Star formation and disk properties in Pismis 24

Fang, Min; Boekel, R. van; King, Robert R.; Henning, Th.; Bouwman, J.; Doi, Yasuo; Okamoto, Y.; Roccatagliata, V.; Sicilia‐Aguilar, A.

doi:10.1051/0004-6361/201015914

Cited by 86 publications

(140 citation statements)

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“…Massey et al (2001) compared the most massive cluster stars with isochrones in a Hertzsprung-Russell diagram finding a median age of 1.7 Myr and a very likely coevality. A similar exercise was done by Fang et al (2012), who found that the age of the 6 most massive stars is between 1-2.7 Myr if they are assumed to be coeval. On the other hand, Fang et al (2012) obtained optical spectra and RI photometry for 151 stars with an X-ray counterpart, deriving their spectral type and extinction.…”

Section: Age Of Pismis 24 and Masses Of Stars From The Optical Hst Datamentioning

confidence: 66%

“…The radial distribution of X-ray source surface density is characterised by a core ∼2 in radius superimposed on a halo with a radius of at least 8 . Optical (RI) photometry and spectroscopy (of a smaller sub-sample) with VIMOS at the VLT (Fang et al 2012) confirmed that these are PMS stars with a median age of 1 Myr and an age spread in the range < ∼ 0.1 to > ∼ 10 Myr. In addition, the IMF is consistent with that of the Orion Nebula Cluster (ONC).…”

Section: Introductionmentioning

confidence: 89%

“…Alternatively, one can use the pseudo-sequence as a reference and pick all the sources inside a well-defined extinction interval from it. In principle one could choose the extinction range found in the visible, 3.2 < A V < 7.8 (Fang et al 2012). However, Figs.…”

Section: K S Luminosity Function Of Pismis 24mentioning

confidence: 99%

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Young open clusters in the Galactic star forming region NGC 6357

Massi

Giannetti

Carlo

et al. 2014

A&A

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Context. NGC 6357 is an active star forming region with very young massive open clusters. These clusters contain some of the most massive stars in the Galaxy and strongly interact with nearby giant molecular clouds. Aims. We study the young stellar populations of the region and of the open cluster Pismis 24, focusing on their relationship with the nearby giant molecular clouds. We seek evidence of triggered star formation "propagating" from the clusters. Methods. We used new deep JHK s photometry, along with unpublished deep Spitzer/IRAC mid-infrared photometry, complemented with optical HST/WFPC2 high spatial resolution photometry and X-ray Chandra observations, to constrain age, initial mass function, and star formation modes in progress. We carefully examine and discuss all sources of bias (saturation, confusion, different sensitivities, extinction). Results. NGC 6357 hosts three large young stellar clusters, of which Pismis 24 is the most prominent. We found that Pismis 24 is a very young (∼1-3 Myr) open cluster with a Salpeter-like initial mass function and a few thousand members. A comparison between optical and infrared photometry indicates that the fraction of members with a near-infrared excess (i.e., with a circumstellar disk) is in the range 0.3-0.6, consistent with its photometrically derived age. We also find that Pismis 24 is likely subdivided into a few different subclusters, one of which contains almost all the massive members. There are indications of current star formation triggered by these massive stars, but clear age trends could not be derived (although the fraction of stars with a near-infrared excess does increase towards the Hii region associated with the cluster). The gas out of which Pismis 24 formed must have been distributed in dense clumps within a cloud of less dense gas ∼1 pc in radius. Conclusions. Our findings provide some new insight into how young stellar populations and massive stars emerge, and evolve in the first few Myr after birth, from a giant molecular cloud complex.

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Section: Age Of Pismis 24 and Masses Of Stars From The Optical Hst Datamentioning

confidence: 66%

Section: Introductionmentioning

confidence: 89%

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Young open clusters in the Galactic star forming region NGC 6357

Massi

Giannetti

Carlo

et al. 2014

A&A

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“…The open cluster Pismis 24 (Pi 24) contains the WC7+O binary system WR 93, and has conflicting distance meaurements in the literature, i.e., 2.56 ± 0.10 kpc (Massey, DeGioia-Eastwood & Waterhouse 2001a) and 1.7 ± 0.2 kpc (Fang et al 2012). In Figure B1 we plot Lejeune & Schaerer (2001) isochrones along with the positions of the 8 brightest O-stars in Pi 24.…”

Section: B01 Pismis 24 and Wr 93mentioning

confidence: 99%

Spatial distribution of Galactic Wolf–Rayet stars and implications for the global population

