A Caltech Library Service

The Panchromatic Hubble Andromeda Treasury. VIII. A Wide-area, High-resolution Map of Dust Extinction in M31

Dalcanton, Julianne J. and Fouesneau, Morgan and Hogg, David W. and Lang, Dustin and Leroy, Adam K. and Gordon, Karl D. and Sandstrom, Karin and Weisz, Daniel R. and Williams, Benjamin F. and Bell, Eric F. and Dong, Hui and Gilbert, Karoline M. and Gouliermis, Dimitrios A. and Guhathakurta, Puragra and Lauer, Tod R. and Schruba, Andreas and Seth, Anil C. and Skillman, Evan D. (2015) The Panchromatic Hubble Andromeda Treasury. VIII. A Wide-area, High-resolution Map of Dust Extinction in M31. Astrophysical Journal, 814 (1). Art. No. 3. ISSN 0004-637X.

[img] PDF - Published Version
See Usage Policy.

[img] PDF - Submitted Version
See Usage Policy.


Use this Persistent URL to link to this item:


We map the distribution of dust in M31 at 25 pc resolution using stellar photometry from the Panchromatic Hubble Andromeda Treasury survey. The map is derived with a new technique that models the near-infrared color–magnitude diagram (CMD) of red giant branch (RGB) stars. The model CMDs combine an unreddened foreground of RGB stars with a reddened background population viewed through a log-normal column density distribution of dust. Fits to the model constrain the median extinction, the width of the extinction distribution, and the fraction of reddened stars in each 25 pc cell. The resulting extinction map has a factor of ≳ 4 times better resolution than maps of dust emission, while providing a more direct measurement of the dust column. There is superb morphological agreement between the new map and maps of the extinction inferred from dust emission by Draine et al. However, the widely used Draine & Li dust models overpredict the observed extinction by a factor of ~2.5, suggesting that M31's true dust mass is lower and that dust grains are significantly more emissive than assumed in Draine et al. The observed factor of ~2.5 discrepancy is consistent with similar findings in the Milky Way by the Plank Collaboration et al., but we find a more complex dependence on parameters from the Draine & Li dust models. We also show that the the discrepancy with the Draine et al. map is lowest where the current interstellar radiation field has a harder spectrum than average. We discuss possible improvements to the CMD dust mapping technique, and explore further applications in both M31 and other galaxies.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Hogg, David W.0000-0003-2866-9403
Leroy, Adam K.0000-0002-2545-1700
Sandstrom, Karin0000-0002-4378-8534
Weisz, Daniel R.0000-0002-6442-6030
Williams, Benjamin F.0000-0002-7502-0597
Gilbert, Karoline M.0000-0003-0394-8377
Gouliermis, Dimitrios A.0000-0002-2763-0075
Guhathakurta, Puragra0000-0001-8867-4234
Additional Information:© 2015. The American Astronomical Society. Received 2014 March 7; accepted 2015 September 11; published 2015 November 10. We are happy to acknowledge Jouni Kainulainen for discussions that helped to crystallize our thinking during the writing of this paper. Bruce Draine is warmly thanked for providing his dust map in advance of publication, and for many illuminating discussions. We also are grateful to Robert Gendler ( for allowing us to use his beautiful image of M31. We also thank Léo Girardi, Brent Groves, Dan Foreman-Mackey, Hans-Walter Rix, Thomas Robitaille, and Sarah Kendrew for help during the long incubation of this paper, and for facilitating J.J.D.'s much-needed conversion to Python. We are also extremely grateful to the referee for providing a truly excellent, well-considered report. J.J.D. gratefully acknowledges the hospitality of the Max-Planck Institut für Astronomie and Caffe Vita during part of this work. This work was supported by the Space Telescope Science Institute through GO-12055. D.A.G. kindly acknowledges support from the German Research Foundation (DFG) through the individual grant GO 1659/3-1. Support for DRW is provided by NASA through Hubble Fellowship grant HST-HF-51331.01 awarded by the Space Telescope Science Institute. This research made use of Astropy, a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2013), and APLpy, an open-source plotting package for Python hosted at, as well as numpy, scipy, and matplotlib (Hunter 2007; Oliphant 2007). This research has made use of NASA's Astrophysics Data System Bibliographic Services.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Space Telescope Science InstituteGO-12055
Deutsche Forschungsgemeinschaft (DFG)GO 1659/3-1
NASA Hubble FellowshipHSTHF-51331.01
Subject Keywords:dust, extinction; galaxies: ISM; galaxies: stellar content; galaxies: structure; ISM: clouds; ISM: structure
Issue or Number:1
Record Number:CaltechAUTHORS:20160105-130329821
Persistent URL:
Official Citation:Julianne J. Dalcanton et al 2015 ApJ 814 3
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63385
Deposited By: Ruth Sustaita
Deposited On:05 Jan 2016 22:04
Last Modified:09 Mar 2020 13:19

Repository Staff Only: item control page