Oral Presentation
From cores to the inner envelope: Tracing variations in the dust emissivity index of the L1448 protostars
Presenter: Zuleta Andres (Institut de Ciències de l'Espai (ICE-CSIC))
Protostellar systems provide unique laboratories to study the earliest stages of star and planet formation, as they span from compact hydrostatic cores and circumstellar disks (10−100 au) to large-scale infalling envelopes (100−10 000 au) embedded within molecular clouds. Recent observations of protostellar envelopes have revealed very low emissivity indices (β<1) toward deeply embedded protostars,
potentially indicating that significant dust evolution is already occurring during the Class 0 phase. Current dust models can only reproduce such low values when grains larger than 100 µm are included.
To investigate whether the properties of dust grains in protostellar environments are inherited from the diffuse ISM or instead evolve during the assembly and collapse of dense cores into star-disk systems, we present a multi-scale study of the dust emissivity index in embedded protostars in L1448. By using NIKA2 continuum observations together with ALMA interferometric data, we derive β radial profiles spanning scales from the parent filament (r∼ 30 000 au) down to the inner envelope (r ∼ 400 au). This approach allows us, for the first time, to trace the dust emissivity index continuously from cloud scales down to the inner envelope, filling the gap that usually divides single-dish and interferometric measurements. We find a continuous monotonic decrease of β (from 2.0 to 0.3) across two orders of magnitudes in spatial scales.
Our results suggest that the dust properties evolve already at cloud scales (15 000 < r < 30 000 au), with a decrease of the dust emissivity index observed with gas density, and that this evolution propagates further in the cores formed out of this material. These findings highlight the importance of multi-scale observations and call for further investigations and better physical models for dust coagulation in the dense gas, long before the material incorporates the disk.
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