The Specific Angular Momentum Radial Profile in Dense Cores: Improved Initial Conditions for Disk Formation

The determination of the specific angular momentum radial profile, j(r), in the early stages of star formation is crucial to constrain star and circumstellar disk formation theories. The specific angular momentum is directly related to the largest Keplerian disk possible, and it could constrain the angular momentum removal mechanism. We determine j(r) toward two Class 0 objects and a first hydrostatic core candidate in the Perseus cloud, which is consistent across all three sources and well fit with a single power-law relation between 800 and 10,000 au: j(fit) (r) = 10(-3.60 +/- 0.15)(r/1000 au)(1.80 +/- 0.04) km s(-1) pc. This power-law relation is in between solid body rotation (proportional to r(2)) and pure turbulence (proportional to r(1.5)). This strongly suggests that even at 1000 au, the influence of the dense core's initial level of turbulence or the connection between core and the molecular cloud is still present. The specific angular momentum at 10,000 au is approximate to 3X higher than previously estimated, while at 1000 au, it is lower by 2x. We do not find a region of conserved specific angular momentum, although it could still be present at a smaller radius. We estimate an upper limit to the largest Keplerian disk radius of 60 au, which is small but consistent with published upper limits. Finally, these results suggest that more realistic initial conditions for numerical simulations of disk formation are needed. Some possible solutions include: (a) using a larger simulation box to include some level of driven turbulence or connection to the parental cloud or (b) incorporating the observed j(r) to set up the dense core kinematics initial conditions.