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Register a new userProper Motions of Thermal Radio Sources near HH 7-11 in the NGC 1333 Star Forming Region
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Added by
Carlos Carrasco-Gonz\\'alez
Publication date
2008
fields
Physics
and research's language is
English
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Star forming regions are expected to show linear proper motions due to the relative motion of the Sun with respect to the region. These proper motions appear superposed to the proper motions expected in features associated with mass ejection from the young stellar objects embedded in them. Therefore, it is necessary to have a good knowledge of the proper motions of the region as a whole in order to correctly interpret the motions associated with mass ejection. In this paper we present the first direct measurement of proper motions of the NGC 1333 star forming region. This region harbors one of the most studied Herbig-Haro systems, HH 7-11, whose exciting source remains unclear. Using VLA A configuration data at 3.6 cm taken over 10 years, we have been able to measure the absolute proper motions of four thermal sources embedded in NGC 1333. From our results we have derived the mean proper motions of the NGC 1333 star forming region to be mu(alpha)cos(delta) = 9 +- 1 mas/yr and mu(delta) = -10 +- 2 mas/yr. In this paper, we also discuss the possible implications of our results in the identification of the outflow exciting sources.
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We present absolute astrometry of four radio sources in the Becklin-Neugebauer/Kleinman-Low (BN/KL) region, derived from archival data (taken in 1991, 1995, and 2000) as well as from new observations (taken in 2006). All data consist of 3.6 cm continuum emission and were taken with the Very Large Array in its highest angular resolution A configuration. We confirm the large proper motions of the BN object, the radio source I (GMR I) and the radio counterpart of the infrared source n (Orion-n), with values from 15 to 26 km/s. The three sources are receding from a point between them from where they seem to have been ejected about 500 years ago, probably via the disintegration of a multiple stellar system. We present simulations of very compact stellar groups that provide a plausible dynamical scenario for the observations. The radio source Orion-n appeared as a double in the first three epochs, but as single in 2006. We discuss this morphological change. The fourth source in the region, GMR D, shows no statistically significant proper motions. We also present new, accurate relative astrometry between BN and radio source I that restrict possible dynamical scenarios for the region. During the 2006 observations, the radio source GMR A, located about 1 to the NW of the BN/KL region, exhibited an increase in its flux density of a factor of ~3.5 over a timescale of one hour. This rapid variability at cm wavelengths is similar to that previously found during a flare at millimeter wavelengths that took place in 2003.
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