Constraining the H column density distribution at z3 from composite DLA spectra
Apr 12, 20186 pages
Published in:
- Mon.Not.Roy.Astron.Soc. 478 (2018) 1, L7-L11
- Published: Jul 21, 2018
e-Print:
- 1804.04611 [astro-ph.GA]
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Abstract: (Oxford University Press)
We present the detection of the average H_2 absorption signal in the overall population of neutral gas absorption systems at z∼ 3 using composite absorption spectra built from the Sloan Digital Sky Survey-III damped Lyman α catalogue. We present a new technique to directly measure the H_2 column density distribution function from the average H_2 absorption signal. Assuming a power-law column density distribution, we obtain a slope and an incidence rate of strong H_2 absorptions [with N(H_2) ≳ 10^18 cm^−2] to be in H i absorption systems with N(H i) ≥10^20 cm^−2. Assuming the same inflexion point where steepens as at z = 0, we estimate that the cosmological density of H_2 in the column density range is of the total. We find one order of magnitude higher H_2 incident rate in a sub-sample of extremely strong damped Lyman α absorption systems (DLAs) [], which, together with the derived shape of , suggests that the typical H i–H_2 transition column density in DLAs is log N(H)(cm^−2) ≳ 22.3 in agreement with theoretical expectations for the average (low) metallicity of DLAs at high-z.Note:
- 6 pages, 3 figures, accepted for publication in MNRAS letters
- quasars: absorption lines
- cosmology: observations
- ISM: clouds
- ISM: molecules
References(40)
Figures(1)