Disk-Braking in Young Stars: Probing Rotation in Chamaeleon I and Taurus-Auriga

TL;DR

This study investigates the rotation, disk presence, and accretion in young T Tauri stars in Chamaeleon I and Taurus-Auriga, finding no clear disk braking signature and revealing mass-dependent rotation and angular momentum patterns.

Contribution

It provides the first comprehensive analysis of rotation and disk signatures in these regions, challenging previous notions of disk braking effects in young star clusters.

Findings

No clear disk braking signature detected in Tau-Aur and Cha I.

Rotational velocities depend on stellar mass, with F--K stars rotating faster than M stars.

Angular momentum scales with mass as M^0.5, differing from other clusters.

Abstract

We present a comprehensive study of rotation, disk and accretion signatures for 144 T Tauri stars in the young (~2 Myr old) Chamaeleon I and Taurus-Auriga star forming regions based on multi-epoch high-resolution optical spectra from the Magellan Clay 6.5 m telescope supplemented by mid-infared photometry from the Spitzer Space Telescope. In contrast to previous studies in the Orion Nebula Cluster and NGC 2264, we do not see a clear signature of disk braking in Tau-Aur and Cha I. We find that both accretors and non-accretors have similar distributions of v sin i. The rotational velocities in both regions show a clear mass dependence, with F--K stars rotating on average about twice as fast as M stars, consistent with results reported for other clusters of similar age. Similarly, we find the upper envelope of the observed values of specific angular momentum j varies as M^0.5 for our sample which spans a mass range of ~0.16 to ~3 M_sun. This power law complements previous studies in Orion which estimated j is proportional to M^0.25 for < ~2 Myr stars in the same mass regime, and a sharp decline in j with decreasing mass for older stars (~10 Myr) with M < 2 M_sun. For a subsample of 67 objects with mid-IR photometry, we examine the connection between accretion signatures and dusty disks: in the vast majority of cases (63/67), the two properties correlate well, which suggests that the timescale of gas accretion is similar to the lifetime of inner disks.