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First Results from the MADCASH Survey: A Faint Dwarf Galaxy Companion to the Low-mass Spiral Galaxy NGC 2403 at 3.2 Mpc

Carlin, Jeffrey L. and Sand, David J. and Price, Paul and Willman, Beth and Karunakaran, Ananthan and Spekkens, Kristine and Bell, Eric F. and Brodie, Jean P. and Crnojević, Denija and Forbes, Duncan A. and Hargis, Jonathan and Kirby, Evan and Lupton, Robert and Peter, Annika H. G. and Romanowsky, Aaron J. and Strader, Jay (2016) First Results from the MADCASH Survey: A Faint Dwarf Galaxy Companion to the Low-mass Spiral Galaxy NGC 2403 at 3.2 Mpc. Astrophysical Journal Letters, 828 (1). Art. No. L5. ISSN 2041-8205.

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We report the discovery of the faintest known dwarf galaxy satellite of a Large Magellanic Cloud (LMC) stellar-mass host beyond the Local Group (LG), based on deep imaging with Subaru/Hyper Suprime-Cam. Magellanic Analog Dwarf Companions And Stellar Halos (MADCASH) J074238+652501-dw lies ~35 kpc in projection from NGC 2403, a dwarf spiral galaxy at D ≈ 3.2 Mpc. This new dwarf has M_g = -7.4 ± 0.4 and a half-light radius of 168 ± 70 pc, at the calculated distance of 3.39 ± 0.41 Mpc. The color–magnitude diagram reveals no evidence of young stellar populations, suggesting that MADCASH J074238+652501-dw is an old, metal-poor dwarf similar to low-luminosity dwarfs in the LG. The lack of either detected HI gas (M_(HI)/L_V < 0.69 M⊙/L⊙, based on Green Bank Telescope observations) or GALEX NUV/FUV flux enhancement is consistent with a lack of young stars. This is the first result from the MADCASH survey, which is conducting a census of the stellar substructure and faint satellites in the halos of Local Volume LMC analogs via resolved stellar populations. Models predict a total of ~4–10 satellites at least as massive as MADCASH J074238+652501-dw around a host with the mass of NGC 2403, with 2–3 within our field of view, slightly more than the one such satellite observed in our footprint.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Carlin, Jeffrey L.0000-0002-3936-9628
Sand, David J.0000-0003-4102-380X
Willman, Beth0000-0003-2892-9906
Spekkens, Kristine0000-0002-0956-7949
Kirby, Evan0000-0001-6196-5162
Peter, Annika H. G.0000-0002-8040-6785
Romanowsky, Aaron J.0000-0003-2473-0369
Strader, Jay0000-0002-1468-9668
Additional Information:© 2016 The American Astronomical Society. Received 2016 July 5; revised 2016 August 6; accepted 2016 August 7; published 2016 August 25. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. We thank Fumiaki Nakata and Rita Morris for assistance at the Subaru Telescope, Mike Beasley for attempting to obtain a spectrum of the new dwarf, the referee for helpful comments, and Michael Wood-Vasey for conversations that helped improve our photometry. J.L.C. and B.W. acknowledge support by NSF Faculty Early Career Development (CAREER) award AST-1151462. D.J.S. acknowledges support from NSF grant AST-1412504. The work of D.J.S. was performed at the Aspen Center for Physics, which is supported by NSF grant PHY-1066293. J.P.B. and A.R. are supported by NSF grant AST-1211995. Some data presented here were obtained from the Mikulski Archive for Space Telescopes (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. The Pan-STARRS1 Surveys have been made possible through contributions of the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, Queen’s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation under grant AST-1238877, the University of Maryland, Eotvos Lorand University (ELTE), and the Los Alamos National Laboratory. Facilities: Subaru (Hyper Suprime-Cam), GALEX, GBT, HST (ACS).
Funding AgencyGrant Number
Subject Keywords:dark matter – galaxies: dwarf – galaxies: formation – galaxies: halos
Record Number:CaltechAUTHORS:20160829-083636247
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Official Citation:Jeffrey L. Carlin et al 2016 ApJ 828 L5
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69983
Deposited By: Tony Diaz
Deposited On:29 Aug 2016 17:28
Last Modified:30 Nov 2017 18:20

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