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Published December 11, 2012 | Published
Journal Article Open

Pre-existing dwarfs, tidal knots and a tidal dwarf galaxy: an unbiased H_I study of the gas-rich interacting galaxy group NGC 3166/9

Abstract

We present Arecibo Legacy Fast ALFA (ALFALFA) and follow-up Giant Metrewave Radio Telescope (GMRT) H _I observations of the gas-rich interacting group NGC 3166/9. The sensitive ALFALFA data provide a complete census of H _I-bearing systems in the group while the high-resolution GMRT data elucidate their origin, enabling one of the first unbiased physical studies of gas-rich dwarf companions and the subsequent identification of second-generation, tidal dwarf galaxies in a nearby group. The ALFALFA maps reveal an extended H _I envelope around the NGC 3166/9 group core, which we mosaic at higher resolution using six GMRT pointings spanning ∼1 deg^2. A thorough search of the GMRT data cube reveals eight low-mass objects with gas masses ranging from 4 × 10^7 to 3 × 10^8 M_⊙ and total dynamical masses up to 1.4 × 10^9 M_⊙. A comparison of the H I fluxes measured from the GMRT data to those measured in the ALFALFA data suggests that a significant fraction (∼60 per cent) of the H _I is smoothly distributed on scales greater than 1 arcmin (∼7 kpc at the NGC 3166/9 distance). We compute stellar masses and star formation rates for the eight low-mass GMRT detections, using ancillary Sloan Digital Sky Survey (SDSS) and Galaxy Evolution Explorer (GALEX) data, and use these values to constrain their origin. Most of the detections are likely to be either pre-existing dwarf irregular galaxies or short-lived, tidally formed knots; however, one candidate, AGC 208457, is clearly associated with a tidal tail extending below NGC 3166, exhibits a dynamical to gas mass ratio close to unity and has a stellar content and star formation rate that are broadly consistent with both simulated as well as candidate tidal dwarf galaxies from the literature. Our observations therefore strongly suggest that AGC 208457 is a tidal dwarf galaxy.

Additional Information

© 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012. Accepted 2012 September 11. Received 2012 September 10; in original form 2012 April 7. Article first published online: 20 Nov. 2012. We thank the staff of the GMRT for facilitating our interferometric observations and the many ALFALFA team members who contributed to producing the data used here. Thank you to the reviewer, P.-A. Duc, for his numerous suggestions to improve the clarity of this paper. KS acknowledges funding from the National Sciences and Engineering Research Council of Canada. The ALFALFA team at Cornell is supported by grants from the US National Science Foundation NSF/AST-0607007 and AST-1107390 and by a grant from the Brinson Foundation. The GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. The Arecibo Observatory is operated by SRI International under a cooperative agreement with the National Science Foundation (AST-1100968) and in alliance with Ana G. Méndez-Universidad Metropolitana and the Universities Space Research Association. This research made use of Montage, funded by the National Aeronautics and Space Administration's Earth Science Technology Office, Computation Technologies Project, under Cooperative Agreement Number NCC5-626 between NASA and the California Institute of Technology. Montage is maintained by the NASA/IPAC Infrared Science Archive. Some of the data presented in this paper were obtained from the Multimission Archive at the Space Telescope Science Institute (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts. This research has also made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

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August 22, 2023
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