2007A&A...466..579G

To study the Herbig-Haro (HH) flows in L1641N, an active star formation region in the southern part of the Orion GMC and one of the most densely populated regions of HH objects in the entire sky. By mapping the velocities of these HH objects, combined with mid-IR observations of the young stars, the major flows in the region and the corresponding outflow sources can be revealed. We have used the 2.56m Nordic Optical Telescope (NOT) to observe two deep fields in L1641N, selected on the basis of previous shock studies, using the 2.12µm transition of H₂ (and a K_S filter to sample the continuum) for a total exposure time of 4.6h (72min K_S) in the overlapping region. The resulting high-resolution mosaic (0.23'' pixel size, 0.75'' seeing) shows numerous new shocks and resolves many known shocks into multiple components. Using previous observations taken 9 yr earlier we calculate a proper motion map and combine this with Spitzer 24µm observations of the embedded young stars. The combined H₂ mosaic shows many new shocks and faint structures in the HH flows. From the proper motion map we find that most HH objects belong to two major bi-polar HH flows, the large-scale roughly North-South oriented flow from central L1641N and a previously unseen HH flow in eastern L1641N. Combining the tangential velocity map with the mid-IR Spitzer images, two very likely outflow sources are found. The outflow source of the eastern flow, L1641N-172, is found to be the currently brightest mid-IR source in L1641N and seem to have brightened considerably during the past 20yr. We make the first detection of this source in the near-IR (K_S) and also find a near-IR reflection nebula pointing at the source, probably the illuminated walls of a cone-shaped cavity cleared out by the eastern lobe of the outflow. Extending a line from the eastern outflow source along the proper motion vector we find that HH 301 and HH 302 (almost 1pc away) belong to this new HH flow.