Kaya Tengiz

I am a PhD candidate at UNSW with focus on galaxy formation and evolution, and cosmological zoom-in simulations. I have completed a Master’s degree in Astrophysics with a Year in China studying counter rotating stars in galactic disks at the University of Liverpool and Liverpool John Moore's University.

Project: Revisiting Disk Galaxy Evolution Using Cutting-Edge Zoom-in Simulations

Supervised by: Dr. Jesse van de Sande 

Project description: The complexity of central components is often simplified into two distinct types: classical bulges, and pseudobulges (Kormendy & Kennicutt, 2004). Classical bulges are typically defined as dispersion dominated, spherical systems thought to form via mergers, whereas pseudobulges are regarded to be dense central components built through secular processes within the disk. While this framework is conceptually appealing, modern observations and simulations have shown that dichotomous bulge classifications are incomplete (e.g. Breda & Papaderos, 2018), which introduces several challenges:

• Contradictions in the classification and frequency of each bulge type in the local universe (e.g. Costantin et al. 2018).

• The framework for classical bulge formation relies on simulations without the detailed sub-grid physics that is available now (e.g. Toomre, 1977b; Bournard et al., 2005; Naab & Burkert, 2003b).

• Modern literature increasingly links the structure and formation of thick disks and central mass components (CMCs) (e.g. Comerón et al., 2018, 2019; Yu et al., 2022; Park et al., 2021), often arguing for reduced reliance on merger-driven formation models (e.g. Hopkins et al. 2009).

• Light contributed by central components are dependent on the number of components in a photometric decomposition (i.e. 1 component versus 2 or more) (e.g. Salo et al., 2015; Breda et al. 2020). Observations of disk galaxies often rely on two component decompositions: bulge + disk when face-on, and thin + thick disk when edge-on. However, light from both the bulge and thick disk may be codependent in different projections.

Cosmological zoom-in simulations now have high-enough resolution to trace the subtle impact of mergers using state of the art sub-grid physics (e.g. Hopkins et al., 2009; Fragkoudi et al., 2019; Shuntov et al., 2022). My work intends to use these simulations to revisit the formation and structure of central components from a blank slate using photometry and kinematics.