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Masumichi Seta

Publications and source records attributed to Masumichi Seta.

20 records · Page 2Linked to original sources

Hot Ammonia in the Center of the Seyfert 2 galaxy NGC 3079

We present the results of ammonia observations toward the center of NGC 3079. The NH3(J, K) = (1, 1) and (2, 2) inversion lines were detected in absorption with the Tsukuba 32-m telescope, and the NH3(1,1) through (6,6) lines with the VLA, although the profile of NH3(3,3) was in emission in contrast to the other transitions. The background continuum source, whose flux density was ~50 mJy, could not be resolved with the VLA beam of ~< 0."09 x 0."08. All ammonia absorption lines have two distinct velocity components: one is at the systemic velocity and the other is blueshifted, and both components are aligned along the nuclear jets. For the systemic components, the relatively low temperature gas is extended more than the high temperature gas. The blueshifted NH3(3,3) emission can be regarded as ammonia masers associated with shocks by strong winds probably from newly formed massive stars or supernova explosions in dense clouds in the nuclear megamaser disk. Using para-NH3(1,1), (2,2), (4,4) and (5,5) lines with VLA, we derived the rotational temperature Trot = 120 +- 12 K and 157 +- 19 K for the systemic and blueshifted components, respectively. The total column densities of NH3(0,0)-(6,6), assuming Tex ~Trot, were (8.85+-0.70) x 10^16 cm^-2 and (4.47+-0.78) x 10^16 cm-2 for the systemic and blueshifted components, respectively. The fractional abundance of NH3 relative to molecular hydrogen H2 for the systemic and blueshifted was [NH3]/[H2]=1.3x10^-7 and 6.5 x 10^-8, respectively. We also found the F = 4-4 and F = 5-5 doublet lines of OH 2{Pi}3/2 J = 9/2 in absorption, which could be fitted by two velocity components, systemic and redshifted components. The rotational temperature of OH was estimated to be Trot,OH >~ 175 K, tracing hot gas associated with the interaction of the fast nuclear outflow with dense molecular material around the nucleus.

astro-ph.GA↗

Kinematics of Shocked Molecular Gas Adjacent to the Supernova Remnant W44

We mapped molecular gas toward the supernova remnant W44 in the HCO+ J=1-0 line with the Nobeyama Radio Observatory 45 m telescope and in the CO J=3-2 line with the Atacama Submillimeter Telescope Experiment 10 m telescope. High-velocity emission wings were detected in both lines over the area where the radio shell of W44 overlaps the molecular cloud in the plane of the sky. We found that the average velocity distributions of the wing emission can be fitted by a uniform expansion model. The best-fit expansion velocities are 12.2+-0.3 km/s and 13.2+-0.2 km/s in HCO+ and CO, respectively. The non-wing CO J=3-2 component is also fitted by the same model with an expansion velocity of 4.7+-0.1 km/s . This component might be dominated by a post shock higher-density region where the shock velocity had slowed down. The kinetic energy of shocked molecular gas is estimated to be (3.5+-1.3)x10^{49} erg. Adding this and the energy of the previously identified HI shell, we concluded that (1.2+-0.2)x10^{50} erg has been converted into gas kinetic energy from the initial baryonic energy of the W44 supernova. We also found ultra-high-velocity CO J=3-2 wing emission with a velocity width of ~100 km/s at (l, b)=(+34.73d, -0.47d). The origin of this extremely high-velocity wing is a mystery.

astro-ph.GA↗