Multiple YSOs in the low-mass

star-forming region IRAS 00213+6530

CONTENT • Introduction • Previous work on IRAS 00213+6530• 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 00213+6530

• Single-dish NH3 (1,1) from Sepúlveda (2001)

• Molecular outflow in CO (1-0) from Yang et al. (1990)

• H2O 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. ObservationsVLA observations

• Continuum emission:6 cm and 3.6 cm(2000 September)3.6 cm and 7 mm(2004 August)

• NH3 (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:12CO (2-1), 13CO (2-1) and C18O (2-1) with the HERA array using the on-off modespectral resolution~0.4 km s-1

(2006 May and July)

4. ResultsVLA continuum emission6 cm 3.6 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 emissionVLA 8: α=0.5±0.4 characteristic 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 adust temperature of Td=20 K for VLA 8A andTd=15 K for VLA 8B

• The total mass of gas and dust for each mm source is:

4. ResultsVLA NH3 emissionNH3 (1,1) NH3 (2,2)

• Two clumps detected in NH3 (1,1) while the NH3 (2,2) map shows emission concentrated near the three sources

• The total mass estimated for the NH3 clumps, assuming NH3/H2~10-8, are:Northern clump: M=2 M⊙

Southern clump: M<0.75 M⊙

4. ResultsVLA NH3 emissionNH3 (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 (Trot~17 K) just north of the two mm sources and in the

western IR sourceWhile the southern clump appears as quiescent (Trot<11K and Δv~0.5 km s-1)

4. Results1.2 mm dust continuum emission

• Compact 1.2 mm dust emission, peaking close to the NH3 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 NH3

The total mass of gas and dust from thermal emission derived from the1.2 mm emission, assuming β~1 and Td = 20 K is:

M~ 6 M⊙

4. Results

CO (2-1) line emission: The molecular outflow

Velocity range (VLSR=19.9 km s-1):Blue wing: -40 to -22 km s-1

Red wing: -17 to -5 km s-1

Physical parameters of theoutflow, with Tex~13 K (derivedfrom the line intensity) similarto those found for Class 0 andClass I low-mass YSOs.

0.092.3x10449.3x10-51.97.8x10-60.22.82.0Red

0.81.5x10455.7x10-48.63.19x10-50.55.61.5Blue

Lmech (L ⊙)

Ekin

(erg)P rate

(M ⊙ km s-1 yr -1)P

(M ⊙ km s-1)M rate

(M ⊙ yr-1)Mass(M⊙)

N12

(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 NH3 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 NH3 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 NH3

• 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 shockinteractions of the jet/outflow with the molecular gas

Interaction of the molecular outflow with the dense gas