Abstract
We present the results of ALMA observations toward the low-mass Class 0 binary system VLA 1623Aab in the Ophiuchus molecular cloud in
12
CO,
13
CO, and C
18
O(2–1) lines. Our
12
CO (
J
= ...2–1) data reveal that the VLA 1623 outflow consists of twin spatially overlapped outflows/jets. The redshifted northwestern jet exhibits three cycles of wiggle with a spatial period of 1360 ± 10 au, corresponding to a time period of 180 yr. The wiggle-like structure is also found in the position–velocity (PV) diagram, showing an amplitude in the velocity of about 0.9 km s
−1
. Both the period and velocity amplitude of the wiggle are roughly consistent with those expected from the binary parameters, i.e., the orbital period (460 ± 20 yr) and the Keplerian velocity (2.2 km s
−1
). Our
13
CO and C
18
O images show a dense gas nature in the two centimeter/millimeter sources, VLA 1623B and W, and its relation to the outflows, and strongly support the previous interpretation that both are shocked cloudlets. The driving sources of the twin molecular outflows are, therefore, likely to be the VLA 1623Aab binary. The outflow axes of the two molecular outflows are estimated to be inclined by 70° to each other across the plane of sky, implying that protostellar disks are also misaligned by
. Such nature together with a small binary separation of 34 au in one of the youngest protobinary systems seems difficult to explain by disk fragmentation in quiescent environments. Other effects such as turbulence probably play roles.
Abstract
We report the system description and results of the commissioning and science verification (CSV) of the Band 10 (787–950 GHz) heterodyne receiver for ASTE (Atacama Submillimeter Telescope ...Experiment), a 10 m submillimeter telescope at the ALMA (Atacama Large Millimeter/submillimeter Array) site in Chile. The new ASTE Band 10 receiver cartridge was refurbished from a prototype ALMA Band 10 receiver with SIS mixers employing high critical current density junctions. We installed the new receiver on ASTE and carried out its CSV. The best double-sideband (DSB) system noise temperature achieved on ASTE toward the zenith was ∼1500 K (PWV ∼ 0.5 mm). As a part of CSV activities, we performed science verification observations to demonstrate ASTE Band 10 capabilities to the community. Wide-field images were successfully obtained toward the well-studied OMC-1 region with both C i(3P2–3P1) and 12CO(J = 7–6) lines. In addition, we partially carried out observations toward a super star cluster RCW 38, C i(3P1–3P0), images of which were already obtained by ASTE. We demonstrated the capability of ASTE Band 10 observations toward bright and extended objects like giant molecular clouds.
Abstract
We present observations of the 3P1–3P0 fine-structure line of atomic carbon using the ASTE 10m sub-mm telescope towards RCW 38, the youngest super star cluster in the Milky Way. The detected ...C i emission is compared with the CO J = 1–0 image cube presented in Fukui et al. (2016, ApJ, 820, 26) which has an angular resolution of 40″ (∼0.33 pc). The overall distribution of the C i emission in this cluster is similar to that of the 13CO emission. The optical depth of the C i emission was found to be τ = 0.1–0.6, suggesting mostly optically thin emission. An empirical conversion factor from the C i integrated intensity to the H2 column density was estimated as XC i$= 6.3 \times 10 ^{20}\:$cm−2 K−1 km−1 s (for visual extinction: AV ≤ 10 mag) and 1.4 × 1021 cm−2 K−1 km−1 s (for AV of 10–100 mag). The column density ratio of the C i to CO (NC i$/N_{\rm CO}$) was derived as ∼0.1 for AV of 10–100 mag, which is consistent with that of the Orion cloud presented in Ikeda et al. (2002, ApJ, 571, 560). However, our results cover an AV regime of up to 100 mag, which is wider than the coverage found in Orion, which reaches up to ∼60 mag. Such a high C i$/$CO ratio in a high-AV region is difficult to explain via the plane-parallel photodissociation region model, which predicts that this ratio is close to 0 due to the heavy shielding of the ultraviolet (UV) radiation. Our results suggest that the molecular gas in this cluster is highly clumpy, allowing deep penetration of UV radiation even at averaged AV values of 100 mag. Recent theoretical works have presented models consistent with such clumped gas distribution with a sub-pc clump size (e.g., Tachihara et al. 2018, arXiv:1811.02224).
We have developed a 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
$\times$
5 array receiver, BEARS, on the 45-m. During OTF observations, the antenna is continuously driven to cover the mapped region rapidly, resulting in a high observing efficiency and accuracy. Pointing of the antenna and readouts from the spectrometer are recorded as fast as 0.1s. In this paper we report on improvements made to the software and instruments, requirements and optimization of observing parameters, the data-reduction process, and verification of the system. It is confirmed that, using optimal parameters, the OTF is about twice as efficient as the conventional position-switch observing method.
We have developed an FX-architecture digital spectro-correlator for the Atacama Compact Array of the Atacama Large Millimeter/submillimeter Array. The correlator is able to simultaneously process ...four pairs of dual polarization signals with a bandwidth of 2 GHz, which are received by up to sixteen antennas. It can calculate auto- and cross-correlation spectra, including cross-polarization in all combinations of all the antennas, and output correlation spectra with flexible spectral configuration, such as multiple frequency ranges and multiple frequency resolutions. Its spectral dynamic range is estimated to be higher than 10
$^{4}$
relative to
$T_{\rm sys}$
from processing results of thermal noise for eight hours with a typical correlator configuration. The sensitivity loss is also confirmed to be 0.9% with the same configuration. In this paper, we report on the detailed design of the correlator and the verification results of the developed hardware.
