A multiwavelength study of 30 Doradus: The interstellar medium in a low-metallicity galaxy

A. Poglitsch, A. Krabbe, S. C. Madden*, T. Nikola, N. Geis, L. E.B. Johansson, G. J. Stacey, A. Sternberg

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We report maps of the 158 μm [C II] fine-structure line, the 63 μm and 146 μm [O I] fine-structure lines, the 2.2 μm H I Brγ line, the 2.1 μm H2 1-0 S(1) ro-vibrational line, and the 2.6 mm CO (1-0) rotational line toward the 30 Doradus complex in the Large Magellanic Cloud. Comparing our Brγ map with Hα and Hβ measurements, we find that visual to near-infrared extinction and reddening follow the standard dust extinction law and that the Brγ extinction is small, which allows for a reliable determination of the Lyman-continuum intensity. The Lyman continuum as derived from the Brγ emission and the far-UV derived from the far-infrared continuum match the average spectrum of the exciting stars in the 30 Doradus cluster. The observed H2 line intensity may be produced in dense clumps exposed to the stellar radiation fields. The maps of all tracers emphasize a shell-like structure of the 30 Doradus region, which is seen approximately edge-on. The warm molecular gas traced by the H2 line and the ionized gas traced by the Brγ line are intermixed, while the cold molecular gas as traced by CO (1-0) and the photodissociated gas as traced by [C II] are coextensive over tens of parsecs. This distribution can be explained only by a highly fragmented structure of the interstellar medium that allows UV radiation to penetrate deep into the molecular cloud. Clumpiness is also the key to understanding the extremely high [C II]/CO line intensity ratio. Depending on cloud geometry and physical conditions, the relative beam-filling factors of the partly atomic, partly molecular photodissociated gas as seen in the FIR tracers, and of the purely molecular gas traced by CO, can differ substantially in a clumpy, low-metallicity environment. This effect also leads to a greatly increased H2/CO conversion factor because a major part of the H2 molecular gas may be contained in the photodissociation region where CO has been destroyed.

Original languageEnglish
Pages (from-to)293-306
Number of pages14
JournalAstrophysical Journal
Issue number1
StatePublished - 20 Nov 1995


  • Dust, extinction
  • ISM: clouds
  • ISM: individual (30 Doradus)
  • ISM: structure
  • Infrared: ISM: lines and bands
  • Magellanic Clouds


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