1. SMA Observations of the Binary Protostar System in L723 Josep Miquel Girart 1, Ramp Rao 2, Robert Estalella 3 & Josep Mª Masqué 3 1 Institut de Ciències de l’Espai, CSIC / Institut d’Estudis Espacials de Catalunya 2 Harvard-Smithsonian Center for Astrophysics 3 Departament d’Astronomia i Meteorologia, Universitat de Barcelona The observations were carried out with the SMA array, with an angular resolution of 3” and spectral resolution of 0.3 km/s The aim of this work is to study in detail the distribution and properties of the dust and molecular gas around the L723 protostars and to understand better the evolution of binary/multiple young stellar systems BACKGROUND: The L723 molecular cloud harbors IRAS 19156+1906 source. Its IR colors are those of a Class 0 protostar. IRAS 19156+1906 is associated with a quadrupolar molecular CO outflow is (e.g. Lee et al. 2002). VLA observations revealed a thermal radio jet, VLA 2, elongated in the direction of the large pair of CO lobes (Anglada et al. 1991, 1996). There are several indications from high angular resolution VLA and OVRO observations that this may be a multiple young stellar system: (1)The NH 3 emission shows two spots of heating, which suggests that they harbor protostars (Girart et al. 1997). One of the spots is associated with VLA 2. The other spot is located 10" (3000 AU) west of VLA 2 and has not known counterparts (WHS). (2)The mm dust emission shows two compact sources separated by ~3" (900 AU) (Launhardt 2004); (3)The VLA 2 radio source splits in two components separated by ~75 AU (Anglada 2004) References: Anglada 2004, RevMexAA SC, 21, 100 Anglada, Estalella, Rodríguez, Torrelles, López & Cantó 1991, ApJ, 376, 615 Anglada, Rodríguez & Torrelles 1996, ApJ, 473, L123 Estalella, Palau, Girart, Beltrán, Osorio, Ho & Anglada 2005, A&A, submitted Girart, Estalella, Anglada, Torrelles, Ho & Rodríguez 1997, ApJ, 489, 743 Girart et al. 2005, in preparation Launhard 2004, IAU Symp. 221, 213 Lee,Mundy, Stone & Ostriker 2002, ApJ, 576, 294 Palacios, I., & Eiroa, C. 1999, A&A, 346, 233 The molecular emission The SMA filters out the emission from the extended envelope so it detects the denser circumstellar material around the protostars. Indeed, from the comparison with H 2 CO 3 03 -2 02 single dish observations we get that the SMA detects about ~11% of the total line emission of this transition. For all the molecular transitions observed the emission is detected in the two dust compact sources. VLA 2 has stronger molecular emission that MM E, except for the DCN line. The WHS is only detected in ammonia. BIMA N 2 H + observations also detects this source (Girart et al. 2005) The line width of the H 2 CO lines is larger than the NH 3 lines: VLA2:  v(H 2 CO) = 1.6  0.1 km/s  v (NH 3 ) = 0.9  0.1 km/s MME:  v(H 2 CO) = 2.0  0.1 km/s  v (NH 3 ) = 1.3  0.1 km/s The H 2 CO traces s more compact region than the NH 3 (2,2) Contour maps of the NH 3 (2,2) from the VLA (Girart et al. 1997) and the CN 2-1, H 2 CO 3 03 -2 02, DCN 3-2 emission from the SMA. Color image of the 1.35 mm emission from the dust. The two crosses show the peak position of the mm continuum emission; the tilted cross shows the position of the WHS (Girart et al. 1997) Contour map of the 850  m dust emission from the SCUBA/JCMT superposed on the gray scale image of the NH 3 (1,1) integrated emission from the VLA (figure from Estalella et al. 2005). The white, red and black crosses indicate the position of VLA 2, WHS and VLA 1, respectively (Anglada et al. 1991; Girart et al. 1997). The triangles mark the position of H2 knots (Palacios & Eiroa 1999). The dashed red circles shows the field of view of the SMA observations. SCUBA beam VLA beam The 1.35 mm dust continuum emission The SMA detects the two sources previously reported by Launhard (2004). Their emission is similar (S ~50 mJy) and suggest a circumstellar mass of ~0.3 M  for the two protostars (assuming a T dust =25 K). No dust emission is detected towards WHS with a 3-  upper limit of 4.2 mJy Beam -1 or 0.03 M  SMA map of the 1.35 mm dust emission. The cross shows the position of VLA 2 (Anglada et al. 1996). SMA beam The two sources are partially resolved at scales of 500 AU. The annular averaged in the u,v plane shows two components: An unresolved component (  < 300 AU), possibly from the disk(s) An extended component, with a size of   1000 AU, coming from the envelope What can we learn about these results? VLA 2 is the only source that has clear signposts of outflowing phase: a thermal radio jet with its axis in the direction of the largest pair of the molecular outflow CO lobes (Anglada et al. 1996), water masers (Girart et al. 1997). MM E has similar dust and molecular properties than VLA 2, although its molecular emission is somewhat weaker than VLA2. But this source doesn’t have any outflow signpost detected yet. That could be an indication that is in an earlier stage of collapse? WHS is only detected in N bearing molecules and no dust emission is associated with it. But the presence of temperature enhancement (from NH3 (1,1) and (2,2) line ratio: Girart et al. 1997) suggests an internal source of heating. Could it be the earlier stage of star formation?, where not enough material has accreted in the disk and molecular depletion is still very important.