Bibcode
Comerón, S.; Salo, H.; Knapen, J. H.; Peletier, R. F.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 623, id.A89, 24 pp.
Fecha de publicación:
3
2019
Revista
Número de citas
25
Número de citas referidas
20
Descripción
Thick discs are nearly ubiquitous components of the discs of present-day
galaxies. It has been proposed that a fraction of their stars have been
accreted. Here, we aim to find whether accretion of satellites is the
main formation mechanism of thick discs. To do so, we observed a sample
of eight nearby edge-on galaxies with the Multi-Unit Spectroscopic
Explorer (MUSE) integral field unit at the Very Large Telescope (VLT).
Six of the galaxies have a distinct thick disc. We derived thick-disc
velocities and velocity dispersions for the galaxies in our sample. We
devise a formalism to estimate the fractions of retrograde material in
the thick discs by using kinematical maps and thin/thick disc
decompositions. None of the galaxies in our sample show strong evidence
for retrograde material at large distances from the centre. Including
those found in the literature, there are seventeen thick discs with
studied kinematics, with only one showing unambiguous signatures of
retrograde material. Literature numerical studies of dynamical friction
allow us to estimate that at the current cosmic time about one in six
mergers for which the stars of the accreted galaxy ended in a thick disc
were retrograde. This is in tension with the observed fraction of
galaxies with a partly retrograde thick disc (one in seventeen). We
conclude that satellite accretion is not favoured by observations to be
the main formation mechanism of thick discs.
Based on observations made at the European Southern Observatory using
the VLT under programmes 096.B-0054(A) and 097.B-0041(A).The reduced
datacubes and the data required to recreate the kinematical maps shown
in Appendix A are available to the community. The data for each galaxy
in our sample can be accessed through the following links: http://ESO 157-49, http://ESO 443-21, http://ESO
469-15, http://ESO 544-27, http://IC 217, http://IC 1553, http://PGC
28308, and http://PGC 30591.
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