PMO OpenIR
Dense gas in low-metallicity galaxies
Braine, J.1; Shimajiri, Y.2; Andre, P.2; Bontemps, S.1; Gao, Yu3,4; Chen, Hao5,6,7; Kramer, C.8
2017
Source PublicationASTRONOMY & ASTROPHYSICS
ISSN1432-0746
Volume597Pages:8
Corresponding AuthorBraine, J.(jonathan.braine@u-bordeaux.fr)
AbstractStars form out of the densest parts of molecular clouds. Far-IR emission can be used to estimate the star formation rate (SFR) and high dipole moment molecules, typically HCN, trace the dense gas. A strong correlation exists between HCN and far-IR emission, with the ratio being nearly constant, over a large range of physical scales. A few recent observations have found HCN to be weak with respect to the far-IR and CO in subsolar metallicity (low-Z) objects. We present observations of the Local Group galaxies M 33, IC 10, and NGC 6822 with the IRAM 30 m and NRO 45 m telescopes, greatly improving the sample of low-Z galaxies observed. HCN, HCO+, CS, C2H, and HNC have been detected. Compared to solar metallicity galaxies, the nitrogen-bearing species are weak (HCN, HNC) or not detected (CN, HNCO, N2H+) relative to far-IR or CO emission. HCO+ and C2H emission is normal with respect to CO and far-IR. While (CO)-C-13 is the usual factor 10 weaker than (CO)-C-12, (CO)-O-18 emission was not detected down to very low levels. Including earlier data, we find that the HCN/HCO+ ratio varies with metallicity (O/H) and attribute this to the sharply decreasing nitrogen abundance. The dense gas fraction, traced by the HCN/CO and HCO+/CO ratios, follows the SFR but in the low-Z objects the HCO+ is much easier to measure. Combined with larger and smaller scale measurements, the HCO+ line appears to be an excellent tracer of dense gas and varies linearly with the SFR for both low and high metallicities.
Keywordgalaxies: individual: M 33 galaxies: individual: IC 10 galaxies: individual: NGC 6822 Local Group galaxies: ISM stars: formation
DOI10.1051/0004-6361/201629781
WOS KeywordSTAR-FORMATION RATE ; SPECTRAL-LINE SURVEY ; ULTRALUMINOUS INFRARED GALAXIES ; DWARF IRREGULAR GALAXIES ; MOLECULAR GAS ; FORMATION EFFICIENCY ; STELLAR POPULATION ; MAGELLANIC CLOUDS ; STARBURST GALAXY ; PLANETARY-NEBULA
Indexed BySCI
Language英语
WOS Research AreaAstronomy & Astrophysics
WOS SubjectAstronomy & Astrophysics
WOS IDWOS:000392392900138
PublisherEDP SCIENCES S A
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Document Type期刊论文
Identifierhttp://libir.pmo.ac.cn/handle/332002/23316
Collection中国科学院紫金山天文台
Corresponding AuthorBraine, J.
Affiliation1.Univ Bordeaux, CNRS, Lab Astrophys Bordeaux, B18N,Allee Geoffroy St Hilaire, F-33615 Pessac, France
2.Univ Paris Diderot, CEA DRF CNRS, Lab AIM, IRFU,Serv Astrophys,CE Saclay, F-91191 Gif Sur Yvette, France
3.Chinese Acad Sci, Purple Mt Observ, 2 West Beijing Rd, Nanjing 210008, Jiangsu, Peoples R China
4.Chinese Acad Sci, Key Lab Radio Astron, Nanjing 210008, Jiangsu, Peoples R China
5.Nanjing Univ, Sch Astron & Space Sci, Nanjing 210093, Jiangsu, Peoples R China
6.Nanjing Univ, Key Lab Modern Astron & Astrophys, Nanjing 210093, Jiangsu, Peoples R China
7.Collaborat Innovat Ctr Modern Astron & Space Expl, Nanjing 210093, Jiangsu, Peoples R China
8.Inst Radioastron Milimetr, Nucleo Cent, Av Divina Pastora 7, Granada 18012, Spain
Recommended Citation
GB/T 7714
Braine, J.,Shimajiri, Y.,Andre, P.,et al. Dense gas in low-metallicity galaxies[J]. ASTRONOMY & ASTROPHYSICS,2017,597:8.
APA Braine, J..,Shimajiri, Y..,Andre, P..,Bontemps, S..,Gao, Yu.,...&Kramer, C..(2017).Dense gas in low-metallicity galaxies.ASTRONOMY & ASTROPHYSICS,597,8.
MLA Braine, J.,et al."Dense gas in low-metallicity galaxies".ASTRONOMY & ASTROPHYSICS 597(2017):8.
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