Astronomy and Astrophysics – Astronomy
Scientific paper
Oct 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998apj...505..756t&link_type=abstract
The Astrophysical Journal, Volume 505, Issue 2, pp. 756-765.
Astronomy and Astrophysics
Astronomy
64
Ism: H Ii Regions, Ism: Individual: Ngc Number: Ngc 2071, Ism: Jets And Outflows, Masers, Stars: Formation
Scientific paper
We have observed simultaneously the 1.3 cm continuum and H_2O maser emission toward the core of the star-forming region NGC 2071 using the Very Large Array in its A configuration. Two 1.3 cm continuum sources have been detected in the region, coinciding with the infrared sources IRS 1 and IRS 3, respectively. The radio emission in IRS 3 is consistent with an ionized thermal bipolar radio jet. Two clusters of H_2O maser spots are detected, one associated with IRS 1 (22 spots) and the other one associated with IRS 3 (13 spots). The H_2O maser distribution in IRS 1 seems to be tracing at scales of 300 AU the larger scale H_2 outflow observed at a few thousands of AU from the exciting source. On the other hand, the H_2O masers in IRS 3 are distributed as an apparent disk of ~=0.05" (~=20 AU) radius, oriented almost perpendicular to the major axis of the radio jet. There is a clear velocity gradient (~=0.35 km s^-1 AU^-1) along the major axis of the H_2O maser distribution, which can be gravitationally bound by a central mass of ~=1 M_&sun;. These results, together with the low-mass and early evolutionary stage of IRS 3, suggest that masers around this source are tracing a rotating proto-planetary disk within a proto-solar-like system. This represents direct kinematic evidence of the smallest rotating circumstellar disk ever observed around a young stellar object (YSO). We discuss the dichotomy of H_2O masers tracing either outflows or disks around YSOs, based on the evolutionary scheme proposed in our earlier work. We suggested that systems in which H_2O masers trace disks are less evolved than those in which masers trace outflows. In this scheme, IRS 3 would then represent a relatively less evolved object than IRS 1. This prediction is consistent with independent infrared observations showing that IRS 3 is at an earlier phase of evolution.
Anglada Guillem
Curiel Salvador
Gomez Jose F.
Ho Paul T. P.
Rodriguez Luis F.
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