AAS 201st Meeting, January, 2003
Session 136. Star Formation Young Stars
Oral, Thursday, January 9, 2003, 2:00-3:30pm, 606-607

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[136.06] Testing the Circumstellar Disk Hypothesis: A Search for Outflows from Young Massive YSOs with Linearly Distributed Methanol Masers

J.M. De Buizer (Cerro Tololo Inter-American Observatory)

I present here results from a small-scale survey searching for outflows using near-infrared imaging. Targets were chosen from a list of massive YSOs found to contain methanol masers in linear distributions. Presently, it is a widely held belief that these types of methanol masers are found in (and delineate) circumstellar accretion disks around young massive stars. If this scenario is correct, one could try to directly image the accretion disks at the location of these linearly distributed methanol masers. However, despite many recent attempts aimed at imaging these disks, there exist no confirmed accretion disks around any of these sources, mainly due to problems of obscuration, distance, and crowding. Another way to test the disk hypothesis is to search for outflows perpendicular to the methanol maser distributions. According to the standard star formation accretion model, if a star is actively accreting from a disk, it is also accompanied by an outflow perpendicular to that disk. The main objective of the survey presented here was to obtain wide-field near-infrared images of the sites of linearly distributed methanol masers using a narrow-band 2.122 micron filter. This filter is centered on the H2 v=1-0 S(1) line; a shock diagnostic that has been shown to successfully trace CO outflows from young stellar objects. Twenty-seven targets were imaged, and eighteen (2/3) were found with H2 emission. Contrary to what was expected, the vast majority of the targets were found to have sources of H2 emission distributed parallel, rather than perpendicular, to the lines of methanol masers. These results are inconsistent with the hypothesis that linearly distributed methanol masers exist in circumstellar disks around massive YSOs.

The author(s) of this abstract have provided an email address for comments about the abstract: jdebuizer@ctio.noao.edu

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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.