Near-infrared diffuse interstellar bands in APOGEE telluric standard
  star spectra: weak bands and comparisons with optical counterparts
  Information on the existence and properties of diffuse interstellar bands
(DIBs) outside the optical domain is still limited. Additional infra-red (IR)
measurements and IR-optical correlative studies are needed to constrain DIB
carriers and locate various absorbers in 3D maps of the interstellar matter. We
extended our study of H-band DIBs in Apache Point Observatory Galactic
Evolution Experiment (APOGEE) Telluric Standard Star (TSS) spectra. We used the
strong 15273A band to select the most and least absorbed targets. We used
individual spectra of the former subsample to extract weaker DIBs, and we
searched the two stacked series for differences that could indicate additional
bands. High-resolution NARVAL and SOPHIE optical spectra for a subsample of 55
TSS targets were additionally recorded for NIR/optical correlative studies.
From the TSS spectra we extract a catalog of measurements of the poorly studied
15617, 15653, and 15673A DIBs in about 300 sightlines, we obtain a first
accurate determination of their rest wavelength and constrained their intrinsic
width and shape. In addition, we studied the relationship between these weak
bands and the strong 15273A DIB. We provide a first or second confirmation of
several other weak DIBs that have been proposed based on different instruments,
and we add new constraints on their widths and locations. We finally propose
two new DIB candidates. We compared the strength of the 15273A absorptions with
their optical counterparts 5780, 5797, 6196, 6283, and 6614A. Using the
5797-5780 ratio as a tracer of shielding against the radiation field, we showed
that the 15273A DIB carrier is significantly more abundant in unshielded
(sigma-type) clouds, and it responds even more strongly than the 5780A band
carrier to the local ionizing field.
