGM before the cosmic reionization.
AB - We have examined dust photoelectric heating in the intergalactic medium (IGM). The heating rate in a typical radiation field of the IGM is represented by Tpe = 1.2 x 10-34 erg s-1 cm-3 (P/10-4)(72h/10-5 cm-3)4/3(J L/10-21 ergs-1 cm-2 Hz-1 sr-1)2/3(T/104 K)-1/6, where D is the dust-to-gas mass ratio, nh is the hydrogen number density, Jl 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 et al. (1977). This heating rate dominates the HI and Hell photoionization heating rates when the hydrogen number density is less than ∼10-6 cm-3 if 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 and Draine (2001). The grain size distribution is very important. If only large (≥0.1 μm) grains exist in the IGM, the heating rate is reduced by a factor of ≃5. Since 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, as suggested by Bolton et al. (2008). Finally, we have found that dust heating is not very important in the mean IGM before the cosmic reionization.
KW - Dust grains
KW - Intergalactic medium
KW - Photo-electron
KW - Photo-ionization
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U2 - 10.5047/eps.2008.10.003
DO - 10.5047/eps.2008.10.003
M3 - Article
AN - SCOPUS:77949818798
VL - 62
SP - 69
EP - 79
JO - Earth, Planets and Space
JF - Earth, Planets and Space
SN - 1343-8832
IS - 1
ER -