The NIR structure of the barred galaxy NGC253 from VISTA
  [abridged] We used J and Ks band images acquired with the VISTA telescope as
part of the science verification to quantify the structures in the stellar disk
of the barred Sc galaxy NGC253. Moving outward from the galaxy center, we find
a nuclear ring within the bright 1 kpc diameter nucleus, then a bar, a ring
with 2.9 kpc radius. From the Ks image we obtain a new measure of the
deprojected length of the bar of 2.5 kpc. The bar's strength, as derived from
the curvature of the dust lanes in the J-Ks image, is typical of weak bars.
From the deprojected length of the bar, we establish the corotation radius
(R_CR=3 kpc) and bar pattern speed (Omega_b = 61.3 km /s kpc), which provides
the connection between the high-frequency structures in the disk and the
orbital resonances induced by the bar. The nuclear ring is located at the inner
Lindblad resonance. The second ring does not have a resonant origin, but it
could be a merger remnant or a transient structure formed during an
intermediate stage of the bar formation. The inferred bar pattern speed places
the outer Lindblad resonance within the optical disk at 4.9 kpc, in the same
radial range as the peak in the HI surface density. The disk of NGC253 has a
down-bending profile with a break at R~9.3 kpc, which corresponds to about 3
times the scale length of the inner disk. We discuss the evidence for a
threshold in star formation efficiency as a possible explanation of the steep
gradient in the surface brightness profile at large radii. The NIR photometry
unveils the dynamical response of the NGC253 stellar disk to its central bar.
The formation of the bar may be related to the merger event that determined the
truncation of stars and gas at large radii and the perturbation of the disk's
outer edge.
