The Infrared Reflection Nebula around the Protostellar System in S140

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Session 41 -- Circumstellar Disks
Display presentation, Thursday, January 13, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[41.05] The Infrared Reflection Nebula around the Protostellar System in S140

Jesse Bregman, David Harker, Xander Tielens (NASA-Ames Reserch Center), David Rank, and Pasquale Temi (UCSC/UCO)

Using the Lick 3m telescope and an Amber Engineering 128x128 InSb array camera, we have imaged the protostellar region in S140 at 2.2, 3.1 and 3.45 microns to study the environment close to the protostar and its interaction with the surrounding molecular cloud. There is a region surrounding IRS 1 which has been cleared out by the wind from IRS 1. In front of IRS 1 and its associated cavity, we observe a low and nearly constant (tau(3.1 microns)=0.6) water ice band depth. However, outside of the cavity, the ice band depth steadily increases with increasing distance into the molecular cloud. Hence, we conclude that there is ice present in the molecular cloud but not in the dusty disk surrounding IRS 1. The ice depth observed around IRS 1 is due to water ice present in the foreground cloud.

Light from the nebula appears to become bluer with increasing distance from IRS 1. This observation can be explained if there is a dusty disk around IRS 1. Light is reddened as it passes through the disk, and appears bluest along the poles of the disk where the dust is the thinnest.

Observed 3.45-2.2 colors of the bluest regions implies a cool radiation field with a color temperature of 900-1200 K. Most likely, these cool temperatures are the result of reprocessing of the protostellar radiation field by dust close to the protostar.

The MRN grain distribution, used to model the ISM, can not sufficiently explain our observations. A larger grain size distribution produces better results in deriving temperatures based upon the observed color of the nebula.

Orientation of the disk around IRS 1 is not aligned with the CO outflows. The large scale structure observed in the CS, ammonia, and CO data are indicative of the interaction between the surrounding molecular cloud and the outflows generated by IRS1 rather than the geometry of the region close to the protostar.

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