Millimeter observations of organic molecules toward high-mass star formation region G34.26+0.15

We surveyed the Aquila Rift complex including the Serpens South and W 40 regions in the NH3 (1,1) and (2,2) transitions making use of the Nanshan 26-m telescope. Our observations cover an area of ~ 1.5° × 2.2° (11.4 pc × 16.7 pc). The kinetic temperatures of the dense gas in the Aquila Rift complex obtained from NH3 (2,2)/(1,1) ratios range from 8.9 to 35.0 K with an average of 15.3 ± 6.1 K (errors are standard deviations of the mean). Low gas temperatures are associated with Serpens South ranging from 8.9 to 16.8 K with an average of 12.3 ± 1.7 K, while dense gas in the W 40 region shows higher temperatures ranging from 17.7 to 35.0 K with an average of 25.1 ± 4.9 K. A comparison of kinetic temperatures derived from para-NH3 (2,2)/(1,1) against HiGal dust temperatures indicates that the gas and dust temperatures are in agreement in the low-mass-star formation region of Serpens South. In the high-mass-star formation region W 40, the measured gas kinetic temperatures are higher than those of the dust. The turbulent component of the velocity dispersion of NH3 (1,1) is found to be positively correlated with the gas kinetic temperature, which indicates that the dense gas may be heated by dissipation of turbulent energy. For the fractional total-NH3 (para+ortho) abundance obtained by a comparison with Herschel infrared continuum data representing dust emission, we find values from 0.1 ×10−8 to 2.1 ×10−7 with an average of 6.9 (±4.5) × 10−8. Serpens South also shows a fractional total-NH3 (para+ortho) abundance ranging from 0.2 ×10−8 to 2.1 ×10−7 with an average of 8.6 (±3.8) × 10−8. In W 40, values are lower, between 0.1 and 4.3 ×10−8 with an average of 1.6 (±1.4) × 10−8. Weak velocity gradients demonstrate that the rotational energy is a negligible fraction of the gravitational energy. In W 40, gas and dust temperatures are not strongly dependent on the projected distance to the recently formed massive stars. Overall, the morphology of the mapped region is ring-like, with strong emission at lower and weak emission at higher Galactic longitudes. However, the presence of a physical connection between the two parts remains questionable.

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A MID-INFRARED VIEW OF THE HIGH MASS STAR FORMATION REGION W51A

The Astrophysical Journal ◽

10.3847/0004-637x/825/1/54 ◽

2016 ◽

Vol 825 (1) ◽

pp. 54 ◽

Cited By ~ 2

Author(s):

C. L. Barbosa ◽

R. D. Blum ◽

A. Damineli ◽

P. S. Conti ◽

D. M. Gusmão

Keyword(s):

Star Formation ◽

High Mass ◽

Mass Star ◽

Mid Infrared ◽

Star Formation Region ◽

Formation Region

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Parallaxes of 6.7-GHz methanol masers towards the G 305.2 high-mass star formation region

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stw2850 ◽

2016 ◽

Vol 465 (1) ◽

pp. 1095-1105 ◽

Cited By ~ 19

Author(s):

V. Krishnan ◽

S. P. Ellingsen ◽

M. J. Reid ◽

H. E. Bignall ◽

J. McCallum ◽

...

Keyword(s):

Star Formation ◽

High Mass ◽

Mass Star ◽

Star Formation Region ◽

Formation Region ◽

Methanol Masers

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Highly deuterated pre-stellar cores in a high-mass star formation region

Astronomy and Astrophysics ◽

10.1051/0004-6361:20078973 ◽

2007 ◽

Vol 477 (3) ◽

pp. L45-L48 ◽

Cited By ~ 21

Author(s):

F. Fontani ◽

P. Caselli ◽

T. L. Bourke ◽

R. Cesaroni ◽

J. Brand

Keyword(s):

Star Formation ◽

High Mass ◽

Mass Star ◽

Star Formation Region ◽

Formation Region

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Maser Emission in G 339.884−1.259

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317010444 ◽

2017 ◽

Vol 13 (S336) ◽

pp. 334-335

Author(s):

V. Krishnan ◽

L. Moscadelli ◽

S. P. Ellingsen ◽

H. E. Bignall ◽

S. L. Breen ◽

...

