The Molecular Gas Environment in the 20 km s<sup>−1</sup> Cloud in the Central Molecular Zone

Lu, Xing; Zhang, Qizhou; Kauffmann, Jens; Pillai, T.; Longmore, Steven N.; Kruijssen, J. M. Diederik; Battersby, Cara; Liu, Hauyu Baobab; Ginsburg, Adam; Mills, Elisabeth A. C.; Zhang, Zhiyu; Gu, Qiusheng

doi:10.3847/1538-4357/aa67f7

Cited by 40 publications

(48 citation statements)

References 81 publications

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“…age of 91 ± 4 K; these values agree with the results measured with H 2 CO in other massive star-forming regions and Galactic centre clouds Hurt et al 1996;Mangum et al 1999;Watanabe & Mitchell 2008;Nagy et al 2012;Ao et al 2013;Ginsburg et al 2016;Immer et al 2016;Lu et al 2017). Most of our clumps, including the detected 70 µm weak clumps, are very warm, which indicates that there is likely ongoing massive star formation in most of our sample.…”

Section: Comparison Of Kinetic Temperatures Derived From Gas and Dustsupporting

confidence: 89%

“…The results are listed in Table A.1. The derived dust temperature range in our observed sources is 11-41 K with an unweighted average of 25 ± 7 K. Previous observations show that the temperatures derived from gas and dust are often in agreement in the active dense clumps of Galactic disk clouds Giannetti et al 2013;Battersby et al 2014), but do not agree in the Galactic CMZ (Güsten et al 1981;Ao et al 2013;Ott et al 2014;Ginsburg et al 2016;Immer et al 2016;Lu et al 2017). As in the CMZ, the gas kinetic temperatures derived from para-H 2 CO show higher values than the dust temperature with no apparent correlation (correlation coefficient R ∼ 0.2) between T dust and T gas (see Fig.…”

Section: Comparison Of Kinetic Temperatures Derived From Gas and Dustmentioning

confidence: 44%

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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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Section: Comparison Of Kinetic Temperatures Derived From Gas and Dustsupporting

confidence: 89%

Section: Comparison Of Kinetic Temperatures Derived From Gas and Dustmentioning

confidence: 44%

ATLASGAL-selected massive clumps in the inner Galaxy

Tang

Henkel

Wyrowski

et al. 2018

A&A

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“…The distribution of para-H 2 CO (3 03 -2 02 ) is similar to the spatial distribution of the NH 3 (1,1) and (2,2) emission mapped with the Green Bank Telescope (GBT) (beam size ∼30 ′′ ; A&A proofs: manuscript no. OMC1-Tkin 2 02 ) and NH 3 (1,1) and (2,2) in the OMC-1 region are consistent with previous observational results in the Galactic Central Molecular Zone (CMZ) on a ∼0.1 pc scale (Lu et al 2017). The strongest H 2 CO (3 03 -2 02 ) emission associates with the massive star formation regions Orion KL and Orion South, which is consistent with the NH 3 (2,2) emission.…”

Section: Distribution Of H 2 Cosupporting

confidence: 79%

“…Therefore the line strength ratios of para-H 2 CO, 3 22 -2 21 /3 03 -2 02 and 3 21 -2 20 /3 03 -2 02 , provide a sensitive thermometer, possibly the best of the very few which are available for the analysis of dense molecular gas. These H 2 CO line ratios have been used to measure physical parameters in our Galactic center clouds (Qin et al 2008;Ao et al 2013;Johnston et al 2014;Ginsburg et al 2016;Immer et al 2016;Lu et al 2017), star formation regions Hurt et al 1996;Mitchell et al 2001;Watanabe & Mitchell 2008;Lindberg et al 2015;Tang et al 2017a,c), as well as in external galaxies (Mühle et al 2007;Tang et al 2017b). …”

