Why this survey?

Interferometric observations of atomic hydrogen (HI) in galaxies play a pivotal role in studies of nearby galaxies. Several extensive HI 21cm surveys of nearby galaxies have been performed in the last few decades through different radio interferometers of the world. These surveys comprise a large number of data sets of the nearby galaxies. With this large and increasing volume of archival data, it has now become essential to appraise the existing archival data so that this large sample volume can be used to examine the completion and coverage of sources. Besides that, most of these surveys have been performed in different set-ups, consisting of a small number of galaxies and aimed to explore some particular science cases. The detailed analysis and results based on these data are published for some targets, but there are no reported results for a significant fraction of the sources. Also, for the sources for which the results are published, the analysis is very heterogeneous, the data products are not readily available, and often, for some of the key analyses, better, more accurate and well-established methods compared to the ones used (e.g., rotation curve estimation from the image cube instead of using the 2-D velocity field) are now available. Considering the above points and to explore the potential of these archival data, we constructed a sample from all the galaxies observed in 21cm by the Giant Meter wave Radio Telescope (GMRT). This results in a total of 515 galaxies, the largest sample to date. We intend to analyze all the data uniformly and carry out different exciting science cases for this large number of galaxies that have different properties, morphology and are in different environments. We have started carrying out this exercise of a GMRT ARChIve Atomic gas survey (GARCIA) with a pilot sample of eleven galaxies and explored different science cases. We plan to make the science-ready data products available publicly in a phased manner for the entire sample.