The intriguing life of star-forming galaxies in the redshift range 1 < z < 2 using MASSIV

TL;DR

This study uses the MASSIV survey to analyze the kinematics and merger history of star-forming galaxies at redshifts 1 to 2, revealing high merger rates and diverse metallicity distributions, which inform galaxy evolution models.

Contribution

It provides new insights into the kinematic properties and merger rates of galaxies in the early universe using integral field spectroscopy data.

Findings

58% of galaxies are slow rotators, suggesting merger-driven formation.

Average of 0.4 major mergers per galaxy since 9.5 Gyr ago.

Over 25% of galaxies have more metal-rich outskirts than centers.

Abstract

MASSIV (Massiv Assembly Survey with SINFONI in VVDS) is an ESO large program which consists of 84 star-forming galaxies, spanning in a wide range of stellar masses, observed with the IFU SINFONI on the VLT, in the redshift range 1 < z < 2. To be representative of the normal galaxy population, the sample has been selected from a well-defined, complete and representative parent sample. The kinematics of individual galaxies reveals that 58% of the galaxies are slow rotators, which means that a high fraction of these galaxies should probably be formed through major merger processes which might have produced gaseous thick or spheroidal structures supported by velocity dispersion rather than by rotation. Computations on the major merger rate from close pairs indicate that a typical star-forming galaxy underwent ~0.4 major mergers since ~9.5 Gyr, showing that merging is a major process driving mass assembly into the red sequence galaxies. These objects are also intriguing due to the fact that more than one galaxy over four is more metal-rich in its outskirts than in its center.