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Session 92 - Very Young Stars, T-Tauri Stars, H-H Objects.
Oral session, Friday, January 09
Lincoln,
We present HST NICMOS observations of the circumstellar nebulosity near the Taurus embedded young stellar objects IRAS04302+2247 and IRAS04248+2612. Images of these sources were obtained using the broad-band filters F110W, F160W, 187W, and F205W of Camera 2. Comparison of these near infrared images with existing WFPC2 data and model reflection nebulae constrain the circumstellar density distribution in these systems.
IRAS04302+2247 is one of the most striking examples of an edge-on circumstellar disk/envelope system. This Class I source shows bipolar reflection nebulae separated by a central dark absorption lane about 700 AU in diameter which obscures the central star at all observed wavelengths. This system is generally similar in aspect to the WFPC2 images of HH 30's edge-on circumstellar disk. However, IRAS04302+2247 differs from HH 30 in several important respects. First, the scattered light distribution of the IRAS source is more patchy and irregular, suggesting that the nebula traces both the disk and envelope components of the circumstellar matter. Second, the dust lane is considerably thicker than in the case of HH 30. This is consistent with a pressure-supported disk whose mass is many times greater than that of HH 30. Finally, the absorption lane of IRAS04302+2247 is relatively constant in thickness across its entire radial extent.
NICMOS images of IRAS04248+2612 (HH 31 IRS) reveal that this Herbig-Haro object exciting star is a previously unknown binary surrounded by complex bipolar nebulosity. The nebula is not crossed by a dust lane; however, the base of the outflow cavity is clearly pinched adjacent to the binary. The improved visibility of both stars in the near-IR indicates that they are being viewed through a considerable amount of circumstellar extinction.
