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Register a new userInterferometric CO(3-2) Observations toward the Central Region of NGC 1068
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We present CO(3-2) interferometric observations of the central region of the Seyfert 2 galaxy NGC 1068 using the Submillimeter Array, together with CO(1-0) data taken with the Owens Valley Radio Observatory Millimeter Array. Both the CO(3-2) and CO(1-0) emission lines are mainly distributed within ~5 arcsec of the nucleus and along the spiral arms, but the intensity distributions show differences; the CO(3-2) map peaks in the nucleus, while the CO(1-0) emission is mainly located along the spiral arms. The CO(3-2)/CO(1-0) ratio is about 3.1 in the nucleus, which is four times as large as the average line ratio in the spiral arms, suggesting that the molecular gas there must be affected by the radiation arising from the AGN. On the other hand, the line ratios in the spiral arms vary over a wide range from 0.24 to 2.34 with a average value around 0.75, which is similar to the line ratios of star-formation regions, indicating that the molecular gas is affected by star formation. Besides, we see a tight correlation between CO(3-2)/(1-0) ratios in the spiral arms and star formation rate surface densities derived from Spitzer 8 {mu}m dust flux densities. We also compare the CO(3-2)/(1-0) ratio and the star formation rate at different positions within the spiral arms; both are found to decrease as the radius from the nucleus increases.
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We present the first interferometric CO(J=3-2) observations (beam size of 3.9x1.6 or 160pc x 65pc) with the Submillimeter Array (SMA) toward the center of the Seyfert 2 galaxy M51. The image shows a strong concentration at the nucleus and weak emission from the spiral arm to the northwest. The integrated intensity of the central component in CO(J=3-2) is almost twice as high as that in CO(J=1-0), indicating that the molecular gas within an ~80 pc radius of the nucleus is warm (>~100 K) and dense (~10^4 cm^-3). Similar intensity ratios are seen in shocked regions in our Galaxy, suggesting that these gas properties may be related to AGN or starburst activity. The central component shows a linear velocity gradient (~1.4 km/s/pc) perpendicular to the radio continuum jet, similar to that seen in previous observations and interpreted as a circumnuclear molecular disk/torus around the Seyfert 2 nucleus. In addition, we identify a linear velocity gradient (~0.7 km/s/pc) along the jet. Judging from the energetics, the velocity gradient can be explained by supernova explosions or energy and momentum transfer from the jet to the molecular gas via interaction, which is consistent with the high intensity ratio.
We made CO ($J$ = 1--0, 2--1, and 3--2) observations toward an H{sc ii} region RCW~32 in the Vela Molecular Ridge. The CO gas distribution associated with the H{sc ii} region was revealed for the first time at a high resolution of 22 arcsec. The results revealed three distinct velocity components which show correspondence with the optical dark lanes and/or H$alpha$ distribution. Two of the components show complementary spatial distribution which suggests collisional interaction between them at a relative velocity of $sim$4 km~s$^{-1}$. Based on these results, we present a hypothesis that cloud-cloud collision determined the cloud distribution and triggered formation of the exciting star ionizing RCW~32. The collision time scale is estimated from the cloud size and the velocity separation to be $sim$2 Myrs and the collision terminated $sim$1 Myr ago, which is consistent with an age of the exciting star and the associated cluster. By combing the previous works on the H{sc ii} regions in the Vela Molecular Ridge, we argue that the majority, at least four, of the H{sc ii} regions in the Ridge were formed by triggering of cloud-cloud collision.
We present 0.8-mm band molecular images and spectra obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) toward one of the nearest galaxies with an active galactic nucleus (AGN), NGC 1068. Distributions of CO isotopic species ($^{13}$CO and C$^{18}$O) $it{J}$ = 3--2, CN $it{N}$ = 3--2 and CS $it{J}$ = 7--6 are observed toward the circumnuclear disk (CND) and a part of the starburst ring with an angular resolution of $sim$1.$^{primeprime}$3 $times$ 1.$^{primeprime}$2. The physical properties of these molecules and shock-related molecules such as HNCO, CH$_{3}$CN, SO, and CH$_{3}$OH detected in the 3-mm band were estimated using rotation diagrams under the assumption of local thermodynamic equilibrium. The rotational temperatures of the CO isotopic species and the shock-related molecules in the CND are, respectively, 14--22 K and upper limits of 20--40 K. Although the column densities of the CO isotopic species in the CND are only from one-fifth to one-third of that in the starburst ring, those of the shock-related molecules are enhanced by a factor of 3--10 in the CND. We also discuss the chemistry of each species, and compare the fractional abundances in the CND and starburst ring with those of Galactic sources such as cold cores, hot cores, and shocked molecular clouds in order to study the overall characteristics. We find that the abundances of shock-related molecules are more similar to abundances in hot cores and/or shocked clouds than to cold cores. The CND hosts relatively complex molecules, which are often associated with shocked molecular clouds or hot cores. Because a high X-ray flux can dissociate these molecules, they must also reside in regions shielded from X-rays.
We present near-infrared interferometric data on the Seyfert 2 galaxy NGC 1068, obtained with the GRAVITY instrument on the European Southern Observatory Very Large Telescope Interferometer. The extensive baseline coverage from 5 to 60 Mlambda allowed us to reconstruct a continuum image of the nucleus with an unrivaled 0.2 pc resolution in the K-band. We find a thin ring-like structure of emission with a radius r = 0.24+/-0.03 pc, inclination i = 70+/-5 deg, position angle PA = -50+/-4 deg, and h/r < 0.14, which we associate with the dust sublimation region. The observed morphology is inconsistent with the expected signatures of a geometrically and optically thick torus. Instead, the infrared emission shows a striking resemblance to the 22 GHz maser disc, which suggests they share a common region of origin. The near-infrared spectral energy distribution indicates a bolometric luminosity of (0.4-4.7) x 10^45 erg/s, behind a large A_K ~ 5.5 (A_V ~ 90) screen of extinction that also appears to contribute significantly to obscuring the broad line region.
We present the results of CO(J=3-2) on-the-fly mappings of two nearby non-barred spiral galaxies NGC 628 and NGC 7793 with the Atacama Submillimeter Telescope Experiment at an effective angular resolution of 25. We successfully obtained global distributions of CO(J=3-2) emission over the entire disks at a sub-kpc resolution for both galaxies. We examined the spatially-resolved (sub-kpc) relationship between CO(J=3-2) luminosities (LCO(3-2)) and infrared (IR) luminosities (LIR) for NGC 628, NGC 7793, and M 83, and compared it with global luminosities of JCMT Nearby Galaxy Legacy Survey sample. We found a striking linear LCO(3-2)-LIR correlation over the 4 orders of magnitude, and the correlation is consistent even with that for ultraluminous infrared galaxies and submillimeter selected galaxies. In addition, we examined the spatially-resolved relationship between CO(J=3-2) intensities (ICO(3-2)) and extinction-corrected star formation rates (SFRs) for NGC 628, NGC 7793, and M 83, and compared it with that for GMCs in M 33 and 14 nearby galaxy centers. We found a linear ICO(3-2)-SFR correlation with 1 dex scatter. We conclude that the CO(J=3-2) star formation law (i.e., linear LCO(3-2)-LIR and ICO(3-2)-SFR correlations) is universally applicable to various types and spatial scales of galaxies, from spatially-resolved nearby galaxy disks to distant IR-luminous galaxies, within 1 dex scatter.
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