|
|
Research Highlights |
|
 Interferometric Multi CO line Observations toward M51 (Matsushita et al.) | | Seyfert galaxies have active galactic nuclei (AGNs) at the center of the galaxies, which are believed to be powered by supermassive black holes, and molecular gas and dust are believe to be the fuel for the supermassive black holes. M51 is one of the closest Seyfert galaxies (8.4 Mpc), about half the distance to the prototypical Seyfert 2 galaxy NGC 1068 (14.4 Mpc). The nucleus of M51 harbors a Seyfert 2 nucleus and exhibits radio jets. It therefore allows us to study the molecular gas around a Seyfert nucleus at the highest possible spatial resolution. 12CO (J=2-1) & (J=3-2) were observed with the SMA. All the 12CO (J=1-0), (J=2-1), & (J=3-2) maps are shown in the same scale. Purple circles indicate the field of views. The SMA images clearly show that the higher-J molecular gas emissions are strongly concentrated toward the Seyfert 2 nucleus. The 12CO(3-2)/(1-0) intensity ratio at the center is 1.9 +- 0.3, indicating that the molecular gas around the AGN is warm and dense. [Details] | | |
| Search for Tidal Interactions in AGN/QSO Host Galaxies (Lim et al.) | | Luminous Active Galactic Nuclei (AGNs) and Quasi-Stellar Objects (QSOs) are believed to be the luminous visible evidence for the vigorous accretion of gas onto central supermassive black holes. What triggers the luminous nuclear activity of these galaxies; i.e., what mechanims brings the fresh supply of fuel required to feed their central supermassive black holes? Tidal torques produced by gravitational interactions between galaxies can force large amounts of gas into the centers of galaxies, but studies reveal that the majority of active galaxies appear to be otherwise normal in optical starlight. Observations in atomic hydrogen (HI) gas, which is the most sensitive tracer of tidal interactions between galaxies, is starting to change our views of these galaxies. Our systematic HI imaging studies of Seyfert galaxies harbouring luminous AGNs and QSOs with the Very Large Array (VLA) show that the majority exhibit HI tidal features or disturbances in both morphology and kinematics indicating interactions with neighboring galaxies. The below panels show two examples, the Seyfert galaxy AKN 539 and the QSO host galaxy IRAS 17596+4221. | | |
| Molecular Gas in Radio Galaxies (Lim et al.) | | Optical imaging with the Hubble Space Telescope reveals that many elliptical galaxies that exhibit luminous radio activity also possess copius dust in the form of disks, lanes, or filaments. The origin of this dust is not well understood, but is believed to be the reservoir for fueling the central supermassive black holes of these elliptical radio galaxies. To determine the amount of molecular gas present as well as the spatio-kinematic distribution of this gas, we have conducted a survey of powerful elliptical radio galaxies in CO(1-0) and CO(2-1) with the IRAM 30-m telescope, with follow-up imaging using the IRAM PdBI. The panel below shows the detection of molecular gas with a mass of ~1 x 10^9 Msun in the powerful radio galaxy 3C 31 (NGC 383). The CO spectrum exhibits a double-horned line profile suggestive of a rotating disk. Indeed, follow-up imaging shows that the molecular gas is distributed in a rotating disk with a size of just ~2 kpc at the center of the galaxy, with the powerful radio jets apparently emerging perpendicular to this disk. | | |
| Positional Coincidence between the High-Latitude Steady Unidentified Gamma-Ray Sources and Possibly Merging Clusters of Galaxies (Kawasaki et al.) | | Matched filter "richness maps" for the seven regions centered at the steady unidentified EGRET sources at |b|>45. The EGRET source name and the bandpass of the galaxy data are shown at the top of each panel. The plus signs denote the Abell-like cluster candidates with z(estimated)<0.15 and Abell Richness Class 0 detected by a matched filter. The small open circles are Abell/ACO clusters for reference. Close cluster pairs or groups (CPGs) are shown as the green ellipses enclosing their member clusters. The VES boundary is shown with large yellow circles (solid line). The yellow dotted ellipses denote the best-fit ellipses for 95% confidence regions of the EGRET sources by Mattox et al. (2001, ApJS, 135, 155). | | |
|
|
|
|
