Distribution of Snow and Maximum Snow Water Equivalent Obtained by LANDSAT Data and Degree Day Method

Maximum snow water equivalence and snowcover distribution are estimated using several LANDSAT data taken in snowmelting season over a four year period. The test site is Okutadami-gawa Basin located in the central position of Tohoku-Kanto-Chubu District. The year to year normalization for snowmelt volume computation on the snow line is conducted by year to year correction of degree days using the snowcover percentage within the test basin obtained from LANDSAT data. The maximum snow water equivalent map in the test basin is generated based on the normalized snowmelt volume on the snow line extracted from four LANDSAT data taken in a different year. The snowcover distribution on an arbitrary day in snowmelting of 1982 is estimated from the maximum snow water equivalent map. The estimated snowcover is compared with the snowcover area extracted from NOAA-AVHRR data taken on the same day. The applicability of the snow estimation using LANDSAT data is discussed

A Novel Jet Model: Magnetically Collimated, Radiation-Pressure Driven Jet

Relativistic jets from compact objects are ubiquitous phenomena in the Unvierse, but their driving mechanism has been an enigmatic issue over many decades. Two basic models have been extensively discussed: magnetohydrodynamic (MHD) jets and radiation-hydrodynamic (RHD) jets. Currently, the former is more widely accepted, since magnetic field is expected to provide both the acceleration and collimation mechanisms, whereas radiation field cannot collimate outflow. Here, we propose a new type of jets, radiation-magnetohydrodynamic (RMHD) jets, based on our global RMHD simulation of luminous accretion flow onto a black hole shining above the Eddington luminosity. The RMHD jet can be accelerated up to the relativistic speed by the radiation-pressure force and is collimated by the Lorentz force of a magnetic tower, inflated magnetic structure made by toroidal magnetic field lines accumulated around the black hole, though radiation energy greatly dominates over magnetic energy. This magnetic tower is collimated by a geometrically thick accretion flow supported by radiation-pressure force. This type of jet may explain relativistic jets from Galactic microquasars, appearing at high luminosities.Comment: 5 pages, 2 figures, accepted for publication in PAS

OAO/ISLE Near-IR Spectroscopy of IRAS Galaxies

We present the results of the near-infrared (IR) spectroscopy of nine IRAS galaxies (NGC 1266, NGC 1320, NGC 2633, NGC 2903, NGC 3034, Mrk 33, NGC 7331, NGC 7625, NGC 7714) with the ISLE imager and spectrograph mounted on the Okayama Astrophysical Observatory 1.88 m telescope. [Fe II] 1.257 um and Pa beta emission lines were observed for the whole sample while H2 2.121 um and Br gamma lines were additionally obtained for two sources, whose flux ratios are used as a diagnostic tool of dominant energy sources of the galaxies. We find that the nucleus of NGC 1266 is most likely a low ionization nuclear emission-line region (LINER), while NGC 2633 and NGC 2903 possibly harbor active galactic nuclei (AGNs). No AGN or LINER signal is found for other objects. In addition, we find the spectral features which is indicative of some unusual phenomena occurring in the galaxies, such as the large [Fe II] line widths compared to the local escape velocity in NGC 1266. The present work shows the potential ability of the ISLE to shed new light on the nature of infrared galaxies, either through a statistical survey of galaxies or an exploration of spectral features found in individual objects.Comment: Accepted for publication in PAS