Impulsive Gas Fueling to Galactic Center in a Barred Galaxy Due to Falls of Gas Clouds

We have studied the evolution of the central hundred pc region of barred galaxies by performing numerical simulations realizing multi-phase nature of gas. Our simulations have shown that a stellar bar produces an oval gas ring namely the $x$-2 ring within $1~{\rm kpc}$ as the bar grows. The ring is self-gravitationally unstable enough to trigger formations of gas clouds. Although the gas clouds initially rotate in the $x$-2 ring, cloud-cloud collisions and/or energy injections into the gas ring by Type II supernovae deviate some of the clouds from the ring orbit. After the deviation, the deviated clouds repeat collisions with the other clouds, which rotate in the $x$-2 ring, during several rotations. These processes effectively reduce the angular momentum of the deviated gas cloud. As a result, the gas cloud finally falls into the galactic center, and episodic gas supply to the galactic center takes place.Comment: 10 pages, 9 figures, accepted for publication in PAS

Mass Supply to Galactic Center due to Nested Bars in the Galaxy

We investigate rapid mass supply process by nested bars in the Galaxy by numerical simulation. We simulate gas flow in the whole galaxy disk with nested bars, which are the outer bar and the inner bar, especially with highly spatial resolution in the galactic central region. We assume two cases of inner bar size which are a smaller one and a larger one than the radius of the 200 pc gas ring which is corresponds to the Central Molecular Zone. From our numerical results, in the large size bar cases, the inner bars with large elongation induce sufficient mass inflow and destroy the 200 pc gas ring. On the other hand, in the small size bar cases, the inner bars with large elongation induce large mass inflow and do not destroy the 200 pc gas ring. This mass inflow is caused by straight shocks excited by the inner bar. In this case, nuclear gas disks of ~ 15 pc radius are formed. The nuclear gas disks are self-gravitationally unstable and we expect formation of compact star clusters under strong tidal force in the nuclear gas disks. We discuss evolution of the nuclear gas disk.Comment: 36 pages, 11 figures. Submitted to Ap

Adenocarcinoma of Ascending Colon Associated with Sarcoid Reaction in Regional Lymph Nodes

Lymph node swelling in the setting of malignancy generally suggests metastasis of the primary tumor. A granulomatous reaction, i.e. sarcoid reaction, occurring within the lymph nodes draining carcinomas is a well-known but uncommon occurrence. The phenomenon is especially rarely seen in colon carcinoma. We herein report a rare case of a 56-year-old Japanese male with adenocarcinoma of the ascending colon associated with sarcoid reaction in the regional lymph nodes. A typical ileocecal resection and lymph node dissection were performed. Histopathological examination revealed moderately differentiated adenocarcinoma of the ascending colon, and the dissected lymph nodes included epithelioid granulomas with multinucleated giant cells. These findings suggest the existence of a sarcoid reaction associated with colon carcinoma; there was no metastasis in the dissected lymph nodes. The significance of this rare condition is discussed

Effects of a Supermassive Black Hole Binary on a Nuclear Gas Disk

We study influence of a galactic central supermassive black hole (SMBH) binary on gas dynamics and star formation activity in a nuclear gas disk by making three-dimensional Tree+SPH simulations. Due to orbital motions of SMBHs, there are various resonances between gas motion and the SMBH binary motion. We have shown that these resonances create some characteristic structures of gas in the nuclear gas disk, for examples, gas elongated or filament structures, formation of gaseous spiral arms, and small gas disks around SMBHs. In these gaseous dense regions, active star formations are induced. As the result, many star burst regions are formed in the nuclear region.Comment: 19 pages, 11 figures, accepted for publication in Ap

Tidal disruption of dark matter halos around proto-globular clusters

Tidal disruption of dark matter halos around proto-globular clusters in a halo of a small galaxy is studied in the context of the hierarchical clustering scenario by using semi-cosmological N-body/SPH simulations assuming the standard cold dark matter model ($\Omega_0 = 1$). Our analysis on formation and evolution of the galaxy and its substructures archives until $z = 2.0$. In such a high-redshift universe, the Einstein-de Sitter universe is still a good approximation for a recently favored $\Lambda$-dominated universe, and then our results does not depend on the choice of cosmology. In order to resolve small gravitationally-bound clumps around galaxies and consider radiative cooling below $T = 10^4 K$, we adopt a fine mass resolution (m_{\rm SPH} = 1.12 \times 10^3 \Msun). Because of the cooling, each clump immediately forms a `core-halo' structure which consists of a baryonic core and a dark matter halo. The tidal force from the host galaxy mainly strips the dark matter halo from clumps and, as a result, theses clumps get dominated by baryons. Once a clump is captured by the host halo, its mass drastically decreases each pericenter passage. At $z = 2$, more than half of the clumps become baryon dominated systems (baryon mass/total mass $> 0.5$). Our results support the tidal evolution scenario of the formation of globular clusters and baryon dominated dwarf galaxies in the context of the cold dark matter universe.Comment: 9page, 13 figures. Accepted for publication in ApJ. A high-resolution PDF of the paper can be obtained from http://th.nao.ac.jp/~takayuki/ApJ05

Rosai-Dorfman disease of the colon presented as small solitary polypoid lesion

Rosai-Dorfman disease (RDD) was formerly known as “sinus histiocytosis with massive lymphadenopathy”, and cases involving the gastrointestinal tract are rare. We present a case of pure extranodal RDD, resected as a polypoid lesion in colonoscopic study. The patient was a 62-year old woman with a history of sigmoidectomy for unexplained peritonitis. Microscopic study of the polypoid lesion showed the submucosal mass with histological and immunological features of RDD. The whole body computed tomography revealed neither lymphadenopathy nor tumor-like mass