Measuring the Diffuse Interstellar Bands at 5780, 5797, and 6614 {\AA} in Low-Resolution Spectra of Cool Stars from LAMOST

TL;DR

This study measures three diffuse interstellar bands (DIBs) in over two million low-resolution spectra from LAMOST, creating the largest dataset to date and producing the first Galactic maps of certain DIBs in the northern sky.

Contribution

Developed a pipeline to measure DIBs in low-resolution spectra, providing extensive new measurements and Galactic maps of DIBs, including the first in the northern hemisphere.

Findings

Measured DIBs in over 200 million spectra, with high-quality data for hundreds of thousands of sources.

First Galactic maps of DIBs λ5780 and λ6614 in the northern sky.

Determined central wavelengths and equivalent widths of DIBs with high precision.

Abstract

We attempt to measure the DIBs $\lambda$5780, $\lambda$5797 and $\lambda$6614 in over two million low-resolution spectra of cool stars from LAMOST. Based on the DIB measurements, the correlation between DIBs and extinction, the kinematics of DIBs, and the Galactic distribution of DIBs are reviewed and investigated from the perspective of statistics. A pipeline is developed to measure the DIBs $\lambda$5780, $\lambda$5797 and $\lambda$6614 in the LAMOST low-resolution spectra. We obtain the DIB measurements of spectra of late-type stars from LAMOST, and screen out 176,831, 13,473 and 110,152 high-quality (HQ) measurements of the DIBs $\lambda$5780, $\lambda$5797 and $\lambda$6614, respectively, corresponding to 142,074, 11,480 and 85,301 unique sources. Utilizing these HQ measurements, we present the Galactic maps of the DIBs $\lambda$5780 and $\lambda$6614 in the northern sky for the first time. The central wavelengths of the DIBs $\lambda$5780, $\lambda$5797 and $\lambda$6614 in air are determined to be 5780.48 $\pm$ 0.01, 5796.94 $\pm$ 0.02 and 6613.64 $\pm$ 0.01 {\AA}, respectively, based on their kinematics. The equivalent widths of these three DIBs per unit extinction are statistically fitted to be 0.565, 0.176 and 0.256 {\AA}/mag. As a part of our work, three catalogs of the HQ measurements for the DIBs $\lambda$5780, $\lambda$5797 and $\lambda$6614 are provided online. To the best of our knowledge, this is the largest number of measurements of these three DIBs to date. It is also the first time that the Galactic maps of the DIBs $\lambda$5780 and $\lambda$6614 in the northern hemisphere are presented, and the central wavelengths of the DIBs $\lambda$5780, $\lambda$5797 and $\lambda$6614 are estimated from the kinematics.