Bibcode
Monreal-Ibero, A.; Weilbacher, P. M.; Wendt, M.
Bibliographical reference
Astronomy and Astrophysics, Volume 615, id.A33, 12 pp.
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7
2018
Journal
Citations
13
Refereed citations
11
Description
Context. Diffuse interstellar bands (DIBs) are faint spectral absorption
features of unknown origin. Research on DIBs beyond the Local Group is
very limited and will surely blossom in the era of the Extremely Large
Telescopes. However, we can already start paving the way. One
possibility that needs to be explored is the use of high-sensitivity
integral field spectrographs. Aims: Our goals are twofold. First,
we aim to derive reliable mapping of at least one DIB in a galaxy
outside the Local Group. Second, we want to explore the relation between
DIBs and other properties of the interstellar medium (ISM) in the
galaxy. Methods: We use Multi Unit Spectroscopic Explorer (MUSE)
data for the Antennae Galaxy, the closest major galaxy merger. High
signal-to-noise spectra were created by co-adding the signal of many
spatial elements with the Voronoi binning technique. The emission of the
underlying stellar population was modelled and substracted with the
STARLIGHT spectral synthesis code. Flux and equivalent width of the
features of interest were measured by means of fitting to Gaussian
functions. Results: To our knowledge, we have derived the first
maps for the DIBs at λ5780 and λ5797 in galaxies outside
the Local Group. The strongest of the two DIBs (at λ5780) was
detected in an area of 0.6□', corresponding to a linear scale of
25 kpc2. This region was sampled using >200 out of 1200
independent lines of sight. The DIB λ5797 was detected in >100
independent lines of sight. Both DIBs are associated with a region of
high emission in the H I 21 cm line, implying a connection between
atomic gas and DIBs, as the correlations in the Milky Way also suggest.
Conversely, there is mild spatial association between the two DIBs and
the molecular gas, in agreement with results for our Galaxy that
indicate a lack of correlation between DIBs and molecular gas. The
overall structures for the DIB strength distribution and extinction are
comparable. Within the system, the λ5780 DIB clearly correlates
with the extinction, and both DIBs follow the relationship between
equivalent width and reddening when data for several galaxies are
considered. This relationship is tighter when comparing only with
galaxies with metallicities close to solar. Unidentified infrared
emission bands (UIBs, likely caused by polycyclic aromatic hydrocarbons
PAHs) and the λ5780 and λ5797 DIBs show similar but not
identical spatial distributions. We attribute the differences to
extinction effects without necessarily implying a radically different
nature of the respective carriers. Conclusions: The results
illustrate the enormous potential of integral field spectrographs for
extragalactic DIB research.
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