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

Kahre, L.; Walterbos, R.A.; Kim, H.; Thilker, D.; Calzetti, D.; Lee, J.C.; Sabbi, E.; Ubeda, L.; Aloisi, A.; Cignoni, M.; Cook, D.O.; Dale, D.A.; Elmegreen, B.G.; Elmegreen, D.M.; Fumagalli, M.; Gallagher, J.S. III; Gouliermis, D.A.; Grasha, K.; Grebel, E.K.; Hunter, D.A.; Sacchi, E.; Smith, L.J.; Tosi, M.; Adamo, A.; Andrews, J.E.; Ashworth, G.; Bright, S.N.; Brown, T.M.; Chandar, R.; Christian, C.; de Mink, S.E.; Dobbs, C.; Evans, A.S.; Herrero, A.; Johnson, K.E.; Kennicutt, R.C.; Krumholz, M.R.; Messa, M.; Nair, P.; Nota, A.; Pellerin, A.; Ryon, J.E.; Schaerer, D.; Shabani, F.; Van Dyk, S.D.; Whitmore, B.C.; Wofford, A.

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Authors

L. Kahre

R.A. Walterbos

H. Kim

D. Thilker

D. Calzetti

J.C. Lee

E. Sabbi

L. Ubeda

A. Aloisi

M. Cignoni

D.O. Cook

D.A. Dale

B.G. Elmegreen

D.M. Elmegreen

J.S. III Gallagher

D.A. Gouliermis

K. Grasha

E.K. Grebel

D.A. Hunter

E. Sacchi

L.J. Smith

M. Tosi

A. Adamo

J.E. Andrews

G. Ashworth

S.N. Bright

T.M. Brown

R. Chandar

C. Christian

S.E. de Mink

C. Dobbs

A.S. Evans

A. Herrero

K.E. Johnson

R.C. Kennicutt

M.R. Krumholz

M. Messa

P. Nair

A. Nota

A. Pellerin

J.E. Ryon

D. Schaerer

F. Shabani

S.D. Van Dyk

B.C. Whitmore

A. Wofford



Abstract

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 Telescope broadband 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 ${N}_{{{\rm{H}}}_{2}}$ in low-metallicity dwarfs from a too-low CO-to-H2 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.

Citation

Kahre, L., Walterbos, R., Kim, H., Thilker, D., Calzetti, D., Lee, J., …Wofford, A. (2018). Extinction Maps and Dust-to-gas Ratios in Nearby Galaxies with LEGUS. Astrophysical Journal, 855(2), Article 133. https://doi.org/10.3847/1538-4357/aab101

Journal Article Type Article
Acceptance Date Feb 15, 2018
Online Publication Date Mar 16, 2018
Publication Date Mar 16, 2018
Deposit Date Apr 5, 2018
Publicly Available Date Apr 9, 2018
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 855
Issue 2
Article Number 133
DOI https://doi.org/10.3847/1538-4357/aab101

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Copyright Statement
© 2018. The American Astronomical Society. All rights reserved.





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