A multifrequency study of the active star-forming complex NGC 6357 - I. Interstellar structures linked to the open cluster Pis 24

Cappa, C. E.; Barbá, R. H.; Duronea, N. U.; Vasquez, J.; Arnal, E. M.; Goss, W. M.; Lajús, E. Fernández

doi:10.1111/j.1365-2966.2011.18902.x

Cited by 16 publications

(26 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As a sanity check, the LSR velocity and the expansion velocity of SFC 264 in G353 can be compared to the results of Cappa et al (2011), who find an expansion velocity ∼ 5−9 km s −1 which is in approximate agreement with the result quoted in this paper, 6.7 km s −1 . Using a photometric distance to the cluster Pismis 24, which appears to power the HII region, they find D = 2.5 kpc, substantially larger than our D = 0.9 kpc.…”

Section: Radial Velocity and Distance Uncertainties Due To Streaming supporting

confidence: 72%

Milky Way Star-Forming Complexes and the Turbulent Motion of the Galaxy's Molecular Gas

Lee

Murray

Rahman

2012

ApJ

View full text Add to dashboard Cite

We analyze Spitzer GLIMPSE, MSX, and WMAP images of the Milky Way to identify 8 micron and free-free sources in the Galaxy. Seventy-two of the eighty-eight WMAP sources have coverage in the GLIMPSE and MSX surveys suitable for identifying massive star forming complexes (SFC). We measure the ionizing luminosity functions of the SFCs and study their role in the turbulent motion of the Galaxy's molecular gas. We find a total Galactic free-free flux f ν = 46177.6 Jy; the 72 WMAP sources with full 8 micron coverage account for 34263.5 Jy (∼ 75%), with both measurements made at ν=94GHz (W band). We find a total of 280 SFCs, of which 168 have unique kinematic distances and free-free luminosities. We use a simple model for the radial distribution of star formation to estimate the free-free and ionizing luminosity for the sources lacking distance determinations. The total dust-corrected ionizing luminosity is Q = 2.9 ± 0.5 x 10 53 photons s −1 , which implies a galactic star formation rate oḟ M * = 1.2 ± 0.2 M ⊙ yr −1 . We present the (ionizing) luminosity function of the SFCs, and show that 24 sources emit half the ionizing luminosity of the Galaxy. The SFCs appear as bubbles in GLIMPSE or MSX images; the radial velocities associated with the bubble walls allow us to infer the expansion velocity of the bubbles. We calculate the kinetic luminosity of the bubble expansion and compare it to the turbulent luminosity of the inner molecular disk. SFCs emitting 80% of the total galactic free-free luminosity produce a kinetic luminosity equal to 65% of the turbulent luminosity in the inner molecular disk. This suggests that the expansion of the bubbles is a major driver of the turbulent motion of the inner Milky Way molecular gas.

show abstract

Section: Radial Velocity and Distance Uncertainties Due To Streaming supporting

confidence: 72%

Milky Way Star-Forming Complexes and the Turbulent Motion of the Galaxy's Molecular Gas

Lee

Murray

Rahman

2012

ApJ

View full text Add to dashboard Cite

show abstract

“…It is believed that the massive stars of this cluster are the main ionizing source responsible for the origin of the H ii region NGC 6357 (Lortet et al 1984;Bohigas et al 2004;Cappa et al 2011). Line observations of a molecular cloud associated with NGC 6357 showed that most of the molecular emission arises from the regions behind or to the north of Pismis 24, which indicates that the cluster is immersed in a blister-like H ii region viewed face-on (Massi et al 1997).…”

Section: Pismis 24mentioning

confidence: 99%

Search for OB stars running away from young star clusters

Gvaramadze

Kniazev

Kroupa

et al. 2011

A&A

View full text Add to dashboard Cite

Dynamical few-body encounters in the dense cores of young massive star clusters are responsible for the loss of a significant fraction of their massive stellar content. Some of the escaping (runaway) stars move through the ambient medium supersonically and can be revealed via detection of their bow shocks (visible in the infrared, optical or radio). In this paper, which is the second of a series of papers devoted to the search for OB stars running away from young ( < ∼ several Myr) Galactic clusters and OB associations, we present the results of the search for bow shocks around the star-forming region NGC 6357. Using the archival data of the Midcourse Space Experiment (MSX) satellite and the Spitzer Space Telescope, and the preliminary data release of the Wide-Field Infrared Survey Explorer (WISE), we discovered seven bow shocks, whose geometry is consistent with the possibility that they are generated by stars expelled from the young (∼1-2 Myr) star clusters, Pismis 24 and AH03 J1725-34.4, associated with NGC 6357. Two of the seven bow shocks are driven by the already known OB stars, HD 319881 and [N78] 34. Follow-up spectroscopy of three other bow-shockproducing stars showed that they are massive (O-type) stars as well, while the 2MASS photometry of the remaining two stars suggests that they could be B0 V stars, provided that both are located at the same distance as NGC 6357. Detection of numerous massive stars ejected from the very young clusters is consistent with the theoretical expectation that star clusters can effectively lose massive stars at the very beginning of their dynamical evolution (long before the second mechanism for production of runaway stars, based on a supernova explosion in a massive tight binary system, begins to operate) and lends strong support to the idea that probably all field OB stars have been dynamically ejected from their birth clusters. A by-product of our search for bow shocks around NGC 6357 is the detection of three circular shells typical of luminous blue variable and late WN-type Wolf-Rayet stars.

show abstract

“…The big shell is ∼60 in diameter (∼30 pc at 1.7 kpc) and is bordered by an outer shell of giant molecular clouds with LSR velocities in the range −12.5 to 0 km s −1 (Cappa et al 2011), The total estimated gas mass of the outer shell amounts to 1.4 × 10 5 M . If the whole molecular gas structure is part of a large bubble, then the gas velocity range suggests an expansion rate of the order of ∼10 km s −1 .…”

Section: Introductionmentioning

confidence: 99%

“…The O-type stars in Pismis 24 are the ionising sources of G353.2+0.9 (Bohigas et al 2004;Giannetti et al 2012). They are also responsible for the ionisation of the inner edge of shell A, originating a ring of Hii regions collectively referred to as G353.12+0.86 by Cappa et al (2011). noting the age discrepancy between the very massive members of Pismis 24 and the nearby (∼4 from Pismis 24) older WR93.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Young open clusters in the Galactic star forming region NGC 6357

Massi

Giannetti

Carlo

et al. 2014

A&A

View full text Add to dashboard Cite

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.

show abstract

A multifrequency study of the active star-forming complex NGC 6357 - I. Interstellar structures linked to the open cluster Pis 24

Cited by 16 publications

References 30 publications

Milky Way Star-Forming Complexes and the Turbulent Motion of the Galaxy's Molecular Gas

Milky Way Star-Forming Complexes and the Turbulent Motion of the Galaxy's Molecular Gas

Search for OB stars running away from young star clusters

Young open clusters in the Galactic star forming region NGC 6357

Contact Info

Product

Resources

About