H II Regions Within a Compact High Velocity Cloud. A Nearly Starless Dwarf Galaxy?

Journal
Date Issued
2015
Author(s)
•
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Mucciarelli, A.
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Beccari, G.
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Ibata, R.
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Battaglia, G.
•
Martin, N.
•
•
•
•
•
Fraternali, F.
DOI
Description
We acknowledge support from the LBT-Italian Coordination Facility and the Italian LBT Spectroscopic Reduction Center for the execution of observations, data distribution, and reduction. We are grateful to S. Bardelli, A. Bragaglia, A. Buzzoni, A. McConnachie, M. Mignoli, and P. Montegriffo for useful discussions and/or assistance. We are grateful to an anonymous referee for insightful suggestions. M.B. and F.F. acknowledge the support from the PRIN MIUR 2010-2011 project “The Chemical and Dynamical Evolution of the Milky Way and Local Group Galaxies,” prot. 2010LY5N2T. G.B. gratefully acknowledges support through a Marie-Curie action Intra European Fellowship, funded from the European Union Seventh Framework Program (FP7/2007-2013) under grant agreement Number PIEF-GA-2010-274151, as well as the financial support by the Spanish Ministry of Economy and Competitiveness (MINECO) under the Ramón y Cajal Program (RYC-2012-11537). This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This research has 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. Facilities: LBT , GALEX .
Abstract
Within the SECCO survey we identified a candidate stellar counterpart to the Ultra Compact High Velocity Cloud (UCHVC) HVC274.68+74.70-123 that was suggested by Adams et al. to be a possible mini halo within the Local Group of galaxies. The spectroscopic follow-up of the brightest sources within the candidate reveals the presence of two H ii regions whose radial velocity is compatible with a physical association with the UVHVC. The available data do not allow us to give a definite answer on the nature of the newly identified system. A few alternative hypotheses are discussed. However, the most likely possibility is that we have found a new faint dwarf galaxy residing in the Virgo cluster of galaxies, which we name SECCO 1. Independently of its actual distance, SECCO 1 displays a ratio of neutral hydrogen mass to V luminosity of {{M}H I}/{{L}V}≳ 20, by far the largest among local dwarfs. Hence, it appears to be a nearly starless galaxy and it may be an example of the missing links between normal dwarfs and the dark mini halos that are predicted to exist in large numbers according to the currently accepted cosmological model.

Based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University; and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University of Virginia.

Volume
800
Issue
1
Start page
L15
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2015ApJ...800L..15B
Rights
open.access
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