A Co Line and Infrared Continuum Study of the Active Star-Forming Complex W51

Kang, Miju; Bieging, John H.; Kulesa, Craig; Lee, Youngung; Choi, Minho; Peters, William L.

doi:10.1088/0067-0049/190/1/58

Cited by 28 publications

(54 citation statements)

References 60 publications

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“…This is consistent with the triggered star formation scenario that is due to the interaction of the filament with the main cloud, as proposed by Carpenter & Sanders (1998). Recently, Kang et al (2010) compared the 2 O spectrum along with a Gaussian fit are taken from Flagey et al (2013). Right: multiple transitions of NH 3 observed with Herschel.…”

Section: New Velocity Component Along the W51e2 Sightlinesupporting

confidence: 84%

“…Therefore the 62.3 and 68.8 km s −1 components are most likely associated with a high-velocity (HV) stream. Note also that the CO line emission is brightest at v LSR = 58 km s −1 (Kang et al 2010), indicating that the ionized and molecular gas have similar velocities and are probably associated with the same radio continuum source. Using H 2 CO observations, Arnal & Goss (1985) detected five absorption components at ∼52, 55, 57, 66, and 70 km s −1 toward W51e2.…”

Section: New Velocity Component Along the W51e2 Sightlinementioning

confidence: 88%

“…We propose that the feature arises in a dense (n(H 2 ) = (1-5) × 10 5 cm −3 ) and cold (10-30 K) clump that is formed within the much larger scale filament (detected in CO) deemed to be interacting with the W51 main molecular cloud. A possible scenario for the formation of the dense clump can be outlined based on the collision of the filament with W51 main (Kang et al 2010). In this scenario, cloud-cloud collision lead to the compression of the interface region and initiate the formation of stars as seen in W51 (Habe & Ohta 1992).…”

Section: Possible Origin Of the Clumpmentioning

confidence: 99%

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Detection of a dense clump in a filament interacting with W51e2

Mookerjea

Vastel

Hassel

et al. 2014

A&A

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In the framework of the Herschel/PRISMAS guaranteed time key program, the line of sight to the distant ultracompact H ii region W51e2 has been observed using several selected molecular species. Most of the detected absorption features are not associated with the background high-mass star-forming region and probe the diffuse matter along the line of sight. We present here the detection of an additional narrow absorption feature at ∼70 km s −1 in the observed spectra of HDO, NH 3 and C 3 . The 70 km s −1 feature is not uniquely identifiable with the dynamic components (the main cloud and the large-scale foreground filament) so-far identified toward this region. The narrow absorption feature is similar to the one found toward low-mass protostars, which is characteristic of the presence of a cold external envelope. The far-infrared spectroscopic data were combined with existing ground-based observations of 12 CO, 13 CO, CCH, CN, and C 3 H 2 to characterize the 70 km s −1 component. Using a non-LTE analysis of multiple transitions of NH 3 and CN, we estimated the density (n(H 2 ) ∼ (1-5) × 10 5 cm −3 ) and temperature (10-30 K) for this narrow feature. We used a gasgrain warm-up based chemical model with physical parameters derived from the NH 3 data to explain the observed abundances of the different chemical species. We propose that the 70 km s −1 narrow feature arises in a dense and cold clump that probably undergoes collapse to form a low-mass protostar, formed on the trailing side of the high-velocity filament, which is thought to be interacting with the W51 main cloud. While the fortuitous coincidence of the dense clump along the line of sight with the continuum-bright W51e2 compact H ii region has contributed to its nondetection in the continuum images, this same attribute makes it an appropriate source for absorption studies and in particular for ice studies of star-forming regions.

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Section: New Velocity Component Along the W51e2 Sightlinesupporting

confidence: 84%

Section: New Velocity Component Along the W51e2 Sightlinementioning

confidence: 88%

Section: Possible Origin Of the Clumpmentioning

confidence: 99%

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Detection of a dense clump in a filament interacting with W51e2

Mookerjea

Vastel

Hassel

et al. 2014

A&A

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“…Presently, we don't have optically thin line data (such as, NH 3 and CS) for the EFS, hence, the high-resolution molecular line data will be required to further explore the EFS and its velocity structure. It has been observationally evident that numerous complex processes involved in star formation operate in a given star-forming complex (e.g., Kang et al 2010;Dewangan et al 2016). At least three YSO clusters are found at one EFS end and also appear to be found near the edges of the shell-like morphology linked with the S242 H ii region (see Figures 7a, 8b, and 9a).…”

Section: Discussionmentioning

confidence: 99%

The Molecular Cloud S242: Physical Environment and Star-formation Activities

Dewangan

Baug

Ojha

et al. 2017

ApJ

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We present a multi-wavelength study to probe the star formation (SF) processes on a larger scale (∼1• .05 × 0 • .56) around the S242 site. The S242 molecular cloud is depicted in a velocity range from −3.25 to 4.55 km s −1 and has spatially elongated appearance. Based on the virial analysis, the cloud is prone to gravitational collapse. The cloud harbors an elongated filamentary structure (EFS; length ∼25 pc) evident in the Herschel column density map and the EFS has an observed mass per unit length of ∼200 M pc −1 exceeding the critical value of ∼16 M pc −1 (at T = 10 K). The EFS contains a chain of Herschel clumps (M clump ∼150 to 1020 M ), revealing the evidence of fragmentation along its length. The most massive clumps are observed at both the EFS ends, while the S242 H ii region is located at one EFS end. Based on the radio continuum maps at 1.28 and 1.4 GHz, the S242 H ii region is ionized by a B0.5V-B0V type star and has a dynamical age of ∼0.5 Myr. The photometric 1-5 µm data analysis of point-like sources traces young stellar objects (YSOs) toward the EFS and the clusters of YSOs are exclusively found at both the EFS ends, revealing the SF activities. Considering the spatial presence of massive clumps and YSO clusters at both the EFS ends, the observed results are consistent with the prediction of a SF scenario of the end-dominated collapse driven by the higher accelerations of gas.

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“…If a group of stellar clusters in our sample was found to form a physically associated complex according to their positions and radial velocities, we identified it in the column Complex of the catalog. When the complex was identified in the literature, we here list its name (e.g., the giant molecular cloud W51; Kang et al 2010). References for complex identification and analysis are provided in the column ref_Complex.…”

Section: B5 Stellar Distance and Agementioning

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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A Co Line and Infrared Continuum Study of the Active Star-Forming Complex W51

Cited by 28 publications

References 60 publications

Detection of a dense clump in a filament interacting with W51e2

Detection of a dense clump in a filament interacting with W51e2

The Molecular Cloud S242: Physical Environment and Star-formation Activities

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

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