We have made mapping observations of L 1551 IRS 5, L 1551 NE, L 723, and L 43 and single-point observations of IRAS 16293
$-$
2422 in the submillimeter CS (
$J$
$=$
7–6) and HCN (
$J$
$=$
4–3) lines ...with Atacama Submillimeter Telescope Experiment (ASTE). Using the present data and our previous ASTE observations of L 483 and B 335 together, we found a definite correlation between source bolometric luminosities and total integrated intensities of the submillimeter lines (
$I_{\rm CS}$
$\propto$
$L_{\rm bol}^{0.92}$
). The combined ASTE
$+$
Submillimeter Array CS (7–6) image of L 1551 IRS 5 exhibits an extended (
$\sim$
2000 AU) component tracing the associated reflection nebula at west and southwest, as well as a compact (
$\lesssim$
500 AU) component centered on the protostellar position. The peaks of the CS and HCN emissions in L 1551 NE are not located at the protostellar position but offset (
$\sim$
1400 AU) toward the associated reflection nebula at west. By statistical analyses, we confirmed the velocity gradients of the CS (7–6) emission that are opposite to those of the millimeter lines along the outflow direction, which we reported in our early paper. The magnitudes of the submillimeter velocity gradients are estimated to be (9.7
$\ \pm\ $
1.7)
$\times$
10
$^{-3}\ $
km s
$^{-1}\ $
arcsec
$^{-1}\ $
in L 1551 IRS 5 and (7.6
$\ \pm\ $
2.4)
$\times$
10
$^{-3}\ $
km s
$^{-1}\ $
arcsec
$^{-1}\ $
in L 483. We suggest that the “skewed” submillimeter molecular emissions toward the associated reflection nebulae at a few thousand AU scale trace the warm (
$\gtrsim$
40 K) walls of the envelope cavities, excavated by the associated outflows and directly irradiated by the central protostars. The opposite velocity gradients along the outflow direction likely reflect the dispersing gas motion at the wall of the cavity in envelopes perpendicular to the outflow.
The Atacama Compact Array (ACA) Iguchi, Satoru; Morita, Koh-Ichiro; Sugimoto, Masahiro ...
Publications of the Astronomical Society of Japan,
02/2009, Letnik:
61, Številka:
1
Journal Article
Recenzirano
Odprti dostop
For realizing high fidelity of imaging with mosaicing observations, the Atacama Large Millimeter/submillimeter Array (ALMA) consists of a homogeneous array of 12 m antennas (12 m Array) and the ...Atacama Compact Array (ACA) in order to cover all spatial frequency Fourier components of the brightness distribution of observed sources. The array is located at an altitude site of about 5000 m with an operating wavelength range of 0.3 to 3 mm. ACA is an array composed of four 12 m dishes TP (Total Power) Array and twelve 7 m dishes (7 m Array). The 7 m Array has a very compact configuration to take short-baseline data corresponding to the low spatial frequency Fourier components. The 7 m Array has two configurations extended over 30-50 m to avoid shadowing at low elevation. The scientific importances and operation concepts of ACA, and the system design of ACA and its performance are presented in this paper.
The Millimeter Sky Transparency Imager (MiSTI) Tamura, Yoichi; Kawabe, Ryohei; Kohno, Kotaro ...
Publications of the Astronomical Society of Japan,
04/2011, Letnik:
63, Številka:
2
Journal Article
Recenzirano
Odprti dostop
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 range. MiSTI observes the water vapor distribution at a spatial resolution of 0
$^\circ\!\!\!.$
5, and it is sensitive enough to detect an excess path length of
$\lesssim\ $
0.05 mm for an integration time of 1 s. By comparing the MiSTI measurements with those by a 220 GHz tipper, we validated 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 us to know the (sub)millimeter sky conditions at Atacama.
With the ASTE telescope, we have observed three low-mass protostellar envelopes around L483, B335, and L723 in the submillimeter CS (
$J$
= 7
$-$
6) and HCN (
$J$
= 4
$-$
3) lines. We detected both ...the CS and HCN lines toward all targets, and the typical CS intensity (
$\sim$
1.0 K in
$T_{\rm B}$
) was twice higher than that of the HCN line. Mapping observations of L483 in these lines have shown that the submillimeter emissions are resolved, exhibit a western extension from the central protostar, and that the deconvolved size is
$\sim$
5500 AU
$\times$
3700 AU (PA = 78
$^{\circ}$
) in the HCN emission. The extent of the submillimeter emission in L483 implies the presence of higher temperature (
$\gtrsim$
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 bipolar cavity into account. The position–velocity diagrams of these submillimeter lines along the axis of the associated molecular outflow exhibit that the sense of the submillimeter velocity gradient is opposite to that of the millimeter observation or the associated molecular outflow, both in L483 and in B335. We suggest that expanding gas motions at the surface of the flattened envelope, which is irradiated by the central protostar directly, are the origin of the observed submillimeter velocity structure.
PDF
