SPIDER II - The Fundamental Plane of Early-type Galaxies in grizYJHK

TL;DR

This study analyzes the Fundamental Plane of early-type galaxies across multiple wavebands, revealing how structural and stellar population properties vary with galaxy size, mass, and environment, and comparing observations with galaxy formation models.

Contribution

It provides a comprehensive analysis of the FP in 39,993 ETGs across grizYJHK bands, including detailed bias correction and the relation of FP parameters to galaxy structure and stellar populations.

Findings

The Kormendy relation slope varies from g to K bands, indicating size-dependent optical/NIR ratios.

The Faber-Jackson relation slope is consistent across wavebands, with a mean of 0.198.

The FP tilt increases with Sersic index and axis ratio, linked to structural and dynamical differences.

Abstract

We present a complete analysis of the Fundamental Plane of early-type galaxies (ETGs) in the nearby universe. The sample, as defined in paper I, comprises 39,993 ETGs located in environments covering the entire domain in local density (from field to cluster). We derive the FP of ETGs in the grizYJHK wavebands with a detailed discussion on fitting procedure, bias due to selection effects and bias due to correlated errors on r_e and mue as key factors in obtaining meaningful FP coefficients. Studying the Kormendy relation we find that its slope varies from g (3.44+-0.04) to K (3.80+-0.02) implying that smaller size ETGs have a larger ratio of optical/NIR radii than galaxies with larger re. We also examine the Faber-Jackson relation and find that its slope is similar for all wavebands, within the uncertainties, with a mean value of 0.198+-0.007. The variation of the FP coefficients for the magnitude selected sample from g through K amounts to 11%, negligible, and 10%, respectively. We find that the tilt of the FP becomes larger for higher Sersic index and larger axis ratios, independent of the waveband we measured the FP variables. This suggests that these variations are likely related to structural and dynamical differences of galaxian properties. We also show that the current semi-analytical models of galaxy formation reproduce very well the variation of age and metallicity of the stellar populations present in massive ETGs as a function of the stellar mass in these systems. In particular, we find that massive ETGs have coeval stellar pops with age varying only by a few % per decade in mass, while metallicity increases with stellar mass by 23% per mass decade.