The Arecibo Methanol Maser Galactic Plane Survey. Iv. Accurate Astrometry and Source Morphologies

Pandian, J. D.; Momjian, Emmanuel; Xu, Ye; Menten, K. M.; Goldsmith, Paul F.

doi:10.1088/0004-637x/730/1/55

Cited by 43 publications

(98 citation statements)

References 33 publications

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“…a halo structure that surrounds the core of the masers. Moreover, if the maser spots do not have a compact core, they would not be detected in the EVN observations (Pandian et al 2011). Although in our observations the EVN resolves out about 50% of the flux of group C (V lsr > −61 km s −1 ), the majority of the flux appears to be recovered across the entire CH 3 OH maser spectrum.…”

Section: Discussionmentioning

confidence: 51%

“…This slight difference can be explained by the different resolution of the two instruments and flux calibration uncertainties in the Effelsberg observations (∼10%, Vlemmings 2008). This means that no significant changes occurred between the two epochs and there is no indication of a core/halo structure of the maser features (hereafter simply called masers) at scales of ∼100 AU such as described for a sample of CH 3 OH maser sources by Pandian et al (2011).…”

Section: Discussionmentioning

confidence: 97%

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The properties and polarization of the H₂O and CH₃OH maser environment of NGC 7538-IRS 1

Surcis

Vlemmings

Torres

et al. 2011

A&A

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Context. NGC 7538 is a complex massive star-forming region. The region is composed of several radio continuum sources, one of which is IRS 1, a high-mass protostar, from which a 0.3 pc molecular bipolar outflow was detected. Several maser species have been detected around IRS 1. The CH 3 OH masers have been suggested to trace a Keplerian-disk, while the H 2 O masers are almost aligned to the outflow. More recent results suggested that the region hosts a torus and potentially a disk, but with a different inclination than the Keplerian-disk that is supposed to be traced by the CH 3 OH masers. Aims. Tracing the magnetic field close to protostars is fundamental for determining the orientation of the disk/torus. Recent studies showed that during the protostellar phase of high-mass star formation the magnetic field is oriented along the outflows and around or on the surfaces of the disk/torus. The observations of polarized maser emissions at milliarcsecond resolution can make a crucial contribution to understanding the orientation of the magnetic field and, consequently, the orientation of the disk/torus in NGC 7538-IRS 1. Methods. The NRAO Very Long Baseline Array was used to measure the linear polarization and the Zeeman-splitting of the 22 GHz H 2 O masers toward NGC 7538-IRS 1. The European VLBI Network and the MERLIN telescopes were used to measure the linear polarization and the Zeeman-splitting of the 6.7 GHz CH 3 OH masers toward the same region. Results. We detected 17 H 2 O masers and 49 CH 3 OH masers at high angular resolution. We detected linear polarization emission toward two H 2 O masers and toward twenty CH 3 OH masers. The CH 3 OH masers, most of which only show a core structure, seem to trace rotating and potentially infalling gas in the inner part of a torus. Significant Zeeman-splitting was measured in three CH 3 OH masers. No significant (3σ) magnetic field strength was measured using the H 2 O masers. We also propose a new description of the structure of the NGC 7538-IRS 1 maser region.

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Section: Discussionmentioning

confidence: 51%

Section: Discussionmentioning

confidence: 97%

The properties and polarization of the H₂O and CH₃OH maser environment of NGC 7538-IRS 1

Surcis

Vlemmings

Torres

et al. 2011

A&A

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“…VLBI observations of G45.473+0.134 in March 2010 have shown that the maser emission comes from three clusters . No significant changes in morphology were seen as compared with the maps obtained in 2007 with MER-LIN (Pandian et al 2011). Comparison of the spectra taken with the 32 m telescope and VLBI indicates that less than 15 per cent of the flux density was missed in the VLBI observation figure A1), thus the source morphology is accurately recovered.…”

Section: Size Of Maser Region Showing Periodic Variabilitymentioning

confidence: 76%

Discovery of four periodic methanol masers and updated light curve for a further one

Szymczak

Wolak

Bartkiewicz

2015

Monthly Notices of the Royal Astronomical Society

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We report the discovery of 6.7 GHz methanol maser periodic flares in four massive star forming regions and the updated light curve for the known periodic source G22.357+0.066. The observations were carried out with the Torun 32 m radio telescope between June 2009 and April 2014. Flux density variations with period of 120 to 245 d were detected for some or all spectral features. A variability pattern with a fast rise and relatively slow fall on time-scale of 30−60 d dominated. A reverse pattern was observed for some features of G22.357+0.066, while sinusoidal-like variations were detected in G25.411+0.105. A weak burst lasting ∼520 d with the velocity drift of 0.24 km s −1 yr −1 occurred in G22.357+0.066. For three sources for which high resolution maps are available, we found that the features with periodic behaviour are separated by more than 500 au from those without any periodicity. This suggests that the maser flares are not triggered by large-scale homogeneous variations in either the background seed photon flux or the luminosity of the exciting source and a mechanism which is able to produce local changes in the pumping conditions is required.

