SIMBAD references

We describe a deep narrowband [S II] imaging survey of ∼0.7 deg² covering the ρ Ophiuchi cloud core (L1688). We detect seven new jet/Herbig-Haro (HH) objects in our survey, of which three are new detections and four confirm candidates from a recent survey by Wilking et al. Together with the five previously known objects, this brings the total to 12 known jet/HH objects in the cloud. In addition to this, we propose six new candidate HH objects. The most likely sources to power the new jet/HH objects appear to be optically visible stars; however, a conclusive association between the HH objects and pre-main-sequence stars is difficult, as several candidate driving sources lie in close vicinity of the new knots. Practically all of the HH objects are located on the perimeter of the cloud. The lack of optical emission toward the center of the cloud and the high spatial concentration of the youngest protostars toward the densest regions strongly suggest that jets inside the cloud are obscured from our view at optical wavelengths. A near-infrared H₂ survey is required to penetrate into the cloud and to study the outflow activity in this extremely active star-forming region.