Atlas of Main-line OH Masers in the Galactic Longitude Range 3° to 60°

Caswell, J. L.; Haynes, R. F.

doi:10.1071/ph830417b

Cited by 45 publications

(55 citation statements)

References 3 publications

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“…OH masers were reported in the main 1.665 and 1.667 GHz, and the satellite 1.720 GHz lines (Caswell & Haynes 1983;Edris et al 2007), whereas the 1.612 GHz OH satellite was observed in absorption. CH 3 OH thermal lines were observed at 25, 96.7, 157, 241.7, and 255 GHz by Leurini et al (2007), and maser emission was reported for the Class II 6.7 GHz (Menten 1991;Caswell et al 1995b;Szymczak et al 2000) and 12.2 GHz (Caswell et al 1995a), and the Class I 44.1 GHz (Slysh et al 1994) and95.2 GHz (Val'tts et al 2000) transitions.…”

Section: The Hmsfr G1659-005mentioning

confidence: 99%

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

Sanna

Moscadelli

Cesaroni

et al. 2010

A&A

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Aims. To study the high-mass star-forming process, we started a large project to unveil the gas kinematics close to young stellar objects (YSOs) through the Very Long Baseline Interferometry (VLBI) of maser associations. By comparing the high spatial resolution maser data that traces the inner kinematics of the (proto)stellar cocoon with interferometric thermal data that traces the large-scale environment of the hot molecular core (HMC) harboring the (proto)stars, we can investigate the nature and identify the sources of large-scale motions. The present paper focuses on the high-mass star-forming region G16.59-0.05. Methods. Using the VLBA and the EVN arrays, we conducted phase-referenced observations of the three most powerful maser species in G16.59-0.05: 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 starforming region at 1.3 and 3.6 cm.Results. This is the first work to report accurate measurements of the relative proper motions of the 6.7 GHz CH 3 OH masers. The different spatial and 3-D velocity distributions clearly indicate that the 22 GHz water and 6.7 GHz methanol masers trace different kinematic environments. The bipolar distribution of 6.7 GHz maser line-of-sight velocities and the regular pattern of observed proper motions suggest that these masers are tracing rotation around a central mass of about 35 M . The flattened spatial distribution of the 6.7 GHz masers, oriented NW−SE, suggests that they can originate in a disk/toroid rotating around the massive YSO that drives the 12 CO (2−1) outflow, oriented NE−SW, observed on an arcsec scale. The extended, radio continuum source observed close to the 6.7 GHz masers could be excited by a wide-angle wind emitted from the YSO associated with the methanol masers, and such a wind has proven to be energetic enough to drive the NE−SW 12 CO (2−1) outflow. The H 2 O masers are distributed across a region offset about 0. 5 to the NW of the CH 3 OH masers, in the same area as where the emission of high-density molecular tracers, typical of HMCs, was detected. We postulate that a distinct YSO, possibly in an earlier evolutionary phase than what excites the methanol masers, is responsible for the excitation of the water masers and the HMC molecular lines.

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Section: The Hmsfr G1659-005mentioning

confidence: 99%

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

Sanna

Moscadelli

Cesaroni

et al. 2010

A&A

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“…OH masers (e.g., Caswell & Haynes 1983;Szymczak & Gérard 2004). Through Zeeman splitting of the 1.667 GHz maser components, Szymczak & Gérard (2004) estimated a magnetic field strength of a few tenths of mG. Interestingly, in the spectra of the 1.665, 1.667, and 1.720 GHz OH transitions, absorption features were also noted (Caswell & Haynes 1983;Szymczak & Gérard 2004).…”

Section: The Hmsfr G2301-041mentioning

confidence: 99%

“…Through Zeeman splitting of the 1.667 GHz maser components, Szymczak & Gérard (2004) estimated a magnetic field strength of a few tenths of mG. Interestingly, in the spectra of the 1.665, 1.667, and 1.720 GHz OH transitions, absorption features were also noted (Caswell & Haynes 1983;Szymczak & Gérard 2004). A similar absorption pattern was observed in the 4.8 GHz H 2 CO transition by Downes et al (1980), who associated G23.01−0.41 to a nearby diffuse H ii region, identified through the H110α recombination line emission.…”

Section: The Hmsfr G2301-041mentioning

confidence: 99%

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

Sanna

Moscadelli

Cesaroni

et al. 2010

A&A

View full text Add to dashboard Cite

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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“…Introduction Caswell and Haynes (1983, present issue p. 419) recently made a compilation of all known OH masers that emit predominantly on the main-line transitions (1665 or 1667 MHz) of the ground state and are located in the galactic plane between longitude 3° and 60°. In April 1982 we conducted a search for associated H20 maser emission in the direction of those OH sources which are either new or now have greatly improved position estimates (Caswell and Haynes 1983). We used the Parkes 64 m radio telescope equipped with a new 22 GHz maser receiver and a 1024-channel correlator.…”

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confidence: 99%