scholarly journals Ammonia observations towards the Aquila Rift cloud complex

2020 ◽  
Vol 643 ◽  
pp. A178
Author(s):  
Kadirya Tursun ◽  
Jarken Esimbek ◽  
Christian Henkel ◽  
Xindi Tang ◽  
Gang Wu ◽  
...  
Keyword(s):  
Star Formation ◽  
Dust Emission ◽  
Turbulent Energy ◽  
Gravitational Energy ◽  
High Mass ◽  
Kinetic Temperature ◽  
Mass Star ◽  
Dense Gas ◽  
Star Formation Region ◽  
Formation Region

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.

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

2016 ◽  
Vol 825 (1) ◽  
pp. 54 ◽  
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

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

2016 ◽  
Vol 465 (1) ◽  
pp. 1095-1105 ◽  
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

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

2007 ◽  
Vol 477 (3) ◽  
pp. L45-L48 ◽  
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

Maser Emission in G 339.884−1.259

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.

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

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.

scholarly journals Probing the initial conditions of high-mass star formation

2019 ◽  
Vol 627 ◽  
pp. A85 ◽  
Author(s):  
Chuan-Peng Zhang ◽  
Timea Csengeri ◽  
Friedrich Wyrowski ◽  
Guang-Xing Li ◽  
Thushara Pillai ◽  
...  
Keyword(s):  
Star Formation ◽  
Multiple Scales ◽  
Initial Conditions ◽  
Dust Emission ◽  
Radio Continuum ◽  
High Mass ◽  
Small Scale ◽  
High Angular Resolution ◽  
H Ii Regions ◽  
Mass Star

Context. Fragmentation and feedback are two important processes during the early phases of star formation. Aims. Massive clumps tend to fragment into clusters of cores and condensations, some of which form high-mass stars. In this work, we study the structure of massive clumps at different scales, analyze the fragmentation process, and investigate the possibility that star formation is triggered by nearby H ii regions. Methods. We present a high angular resolution study of a sample of massive proto-cluster clumps G18.17, G18.21, G23.97N, G23.98, G23.44, G23.97S, G25.38, and G25.71. Combining infrared data at 4.5, 8.0, 24, and 70 μm, we use a few arcsecond resolution, radiometer and millimeter inteferometric data taken at 1.3 cm, 3.5 mm, 1.3 mm, and 870 μm to study their fragmentation and evolution. Our sample is unique in the sense that all the clumps have neighboring H ii regions. Taking advantage of that, we tested triggered star formation using a novel method where we study the alignment of the center of mass traced by dust emission at multiple scales. Results. The eight massive clumps, identified based on single-dish observations, have masses ranging from 228 to 2279 M⊙ within an effective radius of Reff ~ 0.5 pc. We detect compact structures towards six out of the eight clumps. The brightest compact structures within infrared bright clumps are typically associated with embedded compact radio continuum sources. The smaller scale structures of Reff ~ 0.02 pc observed within each clump are mostly gravitationally bound and massive enough to form at least a B3-B0 type star. Many condensations have masses larger than 8 M⊙ at a small scale of Reff ~ 0.02 pc. We find that the two infrared quiet clumps with the lowest mass and lowest surface density with <300 M⊙ do not host any compact sources, calling into question their ability to form high-mass stars. Although the clumps are mostly infrared quiet, the dynamical movements are active at clump scale (~1 pc). Conclusions. We studied the spatial distribution of the gas conditions detected at different scales. For some sources we find hints of external triggering, whereas for others we find no significant pattern that indicates triggering is dynamically unimportant. This probably indicates that the different clumps go through different evolutionary paths. In this respect, studies with larger samples are highly desired.

scholarly journals Probing the initial conditions of high-mass star formation

2020 ◽  
Vol 638 ◽  
pp. A105
Author(s):  
Chuan-Peng Zhang ◽  
Guang-Xing Li ◽  
Thushara Pillai ◽  
Timea Csengeri ◽  
Friedrich Wyrowski ◽  
...  
Keyword(s):  
Star Formation ◽  
Initial Conditions ◽  
Active Regions ◽  
High Mass ◽  
Kinetic Temperature ◽  
Mass Star ◽  
Density Peak ◽  
Initial Stage ◽  
Prestellar Cores ◽  
Median Width

