19 research outputs found
ASTE Observations of Warm Gas in Low-mass Protostellar Envelopes: Different Kinematics between Submillimeter and Millimeter Lines
With the ASTE telescope, we have made observations of three low-mass
protostellar envelopes around L483, B335, and L723 in the submillimeter CS
(=7--6) and HCN (=4--3) lines. We detected both the CS and HCN lines
toward all the targets, and the typical CS intensity ( 1.0 K in T)
is twice higher than that of the HCN line. Mapping observations of L483 in
these lines have shown that the submillimeter emissions in the low-mass
protostellar envelope are resolved, exhibit a western extension from the
central protostar, and that the deconvolved size is 5500 AU
3700 AU (P.A. = 78) in the HCN emission. The extent of the
submillimeter emissions in L483 implies the presence of higher-temperature
( 40 K) gas at 4000 AU away from the central protostar, which suggests
that we need to take 2-dimensional radiative transfer models with a flattened
disklike envelope and bipolar cavity into account to explain the temperature
structure inside the low-mass protostellar envelope. The position-velocity
diagrams of these submillimeter lines in L483 and B335 exhibit different
velocity gradients from those found in the previous millimeter observations. In
particular, along the axis of the associated molecular outflow the sense of the
velocity gradient traced by the submillimeter lines is opposite to that of the
millimeter observations or the associated molecular outflow, both in L483 and
B335. We suggest that expanding gas motions at the surface of the flattened
disklike envelope around the protostar, which is irradiated from the central
star directly, are the origin of the observed submillimeter velocity structure.Comment: 20 pages, 11 figure
The Millimeter Sky Transparency Imager (MiSTI)
The Millimeter Sky Transparency Imager (MiSTI) is a small millimeter-wave
scanning telescope with a 25-cm diameter dish operating at 183 GHz. MiSTI is
installed at Atacama, Chile, and it measures emission from atmospheric water
vapor and its fluctuations to estimate atmospheric absorption in the millimeter
to submillimeter. MiSTI observes the water vapor distribution at a spatial
resolution of 0.5 deg, and it is sensitive enough to detect an excess path
length of <~ 0.05 mm for an integration time of 1 s. By comparing the MiSTI
measurements with those by a 220 GHz tipper, we validate that the 183 GHz
measurements of MiSTI are correct, down to the level of any residual systematic
errors in the 220 GHz measurements. Since 2008, MiSTI has provided real-time
(every 1 hr) monitoring of the all-sky opacity distribution and atmospheric
transmission curves in the (sub)millimeter through the internet, allowing to
know the (sub)millimeter sky conditions at Atacama.Comment: 12 pages, 1 table, 10 figures, accepted for publication in PAS
On-The-Fly Observing System of the Nobeyama 45-m and ASTE 10-m Telescopes
We have developed spectral line On-The-Fly (OTF) observing mode for the
Nobeyama Radio Observatory 45-m and the Atacama Submillimeter Telescope
Experiment 10-m telescopes. Sets of digital autocorrelation spectrometers are
available for OTF with heterodyne receivers mounted on the telescopes,
including the focal-plane 5 x 5 array receiver, BEARS, on the 45-m. During OTF
observations, the antenna is continuously driven to cover the mapped region
rapidly, resulting in high observing efficiency and accuracy. Pointing of the
antenna and readouts from the spectrometer are recorded as fast as 0.1 second.
In this paper we report improvements made on software and instruments,
requirements and optimization of observing parameters, data reduction process,
and verification of the system. It is confirmed that, using optimal parameters,
the OTF is about twice as efficient as conventional position-switch observing
method.Comment: 11 pages, 13 figures, accepted for publication in PAS
The Molecular Outflows in the rho Ophiuchi Main Cloud: Implications For Turbulence Generation
We present the results of CO (J=3-2) and CO (J=1-0) mapping observations
toward the active cluster forming clump, L1688, in the rho Ophiuchi molecular
cloud. From the CO (J=3-2) and CO (J=1-0) data cubes, we identify five
outflows, whose driving sources are VLA 1623, EL 32, LFAM 26, EL 29, and IRS
44. Among the identified outflows, the most luminous outflow is the one from
the prototypical Class 0 source, VLA 1623. We also discover that the EL 32
outflow located in the Oph B2 region has very extended blueshifted and
redshifted lobes with wide opening angles. This outflow is most massive and
have the largest momentum among the identified outflows in the CO (J=1-0) map.
We estimate the total energy injection rate due to the molecular outflows
identified by the present and previous studies to be about 0.2 L_solar, larger
than or at least comparable to the turbulence dissipation rate [~(0.03 - 0.1)
L_solar]. Therefore, we conclude that the protostellar outflows are likely to
play a significant role in replenishing the supersonic turbulence in this
clump.Comment: 37 pages, 9 figures, accepted for publication in The Astrophysical
Journa