S4G extension for nearby early-type galaxies

We showcase NIR scaling relations for ETGs among these quantities. We examine general trends across the whole S4G and ETG extension among our derived parameters, highlighting differences between ETGs and late-type galaxies (LTGs). ETGs are, on average, more massive and more concentrated than LTGs, and also show subtle distinctions among ETG morphological sub-types.

We also derive the following scaling relations and compare with previous results in visible light: mass-size (both half-light and isophotal), mass-concentration, mass-surface brightness (central, effective, and within 1kpc), and mass-color. We find good agreement with previous works, though some relations (e.g., mass-central surface brightness) will require more careful multi-component decompositions to be fully understood.

The relations between mass and isophotal radius and between mass and surface brightness within 1kpc, in particular, show notably small scatter. The former provides important constraints on the limits of size growth in galaxies, possibly related to star formation thresholds, while the latter-particularly when paired with the similarly tight relation for LTGs-showcases the striking self-similarity of galaxy cores, suggesting these evolve little over cosmic time.

All of the profiles and parameters described in this paper will be provided to the community via the NASA/IPAC database on a dedicated website.