We present a detailed analysis of the photometric properties of galaxies in the cluster \mathrm { A 2163 } B at redshift z \sim 0.2 .
R- , I- and K-band structural parameters , ( half light radius \mathrm { R _ { e } } , mean surface brightness \mathrm { < \mu > _ { e } } within \mathrm { R _ { e } } and Sersic index \mathrm { n } ) are derived for N \sim 60 galaxies , and are used to study their internal colour gradients .
For the first time , we use the slopes of optical-NIR Kormendy relations to study colour gradients as a function of galaxy size , and we derive the Photometric Plane at z \sim 0.2 in the K band .
Colour gradients are negligible at optical wavelengths , and are negative in the optical-NIR , amounting on average to -0.48 \pm 0.06 .
This result is in agreement with our previous measurements of colour gradients at intermediate redshifts , and imply a metallicity gradient in galaxies of \sim 0.2 ~ { } dex per radial decade .
The analysis of the Kormendy relation suggests that its slope increases from the optical to the NIR , implying that colour gradients do not vary or even do become less steep in more massive galaxies .
Such a result is not simply accomodated within a monolithic collapse scenario , while it can be well understood within a hierarchical merging framework .
Finally , we derive the first NIR Photometric Plane at z \sim 0.2 , accounting for both the correlations on the measurement uncertainties and the selection effects .
The Photometric Plane at z \sim 0.2 is consistent with that at z \sim 0 , with an intrinsic scatter significantly smaller than the Kormendy relation but larger than the Fundamental Plane .