80 research outputs found
CO-0.30-0.07: A Peculiar Molecular Clump with an Extremely Broad Velocity Width
The high velocity dispersion compact cloud CO-0.30-0.07 is a peculiar
molecular clump discovered in the central moleculr zone of the Milky Way, which
is characterized by its extremely broad velocity emissions () despite the absence of internal energy sources. We present new
interferometric maps of the cloud in multiple molecular lines in frequency
ranges of 265--269 GHz and 276--280 GHz obtained using the Sumbmillimeter
Array, along with the single-dish images previously obtained with the ASTE 10-m
telescope. The data show that the characteristic broad velocity emissions are
predominantly confined in two parallel ridges running through the cloud center.
The central ridges are tightly anti-correlated with each other in both space
and velocity, thereby sharply dividing the entire cloud into two distinct
velocity components (+15 km s and +55 km s). This morphology is
consistent with a model in which the two velocity components collide with a
relative velocity of 40 at the interface defined by the
central ridges, although an alternative explanation with a highly inclined
expanding-ring model is yet to be fully invalidated. We have also unexpectedly
detected several compact clumps (pc in radius) likely formed by
shock compression. The clumps have several features in common with typical
star-forming clouds: high densities (), rich
abundances of hot-core-type molecular species, and relatively narrow velocity
widths apparently decoupled from the furious turbulence dominating the cloud.
The cloud CO-0.30-0.07 is possibly at an early phase of star formation activity
triggered by the shock impact.Comment: 29 pages, 10 figures, accepted for publication in Ap
Physical Conditions of Molecular Gas in the Galactic Center
We estimated physical conditions of molecular gas in the central molecular
zone (CMZ) of the Galaxy, using our CO J=3-2 data obtained with the Atacama
Submillimeter Telescope Experiment (ASTE) in conjunction with J=1-0 12CO and
13CO data previously observed with the NRO 45m telescope. The large velocity
gradient (LVG) approximation was employed. Distributions of gas density,
kinetic temperature, and CO column density are derived as functions of position
and velocity for the entire coverage of the CO J=3-2 data. We fairly determined
physical conditions for 69 % of data points in the CMZ with >= 1 sigma CO
detections. Kinetic temperature was found to be roughly uniform in the CMZ,
while gas density is higher in the 120-pc star forming ring than in the outer
dust lanes. Physical conditions of high J=3-2/J=1-0 features are also
discussed.Comment: 8 pages, 6 figures, to appear in PAS
Discovery of the Pigtail Molecular Cloud in the Galactic Center
This paper reports the discovery of a helical molecular cloud in the central
molecular zone (CMZ) of our Galaxy. This "pigtail" molecular cloud appears at
(l, b, V_LSR) ~ (-0.7deg, +0.0deg, -70 to -30 km/s), with a spatial size of ~
(20 pc)^2 and a mass of (2-6) 10^5 solar masses. This is the third helical
gaseous nebula found in the Galactic center region to date. Line intensity
ratios indicate that the pigtail molecular cloud has slightly higher
temperature and/or density than the other normal clouds in the CMZ. We also
found a high-velocity wing emission near the footpoint of this cloud. We
propose a formation model of the pigtail molecular cloud. It might be
associated with a magnetic tube that is twisted and coiled because of the
interaction between clouds in the innermost x_1 orbit and ones in the outermost
x_2 orbit.Comment: 15 pages, 6 figures, accepted for publication in Astrophysical
Journa
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