Stellar kinematics, morphology and local environment of galaxies with integral field spectroscopy
Keywords: Extragalactic Astrophysics
Galaxy Environment
Galaxy Clusters
Kinematics
Galaxies
Galaxy Evolution
Integral Field Spectroscopy

In this thesis, I study the stellar angular momentum within one effective radius, λRe of a few thousand galaxies and consider how this property relates to other galaxy properties such as stellar mass, optical morphology and environment. I make use of data from the Sloan Digital Sky Survey's (SDSS) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey which is a large integral field spectroscopic survey. I classify early-type galaxies (ETGs) as slow rotators if λRe < 0.08 + 0.25ϵ and ϵ < 0.4, where ϵ is the galaxy flattening, and as fast rotators if otherwise. I present the (λRe,ϵ) diagram for about 2300 galaxies and provide the first conclusive evidence that fast and slow rotator ETGs form a bimodality in angular momentum suggesting that they are kinematically distinct populations. I show that they also form a bimodality in other properties such as stellar mass and kinematic morphology, which I attribute as being a direct consequence of the existence of two ETG formation channels, a gas rich (wet) accretion channel which produces FRs and a gas poor (dry) merger channel which produces SRs.
I investigate the hypothesis that massive SRs have built up their stellar mass and decreased their angular momentum as a result of experiencing multiple dry minor mergers by studying their environment. By running a new group-finder algorithm on a large galaxy catalogue containing spectroscopic and photometric observations, I find the neighbouring galaxies for about 4600 MaNGA galaxies. For all neighbours that satisfy the criteria for massive SRs (M ≥ 2 × 1011 M⊙ and ϵ<0.4), I assign an angular momentum classification based on optical morphology to achieve a complete, volume-limited sample of about 14,000 galaxies.
Using this sample, I reproduce the kinematic morphology-density (kT-Σ) relation for massive SRs, finding that they are about six times more abundant in the dense centres of clusters compared to the field. I show that when the kT-Σ relation is derived from multiple clusters, the individual cluster trends are washed out. I account for this smoothing effect by defining a relative density estimator, Σrel, that measures number density relative to the cluster/group peak density. I show that the kT-Σrel relation is a better predictor of the abundance of massive SRs than the kT-Σ relation. I find that these environmental trends persist at fixed stellar mass, although they are subtle because stellar mass is the main driver for slow rotation. I also present schematics for 10 large galaxy clusters highlighting the location of the massive SRs. In all cases, the density peaks contain at least one massive SR, while FRs are distributed evenly throughout the cluster. I conclude that these results provide definitive proof that the progenitors of modern-day massive SRs formed rapidly at high redshift in dense environments before accreting a significant fraction of their stellar mass via dry minor mergers. Finally, I suggest potential avenues for follow-up.