The effect of mass and morphology on the mass assembly of galaxies

TL;DR

This study investigates how galaxy mass and morphology influence their growth history, revealing early morphological distinctions and the evolution of star formation rates across different galaxy types.

Contribution

It provides new insights into the timing of morphological development and star formation decline, using spectral fitting of MaNGA data to connect galaxy properties over cosmic time.

Findings

Galaxies had similar mass doubling times in the past.

Current morphology correlates with star formation history from early times.

Massive galaxies dropped off the main sequence earlier.

Abstract

The pace at which galaxies grew into their current stellar masses and how this growth is regulated is still not fully understood, nor is the role that morphology plays in this process. We applied full spectral fitting techniques with pyPipe3D to the MaNGA sample to obtain its star formation and stellar mass histories and used these to investigate the mass assembly of galaxies by measuring how their specific star formation correlates to their stellar mass at different look-back times. We find that the correlation between these two parameters was shallower in the past. Galaxies used to have similar mass doubling times and the current negative correlation between the specific star formation and M* is primarily due to more massive galaxies 'dropping' off the main sequence earlier than less massive ones. Additionally, selecting the galaxies into bins based on their present-day morphology shows a segregation in specific star formation rate (sSFR) that is maintained even at high look-back times, showing that the factors that determine which morphology a galaxy ends up in are in place at very early times. Similarly, selecting them based on their current star formation status shows that, on average, currently retired galaxies used to have slightly a higher sSFR before the drop-off, whereas galaxies that have continued to form stars until today had a lower sSFR initially. We compare our results to a set of cosmic surveys, finding partial agreement in our results with several of them, though with significant offsets in redshift. Finally, we discuss how our results fit with certain theoretical models on galaxy evolution as well as cosmological simulations.