HI observations of loose galaxy groups

I. Data and global properties

¹ DAEC, UMR CNRS 8631, Observatoire de Paris, Section de Meudon, 5 place Jules Janssen, 92195 Meudon Cedex, France e-mail: wim.vandriel@obspm.fr; delphine.ragaigne@obspm.fr
² Unité Scientifique Nançay, USR CNRS B704, Observatoire de Paris, 18330 Nançay, France
³ Department of Physics and Astronomy, Texas Christian University, Box 298840, Fort Worth, TX 76129, USA e-mail: p.marcum@tcu.edu
⁴ Astronomy Department, University of Madison-Wisconsin, 475 N. Charter St., Madison WI 53706-1582, USA e-mail: jsg@astro.wisc.edu; ewilcots@astro.wisc.edu
⁵ Faculté des Sciences et des Techniques, Université de Tours, Avenue Monge, 37000 Tours, France

Corresponding author: W. van Driel, wim.vandriel@obspm.fr

Received: 24 July 2001
Accepted: 4 September 2001

Abstract

At Nançay, 21-cm H i line observations were made of 15 spiral-dominated loose groups of galaxies, divided into two samples: an "interacting" sample containing at least one pair of interacting galaxies, and a "control" sample having no optical evidence of interactions or morphological disturbances among the group members. The interacting sample consists of 62 galaxies representing 9 different groups, and the control sample contains 40 galaxies representing 6 groups. Of the 91 galaxy and galaxy pairs observed, 74 were detected, while upper limits were placed on the remaining 17 objects. These homogeneous H i data, which will be used in future analyses, provide comparative information on the H i content of groups and serve as a probe of the vicinity of the target spirals for H i clouds or very low surface brightness gas-rich galaxies.