Diffuse Interstellar Bands vs. Known Atomic and Molecular Species in the
  Interstellar Medium of M82 toward SN 2014J
  We discuss the absorption due to various constituents of the interstellar
medium of M82 seen in moderately high resolution, high signal-to-noise ratio
optical spectra of SN 2014J. Complex absorption from M82 is seen, at velocities
45 $\le$ $v_{\rm LSR}$ $\le$ 260 km s$^{-1}$, for Na I, K I, Ca I, Ca II, CH,
CH$^+$, and CN; many of the diffuse interstellar bands (DIBs) are also
detected. Comparisons of the column densities of the atomic and molecular
species and the equivalent widths of the DIBs reveal both similarities and
differences in relative abundances, compared to trends seen in the ISM of our
Galaxy and the Magellanic Clouds. Of the ten relatively strong DIBs considered
here, six (including $\lambda$5780.5) have strengths within $\pm$20% of the
mean values seen in the local Galactic ISM, for comparable N(K I); two are
weaker by 20--45% and two (including $\lambda$5797.1) are stronger by 25--40%.
Weaker than "expected" DIBs [relative to N(K I), N(Na I), and E(B-V)] in some
Galactic sight lines and toward several other extragalactic supernovae appear
to be associated with strong CN absorption and/or significant molecular
fractions. While the N(CH)/N(K I) and N(CN)/N(CH) ratios seen toward SN 2014J
are similar to those found in the local Galactic ISM, the combination of high
N(CH$^+$)/N(CH) and high W(5797.1)/W(5780.5) ratios has not been seen
elsewhere. The centroids of many of the M82 DIBs are shifted, relative to the
envelope of the K I profile -- likely due to component-to-component variations
in W(DIB)/N(K I) that may reflect the molecular content of the individual
components. We compare estimates for the host galaxy reddening E(B-V) and
visual extinction A$_{\rm V}$ derived from the various interstellar species
with the values estimated from optical and near-IR photometry of SN 2014J.
