Three intermediate-mass young stellar objects with different properties emerging from the same natal cloud in IRAS 00117+6412

Abstract

Aims. Our main aim is to study the influence of the initial conditions of a cloud in the intermediate/high-mass star formation process. Methods. We observed with the VLA, PdBI, and SMA the centimeter and millimeter continuum, N 2 H + (1-0), and CO (2-1) emission associated with a dusty cloud harboring a nascent cluster with intermediate-mass protostars.Results. At centimeter wavelengths we found a strong source, tracing a UCH ii region, at the eastern edge of the dusty cloud, with a shell-like structure, and with the near-infrared counterpart falling in the center of the shell. This is presumably the most massive source of the forming cluster. About 15 to the west of the UCH ii region and well embedded in the dusty cloud, we detected a strong millimeter source, MM1, associated with centimeter and near-infrared emission. MM1 seems to be driving a prominent high-velocity CO bipolar outflow elongated in the northeast-southwest direction, and is embedded in a ridge of dense gas traced by N 2 H + , elongated roughly in the same direction as the outflow. We estimated that MM1 is an intermediate-mass source in the Class 0/I phase. About 15 to the south of MM1, and still more deeply embedded in the dusty cloud, we detected a compact millimeter source, MM2, with neither centimeter nor near-infrared emission, but with water maser emission. MM2 is associated with a clump of N 2 H + , whose kinematics reveal a clear velocity gradient and additionally we found signposts of infall motions. MM2, being deeply embedded within the dusty cloud, with an associated water maser but no hints of CO outflow emission, is an intriguing object, presumably of intermediate mass.Conclusions. The UCH ii region is found at the border of a dusty cloud which is currently undergoing active star formation. Two intermediate-mass protostars in the dusty cloud seem to have formed after the UCH ii region and have different properties related to the outflow phenomenon. Thus, a single cloud with similar dust emission and similar dense gas column densities seems to be forming objects with different properties, suggesting that the initial conditions in the cloud are not determining all the star formation process.

Ongoing star formation in the protocluster IRAS 22134+5834

“…the higher sensitivity of the PdBI is not the reason we do not detect the 1.3 mm counterparts of these cores. Following the method described in the appendix of Palau et al (2010), we estimated that the largest structure from the shortest baselines of our observations that our PdBI observations could recover is ∼9.5 , while for the SMA observation it is ∼5.7 . Thus the relatively smooth distributed MM2, MM4, and MM6 were filtered out by the SMA observations.…”

Dense gas in IRAS 20343+4129: an ultracompact H ii region caught in the act of creating a cavity

“… c Largest angular scale (at half power) detectable by the interferometer, estimated from the minimum baseline of the array configuration, and following the appendix in Palau et al (2010). For the lines observed in C‐ and D‐configuration, this refers to the merged uv coverage. …”

H Ii Regions, Embedded Protostars, and Starless Cores in Sharpless 2-157

“…For example, Palau et al (2007) found a cluster of young stellar objects in the ultra-compact H ii region IRAS 20293+3952 with a similar range of infrared-millimeter colors as found here. Although we do not discuss spectral line observations here, these provide many additional ways to delineate evolutionary stages, through signatures of masers, hot and cold core chemistry, core collapse, and protostellar outflows (Beuther et al 2007;Fontani et al 2009;Brogan et al 2009Brogan et al , 2011Palau et al 2010;Wang et al 2011).…”