Keyword(s):

Star Formation ◽

High Mass ◽

Mass Star ◽

Proper Motions ◽

Star Formation Region ◽

Formation Region ◽

Gas Kinematics ◽

Long Baseline ◽

Vlbi Observations ◽

Water Masers

AbstractWe present multi–epoch VLBI observations of the methanol and water masers in the high–mass star formation region G 339.884−1.259, made using the Australian Long Baseline Array (LBA). Our sub–milliarcsecond precision measurements trace the proper motions of individual maser features in the plane of the sky. When combined with the direct line–of–sight radial velocity (vlsr), these measure the 3 D gas kinematics of the associated high–mass star formation region, allowing us to probe the dynamical processes to within 1000 AU of the core.

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SMA, VLA and VLBA observations in a 105 L⊙ high mass star formation region IRAS 18360-0537

Proceedings of the International Astronomical Union ◽

10.1017/s174392131700895x ◽

2017 ◽

Vol 13 (S336) ◽

pp. 291-292

Author(s):

Gang Wu ◽

Keping Qiu ◽

Jarken Esimbek ◽

Xingwu Zheng

Keyword(s):

Star Formation ◽

Far Infrared ◽

High Mass ◽

Mass Star ◽

Comprehensive Understanding ◽

Promising Candidate ◽

Star Formation Region ◽

Formation Region ◽

Young Stellar Object ◽

Outflow System

AbstractWe have observed a young stellar object, IRAS 18360-0537, with a far-infrared luminosity of 1.2 × 105 L⊙. It is perhaps the most promising candidate of a high-mass protostar associated with a Keplerian disk and a jet/outflow system in the regime of L > 105L⊙. We are conducting the SMA, VLA, and VLBA studies to provide a comprehensive understanding of this interesting high mass star formation scenario.

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Evolutionary study of complex organic molecules in high-mass star-forming regions

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038212 ◽

2020 ◽

Vol 641 ◽

pp. A54 ◽

Cited By ~ 1

Author(s):

A. Coletta ◽

F. Fontani ◽

V. M. Rivilla ◽

C. Mininni ◽

L. Colzi ◽

...

Keyword(s):

Star Formation ◽

Organic Molecules ◽

High Mass ◽

Physical Parameters ◽

Mass Star ◽

Evolutionary Trend ◽

Star Forming ◽

Star Forming Regions ◽

Molecular Abundances ◽

Complex Organic

We have studied four complex organic molecules (COMs), the oxygen-bearing methyl formate (CH3OCHO) and dimethyl ether (CH3OCH3) as well as the nitrogen-bearing formamide (NH2CHO) and ethyl cyanide (C2H5CN), towards a large sample of 39 high-mass star-forming regions representing different evolutionary stages, from early to evolved phases. We aim to identify potential correlations and chemical links between the molecules and to trace their evolutionary sequence through the star formation process. We analysed spectra obtained at 3, 2, and 0.9 mm with the IRAM-30m telescope. We derived the main physical parameters for each species by fitting the molecular lines. We compared them and evaluated their evolution while also taking several other interstellar environments into account. We report detections in 20 sources, revealing a clear dust absorption effect on column densities. Derived abundances range between ~ 10−10−10−7 for CH3OCHO and CH3OCH3, ~ 10−12−10−10 for NH2CHO, and ~ 10−11−10−9 for C2H5CN. The abundances of CH3OCHO, CH3OCH3, and C2H5CN are very strongly correlated (r ≥ 0.92) across ~ 4 orders of magnitude. We note that CH3OCHO and CH3OCH3 show the strongest correlations in most parameters, and a nearly constant ratio (~ 1) over a remarkable ~ 9 orders of magnitude in luminosity for the following wide variety of sources: pre-stellar to evolved cores, low- to high-mass objects, shocks, Galactic clouds, and comets. This indicates that COMs chemistry is likely early developed and then preserved through evolved phases. Moreover, the molecular abundances clearly increase with evolution, covering ~ 6 orders of magnitude in the luminosity/mass ratio. We consider CH3OCHO and CH3OCH3 to be most likely chemically linked. They could, for example, share a common precursor, or be formed one from the other. Based on correlations, ratios, and the evolutionary trend, we propose a general scenario for all COMs, involving a formation in the cold, earliest phases of star formation and a following increasing desorption with the progressive thermal and shock-induced heating of the evolving core.

