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High-density Molecular Gas Properties of the Starburst Galaxy NGC 1614 Revealed with ALMA

We present the results of HCN/HCO+/HNC J=4-3 transition line observations of the nearby starburst galaxy NGC 1614, obtained with ALMA Cycle 0. We find that high density molecular gas, traced with these lines, shows a velocity structure such that the northern (southern) side of the nucleus is redshifted (blueshifted) with respect to the nuclear velocity of this galaxy. The redshifted and blueshifted emission peaks are offset by ~0.6" at the northern and southern sides of the nucleus, respectively. At these offset positions, observations at infrared >3 micron indicate the presence of active dusty starbursts, supporting the picture that high-density molecular gas is the site of active starbursts. The enclosed dynamical mass within the central ~2" in radius, derived from the dynamics of the high-density molecular gas, is ~10^9 Msun, which is similar to previous estimates. Finally, the HCN emission is weaker than HCO+ but stronger than HNC for J=4-3 for all starburst regions of NGC 1614, as seen for J=1-0 transition lines in starburst-dominated galaxies.