scholarly journals Herschel Galactic Cold Cloud Core Analysis

2012 ◽  
Vol 8 (S292) ◽  
pp. 115-115
Author(s):  
Erika Verebelyi ◽  
Laurent Pagani
Keyword(s):  
Molecular Cloud ◽  
Core Analysis ◽  
Molecular Line ◽  
Line Measurement ◽  
The Galaxy ◽  
Cloud Cores ◽  
Cloud Core

AbstractWe have compiled a sample of 106 lesser-known cores from the Herschel Galactic Cold Cloud Cores Key Program (Juvela, M. et al. 2007). Based on the assumption, that these represent the crowd of the cold cores in the galaxy well, we have started a deep individual investigation, beginning with a ground-based follow-up and molecular line measurement at IRAM 30m telescope. We present the methods and calculated values of the most important parameters on a selected source: the G130.38+11.25 molecular cloud, which is part of the L1340.

Ammonia Mapping of the Southern Molecular Cloud NGC 6334

1987 ◽  
Vol 7 (2) ◽  
pp. 189-193 ◽  
Author(s):  
J. R. Forster ◽  
J. B. Whiteoak ◽  
F. F. Gardner ◽  
W. L. Peters ◽  
T. B. H. Kuiper
Keyword(s):  
Molecular Cloud ◽  
Line Emission ◽  
Ammonia Emission ◽  
Molecular Line ◽  
Ir Sources ◽  
Linear Resolution ◽  
The Galaxy ◽  
Velocity Anomalies ◽  
Ngc 6334 ◽  
Cloud Complex

AbstractThe Parkes 64-m antenna has been used to map ammonia emission in the (J,K = 1,1) and (J,K = 2,2) transitions toward molecular cloud complex NGC 6334. This complex contains a number of OH and H2O masers, HII regions and IR sources, and is a rich source of molecular line emission.Distributions of observed and derived quantities are presented with a linear resolution of ∼ 1 pc. Velocity anomalies are present near the two OH masers NGC 6334A and B, and the source of ammonia emission located near the northernmost H2O maser is one of the most intense sources of NH3 emission in the Galaxy.

scholarly journals Accretion and the Properties of Protobinary Systems

2001 ◽  
Vol 200 ◽  
pp. 429-438 ◽  
Author(s):  
Matthew R. Bate
Keyword(s):  
Molecular Cloud ◽  
Stellar Clusters ◽  
Mass Ratio ◽  
Final Mass ◽  
Cloud Cores ◽  
The Masses ◽  
Gaseous Envelope ◽  
Cloud Core

We discuss the evolution of the properties of a protobinary system which forms via fragmentation within a collapsing molecular cloud core and grows to its final mass by accreting from the gaseous envelope. We predict how the mass ratio distributions and the masses of the circumstellar and circumbinary discs depend on the binary's separation, the primary's mass, and the properties of the pre-collapse molecular cloud core. We also discuss how the properties of binaries may depend on whether they were formed in isolated molecular cloud cores or in stellar clusters.

scholarly journals New Sample of Young Stellar Objects

1991 ◽  
Vol 147 ◽  
pp. 466-475
Author(s):  
S. M. Moy ◽  
G. H. MacDonald ◽  
R. J. Habing
Keyword(s):  
Molecular Cloud ◽  
Stellar Object ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Young Stellar Object ◽  
Large Samples ◽  
Protostellar Objects ◽  
Cloud Cores ◽  
Infrared Sources ◽  
Cloud Core

in recent years there has been much interest in the study of large samples of molecular cloud cores and related infrared sources in an attempt to observe true protostars - objects in transition between a molecular cloud core and a young stellar object (YSO). We present here a survey of 48 possible protostellar objects chosen initially by their IRAS colours and subsequently observed in (1—0) HCO+ emission at Onsala in Feb 1990. Future observations in (3—2)13CO & (3—2)12CO will be made with the JCMT and in (1,1) and (2,2) NH3 emission with the Bonn 100m telescope.

A double core in the Auriga-California Molecular Cloud

2018 ◽  
Vol 14 (S345) ◽  
pp. 335-336
Author(s):  
Sarolta Zahorecz ◽  
Daniel Molnar ◽  
Alex Kraus ◽  
Toshikazu Onishi
Keyword(s):  
Radiative Transfer ◽  
Molecular Cloud ◽  
Molecular Line ◽  
3 Dimensional ◽  
Dense Cores ◽  
Open Time ◽  
Radiative Transfer Modeling ◽  
Line Observation

AbstractPlanck cold clump G163.82-8.44 is part of the Auriga-California Molecular Cloud. It was observed with Herschel PACS and SPIRE instruments as part of the Herschel open time key programme Galactic Cold Cores. Follow-up ground-based molecular line observation of NH3 was performed to the densest part of the filament with the Effelsberg-100m telescope. We detected two different velocity components with a separation of 0.5 km/s. We performed radiative transfer modeling with two 3-dimensional spheres to characterise the temperature and density of the dense cores. We have found that the temperatures of the two cores are almost the same, 10.8 K and 11.1 K and their mass and size ratios are 1:10 and 1:5, respectively.