Rosslowe

Crowther

2015

Monthly Notices of the Royal Astronomical Society

118

142

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We construct revised near-infrared absolute magnitude calibrations for 126 Galactic Wolf-Rayet (WR) stars at known distances, based in part upon recent large scale spectroscopic surveys. Application to 246 WR stars located in the field, permits us to map their Galactic distribution. As anticipated, WR stars generally lie in the thin disk (∼40 pc half width at half maximum) between Galactocentric radii 3.5-10 kpc, in accordance with other star formation tracers. We highlight 12 WR stars located at vertical distances of 300 pc from the midplane. Analysis of the radial variation in WR subtypes exposes a ubiquitously higher N W C /N W N ratio than predicted by stellar evolutionary models accounting for stellar rotation. Models for non-rotating stars or accounting for close binary evolution are more consistent with observations. We consolidate information acquired about the known WR content of the Milky Way to build a simple model of the complete population. We derive observable quantities over a range of wavelengths, allowing us to estimate a total number of 1200 +300 −100 Galactic WR stars, implying an average duration of ∼ 0.25 Myr for the WR phase at the current Milky Way star formation rate. Of relevance to future spectroscopic surveys, we use this model WR population to predict follow-up spectroscopy to K S ≃ 13 mag will be necessary to identify 95% of Galactic WR stars. We anticipate that ESA's Gaia mission will make few additional WR star discoveries via low-resolution spectroscopy, though will significantly refine existing distance determinations. Appendix A provides a complete inventory of 322 Galactic WR stars discovered since the VIIth catalogue (313 including Annex), including a revised nomenclature scheme.

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“…There are no correlations between the two emission components in both the EWs and line widths, indicating they may originate from different physical processes. According to the criteria for distinguishing accretors and non-accretors using FW Hα,10% and EW of Hα in Fang et al (2009Fang et al ( , 2013a, the narrow Hα emission component could be mainly related to the chromospheric activity, while the broad one should be due to the accretion activity.…”

Section: Decomposition Of the Hα And Hβ Line Profilesmentioning

confidence: 99%

GW Orionis: Inner disk readjustments in a triple system

Fang

Sicilia‐Aguilar

Roccatagliata

et al. 2014

A&A

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Context. Disks are expected to dissipate quickly in binary or multiple systems. Investigating such systems can improve our knowledge of the disk dispersal. The triple system GW Ori, still harboring a massive disk, is an excellent target. Aims. We study the young stellar system GW Ori, concentrating on its accretion, wind activity and disk properties. Methods. We use high-resolution optical spectra of GW Ori to do spectral classification and derive the radial velocities (RV). We analyze the wind and accretion activity using the emission lines in the spectra. We also use U-band photometry, which has been collected from the literature, to study the accretion variability of GW Ori. We characterize the disk properties of GW Ori by modeling its spectral energy distribution (SED).Results. By comparing our data to the synthetical spectra, we classify GW Ori as a G8 star. Based on the RVs derived from the optical spectra, we confirm the previous result as a close companion in GW Ori with a period of ∼242 days and an orbital semi-major axis of ∼1 AU. The RV residuals after the subtraction of the orbital solution with the equivalent widths (EW) of accretion-related emission lines vary with periods of 5−6.7 days during short-time intervals, which are caused by the rotational modulation. The Hα and Hβ line profiles of GW Ori can be decomposed in two central-peaked emission components and one blue-shifted absorption component. The blue-shifted absorption components are due to a disk wind modulated by the orbital motion of the close companion. Therefore, the systems like GW Ori can be used to study the extent of disk winds. We find that the accretion rates of GW Ori are rather constant but can occasionally be enhanced by a factor of 2−3. We reproduce the SED of GW Ori by using disk models with gaps ∼25−55 AU in size. A small population of tiny dust particles within the gap produces the excess emission at near-infrared bands and the strong and sharp silicate feature at 10 μm. The SED of GW Ori exhibits dramatic changes on timescales of ∼20 yr in the near-infrared bands, which can be explained as the change in the amount and distribution of small dust grains in the gap. We collect a sample of binary/multiple systems with disks in the literature and find a strong positive correlation between their gap sizes and separations from the primaries to companions, which is generally consistent with the prediction from the theory.

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Star formation and disk properties in Pismis 24

Cited by 86 publications

References 100 publications

Young open clusters in the Galactic star forming region NGC 6357

Young open clusters in the Galactic star forming region NGC 6357

Spatial distribution of Galactic Wolf–Rayet stars and implications for the global population

GW Orionis: Inner disk readjustments in a triple system

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