A possible far-ultraviolet flux-dependent core mass function in NGC 6357
arXiv:2102.05464 · doi:10.1051/0004-6361/202039506
Abstract
To derive the properties of the dense cores in the galactic star-forming complex NGC6357 and to investigate the effects of an intense far-UV radiation field on their properties, we mapped the region at 450 and 850 micron, and in the CO(3-2) line with the JCMT. We also made use of the Herschel Hi-GAL data at 70 and 160 micron. We used Gaussclumps to retrieve 686 compact cores embedded in the diffuse sub-mm emission and constructed their SED from 70 to 850 micron, from which we derived mass and temperature. The estimated mass completeness limit is ~5Mo. We divided the observed area in an 'active' region, exposed to the far-UV radiation from the more massive members of three star clusters (411 cores), and a 'quiescent' region, less affected by far-UV radiation (275 cores). We also attempted to select a sample of pre-stellar cores based on cross-correlation with 70 micron emission and red WISE point sources. Most of the cores above the mass completeness limit are likely to be gravitationally bound. The fraction of gas in dense cores is very low, 1.4%. We found a mass-size relation log(M/Mo) ~ (2.0-2.4) x log (D/arcsec), depending on the precise selection of the sample. The temperature distributions in the two sub-regions are clearly different, peaking at ~25K in the quiescent region and at ~35K in the active region. The core mass functions are different as well, at a 2sigma level, consistent with a Salpeter IMF in the quiescent region and flatter than that in the active region. The dense cores lying close to the HII regions are consistent with pre-existing cores being gradually engulfed by a PDR and photoevaporating. We attribute the different global properties of dense cores in the two sub-regions to the influence of the far-UV radiation field.
16 pages, 18 figures, 3 tables (1 only at CDS); accepted by Astronomy & Astrophysics
References in corpus (14)
- Cold Dark Clouds: The Initial Conditions for Star Formation
- SCUBA-2: iterative map-making with the Sub-Millimetre User Reduction Facility
- Identifying the Low Luminosity Population of Embedded Protostars in the c2d Observations of Clouds and Cores
- Do cloud-cloud collisions trigger high-mass star formation? I. Small cloud collisions
- Ionisation-induced star formation II: External irradiation of a turbulent molecular cloud
- The relationship between the prestellar core mass function and the stellar initial mass function
- Pismis 24-1: The Stellar Upper Mass Limit Preserved
- An X-ray Census of Young Stars in the Massive Southern Star-Forming Complex NGC 6357
- Photoevaporation of Jeans-unstable molecular clumps
- The effect of photoionising feedback on star formation in isolated and colliding clouds
- Young open clusters in the galactic star forming region NGC 6357
- GMC Collisions as Triggers of Star Formation. VI. Collision-Induced Turbulence
- The young stellar content of the giant HII regions M8, G333.6-0.2, and NGC6357 with VLT/KMOS
- Photoionising feedback and the star formation rates in galaxies