Context. The initial stage of star formation is a complex area of study because of the high densities (nH2 > 106 cm−3) and low temperatures (Tdust < 18 K) involved. Under such conditions, many molecules become depleted from the gas phase by freezing out onto dust grains. However, the deuterated species could remain gaseous under these extreme conditions, which would indicate that they may serve as ideal tracers. Aims. We investigate the gas dynamics and NH2D chemistry in eight massive precluster and protocluster clumps (G18.17, G18.21, G23.97N, G23.98, G23.44, G23.97S, G25.38, and G25.71). Methods. We present NH2D 111–101 (at 85.926 GHz), NH3 (1, 1), and (2, 2) observations in the eight clumps using the PdBI and the VLA, respectively. We used 3D GAUSSCLUMPS to extract NH2D cores and provide a statistical view of their deuterium chemistry. We used NH3 (1, 1) and (2, 2) data to investigate the temperature and dynamics of dense and cold objects. Results. We find that the distribution between deuterium fractionation and kinetic temperature shows a number density peak at around Tkin = 16.1 K and the NH2D cores are mainly located at a temperature range of 13.0 to 22.0 K. The 3.5 mm continuum cores have a kinetic temperature with a median width of 22.1 ± 4.3 K, which is obviously higher than the temperature in NH2D cores. We detected seven instances of extremely high deuterium fractionation of 1.0 ≤ Dfrac ≤ 1.41. We find that the NH2D emission does not appear to coincide exactly with either dust continuum or NH3 peak positions, but it often surrounds the star-formation active regions. This suggests that the NH2D has been destroyed by the central young stellar object (YSO) due to heating. The detected NH2D lines are very narrow with a median width of 0.98 ± 0.02 km s−1, which is dominated by non-thermal broadening. The extracted NH2D cores are gravitationally bound (αvir < 1), they are likely to be prestellar or starless, and can potentially form intermediate-mass or high-mass stars in future. Using NH3 (1, 1) as a dynamical tracer, we find evidence of very complicated dynamical movement in all the eight clumps, which can be explained by a combined process with outflow, rotation, convergent flow, collision, large velocity gradient, and rotating toroids. Conclusions. High deuterium fractionation strongly depends on the temperature condition. Tracing NH2D is a poor evolutionary indicator of high-mass star formation in evolved stages, but it is a useful tracer in starless and prestellar cores.

scholarly journals Extended ammonia observations towards the integral-shaped filament

2018 ◽  
Vol 616 ◽  
pp. A111 ◽  
Author(s):  
Gang Wu ◽  
Keping Qiu ◽  
Jarken Esimbek ◽  
Xingwu Zheng ◽  
Christian Henkel ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Gravitational Instability ◽  
Gravitational Energy ◽  
High Mass ◽  
Mass Star ◽  
Filamentary Structure ◽  
Average Spacing ◽  
Prestellar Cores ◽  
Predicted Values

Context. Recent observations suggest a scenario in which filamentary structures in the interstellar medium represent the first step towards clumps/cores and eventually star formation. The densest filaments would then fragment into prestellar cores owing to gravitational instability. Aims. We seek to understand the roles filamentary structures play in high-mass star formation. Methods. We mapped the integral-shaped filament (ISF) located at the northern end of the Orion A molecular cloud in NH3 (1, 1) and (2, 2). The observations were made using the 25 m radio telescope operated by the Xinjiang Astronomical Observatory, Chinese Academy of Sciences. The whole filamentary structure, about 1.2° × 0.6°, is uniformly and fully sampled. We investigate the morphology, fragmentation, kinematics, and temperature properties in this region. Results. We find that the morphology revealed by the map of velocity-integrated intensity of the NH3 (1, 1) line is closely associated with the dust ridge revealed by the Herschel Space Observatory. We identify 6 “lumps” related to the well known OMC-1 to 5 and 11 “sub-clumps” within the map. The clumps and sub-clumps are separated not randomly but in roughly equal intervals along the ISF. The average spacing of clumps is 11.30′ ± 1.31′ (1.36 ± 0.16 pc) and the average spacing of sub-clumps is 7.18′ ± 1.19′ (0.86 ± 0.14 pc). These spacings agree well with the predicted values of the thermal (0.86 pc) and turbulent sausage instability (1.43 pc) by adopting a cylindric geometry of the ISF with an inclination of 60° with respect to the line of sight. We also find a velocity gradient of about 0.6 km s−1 pc−1 that runs along the ISF which likely arises from an overall rotation of the Orion A molecular cloud. The inferred ratio between rotational and gravitational energy is well below unity. Furthermore, fluctuations are seen in the centroid velocity diagram along the ISF. The OMC-1 to 5 clouds are located close to the local extrema of the fluctuations, which suggests that there exist gas flows associated with these clumps in the ISF. The derived NH3 (1, 1) and (2, 2) rotation temperatures in the OMC-1 are about 30–40 K while lower temperatures (below 20 K) are obtained in the northern and southern parts of the ISF. In OMC-2, OMC-3, and the northern part of OMC-4, we find higher and lower temperatures at the boundaries and in the interior, respectively.

