EPoS Contribution
EPoS Contribution
Angular momentum properties of young protostellar envelopes

Mathilde Gaudel
LERMA, Paris, FR
One of the main challenges to the formation of solar-like stars is the "angular momentum problem": if the angular momentum of the pre-stellar parent core is totally transferred to the central stellar embryo during the main accretion phase, the gravitational force can not counteract the centrifugal force and the embryo fragments prematurely before reaching the main sequence. To form a star such as our Sun, the gas of the rotating envelope needs to redistribute its angular momentum by 5 to 10 orders of magnitude before reaching the central stellar embryo. Class 0 protostars are key objects to identify the mechanisms responsible for the angular momentum redistribution : they grow by accretion of the matter from the surrounded envelope (Menv>>Mstar) extending to scales 10000 au. At the end of this cornerstone phase, most of the final stellar mass has been accreted and the embryo is surrounding by a large disk (~100 au). In order to tackle this issue, we used high angular resolution observations (0.5", i.e. ~50 au) from the CALYPSO IRAM large program for a sample of 12 Class 0 protostars with d<400 pc. We established, for the first time homogeneously in a large sample, robust constraints on the radial distributions of specific angular momentum within protostellar envelopes in a large range of scales from ~50 to 10000 au. Two distinct regimes are revealed: a constant profile at small scales (<1600 au) and an increasing of the angular momentum at larger radii (1600-10000 au). From the constant profile, I will discuss angular momentum conservation and disk formation as possible solutions to reconnect the angular momentum measured in the inner protostellar envelopes to what is expected in T-Tauri disks. Furthemore, velocity gradients observed on large scales (>3000 au) - that are historically used to measure the rotation of the core and quantify the angular momentum problem - are not due to pure envelope rotation. I will examine the influence of the interstellar filament dynamics (turbulence, collapse, shocks) within which protostars are buried and the imprints of the initial conditions of the pre-stellar phase in the large scales of the envelope.
Caption: Radial distribution of specific angular momentum. Left : Figure adapted from Figure 8 of Belloche et al. 2013 and from Ohashi et al. 1997. Right : zoom on the region where the angular momentum profiles of the 12 CALYPSO sources lie. The gray curve shows the median profile. In the two panels, the solid black line shows the best fit by a broken power-law model.
Collaborators:
A. Maury, CEA/AIM-DAp, FR
A. Belloche, MPIfR, DE
S. Maret, IPAG, FR
Ph. Andre, CEA/AIM-DAp, FR
Key publication

Suggested Session: Cores2Disks