1. LDN 723: Can molecular emission be used as clock calibrators? Josep Miquel Girart Collaborators: J.M.Masqué,R.Estalella (UB) R.Rao (SMA)

2. L723 is a isolated dark cloud: Located at a distance of 300 pc Total mass of few solar masses Size: 0.15 pc It harbors a low mass Class 0 object: Protostellar system Bolometric luminosity of 3 Lo Very embedded objects (detected only in mid-IR and larger wavelengths) Quadrupolar molecular outflow (maybe there are more outflows!) HH objects H2O maser emission cm emission shows several sources, some of them tracing protostars VLA NH3 observations showed two sources of heating: VLA 2 and WHS References: Avery et al. 1991 Lee et al. 2002 Anglada et al. 1991, 1996 Girart et al. 1997 López et al. 2006 Carrasco-González et al. 2006

3. BIMA N 2 H + observations Apparent distribution of N2H+ and NH3 is very similar … but: column density ratioshow differences along the dense core: Central region: (NH3)/N(N2H+)= 60  high density/SF Dense gas far away from star formation activity: (NH3)/N(N2H+)=100-200  starless region

4. SMA 1.3mm continuum observations Binary dusty system with a separation of 3  (900 AU): One associated with VLA 2 (M≈0.08 M  ) The other without any counterpart know (M≈0.07 M  ) WHS doesn’t have dust emission (M≤0.01 M  )

5. Molecular line observations

6. Modeling the SMA dust Twin protostellar cores Optical thin emission at 1.3mm Primary beam correction from SMA antenna Modeled emission converted to the SMA observed visibility distribution SMA synthetic maps of models Residual maps:  2 analysis

7. Modeling the SMA H 2 CO Twin protostellar cores H 2 CO different in the two sources (abundance and Rmin, Rmax) Primary beam correction from SMA antenna Modeled emission converted to the SMA observed visibility distribution SMA synthetic maps of models Residual maps:  2 analysis

8. LDN 723: Properties of dense cores SourcesOutflowMassTemp (1000AU) H 2 CO (r min -r max ) X[H 2 CO]N[NH 3 / N[N 2 H + ]] CN & DCN VLA 2 Yes0.08 M  20 K30-300 AU 5  10 -9 46yes MM E ? 0.07 M  20 K100-1000 AU 5  10 -10 idemyes WHS ?≤0.01 M  19 K??75no WHS MM E VLA2

9. Summary Detected a twin protostellar system They share the same physical conditions (mass, temperature and density distribution) But they are chemically different and they show different outflow activity  Due to different evolutionary stage/different luminosity? WHS clump: is it a warm (protostellar) core or is it just a illuminated clump?