NEAR-INFRARED DIFFUSE INTERSTELLAR BANDS IN 0.91-1.32 μm

Abstract

We present a comprehensive survey of diffuse interstellar bands (DIBs) in\n$0.91-1.32\\mu$m with a newly-developed near-infrared (NIR) spectrograph,\nWINERED, mounted on the Araki 1.3 m Telescope in Japan. We obtained\nhigh-resolution ($R=28,300$) spectra of 25 early-type stars with color excesses\nof $0.07<E(B-V)<3.4$. In addition to the five DIBs previously detected in this\nwavelength range, we identified 15 new DIBs, 7 of which were reported as DIB\n"candidates" by Cox. We analyze the correlations among NIR DIBs, strong optical\nDIBs, and the reddening of the stars. Consequently, we found that all NIR DIBs\nshow weaker correlations with the reddening rather than the optical DIBs,\nsuggesting that the equivalent widths of NIR DIBs depend on some physical\nconditions of the interstellar clouds, such as UV flux. Three NIR DIBs,\n$\\lambda\\lambda$10780, 10792, and 11797, are found to be classifiable as a\n"family," in which the DIBs are well correlated with each other, suggesting\nthat the carriers of these DIBs are connected with some chemical reactions\nand/or have similar physical properties such as ionization potential. We also\nfound that three strongest NIR DIBs $\\lambda\\lambda10780, 11797, 13175$ are\nwell correlated with the optical DIB $\\lambda 5780.5$, whose carrier is\nproposed to be a cation molecule with high ionization potential, indicating\nthat the carriers of the NIR DIBs could be cation molecules.\n