The RMS survey: resolving kinematic distance ambiguities towards a sample of compact H ii regions using H i absorption★

Urquhart, J. S.; Hoare, M. G.; Lumsden, S. L.; Oudmaijer, R. D.; Moore, T. J. T.; Mottram, J. C.; Cooper, H. D. B.; Mottram, M.; Rogers, Hazel

doi:10.1111/j.1365-2966.2011.20157.x

Cited by 60 publications

(62 citation statements)

References 46 publications

(104 reference statements)

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“…This ambiguity can often be resolved by assessing the presence or absence of absorption or self-absorption lines in the 21 cm H I spectrum (cf. Kolpak et al 2003;Roman-Duval et al 2009;Green & McClure-Griffiths 2011;Jones & Dickey 2012;Urquhart et al 2012Urquhart et al , 2014Wienen et al 2015).…”

Section: Motivation and Methodsmentioning

confidence: 99%

MALT90 Kinematic Distances to Dense Molecular Clumps

Whitaker

Jackson

Rathborne

et al. 2017

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Using molecular-line data from the Millimetre Astronomy Legacy Team 90 GHz Survey (MALT90), we have estimated kinematic distances to 1905 molecular clumps identified in the ATLASGAL 870 μm continuum survey over the longitude range 295°<l<350°. The clump velocities were determined using a flux-weighted average of the velocities obtained from Gaussian fits to the HCO + , HNC, and N 2 H + (1-0) transitions. The near/far kinematic distance ambiguity was addressed by searching for the presence or absence of absorption or self-absorption features in 21 cm atomic hydrogen spectra from the Southern Galactic Plane Survey. Our algorithm provides an estimation of the reliability of the ambiguity resolution. The Galactic distribution of the clumps indicates positions where the clumps are bunched together, and these locations probably trace the locations of spiral arms. Several clumps fall at the predicted location of the far side of the Scutum-Centaurus arm. Moreover, a number of clumps with positive radial velocities are unambiguously located on the far side of the Milky Way at galactocentric radii beyond the solar circle. The measurement of these kinematic distances, in combination with continuum or molecular-line data, now enables the determination of fundamental parameters such as mass, size, and luminosity for each clump.

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Section: Motivation and Methodsmentioning

confidence: 99%

MALT90 Kinematic Distances to Dense Molecular Clumps

Whitaker

Jackson

Rathborne

et al. 2017

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“…Lépine et al (2011) solved the kinematic distance ambiguity problem for more than 800 CS (2−1) emission sources , which are associated with the confident candidates of UCHII regions (Wood & Churchwell 1989). By analyzing the HI absorption data toward a sample of compact HII regions identified from the Red MSX Source Survey (Hoare et al 2005), Urquhart et al (2012) solved the kinematic distance ambiguity for about 105 HII regions. Similar work was conducted by Jones & Dickey (2012) for 75 HII regions.…”

Section: Hii Regionsmentioning

confidence: 99%

“…Some newly discovered HII regions or GMCs even as far as ∼20 kpc from the Sun Dame & Thaddeus 2011) provide important data to reveal the spiral structure in the outer Galaxy. The kinematic distance ambiguity for many HII regions, GMCs, and 6.7 GHz methanol masers has been solved (e.g., Roman-Duval et Lépine et al 2011;Anderson et al 2012;Urquhart et al 2012;Jones & Dickey 2012), which enables us to estimate their kinematic distances. In addition, the more reliable trigonometric or photometric distances of a number of HII regions or masers have been measured (e.g., Rygl et al 2010;Sato et al 2010a; Moisés et al 2011;Xu et al 2011Xu et al , 2013Russeil et al 2012;Zhang et al 2014;Foster & Brunt 2014).…”

