Complex molecule formation around massive young stellar objects

Öberg, Karin I.; Fayolle, Edith C.; Reiter, John B.; Cyganowski, C. J.

doi:10.1039/c3fd00146f

Cited by 22 publications

(15 citation statements)

References 38 publications

(56 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…CH 3 OH and CH 3 CN, the most spatially extended Oand N-bearing species, respectively, in our sample, possess similar spatial distributions and tight column density correlations across G10.6. This is surprising as prior observations of MYSO have reported a lack of correlation between these species (Bisschop et al 2007;Öberg et al 2014), and both molecules are thought to form via different mechanisms (Garrod & Herbst 2006;Garrod et al 2008). Indeed, in G10.6, we believe the observed correlation likely reflects that both species are tied to total gas column density, rather than intrinsic chemical similarity.…”

Section: Spatial Distribution Of N-versus O-bearing Speciescontrasting

confidence: 69%

Sub-arcsecond Imaging of the Complex Organic Chemistry in Massive Star-forming Region G10.6-0.4

Law,

Zhang,

Öberg

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

Massive star-forming regions exhibit an extremely rich and diverse chemistry, which in principle provides a wealth of molecular probes, as well as laboratories for interstellar prebiotic chemistry. Since the chemical structure of these sources displays substantial spatial variation among species on small scales ( 10 4 au), high angular resolution observations are needed to connect chemical structures to local environments and inform astrochemical models of massive star formation. To address this, we present ALMA 1.3 mm observations toward OB cluster-forming region G10.6-0.4 (hereafter "G10.6") at a resolution of 0.14 (700 au). We find highly-structured emission from complex organic molecules (COMs) throughout the central 20,000 au, including two hot molecular cores and several shells or filaments. We present spatially-resolved rotational temperature and column density maps for a large sample of COMs and warm gas tracers. These maps reveal a range of gas substructure in both O-and N-bearing species. We identify several spatial correlations that can be explained by existing models of COM formation, including NH 2 CHO/HNCO and CH 3 OCHO/CH 3 OCH 3 , but also observe unexpected distributions and correlations which suggest that our current understanding of COM formation is far from complete. Importantly, complex chemistry is observed throughout G10.6, rather than being confined to hot cores. The COM composition appears to be different in the cores compared to the more extended structures, which illustrates the importance of high spatial resolution observations of molecular gas in elucidating the physical and chemical processes associated with massive star formation.

show abstract

Section: Spatial Distribution Of N-versus O-bearing Speciescontrasting

confidence: 69%

Sub-arcsecond Imaging of the Complex Organic Chemistry in Massive Star-forming Region G10.6-0.4

Law,

Zhang,

Öberg

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…We observed a weak correlation of abundance of CH 3 CCH and bulk gas temperature, which is reminiscent of the small variation of the CH 3 CCH abundance toward massive clumps of various evolutionary stages reported by Giannetti et al (2017) (see also Öberg et al 2014). Other higher angular resolution observations of this species indicated a mixed behavior of its spatial distribution, depending on whether the emission coincides with the localized hot cores or appears offset and/or shows more extended structures (Bøgelund et al 2019, Öberg et al 2014, Fayolle et al 2015. Comparing rotational temperature maps of CH 3 CCH (12-11), the temperatures of G13 and G31 in the core region is 20-30 K higher than those of G19, G08a, and G08b.…”

Section: Molecular Abundance and Abundance Ratiosmentioning

confidence: 92%

“…They have been regarded as good tracers of hot molecular cores owing to the fact that they were mainly detected around significantly heated regions. On the other hand, CH 3 CCH has been detected in spatially more extended, lower temperature regions (e.g., Bergin et al 1994;Öberg et al 2014) and is therefore particularly advantageous for probing sources in relatively early evolutionary stages (Molinari et al 2016), prior to hot core formation. Giannetti et al (2017) showed that among the various thermometers the kinetic temperature constrained by CH 3 CCH is representative of gas temperatures of massive clumps.…”

Section: Distribution Of Emissionmentioning

confidence: 99%

The evolution of temperature and density structures of OB cluster-forming molecular clumps

