Abstract

Poster - Splinter General   (MW-1801 / virtual plenum)

Star Formation Quenching in Post-Merger Galaxies

Jatin Chopra, Frank Bigiel, Mallory Thorp
Argelander-Institut für Astronomie (University of Bonn)

Galaxy-Galaxy mergers are well-known phenomena that alter the morphology and star formation of the constituent galaxies. Many simulation-based studies have shown that the cessation of star formation (star formation quenching) is caused by AGN triggered by mergers. However, many other studies have proposed different quenching mechanisms, such as morphological quenching, stellar feedback, and ram-pressure stripping. Yet observations have failed to determine which of these mechanisms dominates galaxy evolution. We aim to investigate the questions: (1) Are post-mergers distributed differently across quenching stages? (2) Does star formation quenching in post-mergers differ significantly from non-interacting galaxies? Recent spatially resolved studies have revealed that merger-triggered starbursts exhibit unique radial star formation profiles compared to their secular counterparts. So what remains unanswered is whether the merger-induced star formation changes as galaxies transition across different evolutionary stages. We use the integral field spectroscopy data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) Survey (10,070 Galaxies). Using IFU observations of galaxies with a range of star-formation properties, Kalinova et al. 2021 found distinct kpc-scale signatures in a galaxy’s ionised gas marking an evolution from star-forming to quenched, which they have labelled with unique "quenching stages”. We visually classified the galaxies into their respective quenching stages, following Kalinova. The sample has 388 Post Mergers (PMs) and 7051 Non-Interacting Galaxies (Controls). Each post-merger is matched to at least five control galaxies with similar properties at the same quenching stage. Radial profiles of ∆ΣSFR (Offset from the resolved star-formation main sequence, calculated using Hα emission) are created by comparing star-forming spaxels of PMs and Controls that occupy similar regions within a galaxy. The distribution of PMs and Controls across the quenching stages is broadly similar. This suggests that while mergers do not dramatically redistribute galaxies across the quenching stages. Within each quenching stage, the radial profiles do not show any significant differences between the PMs and Controls. This implies that though the magnitude of star formation enhancement is tied to kpc-scale variations in the ISM related to mergers, star formation suppression is a more universal process with no merger influence on kpc-scales. We are now working with alternative and more continuous measurements of star formation (beyond Hα emission) to create a more complete picture of the resolved quenching scheme of the galaxies and further constrain the significance of mergers in galaxy evolution.