High-resolution spectroscopy in TR 37: Gas accretion evolution in evolved dusty disks

Using the Hectochelle multifiber spectrograph, we have obtained high-resolution (R similar to 34,000) spectra in the H alpha region for a large number of stars in the 4 Myr old cluster Tr 37, containing 146 previously known members and 26 newly identified ones. We present the H alpha line profiles of all members, compare them to our IR observations of dusty disks (Two Micron All Sky Survey JHK + IRAC + MIPS 24 mu m), use the radial velocities as a membership criterion, and calculate the rotational velocities. We find a good correlation between the accretion-broadened profiles and the presence of protoplanetary disks, noting that a small fraction of the accreting stars presents broad profiles with H alpha equivalent widths smaller than the canonical limit separating classical T Tauri stars (CTTSs) and weak-lined T Tauri stars (WTTSs). The number of strong accretors appears to be lower than in younger regions, and a large number of CTTSs have very small accretion rates (M