scholarly journals New Sample of Young Stellar Objects

1991 ◽  
Vol 147 ◽  
pp. 466-475
Author(s):  
S. M. Moy ◽  
G. H. MacDonald ◽  
R. J. Habing
Keyword(s):  
Molecular Cloud ◽  
Stellar Object ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Young Stellar Object ◽  
Large Samples ◽  
Protostellar Objects ◽  
Cloud Cores ◽  
Infrared Sources ◽  
Cloud Core

in recent years there has been much interest in the study of large samples of molecular cloud cores and related infrared sources in an attempt to observe true protostars - objects in transition between a molecular cloud core and a young stellar object (YSO). We present here a survey of 48 possible protostellar objects chosen initially by their IRAS colours and subsequently observed in (1—0) HCO+ emission at Onsala in Feb 1990. Future observations in (3—2)13CO & (3—2)12CO will be made with the JCMT and in (1,1) and (2,2) NH3 emission with the Bonn 100m telescope.

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.

scholarly journals Chemical variation in molecular cloud cores in the Orion A Cloud. III

2014 ◽  
Vol 66 (6) ◽  
pp. 119 ◽  
Author(s):  
Satoshi Ohashi ◽  
Ken'ichi Tatematsu ◽  
Minho Choi ◽  
Miju Kang ◽  
Tomofumi Umemoto ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Chemical Variation ◽  
Cloud Cores

scholarly journals Understanding biases in measurements of molecular cloud kinematics using line emission

2020 ◽  
Vol 498 (2) ◽  
pp. 2440-2455
Author(s):  
Yuxuan (宇轩) Yuan (原) ◽  
Mark R Krumholz ◽  
Blakesley Burkhart
Keyword(s):  
Magnetic Field ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Velocity Dispersion ◽  
Signal To Noise Ratio ◽  
Line Emission ◽  
Molecular Line ◽  
Velocity Dispersions ◽  
Cloud Kinematics ◽  
Measurement Biases

ABSTRACT Molecular line observations using a variety of tracers are often used to investigate the kinematic structure of molecular clouds. However, measurements of cloud velocity dispersions with different lines, even in the same region, often yield inconsistent results. The reasons for this disagreement are not entirely clear, since molecular line observations are subject to a number of biases. In this paper, we untangle and investigate various factors that drive linewidth measurement biases by constructing synthetic position–position–velocity cubes for a variety of tracers from a suite of self-gravitating magnetohydrodynamic simulations of molecular clouds. We compare linewidths derived from synthetic observations of these data cubes to the true values in the simulations. We find that differences in linewidth as measured by different tracers are driven by a combination of density-dependent excitation, whereby tracers that are sensitive to higher densities sample smaller regions with smaller velocity dispersions, opacity broadening, especially for highly optically thick tracers such as CO, and finite resolution and sensitivity, which suppress the wings of emission lines. We find that, at fixed signal-to-noise ratio, three commonly used tracers, the J = 4 → 3 line of CO, the J = 1 → 0 line of C18O, and the (1,1) inversion transition of NH3, generally offer the best compromise between these competing biases, and produce estimates of the velocity dispersion that reflect the true kinematics of a molecular cloud to an accuracy of $\approx 10{{\ \rm per\ cent}}$ regardless of the cloud magnetic field strengths, evolutionary state, or orientations of the line of sight relative to the magnetic field. Tracers excited primarily in gas denser than that traced by NH3 tend to underestimate the true velocity dispersion by $\approx 20{{\ \rm per\ cent}}$ on average, while low-density tracers that are highly optically thick tend to have biases of comparable size in the opposite direction.

scholarly journals A new distance to the Brick, the dense molecular cloud G0.253+0.016

2021 ◽  
Vol 502 (1) ◽  
pp. 1246-1252
Author(s):  
M Zoccali ◽  
E Valenti ◽  
F Surot ◽  
O A Gonzalez ◽  
A Renzini ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Near Infrared ◽  
Formation Rate ◽  
Dynamical Evolution ◽  
Galactic Centre ◽  
The Galaxy ◽  
Centre Region ◽  
Order Of Magnitude ◽  
Red Clump

ABSTRACT We analyse the near-infrared colour–magnitude diagram of a field including the giant molecular cloud G0.253+0.016 (a.k.a. The Brick) observed at high spatial resolution, with HAWK-I@VLT. The distribution of red clump stars in a line of sight crossing the cloud, compared with that in a direction just beside it, and not crossing it, allow us to measure the distance of the cloud from the Sun to be 7.20, with a statistical uncertainty of ±0.16 and a systematic error of ±0.20 kpc. This is significantly closer than what is generally assumed, i.e. that the cloud belongs to the near side of the central molecular zone, at 60 pc from the Galactic centre. This assumption was based on dynamical models of the central molecular zone, observationally constrained uniquely by the radial velocity of this and other clouds. Determining the true position of the Brick cloud is relevant because this is the densest cloud of the Galaxy not showing any ongoing star formation. This puts the cloud off by one order of magnitude from the Kennicutt–Schmidt relation between the density of the dense gas and the star formation rate. Several explanations have been proposed for this absence of star formation, most of them based on the dynamical evolution of this and other clouds, within the Galactic centre region. Our result emphasizes the need to include constraints coming from stellar observations in the interpretation of our Galaxy’s central molecular zone.

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