IRS SCAN-MAPPING OF THE WASP-WAIST NEBULA (IRAS 16253-2429). I. DERIVATION OF SHOCK CONDITIONS FROM H{sub 2} EMISSION AND DISCOVERY OF 11.3 {mu}m PAH ABSORPTION

Journal Article · Wed Sep 01 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/720/1/64· OSTI ID:21460156

Barsony, Mary ^[1]; Wolf-Chase, Grace A ^[2]; Ciardi, David R ^[3]; O'Linger, JoAnn ^[4]

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1. Department of Physics and Astronomy, San Francisco State University, 1600 Holloway Drive, San Francisco, CA 94132 (United States)
2. Astronomy Department, Adler Planetarium, 1300 South Lake Shore Drive, Chicago, IL 60605 (United States)
3. NASA Exoplanet Science Institute/Caltech, 770 South Wilson Avenue, MS 100-22, Pasadena, CA 91125 (United States)
4. Spitzer Science Center, California Institute of Technology MS 314-6, Pasadena, CA 91125 (United States)

The outflow driven by the Class 0 protostar, IRAS 16253-2429, is associated with bipolar cavities visible in scattered mid-infrared light, which we refer to as the Wasp-Waist Nebula. InfraRed Spectometer (IRS) scan mapping with the Spitzer Space Telescope of a {approx}1' x 2' area centered on the protostar was carried out. The outflow is imaged in six pure rotational (0-0 S(2) through 0-0 S(7)) H{sub 2} lines, revealing a distinct, S-shaped morphology in all maps. A source map in the 11.3 {mu}m polycyclic aromatic hydrocarbon (PAH) feature is presented in which the protostellar envelope appears in absorption. This is the first detection of absorption in the 11.3 {mu}m PAH feature. Spatially resolved excitation analysis of positions in the blue- and redshifted outflow lobes, with extinction-corrections determined from archival Spitzer 8 {mu}m imaging, shows remarkably constant temperatures of {approx}1000 K in the shocked gas. The radiated luminosity in the observed H{sub 2} transitions is found to be 1.94 {+-} 0.05 x 10{sup -5} L{sub sun} in the redshifted lobe and 1.86 {+-} 0.04 x 10{sup -5} L{sub sun} in the blueshifted lobe. These values are comparable to the mechanical luminosity of the flow. By contrast, the mass of hot (T {approx} 1000 K) H{sub 2} gas is 7.95 {+-} 0.19 x 10{sup -7} M{sub sun} in the redshifted lobe and 5.78 {+-} 0.17 x 10{sup -7} M{sub sun} in the blueshifted lobe. This is just a tiny fraction, of order 10{sup -3}, of the gas in the cold (30 K), swept-up gas mass derived from millimeter CO observations. The H{sub 2} ortho/para ratio of 3:1 found at all mapped points in this flow suggests previous passages of shocks through the gas. Comparison of the H{sub 2} data with detailed shock models of Wilgenbus et al. shows the emitting gas is passing through Jump (J-type) shocks. Pre-shock densities of 10{sup 4} cm{sup -3{<=}} n {sub H{<=}} 10{sup 5} cm{sup -3} are inferred for the redshifted lobe and n {sub H{<=}} 10{sup 3} cm{sup -3} for the blueshifted lobe. Shock velocities are 5 km s{sup -1} {<=} v{sub s} {<=} 10 km s{sup -1} for the redshifted gas and v{sub s} = 10 km s{sup -1} for the blueshifted gas. Initial transverse (to the shock) magnetic field strengths for the redshifted lobe are in the range 10-32 {mu}G, and just 3 {mu}G for the blueshifted lobe. A cookbook for using the CUBISM contributed software for IRS spectral mapping data is presented in the Appendix.

• OSTI ID: 21460156
• Journal Information: Astrophysical Journal, Vol. 720, Issue 1; Other Information: DOI: 10.1088/0004-637X/720/1/64; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABSORPTION
COMPUTER CODES
HYDROGEN
LUMINOSITY
MAGNETIC FIELDS
NEBULAE
POLYCYCLIC AROMATIC HYDROCARBONS
PROTOSTARS
STARS
TELESCOPES
WASPS
ANIMALS
AROMATICS
ARTHROPODS
ELEMENTS
HYDROCARBONS
HYMENOPTERA
INSECTS
INVERTEBRATES
NONMETALS
OPTICAL PROPERTIES
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
SORPTION