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Paper: Multiline Observations of Molecular Gas in the Central Region of the ``Low Star Formation Efficiency'' Starburst Galaxy NGC 4527
Volume: 249, The Central Kiloparsec of Starbursts and AGN: the La Palma Connection
Page: 691
Authors: Shibatsuka, Toshihito; Kohno, Kotaro; Matsushita, Satoki; Kawabe, Ryohei
Abstract: In order to understand the relationship between the physical properties of molecular gas and star formation we have performed high resolution CO (2 --> 1), CO (1 --> 0), 13CO (1 --> 0), C18O (1 --> 0), HCN (1 --> 0), HCO+ (1 --> 0), CS (2 --> 1), and 3 mm continuum observations of the ``low star formation efficiency'' starburst galaxy NGC 4527 with the Nobeyama Millimeter Array. The CO (1 --> 0) map clearly shows the characteristic molecular gas distribution for barred galaxies: two offset ridges located symmetrically toward the nucleus. On the other hand, other molecule emissions, which trace dense molecular matter, are found to be spatially associated with the central star-forming regions traced by the radio-continuum and mid-infrared emission. The integrated-intensity ratios, CO (2 --> 1)/CO (1 --> 0) and HCN (1 --> 0)/CO (1 --> 0), at the center (r < 3 arcsec) are found to be smaller than those in prototypical starburst galaxies such as NGC 253, and we suggest that the fraction of dense molecular gas to the total molecular mass is small in the central few kpc of NGC 4527. This fact may be responsible for the low star formation efficiency in the center of NGC 4527.
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