Pre-Main-Sequence Accretion in the Low Metallicity Galactic Star-forming Region Sh 2-284

V. M. Kalari*, J. S. Vink

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)

Abstract

We present optical spectra of pre-main-sequence (PMS) candidates around the Ha 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 similar to 1/5 Z(circle dot). It has been suggested on the basis of both theory and observations that PMS mass-accretion rates, (M) over dot(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 H alpha emission in intermediate-resolution R-band spectroscopy. Our total sample includes 24 objects spanning a mass range between 1 and 2 M-circle dot 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 (M) over dot(acc) in the 1-2 M-circle dot interval to depend quasi-quadratically on stellarmass, with (M) over dot(acc) proportional to M-*(2.4 +/- 0.35), and inversely with stellar age, with (M) over dot(acc) proportional to t(*)(-0.7 +/- 0.4). Furthermore, we compare our spectroscopic (M) over dot(acc) measurements with solar Z Galactic PMS stars in the same mass range, but, surprisingly find no evidence for a systematic change in (M) over dot(acc) with Z. We show that literature accretion-rate studies are influenced by detection limits, and we suggest that (M) over dot(acc) may be controlled by factors other than Z(*), M-*, and age.

Original languageEnglish
Article number113
Number of pages13
JournalAstrophysical Journal
Volume800
Issue number2
DOIs
Publication statusPublished - 20 Feb 2015

Keywords

  • accretion, accretion disks
  • stars: formation
  • stars: fundamental parameters
  • stars: pre-main sequence
  • stars: variables: T Tauri, Herbig Ae/Be
  • LARGE-MAGELLANIC-CLOUD
  • T-TAURI STARS
  • HERBIG AE/BE STARS
  • YOUNG STELLAR OBJECTS
  • ORION NEBULA CLUSTER
  • LOW-MASS STARS
  • PHOTOMETRIC-DETERMINATION
  • PROTOPLANETARY DISKS
  • CANDIDATE STARS
  • BROWN DWARFS

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