The Fundamental Plane Is Not a Plane: Warped Nature of the Fundamental Plane of Early-type Galaxies and Its Implication for Galaxy Formation

Abstract

Based on $16,283$ early-type galaxies (ETGs) in $0.025\le z_{\mathrm{spec}}<0.055$ from Sloan Digital Sky Survey data, we show that the fundamental plane (FP) of ETGs is not a plane in the strict sense but is a curved surface with a twisted shape whose orthogonal direction to the surface is shifted as the central velocity dispersion (${\sigma }_0$) or mean surface brightness within the half-light radius (${\mu }_e$) changes. When ETGs are divided into subsamples according to ${\sigma }_0$, the coefficient of ${\mu }_e$ of the FP increases, whereas the zero-point of the FP decreases at higher ${\sigma }_0$. Taking the $z$ band as an example, the coefficient of ${\mu }_e$ rises from $0.28$ to $0.36$ as ${\sigma }_0$ increases from $\sim 100$ to $\sim 300$ km s${}^{-1}$. At the same time, the zero-point of the FP falls from $-7.5$ to $-9.0$ in the same ${\sigma }_0$ range. The consistent picture on the curved nature of the FP is also reached by inspecting changes in the FP coefficients for ETG subsamples with different ${\mu }_e$. By examining scaling relations that are projections of the FP, we suggest that the warped nature of the FP may originate from dry merger effects that are imprinted more prominently in ETGs with higher masses.

20 pages, 15 figures, 4 tables, accepted for publication in the ApJ

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Cited by in corpus (4)

• Impact of Galaxy Mergers on Stellar Population Profiles of Early-type Galaxies
• The Most Massive Early-type Galaxies Exhibit Tidal Features More Frequently in Lower-density Environments
• The hyperplane of early-type galaxies: using stellar population properties to increase the precision and accuracy of the fundamental plane as a distance indicator
• Is there a tilt in the fundamental (hyper)plane?