A study of H I-selected galaxies in the Hercules cluster^*

¹ Laboratoire d'Astrophysique de Marseille, Traverse du Siphon – Les Trois Lucs, 13376 Marseille, France e-mail: jorge.iglesias@oamp.fr
² Observatoire de Paris, GEPI, CNRS-UMR 8111 and Université Paris 7, 92195 Meudon Cedex, France e-mail: wim.vandriel@obspm.fr; veronique.cayatte@obspm.fr; chantal.balkowski@obspm.fr
³ CNRS URA 2052 and CEA, DSM, DAPNIA, Service d'Astrophysique, 91191 Gif-sur-Yvette Cedex, France e-mail: paduc@cea.fr
⁴ Universitäts-Sternwarte, Geismarlandstrasse 11, 37083 Göttingen, Germany e-mail: papade@uni-sw.gwdg.de
⁵ Instituto de Astrofísica de Andalucía (CSIC), Granada, Spain e-mail: jvm@iaa.es
⁶ Arecibo Observatory, HC3 Box 53995, Arecibo, Puerto Rico 00612, USA e-mail: koneil@naic.edu, hhernand@naic.edu
⁷ Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455, USA e-mail: john@astro.umn.edu
⁸ Astronomy Department, University of Virginia, Charlottesville, VA 22903, USA e-mail: txt@astro.virginia.edu

Corresponding author: J. Iglesias-Páramo, jorge.iglesias@oamp.fr

Received: 26 April 2002
Accepted: 9 April 2003

Abstract

The present study focuses on a sample of 22 galaxies detected in the blind VLA H i survey of the Hercules cluster by Dickey ([CITE]), 18 of which were selected on an H i line width smaller than 270 km s^-1 and 4 others with only tentative optical counterparts in the Palomar Sky Survey. Sensitive single-dish H i line spectra were obtained for 20 of them, and for one the VLA detection was not confirmed. Optical surface photometry has been carried out for 10 objects, for 8 of which optical spectroscopy was obtained as well. Based on various criteria, we classify two sample galaxies (ce-143 and ne-204) as genuine dwarfs whereas the remaining sample objects are found to be intrinsically luminous galaxies. For those objects investigated in optical wavelengths we determine properties similar to those of actively star-forming galaxies, and find that approximately one half of them has properties intermediate between those of dwarf galaxies and low-luminosity disc galaxies. No optical redshifts could be determined for two of the galaxies (sw-103 and sw-194) and their physical association with the H i clouds detected at their positions therefore remains uncertain. A particularly interesting object in our sample is the Tidal Dwarf Galaxy candidate ce-061 in the galaxy merger IC 1182.