Ammonia cores in high mass star formation regions

Wu, Yuefang; Zhang, Qizhou; Yu, Wentao; Miller, M.; Mao, Rihua; Sun, K.; Wang, Y

doi:10.1051/0004-6361:20053203

Cited by 53 publications

(80 citation statements)

References 35 publications

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“…13. A correlation between T K and L bol was also found by e.g., Churchwell et al (1990), Wu et al (2006), Urquhart et al (2011), and by Sánchez-Monge et al (2013b), for cores in clustered environments, using the luminosity of the whole region.…”

Section: Temperaturessupporting

confidence: 70%

Physical properties of high-mass clumps in different stages of evolution

Giannetti

Brand

Sánchez-Monge

et al. 2013

A&A

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Context. The details of the process of massive star formation are still elusive. A complete characterization of the first stages of the process from an observational point of view is needed to constrain theories on the subject. In the past 20 years we have made a thorough investigation of colour-selected IRAS sources over the whole sky. The sources in the northern hemisphere were studied in detail and used to derive an evolutionary sequence based on their spectral energy distribution. Aims. To investigate the first stages of the process of high-mass star formation, we selected a sample of massive clumps previously observed with the Swedish-ESO Submillimetre Telescope at 1.2 mm and with the ATNF Australia Telescope Compact Array at 1.3 cm. We want to characterize the physical conditions in such sources, and test whether their properties depend on the evolutionary stage of the clump. Methods. With ATCA we observed the selected sources in the NH 3 (1, 1) and (2, 2) transitions and in the H 2 O(6 16 −5 23 ) maser line. Ammonia lines are a very good temperature probe that allow us to accurately determine the mass and the column, volume, and surface densities of the clumps. We also collected all data available to construct the spectral energy distribution of the individual clumps and to determine if star formation is already occurring through observations of its most common signposts, thus putting constraints on the evolutionary stage of the source. We fitted the spectral energy distribution between 1.2 mm and 70 µm with a modified black body to derive the dust temperature and independently determine the mass. Results. We find that the clumps are cold (T ∼ 10−30 K), massive (M ∼ 10 2 −10 3 M ), and dense (n(H 2 ) 10 5 cm −3 ) and that they have high column densities (N(H 2 ) ∼ 10 23 cm −2 ). All clumps appear to be potentially able to form high-mass stars. The most massive clumps appear to be gravitationally unstable, if the only sources of support against collapse are turbulence and thermal pressure, which possibly indicates that the magnetic field is important in stabilizing them. Conclusions. After investigating how the average properties depend on the evolutionary phase of the source, we find that the temperature and central density progressively increase with time. Sources likely hosting a ZAMS star show a steeper radial dependence of the volume density and tend to be more compact than starless clumps.

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Section: Temperaturessupporting

confidence: 70%

Physical properties of high-mass clumps in different stages of evolution

Giannetti

Brand

Sánchez-Monge

et al. 2013

A&A

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“…Previous observations of NH 3 (Wouterloot et al 1988;Myers et al 1991;Harju et al 1993;Ladd et al 1994;Molinari et al 1996;Jijina et al 1999;Wu et al 2006;Urquhart et al 2011Urquhart et al , 2015, C 18 O (Saito et al 2001;Ridge et al 2003;Maud et al 2015), and 13 CO (Wang et al 2009;Lundquist et al 2015) suggest that the line width is correlated with luminosity, which indicates the presence of a link between formed stars and velocity dispersion. We investigate the line width-luminosity relation in the case of the dense gas tracer H 2 CO. We plot the line width-luminosity relation in Figure 9.…”

