2015ApJ...800..113K

We present optical spectra of pre-main-sequence (PMS) candidates around the Hα region taken with the Southern African Large Telescope in the low metallicity (Z) Galactic region Sh 2-284, which includes the open cluster Dolidze 25 with an atypical low metallicity of Z ∼ 1/5 Z_☉. It has been suggested on the basis of both theory and observations that PMS mass-accretion rates, {dot}M_acc, are a function of Z. We present the first sample of spectroscopic estimates of mass-accretion rates for PMS stars in any low-Z star-forming region. Our data set was enlarged with literature data of Hα emission in intermediate-resolution R-band spectroscopy. Our total sample includes 24 objects spanning a mass range between 1 and 2 M_☉ and with a median age of approximately 3.5 Myr. The vast majority (21 out of 24) show evidence for a circumstellar disk on the basis of Two Micron All Sky Survey and Spitzer infrared photometry. We find {dot}M_acc in the 1-2 M_☉interval to depend quasi-quadratically on stellar mass, with {dot}M_acc ∝ {dot}M_* ^2.4 ± 0.35^, and inversely with stellar age, with {dot}M_acc ∝ t_* ^-0.7 ± 0.4^. Furthermore, we compare our spectroscopic {dot}M_acc measurements with solar Z Galactic PMS stars in the same mass range, but, surprisingly find no evidence for a systematic change in {dot}M_acc with Z. We show that literature accretion-rate studies are influenced by detection limits, and we suggest that {dot}M_acc may be controlled by factors other than Z_*, M_*, and age.