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Low-mass protostars and dense cores in different evolutionary stages in IRAS  00213+6530

AutorBusquet, Gemma; Palau, Aina ; Estalella, Robert; Girart, Josep Miquel ; Sepúlveda, Inmaculada
Palabras claveStars: formation
ISM: individual objects: IRAS  00213+6530
ISM: clouds
Fecha de publicaciónago-2009
EditorEDP Sciences
CitaciónAstronomy and Astrophysics - Les Ulis 506(3): 1183-1198 (2009)
ResumenAims. The aim of this paper is to study with high angular resolution a dense core associated with a low-luminosity IRAS source, IRAS 00213+6530, in order to investigate whether low mass star formation is taking place in isolation.
Methods. We carried out observations at 1.2 mm with the IRAM 30 m telescope, and VLA observations in the continuum mode at 6 cm, 3.6 cm, 1.3 cm and 7 mm, together with H2O maser and NH3 lines toward IRAS 00213+6530. Additionally, we observed the CCS JN=21–10 transition, and H2O maser emission using the NASA 70 m antenna at Robledo de Chavela, Spain. We studied the nature of the centimeter and millimeter emission of the young stellar objects (YSOs) found in the region, and the physical properties of the dense gas and dust emission.
Results. The centimeter and millimeter continuum emission, together with the near infrared data from 2MASS allowed us to identify three YSOs, IRS 1, VLA 8A, and VLA 8B, with different radio and infrared properties, and which seem to be in different evolutionary stages. IRS 1, detected only in the infrared, is in the more advanced stage. On the other hand, VLA 8A, bright at centimeter and millimeter wavelengths, coincides with a near infrared 2MASS source, whereas VLA 8B has no infrared emission associated with it and is in the earliest evolutionary stage. The overall structure of the NH3 emission consists of three clouds. Two of these, MM1 and MM2, are associated with dust emission at millimeter wavelengths, while the southern cloud is only detected in NH3. The YSOs are embedded in MM1, where we found evidence of line broadening and temperature enhancements. On the other hand, the southern cloud and MM2 appear to be quiescent and starless. Concerning the 1.2 mm dust emission, we modeled the radial intensity profile of MM1. The model fits the data reasonably well, but it underestimates the intensity at small projected distances from the 1.2 mm peak, probably due to the presence of multiple YSOs embedded in the dusty envelope. There is a strong differentiation in the relative NH3 abundance with low values of ~ toward MM1, which harbors the YSOs, and high values, up to 10-6, toward the southern cloud and MM2, suggesting that these clouds could be in a young evolutionary stage.
Conclusions. IRAS 00213+6530 harbors a multiple system of low-mass protostars, indicating that star formation in this cloud is taking place in groups or clusters, rather than in isolation. The low-mass YSOs found in IRAS 00213+6530 are in different evolutionary stages, suggesting that star formation takes place in different episodes.
Descripción17 pages, 13 tables, 12 figures, 1 appendix.-- Pre-print archive.
Versión del editorhttp://dx.doi.org/10.1051/0004-6361/200911845
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