Disk Galaxies
Disk galaxies play a fundamental role for our understanding of galaxy
evolution in a cosmological context.
We have constructed one of the largest kinematic samples of distant
disks to date using VLT/FORS spectroscopy and HST/ACS imaging
(Böhm et al. 2004;
Böhm & Ziegler 2007).
The data set has grown successively over the years and now
contains ~250 objects up to redshifts z~1.
From the emission lines of the optical spectra, we extracted
spatially resolved rotation curves (i.e.
rotation velocities as a function of galactocentric radius).
To determine the intrinsic maximum rotation velocity
V
max, I developed a code that
takes into account all geometrical and observational effects (such as
seeing or the impact of the slit width).
Based on the key parameter V
max,
we investigated the evolution of galaxy scaling relations, like the correlation
between V
max and luminosity
(aka Tully-Fisher relation) or the correlation between
V
max and disk size (velocity-size relation).
We found that, at given V
max, disks at
z=1 were brighter by ~1 mag in the B-band
and had only ~70% the size of
their present-day counterparts
(Böhm & Ziegler 2016).
The combined evolution in size and luminosity (represented by the
offsets ΔM
B from the Tully-Fisher relation and the
offsets Δlogr
d from the velocity-size relation)
is equivalent to an edge-on view on the fundamental
plane of late-type galaxies, see Fig. 1.
Fig.1:
Offsets ΔMB from the local Tully-Fisher relation (x-axis)
and offsets Δlogrd from the local velocity-size relation (y-axis)
in the local universe (upper left plot; error bars omitted for clarity) and in three redshift bins for our distant spiral data. Towards higher redshifts, disk galaxies become more luminous and smaller compared to their present-day counterparts (however, the ones with the strongest evolution in luminosity are not the ones with strongest size evolution and vice versa). The black dashed and dotted lines show a linear fit to the local data along with the 3σ scatter; the solid colored lines denote fits to the distant data.
In a complementary analysis, we used models of chemical enrichment to
approximate the star formation histories of disk galaxies over the past 8 Gyr.
This revealed a down-sizing effect in the sense that
high-mass disk galaxies began forming their stars at higher
redshifts and on shorter timescales than low-mass ones
(Ferreras, Böhm, et al. 2014).