Detections of Diffuse Interstellar Bands in the SDSS Low-resolution Spectra

TL;DR

This study detects diffuse interstellar bands (DIBs) in low-resolution SDSS spectra of about 2,000 stars, confirming their ubiquity and relation to interstellar extinction, and demonstrates the potential of large-scale surveys for DIB research.

Contribution

First large-scale detection of DIBs in low-resolution spectra across a broad stellar sample, expanding understanding of DIB distribution and properties in the diffuse interstellar medium.

Findings

DIBs λ5780 and λ6283 detected in SDSS spectra of ~2,000 stars

DIB strengths correlate with line-of-sight extinction (E(B-V))

DIBs also detected in LAMOST spectra, enabling large-scale ISM studies

Abstract

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.