# SDSS IV MaNGA: Full spectroscopic bulge-disc decomposition of MaNGA early-type galaxies

## TL;DR

This study applies spectroscopic decomposition to MaNGA early-type galaxies to analyze their bulge and disc stellar populations and kinematics, revealing distinct properties and evolutionary insights.

## Contribution

It introduces a method for spectroscopic decomposition of galaxies into bulge and disc components and validates it through dynamical modeling, highlighting their individual properties.

## Key findings

- Bulges are more metal-rich than discs.
- Discs show a tail of younger, metal-poor populations.
- Bulges and discs follow distinct kinematic relations.

## Abstract

By applying spectroscopic decomposition methods to a sample of MaNGA early-type galaxies, we separate out spatially and kinematically distinct stellar populations, allowing us to explore the similarities and differences between galaxy bulges and discs, and how they affect the global properties of the galaxy. We find that the components have interesting variations in their stellar populations, and display different kinematics. Bulges tend to be consistently more metal rich than their disc counterparts, and while the ages of both components are comparable, there is an interesting tail of younger, more metal poor discs. Bulges and discs follow their own distinct kinematic relationships, both on the plane of the stellar spin parameter, lambda_R, and ellipticity, and in the relation between stellar mass and specific angular momentum, j, with the location of the galaxy as a whole on these planes being determined by how much bulge and disc it contains. As a check of the physical significance of the kinematic decompositions, we also dynamically model the individual galaxy components within the global potential of the galaxy. The resulting components exhibit kinematic parameters consistent with those from the spectroscopic decomposition, and though the dynamical modelling suffers from some degeneracies, the bulges and discs display systematically different intrinsic dynamical properties. This work demonstrates the value in considering the individual components of galaxies rather than treating them as a single entity, which neglects information that may be crucial in understanding where, when and how galaxies evolve into the systems we see today.