An HI and Optical Search for Dwarf Galaxies in the Hercules Cluster

Authors: J. Iglesias-Pàramo, W. van Driel, P.-A. Duc, P. Papaderos,
J. M. Vílchez, V. Cayatte, C. Balkowski, K. O'Neil, J. Dickey, H. Hernàdez, T.X. Thuan
2003, accepted by A&A

ABSTRACT:

The present study is aimed at a sample of 22 galaxies detected in the blind selected on an HI line width smaller than 270 km/s and 4 others with only tentative optical counterparts on the Palomar Sky Survey. Sensitive single-dish HI line spectra were obtained for 20 of them, and for one (47-154) the VLA detection was not confirmed. Optical surface photometry was obtained of 10 objects, for 8 of which optical spectroscopy was obtained as well. Based on various selection criteria, two (ce-143 and ne-204) can be classified as dwarfs. The objects of which optical observations were made show star formation properties similar to those of published samples of actively star forming galaxies, and approximately half of them have properties intermediate between those of dwarf galaxies and low-luminosity disc galaxies. No optical redshifts could be obtained for two of the galaxies (sw-103 and sw-194) and their physical association with the HI clouds detected at their positions therefore remains uncertain. Unique among the objects is the Tidal Dwarf Galaxy ce-061 in a tail of the IC 1182 merger system.

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