Methanol masers at 12 GHz

Caswell, J. L.; Gardner, F. F.; Norris, R. P.; Wellington, K. J.; McCutcheon, W. H.; Peng, R.

doi:10.1093/mnras/260.2.425

Cited by 37 publications

(74 citation statements)

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“…OH and H 2 O maser was reported by Braz et al (1989). A methanol maser has been detected by Caswell et al (1993) at a peak velocity of V CH 3 OH = 11.9 km s −1 , close to the cloud systemic velocity of V cl = 16.8 km s −1 (see also MacLeod & Gaylard 1992). Radio emission at 3 and 6 cm with flux density of 32.4 and 149 mJy, respectively, has been detected by Thompson et al (2004) in correspondence of the optical rim.…”

Section: Brc 68 Sfo 68 Iras 11332-6258 G2945-016mentioning

confidence: 67%

H₂O maser emission from bright rimmed clouds in the southern hemisphere

Valdettaro¹,

Chapman

Lovell

et al. 2007

A&A

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Context. Water maser emission is a powerful tracer of the presence of embedded sources in dense clouds since it requires elevated temperatures (>100 K) and densities (>10 7 cm −3 ) that can be found in circumstellar disks and/or jets/outflows associated with Young Stellar Objects. Bright rimmed clouds compressed by ionization fronts from nearby massive stars are considered good examples of externally triggered star formation, possibly resulting in the formation of massive stars. Aims. We aim to determine the water maser emission frequency and characteristics of 45 bright rimmed clouds in the southern hemisphere identified by Sugitani & Ogura (1994, ApJS, 92, 163). Methods. We have used the Tidbinbilla 70-m radiotelescope to perform a high sensitivity survey at 22.2 GHz of the maser emission from the 6 16 −5 23 rotational transition of H 2 O molecules. Results. We found 7 water maser sources out of 44 (16% detection rate), 5 being new detections. With the exception of the maser associated with BRC 68, all the other maser are characterized by low integrated fluxes and luminosities. Conclusions. Most maser sources fall below the correlation between the H 2 O and far-infrared luminosity found in other studies towards a variety of star forming regions. These results are similar to those found in the companion survey of BRCs in the northern hemisphere by Valdettaro et al. (2005, A&A, 443, 535). The low detection frequency and the properties of water maser emission from BRCs indicate that low-mass star formation is the most natural outcome of the external compression induced by the ionization front from nearby massive stars.

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Section: Brc 68 Sfo 68 Iras 11332-6258 G2945-016mentioning

confidence: 67%

H₂O maser emission from bright rimmed clouds in the southern hemisphere

Valdettaro¹,

Chapman

Lovell

et al. 2007

A&A

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“…Caswell et al (2000) detected thermal CH 3 OH emission from the 156.6 GHz (see also Slysh et al 1999) and 107.0 GHz transitions, this latter superimposed on a maser component. Methanol maser emission was also reported at 6.7 GHz (e.g., Menten 1991;Goedhart et al 2004), 12.2 GHz (e.g., Caswell et al 1993;Błaszkiewicz & Kus 2004), 44.1 GHz (Slysh et al 1994), and 95.2 GHz (Val'tts et al 2000). First attempts to measure Zeeman splitting of the 6.7 GHz maser components suggest a magnetic field strength of a few tens of mG (Vlemmings 2008).…”

