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The Spitzer C2D Survey of Nearby Dense Cores: Jet and Molecular Outflow Associated With A Young Stellar Object in Core A of L1251
A long infrared jet has been discovered by the Spitzer c2d Legacy Program in core A of L1251. It is associated with a very embedded Class 0 object with an accretion luminosity of about 0.9 L(circle dot) derived by radiative transfer model fitting to the observed spectral energy distribution. Comparing the observed Infrared Array Camera colors along the infrared jet with those calculated from a model of an admixture of gas with a power-law temperature distribution indicates that the jet is possibly created by a paraboloidal bow shock propagating into the ambient medium of n(H(2)) = 10(5) cm(-3). In addition, the variation of the power-law index along the jet suggests that the portion of hot gas decreases with distance from the jet engine. The molecular outflow in this region has been mapped for the first time using CO data. From the calculated outflow momentum flux, a very strong lower limit to the average accretion luminosity is 3.6 sin i/cos(3) i L(circle dot), indicative of a decrease in the accretion rate with time.Korean government (MEST) 2009-0062865NRF R01-2007-000-20336-0NASA 1407, 1224608Astronom
Ortho-to-Para Ratio Studies of Shocked H2 Gas in the Two Supernova Remnants IC 443 and HB 21
We present near-infrared (2.5-5.0 {\mu}m) spectral studies of shocked H2 gas
in the two supernova remnants IC 443 and HB 21, which are well known for their
interactions with nearby molecular clouds. The observations were performed with
Infrared Camera (IRC) aboard the AKARI satellite. At the energy range 7000 K <=
E(v,J) <= 20000 K, the shocked H2 gas in IC 443 shows an ortho-to-para ratio
(OPR) of 2.4+0.3-0.2, which is significantly lower than the equilibrium value
3, suggesting the existence of non-equilibrium OPR. The shocked gas in HB 21
also indicates a potential non-equilibrium OPR in the range of 1.8-2.0. The
level populations are well described by the power-law thermal admixture model
with a single OPR, where the temperature integration range is 1000-4000 K. We
conclude that the obtained non-equilibrium OPR probably originates from the
reformed H2 gas of dissociative J-shocks, considering several factors such as
the shock combination requirement, the line ratios, and the possibility that H2
gas can form on grains with a non-equilibrium OPR. We also investigate C-shocks
and partially-dissociative J-shocks for the origin of the non-equilibrium OPR.
However, we find that they are incompatible with the observed ionic emission
lines for which dissociative J-shocks are required to explain. The difference
in the collision energy of H atoms on grain surfaces would make the observed
difference between the OPRs of IC 443 and HB 21, if dissociative J-shocks are
responsible for the H2 emission. Our study suggests that dissociative J-shocks
can make shocked H2 gas with a non-equilibrium OPR.Comment: aastex preprint 12pt, 32 pages, 9 figures, 7 tables, ApJ accepte
Far-Ultraviolet Cooling Features of the Antlia Supernova Remnant
We present far-ultraviolet observations of the Antlia supernova remnant
obtained with Far-ultraviolet IMaging Spectrograph (FIMS, also called SPEAR).
The strongest lines observed are C IV 1548,1551 and C III 977. The C IV
emission of this mixed-morphology supernova remnant shows a clumpy
distribution, and the line intensity is nearly constant with radius. The C III
977 line, though too weak to be mapped over the whole remnant, is shown to vary
radially. The line intensity peaks at about half the radius, and drops at the
edge of the remnant. Both the clumpy distribution of C IV and the rise in the C
IV to C III ratio towards the edge suggest that central emission is from
evaporating cloudlets rather than thermal conduction in a more uniform, dense
medium.Comment: 9 pages, 4 figures, will be published in ApJ December 1, 2007, v670n2
issue. see http://astro.snu.ac.kr/~jhshinn/ms.pd