[astro-ph/0510259] The Cosmological Unimportance of Low Surface Brightness Galaxies

Authors:  C. C. Hayward, J. A. Irwin, J. N. Bregman
Abstract:  We have searched for Type Ia supernovae (SNe Ia) in the local (d < 60 Mpc) Universe using Northern Sky Variability Survey (NSVS) data collected from the nightly optical surveys of the Robotic Optical Transient Search Experiment} (ROTSE) Telescope. It was hoped that SNe Ia would provide a means to find previously-unknown low surface brightness (LSB) galaxies or displaced stars that would otherwise be very difficult to detect. The ROTSE data allowed us to survey 19,000 square degrees at declinations north of 0 degrees, but we did not find a single SN Ia in a period of time covering roughly one year. Using known SNe Ia rates in bright galaxies, we set an upper limit on the optical luminosity density, L_B, of LSBs in the local Universe. Using mean LSB baryonic and dynamical mass-to-light ratios, we find 95% upper limits for LSBs of L_B \le 2.53 x 10^8 L_{B, solar} Mpc^{-3}, Omega_b \le 0.0040, and Omega_m \le 0.036. We conclude that LSBs and displaced stars are not a major constituent of matter in the local Universe.
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Anze Slosar
Posts: 183
Joined: September 24 2004
Affiliation: Brookhaven National Laboratory

[astro-ph/0510259] The Cosmological Unimportance of Low Surf

Post by Anze Slosar » October 11 2005

Apart from hilarious title this piece of work seems to be quite clever: if galaxy is too faint to be detected alone there should still be SN Ias going off every now and then and therefore seeing a lone SN would indicate either a lone star (well a binary system) or a very faint galaxy. By not detecting anything the authors conclude that LSB galaxies are negligible so everything is good and dandy.

Could we find any loopholes in their argument? I think it would be interesting to repeat this in clusters of galaxies (deeper and narrower) to look for lone stars/LSBs in there...

Pier Stefano Corasaniti
Posts: 43
Joined: November 11 2004
Affiliation: LUTH, Observatoire de Paris-Meudon

[astro-ph/0510259] The Cosmological Unimportance of Low Surf

Post by Pier Stefano Corasaniti » October 11 2005

I have given a quick look at this very interesting paper, indeed the strategy seems to be very smart for tracking the LSBG, however I wonder whether their actual results are limited by selection effects due to the experimental sensitivity. After all when they look for known SNe Ia that should be present in their dataset, they found none, there is only one SNIa candidate during the period of time the data have been collected, which resulted to be too faint for being detected in their survey. Can it be that most of the SNe Ia in LSBG are fainter than ROTSE telescope sensitivity?

Perhaps they have accounted for this in their final estimate and I have just missed that point.

V. Antonuccio-Delogu
Posts: 1
Joined: December 02 2004
Affiliation: INAF - Catania Astrophysical Observatory

[astro-ph/0510259] The Cosmological Unimportance of Low Surf

Post by V. Antonuccio-Delogu » October 13 2005

Some time ago P. Padoan, R. Jimenez and myself published a paper where we tried to make synthetic pop. models of LSB (ApJ 481, L27, 1997). We found that models with a single episode of stellar formation, of very low activity and happening very early, could quite well describe the observed B vs. B-V diagrams for LSBs. I wonder how many SNs could be produced under these conditions, also taking into account the fact that often the surface density of the stellar discs of LSBs is lower than for "normal" disc galaxies. Probably very few.

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