A step back in space and time: dusty envelopes and streamers infalling in young disks.

Circumstellar discs orbiting young sources have long been considered isolated cradles of planet formation, while recent observations are challenging this paradigm. First, some protostellar envelopes infalling onto younger, embedded discs seem to host submillimetric grains, possibly indicating early dust growth at scales of a few hundred au. Second, detections of infalling large-scale streamers are a constant reminder of how discs can be replenished at any time of their evolution with fresh material. These findings raise core questions for star and planet formation theories:

Is dust really starting to coalesce at earlier stages than previously thought? Might there be alternative explanations for this apparent conundrum?

To what extent can streaming infall influence the evolution of a planet-forming system? I will present two case studies: a study of dust properties across the envelope of a Class 0/I object, L1527 IRS; and the first ALMA dual-band dust analysis of a streamer infalling on a young source in the Orion molecular cloud.