A Search for Strongly Mg-enhanced Stars from the Sloan Digital Sky
  Survey
  Strongly Mg-enhanced stars with [Mg/Fe] $>$ 1.0 show peculiar abundance
patterns and hence are of great interest for our understanding of stellar
formation and chemical evolution of the Galaxy. A systematical search for
strongly Mg-enhanced stars based on the low-resolution $(R\simeq2000)$ spectra
of the Sloan Digital Sky Survey (SDSS) is carried out by finding the best
matched synthetic spectrum to the observed one in the region of Mg I b lines
around $\lambda$5170\AA$~$via a profile matching method. The advantage of our
method is that fitting parameters are refined by reproducing the [Mg/Fe] ratios
of 47 stars from very precise high-resolution spectroscopic (HRS) analysis by
Nissen and Schuster (2010); and these parameters are crucial to the precision
and validity of the derived Mg abundances. As a further check of our method, Mg
abundances are estimated with our method for member stars in four Galactic
globular clusters (M92, M13, M3, M71) which cover the same metallicity range as
our sample, and the results are in good agreement with those of HRS analysis in
the literature. The validation of our method is also proved by the agreement of
[Mg/Fe] between our values and those of HRS analysis by Aoki et al.(2013).
Finally, 33 candidates of strongly Mg-enhanced stars with [Mg/Fe]$>$1.0 are
selected from 14850 F and G stars. Follow-up observations will be carried out
on these candidates with high-resolution spectroscopy by large telescopes in
the near future, so as to check our selection procedure and to perform a
precise and detailed abundance analysis and to explore the origins of these
stars.
