High-resolution study of the young stellar objects in Mon R2 IRS 3

Abstract

We present a bispectrum speckle interferometry study of the embedded young stellar objects in Mon R2 IRS 3 in the near-infrared H and K bands. Our images with a resolution of 75 mas (cor 62 AU) show a close triple system surrounded by strong diffuse nebulosity and three additional infrared sources (K magnitudes ~ 11.8-13.7) within 3'' of the brightest object IRS 3 A (K ~ 7.9). We use HST/NICMOS archive images to derive near-infrared photometry for the sources and estimate the stellar masses of the three brightest objects IRS 3 A, B, and C to be in the range ~ 5-15 M_sun. IRS 3 A is surrounded by a bipolar nebula (position angle ~ 30degr ), suggesting it to be embedded in a thick circumstellar disk or a torus with polar cavities. IRS 3 B shows a remarkable jet-like emission feature pointing towards the north-east (position angle 50degr ). This feature consists of at least three individual knots with projected separations of 130, 230, and 290 mas (110, 190, and 240 AU) from IRS 3 B, which are much brighter in the K band than in the H band. This strongly indicates outflow activity from IRS 3 B, which is therefore probably the source of the compact high velocity molecular outflow reported from Mon R2 IRS 3. We also analyze Chandra X-ray archive data for the Mon R2 region and find IRS 3 A and IRS 3 C to be sources of hard (3 - 10 keV) and variable X-ray emission, suggesting plasma temperatures of at least 50 x 10⁶ K. The similarity of the X-ray properties to those of Class I protostars suggests magnetic interaction between the protostars and their circumstellar disks to be the origin of the X-ray emission; this provides indirect evidence for the presence of circumstellar disks in the intermediate- to high-mass young stellar objects IRS 3 A and IRS 3 C.