Subaru Near-Infrared Multicolor Images of Class II Young Stellar Object, RNO 91

Abstract

Abstract We conducted subarcsecond near-infrared imaging observations of RNO 91 with CIAO (Coronagraphic Imager with Adaptive Optics) mounted on the 8.2 m Subaru telescope. We present our JHK band data along with optical images, which when considered together reveal a complex circumstellar structure. We examined the colors of associated nebulae and compared the geometry of the outflow/disk system suggested by our data with that already proposed on the basis of previous studies. Our K-band image shows bright circumstellar nebulosity detected within $\sim$2$^{\prime\prime}$ around the central source, while it is less conspicuous at shorter wavelengths. PA and the size of this red color nebulosity agree with those of the previously detected polarization disk. Agreements among these data indicate that this bright nebulosity region, which follows the reddening law, might be attributed to a disklike structure. At $J$ and optical wavelengths, several blue knotlike structures are detected around and beyond the bright circumstellar nebulosity. We suggest that these knotty reflection nebulae may represent disintegrating fragments of an infalling envelope. The three-color composite image has the appearance of arc-shaped nebulosity. We interpret these structures as being roots of a bipolar cavity opening toward the northeast and the southwest. The complex distribution of reflection nebulosity seen around RNO 91 appears to confirm the interpretation that this source is an object dispersing its molecular envelope while transitioning from protostar to T Tauri star.