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Jets and Wide-Angle Outflows in Cepheus E: New Evidence from Spitzer

T. Velusamy, W. D. Langer, M. S. N. Kumar, J. M. C. Grave

Abstract
Outflows and jets are believed to play a crucial role in determining the mass of the central protostar and its planet forming disk by virtue of their ability to transport energy, mass, and momentum of the surrounding material, and thus terminate the infall stage in star and disk formation. In some protostellar objects both wide angle outflows and collimated jets are seen, while in others only one is observed. Spitzer provides unprecedented sensitivity in the infrared to study both the jet and outflow features. Here, we use HiRes deconvolution to improve the visualization of spatial morphology by enhancing resolution (to sub-arcsecond levels in the IRAC bands) and removing the contaminating sidelobes from bright sources. We apply this approach to study the jet and outflow features in Cep E a young, energetic Class 0 protostar. In the reprocessed images we detect: (i) wide angle outflow seen in scattered light; (ii) morphological details on at least 29 jet driven bow shocks and jet heads or knots; (iii) three compact features in 24 µm continuum image as atomic/ionic line emission coincident with the jet heads; and, (iv) a flattened ~35" size protostellar envelope seen against the interstellar background PAH emission as an absorption band across the protostar at 8 µm. By separating the protostellar photospheric scattered emission in the wide angle cavity from the jet emission we show that we can study directly the scattered light spectrum. We present the H2 emission line spectra, as observed in all IRAC bands, for 29 knots in the jets and bowshocks and use them in the IRAC color – color space as a diagnostic of the thermal gas in the shocks driven by the jets. The data presented here will enable detailed modeling of the individual shocks retracing the history of the episodic jet activity and the associated accretion on to the protostar. The Spitzer data analysis presented here shows the richness of its archive as a resource to study the jet/outflow features in H2 and scattered light in a large homogeneous sample.

Keywords
Herbig–Haro objects – infrared: ISM – ISM: individual objects (Cepheus E) – ISM: jets and outflows – stars: formation – stars: protostars

The Astrophysical Journal
Volume 741, Number 1, Page 60_1
2011 October

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia