We present the results of our ALMA Cycle 4 high-spatial-resolution (0 04-0 07) observations, at HCN J = 3-2 and HCO+ J = 3-2 lines, of the nucleus of NGC 1068, the nearby prototypical type 2 active ...galactic nucleus (AGN). Our previous ALMA observations identified the compact emission of these lines at the putative location of the torus around a mass-accreting supermassive black hole. We now report that we have detected the rotation of this compact emission, with the eastern and western sides being redshifted and blueshifted, respectively. Unlike the previously reported CO J = 6-5 emission, both the morphological and dynamical alignments of the HCN J = 3-2 and HCO+ J = 3-2 emission are roughly along the east-west direction (i.e., the expected torus direction), suggesting that these molecular lines are better probes of a rotating dense molecular gas component in the torus. The western part of the torus exhibits larger velocity dispersion and stronger emission in the HCN J = 3-2 and HCO+ J = 3-2 lines than the eastern part, revealing a highly inhomogeneous molecular torus. The dense molecular gas in the torus and that of the host galaxy at 0 5-2 0 from the AGN along the torus direction are found to be counter-rotating, suggesting an external process happened in the past at the NGC 1068 nucleus.
We present the results of our Atacama Large Millimeter Array HCN J = 3-2 and HCO+ J = 3-2 line observations of a uniformly selected sample (>25) of nearby ultraluminous infrared galaxies (ULIRGs) at ...z < 0.15. The emission of these dense molecular gas tracers and continuum are spatially resolved in the majority of observed ULIRGs for the first time with achieved synthesized beam sizes of 0 2 or 500 pc. In most ULIRGs, the HCN-to-HCO+ J = 3-2 flux ratios in the nuclear regions within the beam size are systematically higher than those in the spatially extended regions. The elevated nuclear HCN J = 3-2 emission could be related to (a) luminous buried active galactic nuclei, (b) the high molecular gas density and temperature in ULIRG's nuclei, and/or (c) mechanical heating by spatially compact nuclear outflows. A small fraction of the observed ULIRGs display higher HCN-to-HCO+ J = 3-2 flux ratios in localized off-nuclear regions than those of the nuclei, which may be due to mechanical heating by spatially extended outflows. The observed nearby ULIRGs are generally rich in dense (>105 cm−3) molecular gas, with an estimated mass of >109 M within the nuclear (a few kpc) regions, and dense gas can dominate the total molecular mass there. We find a low detection rate (<20%) regarding the possible signature of a vibrationally excited (v2 = 1f) HCN J = 3-2 emission line in the vicinity of the bright HCO+ J = 3-2 line that may be due, in part, to the large molecular line widths of ULIRGs.
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