Extinction Maps and Dust-to-gas Ratios in Nearby Galaxies with LEGUS
Authors
Ubeda, L
Andrews, JE
Ashworth, G
Bright, SN
Dobbs, C
Evans, AS
Messa, M
Nair, P
Nota, A
Ryon, JE
Whitmore, BC
Wofford, A
Publication Date
2018-03-10Journal Title
Astrophysical Journal
ISSN
0004-637X
Publisher
IOP Publishing
Volume
855
Issue
2
Type
Article
This Version
VoR
Metadata
Show full item recordCitation
Kahre, L., Walterbos, R., Kim, H., Thilker, D., Calzetti, D., Lee, J., Sabbi, E., et al. (2018). Extinction Maps and Dust-to-gas Ratios in Nearby Galaxies with LEGUS. Astrophysical Journal, 855 (2)https://doi.org/10.3847/1538-4357/aab101
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 broad band WFC3/UVIS UV and optical images from the Treasury program LEGUS (Legacy ExtraGalactic UV Survey) combined with archival HST/ACS 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 HI and CO gas maps from literature, including The HI Nearby Galaxy Survey (THINGS) and the HERA CO-Line Extragalactic Survey (HERACLES). 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 H$_2$ is not included. This implies that underestimation of $N_{H_2}$ 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 (BEAST) for NGC 7793 and find systematically lower extinctions from SED-fitting as compared to isochrone matching.
Sponsorship
SCIENCE & TECHNOLOGY FACILITIES COUNCIL (ST/N000927/1)
Embargo Lift Date
2100-01-01
Identifiers
External DOI: https://doi.org/10.3847/1538-4357/aab101
This record's URL: https://www.repository.cam.ac.uk/handle/1810/276937
Rights
Licence:
http://www.rioxx.net/licenses/all-rights-reserved