Outflow Activity in the Brown Dwarf Mass Regime

• Applicant: Emma Whelan, Ph.D.
• Subject Area: Astrophysics and Astronomy
• Term: from 2013 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 252106471

Brown dwarfs (BDs) are the so-called “failed stars” which occupy the mass range between stars and planets. How BDs form is an open question in star formation theory. One idea is that they form in the same manner as young solar mass stars but that the formation processes are scaled down. To test this idea the properties of young BDs should be compared to the well-known properties of young stars. For example BDs have been found to accrete, to have accretion disks and to drive outflows. Since 2005 I have been leading a study to detect BD outflows and compare their properties to outflows driven by young solar mass stars. To date six such outflows have been observed.My work up until this point on BD outflow activity, has allowed me to identify the most efficient methods for the detecting these flows i.e. optical and sub-miilimetre imaging surveys, and to pin-point the key questions on which research should be focussed. In particular, early results suggest that BD outflows and more efficient that the outflows driven by young stars. The efficiency is defined as the ratio of the rate of mass outflow to mass accretion and this property has the potential to reveal the most about how BD and stellar outflows compare.The main objective of the project proposed here is to constrain the ratio of mass outflow to accretion in a statistically significant sample of young BDs and to make a comparison with leading outflow models. As only 6 outflows have been observed so far the first part of the project will concentrate on increasing the sample of BD outflows. This will be done through the analysis of two datasets. The first is an optical imaging survey of the Upper Scorpius star forming region and the second is a series of observations of the CO emission from a sample of 30 BDs. Once the larger sample of BD outflows is complete the spectroscopic data needed to constrain the efficiency of the outflows will be collected.This study of BD outflow activity is impactful and relevant to state-of-the-art astrophysical research. Firstly by investigating BD outflow activity, information pertinent to BD formation and evolution will be provided. This can give us a clearer idea of the place BDs occupy in the complete picture of star formation. A second motivation for investigating BD outflow activity is to better understand outflow mechanisms in general. The mechanisms responsible for protostellar outflows are seen in a large range of astrophysical objects from active galactic nuclei to BDs. Hence a better insight into outflow mechanisms will have repercussions for several astrophysical disciplines from extragalactic astronomy to planetary science.

• DFG Programme: Research Grants
• Participating Person: Dr. Matthias Stute