UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Understanding the evolution of galaxies using a novel definition of the Green Valley

Angthopo, James; (2021) Understanding the evolution of galaxies using a novel definition of the Green Valley. Doctoral thesis (Ph.D), UCL (University College London). Green open access

[thumbnail of UCL_Thesis_Final.pdf]
Preview
Text
UCL_Thesis_Final.pdf - Accepted Version

Download (17MB) | Preview

Abstract

Green Valley (GV) galaxies are essential to the understanding of galaxy formation and evolution, which, in turn, is necessary to understand our Universe. In this thesis we explore a novel way to define the GV, using the 4000Å break strength, which is more resilient to dust and less model dependent, thus carrying less inherent systematics compared with traditional methods. This method finds a cleaner stratification between each GV region; divided into lower (lGV), middle (mGV) and upper (uGV) green valley. We find comparable results between novel (4000Å break) and traditional (dust-corrected colour) methods of selecting GV galaxies - i.e., similar fractions of AGN galaxies and matching transition timescales. However, a more in-depth analysis finds nuanced differences, such as more homogeneous stellar population properties between different types of galaxies in the novel definition. Furthermore, we find results suggesting a more rapid transition from Blue Cloud (BC) to GV than from GV to Red Sequence (RS). This thesis also tests how well hydrodynamical simulations, EAGLE and IllustrisTNG (TNG100), are able to reproduce the observed trend on the 4000Å break vs stellar mass plane. We find both simulations match the location of the BC, however produce the RS and GV at a higher 4000Å break value than observations. Comparison of GV galaxies between observation and simulations find both simulations to overproduce quiescent fractions. As this is mostly seen for M⋆ ≳ 10^{10.5} M⊙, it is assumed mostly to be due to the subgrid physics of AGN feedback. Finally, we also compared “Twin” galaxies, having similar overall properties such as morphology, colour, stellar mass, etc, but one hosts an AGN and the other doesn’t. From this, we find AGN galaxies to be generally more evolved and metal rich than their non-AGN “twin”.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Understanding the evolution of galaxies using a novel definition of the Green Valley
Event: UCL (University College London)
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2021. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10140811
Downloads since deposit
116Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item