We want to quantify the structures in the stellar disk of the barred Sc galaxy NGC 253 located in the Sculptor group , at 3.47Â Mpc distance .
We used J and Ks band images acquired with the VISTA telescope as part of the science verification .
The wide field of view and the high angular resolution of this survey facility allow mapping the large and small scale structure of the stellar disk in NGCÂ 253 .
We used unsharp masking and two-dimensional modeling of the smooth light distribution in the disk to identify and measure the substructures induced by the bar in the stellar disk of NGCÂ 253 .
We built azimuthally-averaged profiles in the J and Ks bands to measure the radial surface brightness profile of the central bulge , bar and disk .
Moving outward from the galaxy center , we find a nuclear ring within the bright 1Â kpc diameter nucleus , then a bar , a ring with 2.9 kpc radius , and spiral arms in the outer disk .
From the Ks image we obtain a new measure of the deprojected length of the bar of 2.5Â kpc .
The bar ’ s strength , as derived from the curvature of the dust lanes in the J-Ks image , is typical of weak bars with \Delta \alpha = 25 degree/kpc .
From the deprojected length of the bar , we establish the corotation radius ( R _ { CR } = 3 Â kpc ) and bar pattern speed ( \Omega _ { b } = 61.3 kms ^ { -1 } Â kpc ^ { -1 } ) , 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 ( at 2.9Â kpc ) 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 4.9Â kpc , in the same radial range as the peak in the HI surface density .
The disk of NGCÂ 253 has a down-bending profile with a break at R \sim 9.3Â 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 NGCÂ 253 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 .