Low surface brightness galaxies around the HDF-S. I. Object extraction and photometric results

Aims:The aim of this study is to extend the parameter space for Low Surface Brightness (LSB) galaxies to reach lower central surface brightnesses, smaller sizes and higher number densities.
Methods: This study reports on photometric results of a search for LSB galaxies in a 0.76 deg² field centered on the Hubble Deep Field-South (HDF-S). We present results from photometric analysis of the derived sample galaxies and compare number densities to results of former surveys. We used public data from the NOAO Deep Wide-Field survey and the multi-wavelength Goddard Space Flight Center survey. The former reaches a limiting surface brightness of μ_B_W ~ 29 mag arcsec^-2 and is therefore one of the most sensitive ground based data sets systematically analyzed for LSB galaxies. The search was performed with two methods. For faint objects, with a blue central surface brightness of μ_B_W ≥ 24 mag arcsec^-2, we applied a spatial filtering method in combination with an object search by eye. For brighter objects (μ_B_W ≥ 22 mag arcsec^-2) we used an automatic search routine. To reduce the contamination by High Surface Brightness (HSB) galaxies at higher redshift, mimicking LSBs due to the "Tolman Dimming" effect, we placed a lower diamater limit of 10.8 arcsec and compared the colors of our candidate galaxies with the redshift tracks of 5 "standard" HSB galaxy types.
Results: We report the detection of 37 galaxies with low apparent central surface brightness (μ_B_W ≥ 22 mag arcsec^-2). Using color-color diagrams we were able to derive a subsample of 9 LSB galaxy candidates with intrinsic central surface brightnesses below μ_0, B_W = 22.5 mag arcsec^-2 and diameters larger than the preselected size limit of 10.8 arcsec. We selected three additional LSB candidates due to there extreme low blue central surface birghntess (μ_B_W ≥ 25 mag arcsec^-2). These galaxies were only found in the larger and more sensitive NOAO data. So finally we derived a sample of 12 LSB galaxy candidates and therefore this survey results in a four times higher surface density than other CCD based surveys for field galaxies before.

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