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Cold Neutral Gas in a z=4.2 Damped Lyman-alpha System: The Fuel for Star Formation | | J. Christopher Howk
; Arthur M. Wolfe
; Jason X. Prochaska
; | | Date: |
31 Mar 2004 | | Journal: | Astrophys.J. 433 (1994) 468 | | Subject: | astro-ph | | Affiliation: | UCSD), Jason X. Prochaska (UCSC | | Abstract: | We discuss interstellar temperature determinations using the excitation equilibrium of the ^2P levels of Si II and C II. We show how observations of the ^2P_3/2 fine structure levels of Si II and C II (which have significantly different excitation energies, corresponding to ~413 and 92 K, respectively) can be used to limit gas kinetic temperatures. We apply this method to the z=4.224 damped Lyman-alpha system toward the quasar PSS1443+27. The lack of significant absorption out of the SiII ^2P_3/2 level and the presence of very strong C II ^2P_3/2 provides an upper limit to the temperature of the C II*-bearing gas in this system. Assuming a solar Si/C ratio, the observations imply a 2-sigma limit T<954 K for this absorber; a super-solar Si/C ratio gives stricter limits, T<524 K. The observations suggest the presence of a cold neutral medium; such cold gas may serve as the fuel for star formation in this young galaxy. | | Source: | arXiv, astro-ph/0404005 | | Services: | Forum | Review | PDF | Favorites | |
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