Young ages and other intriguing properties of massive compact galaxies in the Local Universe

TL;DR

This study investigates nearby massive compact galaxies, revealing their young ages, fast rotation, and recent intense star formation, offering insights into their high-redshift counterparts and challenging existing galaxy classification models.

Contribution

It provides detailed kinematic, morphological, and stellar population analysis of local compact galaxies, highlighting their unique properties and recent starburst histories not seen in other galaxy types.

Findings

Nearby compact galaxies are fast rotators with elongated shapes.

They have young stellar populations with ages less than 2 Gyr.

These galaxies experienced recent, large starburst events.

Abstract

We characterize the kinematics, morphology, stellar populations and star formation histories of a sample of massive compact galaxies in the nearby Universe, which might provide a closer look to the nature of their high redshift (z > 1.0) massive counterparts. We find that nearby compact massive objects show elongated morphologies and are fast rotators. New high-quality long-slit spectra show that they have young mean luminosity-weighted ages (< 2Gyr) and solar metallicities or above ([Z/H]> 0.0). No significant stellar population gradients are found. The analysis of their star formation histories suggests that these objects have experienced recently enormous bursts which, in some cases, represent unprecedented large fractions of their total stellar mass. These galaxies seem to be truly unique, as they do not follow the characteristic kinematical and stellar population patterns of present-day massive ellipticals, spirals or even dwarfs.