Astrophys. J., 864, 120-120 (2018/September-2)
ALMA observations toward the starburst dwarf galaxy NGC 5253. I. Molecular cloud properties and scaling relations.
MIURA R.E., ESPADA D., HIROTA A., NAKANISHI K., BENDO G.J. and SUGAI H.
Abstract (from CDS):
We present high-spatial-resolution (∼0.''2, or ∼3 pc) CO(2-1) observations of the nearest young starburst dwarf galaxy, NGC 5253, taken with the Atacama Large Millimeter/submillimeter Array. We have identified 118 molecular clouds with average values of 4.3 pc in radius and 2.2 km s–1 in velocity dispersion, which comprise the molecular cloud complexes observed previously with ∼100 pc resolution. We derive for the first time in this galaxy the I(CO)-N(H2) conversion factor, X=4.1–2.4+5.9×1020 cm–2(K km s–1)–1, based on the virial method. The line width and mass-to-size relations of the resolved molecular clouds present an offset on average toward higher line widths and masses with respect to quiescent regions in other nearby spiral galaxies and our Galaxy. The offset in the scaling relation reaches its maximum in regions close to the central starburst, where velocity dispersions are ∼0.5 dex higher and gas mass surface densities are as high as ΣH2=103M☉_pc–2. These central clouds are gravitationally bound despite the high internal pressure. A spatial comparison with star clusters found in the literature enables us to identify six clouds that are associated with young star clusters. Furthermore, the star formation efficiencies (SFEs) of some of these clouds exceed those found in star-cluster-forming clouds within our Galaxy. We conclude that once a super star cluster is formed, the parent molecular clouds are rapidly dispersed by the destructive stellar feedback, which results in such a high SFE in the central starburst of NGC 5253.
© 2018. The American Astronomical Society. All rights reserved.
galaxies: dwarf - galaxies: starburst - galaxies: star clusters: individual: NGC 5253
Table 3: [MEH2018] NNN (Nos 1-118).
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