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arXiv · 1007.3936

A GBT Survey for HI 21 cm Absorption in the Disks and Halos of Low-Redshift Galaxies

Sanchayeeta Borthakur·Todd M. Tripp·Min S. Yun·David V. Bowen·Joseph D. Meiring·Donald G. York·Emmanuel Momjian
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Abstract

We present an HI 21 cm absorption survey with the Green Bank Telescope (GBT) of galaxy-quasar pairs selected by combining data from the Sloan Digital Sky Survey (SDSS) and the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey. Our sample consists of 23 sightlines through 15 low-redshift foreground galaxy - background quasar pairs with impact parameters ranging from 1.7 kpc up to 86.7 kpc. We detected one absorber in the GBT survey from the foreground dwarf galaxy, GQ1042+0747, at an impact parameter of 1.7 kpc and another possible absorber in our follow-up Very Large Array (VLA) imaging of the nearby foreground galaxy, UGC 7408. Both of the absorbers are narrow (FWHM of 3.6 and 4.8 km/s), have sub Damped Lyman alpha column densities, and most likely originate in the disk gas of the foreground galaxies. We also detected H I emission from three foreground galaxies, including UGC 7408. Although our sample contains both blue and red galaxies, the two H I absorbers as well as the H I emissions are associated with blue galaxies. We discuss the physical conditions in the 21 cm absorbers and some drawbacks of the large GBT beam for this type of survey.

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Sanchayeeta Borthakur, Todd M. Tripp, Min S. Yun, David V. Bowen, Joseph D. Meiring, Donald G. York, Emmanuel Momjian. 2010-10-27. A GBT Survey for HI 21 cm Absorption in the Disks and Halos of Low-Redshift Galaxies. https://doi.org/10.1088/0004-637x%2F727%2F1%2F52

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