skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Angular Momentum in Disk Wind Revealed in the Young Star MWC 349A

Abstract

Disk winds are thought to play a critical role in star birth. As winds extract excess angular momentum from accretion disks, matter in the disk can be transported inward to the star to fuel mass growth. However, observational evidence of wind carrying angular momentum has been very limited. We present Submillimeter Array (SMA) observations of the young star MWC 349A in the H26 α and H30 α recombination lines. The high signal-to-noise ratios made possible by the maser emission process allow us to constrain the relative astrometry of the maser spots to milli-arcsecond precision. Previous observations of the H30 α line with the SMA and the Plateau de Bure interferometer (PdBI) showed that masers are distributed in the disk and wind. Our new high-resolution observations of the H26 α line reveal differences in spatial distribution from that of the H30 α line. H26 α line masers in the disk are excited in a thin annulus with a radius of about 25 au, while the H30 α line masers are formed in a slightly larger annulus with a radius of 30 au. This is consistent with expectations for maser excitation in the presence of an electron density variation of approximately Rmore » {sup −4}. In addition, the H30 α and H26 α line masers arise from different parts in the wind. This difference is also expected from maser theory. The wind component of both masers exhibits line-of-sight velocities that closely follow a Keplerian law. This result provides strong evidence that the disk wind extracts significant angular momentum, thereby facilitating mass accretion in the young star.« less

Authors:
; ; ;  [1]
  1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138 (United States)
Publication Date:
OSTI Identifier:
22661322
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 837; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; ANGULAR MOMENTUM; APPROXIMATIONS; ELECTRON DENSITY; EMISSION; FUELS; INTERFEROMETERS; MASERS; MASS; NOISE; PARTURITION; RECOMBINATION; RESOLUTION; SIGNAL-TO-NOISE RATIO; SPATIAL DISTRIBUTION; STARS; STELLAR WINDS; VELOCITY

Citation Formats

Zhang, Qizhou, Claus, Brian, Watson, Linda, and Moran, James, E-mail: qzhang@cfa.harvard.edu. Angular Momentum in Disk Wind Revealed in the Young Star MWC 349A. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA5EA9.
Zhang, Qizhou, Claus, Brian, Watson, Linda, & Moran, James, E-mail: qzhang@cfa.harvard.edu. Angular Momentum in Disk Wind Revealed in the Young Star MWC 349A. United States. doi:10.3847/1538-4357/AA5EA9.
Zhang, Qizhou, Claus, Brian, Watson, Linda, and Moran, James, E-mail: qzhang@cfa.harvard.edu. Wed . "Angular Momentum in Disk Wind Revealed in the Young Star MWC 349A". United States. doi:10.3847/1538-4357/AA5EA9.
@article{osti_22661322,
title = {Angular Momentum in Disk Wind Revealed in the Young Star MWC 349A},
author = {Zhang, Qizhou and Claus, Brian and Watson, Linda and Moran, James, E-mail: qzhang@cfa.harvard.edu},
abstractNote = {Disk winds are thought to play a critical role in star birth. As winds extract excess angular momentum from accretion disks, matter in the disk can be transported inward to the star to fuel mass growth. However, observational evidence of wind carrying angular momentum has been very limited. We present Submillimeter Array (SMA) observations of the young star MWC 349A in the H26 α and H30 α recombination lines. The high signal-to-noise ratios made possible by the maser emission process allow us to constrain the relative astrometry of the maser spots to milli-arcsecond precision. Previous observations of the H30 α line with the SMA and the Plateau de Bure interferometer (PdBI) showed that masers are distributed in the disk and wind. Our new high-resolution observations of the H26 α line reveal differences in spatial distribution from that of the H30 α line. H26 α line masers in the disk are excited in a thin annulus with a radius of about 25 au, while the H30 α line masers are formed in a slightly larger annulus with a radius of 30 au. This is consistent with expectations for maser excitation in the presence of an electron density variation of approximately R {sup −4}. In addition, the H30 α and H26 α line masers arise from different parts in the wind. This difference is also expected from maser theory. The wind component of both masers exhibits line-of-sight velocities that closely follow a Keplerian law. This result provides strong evidence that the disk wind extracts significant angular momentum, thereby facilitating mass accretion in the young star.},
doi = {10.3847/1538-4357/AA5EA9},
journal = {Astrophysical Journal},
number = 1,
volume = 837,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2017},
month = {Wed Mar 01 00:00:00 EST 2017}
}