Dense molecular clouds in the SN2008fp host galaxy?

Accepted for publication in A&A. Context. Supernovae (SNe) offer a unique opportunity to study physical properties, small-scale structure, and complex organic chem-istry of the interstellar medium (ISM) in different galaxies. Aims. Interstellar absorption features, such as atomic and molecular lines as well as diffuse interstellar bands (DIBs), can be used to study the physical properties of extra-galactic diffuse interstellar clouds. Methods. We used optical high-resolution spectroscopy to study the properties of the ISM in the SN 2008fp host galaxy, ESO428-G14. The properties of intervening dust were investigated via spectropolarimetry. Results. The spectra of SN 2008fp reveal a complex of diffuse atomic clouds at radial velocities in line with the systematic velocities of the host galaxy. In addition, a translucent (AV ∼ 1.5 mag) cloud is detected at a heliocentric velocity of 1770 km s−1 (redshifted by 70 km s−1 with respect to the system velocity). This cold dense cloud is rich in dense atomic gas tracers, molecules, as well as diffuse interstellar bands. We have detected both C2 and C3 for the first time in a galaxy beyond the Local Group. The CN (0,0) band-line ratios are consistent with an excitation temperature of T = 2.9 ± 0.3 K. The interstellar polarisation law deviates significantly from what is observed in the Galaxy, indicating substantial differences in the host dust/size composition. No variations over a period of about one month are observed in any of the interstellar medium tracers