The basic scenario for star formation includes a central stellar object which is surrounded by a flattened envelope/disk. The central star usually drives a molecular outflow/jet perpendicular to the disk plane. The validity of this picture has been proven for low- and medium-mass stars (see, e.g., McCaughrean et al. 1999). However, in many cases, the influence of dust obscuration by the parent molecular cloud and the clustering of objects makes it difficult to reveal the circumstellar structure of an individual object. A frequently observed feature of young stellar objects (YSOs) is their association with bipolar nebulae (Staude & Elsässer 1993, Close et al. 1997). These nebulae result from scattering in cavities which might be produced either by the outflows (Wood et al. 1998, Menshchikov et al. 1999) or the collapse of sheet-like structures (Hartmann et al. 1996).
In the following, we will examine the nebula BBW 192E which shows quite different morphologies at different wavelengths. The optically fan-shaped nebula BBW 192E (GRV 5) is listed in the catalogue of nebulous objects by Brand et al. (1986) and was mentioned as a region of recent star formation by Gyulbudaghian et al. (1993). The nebula is located towards the Vela OB4 association (distance: 1 kpc, Slawson & Reed 1988) and the dark cloud DC 263.2+1.6 (Wouterloot & Brand 1989, Hartley et al. 1986; SL 4: Sandqvist & Lindroos 1976) for which Wouterloot & Brand (1989) estimated a kinematic distance of 1.2 kpc. The photometric distance of BBW 192E lies in the range between 0.7 and 1.2 kpc and star counts point to a distance between 0.7-2.6 kpc (Liseau et al. 1992). Within this paper, we assume a distance of 1.2 kpc.
A recent study by Massi et al. (1999) of YSOs in the Vela Molecular Ridge (VMR) led to the detection of a dozen sources which, according to the classification scheme of Lada (1987), belong to class I, and possibly one Herbig Ae/Be star. The object BBW 192E was not included in their investigation. Thus, the results presented here complete our view on the ongoing star formation in the VMR molecular cloud.
At optical wavelengths, the nebula associated with BBW 192E is extended essentially in southeast-northwest direction, with a brightening at its eastern apex which lies in the error ellipse of the IRAS point source 08513-4201. Cohen et al. (1989) noted that the bright condensation is brighter in blue than in red. The morphology and colour of BBW 192E at optical wavelengths led Cohen et al. to classify the object as a reflection nebula, consistent with the absence of conspicuous emission lines in the nebula. Liseau et al. (1992) detected two near-infrared sources (IRS 26/1, IRS 26/2) with offsets of 5" and 26" from the nominal position of IRAS 08513-4201, respectively. Pettersson & Reipurth (1994) assigned IRAS 08513-4201 to Lada class I. They mentioned that according to the luminosity of this object it should be similar to an Herbig Ae/Be star, just emerging from its molecular cloud.
In this paper, we present the first extensive multi-wavelength imaging investigation of BBW 192E. We performed NIR/MIR imaging (HKK´NQ) and photometry (JHKK´LMNQ) as well as 1.3 mm continuum mapping. In Sect. 2 we describe the observations and data reduction. In Sect. 3, we present the observational results and derive physical properties, especially from the 1.3 mm continuum map. The results of our multi-wavelength investigation are discussed in Sect. 4.
© European Southern Observatory (ESO) 2000
Online publication: December 8, 1999