A Caltech Library Service

He II Emission from Wolf-Rayet Stars as a Tool for Measuring Dust Reddening

Leitherer, Claus and Lee, Janice C. and Faisst, Andreas (2019) He II Emission from Wolf-Rayet Stars as a Tool for Measuring Dust Reddening. Astronomical Journal, 158 (5). Art. No. 192. ISSN 1538-3881. doi:10.3847/1538-3881/ab44c0.

[img] PDF - Published Version
See Usage Policy.

[img] PDF - Submitted Version
See Usage Policy.


Use this Persistent URL to link to this item:


We calibrated a technique to measure dust attenuation in star-forming galaxies. The technique utilizes the stellar-wind lines in Wolf–Rayet stars, which are widely observed in galaxy spectra. The He ii 1640 and 4686 features are recombination lines whose ratio is largely determined by atomic physics. Therefore they can serve as a stellar dust probe in the same way as the Balmer lines are used as a nebular probe. We measured the strength of the He ii 1640 line in 97 Wolf–Rayet stars in the Galaxy and the Large Magellanic Cloud. The reddening corrected fluxes follow a tight correlation with a fixed ratio of 7.76 for the He ii 1640 to 4686 line ratio. Dust attenuation decreases this ratio. We provide a relation between the stellar E(B−V) and the observed line ratio for several attenuation laws. Combining this technique with the use of the nebular Balmer decrement allows the determination of the stellar and nebular dust attenuation in galaxies and can probe its effects at different stellar age and mass regimes, independently of the initial mass function and the star formation history. We derived the dust reddening from the He ii line fluxes and compared it to the reddening from the Balmer decrement and from the slope of the ultraviolet continuum in two star-forming galaxies. The three methods result in dust attenuations which agree to within the errors. Future application of this technique permits studies of the stellar dust attenuation compared to the nebular attenuation in a representative galaxy sample.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Leitherer, Claus0000-0003-2685-4488
Lee, Janice C.0000-0002-2278-9407
Faisst, Andreas0000-0002-9382-9832
Additional Information:© 2019 The American Astronomical Society. Received 2019 June 17; revised 2019 August 21; accepted 2019 September 13; published 2019 October 21. Useful email correspondence with Paul Crowther and Andreas Sander are gratefully acknowledged. We are grateful to Daniela Calzetti and Karl Gordon for their comments on the reddening law section of the paper. Support for this work has been provided by NASA through grant No. AR-15036 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. This research has made extensive use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:Wolf–Rayet stars; Interstellar dust extinction; Interstellar medium; Stellar populations; Young star clusters; Starburst galaxies
Issue or Number:5
Classification Code:Unified Astronomy Thesaurus concepts: Wolf–Rayet stars (1806); Interstellar dust extinction (837); Interstellar medium (847); Stellar populations (1622); Young star clusters (1833); Starburst galaxies (1570)
Record Number:CaltechAUTHORS:20191002-112346900
Persistent URL:
Official Citation:Claus Leitherer et al 2019 AJ 158 192
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99018
Deposited By: Tony Diaz
Deposited On:02 Oct 2019 19:29
Last Modified:16 Nov 2021 17:43

Repository Staff Only: item control page