Outflow forces of low mass embedded objects in Ophiuchus: a quantitative comparison of analysis methods

摘要

The outflow force of molecular bipolar outflows is a key parameter intheories of young stellar feedback on their surroundings. The focus of manyoutflow studies is the correlation between the outflow force, bolometricluminosity and envelope mass. However, it is difficult to combine the resultsof different studies in large evolutionary plots over many orders of magnitudedue to the range of data quality, analysis methods and corrections forobservational effects such as opacity and inclination. We aim to determine theoutflow force for a sample of low luminosity embedded sources. We will quantifythe influence of the analysis method and the assumptions entering thecalculation of the outflow force. We use the James Clerk Maxwell Telescope tomap 12CO J=3-2 over 2'x2' regions around 16 Class I sources of a well-definedsample in Ophiuchus at 15" resolution. The outflow force is then calculatedusing seven different methods differing e.g. in the use of intensity-weightedemission and correction factors for inclination. The results from the analysismethods differ from each other by up to a factor of 6, whereas observationalproperties and choices in the analysis procedure affect the outflow force by upto a factor of 4. For the sample of Class I objects, bipolar outflows aredetected around 13 sources including 5 new detections, where the threenon-detections are confused by nearby outflows from other sources. Whencombining outflow forces from different studies, a scatter by up to a factor of5 can be expected. Although the true outflow force remains unknown, theseparation method (separate calculation of dynamical time and momentum) isleast affected by the uncertain observational parameters. The correlationsbetween outflow force, bolometric luminosity and envelope mass are furtherconfirmed down to low luminosity sources.