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

Intermediate-mass star-forming regions: are they so complex?. Maite Beltrán. Josep Miquel Girart Robert Estalella Paul T.P. Ho Aina Palau. Introduction.

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

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  1. Intermediate-mass star-forming regions: are they so complex? Maite Beltrán Josep Miquel Girart Robert Estalella Paul T.P. Ho Aina Palau

  2. Introduction • Intermediate-mass protostars: 2 Mo < M < 10 Mo ; precursors of Herbig Ae and Be stars; embedded 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. • 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 YSO; interaction of the outflows with the surroundings is more dramatic  poorly understood, in part due to the difficulty of identifying true protostars. • 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 resolution observations? • High-angular resolution observations: observational constraints? BIMA and OVRO observations of gas and dust at mm l’s: CO, CS, CH3OH, C18O, HC3N to compare the morphology and evolution of intermediate-mass protostars with those of low-mass • IC1396N and L1206: embedded sources in two bright-rimmed clouds

  3. IC1396N Cepheus@ 750 pc L=225-440 Lo IRAS 21391+5802 Digitized Sky survey 2 + VLA 3.6 cm observations (Beltrán et al. 2002)

  4. IC1396N H2 (Codella et al. 2001) (Reipurth et al. 2003)

  5. BIMA IRAS 21391+5802 IC1396N: continuum obervations VLA @ 3.6cm 5.1 Mo 0.1 Mo 0.1 Mo Beltrán et al. (2002)

  6. IC1396N: CO and CS BIMA 2 BIMA 3 BIMA 1

  7. IC1396N: CS and CH3OH Shocked material

  8. IC1396N: interaction of the outflow with the dense material Shocked cloudlet model scenario CO(1-0) + CS(5-4) inverted bow shock Clumps are tracing gas entrained within the surface of interaction between the molecular outflow and the dense ambient quiescent clump quiescent shocks quiescent CS (5-4)

  9. L1206 Ridge et al. (2003) @910 pc L=1200 Lo C18O(1-0) 13CO(1-0) IRAS 22272+6358A Digitized Sky survey 2 + VLA 6 cm observations (Beltrán et al. 2006) 2mm Sugitani et al. (2000)

  10. L1206 @910 pc L=1200 Lo IRAS 22272+6358A Sugitani et al. (1989) Digitized Sky survey 2 + VLA 6 cm observations (Beltrán et al. 2006)

  11. L1206:continuum + CO OVRO CO(1-0) IRAS 22272+6358A 1.6 Mo 14.2 Mo 2.2 Mo 1.8 Mo Beltrán et al. (2006)

  12. L1206: C18O + HC3N (1-0) redshifted peak @5.5” SE  -11 km/s (12-11)

  13. CO+HC3N OVRO 2 OVRO 2 L1206: interaction of the molecular cloud with the ionized bright-rimmed cloud • Weakness and small size of the redshifted lobe: • redshifted lobe breaks outs out of the molecular cloud • or redshifted (southern) lobe is photodissociated or redshifted (southern) lobe is photodissociated 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 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 Digitized Sky survey 2 + VLA 6 cm observations (Beltrán et al. 2006)

  14. Intermediate-mass protostars and their outflows • 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. • The morphology and properties of the intermediate-mass protostars do not differ significantly of those of low-mass • 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 (e.g. Bontemps et al. 1996; Anglada 1996). • 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  they are embedded 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. • Need of high-angular resolution observations (e.g. high collimation of the outflows)

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