Dense gas and the nature of the outflows

Sepúlveda, Inma; Anglada, Guillem; Estalella, R.; López, R.; Girart, J. M.; Yang, Ji

doi:10.1051/0004-6361/200912916

Cited by 28 publications

(34 citation statements)

References 178 publications

(251 reference statements)

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“…The most intense emission in the central region of the 1.2‐mm dust continuum map is contained inside the HPBW of the low angular resolution NH 3 map of Sepúlveda et al (). The BIMA observations of MGE03 also only detected N 2 H + emission in a region almost coinciding with CL1/SMM5 (the other dust continuum sources lie outside the BIMA primary beam).…”

Section: Discussionmentioning

confidence: 94%

Probing the physical and chemical structure of the CS core in LDN 673: multitransitional and continuum observations

Morata

Girart

Estalella

et al. 2012

Monthly Notices of the Royal Astronomical Society

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High angular resolution observations of dense molecular cores show that these cores can be clumpier at smaller scales and that some of these clumps can also be unbound or transient. The use of chemical models of the evolution of the molecular gas provides a way to probe the physical properties of the clouds. We study the properties of the clump and interclump medium in the starless CS core in LDN 673 by carrying out a molecular line survey with the IRAM 30‐m telescope towards two clumps and two interclump positions. We also observed the 1.2‐mm continuum with the MAMBO‐II bolometer at IRAM. The dust continuum map shows four condensations, three of them centrally peaked, coinciding with previously identified submillimetre sources. We confirm that the denser clump of the region, n ∼ 3.6 × 105 cm−3, is also the more chemically evolved, and it could still undergo further fragmentation. The interclump medium positions are denser than previously expected, likely n ∼ 1 × 103–1 × 104 cm−3 due to contamination, and are chemically young, similar to the gas in the lower density clump position. We argue that the density contrast between these positions and their general young chemical age would support the existence of transient clumps in the lower density material of the core. We were also able to find reasonable fits of the observationally derived chemical abundances to models of the chemistry of transient clumps.

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Section: Discussionmentioning

confidence: 94%

Probing the physical and chemical structure of the CS core in LDN 673: multitransitional and continuum observations

Morata

Girart

Estalella

et al. 2012

Monthly Notices of the Royal Astronomical Society

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“…References. (1) Mardones et al (1997); (2) Tafalla et al (2004); (3) Marcaide et al (1988); (4) Wiseman et al (2001); (5) Choi et al (1999); (6) Sepúlveda et al (2011); (7) Bourke et al (1995); (8) Bjerkeli et al (2011); (9) Fuente et al (2005); (10) Lefloch et al (1996). These observations, from now on referred to as the "557 GHz" observations, were made initially in position-switching (PS) mode using a reference 10 or more away from the source. Experience within the WISH project, however, showed that dual beam switching (DBS) with a 3 chop produced flatter baselines than PS, and the observing mode was changed to DBS after the first set of data were obtained.…”

Section: Hifi Observations Of Hmentioning

confidence: 99%

High-pressure, low-abundance water in bipolar outflows

Tafalla

Liseau

Nisini

et al. 2013

A&A

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Context. Water is a potential tracer of outflow activity because it is heavily depleted in cold ambient gas and is copiously produced in shocks.Aims. We present a survey of the water emission in a sample of more than 20 outflows from low-mass young stellar objects with the goal of characterizing the physical and chemical conditions of the emitting gas. Methods. We used the HIFI and PACS instruments on board the Herschel Space Observatory to observe the two fundamental lines of ortho-water at 557 and 1670 GHz. These observations were part of the "Water In Star-forming regions with Herschel" (WISH) key program, and have been complemented with CO and H 2 data. Results. The emission of water has a different spatial and velocity distribution from that of the J = 1−0 and 2−1 transitions of CO. On the other hand, it has a similar spatial distribution to H 2 , and its intensity follows the H 2 intensity derived from IRAC images. This suggests that water traces the outflow gas at hundreds of kelvins that is responsible for the H 2 emission, and not the component at tens of kelvins typical of low-J CO emission. A warm origin of the water emission is confirmed by a remarkable correlation between the intensities of the 557 and 1670 GHz lines, which also indicates that the emitting gas has a narrow range of excitations. A radiative transfer analysis shows that while there is some ambiguity in the exact combination of density and temperature values, the gas thermal pressure nT is constrained within less than a factor of 2. The typical nT over the sample is 4×10 9 cm −3 K, which represents an increase of 10 4 with respect to the ambient value. The data also constrain the water column density within a factor of 2 and indicate values in the sample between 2 × 10 12 and 10 14 cm −2 . When these values are combined with estimates of the H 2 column density, the typical water abundance is only 3 × 10 −7 , with an uncertainty of a factor of 3. Conclusions. Our data challenge current C-shock models of water production through the combination of wing-line profiles, high gas compressions, and low abundances.

