  Large-scale asymmetries (i.e. lopsidedness) are a common feature in the
stellar density distribution of nearby disk galaxies both in low- and
high-density environments. In this work, we characterize the present-day
lopsidedness in a sample of 1435 disk-like galaxies selected from the TNG50
simulation. We find that the percentage of lopsided galaxies (10%-30%) is in
good agreement with observations if we use similar radial ranges to the
observations. However, the percentage (58%) significantly increases if we
extend our measurement to larger radii. We find a mild or lack of correlation
between lopsidedness amplitude and environment at z=0 and a strong correlation
between lopsidedness and galaxy morphology regardless of the environment.
Present-day galaxies with more extended disks, flatter inner galactic regions
and lower central stellar mass density (i.e. late-type disk galaxies) are
typically more lopsided than galaxies with smaller disks, rounder inner
galactic regions and higher central stellar mass density (i.e. early-type disk
galaxies). Interestingly, we find that lopsided galaxies have, on average, a
very distinct star formation history within the last 10 Gyr, with respect to
their symmetric counterparts. Symmetric galaxies have typically assembled at
early times (~8-6 Gyr ago) with relatively short and intense bursts of central
star formation, while lopsided galaxies have assembled on longer timescales and
with milder initial bursts of star formation, continuing building up their mass
until z=0. Overall, these results indicate that lopsidedness in present-day
disk galaxies is connected to the specific evolutionary histories of the
galaxies that shaped their distinct internal properties.
