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A Deeper Look at Faint Hα Emission in Nearby Dwarf Galaxies

Lee, Janice C. and Veilleux, Sylvain and McDonald, Michael and Hilbert, Bryan (2016) A Deeper Look at Faint Hα Emission in Nearby Dwarf Galaxies. Astrophysical Journal, 817 (2). Art. No. 177. ISSN 0004-637X. doi:10.3847/0004-637X/817/2/177.

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We present deep Hα imaging of three nearby dwarf galaxies, carefully selected to optimize observations with the Maryland-Magellan Tunable Filter (MMTF) on the Magellan 6.5 m telescope. An effective bandpass of ~13 Å is used, and the images reach 3σ flux limits of ~8 × 10^(−18) erg s^(−1) cm^(−2), which is about an order of magnitude lower than standard narrowband observations obtained by the most recent generation of local Hα galaxy surveys. The observations were originally motivated by the finding that the Hα/FUV flux ratio of galaxies systematically declines as global galactic properties such as the star formation rate (SFR) and stellar mass decrease. The three dwarf galaxies selected for study have SFRs that, when calculated from their Hα luminosities using standard conversion recipes, are ~50% of those based on the FUV. Follow-up studies of many of the potential causes for the trends in the Hα/FUV flux ratio have been performed, but the possibility that previous observations have missed a non-negligible fraction of faint ionized emission in dwarf galaxies has not been investigated. The MMTF observations reveal both diffuse and structured Hα emission (filaments, shells, possible single-star H ii regions) spanning extents up to 2.5 times larger relative to previous observations. However, only up to an additional ~5% of Hα flux is captured, which does not account for the trends in the Hα/FUV ratio. Beyond investigation of the Hα/FUV ratio, the impact of the newly detected extended flux on our understanding of star formation, the properties of H ii regions, and the propagation of ionizing photons warrant further investigation.

Item Type:Article
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URLURL TypeDescription Paper
Lee, Janice C.0000-0002-2278-9407
Veilleux, Sylvain0000-0002-3158-6820
McDonald, Michael0000-0001-5226-8349
Additional Information:© 2016 The American Astronomical Society. Received 2015 August 21; accepted 2015 December 18; published 2016 February 1. S.V. and M.M. acknowledge partial support from NSF grants AST-0606932 and AST-1009583. We thank the referee for a constructive report that helped to improve this paper. Facility: Magellan:Baade (IMACS).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:galaxies: dwarf – galaxies: ISM – galaxies: star formation
Issue or Number:2
Record Number:CaltechAUTHORS:20160304-092918503
Persistent URL:
Official Citation:Janice C. Lee et al 2016 ApJ 817 177
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:65075
Deposited By: Tony Diaz
Deposited On:04 Mar 2016 17:35
Last Modified:10 Nov 2021 23:39

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