Disentangling the ISM phases of the dwarf galaxy NGC 4214 using [C II] SOFIA/GREAT observations
The [C ii] 158 <i>μ<i/>m fine structure line is one of the dominant cooling lines in the interstellar medium (ISM) and is an important tracer of star formation. Recent velocity-resolved studies with <i>Herschel<i/>/HIFI and SOFIA/GREAT showed that the [C ii] line can constrai...
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| Main Authors: | , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
20 February 2017
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| In: |
Astronomy and astrophysics
Year: 2017, Volume: 599 |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201629341 |
| Online Access: | Verlag, kostenfrei, Volltext: http://dx.doi.org/10.1051/0004-6361/201629341
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| Author Notes: | K. Fahrion, D. Cormier, F. Bigiel, S. Hony, N.P. Abel, P. Cigan, T. Csengeri, U.U. Graf, V. Lebouteiller, S.C. Madden, R. Wu, and L. Young |
| Summary: | The [C ii] 158 <i>μ<i/>m fine structure line is one of the dominant cooling lines in the interstellar medium (ISM) and is an important tracer of star formation. Recent velocity-resolved studies with <i>Herschel<i/>/HIFI and SOFIA/GREAT showed that the [C ii] line can constrain the properties of the ISM phases in star-forming regions. The [C ii] line as a tracer of star formation is particularly important in low-metallicity environments where CO emission is weak because of the presence of large amounts of CO-dark gas.<i>Aims. <i/>The nearby irregular dwarf galaxy NGC 4214 offers an excellent opportunity to study an actively star-forming ISM at low metallicity. We analyzed the spectrally resolved [C ii] line profiles in three distinct regions at different evolutionary stages of NGC 4214 with respect to ancillary H i and CO data in order to study the origin of the [C ii] line.<i>Methods. <i/>We used SOFIA/GREAT [C ii] 158 <i>μ<i/>m observations, H i data from THINGS, and CO(2 → 1) data from HERACLES to decompose the spectrally resolved [C ii] line profiles into components associated with neutral atomic and molecular gas. We use this decomposition to infer gas masses traced by [C ii] under different ISM conditions.<i>Results. <i/>Averaged over all regions, we associate about 46% of the [C ii] emission with the H i emission. However, we can assign only ~9% of the total [C ii] emission to the cold neutral medium (CNM). We found that about 79% of the total molecular hydrogen mass is not traced by CO emission.<i>Conclusions. <i/>On average, the fraction of CO-dark gas dominates the molecular gas mass budget. The fraction seems to depend on the evolutionary stage of the regions: it is highest in the region covering a super star cluster in NGC 4214, while it is lower in a more compact, more metal-rich region. |
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| Item Description: | Gesehen am 25.10.2017 |
| Physical Description: | Online Resource |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201629341 |