Intermediate-mass star-Intermediate-mass star-forming regions: are they so forming regions: are they so

complex?complex?Maite BeltránMaite Beltrán

Josep Miquel Girart

Robert Estalella

Paul T.P. Ho

Aina Palau

IntroductionIntroduction

Intermediate-mass protostars: 2 MIntermediate-mass protostars: 2 Mo o < M < 10 M< M < 10 Moo ; precursors of Herbig Ae and Be stars; embedded ; precursors of Herbig Ae and Be stars; embedded in clouds of gas and dust; power energetic molecular outflows, in general less collimated and in clouds of gas and dust; power energetic molecular outflows, in general less collimated and bipolar and more chaotic than those of low-mass stars.bipolar and more chaotic than those of low-mass stars.

Intermediate-mass are rare in comparison with low-mass counterparts; located at greater distances; Intermediate-mass are rare in comparison with low-mass counterparts; located at greater distances; the immediate vicinity is a very complex environment; dust emission resolved out in more than one the immediate vicinity is a very complex environment; dust emission resolved out in more than one YSO; interaction of the outflows with the surroundings is more dramatic YSO; interaction of the outflows with the surroundings is more dramatic poorly understood, in poorly understood, in part due to the difficulty of identifying true protostars.part due to the difficulty of identifying true protostars.

Are intermediate-mass protostars and outflows intrinsically different, being the latter sistematically Are intermediate-mass protostars and outflows intrinsically different, being the latter sistematically less collimated? Or is the complexity the result of the environment itself and poor angular less collimated? Or is the complexity the result of the environment itself and poor angular resolution observations?resolution observations?

High-angular resolution observations: observational constraints? BIMA and OVRO observations of High-angular resolution observations: observational constraints? BIMA and OVRO observations of gas and dust at mm gas and dust at mm ’s: CO, CS, CH’s: CO, CS, CH33OH, COH, C1818O, HCO, HC33N to compare the morphology and evolution of N to compare the morphology and evolution of intermediate-mass protostars with those of low-mass intermediate-mass protostars with those of low-mass

IC1396N and L1206: embedded sources in two bright-rimmed cloudsIC1396N and L1206: embedded sources in two bright-rimmed clouds

IC1396NIC1396N

Cepheus@ 750 pc

IRAS 21391+5802

Digitized Sky survey 2 + VLA 3.6 cm observations (Beltrán et al. 2002)

L=225-440 Lo

IC1396NIC1396N

(Codella et al. 2001)

(Reipurth et al. 2003)

H2

IC1396N: continuum obervationsIC1396N: continuum obervations

VLA @ 3.6cmBIMA

IRAS 21391+5802

Beltrán et al. (2002)

5.1 Mo

0.1 Mo

0.1 Mo

IC1396N: CO and CSIC1396N: CO and CS

BIMA 1BIMA 3

BIMA 2

IC1396N: CS and CHIC1396N: CS and CH33OHOH

Shocked material

IC1396N: interaction of the outflow with the IC1396N: interaction of the outflow with the

dense materialdense material

CO(1-0) + CS(5-4)

shocks

CS (5-4)

quiescent quiescent

Shocked cloudlet model scenario

inverted bow shock

Clumps are tracing gas entrained within the surface of interaction between the molecular outflow and the dense ambient quiescent clump

L1206L1206

IRAS 22272+6358A

@910 pc

Digitized Sky survey 2 + VLA 6 cm observations

(Beltrán et al. 2006)

L=1200 Lo

13CO(1-0) C18O(1-0)

2mm

Sugitani et al. (2000)

Ridge et al. (2003)

L1206L1206

IRAS 22272+6358A

@910 pc

Digitized Sky survey 2 + VLA 6 cm observations

(Beltrán et al. 2006)

L=1200 Lo

Sugitani et al. (1989)

L1206:continuum + COL1206:continuum + CO

OVRO

Beltrán et al. (2006)

IRAS 22272+6358A1.6 Mo

2.2 Mo

1.8 Mo

14.2 Mo

CO(1-0)

L1206: CL1206: C1818O + HCO + HC33NN

(1-0)

(12-11)

-11 km/s

redshifted peak @5.5” SE

L1206: interaction of the molecular cloud L1206: interaction of the molecular cloud with the ionized bright-rimmed cloudwith the ionized bright-rimmed cloud

OVRO 2

Weakness and small size of the redshifted lobe:

• redshifted lobe breaks outs out of the molecular cloud

• or redshifted (southern) lobe is photodissociated

Digitized Sky survey 2 + VLA 6 cm observations

(Beltrán et al. 2006)

The HII region is in the background and the ionization-shock front lies very close to the southern redshifted lobe, thus any redshifted ejected material could be destroyed by the intense radiation field at the ionization front.

The internal pressure of the molecular gas ~ ionized boundary layer pressure the ionized front right now would be stalled

or redshifted (southern) lobe is photodissociated

HC3N elongated in the direction of the CO outflow and peaks south of OVRO 2. Emission is enhanced 3-4 towards the south:

shock-enhancement either by the outflow or most probably by the shock preceding the ionization front , which has compressed and heated the neutral gas, helping to enhance the HC3N abundance

CO+HC3N

OVRO 2

Intermediate-mass protostars and their Intermediate-mass protostars and their outflowsoutflows

Intermediate-mass star forming regions are usually resolved into more than one embedded object, Intermediate-mass star forming regions are usually resolved into more than one embedded object, being one of them the one with has most of the mass.being one of them the one with has most of the mass.

The morphology and properties of the intermediate-mass protostars do not differ significantly of The morphology and properties of the intermediate-mass protostars do not differ significantly of those of low-massthose of low-mass

The same for their molecular outflows. They are more massive and energetic than those of low-The same for their molecular outflows. They are more massive and energetic than those of low-mass stars, however their properties are consistent with the correlations found for low-mass objects mass stars, however their properties are consistent with the correlations found for low-mass objects (e.g. Bontemps et al. 1996; Anglada 1996).(e.g. Bontemps et al. 1996; Anglada 1996).

The complexity and chaoticity of the molecular outflows driven by intermediate-mass protostars is The complexity and chaoticity of the molecular outflows driven by intermediate-mass protostars is not intrinsic but a result of the more complex protostellar environment itself not intrinsic but a result of the more complex protostellar environment itself they are embedded they are embedded in larger amounts of material, then the interactions between high-velocity gas and the circumstellar in larger amounts of material, then the interactions between high-velocity gas and the circumstellar material will be more dramatic, disrupting and pushing more material.material will be more dramatic, disrupting and pushing more material.

Need of high-angular resolution observations (e.g. high collimation of the outflows)Need of high-angular resolution observations (e.g. high collimation of the outflows)