A Sensitive Survey for Water Maser Emission Toward Bok Globules Using the Robledo 70 m Antenna

We report the most sensitive water maser survey towards Bok globules to date,using NASA's 70m antenna in Robledo de Chavela (Spain). We observed 207positions within the CB catalog with a higher probability of harboring a youngstar, using as selection criteria the presence of radio continuum emission(from submillimeter to centimeter wavelengths), geometrical centers ofmolecular outflows, peaks in maps of high-density gas tracers (NH3 or CS), andIRAS point sources. We have obtained 7 maser detections, 6 of which (in CB 34,CB 54, CB 65, CB 101, CB 199, and CB 232) are reported for the first time here.Most of the water masers we detected are likely to be associated with youngstellar objects (YSOs), except for CB 101 (probably an evolved object) and CB65 (uncertain nature). The water maser in CB 199 shows a relatively high shift(~30 km/s) of its velocity centroid with respect to the cloud velocity, whichis unusual for low-mass YSOs. We speculate that high-velocity masers in thiskind of object could be related with episodes of energetic mass-loss in closebinaries. Alternatively, the maser in CB 199 could be pumped by aprotoplanetary or a young planetary nebula. CB 232 is the smallest Bok globule(~0.6 pc) known to be associated with water maser emission, although it wouldbe superseded by the cases of CB 65 (~0.3 pc) and CB 199 (~0.5 pc) if theirassociation with YSOs is confirmed. All our selection criteria havestatistically compatible detection rates, except for IRAS sources, which tendto be a somewhat worse predictor for the presence of maser emission.Comment: 42 pages, 7 figures. Accepted by The Astronomical Journal. Corrected typos in Tables 1 &