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“…We plot the distribution of young stellar objects (YSOs as dotted black curve) from the RMS survey (Hoare et al 2005), CH 3 OH masers from Pandian et al (2011), Szymczak et al (2002), and Caswell et al (2010 (dashed and dashed-dotted curves) and the ATLASGAL sample as a solid curve in green in the middle panel. The YSOs are MSX sources (Price et al 2001), which emit at infrared wavelengths and are therefore in a more evolved phase than the IRDCs.…”

Section: Temperature and Linewidth Distributions In Different Evolutimentioning

confidence: 99%

Ammonia from cold high-mass clumps discovered in the inner Galactic disk by the ATLASGAL survey

Wienen

Wyrowski

Schüller

et al. 2012

A&A

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220

368

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Context. The APEX Telescope Large Area Survey: the GALaxy (ATLASGAL) is an unbiased continuum survey of the inner Galactic disk at 870 μm. It covers ±60 • in Galactic longitude and aims to find all massive clumps at various stages of high-mass star formation in the inner Galaxy, particularly the earliest evolutionary phases. Aims. We aim to determine properties such as the gas kinetic temperature and dynamics of new massive cold clumps found by ATLASGAL. Most importantly, we derived their kinematical distances from the measured line velocities. Methods. We observed the ammonia (J, K) = (1, 1) to (3, 3) inversion transitions toward 862 clumps of a flux-limited sample of submm clumps detected by ATLASGAL and extracted 13 CO (1−0) spectra from the Galactic Ring Survey (GRS). We determined distances for a subsample located at the tangential points (71 sources) and for 277 clumps whose near/far distance ambiguity is resolved. Results. Most ATLASGAL clumps are cold with rotational temperatures from 10−30 K with a median of 17 K. They have a wide range of NH 3 linewidths (1−7 km s −1 ) with 1.9 km s −1 as median, which by far exceeds the thermal linewidth, as well as a broad distribution of high column densities from 10 14 to 10 16 cm −2 (median of 2 × 10 15 cm −2 ) with an NH 3 abundance in the range of 5 to 30 × 10 −8 . ATLASGAL sources are massive, > ∼ 100 M , and a fraction of clumps with a broad linewidth is in virial equilibrium. We found an enhancement of clumps at Galactocentric radii of 4.5 and 6 kpc. The comparison of the NH 3 lines as high-density probes with the GRS 13 CO emission as low-density envelope tracer yields broader linewidths for 13 CO than for NH 3 . The small differences in derived clump velocities between NH 3 (representing dense core material) and 13 CO (representing more diffuse molecular cloud gas) suggests that the cores are essentially at rest relative to the surrounding giant molecular cloud. Conclusions. The high detection rate (87%) confirms ammonia as an excellent probe of the molecular content of the massive, cold clumps revealed by ATLASGAL. A clear trend of increasing rotational temperatures and linewidths with evolutionary stage is seen for source samples ranging from 24 μm dark clumps to clumps with embedded HII regions. The survey provides the largest ammonia sample of high-mass star forming clumps and thus presents an important repository for the characterization of statistical properties of the clumps and the selection of subsamples for detailed, high-resolution follow-up studies.

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The Arecibo Methanol Maser Galactic Plane Survey. Iv. Accurate Astrometry and Source Morphologies

Cited by 43 publications

References 33 publications

The properties and polarization of the H₂O and CH₃OH maser environment of NGC 7538-IRS 1

The properties and polarization of the H₂O and CH₃OH maser environment of NGC 7538-IRS 1

Discovery of four periodic methanol masers and updated light curve for a further one

Ammonia from cold high-mass clumps discovered in the inner Galactic disk by the ATLASGAL survey

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The Arecibo Methanol Maser Galactic Plane Survey. Iv. Accurate Astrometry and Source Morphologies

Cited by 43 publications

References 33 publications

The properties and polarization of the H2O and CH3OH maser environment of NGC 7538-IRS 1

The properties and polarization of the H2O and CH3OH maser environment of NGC 7538-IRS 1

Discovery of four periodic methanol masers and updated light curve for a further one

Ammonia from cold high-mass clumps discovered in the inner Galactic disk by the ATLASGAL survey

Contact Info

Product

Resources

About

The properties and polarization of the H₂O and CH₃OH maser environment of NGC 7538-IRS 1

The properties and polarization of the H₂O and CH₃OH maser environment of NGC 7538-IRS 1