The MASSIVE Survey. XVIII. Deep Wide-Field $K$-band Photometry and Local Scaling Relations for Massive Early-Type Galaxies

TL;DR

This study provides deep K-band photometry of 98 massive early-type galaxies, revealing curved size-luminosity and Faber-Jackson relations that suggest different formation histories for galaxy subtypes and support dissipationless merger models.

Contribution

It presents new wide-field K-band photometry data and analyzes the scaling relations of massive ETGs, highlighting curvature and differences between fast and slow rotators.

Findings

Curvature in size-luminosity and velocity dispersion-luminosity relations.

Slow rotators show different slopes, indicating varied formation histories.

Dynamical mass-luminosity relation follows a single power-law, consistent with fundamental plane tilt.

Abstract

We present wide-field, deep $K$-band photometry of 98 luminous early-type galaxies (ETGs) from the MASSIVE survey based on observations taken with the WIRCam instrument on the Canada-France-Hawaii Telescope. Using these images, we extract accurate total $K$-band luminosities ($L_K$) and half-light radii ($R_e$) for this sample of galaxies. We use these new values to explore the size-luminosity and Faber-Jackson relations for massive ETGs. Within this volume-limited sample, we find clear evidence for curvature in both relations, indicating that the most luminous galaxies tend to have larger sizes and smaller velocity dispersions than expected from a simple power-law fit to less luminous galaxies. Our measured relations are qualitatively consistent with the most massive elliptical galaxies forming largely through dissipationless mergers. When the sample is separated into fast and slow rotators, we find the slow rotators to exhibit similar changes in slope with increasing $L_K$, suggesting that low-mass and high-mass slow rotators have different formation histories. The curvatures in the $R_e-L_K$ and $\sigma-L_K$ relations cancel, leading to a relation between dynamical mass and luminosity that is well described by a single power-law: $R_e\sigma^2 \propto {L_K}^b$ with $b \approx 1.2$. This is consistent with the tilt of the fundamental plane observed in lower mass elliptical galaxies.