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The Chamaeleon Dark Clouds Complex: Preliminary Analysis of the Colour Excesses E(b-y) Towards the Selected Area 203

International Astronomical Union Colloquium ◽

10.1017/s0252921100023642 ◽

1989 ◽

Vol 120 ◽

pp. 133-133

Author(s):

G.A.P. Franco

Keyword(s):

Star Formation ◽

Preliminary Analysis ◽

Galactic Plane ◽

Mass Star ◽

The Sun ◽

Star Formation Region ◽

Formation Region ◽

Dark Clouds ◽

Low Mass ◽

Selective Extinction

The Chamaeleon dark clouds form a large complex of interstellar obscuring material situated at ≈ 15° below the galactic plane. Although it is accepted as being one of the closest low-mass star formation region to the Sun, its distance has been debated issues. The proposed distance is in general dependent on the value assumed for the ratio of total-to-selective extinction, which in the Chamaeleon clouds has proved controversial, leading to distances estimates ranging from 115 to 215 pc.

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From clump to disc scales in W3 IRS4

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834152 ◽

2020 ◽

Vol 636 ◽

pp. A118

Author(s):

J. C. Mottram ◽

H. Beuther ◽

A. Ahmadi ◽

P. D. Klaassen ◽

M. T. Beltrán ◽

...

Keyword(s):

Star Formation ◽

Spatial Scales ◽

High Mass ◽

Bulk Temperature ◽

Mass Star ◽

Star Formation Region ◽

Physical And Chemical ◽

First Time ◽

Core Fragmentation

Context. High-mass star formation typically takes place in a crowded environment, with a higher likelihood of young forming stars affecting and being affected by their surroundings and neighbours, as well as links between different physical scales affecting the outcome. However, observational studies are often focused on either clump or disc scales exclusively. Aims. We explore the physical and chemical links between clump and disc scales in the high-mass star formation region W3 IRS4, a region that contains a number of different evolutionary phases in the high-mass star formation process, as a case-study for what can be achieved as part of the IRAM NOrthern Extended Millimeter Array (NOEMA) large programme named CORE: “Fragmentation and disc formation in high-mass star formation”. Methods. We present 1.4 mm continuum and molecular line observations with the IRAM NOEMA interferometer and 30 m telescope, which together probe spatial scales from ~0.3−20′′ (600−40 000 AU or 0.003−0.2 pc at 2 kpc, the distance to W3). As part of our analysis, we used XCLASS to constrain the temperature, column density, velocity, and line-width of the molecular emission lines. Results. The W3 IRS4 region includes a cold filament and cold cores, a massive young stellar object (MYSO) embedded in a hot core, and a more evolved ultra-compact (UC)H II region, with some degree of interaction between all components of the region that affects their evolution. A large velocity gradient is seen in the filament, suggesting infall of material towards the hot core at a rate of 10−3−10−4 M⊙ yr−1, while the swept up gas ring in the photodissociation region around the UCH II region may be squeezing the hot core from the other side. There are no clear indications of a disc around the MYSO down to the resolution of the observations (600 AU). A total of 21 molecules are detected, with the abundances and abundance ratios indicating that many molecules were formed in the ice mantles of dust grains at cooler temperatures, below the freeze-out temperature of CO (≲35 K). This contrasts with the current bulk temperature of ~50 K, which was obtained from H2CO. Conclusions. CORE observations allow us to comprehensively link the different structures in the W3 IRS4 region for the first time. Our results argue that the dynamics and environment around the MYSO W3 IRS4 have a significant impact on its evolution. This context would be missing if only high resolution or continuum observations were available.

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