572 research outputs found
Central Spiral Structure of Molecular Gas in Maffei 2
Distribution and kinematics of molecular gas in the central region of the
barred spiral galaxy Maffei 2 were investigated using a data set of 12CO(1-0),
12CO(2-1), CS(2-1) lines and 103 GHz continuum. We found that the offset ridges
along the kpc-scale bar continue to the central spiral structure embedded in
the weak oval structure which is regarded as x2 orbit in the bar potential. The
spiral structure continues toward the center diverging from the oval structure.
The size of these structures is less than R ~ 100 pc. The mass concentration
within R = 35 pc is estimated to be 2 X 10^8 Mo. The high mass concentration is
consistent with theoretical predictions concerning the creation of such a
nuclear spiral structure. A comparison with the tracers of dense gas and
star-forming region suggests that the dense molecular gas traced by CS(2-1)
line is formed at the crossing points of x1 and x2 orbits and the star-forming
region appears after 2 X 10^5 yr which is comparable with the free-fall time of
the dense gas traced by the CS line (~ 10^5 cm^-3).Comment: 7 pages, 10 figures, Publication of Astronomical Society of Japan, in
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Detection of CO(J=1-0) Emission from Barred Spiral Galaxies at z~0.1
We present the results of CO (J=1-0) observations towards nine barred spiral
galaxies at z=0.08-0.25 using the 45-m telescope at Nobeyama Radio Observatory
(NRO). This survey is the first one specialized for barred spiral galaxies in
this redshift range. We detected CO emission from six out of nine galaxies,
whose CO luminosity (L_CO') ranges (1.09-10.8)\times10^9 K km s^{-1} pc^2.
These are the infrared (IR) dimmest galaxies that have ever been detected in CO
at z~0.1 to date. They follow the L_CO'-L_IR relation among local spiral
galaxies, Luminous Infrared Galaxies (LIRGs), Ultra-Luminous Infrared Galaxies
(ULIRGs) and Sub-millimeter Galaxies (SMGs). Their L_CO' and L_IR are higher
than that of local spiral galaxies which have been detected in CO so far, and
L_IR/L'_CO, which is a measure of star formation efficiency, is comparable to
or slightly higher than that of local ones. This result suggests that these
galaxies are forming stars more actively than local spirals galaxies simply
because they have more fuel.Comment: 9 pages, 5 figures, accepted for publication in PAS
A collimated jet and an infalling-rotating disk in G192.16-3.84 traced by H2O maser emission
We report H2O masers associated with the massive-star forming region
G192.16-3.84 observed with the new Japan VLBI network at three epochs spanned
for two months, which have revealed the three-dimensional kinematical structure
of the whole \h2o maser region in G192.16-3.84, containing two young stellar
objects separated by ~1200 AU. The maser spatio-kinematical structure has well
persisted since previous observations, in which the masers are expected to be
associated with a highly-collimated bipolar jet and an infalling-rotating disk
in the northern and southern clusters of H2O maser features, respectively. We
estimated a jet expansion speed of ~100 km/s and re-estimated a dynamical age
of the whole jet to be 5.6x10^4 yrs. We have investigated the spatial
distribution of Doppler velocities during the previous and present observations
and relative proper motions of H2O maser features in the southern cluster, and
a relative bulk motion between the two maser clusters. They are well explained
by a model of an infalling-rotating disk with a radius of ~1000 AU and a
central stellar mass of 5-10 M_sun, rather than by a model of a bipolar jet
perpendicular to the observed CO outflow. Based on the derived H2O maser
spatio-kinematical parameters, we discuss the formation mechanism of the
massive young stellar objects and the outflow development in G192.16-3.84.Comment: 30 pages, 3 figures, 3 tables, to be published in the Publication of
the Astronomical Society of Japan issued on 2006 October 2
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