Hubble Space Telescope Wide Field Planetary Camera 2 Observations of HH 1-2

HH 2 has an extremely complex structure, but on a feature-by-feature basis much of the physical structure of HH 2 can be understood, leading to a consistent overall description of the object. The HH 2 jet is currently encountering dense ambient gas. The working surface of the jet is seen as bright, high-ionization emission in the central region of the complex. This emission shows a clumpy appearance due largely to the short cooling lengths behind shocks driven into dense material. The larger bow shock accompanying the jet working surface can be traced as well. Flanking the working surface are several locations where a momentum-driven shell is fragmenting as a result of hydrodynamic and thermal instabilities that arise as it, too, runs into dense ambient material. The dense obstacle being encountered by HH 2 is localized. Fossil bow shocks and "splatter" from the jet can be observed moving around this obstacle on either side of HH 2, giving the object its "indented" appearance. As in HH 1, a broader wind accompanies the HH 2 jet. Interaction of this wind with ambient material is responsible for a number of features in HH 2, including the knot seen farthest from the outflow source.

[1]  Alan M. Watson,et al.  The On-Orbit Performance of WFPC2 , 1994 .

[2]  M. Cohen,et al.  The exciting star of Herbig-Haro object 1. , 1979 .

[3]  M. Mateo,et al.  An interpretation of observations of HH 1 in terms of a time-dependent bow-shock model , 1988 .

[4]  J. Solf,et al.  The kinematical and physical structure of HH 1 and HH 2 determined from high -resolution spectroscopy , 1985 .

[5]  J. Solf,et al.  The two-dimensional distribution of the velocity dispersion and the excitation in the complex Herbig-Haro object HH2 , 1992 .

[6]  B. Jones,et al.  Large proper motions of the Herbig-Haro objects HH 1 and HH 2. , 1981 .

[7]  T. Ray,et al.  Hubble Space Telescope Observations of Jets from Young Stars , 1996 .

[8]  Michael L. Norman,et al.  Numerical Simulations of Protostellar Jets with Nonequilibrium Cooling. III. Three-dimensional Results , 1994 .

[9]  A. Raga,et al.  Spatially resolved spectra of HH1 and Burnham's nebula in the range lambda of between about 3700 A and 10830 A , 1988 .

[10]  P. Hartigan,et al.  The Bow Shock and Mach Disk of HH 34 , 1992 .

[11]  K. Sellgren,et al.  Detection of radio continuum emission from Herbig-Haro objects 1 and 2 and from their central exciting source. , 1985 .

[12]  C. McKee,et al.  Theoretical models of interstellar shocks. I - Radiative transfer and UV precursors , 1979 .

[13]  P. Hartigan,et al.  Radiative Bow Shock Models of Herbig-Haro Objects , 1987 .

[14]  Michael L. Norman,et al.  Numerical simulations of protostellar jets with nonequilibrium cooling. II: Models of pulsed jets , 1993 .

[15]  D. Cox.  Theoretical structure and spectrum of a shock wave in the interstellar medium - The Cygnus Loop. , 1972 .

[16]  T. Ray,et al.  Near-infrared imaging of HH 1/2 in shocked molecular hydrogen and [Fe II] , 1994 .

[17]  Stefano Casertano,et al.  THE PHOTOMETRIC PERFORMANCE AND CALIBRATION OF WFPC2 , 1995 .

[18]  P. Ho,et al.  VLA Observations of the Herbig-Haro 1-2 System , 1990 .

[19]  L. Hartmann,et al.  A high-resolution study of Herbig-Haro objects 1 and 2 , 1984 .

[20]  B. Reipurth,et al.  A new Herbig-Haro flow in the HH 1-2 complex , 1993 .

[21]  J. Raymond.  Shock waves in the interstellar medium , 1979 .

[22]  P. Hartigan,et al.  Hubble Space Telescope Observations of the HH 47 Jet: Narrowband Images , 1996 .

[23]  T. Ray,et al.  HST Observations of Jets from Young Stars , 1996 .

[24]  A. Raga,et al.  The steady structure of a jet/cloud interaction — I. The case of a plane-parallel stratification , 1996 .

[25]  M. Mateo,et al.  New positions and intensities of the Herbig-Haro objects HH 1 and 2 , 1990 .

[26]  L. Drury,et al.  Non--LTE Excitation of H$_2$ in Magnetised Molecular Shocks , 1996, astro-ph/9601028.

[27]  A. Raga,et al.  The spatial intensity distribution of selected emission lines for Herbig-Haro 1 - Comparison between theory and observations , 1989 .

[28]  P. Garnavich,et al.  The Proper Motions of the Warm Molecular Hydrogen Gas in Herbig-Haro 1 , 1997 .

[29]  R. Mundt,et al.  Structure and Proper Motions in Herbig-Haro Objects 1 and 2 , 1994 .

[30]  K. Sellgren,et al.  An optical and infrared study of the region surrounding Herbig-Haro objects 1 and 2 , 1985 .

[31]  P. Hartigan,et al.  Hubble Space Telescope Images of the HH 111 Jet. , 1997 .

[32]  Alan M. Watson,et al.  Hubble Space Telescope Observations of the Disk and Jet of HH 30 , 1996 .