Large Molecular-Cloud Complexes

1988 ◽  
pp. 269-280 ◽  
Author(s):  
L. Blitz
Keyword(s):  
Molecular Cloud

THE TRANSITION FROM DIFFUSE ATOMIC GAS TO MOLECULAR CLOUD IN TAURUS

2019 ◽  
Author(s):  
Steven Federman ◽  
David Lambert ◽  
Gregory Mace ◽  
Nicolas Flagey ◽  
Paul Goldsmith ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Atomic Gas

SiO Maser Sources toward the Sagittarius B2 Molecular Cloud

1997 ◽  
Vol 478 (1) ◽  
pp. 206-210 ◽  
Author(s):  
Shigetomo Shiki ◽  
Masatoshi Ohishi ◽  
Shuji Deguchi
Keyword(s):  
Molecular Cloud ◽  
Maser Sources

The Magnetic Field of the NGC 2024 Molecular Cloud

1999 ◽  
Vol 515 (1) ◽  
pp. 275-285 ◽  
Author(s):  
R. M. Crutcher ◽  
D. A. Roberts ◽  
T. H. Troland ◽  
W. M. Goss
Keyword(s):  
Magnetic Field ◽  
Molecular Cloud ◽  
The Magnetic Field

The Perseus B5 Molecular Cloud Halo: Measurements of Pressure, Temperature, and Composition

1999 ◽  
Vol 510 (1) ◽  
pp. 291-304 ◽  
Author(s):  
Peter Wannier ◽  
B‐G Andersson ◽  
Bryan E. Penprase ◽  
S. R. Federman
Keyword(s):  
Molecular Cloud

350 Micron Continuum Imaging of the Orion A Molecular Cloud with the Submillimeter High Angular Resolution Camera

1998 ◽  
Vol 509 (1) ◽  
pp. 299-308 ◽  
Author(s):  
D. C. Lis ◽  
E. Serabyn ◽  
Jocelyn Keene ◽  
C. D. Dowell ◽  
D. J. Benford ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Angular Resolution ◽  
High Angular Resolution

scholarly journals Resolved spectral variations of the centimetre-wavelength continuum from the ρ Oph W photo-dissociation-region

2021 ◽  
Author(s):  
Simon Casassus ◽  
Matías Vidal ◽  
Carla Arce-Tord ◽  
Clive Dickinson ◽  
Glenn J White ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Dust Emission ◽  
Image Synthesis ◽  
Microwave Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Parametric Image ◽  
Physical Conditions ◽  
Morphological Differences ◽  
Dust Grain

Abstract Cm-wavelength radio continuum emission in excess of free-free, synchrotron and Rayleigh-Jeans dust emission (excess microwave emission, EME), and often called ‘anomalous microwave emission’, is bright in molecular cloud regions exposed to UV radiation, i.e. in photo-dissociation regions (PDRs). The EME correlates with IR dust emission on degree angular scales. Resolved observations of well-studied PDRs are needed to compare the spectral variations of the cm-continuum with tracers of physical conditions and of the dust grain population. The EME is particularly bright in the regions of the ρ Ophiuchi molecular cloud (ρ Oph) that surround the earliest type star in the complex, HD 147889, where the peak signal stems from the filament known as the ρ Oph-W PDR. Here we report on ATCA observations of ρ Oph-W that resolve the width of the filament. We recover extended emission using a variant of non-parametric image synthesis performed in the sky plane. The multi-frequency 17 GHz to 39 GHz mosaics reveal spectral variations in the cm-wavelength continuum. At ∼30 arcsec resolutions, the 17-20 GHz intensities follow tightly the mid-IR, Icm∝I(8 μm), despite the breakdown of this correlation on larger scales. However, while the 33-39 GHz filament is parallel to IRAC 8 μm, it is offset by 15–20 arcsec towards the UV source. Such morphological differences in frequency reflect spectral variations, which we quantify spectroscopically as a sharp and steepening high-frequency cutoff, interpreted in terms of the spinning dust emission mechanism as a minimum grain size acutoff ∼ 6 ± 1 Å that increases deeper into the PDR.

scholarly journals The effect of stellar multiplicity on protoplanetary discs: a near-infrared survey of the Lupus star-forming region

2020 ◽  
Vol 501 (2) ◽  
pp. 2305-2315
Author(s):  
Alice Zurlo ◽  
Lucas A Cieza ◽  
Megan Ansdell ◽  
Valentin Christiaens ◽  
Sebastián Pérez ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Molecular Cloud ◽  
Near Infrared ◽  
Main Sequence Stars ◽  
Multiple Systems ◽  
Star Forming ◽  
Very Large Telescope ◽  
Pms Stars ◽  
First Time ◽  
Infrared Survey

