Szomoru, Arpad; Guhathakurta, Puragra; van Gorkom, Jacqueline H.; Knapen, Johan H.; Weinberg, David H.; Fruchter, Andrew S.
Bibliographical reference
The Astronomical Journal, vol. 108, no. 2, p. 491-506
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8
1994
Citations
37
Refereed citations
29
Description
We analyze the properties of a sample of galaxies identified in a 21cm,
H I-line survey of selected areas in the Perseus-Pisces supercluster and
its foreground void. Twelve fields were observed in the supercluster,
five of them (target fields) centered on optically bright galaxies, and
the other seven (blank fields) selected to contain no bright galaxies
within 45 min. of their centers. We detected nine previously
uncatalogued, gas-rich galaxies, six of them in the target fields. We
also detected H I from seven previously catalogued galaxies in these
fields. Observations in the void covered the same volume as the 12
supercluster fields at the same H I-mass sensitivity, but no objects
were detected. Combining out H I data with optical broadband and H alpha
imaging, we conclude that the properties of H I-selected galaxies do not
differ substantially from those of late-type galaxies found in optical
surveys. In particular, the galaxies in our sample do not appear to be
unusually faint for their H I mass, or for their circular velocity. We
find tentative evidence for a connection between optical surface
brightness and degree of isolation, in the sense that low surface
brightness galaxies tend to be more isolated. The previously catalogued,
optically bright galaxies in our survey volume dominate the total H I
mass density and cross section; the uncatalogued galaxies contribute
only approximately 19 percent of the mass and approximately 12 percent
of the cross section. Thus, existing estimates of the density and cross
section of neutral hydrogen, most of which are based on optically
selected galaxy samples, are probably accurate. Such estimates can be
used to compare the nearby universe to the high-redshift universe probed
by quasar absorption lines.