Near-infrared diffuse interstellar bands in 0.91-1.32 micron [GA]

We present a comprehensive survey of diffuse interstellar bands (DIBs) in $0.91-1.32\mu$m with a newly-developed near-infrared (NIR) spectrograph, WINERED, mounted on the Araki 1.3 m Telescope in Japan. We obtained high-resolution ($R=28,300$) spectra of 25 early-type stars with color excesses of $0.07<E(B-V)<3.4$. In addition to the four DIBs previously detected in this wavelength range, we identified 16 new DIBs, eight of which were reported as DIB “candidates” by Cox. We analyze the correlations among NIR DIBs, strong optical DIBs, and the reddening of the stars. Consequently, we found that all NIR DIBs show weaker correlations with the reddening rather than the optical DIBs, suggesting that the equivalent widths of NIR DIBs depend on some physical conditions of the interstellar clouds, such as UV flux. Three NIR DIBs, $\lambda\lambda$10780, 10792, and 11797, are found to be classifiable as a “family,” in which the DIBs are well correlated with each other, suggesting that the carriers of these DIBs are connected with some chemical reactions and/or have similar physical properties such as ionization potential. We also found that three strongest NIR DIBs $\lambda\lambda10780, 11797, 13175$ are well correlated with the optical DIB $\lambda 5780.5$, whose carrier is proposed to be a cation molecule with high ionization potential, indicating that the carriers of the NIR DIBs could be cation molecules.

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S. Hamano, N. Kobayashi, S. Kondo, et. al.
Fri, 12 Dec 14

Comments: 21 pages, 12 Figures, accepted for The Astrophysical Journal