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Extinction Maps and Dust-to-gas Ratios in Nearby Galaxies with LEGUS

Kahre, L. and Cook, D. O. and Van Dyk, S. D. (2018) Extinction Maps and Dust-to-gas Ratios in Nearby Galaxies with LEGUS. Astrophysical Journal, 855 (2). Art. No. 133. ISSN 1538-4357. doi:10.3847/1538-4357/aab101.

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We present a study of the dust-to-gas ratios in five nearby galaxies: NGC 628 (M74), NGC 6503, NGC 7793, UGC 5139 (Holmberg I), and UGC 4305 (Holmberg II). Using Hubble Space Telescopebroadband WFC3/UVIS UV and optical images from the Treasury program Legacy ExtraGalactic UV Survey (LEGUS) combined with archival HST/Advanced Camera for Surveys data, we correct thousands of individual stars for extinction across these five galaxies using an isochrone-matching (reddening-free Q) method. We generate extinction maps for each galaxy from the individual stellar extinctions using both adaptive and fixed resolution techniques and correlate these maps with neutral H I and CO gas maps from the literature, including the H I Nearby Galaxy Survey and the HERA CO-Line Extragalactic Survey. We calculate dust-to-gas ratios and investigate variations in the dust-to-gas ratio with galaxy metallicity. We find a power-law relationship between dust-to-gas ratio and metallicity, consistent with other studies of dust-to-gas ratio compared to metallicity. We find a change in the relation when H2 is not included. This implies that underestimation of N_(H2) in low-metallicity dwarfs from a too-low CO-to-H_2 conversion factor X_(CO) could have produced too low a slope in the derived relationship between dust-to-gas ratio and metallicity. We also compare our extinctions to those derived from fitting the spectral energy distribution (SED) using the Bayesian Extinction and Stellar Tool for NGC 7793 and find systematically lower extinctions from SED fitting as compared to isochrone matching.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Kahre, L.0000-0002-2037-3096
Cook, D. O.0000-0002-6877-7655
Van Dyk, S. D.0000-0001-9038-9950
Additional Information:© 2018 The American Astronomical Society. Received 2017 November 30; revised 2018 February 13; accepted 2018 February 15; published 2018 March 16. This work is based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy under NASA contract NAS 5-26555. These observations are associated with program 13364 (LEGUS). Support for program 13364 was provided by NASA through a grant from the Space Telescope Science Institute. LK and RAW acknowledge support from the Space Telescope Science institute (grant Numbers HST-GO-13773.003-A). LK would additionally like to acknowledge support from the Gemini Observatory in La Serena, Chile. MF acknowledges support from the Science and Technology Facilities Council (grant Number ST/P000541/1). DAG kindly acknowledges financial support by the German Research Foundation (DFG) through program GO 1659/3-2. GA acknowledges support from the Science and Technology Facilities Council (ST/P000541/1 and ST/M503472/1). We would also like to thank the anonymous referee for useful comments that helped improve the paper. Software: BEAST (Gordon et al. 2016), DOLPHOT photometric package (Dolphin & Kennicutt 2002), PARSEC (Bressan et al. 2012).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASANAS 5-26555
Hubble Space TelescopeHST-GO-13773.003-A
Science and Technology Facilities Council (STFC)ST/P000541/1
Deutsche Forschungsgemeinschaft (DFG)GO 1659/3-2
Science and Technology Facilities Council (STFC)ST/M503472/1
Gemini ObservatoryUNSPECIFIED
Subject Keywords:dust, extinction – galaxies: dwarf – galaxies: ISM – galaxies: photometry – galaxies: spiral – ISM: general
Issue or Number:2
Record Number:CaltechAUTHORS:20180405-154527811
Persistent URL:
Official Citation:L. Kahre et al 2018 ApJ 855 133
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85668
Deposited By: Tony Diaz
Deposited On:05 Apr 2018 22:54
Last Modified:15 Nov 2021 20:31

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