FIRST PARALLAX MEASUREMENTS TOWARD A 6.7 GHz METHANOL MASER WITH THE AUSTRALIAN LONG BASELINE ARRAY—DISTANCE TO G 339.884−1.259.

Krishnan, V.; Ellingsen, S. P.; Reid, M. J.; Brunthaler, A.; Sanna, A.; McCallum, J.; Reynolds, C.; Bignall, Hayley; Phillips, Chris; Dodson, Richard; Rioja, María J.; Caswell, J. L.; Chen, X.; Dawson, J. R.; Fujisawa, Kenta; Goedhart, S.; Green, James; Hachisuka, Kazuya; Honma, Mareki; Menten, K. M.; Shen, Zhi-Qiang; Voronkov, M. A.; Walsh, A. J.; Xu, Ye; Zhang, B.; Zheng, Xingwu

doi:10.1088/0004-637x/805/2/129

Cited by 33 publications

(18 citation statements)

References 79 publications

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“…Southern arrays -like the Australian Long Baseline Array (see e.g. Krishnan et al 2015Krishnan et al , 2017 and, in the future, the African VLBI Network and the Square Kilometre Array in Australia and South Africa -will supplement the lack of precise astrometric data in quadrants III and IV of the Milky Way plane, where only a few sources have been measured. Moreover, astrometric studies that include the inner Galactic region, such as the Bulge Asymmetries and Dynamic Evolution (BAaDE 2 ) project, aim to resolve the dynamics of the bar by measuring proper motions and distances of SiO masers present in AGB stars (Sjouwerman et al 2017).…”

Section: Discussionmentioning

confidence: 99%

Simulated Galactic methanol maser distribution to constrain Milky Way parameters

Quiroga-Nuñez

Langevelde

Reid

et al. 2017

A&A

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Context. Using trigonometric parallaxes and proper motions of masers associated with massive young stars, the Bar and Spiral Structure Legacy (BeSSeL) survey has reported the most accurate values of the Galactic parameters so far. The determination of these parameters with high accuracy has a widespread impact on Galactic and extragalactic measurements. Aims. This research is aimed at establishing the confidence with which such parameters can be determined. This is relevant for the data published in the context of the BeSSeL survey collaboration, but also for future observations, in particular from the southern hemisphere. In addition, some astrophysical properties of the masers can be constrained, notably the luminosity function. Methods. We have simulated the population of maser-bearing young stars associated with Galactic spiral structure, generating several samples and comparing them with the observed samples used in the BeSSeL survey. Consequently, we checked the determination of Galactic parameters for observational biases introduced by the sample selection. Results. Galactic parameters obtained by the BeSSeL survey do not seem to be biased by the sample selection used. In fact, the published error estimates appear to be conservative for most of the parameters. We show that future BeSSeL data and future observations with southern arrays will improve the Galactic parameters estimates and smoothly reduce their mutual correlation. Moreover, by modeling future parallax data with larger distance values and, thus, greater relative uncertainties for a larger numbers of sources, we found that parallax-distance biasing is an important issue. Hence, using fractional parallax uncertainty in the weighting of the motion data is imperative. Finally, the luminosity function for 6.7 GHz methanol masers was determined, allowing us to estimate the number of Galactic methanol masers.

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Section: Discussionmentioning

confidence: 99%

Simulated Galactic methanol maser distribution to constrain Milky Way parameters

Quiroga-Nuñez

Langevelde

Reid

et al. 2017

A&A

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“…In the Ist Galactic quadrant, such measurements are available for 59 out of 85 sources (70%), providing a robust estimate of their physical parameters. Sources in the IVth Galactic quadrant have less reliable distance measurements owing to the lack of currently available maser parallax distances, except for G339.8841-1.2568 (Krishnan et al 2015). We were able to provide distance estimates to all but one source in the sample (see Table 4).…”

