Multiple YSOs in the low-mass star-forming region IRAS CONTENT Introduction Previous work on IRAS Observations Results Discussion and Conclusions G. Busquet, R. Estalella, A. Palau, J. M. Girart, G. Anglada and I. Sepúlveda

1. Introduction The low-mass star-forming theories assume that star formation takes place in the isolated mode, forming one star per dense core Observational studies show that most stars form in groups The interaction between the different objects may play an important role. In particular the interaction of outflows from the YSOs formed in the cloud

2. Previous work on IRAS Single-dish NH 3 (1,1) from Sepúlveda (2001) Molecular outflow in CO (1-0) from Yang et al. (1990) H 2 O maser emission from Han et al. (1998) VLA 6 cm and 3.6 cm continuum emission revealing two radio sources (A. Palau, 2002 Master Thesis) Cepheus OB4 star-forming region

3. Observations VLA observations Continuum emission: 6 cm and 3.6 cm (2000 September) 3.6 cm and 7 mm (2004 August) NH 3 (1,1) and (2,2): 4 IF mode bandwidth: 3.12 MHz spectral resolution: 48.8 kHz ~ 0.6 km s -1 (2004 August) IRAM 30m Telescope Continuum emission: 1.2 mm with the MPIfR 37-element bolometer array MAMBO I using the on-the-fly mapping mode (2006 June) Line emission: 12 CO (2-1), 13 CO (2-1) and C 18 O (2-1) with the HERA array using the on-off mode spectral resolution~0.4 km s -1 (2006 May and July)

4. Results VLA continuum emission 6 cm3.6 cm and 7 mm In the centimeter range the spectral index of the two detected sources are: VLA 7:α=-1.56±0.2 characteristic of non-thermal emission VLA 8:α=0.5±0.4characteristic of free-free thermal emission from ionized gas (thermal radio jet) VLA 8A: M< 0.8 M ⊙ VLA 8B: M< 1.1 M ⊙ Western IR: M<0.7 assuming a dust emissivity index β=1 and a dust temperature of Td=20 K for VLA 8A and Td=15 K for VLA 8B The total mass of gas and dust for each mm source is:

4. Results VLA NH3 emission NH 3 (1,1)NH 3 (2,2) Two clumps detected in NH 3 (1,1) while the NH 3 (2,2) map shows emission concentrated near the three sources The total mass estimated for the NH 3 clumps, assuming NH 3 /H 2 ~10 -8, are: Northern clump:M=2 M ⊙ Southern clump:M<0.75 M⊙

4. Results VLA NH3 emission NH 3 (1,1) second-order moment(2,2)/(1,1) ratio Evidences of Line broadening (Δv~1 km s -1 ) in an arc-shape structure around the position of the three objects Local heating (T rot ~17 K) just north of the two mm sources and in the western IR source While the southern clump appears as quiescent (T rot <11K and Δv~0.5 km s -1 )

4. Results 1.2 mm dust continuum emission Compact 1.2 mm dust emission, peaking close to the NH 3 peak, with some substructure There is no 1.2 mm emission detected toward the southern clump Dust condensation toward the north- west detected also in NH 3 The total mass of gas and dust from thermal emission derived from the 1.2 mm emission, assuming β~1 and T d = 20 K is: M~ 6 M ⊙

4. Results CO (2-1) line emission: The molecular outflow Velocity range (V LSR =19.9 km s -1) : Blue wing: -40 to -22 km s -1 Red wing: -17 to -5 km s -1 Physical parameters of the outflow, with T ex ~13 K (derived from the line intensity) similar to those found for Class 0 and Class I low-mass YSOs x x x Red x x x Blue L mech (L ⊙ ) E kin (erg) P rate (M ⊙ km s -1 yr -1 ) P (M ⊙ km s -1 ) M rate (M ⊙ yr -1 ) Mass (M ⊙ ) N 12 (10 16 cm -2 ) Age (10 5 yr) CO (2-1) emission: The molecular outflow

5. Discussion and Conclusions Multiple low-mass YSOs in the northern NH 3 clump: Western IR: bright only in the IR VLA 8A: IR and mm emission VLA 8B: bright in the mm but no IR emission Different evolutionary stages

5. Discussion and Conclusions It seems that there is a cavity in NH 3 just north of the two mm sources, that may be created by the molecular outflow The morphology of the outflow follows the structure of the NH 3 It is possible that the blueshifted component of the outflow N-S is deflected Temperature enhancements detected along the cavity : May arise from the molecular outflow as a result of the shock interactions of the jet/outflow with the molecular gas Interaction of the molecular outflow with the dense gas