The Stellar Content of Obscured Galactic Giant H Ii Regions. Vi. W51a

Figuerêdo, E.; Blum, Robert; Damineli, A.; Conti, Peter S.; Barbosa, C. L.

doi:10.1088/0004-6256/136/1/221

Cited by 32 publications

(95 citation statements)

References 47 publications

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“…It implies that W51 is not only very massive but that it could also be exceptionally young, even when compared to M17. This result is consistent with the idea that W51 IRS 2E, the most luminous embedded source in W51A, is a highly embedded, very young O star that has yet to produce a detectable hypercompact H II region (Figuerêdo et al 2008). The shift of the color selection criteria in the direction of the reddening vector is consistent with the fact that the W51 complex is a more massive star forming region with more extinction than the star forming region studied by Allen et al (2004).…”

Section: Resultssupporting

confidence: 90%

Embedded Young Stellar Object Candidates in the Active Star-Forming Complex W51: Mass Function and Spatial Distribution

Kang

Bieging

Povich

et al. 2009

ApJ

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We present 737 candidate Young Stellar Objects (YSOs) near the W51 Giant Molecular Cloud (GMC) over an area of 1.25 • × 1.00 • selected from Spitzer Space Telescope data. We use spectral energy distribution (SED) fits to identify YSOs and distinguish them from main-sequence or red giant stars, asymptotic giant branch stars, and background galaxies. Based on extinction of each YSO, we separate a total of 437 YSOs associated with the W51 region from the possible foreground sources. We identify 69 highly embedded Stage 0/I candidate YSOs in our field with masses > 5 M ⊙ (corresponding to mid-to early-B main-sequence spectral types) 46 of which are located in the central active star forming regions of W51A and W51B. From the YSOs associated with W51, we find evidence for mass segregation showing that the most massive YSOs are concentrated on the W51 H II region complex. We find a variation in the spatial distribution of the mass function (MF) of YSOs in the mass range between 5 M ⊙ and 18 M ⊙ . The derived slopes of the MF are −1.26 and −2.36 in the active starforming region and the outer region, respectively. The variation of the MF for YSOs embedded in the molecular cloud implies that the distribution of stellar masses in clusters depends on the local conditions in the parent molecular cloud.

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Section: Resultssupporting

confidence: 90%

Embedded Young Stellar Object Candidates in the Active Star-Forming Complex W51: Mass Function and Spatial Distribution

Kang

Bieging

Povich

et al. 2009

ApJ

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“…Subsequent spectroscopic observations by Figueredo et al (2008) and Barbosa et al (2008) confirmed these findings, identifying several early-mid O stars within W51A and resolved the subregion W51 IRS2 (see Fig. 1) into a proto cluster containing an ∼O3 star and a massive YSO.…”

Section: Introductionmentioning

confidence: 66%

“…While we defer a detailed description of the Spitzer data to a future paper, we note that the morphology of the emission also casts doubt on the hypothesis of OMN2000 that SF in their Region 1 subsequently triggered similar activity in their Region 3 (which contains the massive proto-cluster IRS2; Figueredo et al 2008;Barbosa et al 2008). Under such a scenario we might expect to see a mid-IR morphology similar to that of the G305 SF complex (Clark & Porter 2004), with IRS2 residing on the periphery of a large wind blown cavity, which would be readily visible in e.g.…”

Section: The Star Formation History Of W51mentioning

confidence: 96%

“…For a distance to W51 of 6 kpc, the O stars discussed by Figueredo et al (2008) are at projected distances of 2-4 pc from the compact star forming region IRS2. While it might appear unlikely for evolved stars to be located so close to regions of ongoing SF, early O supergiants are found within the massive star forming regions G305 (Leistra et al 2005) and W43 (Blum et al 1999).…”

Section: The Distance To [Omn2000] Ls1mentioning

confidence: 99%

“…1; RA = 19 23 47.64 δ = +14 36 38.4). OMN2000 described it as a 'P Cygni type supergiant' and Article published by EDP Sciences For clarity we also indicate SF regions 1 and 3 as defined by OMN2000 (the latter containing the O star candidates identified by Figueredo et al 2008), the heavily embedded massive YSO forming complex IRS2 and 3 further regions throughout the W51 complex which Nanda Kumar et al (2004) find to host massive young stellar clusters (the fourth region studied in detail by Nanda Kumar et al encompasses IRS2 and is located within Region 3 of OMN2000). Note that for reasons of clarity not all the locations of star formation activity identified by these authors are indicated in this figure. classified it as O4 I, with a progenitor mass of ∼120 M , making it of considerable interest as one of the most massive, evolved stars in the Galaxy.…”

Section: Introductionmentioning

confidence: 99%

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The P Cygni supergiant [OMN2000] LS1 – implications for the star formation history of W51

Clark¹,

Davies²,

Najarro³

et al. 2009

A&A

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Aims. We investigate the nature of the massive star [OMN2000] LS1 and use these results to constrain the history of star formation within the host complex W51. Methods. We utilised a combination of near-IR spectroscopy and non-LTE model atmosphere analysis to derive the physical properties of [OMN2000] LS1, and a combination of theoretical evolutionary calculations and Monte Carlo simulations to apply limits on the star formation history of W51. Results. We find the spectrum of [OMN2000] LS1 to be consistent with that of a P Cygni supergiant. With a temperature in the range of 13.2-13.7 kK and log(L * /L ) ≤ 5.75, it is significantly cooler, less luminous, and less massive than proposed by previous authors. The presence of such a star within W51 shows that star formation has been underway for at least 3 Myr, while the formation of massive O stars is still on going. The lack of a population of evolved red supergiants within the complex shows that the rate of formation of young massive clusters at ages ≥9 Myr was lower than currently observed. We find no evidence of internally triggered, sequential star formation within W51, and favour the suggestion that star formation has proceeded at multiple indepedent sites within the GMC. Along with other examples, such as the G305 and Carina star-forming regions, we suggest that W51 is a Galactic analogue of the ubiquitous star cluster complexes seen in external galaxies such as M51 and NGC2403.

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Twin Masks of Spiral Structure? A Local Perspective

Steiman-Cameron

2010

Galaxies and Their Masks

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The Stellar Content of Obscured Galactic Giant H Ii Regions. Vi. W51a

Cited by 32 publications

References 47 publications

Embedded Young Stellar Object Candidates in the Active Star-Forming Complex W51: Mass Function and Spatial Distribution

Embedded Young Stellar Object Candidates in the Active Star-Forming Complex W51: Mass Function and Spatial Distribution

The P Cygni supergiant [OMN2000] LS1 – implications for the star formation history of W51

Twin Masks of Spiral Structure? A Local Perspective

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