Bibcode
Martínez-Lombilla, C.; Knapen, J. H.
Bibliographical reference
Astronomy and Astrophysics, Volume 629, id.A12, 22 pp.
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9
2019
Journal
Citations
21
Refereed citations
17
Description
Context. Thick discs can give invaluable information on the formation
and evolution history of galaxies as most, if not all, disc galaxies
have a thin (classical) disc and a thick disc. Aims: We study the
structure of thick discs in extraordinary depth by reaching a surface
brightness limit of μrdeep ˜ 28.5-29 mag
arcsec-2 with combined g, r, i band images from the IAC
Stripe 82 Legacy Project. Methods: We present the
characterisation of the thick discs in a sample of five edge-on
galaxies. A study of the radial and vertical surface brightness profiles
is presented by comparing our data with point spread function (PSF)
deconvolved models. Our method begins with an analysis of the background
and masking processes. Then we consider the effects of the PSF through
galaxy modelling. The galaxy disc components are fitted considering that
the thin and thick discs are two stellar fluids that are gravitationally
coupled in hydrostatic equilibrium. Results: We find that effects
due to the PSF are significant when low surface brightness is reached,
especially in the vertical profiles, but it can be accounted for by
careful modelling. The galaxy outskirts are strongly affected by the
faint wings of the PSF, mainly by PSF-redistributed light from the thin
disc. This is a central problem for ultra-deep imaging. The thick-disc
component is required to reach satisfactory fit results in the more
complex galaxies in our sample, although it is not required for all
galaxies. When the PSF is ignored, the brightness of these structures
may be overestimated by up to a factor of ˜4. Conclusions:
In general, our results are in good agreement with those of previous
works, although we reach deeper surface brightness levels, so that the
PSF effects are stronger. We obtain scale heights and mass ratios of
thin and thick discs (zt, zT, and
MT/Mt), which provide excellent agreement with
previous studies. Our small initial sample provides evidence for aspects
of a wide variety of formation theories for the thick discs in disc
galaxies.
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