High-resolution bispectrum speckle intererometry and speckle polarimetry of the southern outflow lobe of S140 IRS1
Some - perhaps all - newly formed stars go through a turbulent phase of adolescence in which they eject streams of gas that collide with the surrounding molecular cloud material. The figure below shows the first bispectrum speckle interferometry image of the young stellar object S140~IRS1 and its southern outflow. Radio interferometric observations proved that this outflow is in fact bipolar. The northern lobe shows redshifted emission and is thus pointing away from us. Consistently, the northern part of the outflow cavity is not visible at near infrared wavelengths. The observations suggest that S140 IRS1 is a massive young star surrounded by an optically thick circumstellar disk. The outflow perpendicular to this disk is clearing a polar cavity, which can be seen in scattered stellar light at the cavity walls.

Diffraction-limited bispectrum speckle interferometry and speckle polarimetry of the young bipolar outflow source S140 IRS1

D. Schertl, Y. Balega, T. Hannemann, K.-H. Hofmann, T. Preibisch, and G. Weigelt

Astronomy & Astrophysics 361, L29-L32 (2000)


Abstract

We present bispectrum speckle interferometry and speckle polarimetry of the deeply embedded infrared bipolar outflow source S140 IRS1, a massive protostellar object in the L1204 molecular cloud. Using the SAO 6m telescope, we obtained 280 mas resolution polarization maps of S140 IRS1 as well as a K-band image with diffraction-limited resolution lambda/D of 76 mas, which is the highest angular resolution image of a young outflow source ever obtained in the infrared. Our data suggest that the central source is marginally resolved with a FWHM diameter of approximately 20 mas (~20 AU). The most remarkable feature in our image is a bright extended and very clumpy structure pointing away from the central source in exactly the same direction as the blue-shifted CO outflow lobe. A centro-symmetric pattern of high polarization in this feature suggests that we see scattered light from the central source. We interprete this feature as the clumpy inner surface of a partially evacuated cavity in the circumstellar envelope around IRS1, which has been excavated by the strong outflow from IRS1.


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