Towards DIB mapping in galaxies beyond 100 Mpc

A radial profile of the λ5780.5 diffuse interstellar band in AM 1353-272 B^⋆

¹ GEPI, Observatoire de Paris, CNRS, Université Paris-Diderot, Place Jules Janssen, 92190 Meudon, France
e-mail: ana.monreal-ibero@obspm.fr
² Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
³ Institut für Physik und Astronomie, Universität Potsdam, 14476 Golm, Germany
⁴ European Southern Observatory, 3107 Alonso de Córdova, Santiago, Chile
⁵ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁶ Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

Received: 10 February 2015
Accepted: 20 February 2015

Abstract

Context. Diffuse interstellar bands (DIBs) are non-stellar weak absorption features of unknown origin found in the spectra of stars viewed through one or several clouds of the interstellar medium (ISM). Research of DIBs outside the Milky Way is currently very limited. In particular, spatially resolved investigations of DIBs outside of the Local Group are, to our knowledge, inexistent.

Aims. In this contribution, we explore the capability of the high-sensitivity integral field spectrograph, MUSE, as a tool for mapping diffuse interstellar bands at distances larger than 100 Mpc.

Methods. We used MUSE commissioning data for AM 1353-272 B, the member with the highest extinction of the Dentist’s Chair, an interacting system of two spiral galaxies. High signal-to-noise spectra were created by co-adding the signal of many spatial elements distributed in a geometry of concentric elliptical half-rings.

Results. We derived decreasing radial profiles for the equivalent width of the λ5780.5 DIB both in the receding and approaching side of the companion galaxy up to distances of ~4.6 kpc from the centre of the galaxy. The interstellar extinction as derived from the Hα/Hβ line ratio displays a similar trend, with decreasing values towards the external parts. This translates into an intrinsic correlation between the strength of the DIB and the extinction within AM 1353-272 B, consistent with the currently existing global trend between these quantities when using measurements for Galactic and extragalactic sightlines.

Conclusions. It seems feasible to map the DIB strength in the Local Universe, which has up to now only been performed for the Milky Way. This offers a new approach to studying the relationship between DIBs and other characteristics and species of the ISM in addition to using galaxies in the Local Group or sightlines towards very bright targets outside the Local Group.