Lin

Wyrowski

Liu

et al. 2022

A&A

View full text Add to dashboard Cite

Context. OB star clusters originate from parsec-scale massive molecular clumps, while individual stars may form in ≲0.1 pc scale dense cores. The thermal properties of the clump gas are key factors governing the fragmentation process, and are closely affected by gas dynamics and feedback of forming stars. Aims. We aim to understand the evolution of temperature and density structures on the intermediate-scale (≲0.1–1 pc) extended gas of massive clumps. This gas mass reservoir is critical for the formation of OB clusters, due to their extended inflow activities and intense thermal feedback during and after formation. Methods. We performed ~0.1 pc resolution observations of multiple molecular line tracers (e.g., CH3CCH, H2CS, CH3CN, CH3OH) that cover a wide range of excitation conditions, toward a sample of eight massive clumps. The sample covers different stages of evolution, and includes infrared-weak clumps and sources that are already hosting an HII region, spanning a wide luminosity-to-mass ratio (L∕M) range from ~1 to ~100 (L⊙/M⊙). Based on various radiative transfer models, we constrain the gas temperature and density structures and establish an evolutionary picture, aided by a spatially dependent virial analysis and abundance ratios of multiple species. Results. We determine temperature profiles varying in the range 30–200 K over a continuous scale, from the center of the clumps out to 0.3–0.4 pc radii. The clumps’ radial gas density profiles, described by radial power laws with slopes between −0.6 and ~−1.5, are steeper for more evolved sources, as suggested by results based on dust continuum, representing the bulk of the gas (~104 cm−3), and on CH3OH lines probing the dense gas (≳106–108 cm−3) regime. The density contrast between the dense gas and the bulk gas increases with evolution, and may be indicative of spatially and temporally varying star formation efficiencies. The radial profiles of the virial parameter show a global variation toward a sub-virial state as the clump evolves. The linewidths probed by multiple tracers decline with increasing radius around the central core region and increase in the outer envelope, with a slope shallower than the case of the supersonic turbulence (σv ∝ r0.5) and the subsonic Kolmogorov scaling (σv ∝ r0.33). In the context of evolutionary indicators for massive clumps, we also find that the abundance ratios of [CCH]/[CH3OH] and [CH3CN]/[CH3OH] show correlations with clump L∕M.

show abstract

“…COMs have also been detected in the lukewarm envelopes of several low-mass and high-mass protostars. The COM excitation temperatures in these sources are well below the expected ice sublimation temperature of ∼100 K. 41,[57][58][59][60] COMs are thus present in protostellar gas prior to the onset of thermal ice sublimation. The protostellar envelopes where these COMs are detected are generally warm enough for diffusion-limited COM formation to be efficient in ices.…”

Section: Complex Organic Molecules During Star Formationmentioning

confidence: 99%

Photochemistry and Astrochemistry: Photochemical Pathways to Interstellar Complex Organic Molecules

2016

Self Cite

View full text Add to dashboard Cite

The interstellar medium is characterized by a rich and diverse chemistry. Many of its complex organic molecules are proposed to form through radical chemistry in icy grain mantles.Radicals form readily when interstellar ices (composed of water and other volatiles) are exposed to UV photons and other sources of dissociative radiation, and if sufficiently mobile the radicals can react to form larger, more complex molecules. The resulting complex organic molecules (COMs) accompany star and planet formation, and may eventually seed the origins of life on nascent planets. Experiments of increasing sophistication have demonstrated that known interstellar COMs as well as the prebiotically interesting amino acids can form through ice photochemistry. We review these experiments and discuss the qualitative and quantitative kinetic and mechanistic constraints they have provided. We finally compare the effects of UV radiation with those of three other potential sources of radical production and chemistry in interstellar ices: electrons, ions and X-rays.

show abstract

Complex molecule formation around massive young stellar objects

Cited by 22 publications

References 38 publications

Sub-arcsecond Imaging of the Complex Organic Chemistry in Massive Star-forming Region G10.6-0.4

Sub-arcsecond Imaging of the Complex Organic Chemistry in Massive Star-forming Region G10.6-0.4

The evolution of temperature and density structures of OB cluster-forming molecular clumps

Photochemistry and Astrochemistry: Photochemical Pathways to Interstellar Complex Organic Molecules

Contact Info

Product

Resources

About