Section: The Hmsfr G2301-041mentioning

confidence: 96%

VLBI study of maser kinematics in high-mass star-forming regions

Sanna

Moscadelli

Cesaroni

et al. 2010

A&A

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Aims. We performed a detailed study of maser and radio continuum emission toward the high-mass star-forming region G23.01−0.41. This study aims at improving our knowledge of the high-mass star-forming process by comparing the gas kinematics near a newly born young stellar object (YSO), analyzed through high spatial resolution maser data, with the large-scale environment of its native hot molecular core (HMC), identified in previous interferometric observations of thermal continuum and molecular lines. Methods. Using the VLBA and the EVN arrays, we conducted phase-referenced observations of the three most powerful maser species in G23.01−0.41: H 2 O at 22.2 GHz (4 epochs), CH 3 OH at 6.7 GHz (3 epochs), and OH at 1.665 GHz (1 epoch). In addition, we performed high-resolution (≥0. 1), high-sensitivity (<0.1 mJy) VLA observations of the radio continuum emission from the HMC at 1.3 and 3.6 cm. Results. We have detected H 2 O, CH 3 OH, and OH maser emission clustered within 2000 AU from the center of a flattened HMC, oriented SE-NW, from which emerges a massive 12 CO outflow, elongated NE-SW, extended up to the pc-scale. Although the three maser species show a clearly different spatial and velocity distribution and sample distinct environments around the massive YSO, the spatial symmetry and velocity field of each maser specie can be explained in terms of expansion from a common center, which possibly denotes the position of the YSO driving the maser motion. Water masers trace both a fast shock (up to 50 km s −1 ) closer to the YSO, powered by a wide-angle wind, and a slower (20 km s −1 ) bipolar jet, at the base of the large-scale outflow. Because the compact free-free emission is found offset from the putative location of the YSO along a direction consistent with that of the maser jet axis, we interpret the radio continuum in terms of a thermal jet. The velocity field of methanol masers can be explained in terms of a composition of slow (4 km s −1 in amplitude) motions of radial expansion and rotation about an axis approximately parallel to the maser jet. Finally, the distribution of line-of-sight velocities of the hydroxyl masers suggests that they can trace gas less dense (n H 2 ≤ 10 6 cm −3 ) and more distant from the YSO than that traced by the water and methanol masers, which is expanding toward the observer. A few pairs of OH masers, with different circular polarization, are well aligned in position on the sky and we interpret them as Zeeman pairs. From Zeeman splitting, the derived typical values of the magnetic field are of a few mG.

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“…Methyl alcohol or methanol (CH 3 OH), the simplest alcohol, is one of the most abundant molecules detected toward various astrophysical regions, including hot molecular cores (HMCs) associated with low-and high-mass star-forming regions (Requena-Torres et al 2006;Remijan et al 2004;Pei et al 2000;De Buizer et al 2000;Menten 1991;Norris et al 1993;Caswell et al 1993, and references therein); dense molecular clouds (Irvine et al 1987;Tielens & Alamandola 1987), circumstellar and proto-stellar regions (Schutte et al 1999;Keane et al 2001;Goldsmith et al 1999;Pontoppidan et al 2003Pontoppidan et al , 2004Grim et al 1991) and in comets (Mumma et al 2001;BockeleeMorvan et al 1994;Crovisier & Bockelée-Morvan 1999, and references therein). In these objects, the radiation field can drive several photophysical and photochemical processes, including molecular photodissociation.…”

Section: Introductionmentioning

confidence: 99%

Photodissociation of organic molecules in star-forming regions

Pilling

Neves

Santos

et al. 2006

A&A

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The presence of methyl alcohol or methanol (CH 3 OH) in several astrophysical environments has been characterized by its high abundance that depends on both the production rate and the destruction rate. In the present work, the photoionization and photodissociation processes of methanol have been experimentally studied, employing soft X-ray photons (100-310 eV) from a toroidal grating monochromator (TGM) beamline of the Brazilian Synchrotron Light Laboratory (LNLS). Mass spectra were obtained using the photoelectron photoion coincidence (PEPICO) method. Kinetic energy distribution and abundances for each ionic fragment have been obtained from the analysis of the corresponding peak shapes in the mass spectra. Absolute photoionization and photodissociation cross sections were also determined. We have found, among the channels leading to ionization, about 11-16% of CH 3 OH survive the soft X-rays photons. This behavior, together with an efficient formation pathways, may be associated with the high column density observed in star-forming regions. The three main photodissociation pathways are represented by COH + (or HCO + ) ion release (with ejection of H 2 + H), the dissociation via C-O bond rupture (with strong charge retention preferentially on the methyl fragment) and the ejection of a single energetic (2-4 eV) proton. Since methanol is very abundant in star forming regions, the produced protons could be an alternative route to molecular hydrogenation or a trigger for secondary dissociation processes or even to promote extra heating of the environment.

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Methanol masers at 12 GHz

Cited by 37 publications

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H₂O maser emission from bright rimmed clouds in the southern hemisphere

H₂O maser emission from bright rimmed clouds in the southern hemisphere

VLBI study of maser kinematics in high-mass star-forming regions

Photodissociation of organic molecules in star-forming regions

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Methanol masers at 12 GHz

Cited by 37 publications

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H2O maser emission from bright rimmed clouds in the southern hemisphere

H2O maser emission from bright rimmed clouds in the southern hemisphere

VLBI study of maser kinematics in high-mass star-forming regions

Photodissociation of organic molecules in star-forming regions

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H₂O maser emission from bright rimmed clouds in the southern hemisphere

H₂O maser emission from bright rimmed clouds in the southern hemisphere