2Mass J17112318-2724315: A deeply embedded low-mass protostellar system in the B59 molecular cloud

Abstract

We present near-infrared observations of the low-mass deeply embedded Class 0/I system 2MASS J17112318-2724315 (2M171123) in the B59 molecular cloud. Bright scattered light nebulosity is observed toward this source in the K s images, that seems to trace the edges of an outflow cavity. We report the detection of a low-luminosity protostar 2M17112255-27243448 (2M17112255) that lies ∼ 8″ (∼1000 AU) from 2M171123. This is a Class I system, as indicated by its 2-8 μm slope and Infrared Array Camera colors, with an estimated internal luminosity of ∼ 0.3 L ⊙. We estimate a mass of ∼ 0.12-0.25 M ⊙ for this source, at an age of 0.1-1 Myr. Also presented is detailed modeling of the 2M171123 system. The best-fit parameters indicate a large envelope density of the order of ∼ 10-13 g cm-3, and an intermediate inclination between 53° and 59°. The observed Ks -band variability for this system could be explained by slight variability in the mass infall rate between 2.5E-5 and 1.8E-5 M ⊙ yr-1. The protostar 2M171123 exhibits a rarely observed absorption feature near 11.3 μm within its 10 μm silicate band. We find a strong correlation between the strength in this 11.3 μm "edge" and the H2O-ice column density, indicating the origin of this feature in the thickness of the ice mantle over the silicate grains. © 2009. The American Astronomical Society. All rights reserved.