RESOLVED RADIO EMISSION FROM MODELS OF PHOTOEVAPORATED DISKS AROUND MASSIVE YOUNG STARS

Journal Article · Sun May 20 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/751/1/63· OSTI ID:22037237

Avalos, Martin; Lizano, Susana ^[1]

---

1. Centro de Radioastronomia y Astrofisica, UNAM, Apartado Postal 3-72, 58089 Morelia, Michoacan (Mexico)

We study the radio continuum and thermal hydrogen radio recombination line (RRL) emission from photoevaporated disk wind models around massive young stars. We applied the models of Lugo and coworkers to the source MWC 349A. The resolved synthetic radio continuum maps reproduce the observed hourglass morphology at low frequency but are more flattened than the observations at high frequency because the density in the model decreases too fast. These photoevaporated wind models naturally produce RRLs with FWHM {Delta}v {approx} 60 km s{sup -1}. Nevertheless, recent H66{alpha} line observations of MWC 349A by Loinard and Rodriguez have an FWHM {Delta}v {approx} 89 km s{sup -1}. We propose that such wide lines could be produced by an extra magnetocentrifugal acceleration of the flow due to a poloidal magnetic field anchored in the disk. Such fields could also prevent the flow divergence and the fast density drop of the photoevaporated disk wind model. To mimic this effect we include in this model a large non-thermal velocity dispersion {sigma}{sub nt} {approx} 70 km s{sup -1}. The width of the RRLs of this modified model increases with quantum number. This is in contrast with the observed H76{alpha} and H92{alpha} lines which are narrower than the H66{alpha} line. We argue that the low-frequency observations could have suffered from insufficient bandwidth and that new measurements of these lines would be very valuable to constrain the models. Finally, the resolved H66{alpha} and H53{alpha} line emission maps show the velocity asymmetry expected from flow rotation.

• OSTI ID: 22037237
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 751; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
ASTRONOMY
ASTROPHYSICS
ASYMMETRY
COSMIC RADIO SOURCES
GIANT STARS
HYDRODYNAMICS
HYDROGEN
MAGNETIC FIELDS
MORPHOLOGY
PHOTON EMISSION
ROTATION
STELLAR WINDS
VELOCITY