Dense gas in IRAS 20343+4129: an ultracompact H ii region caught in the act of creating a cavity

Fontani, F.; Palau, Aina; Busquet, G.; Isella, Andrea; Estalella, R.; Sánchez-Monge, Á.; Caselli, P.; Zhang, Qizhou

doi:10.1111/j.1365-2966.2012.20990.x

Cited by 18 publications

(15 citation statements)

References 52 publications

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“…The warm molecule C 2 H appears to be associated with L bol , as well as the c−C 3 H 2 6-5 and 5-4 transitions. Since these molecules are generally formed in irradiated regions (Fontani et al 2012;Jørgensen et al 2013;Nagy et al 2015;Guzmán et al 2015), the correlation between C 2 H and c−C 3 H 2 , and L bol can be explained by the outflow cavity being irradiated by the central protostar, as was also found for O[I] and H2O (e.g. Mottram et al 2017).…”

Section: Line Emission and System Parametersmentioning

confidence: 79%

“…The weak emission of DCN and the higher-lying transitions of H 2 CO would suggest that the envelope gas is relatively cold and currently not being strongly heated. The molecules c−C 3 H 2 and C 2 H trace the warm UV-irradiated gas (e.g., Nagy et al 2015;Guzmán et al 2015), most likely located along the outflow cavity (e.g., Fontani et al 2012;Jørgensen et al 2013;Murillo et al 2018). The peak intensities of c−C 3 H 2 vary by less than a factor of 3 among all three observed transitions.…”

Section: Cold and Warm Gasmentioning

confidence: 99%

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Role of environment and gas temperature in the formation of multiple protostellar systems: molecular tracers

Murillo

Dishoeck

Tobin

et al. 2018

A&A

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Context. Simulations suggest that gas heating due to radiative feedback is a key factor in whether or not multiple protostellar systems will form. Chemistry is a good tracer of the physical structure of a protostellar system, since it depends on the temperature structure. Aims. To study the relationship between envelope gas temperature and protostellar multiplicity. Methods. Single dish observations of various molecules that trace the cold, warm and UV-irradiated gas are used to probe the temperature structure of multiple and single protostellar systems on 7000 AU scales. Results. Single, close binary and wide multiples present similar current envelope gas temperatures, as estimated from H 2 CO and DCO + line ratios. The temperature of the outflow cavity, traced by c−C 3 H 2 , on the other hand, shows a relation with bolometric luminosity and an anti-correlation with envelope mass. Although the envelope gas temperatures are similar for all objects surveyed, wide multiples tend to exhibit a more massive reservoir of cold gas compared to close binary and single protostars. Conclusions. Although the sample of protostellar systems is small, the results suggest that gas temperature may not have a strong impact on fragmentation. We propose that mass, and density, may instead be key factors in fragmentation.

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Section: Line Emission and System Parametersmentioning

confidence: 79%

Section: Cold and Warm Gasmentioning

confidence: 99%

Role of environment and gas temperature in the formation of multiple protostellar systems: molecular tracers

Murillo

Dishoeck

Tobin

et al. 2018

A&A

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“…In high-mass star-forming regions, c−C 3 H 2 and C 2 H tend to be strongly correlated, with both lines presenting similar spatial distributions (Pilleri et al 2013;Mookerjea et al 2012Mookerjea et al , 2014. In contrast, toward IRAS 20343+4129, c−C 3 H 2 and C 2 H show an anti-correlation around the outflow cavity walls of IRS 1 (Fontani et al 2012) but not around the UC HII-region of IRS 3. The anti-correlation is explained to possibly be product of the gas density, with an enhancement of C 2 H located in the regions with denser gas.…”

Section: Comparison With Diffuse Clouds Pdrs and Intermediate To Higmentioning

confidence: 92%

Tracing the cold and warm physico-chemical structure of deeply embedded protostars: IRAS 16293−2422 vs. VLA 1623−2417

