Abstract

We investigate the molecular gas properties, especially the dense molecular gas in NGC 1614, using the ALMA (Atacama Large Millimeter/ submillimeter Array) high resolution archival data of 12CO(1-0), 13CO(1-0), 12CO(3-2), 12CO(6-5), HCN(3-2), HCO+(3-2), HCN(4-3), and HCO+(4-3). From the high-resolution integrated intensity maps, a ring structure was detected in the central region (< 1 kpc), and the molecular gas mainly distributes in the central region while there is little gas in the nucleus. The 12CO(1-0) shows an extended structure to the south, north, and southeast, and CO (J⩾3, J is the quantum number of rotational vibration levels), HCN, and HCO+ show that the dense gas mainly concentrated in the central region. Similarly, HCN(4-3)/12CO(1-0) and HCO+(4-3)/12CO(1-0) ratio maps show that the dense molecular gas is mainly concentrated in the ring of the central region. The HCN/HCO+ ratios show that the different regions of the starburst ring might have different excitation conditions. The variations of HCN/HCO+ values in different region of central region may be due to the gas density and temperature. For HCN/HCO+(4-3) ratio map, the higher intensity values (∼0.44 ± 0.04) were obtained in the eastern and western region of the ring, compared to the northern and southern region (∼0.35 ± 0.03). For HCN/HCO+(3-2) ratio map, the higher values (∼0.38 ± 0.04) are distributed at peak location of HCN(3-2) emission, while the lower values (∼0.3 ± 0.03) are distributed at the northwestern and southeastern region of the ring. The mechanism of variations of HCN/HCO+ values in the central region of the galaxy has been discussed in the article.

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