Resolving the shocked gas in HH 54 with Herschel. CO line mapping at high spatial and spectral resolution
Journal article, 2014

Context. The HH 54 shock is a Herbig-Haro object, located in the nearby Chamaeleon II cloud. Observed CO line profiles are due to a complex distribution in density, temperature, velocity, and geometry. Aims: Resolving the HH 54 shock wave in the far-infrared (FIR) cooling lines of CO constrain the kinematics, morphology, and physical conditions of the shocked region. Methods: We used the PACS and SPIRE instruments on board the Herschel space observatory to map the full FIR spectrum in a region covering the HH 54 shock wave. Complementary Herschel-HIFI, APEX, and Spitzer data are used in the analysis as well. The observed features in the line profiles are reproduced using a 3D radiative transfer model of a bow-shock, constructed with the Line Modeling Engine code (LIME). Results: The FIR emission is confined to the HH 54 region and a coherent displacement of the location of the emission maximum of CO with increasing J is observed. The peak positions of the high-J CO lines are shifted upstream from the lower J CO lines and coincide with the position of the spectral feature identified previously in CO (10-9) profiles with HIFI. This indicates a hotter molecular component in the upstream gas with distinct dynamics. The coherent displacement with increasing J for CO is consistent with a scenario where IRAS12500 - 7658 is the exciting source of the flow, and the 180 K bow-shock is accompanied by a hot (800 K) molecular component located upstream from the apex of the shock and blueshifted by -7 km s-1. The spatial proximity of this knot to the peaks of the atomic fine-structure emission lines observed with Spitzer and PACS ([O i]63, 145 mum) suggests that it may be associated with the dissociative shock as the jet impacts slower moving gas in the HH 54 bow-shock. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

molecules

outflows

interstellar matter

jets

shocks

Herbig-Haro Objects

Author

Per Bjerkeli

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

René Liseau

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

C. Brinch

Köbenhavns Universitet

Niels Bohr Institute

G. Olofsson

Stockholm University

G. Santangelo

Arcetri Astrophysical Observatory

Osservatorio Astronomico di Roma

S. Cabrit

LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres

M. Benedettini

Arcetri Astrophysical Observatory

John H Black

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

G. J. Herczeg

Peking University

Kay Justtanont

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

L. Kristensen

Harvard-Smithsonian Center for Astrophysics

B. Larsson

Stockholm University

B. Nisini

Osservatorio Astronomico di Roma

M. Tafalla

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 571 A90- 24789

Subject Categories

Astronomy, Astrophysics and Cosmology

Roots

Basic sciences

Infrastructure

Onsala Space Observatory

DOI

10.1051/0004-6361/201424789