The galaxy catalogs used by the BRASS project were developed to provide statistically-optimized probability of supernovae discovery, given our equipment profile, operation conditions and desired imaging productivity.

Several papers are available in the professional literature (just a few of them are listed in the Bibliography) describing the statistical relationships between the rate of supernovae in galaxies and many astrophysical parameters such as galactic mass (or luminosity), Hubble morphological classification, apparent size, inclination angle, redshifts, and others. Most of those articles are based on statistical data provided by historical SN searches since the pioneering efforts of Fritz Zwicky and Walter Baade by mid-20th century.

The design of our catalogs departs from known galaxy catalogs such as ESO-Uppsala, UGC, PGC, NGC and IC, and take into account as selection criteria all the relationships found in professional papers plus a few constraints imposed by our instrumental limitations and desired imaging productivity. As an additional constraint, we have limited our sample to Southern galaxies (located South of the declination –17 degrees), to concentrate our search in regions less explored by other current supernovae searches.

As a result, our catalogs are usually smaller than other counterparts (current revised Version 1.0 contains less than 1200 galaxies; Version 2.0, to be effective in the second half of 2005, contains slightly more than 3600 galaxies), but are expected to provide an optimized relationship between supernovae occurrence and the average number of images needed to find each SN. Our first results appear to confirm our expectations: seven SNe were discovered over almost 21 000 images taken between June 2004 and late May 2005. That means an average of about 3000 images per supernova discovered, which compares to a generally-accepted figure of 5000 images per SN. Although our sample (less than one year data) is still very small to allow a final conclusion on this question, it appears that, through adequate selection of galaxies based on statistical probabilities of SNe rates, it is possible to improve the SN discovery productivity. This is particularly useful for our search in Brazil, since the prevailing hot and wet climate in our country usually limits the number of clear nights we have available for our search activities.

Bibliography:

Cappelaro et al, The Rate of Supernovae, Part I, A&A 268: 472-482, 1993
Cappelaro et al, The Rate of Supernovae, Part II, A&A 273: 383-392, 1993
Tammann, Löffler, Schröder, The Galactic Supernovae Rate, ApJS 92: 487-493, 1994
Van den Bergh, Li and Filipenko, Classifications of Host Galaxies of Supernovae, arXiv : astro-ph/0204298 v1, 2002