Section: Introductionmentioning

confidence: 99%

The observed spiral structure of the Milky Way

Hou

Han

2014

A&A

237

233

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Context. The spiral structure of the Milky Way is not yet well determined. The keys to understanding this structure are to increase the number of reliable spiral tracers and to determine their distances as accurately as possible. HII regions, giant molecular clouds (GMCs), and 6.7 GHz methanol masers are closely related to high mass star formation, and hence they are excellent spiral tracers. The distances for many of them have been determined in the literature with trigonometric, photometric, and/or kinematic methods. Aims. We update the catalogs of Galactic HII regions, GMCs, and 6.7 GHz methanol masers, and then outline the spiral structure of the Milky Way. Methods. We collected data for more than 2500 known HII regions, 1300 GMCs, and 900 6.7 GHz methanol masers. If the photometric or trigonometric distance was not yet available, we determined the kinematic distance using a Galaxy rotation curve with the current IAU standard, R 0 = 8.5 kpc and Θ 0 = 220 km s −1 , and the most recent updated values of R 0 = 8.3 kpc and Θ 0 = 239 km s −1 , after velocities of tracers are modified with the adopted solar motions. With the weight factors based on the excitation parameters of HII regions or the masses of GMCs, we get the distributions of these spiral tracers.Results. The distribution of tracers shows at least four segments of arms in the first Galactic quadrant, and three segments in the fourth quadrant. The Perseus Arm and the Local Arm are also delineated by many bright HII regions. The arm segments traced by massive star forming regions and GMCs are able to match the HI arms in the outer Galaxy. We found that the models of three-arm and four-arm logarithmic spirals are able to connect most spiral tracers. A model of polynomial-logarithmic spirals is also proposed, which not only delineates the tracer distribution, but also matches the observed tangential directions.

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“…For the RMS survey, which is an ongoing project, we took the KDA solutions from an on-line search we performed for every possibly associated source on "The RMS Database Server" 25 ; these solutions arise from dedicated application of H i absorption methods (Urquhart et al 2011(Urquhart et al , 2012, from the literature, or from grouping of sources close in the phase space where there is at least one with resolved KDA. Additional KDA solutions were found through the SIMBAD coordinate query of each source, or from the reference from which the final cluster distance was adopted (e.g., a more accurate method such as maser parallax, see Sect.…”

Section: B44 Resolution Of the Kinematic Distance Ambiguitymentioning

confidence: 99%

Stellar clusters in the inner Galaxy and their correlation with cold dust emission

Morales

Wyrowski

Schüller

et al. 2013

A&A

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Context. Stars are born within dense clumps of giant molecular clouds, and constitute young stellar agglomerates known as embedded clusters, which only evolve into bound open clusters under special conditions. Aims. We statistically study all embedded clusters (ECs) and open clusters (OCs) known so far in the inner Galaxy, in particular investigating their interaction with the surrounding molecular environment and the differences in their evolution. Methods. We first compiled a merged list of 3904 clusters from optical and infrared cluster catalogs in the literature, including 75 new (mostly embedded) clusters discovered by us in the GLIMPSE survey. From this list, 695 clusters are within the Galactic range | | ≤ 60 • and |b| ≤ 1.5 • covered by the ATLASGAL survey, which was used to search for correlations with submm dust continuum emission tracing dense molecular gas. We defined an evolutionary sequence of five morphological types: deeply embedded cluster (EC1), partially embedded cluster (EC2), emerging open cluster (OC0), OC still associated with a submm clump in the vicinity (OC1), and OC without correlation with ATLASGAL emission (OC2). Together with this process, we performed a thorough literature survey of these 695 clusters, compiling a considerable number of physical and observational properties in a catalog that is publicly available. Results. We found that an OC defined observationally as OC0, OC1, or OC2 and confirmed as a real cluster is equivalent to the physical concept of OC (a bound exposed cluster) for ages in excess of ∼16 Myr. Some observed OCs younger than this limit can actually be unbound associations. We found that our OC and EC samples are roughly complete up to ∼1 kpc and ∼1.8 kpc from the Sun, respectively, beyond which the completeness decays exponentially. Using available age estimates for a few ECs, we derived an upper limit of 3 Myr for the duration of the embedded phase. Combined with the OC age distribution within 3 kpc of the Sun, which shows an excess of young exposed clusters compared to a theoretical fit that considers classical disruption mechanisms, we computed an embedded and young cluster dissolution fraction of 88 ± 8%. This high fraction is thought to be produced by several factors and not only by the classical paradigm of fast gas expulsion.

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The RMS survey: resolving kinematic distance ambiguities towards a sample of compact H ii regions using H i absorption★

Cited by 60 publications

References 46 publications

MALT90 Kinematic Distances to Dense Molecular Clumps

MALT90 Kinematic Distances to Dense Molecular Clumps

The observed spiral structure of the Milky Way

Stellar clusters in the inner Galaxy and their correlation with cold dust emission

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