Low surface brightness galaxies around the HDF-S^*

I. Object extraction and photometric results

¹ Astronomical Institute, Ruhr-University Bochum, Universitätsstrasse 150, 44780 Bochum, Germany e-mail: lutz.haberzettl@astro.rub.de
² Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands

Received: 23 May 2006
Accepted: 5 December 2006

Abstract

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  ~ 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  ≥ 24 mag arcsec^-2, we applied a spatial filtering method in combination with an object search by eye. For brighter objects ( ≥ 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 108 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 ( ≥ 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  = 22.5 mag arcsec^-2 and diameters larger than the preselected size limit of 108. We selected three additional LSB candidates due to there extreme low blue central surface birghntess ( ≥ 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.