Physical and chemical complexity in high-mass star-forming regions with ALMA

Gieser, C.; Beuther, H.; Semenov, D.; Ahmadi, A.; Henning, Th.; Wells, M. R. A.

doi:10.1051/0004-6361/202245249

Cited by 4 publications

(1 citation statement)

References 124 publications

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“…We have analyzed the ALMA Band 3 data toward five HMPOs. 15 Details of the observations of this project are described in Gieser et al (2023). Details about the five target sources and molecular lines presented in this paper are summarized in Tables 1 and 2, respectively.…”

Section: Data Reductionmentioning

confidence: 99%

Chemical Differentiation around Five Massive Protostars Revealed by ALMA: Carbon-chain Species and Oxygen/Nitrogen-bearing Complex Organic Molecules

Taniguchi

Majumdar

Caselli

et al. 2023

ApJS

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We present Atacama Large Millimeter/submillimeter Array Band 3 data toward five massive young stellar objects (MYSOs), and investigate relationships between unsaturated carbon-chain species and saturated complex organic molecules (COMs). An HC5N (J = 35–34) line has been detected from three MYSOs, where nitrogen (N)-bearing COMs (CH2CHCN and CH3CH2CN) have been detected. The HC5N spatial distributions show compact features and match with a methanol (CH3OH) line with an upper-state energy around 300 K, which should trace hot cores. The hot regions are more extended around the MYSOs where N-bearing COMs and HC5N have been detected compared to two MYSOs without these molecular lines, while there are no clear differences in the bolometric luminosity and temperature. We run chemical simulations of hot-core models with a warm-up stage, and compare with the observational results. The observed abundances of HC5N and COMs show good agreements with the model at the hot-core stage with temperatures above 160 K. These results indicate that carbon-chain chemistry around the MYSOs cannot be reproduced by warm carbon-chain chemistry, and a new type of carbon-chain chemistry occurs in hot regions around MYSOs.

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Section: Data Reductionmentioning

confidence: 99%

Chemical Differentiation around Five Massive Protostars Revealed by ALMA: Carbon-chain Species and Oxygen/Nitrogen-bearing Complex Organic Molecules

Taniguchi

Majumdar

Caselli

et al. 2023

ApJS

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Density distributions, magnetic field structures, and fragmentation in high-mass star formation

Beuther,

Gieser,

Soler

et al. 2024

A&A

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The fragmentation of high-mass star-forming regions depends on a variety of physical parameters, including density, the magnetic field, and turbulent gas properties. We evaluate the importance of the density and magnetic field structures in relation to the fragmentation properties during high-mass star formation. Observing the large parsec-scale Stokes $I$ millimeter dust continuum emission with the IRAM 30\,m telescope and the intermediate-scale ($<$0.1\,pc) polarized submillimeter dust emission with the Submillimeter Array toward a sample of 20 high-mass star-forming regions allows us to quantify the dependence of the fragmentation behavior of these regions on the density and magnetic field structures. Based on the IRAM\,30\,m data, we infer density distributions $n -p $ of the regions with typical power-law slopes $p$ around sim 1.5. There is no obvious correlation between the power-law slopes of the density structures on larger clump scales (sim 1\,pc) and the number of fragments on smaller core scales ($<$0.1\,pc). Comparing the large-scale single-dish density profiles to those derived earlier from interferometric observations at smaller spatial scales, we find that the smaller-scale power-law slopes are steeper, typically around sim 2.0. The flattening toward larger scales is consistent with the star-forming regions being embedded in larger cloud structures that do not decrease in density away from a particular core. The magnetic fields of several regions appear to be aligned with filamentary structures that lead toward the densest central cores. Furthermore, we find different polarization structures; some regions exhibit central polarization holes, whereas other regions show polarized emission also toward the central peak positions. Nevertheless, the polarized intensities are inversely related to the Stokes $I$ intensities, following roughly a power-law slope of $ We estimate magnetic field strengths between sim 0.2 and sim 4.5\,mG, and we find no clear correlation between magnetic field strength and the fragmentation level of the regions. A comparison of the turbulent to magnetic energies shows that they are of roughly equal importance in this sample. The mass-to-flux ratios range between sim 2 and sim 7, consistent with collapsing star-forming regions. Finding no clear correlations between the present-day large-scale density structure, the magnetic field strength, and the smaller-scale fragmentation properties of the regions, indicates that the fragmentation of high-mass star-forming regions may not be affected strongly by the initial density profiles and magnetic field properties. However, considering the limited evolutionary range and spatial scales of the presented CORE analysis, future research directions should include density structure analysis of younger regions that better resemble the initial conditions, as well as connecting the observed intermediate-scale magnetic field structure with the larger-scale magnetic fields of the parental molecular clouds.

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

Zhao,

Tang,

Henkel

et al. 2024

A&A

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The kinetic temperature structure of the massive filament DR21 within the Cygnus X molecular cloud complex has been mapped using the IRAM\,30\,m telescope. This mapping employed the para-H$_2$CO triplet K_aK_c $, and 3$_ $) on a scale of sim 0.1\,pc. By modeling the averaged line ratios of $ and 3$_ $ with RADEX under non local thermodynamic equilibrium (LTE) assumptions, the kinetic temperature of the dense gas was derived, which ranges from 24 to 114\,K, with an average temperature of 48.3\,pm \,0.5\,K at a density of $. In comparison to temperature measurements using NH$_3$\,(1,1)/(2,2) and far-infrared (FIR) wavelengths, the para-H$_2$CO\,(3--2) lines reveal significantly higher temperatures. The dense clumps in various regions appear to correlate with the notable kinetic temperature kin $\,gtrsim \,50\,K) of the dense gas traced by H$_2$CO. Conversely, the outskirts of the DR21 filament display lower temperature distributions kin $\,$<$\,50\,K). Among the four dense cores (N44, N46, N48, and N54), temperature gradients are observed on a scale of sim 0.1-0.3\,pc. This suggests that the warm dense gas traced by H$_2$CO is influenced by internal star formation activity. With the exception of the dense core N54, the temperature profiles of these cores were fitted with power-law indices ranging from $-$0.3 to $-$0.5, with a mean value of approximately $-$0.4. This indicates that the warm dense gas probed by H$_2$CO is heated by radiation emitted from internally embedded protostar(s) and/or clusters. While there is no direct evidence supporting the idea that the dense gas is heated by shocks resulting from a past explosive event in the DR21 region on a scale of sim 0.1\,pc, our measurements of H$_2$CO toward the DR21W1 region provide compelling evidence that the dense gas in this specific area is indeed heated by shocks originating from the western DR21 flow. Higher temperatures as traced by H$_2$CO appear to be associated with turbulence on a scale of sim 0.1\,pc. The physical parameters of the dense gas as determined from H$_2$CO lines in the DR21 filament exhibit a remarkable similarity to the results obtained in OMC-1 and N113, albeit on a scale of approximately 0.1-0.4\,pc. This may imply that the physical mechanisms governing the dynamics and thermodynamics of dense gas traced by $CO in diverse star formation regions may be dominated by common underlying principles despite variations in specific environmental conditions.

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Physical and chemical complexity in high-mass star-forming regions with ALMA

Cited by 4 publications

References 124 publications

Chemical Differentiation around Five Massive Protostars Revealed by ALMA: Carbon-chain Species and Oxygen/Nitrogen-bearing Complex Organic Molecules

Chemical Differentiation around Five Massive Protostars Revealed by ALMA: Carbon-chain Species and Oxygen/Nitrogen-bearing Complex Organic Molecules

Density distributions, magnetic field structures, and fragmentation in high-mass star formation

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

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