Section: Distances and Association With Massive Molecular Complexesmentioning

confidence: 97%

The ATLASGAL survey: The sample of young massive cluster progenitors

Csengeri

Bontemps

Wyrowski

et al. 2017

A&A

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Context. The progenitors of high-mass stars and clusters are still challenging to recognise. Only unbiased surveys, sensitive to compact regions of high dust column density, can unambiguously reveal such a small population of particularly massive and cold clumps. Aims. Here we use the ATLASGAL survey to identify a sample of candidate progenitors of massive clusters in the inner Galaxy. Methods. We characterise a flux limited sample of compact sources selected from the ATLASGAL survey. Sensitive mid-infrared data at 21−24 µm from the WISE and MIPSGAL surveys were explored to search for embedded objects, and complementary spectroscopic data were used to investigate their stability and their star formation activity. Results. We identify an unbiased sample of infrared-quiet massive clumps in the Galaxy that potentially represent the earliest stages of massive cluster formation. An important fraction of this sample consists of sources that have not been studied in detail before. We first find that clumps hosting more evolved embedded objects and infrared-quiet clumps exhibit similar physical properties in terms of mass and size, suggesting that the sources are not only capable of forming high-mass stars, but likely also follow a single evolutionary track leading to the formation of massive clusters. The majority of the clumps are likely not in virial-equilibrium, suggesting collapse on the clump scale. Conclusions. We identify the precursors of the most massive clusters in the Galaxy within our completeness limit, and argue that these objects are undergoing large-scale collapse. This is in line with the low number of infrared-quiet massive clumps and earlier findings that star formation, in particular for high-mass objects is a fast, dynamic process. We propose a scenario in which massive clumps start to fragment and collapse before their final mass is accumulated indicating that strong self-gravity and global collapse is needed to build up rich clusters and the most massive stars.

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“…88-1.26 (a.k.a. IRAS 16484-4603; hereafter G339) is a massive protostellar source at a distance of d = 2.1 kpc (Krishnan et al 2015). Interferometric radio continuum observations revealed an elongated structure of ∼ 10 with a position angle of 45 • east of north (Ellingsen et al 1996;Purser et al 2016), which is believed to be tracing an ionized jet.…”

Section: Introductionmentioning

confidence: 99%

An Ordered Envelope–Disk Transition in the Massive Protostellar Source G339.88-1.26

Zhang¹,

Tan²,

Sakai³

et al. 2019

ApJ

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We report molecular line observations of the massive protostellar source G339.88-1.26 with the Atacama Large Millimeter/Submillimeter Array. The observations reveal a highly collimated SiO jet extending from the 1.3 mm continuum source, which connects to a slightly wider but still highly collimated CO outflow. Rotational features perpendicular to the outflow axis are detected in various molecular emissions, including SiO, SO 2 , H 2 S, CH 3 OH, and H 2 CO emissions. Based on their spatial distributions and kinematics, we find that they trace different parts of the envelope-disk system. The SiO emission traces the disk and inner envelope in addition to the jet. The CH 3 OH and H 2 CO emissions mostly trace the infalling-rotating envelope, and are enhanced around the transition region between envelope and disk, i.e., the centrifugal barrier. The SO 2 and H 2 S emissions are enhanced around the centrifugal barrier, and also trace the outer part of the disk. Envelope kinematics are consistent with rotating-infalling motion, while those of the disk are consistent with Keplerian rotation. The radius and velocity of the centrifugal barrier are estimated to be about 530 au and 6 km s −1 , leading to a central mass of about 11 M , consistent with estimates based on spectral energy distribution fitting. These results indicate that an ordered transition from an infalling-rotating envelope to a Keplerian disk through a centrifugal barrier, accompanied by changes of types of molecular line emissions, is a valid description of this massive protostellar source. This implies that at least some massive stars form in a similar way as low-mass stars via Core Accretion.

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FIRST PARALLAX MEASUREMENTS TOWARD A 6.7 GHz METHANOL MASER WITH THE AUSTRALIAN LONG BASELINE ARRAY—DISTANCE TO G 339.884−1.259.

Cited by 33 publications

References 79 publications

Simulated Galactic methanol maser distribution to constrain Milky Way parameters

Simulated Galactic methanol maser distribution to constrain Milky Way parameters

The ATLASGAL survey: The sample of young massive cluster progenitors

An Ordered Envelope–Disk Transition in the Massive Protostellar Source G339.88-1.26

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