Murillo

Dishoeck

Wiel

et al. 2018

A&A

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Context. Much attention has been placed on the dust distribution in protostellar envelopes, but there are still many unanswered questions regarding the physico-chemical structure of the gas. Aims. Our aim is to start identifying the factors that determine the chemical structure of protostellar regions, by studying and comparing low-mass embedded systems in key molecular tracers. Methods. The cold and warm chemical structures of two embedded Class 0 systems, IRAS 16293-2422 and VLA 1623-2417 is characterized through interferometric observations. DCO + , N 2 H + and N 2 D + are used to trace the spatial distribution and physics of the cold regions of the envelope, while c−C 3 H 2 and C 2 H from models of the chemistry are expected to trace the warm (UV-irradiated) regions.Results. The two sources show a number of striking similarities and differences. DCO + consistently traces the cold material at the disk-envelope interface, where gas and dust temperatures are lowered due to disk shadowing. N 2 H + and N 2 D + , also tracing cold gas, show low abundances towards VLA 1623−2417, but for IRAS 16293−2422, the distribution of N 2 D + is consistent with the same chemical models that reproduce DCO + . c−C 3 H 2 and C 2 H show different spatial distributions for the two systems. For IRAS 16293−2422, c−C 3 H 2 traces the outflow cavity wall, while C 2 H is found in the envelope material but not the outflow cavity wall. In contrast, toward VLA 1623−2417 both molecules trace the outflow cavity wall. Finally, hot core molecules are abundantly observed toward IRAS 16293−2422 but not toward VLA 1623−2417.Conclusions. We identify temperature as one of the key factors in determining the chemical structure of protostars as seen in gaseous molecules. More luminous protostars, such as IRAS 16293-2422, will have chemical complexity out to larger distances than colder protostars, such as VLA 1623-2417. Additionally, disks in the embedded phase have a crucial role in controlling both the gas and dust temperature of the envelope, and consequently the chemical structure.

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“…2). We have identified the lines detected with signal-to-noise ratio > ∼ 5, which correspond to typical main beam temperatures ∼0.1 K. Most of the lines detected toward all the sources of the sample correspond to simple molecules such as N 2 H + , C 2 H, NH 2 D, or H 13 CN, which are typically found tracing the dense gas in YSOs (e.g., Tafalla et al 2004;Padovani et al 2011;Busquet et al 2011;Fontani et al 2012), and molecules such as SiO and HCO + typically used to trace the outflow emission (e.g., Tafalla et al 2010;López-Sepulcre et al 2010;Codella et al 2013). For twelve of the fourteen sources, we also detected CH 3 CN emission, which is a tracer typically found in association with hot cores (e.g., Olmi et al 1993Olmi et al , 1996Sánchez-Monge et al 2010.…”

Section: Molecular Line Emissionmentioning

confidence: 99%

Evolution and excitation conditions of outflows in high-mass star-forming regions

Sánchez-Monge

López-Sepulcre

Cesaroni

et al. 2013

A&A

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Context. Theoretical models suggest that massive stars form via disk-mediated accretion in a similar fashion to low-mass stars. In this scenario, bipolar outflows ejected along the disk axis play a fundamental role, and their study can help characterize the different evolutionary stages involved in the formation of a high-mass star. A recent study toward massive molecular outflows has revealed a decrease in the SiO line intensity as the object evolves. Aims. The present study aims to characterize the variation of the molecular outflow properties with time and to study the SiO excitation conditions in outflows associated with high-mass young stellar objects (YSOs). Methods. We used the IRAM 30-m telescope on Pico Veleta (Spain) to map 14 high-mass star-forming regions in the SiO (2-1), SiO (5-4), and HCO + (1-0) lines, which trace the molecular outflow emission. The FTS backend, covering a total frequency range of ∼15 GHz, allowed us to simultaneously map several dense gas (e.g., N 2 H + , C 2 H, NH 2 D, H 13 CN) and hot-core (CH 3 CN) tracers. We used the Hi-GAL data to improve the previous spectral energy distributions and obtained a more accurate dust envelope mass and bolometric luminosity for each source. We calculated the luminosity-to-mass ratio, which is believed to be a good indicator of the evolutionary stage of the YSO. Results. We detect SiO and HCO + outflow emission in all fourteen sources and bipolar structures in six of them. The outflow parameters are similar to those found toward other massive YSOs with luminosities 10 3 −10 4 L . We find an increase in the HCO + outflow energetics as the object evolves, and a decrease in the SiO abundance with time from 10 −8 to 10 −9 . The SiO (5-4) to (2-1) line ratio is found to be low at the ambient gas velocity, and increases as we move to red-/blue-shifted velocities, indicating that the excitation conditions of the SiO change with the velocity of the gas. In particular, the high-velocity SiO gas component seems to arise from regions with higher densities and/or temperatures than the SiO emission at the ambient gas velocity. Conclusions. The properties of the SiO and HCO + outflow emission suggest a scenario in which SiO is largely enhanced in the first evolutionary stages, probably owing to strong shocks produced by the protostellar jet. As the object evolves, the power of the jet would decrease and so does the SiO abundance. During this process, however, the material surrounding the protostar would have been been swept up by the jet, and the outflow activity, traced by entrained molecular material (HCO + ), would increase with time.

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Dense gas in IRAS 20343+4129: an ultracompact H ii region caught in the act of creating a cavity

Cited by 18 publications

References 52 publications

Role of environment and gas temperature in the formation of multiple protostellar systems: molecular tracers

Role of environment and gas temperature in the formation of multiple protostellar systems: molecular tracers

Tracing the cold and warm physico-chemical structure of deeply embedded protostars: IRAS 16293−2422 vs. VLA 1623−2417

Evolution and excitation conditions of outflows in high-mass star-forming regions

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