Detections of Diffuse Interstellar Bands in the SDSS Low-resolution
  Spectra
  Diffuse interstellar bands (DIBs) have been discovered for almost a century,
but their nature remains one of the most challenging problems in astronomical
spectroscopy. Most recent work to identify and investigate the properties and
carriers of DIBs concentrates on high-resolution spectroscopy of selected
sight-lines. In this paper, we report detections of DIBs in the Sloan Digital
Sky Survey (SDSS) low-resolution spectra of a large sample of Galactic stars.
Using a template subtraction method, we have successfully identified the DIBs
$\lambda$$\lambda$5780, 6283 in the SDSS spectra of a sample of about 2,000
stars and measured their strengths and radial velocities. The sample is by far
the largest ever assembled. The targets span a large range of reddening, E(B-V)
~ 0.2 -- 1.0, and are distributed over a large sky area and involve a wide
range of stellar parameters (effective temperature, surface gravity and
metallicity), confirming that the carriers of DIBs are ubiquitous in the
diffuse interstellar medium (ISM). The sample is used to investigate relations
between strengths of DIBs and magnitudes of line-of-sight extinction, yielding
results (i.e., EW(5780)= 0.61 x E(B-V) and EW(6283) = 1.26 x E(B-V)) consistent
with previous studies. DIB features have also been detected in the
commissioning spectra of the Guoshoujing Telescope (LAMOST) of resolving power
similar to that of SDSS. Detections of DIBs towards hundreds of thousands of
stars are expected from the on-going and up-coming large scale spectroscopic
surveys such as RAVE, SDSS III and LAMOST, particularly from the LAMOST Digital
Sky Survey of the Galactic Anti-center (DSS-GAC). Such a huge database will
provide an unprecedented opportunity to study the demographical distribution
and nature of DIBs as well as using DIBs to probe the distribution and
properties of the ISM and the dust extinction.
