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Constraints on the gas masses of low-z damped Lyman-$\alpha$ systems

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(2014)cite arxiv:1406.0991Comment: 5 pages, 4 figures; accepted for publication in MNRAS (Letters).

Abstract

We report a deep search for redshifted HI 21 cm emission from three damped and sub-damped Lyman-$\alpha$ absorbers (DLAs) at $z 0.1$ with the Green Bank Telescope (GBT). No evidence for a redshifted HI 21 cm emission signal was obtained in the GBT spectra of two absorbers, with the data on the third rendered unusable by terrestrial interference. The non-detections of HI 21 cm emission yield strong constraints on the HI masses of the associated galaxies, M$_HI < 2.3 10^9 (\Delta V/100)^1/2$ M$_ødot$ for the sub-DLA at $z = 0.0830$ towards J1553+3548, and M$_HI < 2.7 10^9 (\Delta V/100)^1/2$ M$_ødot$ for the DLA at $z = 0.0963$ towards J1619+3342, where $\Delta V$ is the HI 21 cm line width, in km s$^-1$. This continues the trend of low HI masses found in all low-$z$ DLAs and sub-DLAs that have been searched for redshifted HI 21 cm emission. Low-redshift absorbers with relatively low HI column densities, $few 10^20$ cm$^-2$, thus do not typically arise in massive gas-rich galaxies.

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