The merger history of massive spheroids since z~1 is size independent

TL;DR

This study analyzes the merger history of massive spheroid galaxies since redshift ~1, finding that merger activity is independent of galaxy size, implying similar growth rates for both compact and extended spheroids.

Contribution

It provides evidence that merger activity since z~1 does not depend on galaxy size, suggesting uniform growth mechanisms across different spheroid sizes.

Findings

Companions are equally distributed around compact and extended spheroids.

Merger activity since z~1 is size-independent.

Both galaxy types grow in size at similar rates.

Abstract

Using a compilation of 379 massive (stellar mass M > 10^{11} M_Sun) spheroid-like galaxies from the near-infrared Palomar/DEEP-2 survey, we have probed, up to z~1, whether the presence of companions depends on the size of the host galaxies. We have explored the presence of companions with mass ratios down to 1:10 and 1:100, with respect to the central massive galaxy, and within a projected distance of 30, 50 and 100 kpc of these objects. We find evidence for these companions being equally distributed around both compact and extended massive spheroids. This finding suggests that, at least since z~1, the merger activity in these objects is rather homogeneous across the whole population and its merger history is not affected for the size of the host galaxy. Our result could indicate that both compact and extended massive spheroid-like galaxies are growing in size at the same rate.