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TOPIC: S140 IRS1

Blobrana

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Posts: 131433

Date: May 5 12:16 2015

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Title: Temperatures of dust and gas in S~140 Author: E. Koumpia, P.M. Harvey, V. Ossenkopf, F.F.S. van der Tak, B. Mookerjea, A. Fuente, C. Kramer n dense parts of interstellar clouds (> 10^5 cm^-3), dust & gas are expected to be in thermal equilibrium, being coupled via collisions. However, previous studies have shown that the temperatures of the dust & gas may remain decoupled even at higher densities. We study in detail the temperatures of dust & gas in the photon-dominated region S 140, especially around the deeply embedded infrared sources IRS 1-3 and at the ionisation front. We derive the dust temperature and column density by combining Herschel PACS continuum observations with SOFIA observations at 37 µm and SCUBA at 450 µm. We model these observations using greybody fits and the DUSTY radiative transfer code. For the gas part we use RADEX to model the CO 1-0, CO 2-1, 13CO 1-0 and C18O 1-0 emission lines mapped with the IRAM-30m over a 4' field. Around IRS 1-3, we use HIFI observations of single-points and cuts in CO 9-8, 13CO 10-9 and C18O 9-8 to constrain the amount of warm gas, using the best fitting dust model derived with DUSTY as input to the non-local radiative transfer model RATRAN. We find that the gas temperature around the infrared sources varies between 35 and 55K and that the gas is systematically warmer than the dust by ~5-15K despite the high gas density. In addition we observe an increase of the gas temperature from 30-35K in the surrounding up to 40-45K towards the ionisation front, most likely due to the UV radiation from the external star. Furthermore, detailed models of the temperature structure close to IRS 1 show that the gas is warmer and/or denser than what we model. Finally, modelling of the dust emission from the sub-mm peak SMM 1 constrains its luminosity to a few ~10^2 Lo. We conclude that the gas heating in the S 140 region is very efficient even at high densities, most likely due to the deep UV penetration from the embedded sources in a clumpy medium and/or oblique shocks. Read more (2581kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Feb 21 10:42 2012

S140 IRS1	Permalink

Title: First Science Results From SOFIA/FORCAST: Super-Resolution Imaging of the S140 Cluster at 37\micron Authors: Paul M. Harvey, Joseph D. Adams, Terry L. Herter, George Gull, Justin Schoenwald, Luke D. Keller, James M. De Buizer, William Vacca, William Reach, E. E. Becklin We present 37\micron\ imaging of the S140 complex of infrared sources centred on IRS1 made with the FORCAST camera on SOFIA. These observations are the longest wavelength imaging to resolve clearly the three main sources seen at shorter wavelengths, IRS 1, 2 and 3, and are nearly at the diffraction limit of the 2.5-m telescope. We also obtained a small number of images at 11 and 31\micron\ that are useful for flux measurement. Our images cover the area of several strong sub-mm sources seen in the area -- SMM 1, 2, and 3 -- that are not coincident with any mid-infrared sources and are not visible in our longer wavelength imaging either. Our new observations confirm previous estimates of the relative dust optical depth and source luminosity for the components in this likely cluster of early B stars. We also investigate the use of super-resolution to go beyond the basic diffraction limit in imaging on SOFIA and find that the van Cittert algorithm, together with the "multi-resolution" technique, provides excellent results. Read more (1831kb, PDF) __________________

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