Shocked cloudlet model for herbig-haro objects

Journal Article · Tue Aug 01 04:00:00 EDT 1978 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/156321· OSTI ID:6879440

Schwartz, R D

The results of moderately high dispersion spectra of Herbig-Haro objects Nos. 1 and 2 are reported. Relative emission line intensities, radial velocities, and emission line widths have been measured for seven of the knots composing HH 2. A theoretical model is proposed in which a strong stellar wind from an embedded pre--main-sequence star produces shock waves upon interaction with small ambient cloudlets. Radiating gas from bow shocks formed aroung dense clouds can produce the salient features of most HH objects including their low excitation spectra, radial velocities, relative emission line widths between lower and higher excitation lines, luminosities, and variational time scales. For the knots composing HH 1 and HH 2, a characteristic stellar wind velocity of about 100 km s/sup -1/ and a mass loss rate of approx.10/sup -5/ to 10/sup -6/Msunyr/sup -1/ from the embedded source are required. The preshock stellar wind density of about 200 cm/sup -3/ at a distance of approx.10/sup 17/ cm from the star is expected to yield post--bow-shock conditions typical of HH 1 and HH 2. The results of detailed plane shock calculations performed independently by Raymond and Dopita for HH objects are employed to discuss the differences expected between bow shock and plane shock spectra. The required mass flow rates and acceleration time scale of the cloudlets indicate that HH objects are short-lived phenomena (approx.10/sup 3/yr). Polarization is associated with those objects which exhibit significant continuum, and it is suggested that these objects represent a later phase of evolution in which a dust envelope has been partially cleared from the star, permitting reflection of continuum from dust associated with the cloudlets.

• Research Organization: Department of Physics, University of Missouri, St. Louis
• OSTI ID: 6879440
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 223:3; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
EMISSION SPECTRA
FLUID FLOW
GAS FLOW
LINE WIDTHS
LUMINOSITY
NEBULAE
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIAL VELOCITY
SHOCK WAVES
SPECTRA
STARS
STELLAR WINDS
T TAURI STARS
THERMODYNAMICS
VARIABLE STARS
VELOCITY