Issue A&A Volume 506, Number 3, November II 2009 Page(s) 1183 - 1198 Section Interstellar and circumstellar matter DOI http://dx.doi.org/10.1051/0004-6361/200911845 Published online 27 August 2009

A&A 506, 1183-1198 (2009)
DOI: 10.1051/0004-6361/200911845

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

G. Busquet¹, Aina Palau^{1, 2}, R. Estalella¹, J. M. Girart³, G. Anglada⁴, and I. Sepúlveda<sup>1

1</sup>  Departament d'Astronomia i Meteorologia (IEEC-UB), Institut de Ciències del Cosmos, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Catalunya, Spain
    e-mail: gbusquet@am.ub.es
²  Centro de Astrobiología (CSIC-INTA), Laboratorio de Astrofísica Estelar y Exoplanetas, LAEFF campus, PO Box 78, 28691 Villanueva de la Cañada (Madrid), Spain
³  Institut de Ciències de l'Espai (CSIC-IEEC), Campus UAB, Facultat de Ciències, Torre C-5 parell, 08193 Bellaterra, Catalunya, Spain
⁴  Instituto de Astrofísica de Andalucía (CSIC), C/ Camino Bajo de Huétor 50, 18008, Granada, Spain

Received 13 February 2009 / Accepted 27 July 2009

Abstract
Aims. 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 J_N=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.

Key words: stars: formation -- ISM: individual objects: IRAS  00213+6530 -- ISM: clouds

© ESO 2009

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