Section: Line Width-luminosity Relationmentioning

confidence: 90%

ATLASGAL-selected massive clumps in the inner Galaxy

Tang

Henkel

Wyrowski

et al. 2018

A&A

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Context. Formaldehyde (H 2 CO) is a reliable tracer to accurately measure the physical parameters of dense gas in star-forming regions. Aims. We aim to determine directly the kinetic temperature and spatial density with formaldehyde for the ∼100 brightest ATLASGALselected 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-H 2 CO 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-H 2 CO 3 21 -2 20 /3 03 -2 02 , 4 22 -3 21 /4 04 -3 03 , and 4 04 -3 03 /3 03 -2 02 ratios. The gas kinetic temperatures derived from the para-H 2 CO 3 21 -2 20 /3 03 -2 02 and 4 22 -3 21 /4 04 -3 03 line ratios are high, ranging from 43 to >300 K with an unweighted average of 91 ± 4 K. Deduced T kin values from the J = 3-2 and 4-3 transitions are similar. Spatial densities of the gas derived from the para-H 2 CO 4 04 -3 03 /3 03 -2 02 line ratios yield 0.6-8.3 × 10 6 cm −3 with an unweighted average of 1.5 (±0.1) × 10 6 cm −3 . A comparison of kinetic temperatures derived from para-H 2 CO, NH 3 , and dust emission indicates that para-H 2 CO traces a distinctly higher temperature than the NH 3 (2,2)/(1,1) transitions and the dust, tracing heated gas more directly associated with the star formation process. The H 2 CO 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 H 2 CO do not vary significantly with the evolutionary stage of the clumps. However, averaged gas kinetic temperatures derived from H 2 CO increase with time through the evolution of the clumps. The high temperature of the gas traced by H 2 CO may be mainly caused by radiation from embedded young massive stars and the interaction of outflows with the ambient medium. For L bol /M clump 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 H 2 CO line luminosities and clump masses is apparently linear during the late evolutionary stages of the clumps, indicating that L H 2 CO does reliably trace the mass of warm dense molecular gas. In our massive clumps H 2 CO line luminosities are approximately linearly correlated with bolometric luminosities over about four orders of magnitude in L bol , which suggests that the mass of dense molecular gas traced by the H 2 CO line luminosity is well correlated with star formation.

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“…Towards C5, dense molecular tracers such as CS (Beuther et al 2002) and NH 3 (Wu et al 2006) have been observed. The signature of high-velocity CO gas (Yang et al 2002) has also been reported towards C5.…”

Section: Nature Of Sources Within Ir Blobs And/or Clumpsmentioning

confidence: 99%

The molecular complex associated with the Galactic H II region Sh2-90: a possible site of triggered star formation

Samal

Zavagno

Deharveng

et al. 2014

A&A

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Aims. We investigate the star formation activity in the molecular complex associated with the Galactic H ii region Sh2-90.Methods. We obtain the distribution of the ionized and cold neutral gas using radio-continuum and Herschel observations. We use near-infrared and Spitzer data to investigate the stellar content of the complex. We discuss the evolutionary status of embedded massive young stellar objects (MYSOs) using their spectral energy distribution.Results. The Sh2-90 region presents a bubble morphology in the mid-infrared. Radio observations suggest it is an evolved H ii region with an electron density ∼144 cm −3 , emission measure ∼6.7 × 10 4 cm −6 pc and an ionized mass ∼55 M . From Herschel and CO (J = 3−2) observations we found that the H ii region is part of an elongated extended molecular cloud (H 2 column density ≥3 × 10 21 cm −2 and dust temperature 18−27 K) of total mass ≥1 × 10 4 M . We identify the ionizing cluster of Sh2-90, the main exciting star being an O8-O9 V star. Five cold dust clumps, four mid-IR blobs around B stars, and a compact H ii region are found at the edge of the bubble. The velocity information derived from CO data cubes suggest that most of them are associated with the Sh2-90 region. One hundred and twenty-nine low mass (≤3 M ) YSOs have been identified, and they are found to be distributed mostly in the regions of high column density. Four candidate Class 0/I MYSOs have been found. We suggest that multi-generation star formation is present in the complex. From evidence of interaction, time scales involved, and evolutionary status of stellar/protostellar sources, we argue that the star formation at the edges of Sh2-90 might have been triggered. However, several young sources in this complex are probably formed by some other processes.

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Ammonia cores in high mass star formation regions

Cited by 53 publications

References 35 publications

Physical properties of high-mass clumps in different stages of evolution

Physical properties of high-mass clumps in different stages of evolution

ATLASGAL-selected massive clumps in the inner Galaxy

The molecular complex associated with the Galactic H II region Sh2-90: a possible site of triggered star formation

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