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Optical Properties of the HI-selected Galaxies from the Arecibo Dual Beam Survey. John Salzer, Nyla Tresser, Samantha Stevenson & Hart Webb (Wesleyan University) Jessica Rosenberg (Harvard/Smithsonian CfA). What will ALFALFA galaxies look like in the optical?.
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HI-selected Galaxies from the
Arecibo Dual Beam Survey
John Salzer, Nyla Tresser, Samantha Stevenson
& Hart Webb (Wesleyan University)
Jessica Rosenberg (Harvard/Smithsonian CfA)
Arecibo, Puerto Rico
305-m Radio Telescope
The galaxies detected in the ADBS exhibit a broad range of HI masses, with a median value of log(MHI) = 9.21 and a tail extending to values below 108 solar masses.
As one would expect from such a sample, lower HI mass galaxies are detected nearby, whereas high HI mass galaxies are detected at all distances covered by the survey.
When looked at in terms of its optical properties, the ADBS sample detects far lower luminosity galaxies than does the Zwicky Catalog magnitude-limited sample (B<15.5) at all distances.
All Observations for this project have been obtained on the WIYN 0.9m telescope on Kitt Peak, which is operated jointly by a consortium of universities that includes Wesleyan.
Galaxies imaged through B & V filters with 2k x 2k
CCD with 0.6 arcsec pixels.
Apparent magnitudes. Nearly half of the ADBS galaxies have B > 15.5. These fainter galaxies are not included in magnitude-limited catalogs.
Morphological Classifications. The ADBS is a roughly equal mix of spirals and
irregulars (including the LSB galaxies). There is a small number of early types and compact objects.
Example LSB dwarf galaxy in the ADBS
045254+2310 (a.k.a. the fish)
B-V colors. The median color is B-V = 0.47, far bluer than in typical magnitude-limited samples. The dwarf galaxies are particularly blue.
Color vs. Galaxy type. We can investigate the properties of the ADBS galaxies as a function of their galaxy class - in this case B-V color.
Absolute magnitudes. There is a solid component of luminous galaxies included in the ADBS, as well as a large contingent of dwarf systems. The median MB is -18.29.
Luminosity - Color Diagram. The ADBS galaxies display a weak relationship between MB and color, in the sense that dwarfier galaxies tend to be bluer. There are many outliers, however.
Central Surface Brightness vs. Luminosity. The major galaxy types are indicated by the plot symbols. There is a clear trend, but with much scatter.
HI mass-to-light ratio vs Luminosity. We see an inverse relationship between the fractional HI mass (HI mass-to-light ratio) and absolute magnitude such that the more luminous an object the lower the fractional gas content it will have.
Velocity circle diagrams (analogous to cone diagrams) show the UZC galaxies
(small dots) and the ADBS galaxies (open circles).
RA is “circular”, declination is suppressed and
velocity moves outwards. Clusters, filaments and
voids can be seen.
To first order, the ADBS galaxies follow the
spatial distribution of the UZC galaxies. This is
to no surprise since ~50% of the ADBS galaxies are in the UZC.
A weak relationship is seen in the sense that the HI mass in low density environments is slightly greater than in high-density environments. This may be to due to gas stripping in the denser environments.