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“…Heavily destroyed in UV fields (e.g. Fuente et al 1990, and references therein), it is present in cold dark clouds (Jijina et al 1999;Sepúlveda et al 2011) and also in regions affected by shocks (Tafalla & Bachiller 1995;Zhang et al 2002;Palau et al 2007). Since the very beginnings of molecular spectroscopy, it has been widely recognized as an excellent thermometer of the ISM (Ho & Townes 1983;Guesten et al 1985;Maret et al 2009).…”

Section: Derivation Of Physical Parametersmentioning

confidence: 99%

Ammonia observations in the LBV nebula G79.29+0.46

Rizzo

Palau

Jiménez-Esteban

et al. 2014

A&A

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Context. The surroundings of luminous blue variable (LBV) stars are excellent laboratories to study the effects of their high UV radiation, powerful winds, and strong ejection events onto the surrounding gas and dust. Aims. We aim at determining the physical parameters of the dense gas near G79.29+0.46, an LBV-candidate located at the centre of two concentric infrared rings, which may interact with the infrared dark cloud (IRDC) G79.3+0.3. Methods. The Effelsberg 100 m telescope was used to observe the NH 3 (1, 1) and (2, 2) emission in a field of view of 7 × 7 including the infrared rings and a part of the IRDC. In addition, we observed particular positions in the NH 3 (3,3) transition toward the strongest region of the IRDC, which is also closest to the ring nebula. Results. We report here the first coherent ring-like structure of dense NH 3 gas associated with an evolved massive star. It is well traced in both ammonia lines, surrounding an already known infrared ring nebula; its column density is two orders of magnitude lower than the IRDC. The NH 3 emission in the IRDC is characterized by a low and uniform rotational temperature (T rot ∼10 K) and moderately high opacities in the (1, 1) line. The rest of the observed field is spotted by warm or hot zones (T rot >30 K) and characterized by optically thin emission of the (1, 1) line. The NH 3 abundances are about 10 −8 in the IRDC, and 10 −10 -10 −9 elsewhere. The warm temperatures and low abundances of NH 3 in the ring suggest that the gas is being heated and photo-dissociated by the intense UV field of the LBV star. An outstanding region is found to the south-west (SW) of the LBV star within the IRDC. The NH 3 (3, 3) emission at the centre of the SW region reveals two velocity components tracing gas at temperatures >30 K. Of particular interest is the northern edge of the SW region, which coincides with the border of the ring nebula and a region of strong 6 cm continuum emission; here, the opacity of the (1, 1) line and the NH 3 abundance do not decrease as expected in a typical clump of an isolated cold dark cloud. This strongly suggests some kind of interaction between the ring nebula (powered by the LBV star) and the IRDC. We finally discuss the possibility of NH 3 evaporation from the dust grain mantles due to the already known presence of low-velocity shocks in the area. Conclusions. The detection of the NH 3 associated with this LBV ring nebula, as well as the special characteristics of the northern border of the SW region, confirm that the surroundings of G79.29+0.46 constitute an exemplary scenario, which merits to be studied in detail by other molecular tracers and higher angular resolutions.

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Dense gas and the nature of the outflows

Cited by 28 publications

References 178 publications

Probing the physical and chemical structure of the CS core in LDN 673: multitransitional and continuum observations

Probing the physical and chemical structure of the CS core in LDN 673: multitransitional and continuum observations

High-pressure, low-abundance water in bipolar outflows

Ammonia observations in the LBV nebula G79.29+0.46

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