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  1. OA@INAF
  2. PRODOTTI RICERCA INAF
  3. 1 CONTRIBUTI IN RIVISTE (Journal articles)
  4. 1.01 Articoli in rivista
Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12386/24450
Title: Globules and pillars in Cygnus X. I. Herschel far-infrared imaging of the Cygnus OB2 environment
Authors: Schneider, N.
Bontemps, S.
Motte, F.
Blazere, A.
André, Ph.
Anderson, L. D.
Arzoumanian, D.
Comerón, F.
Didelon, P.
Di Francesco, J.
Duarte-Cabral, A.
GUARCELLO, Mario Giuseppe 
Hennemann, M.
Hill, T.
Könyves, V.
Marston, A.
Minier, V.
RYGL, Kazi Lucie Jessica 
Röllig, M.
Roy, A.
SPINOGLIO, Luigi Giuseppe Maria 
Tremblin, P.
White, G. J.
Wright, N. J.
Issue Date: 2016
Journal: ASTRONOMY & ASTROPHYSICS 
Number: 591
First Page: A40
Abstract: The radiative feedback of massive stars on molecular clouds creates pillars, globules and other features at the interface between the H II region and molecular cloud. Optical and near-infrared observations from the ground as well as with the Hubble or Spitzer satellites have revealed numerous examples of such cloud structures. We present here Herschel far-infrared observations between 70 μm and 500 μm of the immediate environment of the rich Cygnus OB2 association, performed within the Herschel imaging survey of OB Young Stellar objects (HOBYS) program. All of the observed irradiated structures were detected based on their appearance at 70 μm, and have been classified as pillars, globules, evaporating gasous globules (EGGs), proplyd-like objects, and condensations. From the 70 μm and 160 μm flux maps, we derive the local far-ultraviolet (FUV) field on the photon dominated surfaces. In parallel, we use a census of the O-stars to estimate the overall FUV-field, that is 10^3-10^4 G0 (Habing field) close to the central OB cluster (within 10 pc) and decreases down to a few tens G0, in a distance of 50 pc. From a spectral energy distribution (SED) fit to the four longest Herschel wavelengths, we determine column density and temperature maps and derive masses, volume densities and surface densities for these structures. We find that the morphological classification corresponds to distinct physical properties. Pillars and globules are massive (~500 M☉) and large (equivalent radius r ~ 0.6 pc) structures, corresponding to what is defined as "clumps" for molecular clouds. EGGs and proplyd-likeobjects are smaller (r ~ 0.1 and 0.2 pc) and less massive (~10 and ~30 M☉). Cloud condensations are small (~0.1 pc), have an average mass of 35 M☉, are dense (~6 × 10^4 cm^-3), and can thus be described as molecular cloud "cores". All pillars and globules are oriented toward the Cyg OB2 association center and have the longest estimated photoevaporation lifetimes, a few million years, while all other features should survive less than a million years. These lifetimes are consistent with that found in simulations of turbulent, UV-illuminated clouds. We propose a tentative evolutionary scheme in which pillars can evolve into globules, which in turn then evolve into EGGs, condensations and proplyd-like objects. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
URI: http://hdl.handle.net/20.500.12386/24450
URL: https://arxiv.org/abs/1604.03967
https://www.aanda.org/articles/aa/abs/2016/07/aa28328-16/aa28328-16.html
ISSN: 0004-6361
DOI: 10.1051/0004-6361/201628328
Bibcode ADS: 2016A&A...591A..40S
Fulltext: open
Appears in Collections:1.01 Articoli in rivista

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