Solar Mass Clumps in the B5 Core

Abstract

Results from IRAS have shown that four compact sources exist within the central 0.°5 of the dark cloud Barnard 5 (B5) (Beichman et al .,1984, Ap. J. (Letters),278, L45). The source denoted IRS1 by those authors is the only IRAS source located within the core (~ 5’ × 10’). IRS1 appears pointlike in all bands except the 100 μm band. The NH3 maps of B5 (Benson, 1984, Ph.D thesis; Benson and Myers 1988, private communication) show two peaks of emission in the core of B5. The southernmost of the two peaks in NH3 emission corresponds to the location of the IRAS source while the northern peak, located approximately 2’ north of IRS1, has no IRAS counterpart. Boss (1985, ApJLett,288 L25) suggested that a second protostellar source could be present at the position of the northern NH3 peak based on his models of binary protostellar formation. We report observations of the B5 core at 160 and 360 μm which were made in order to test Boss’ hypothesis and to further study the environment of a known star forming region. The 360 μm observations were made at the NASA Infrared Telescope Facility and the 160 μm observations were made from the Kuiper Airborne Observatory using the University of Chicago submillimeter 32 detector array camera and Far-IR 32 detector array camera. Figures 1 and 2 are photometric maps of the B5 core at 360 and 160 μm, respectively, made using a 45“ beam. In figure 1, contour levels represent 1Jy/beam with the peak contour being 9 Jy/beam. In figure 2, contour levels represent 1.2 Jy/beam with the highest contour level at 10.8 Jy/beam. The (0,0) position corresponds to α(1950) = 03h44m28.s7 and δ(1950) = 32°44′30″. Both maps display a crescent shaped feature similar to that seen in the outer regions of B5 in the C18O observations (Goldsmith, Langer, and Wilson, 1986,Ap. J. (Letters) 303, L11) (GLW). The NH3 map (Benson and Myers, 1988) correlates much better with the 160 μm map than with the 360 pm map. Four regions of relatively high density are observed along the crescent ridge, which we have labelled A, B, C, and D. Region A corresponds to the position of the IRAS (IRS1) point. Regions B and C have not been previously identified, while D corresponds to the northernmost NH3 peak. The background flux from the ridge is r 4 JY/beam at 360 μm and r 3 JY/beam at 160 μm. After background subtraction and beam deconvolution, both A and B appeared approximately gaussian in shape with FWHM values of 44” and 32“, respectively, at 360 μm. The total flux densities for A and B at 360 μm are 12 Jy and 5 Jy, respectively, and total flux densities at 160 μm for A and B are 16 Jy and ≤1.5 Jy.