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2009MNRAS.396..385K - Mon. Not. R. Astron. Soc., 396, 385-401 (2009/June-2)
A search for HI 21cm absorption in strong Mg II absorbers in the redshift desert.
KANEKAR N., PROCHASKA J.X., ELLISON S.L. and CHENGALUR J.N.
Abstract (from CDS):
Two of the Mgii absorbers, at zabs∼ 1.4106 towards 2003-025 and at zabs∼ 0.9115 towards 2149+212, are known DLAs. We detect Hi 21cm absorption towards 2003-025 with the GMRT and estimate the spin temperature of the DLA to be Ts = [(905±380)xf] K. Conversely, the GBT observations of 2149+212 resulted in a non-detection of Hi 21cm absorption, yielding the 3σ limit Ts> [2700xf] K.
Excluding `associated' systems (within 3000km/s of the quasar redshift), the detection rate of Hi 21cm absorption in strong Mgiiλ2796 absorbers is per cent, at a 3σ optical depth sensitivity of ∼0.013 per 10km/s. Comparing the detection rates of Hi 21cm and damped Lyman α absorption in strong Mgii absorber samples yields a detection rate of Hi 21cm absorption in DLAs of per cent, consistent with the detection rate in low-z DLAs. Since Hi 21cm absorption arises in cold neutral gas, this indicates that most gas-rich galaxies contain significant fractions of cold Hi by z ∼ 1.
Finally, we use the observed detection rate of Hi 21cm absorption in Mgii absorbers to infer the cosmological mass density of neutral gas in DLAs, assuming that (1) the average Hi column density in our Hi 21cm absorber sample is the same as that measured by Rao, Turnshek & Nestor in their DLA sample and (2) the detection rate of Hi 21cm absorption in the DLAs of our Mgii sample is the same as that in known DLAs at 0.09 < zabs< 3.45. We obtain ΩGAS∼ (0.55+0.42–0.22) x10–3, at, slightly lower than, but consistent with, the value obtained by Rao, Turnshek & Nestor from their DLA survey at similar redshifts.
Abstract Copyright: © 2009 The Authors. Journal compilation © 2009 RAS
Journal keyword(s): galaxies: evolution - galaxies: ISM - radio lines: galaxies
Simbad objects: 57
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