ABSTRACT We present results from a near-infrared (NIR) adaptive optics (AO) survey of pre-main-sequence stars in the Lupus molecular cloud with NACO at the Very Large Telescope (VLT) to identify (sub)stellar companions down to ∼20-au separation and investigate the effects of multiplicity on circumstellar disc properties. We observe for the first time in the NIR with AO a total of 47 targets and complement our observations with archival data for another 58 objects previously observed with the same instrument. All 105 targets have millimetre Atacama Large Millimetre/sub-millimetre Array (ALMA) data available, which provide constraints on disc masses and sizes. We identify a total of 13 multiple systems, including 11 doubles and 2 triples. In agreement with previous studies, we find that the most massive (Mdust > 50 M⊕) and largest (Rdust > 70 au) discs are only seen around stars lacking visual companions (with separations of 20–4800 au) and that primaries tend to host more massive discs than secondaries. However, as recently shown in a very similar study of >200 PMS stars in the Ophiuchus molecular cloud, the distributions of disc masses and sizes are similar for single and multiple systems for Mdust < 50 M⊕ and radii Rdust < 70 au. Such discs correspond to ∼80–90 per cent of the sample. This result can be seen in the combined sample of Lupus and Ophiuchus objects, which now includes more than 300 targets with ALMA imaging and NIR AO data, and implies that stellar companions with separations >20 au mostly affect discs in the upper 10${{\ \rm per\ cent}}$ of the disc mass and size distributions.

scholarly journals Carbon-chain molecules in molecular outflows and Lupus I region – new producing region and new forming mechanism

2019 ◽  
Vol 488 (1) ◽  
pp. 495-511
Author(s):  
Yuefang Wu ◽  
Xunchuan Liu ◽  
Xi Chen ◽  
Lianghao Lin ◽  
Jinghua Yuan ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Molecular Cloud ◽  
Carbon Chain ◽  
Species Range ◽  
Chain Molecules ◽  
Forming Mechanism ◽  
Molecular Outflows ◽  
Chemical Models ◽  
Cloud Complex

Abstract Using the new equipment of the Shanghai Tian Ma Radio Telescope, we have searched for carbon-chain molecules (CCMs) towards five outflow sources and six Lupus I starless dust cores, including one region known to be characterized by warm carbon-chain chemistry (WCCC), Lupus I-1 (IRAS 15398-3359), and one TMC-1 like cloud, Lupus I-6 (Lupus-1A). Lines of HC3N J = 2 − 1, HC5N J = 6 − 5, HC7N J = 14 − 13, 15 − 14, 16 − 15, and C3S J = 3 − 2 were detected in all the targets except in the outflow source L1660 and the starless dust core Lupus I-3/4. The column densities of nitrogen-bearing species range from 1012 to 1014 cm−2 and those of C3S are about 1012 cm−2. Two outflow sources, I20582+7724 and L1221, could be identified as new carbon-chain-producing regions. Four of the Lupus I dust cores are newly identified as early quiescent and dark carbon-chain-producing regions similar to Lup I-6, which together with the WCCC source, Lup I-1, indicate that carbon-chain-producing regions are popular in Lupus I which can be regard as a Taurus-like molecular cloud complex in our Galaxy. The column densities of C3S are larger than those of HC7N in the three outflow sources I20582, L1221, and L1251A. Shocked carbon-chain chemistry is proposed to explain the abnormal high abundances of C3S compared with those of nitrogen-bearing CCMs. Gas-grain chemical models support the idea that shocks can fuel the environment of those sources with enough S+ thus driving the generation of S-bearing CCMs.

scholarly journals 13CO(J = 1-0) Observations of the Orion Molecular Cloud

1987 ◽  
Vol 115 ◽  
pp. 149-150
Author(s):  
K. Sugitani ◽  
Y. Fukui
Keyword(s):  
Millimeter Wave ◽  
High Velocity ◽  
Molecular Cloud ◽  
High Velocity Resolution ◽  
H Ii Region ◽  
Co Emission

We present new 13CO(J = 1-0) measurements of the Orion molecular cloud. The data were taken with the 4-m millimeter-wave telescope of Nagoya University with a beamwidth of 2.7′. The high velocity resolution of 0.1 km s−1 employed has revealed significant details of the 13CO emission toward the H II region.

scholarly journals Aperture synthesis CS and 98 GHz continuum observations of protostellar IRAS sources in Taurus

1991 ◽  
Vol 147 ◽  
pp. 353-356
Author(s):  
N. Ohashi ◽  
R. Kawabe ◽  
M. Hayashi ◽  
M. Ishiguro
Keyword(s):  
Molecular Cloud ◽  
Total Mass ◽  
T Tauri Stars ◽  
Continuum Emission ◽  
Beam Size ◽  
Dust Grains ◽  
Dynamical Mass ◽  
T Tauri ◽  
Cloud Cores ◽  
The Continuum

The CS (J = 2 — 1) line and 98 GHz continuum emission have been observed for 11 protostellar IRAS sources in the Taurus molecular cloud with resolutions of 2.6″−8.8″ (360 AU—1200 AU) using the Nobeyama Millimeter Array (NMA). The CS emission is detected only toward embedded sources, while the continuum emission from dust grains is detected only toward visible T Tauri stars except for one embedded source, L1551-IRS5. This suggests that the dust grains around the embedded sources do not centrally concentrate enough to be detected with our sensitivity (∼4 m Jy r.m.s), while dust grains in disks around the T Tauri stars have enough total mass to be detected with the NMA. The molecular cloud cores around the embedded sources are moderately extended and dense enough to be detected in CS, while gas disks around the T Tauri are not detected because the radius of such gas disks may be smaller than 70 (50 K/Tex) AU. These results imply that the total amount of matter within the NMA beam size must increase when the central objects evolve into T Tauri stars from embedded sources, suggesting that the compact and highly dense disks around T Tauri stars are formed by the dynamical mass accretion during the embedded protostar phase.

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