scholarly journals ATLASGAL-selected massive clumps in the inner Galaxy

2018 ◽  
Vol 611 ◽  
pp. A6 ◽  
Author(s):  
X. D. Tang ◽  
C. Henkel ◽  
F. Wyrowski ◽  
A. Giannetti ◽  
K. M. Menten ◽  
...  
Keyword(s):  
Star Formation ◽  
Ambient Medium ◽  
Strong Relationship ◽  
High Mass ◽  
Spatial Density ◽  
Physical Parameters ◽  
Molecular Gas ◽  
Kinetic Temperature ◽  
Evolutionary Stage ◽  
Mass Star

Context. Formaldehyde (H2CO) is a reliable tracer to accurately measure the physical parameters of dense gas in star-forming regions. Aim. We aim to determine directly the kinetic temperature and spatial density with formaldehyde for the ~100 brightest ATLASGAL-selected clumps (the TOP100 sample) at 870 μm representing various evolutionary stages of high-mass star formation. Methods. Ten transitions (J = 3–2 and 4–3) of ortho- and para-H2CO near 211, 218, 225, and 291 GHz were observed with the Atacama Pathfinder EXperiment (APEX) 12 m telescope. Results. Using non-LTE models with RADEX, we derived the gas kinetic temperature and spatial density with the measured para-H2CO 321–220/303–202, 422–321/404–303, and 404–303/303–202 ratios. The gas kinetic temperatures derived from the para-H2CO 321–220/303–202 and 422–321/404–303 line ratios are high, ranging from 43 to >300 K with an unweighted average of 91 ± 4 K. Deduced Tkin values from the J = 3–2 and 4–3 transitions are similar. Spatial densities of the gas derived from the para-H2CO 404–303/303–202 line ratios yield 0.6–8.3 × 106 cm−3 with an unweighted average of 1.5 (±0.1) × 106 cm−3. A comparison of kinetic temperatures derived from para-H2CO, NH3, and dust emission indicates that para-H2CO traces a distinctly higher temperature than the NH3 (2, 2)/(1, 1) transitions and the dust, tracing heated gas more directly associated with the star formation process. The H2CO line widths are found to be correlated with bolometric luminosity and increase with the evolutionary stage of the clumps, which suggests that higher luminosities tend to be associated with a more turbulent molecular medium. It seems that the spatial densities measured with H2CO do not vary significantly with the evolutionary stage of the clumps. However, averaged gas kinetic temperatures derived from H2CO increase with time through the evolution of the clumps. The high temperature of the gas traced by H2CO may be mainly caused by radiation from embedded young massive stars and the interaction of outflows with the ambient medium. For Lbol/Mclump ≳ 10 L⊙/M⊙, we find a rough correlation between gas kinetic temperature and this ratio, which is indicative of the evolutionary stage of the individual clumps. The strong relationship between H2CO line luminosities and clump masses is apparently linear during the late evolutionary stages of the clumps, indicating that LH_2CO does reliably trace the mass of warm dense molecular gas. In our massive clumps H2CO line luminosities are approximately linearly correlated with bolometric luminosities over about four orders of magnitude in Lbol, which suggests that the mass of dense molecular gas traced by the H2CO line luminosity is well correlated with star formation.

Sign in / Sign up

Export Citation Format

Share Document