GMRT Observations of the Group Holmberg 124 + Preliminary results on Holm 377 and Holm 565 N.G.Kantharia 1 , S. Ananthakrishnan 2 , R. Nityananda 3 , Ananda Hota 4 National Centre for Radio Astrophysics, Tata Institute of Fundamental Research Post Bag 3, Ganeshkhind, Pune - 411007, India 1 ngk@ncra.tifr.res.in, 2 ananth@ncra.tifr.res.in, 3 rajaram@ncra.tifr.res.in, 4 hota@ncra.tifr.res.in Abstract: We discuss the results of a multi-frequency radio study using the Giant Metrewave Radio Telescope (GMRT) of the group Holmberg 124 which comprises galaxies: NGC 2820, NGC 2805, Mrk 108 and NGC 2814. We detect the radio continuum bridge connecting NGC 2820 with NGC 2814 and find it to have a steep spectrum with index −1.8 at frequencies below 1.4 GHz. A large asymmetrical loop is detected in the 21 cm line of HI to the north of NGC 2820. We also report detection of a dwarf galaxy with mass ∼ 10 8 M ⊙ to the north-west of NGC 2820. We conclude that both tidal interaction and ram pressure stripping due to the motion of the galaxies in the intragroup medium have likely influenced the evolution of this group [1]. Preliminary results from a radio continuum study of Holmberg 377 and Holmberg 565 at 330 MHz using GMRT, in particular, the first positive detection of interaction between NGC 4302 and NGC 4298 are also presented. Introduction A multi-frequency radio study of poor groups of galaxies is essential alongwith other wave-bands such as X-rays and optical to understand the evolution of small groups of galaxies and ultimately formation of clusters and the largest structures in the universe since different wave-bands trace different constituents. While X-rays traces hot gas (T e = 10 6 − 10 7 K) of the intragroup medium (IGrM) which emits through free-free emission and spectral lines, optical emission traces star forming regions in galaxies. Radio continuum, on the other hand, traces the relativistic electron plasma in a magnetic field and the HI 21cm line traces cold neutral gas. Thus, all the above diagnostics are required to obtain for understanding the evolution of the group, its member galaxies IGrM. In this paper we discuss our results of a multi-frequency radio continuum and HI 21cm study of the group Holmberg 124 using GMRT. We detect a steep spectrum bridge connecting NGC 2820 and NGC 2814 and a large asymmetrical HI loop to the north of NGC 2820. Additionally, preliminary results from GMRT observations of Holmberg 377 and Holmberg 565 are presented [2]. Observations Table 1 summarizes details of GMRT [3] observations on Holm 124, Holm 377 and Holm 565. Although we have completed a comprehensive multi-frequency study of Holm 124, a similar study is being undertaken for Holm 377 and Holm 565 as is evident from the blank boxes in the table. Using NVSS and FIRST data on the latter two galaxies, preliminary results are presented in this paper. Note that the angular resolution at 330 MHz obtained on the three galaxies is different and is caused by editing data for RFI. Typical dynamic range at 330 MHz ranged from 1000 to 2500. Results and Discussion Holmberg 124 Fig 1 presents the low resolution 330 MHz image and the high resolution 1280 MHz image of NGC 2820, NGC 2814 and Mrk 108 (the triplet). NGC 2805 is about 8’ south of the triplet and is not 1