Getting to the bottom of the lagoon - Dust, magnetism, and star formation

McCall, Marshall L.; Richer, M. G.; Visvanathan, N.

doi:10.1086/168937

Cited by 18 publications

(42 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, the circumstellar effects cannot be disregarded, since the grain growth is expected to occur in protoplanetary discs. In this case, our results also agree with the polarimetric results of McCall et al (1990), which suggested that the anomalous R V is due to circumstellar effects.…”

Section: Discussionsupporting

confidence: 90%

“…This material was possibly contained in a massive dense core within the cloud, whose structure was changed by the process of cluster formation consuming the core. This scenario is consistent with the suggestion that NGC 6530 lies within an HII cavity (McCall et al 1990). …”

Section: Comparing Clouds and Clusterssupporting

confidence: 91%

“…Despite being along a lineof-sight that contains a high concentration of gas, NGC 6530 appears to be decoupled from the molecular cloud once the cluster members do not seem to be very embedded. This implies that NGC 6530 is inside the cavity of the HII region (McCall et al 1990), as indicated by measurements of the expanding gas (Welsh 1983). A range of 0.17 mag to 0.33 mag has been reported for the colour-excess in the direction of NGC 6530 (Mayne & Naylor 2008).…”

Section: Selected Clustersmentioning

confidence: 76%

“…Most of these objects had their SED well-fitted Appendix is available in electronic form at http://www.aanda.org by assuming that R V = 3.1, with some exceptions that show anomalous R V and have high extinction probably owing to the circumstellar material. From the results of a polarimetric survey in the direction of the Lagoon Nebula (M8), McCall et al (1990) estimated that R V = 4.64 ± 0.27, which they attributed to circumstellar effects. This anomalous R V was obtained after removing the normal foreground extinction.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Probing the anomalous extinction of four young star clusters: the use of colour-excess, main-sequence fitting and fractal analysis

Fernandes

Gregorio-Hetem

Hetem

2012

A&A

View full text Add to dashboard Cite

Aims. We studied four young star clusters to characterise their anomalous extinction or variable reddening and asses whether they could be due to contamination by either dense clouds or circumstellar effects. Methods. We evaluated the extinction law (R V ) by adopting two methods: (i) the use of theoretical expressions based on the colourexcess of stars with known spectral type; and (ii) the analysis of two-colour diagrams, where the slope of the observed colour distribution was compared to the normal distribution. An algorithm to reproduce the zero-age main-sequence (ZAMS) reddened colours was developed to derive the average visual extinction (A V ) that provides the closest fit to the observational data. The structure of the clouds was evaluated by means of a statistical fractal analysis, designed to compare their geometric structure with the spatial distribution of the cluster members. Results. The cluster NGC 6530 is the only object of our sample affected by anomalous extinction. On average, the other clusters suffer normal extinction, but several of their members, mainly in NGC 2264, seem to have high R V , probably because of circumstellar effects. The ZAMS fitting provides A V values that are in good agreement with those found in the literature. The fractal analysis shows that NGC 6530 has a centrally concentrated distribution of stars that differs from the substructures found in the density distribution of the cloud projected in the A V map, suggesting that the original cloud was changed by the cluster formation. However, the fractal dimension and statistical parameters of Berkeley 86, NGC 2244, and NGC 2264 indicate that there is a good cloud-cluster correlation, when compared to other works based on an artificial distribution of points.

show abstract

Section: Discussionsupporting

confidence: 90%

Section: Comparing Clouds and Clusterssupporting

confidence: 91%

Section: Selected Clustersmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Probing the anomalous extinction of four young star clusters: the use of colour-excess, main-sequence fitting and fractal analysis

Fernandes

Gregorio-Hetem

Hetem

2012

A&A

View full text Add to dashboard Cite

show abstract

“…m 09 by Chini & Neckel (1981) and 1.86±0.07 kpc by McCall et al (1990). Because Chini & Neckel (1981) neglected the effects of anomalous extinction and used only very rough spectral classifications from UBV photometry we concluded that a new study of this cluster, taking into account these effects, might yield different results.…”

Section: Introductionmentioning

confidence: 89%

A multiwavelength study of star formation in the very young open cluster NGC 6530

Ancker

Feinstein

Vazquez

et al. 1997

Astron. Astrophys. Suppl. Ser.

View full text Add to dashboard Cite

Abstract. The distance and formation history of the very young open cluster NGC 6530 were investigated by studying a total of 132 probable member stars of this open cluster. It was concluded that the distance to NGC 6530 is 1.8 ± 0.2 kpc, and its interstellar reddening E(B − V ) is 0.m 30. Furthermore, we conclude that the extinction law of the intracluster material is normal (i.e. R V = 3.1), but anomalous extinction laws were found for several more embedded stars in the cluster. Of the 132 stars included in this study, 11 are suspected to be variable, five show Hα in emission and nine show an infrared excess. Among the member stars of NGC 6530, three were found to be part of the Herbig Ae/Be stellar class, whereas two others are possible members of this stellar group as well. Also, one cluster member is probably a new massive post-AGB star, whereas the same could possibly apply to another member star. Finally, from the distribution of post-and pre-main sequence stars in the cluster's HR-diagram, it was concluded that the process of star formation in NGC 6530 must have started a few times 10 7 years ago and, for the less massive stars, is probably still going on today.

show abstract

OH masers and magnetic fields in the bipolar outflow source W75N

Hutawarakorn

Cohen

Brebner

2002

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

MERLIN polarization measurements of 1665‐,1667‐ and 1720‐MHz OH masers in the bipolar outflow source W75N are presented. The OH masers are distributed over a region 5 arcsec across (10 000 au at 2 kpc), which is elongated in a north‐west–south‐east (NW–SE) direction. The distribution is interpreted in terms of a rotating disc orthogonal to the bipolar outflow that is seen in CO and H2. A compact cluster of OH masers with a large velocity spread appears to mark the source of the outflow. Most of the OH masers detected have strong circular polarization up to 100 per cent. Seven Zeeman groups are identified, including the first example of a complete Zeeman triplet (two σ‐components and one π‐component). The field strength measured from Zeeman pairs of opposite circular polarization ranges from −8 to +8 mG, with a field reversal on opposite sides of the disc. This is interpreted in terms of a toroidal component of the magnetic field in the disc. Linear polarization is also detected in many of the OH masers with some 1665‐MHz masers showing up to 100 per cent linear polarization. The polarization position angles are preferentially along the direction of the bipolar outflow or perpendicular to it. The polarization data lend support to the twisted magnetic field model originally proposed by Uchida & Shibata.

show abstract

Getting to the bottom of the lagoon - Dust, magnetism, and star formation

Cited by 18 publications

References 0 publications

Probing the anomalous extinction of four young star clusters: the use of colour-excess, main-sequence fitting and fractal analysis

Probing the anomalous extinction of four young star clusters: the use of colour-excess, main-sequence fitting and fractal analysis

A multiwavelength study of star formation in the very young open cluster NGC 6530

OH masers and magnetic fields in the bipolar outflow source W75N

Contact Info

Product

Resources

About