University Of Tasmania

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Galaxies on the Blue Edge

journal contribution
posted on 2023-05-16, 19:45 authored by Cabanela, JE, John DickeyJohn Dickey
We have successfully constructed a catalog of H I-rich galaxies selected from the Minnesota Automated Plate Scanner catalog of the Palomar Observatory Sky Survey (POSS I), based solely on optical criteria. We identify H I-rich candidates by selecting the bluest galaxies at a given apparent magnitude, those galaxies on the blue edge of POSS I color-magnitude parameter space. Subsequent 21 cm observations on the upgraded Arecibo 305 m dish detected over 50% of the observed candidates. The detected galaxies are H I-rich, with H I masses comparable to "normal" high surface brightness disk galaxies, and they have gas mass-to-light ratios ranging from 0.1 to 4.8 (in solar units). Comparison of our candidate galaxies with known low surface brightness galaxies (hereafter LSBs) shows that they exhibit similar optical and H I properties to that population. We also show that previously identified LSBs, including several LSBs with red B-V colors, preferentially occupy the blue edge of POSS I color-magnitude parameter space. Their presence on the blue edge appears to be a selection effect due to differing plate limits in the two POSS I bandpasses. This suggests the POSS I is a good filter for separating galaxies on the higher surface brightness end of the LSB population from the general population of galaxies in the night sky.


Publication title

The Astronomical Journal








School of Natural Sciences


University of Chicago Press

Place of publication

Chicago, USA

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the physical sciences

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