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Revealing the dust grain size in the inner envelope of the Class i protostar Per-emb-50

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Agurto-Gangas, C 
Pineda, JE 
Szucs, L 
Testi, L 


Context. A good constraint of when the growth of dust grains from sub-micrometer to millimeter sizes occurs, is crucial for planet formation models. This provides the first step towards the production of pebbles and planetesimals in protoplanetary disks. Currently, it is well established that Class II objects have large dust grains. However, it is not clear when in the star formation process this grain growth occurs. Aims. We use multi-wavelength millimeter observations of a Class I protostar to obtain the spectral index of the observed flux densities α mm of the unresolved disk and the surrounding envelope. Our goal is to compare our observational results with visibility modeling at both, 1.3 and 2.7mm simultaneously. Methods. We present data from NOEMA at 2.7mm and SMA at 1.3mm of the Class I protostar, Per-emb-50. We model the dust emission with a variety of parametric and radiative-transfer models to deduce the grain size from the observed emission spectral index. Results. We find a spectral index in the envelope of Per-emb-50 of α env = 3.3 ± 0.3, similar to the typical ISM values. The radiativetransfer modeling of the source confirms this value of α env with the presence of dust with a a max ≤ 100 μm. Additionally, we explore the backwarming effect, where we find that the envelope structure affects the millimeter emission of the disk. Conclusions. Our results reveal grains with a maximum size no larger than 100 μm in the inner envelope of the Class I protostar Per-emb-50, providing an interesting case to test the universality of millimeter grain growth expected in these sources.



stars: formation, stars: protostars, circumstellar matter, techniques: interferometric

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Astronomy and Astrophysics

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EDP Sciences
European Research Council (341137)
Science and Technology Facilities Council (ST/N000927/1)
C.A.G. acknowledges support from CONICYT-Becas Chile (grant 72160297). P.C, J.P and L.S acknowledge the financial support of the European Research Council (ERC; project 320620). L.T. acknowledges the financial support of the Italian Ministero dell’Istruzione, Universitá e Ricerca through the grant Progetti Premiali 2012 – iALMA (CUP C52I13000140001), and by the Deutsche Forschungs-gemeinschaft (DFG, German Research Foundation) – Ref no. FOR 2634/1 TE 1024/1–1. M.T. has been supported by the DISCSIM project, grant agreement 341137 funded by the European Research Council under ERC-2013-ADG. A.M. acknowledges an ESO Fellowship.