Section: Introductionmentioning

confidence: 99%

Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde

Tang

Henkel

Menten

et al. 2017

A&A

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We mapped the kinetic temperature structure of the Orion molecular cloud 1 (OMC-1) with para-H 2 CO (J KaKc = 3 03 -2 02 , 3 22 -2 21 , and 3 21 -2 20 ) using the APEX 12 m telescope. This is compared with the temperatures derived from the ratio of the NH 3 (2,2)/(1,1) inversion lines and the dust emission. Using the RADEX non-LTE model, we derive the gas kinetic temperature modeling the measured averaged line ratios of para-H 2 CO 3 22 -2 21 /3 03 -2 02 and 3 21 -2 20 /3 03 -2 02 . The gas kinetic temperatures derived from the para-H 2 CO line ratios are warm, ranging from 30 to >200 K with an average of 62 ± 2 K at a spatial density of 10 5 cm −3 . These temperatures are higher than those obtained from NH 3 (2,2)/(1,1) and CH 3 CCH (6-5) in the OMC-1 region. The gas kinetic temperatures derived from para-H 2 CO agree with those obtained from warm dust components measured in the mid infrared (MIR), which indicates that the para-H 2 CO (3-2) ratios trace dense and warm gas. The cold dust components measured in the far infrared (FIR) are consistent with those measured with NH 3 (2,2)/(1,1) and the CH 3 CCH (6-5) line series. With dust at MIR wavelengths and para-H 2 CO (3-2) on one side and dust at FIR wavelengths, NH 3 (2,2)/(1,1), and CH 3 CCH (6-5) on the other, dust and gas temperatures appear to be equivalent in the dense gas (n(H 2 ) 10 4 cm −3 ) of the OMC-1 region, but provide a bimodal distribution, one more directly related to star formation than the other. The non-thermal velocity dispersions of para-H 2 CO are positively correlated with the gas kinetic temperatures in regions of strong non-thermal motion (Mach number 2.5) of the OMC-1, implying that the higher temperature traced by para-H 2 CO is related to turbulence on a ∼0.06 pc scale. Combining the temperature measurements with para-H 2 CO and NH 3 (2,2)/(1,1) line ratios, we find direct evidence for the dense gas along the northern part of the OMC-1 10 km s −1 filament heated by radiation from the central Orion nebula.

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“…These clouds contain some of the most active embedded star formation activity in the Galactic Centre region (Lu et al 2015(Lu et al , 2017. It is therefore unclear if these clouds had intrinsically large velocity dispersions before forming stars, or whether the affect of stellar feedback may have been responsible for increasing their velocity dispersions from their pre-star formation state.…”

Section: G a L Ac T I C C E N T R E G A S K I N E M At I C P Ro P E Rmentioning

confidence: 99%

H2O Southern Galactic Plane Survey (HOPS): Paper III – properties of dense molecular gas across the inner Milky Way

Longmore

Walsh

Purcell

et al. 2017

Monthly Notices of the Royal Astronomical Society

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The H 2 O Southern Galactic Plane Survey (HOPS) has mapped 100 deg 2 of the Galactic plane for water masers and thermal molecular line emission using the 22 m Mopra telescope. We describe the automated spectral-line fitting pipelines used to determine the properties of emission detected in HOPS data cubes, and use these to derive the physical and kinematic properties of gas in the survey. A combination of the angular resolution, sensitivity, velocity resolution and high critical density of lines targeted make the HOPS data cubes ideally suited to finding precursor clouds to the most massive and dense stellar clusters in the Galaxy. We compile a list of the most massive HOPS ammonia regions and investigate whether any may be young massive cluster progenitor gas clouds. HOPS is also ideally suited to trace the flows of dense gas in the Galactic Centre. We find the kinematic structure of gas within the inner 500 pc of the Galaxy is consistent with recent predictions for the dynamical evolution of gas flows in the centre of the Milky Way. We confirm a recent finding that the dense gas in the inner 100 pc has an oscillatory kinematic structure with characteristic length-scale of 20 pc, and also identify similar oscillatory kinematic structure in the gas at radii larger than 100 pc. Finally, we make all of the above fits and the remaining HOPS data cubes across the 100 deg 2 of the survey available to the community.

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The Molecular Gas Environment in the 20 km s⁻¹ Cloud in the Central Molecular Zone

Cited by 40 publications

References 81 publications

ATLASGAL-selected massive clumps in the inner Galaxy

ATLASGAL-selected massive clumps in the inner Galaxy

Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde

H2O Southern Galactic Plane Survey (HOPS): Paper III – properties of dense molecular gas across the inner Milky Way

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The Molecular Gas Environment in the 20 km s−1 Cloud in the Central Molecular Zone

Cited by 40 publications

References 81 publications

ATLASGAL-selected massive clumps in the inner Galaxy

ATLASGAL-selected massive clumps in the inner Galaxy

Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde

H2O Southern Galactic Plane Survey (HOPS): Paper III – properties of dense molecular gas across the inner Milky Way

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Product

Resources

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The Molecular Gas Environment in the 20 km s⁻¹ Cloud in the Central Molecular Zone