A cautionary tale of attenuation in star-forming regions

Mallory Molina, Nikhil Ajgaonkar, Renbin Yan, Robin Ciardullo, Caryl Gronwall, Michael Eracleous, Médéric Boquien, Donald P. Schneider

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


The attenuation of light from star-forming galaxies is correlated with a multitude of physical parameters including star formation rate, metallicity and total dust content. This variation in attenuation is even more evident on kiloparsec scales, which is the relevant size for many current spectroscopic integral field unit surveys. To understand the cause of this variation, we present and analyse Swift/UVOT near-UV (NUV) images and SDSS/MaNGA emission-line maps of 29 nearby (z < 0.084) star-forming galaxies. We resolve kiloparsec-sized star-forming regions within the galaxies and compare their optical nebular attenuation (i.e. the Balmer emission line optical depth, τlB ≡ τH β-τH α) and NUV stellar continuum attenuation (via the NUV power-law index, β) to the attenuation law described by Battisti et al. We show the data agree with that model, albeit with significant scatter. We explore the dependence of the scatter of the β-τlB measurements from the star-forming regions on different physical parameters, including distance from the nucleus, star formation rate and total dust content. Finally, we compare the measured τlB and β values for the individual star-forming regions with those of the integrated galaxy light. We find a strong variation in β between the kiloparsec scale and the larger galaxy scale that is not seen in τlB. We conclude that the sightline dependence of UV attenuation and the reddening of β due to the light from older stellar populations could contribute to the scatter in the β-τlB relation.

Original languageEnglish
Pages (from-to)4751-4770
Number of pages20
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Jun 1 2020

Bibliographical note

Publisher Copyright:
© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.


  • dust, extinction
  • galaxies: General
  • galaxies: ISM

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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