No abstract

Multiple optical outflows are known to exist in the vicinity of the active star formation region called Orion South (Orion-S). We have mapped the velocity of low-ionization features in the brightest part of the Orion Nebula, including Orion-S, and imaged the entire nebula with the Hubble Space Telescope. These new data, combined with recent high-resolution radio maps of outflows from the Orion-S region, allow us to trace the origin of the optical outflows. It is confirmed that HH 625 arises from the blueshifted lobe of the CO outflow from 136-359 in Orion-S, while it is likely that HH 507 arises from the blueshifted lobe of the SiO outflow from the nearby source 135-356. It is likely that redshifted lobes are deflected within the photon-dominated region behind the optical nebula. This leads to a possible identification of a new large shock to the southwest of Orion-S as being driven by the redshifted CO outflow arising from 137-408. The distant object HH 400 is seen to have two even further components, and these all are probably linked to either HH 203, HH 204, or HH 528. Distant shocks on the west side of the nebula may be related to HH 269. The sources of multiple bright, blueshifted Herbig-Haro objects (HH 202, HH 203, HH 204, HH 269, and HH 528) remain unidentified, in spite of earlier claimed identifications. Some of this lack of identification may arise from the fact that deflection in radial velocity can also produce a change in direction in the plane of the sky. The best way to resolve this open question is through improved tangential velocities of low-ionization features arising where the outflows first break out into the ionized nebula.

We study the line widths in the [O III]λ5007 and Hα lines for two groups of planetary nebulae in the Milky Way bulge based upon spectroscopy obtained at the Observatorio Astronómico Nacional in the Sierra San Pedro Mártir (OAN-SPM) using the Manchester Echelle Spectrograph. The first sample includes objects early in their evolution, having high Hβ luminosities, but [O III]λ5007/Hβ < 3. The second sample comprises objects late in their evolution, with He II λ4686/Hβ > 0.5. These planetary nebulae represent evolutionary phases preceeding and following those of the objects studied by . Our sample of planetary nebulae with weak [O III]λ5007 has a line width distribution similar to that of the expansion velocities of the envelopes of AGB stars, and shifted to systematically lower values as compared to the less evolved objects studied by . The sample with strong He II λ4686 has a line width distribution indistinguishable from that of the more evolved objects from , but a distribution in angular size that is systematically larger and so they are clearly more evolved. These data and those of form a homogeneous sample from a single Galactic population of planetary nebulae, from the earliest evolutionary stages until the cessation of nuclear burning in the central star. They confirm the long-standing predictions of hydrodynamical models of planetary nebulae, where the kinematics of the nebular shell are driven by the evolution of the central star.

High-dispersion echelle spectroscopy in optical forbidden lines of O 0 , S + , and S 2+ is used to construct velocity-resolved images and electron density maps of the inner region of the Orion nebula with a resolution of 10 km s −1 × 3 ′′ × 2 ′′ . Among the objects and regions revealed in this study are (1) the Diffuse Blue Layer: an extended layer of moderately blue-shifted, low-density, low-ionization emission in the southeast region of the nebula; (2) the Red Bay: a region to the east of the Trapezium where the usual correlation between velocity and ionization potential is very weak, and where the emitting layer is very thick; and (3) HH 873: a new redshifted jet to the southwest of the Trapezium.Note: A version of this paper with full-resolution figures can be obtained from http://www.ifront.org/wiki/Spectral_Mapping_Paper_I