Astronomy and Astrophysics, volume 602A, 77-77 (2017/6-1)
The earliest phases of high-mass star formation, as seen in NGC 6334 by Herschel-HOBYS.
TIGE J., MOTTE F., RUSSEIL D., ZAVAGNO A., HENNEMANN M., SCHNEIDER N., HILL T., NGUYEN LUONG Q., DI FRANCESCO J., BONTEMPS S., LOUVET F., DIDELON P., KONYVES V., ANDRE P., LEULEU G., BARDAGI J., ANDERSON L.D., ARZOUMANIAN D., BENEDETTINI M., BERNARD J.-P., ELIA D., FIGUEIRA M., KIRK J., MARTIN P.G., MINIER V., MOLINARI S., NONY T., PERSI P., PEZZUTO S., POLYCHRONI D., RAYNER T., RIVERA-INGRAHAM A., ROUSSEL H., RYGL K., SPINOGLIO L. and WHITE G.J.
Abstract (from CDS):
Aims. To constrain models of high-mass star formation, the Herschel-HOBYS key program aims at discovering massive dense cores (MDCs) able to host the high-mass analogs of low-mass prestellar cores, which have been searched for over the past decade. We here focus on NGC 6334, one of the best-studied HOBYS molecular cloud complexes.
Methods. We used Herschel/PACS and SPIRE 70-500µm images of the NGC 6334 complex complemented with (sub)millimeter and mid-infrared data. We built a complete procedure to extract ∼0.1pc dense cores with the getsources software, which simultaneously measures their far-infrared to millimeter fluxes. We carefully estimated the temperatures and masses of these dense cores from their spectral energy distributions (SEDs). We also identified the densest pc-scale cloud structures of NGC 6334, one 2pcx1pc ridge and two 0.8pcx0.8pc hubs, with volume-averaged densities of ∼105cm–3.
Results. A cross-correlation with high-mass star formation signposts suggests a mass threshold of 75M☉ for MDCs in NGC 6334. MDCs have temperatures of 9.5-40K, masses of 75-1000M☉, and densities of 1x105-7x107cm–3. Their mid-infrared emission is used to separate 6 IR-bright and 10 IR-quiet protostellar MDCs while their 70µm emission strength, with respect to fitted SEDs, helps identify 16 starless MDC candidates. The ability of the latter to host high-mass prestellar cores is investigated here and remains questionable. An increase in mass and density from the starless to the IR-quiet and IR-bright phases suggests that the protostars and MDCs simultaneously grow in mass. The statistical lifetimes of the high-mass prestellar and protostellar core phases, estimated to be 1-7x104yr and at most 3x105yr respectively, suggest a dynamical scenario of high-mass star formation.
Conclusions. The present study provides good mass estimates for a statistically significant sample, covering the earliest phases of high-mass star formation. High-mass prestellar cores may not exist in NGC 6334, favoring a scenario presented here, which simultaneously forms clouds, ridges, MDCs, and high-mass protostars.
© ESO, 2017
dust, extinction - ISM: clouds - stars: formation - submillimeter: ISM - stars: protostars - ISM: individual objects: NGC 6334 - ISM: individual objects: NGC 6334
VizieR on-line data:
<Available at CDS (J/A+A/602/A77): catalog.dat tanle3.dat list.dat fits/*>
Table A.1: HOBYS JHHMMSS.s+DDMMSS N=46.
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