Accretion and outflow activity in proto-brown dwarfs

Riaz, B. und Bally, J. (2021): Accretion and outflow activity in proto-brown dwarfs. In: Monthly Notices of the Royal Astronomical Society, Bd. 501, Nr. 3: S. 3781-3805

Abstract

We present a near-infrared study of accretion and outflow activity in six Class 0/I proto-brown dwarfs (proto-BDs) using VLT/SINFONI spectroscopy and spectroimaging observations. The spectra show emission in several [Feii] and H-2 lines associated with jet/outflow activity, and in the accretion diagnostics of Pa beta and Br gamma lines. The peak velocities of the [Feii] lines (>100 km s(-1)) are higher than the H-2 lines. The Class 0 proto-BDs show strong emission in the H-2 lines but the [Feii] lines are undetected, while the Class I objects show emission in both [Feii] and H-2 lines, suggesting an evolutionary trend in the jets from a molecular to an ionic composition. Extended emission with knots is seen in the [Feii] and H-2 spectroimages for three proto-BDs, while the rest show compact morphologies with a peak on-source. The accretion rates for the proto-BDs span the range of (2 x 10(-6)-2 x 10(-8)) M-circle dot yr(-1), while the mass-loss rates are in the range of (4 x 10(-8)-5 x 10(-9)) M-circle dot yr(-1). These rates are within the range measured for low-mass protostars and higher than Class II brown dwarfs. We find a similar range in the jet efficiency for proto-BDs as measured in protostars. We have performed a study of the Brackett decrement from the Br 7-19 lines detected in the proto-BDs. The upper Brackett lines of Br 13-19 are only detected in the earlier stage systems. The ratios of the different Brackett lines with respect to the Br gamma line intensity are consistent with the ratios expected from Case B recombination.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Physik
• Themengebiete: 500 Naturwissenschaften und Mathematik > 530 Physik
• ISSN: 0035-8711
• Sprache: Englisch