Here you may find information on the fellows of the PhD::SPACE Program that have selected a topic on the thematic line on The assembly history of galaxies resolved in space and time.
2015/B010 Fellow: Sara Pérez Sánchez (ongoing)
PhD Topic (2015/311): Exploring the Universe with the largest emission-line surveys: from the first galaxies to the peak and decline of the star formation history of the Universe
What are the physical drivers of galaxy formation and evolution? How much (and why) did galaxies like our own change across cosmic time? When, how and through which physical mechanisms are galaxies “quenched”? Why were galaxies in the distant Universe so efficient at producing new stars? What were the roles of “nature” (stellar mass) and “nurture” (environment) in the past, how did they change with cosmic time and is there a connection between those and the declining star formation activity? Is our current view of how galaxies form and evolve correct? When and how were the first galaxies and stars formed?
In order to make progress, the student will explore and conduct unique, large >10 deg^2 narrow- band surveys that have yielded 1000s of galaxies (similar to the Milky Way), selected in the same way across the last ~13 billion years (with WIRCam/CFHT and WFCAM/UKIRT) with Hα and Lyα, including a unique double blind survey which targets both lines (Hα and Lyα) simultaneously at z=2.23 over large areas. Currently almost all high redshift studies rely on the Lyα emission line to survey, study and understand the distant Universe (z>2-3), as it is often the only feature available to spectroscopically confirm/study such galaxies. However, the escape fraction of Lyα (fescape) is highly uncertain at z>2, and much is unknown about what Lyα actually traces. How much are we missing by relying on it? How biased is our current view of the very high redshift, almost completely based on Lyα? Can we finally calibrate and understand Lyα and Lyα emitters.
The samples will be ideal to study the metallicities, dust extinction, clustering, radio-loud fractions and evolution of “typical” star-forming galaxies all the way to z~7-9 (including the possibility to use J-PAS data), and to study the role of nature and nurture at z~1-2 (with PI VIMOS observations, but also by exploring the 128 night LEGA-C VIMOS observations on the VLT). By using observations that have already been conducted (e.g. MOSFIRE and DEIMOS/Keck, FMOS/Subaru, VIMOS/VLT and new data from radio surveys, e.g. EMU), the student will be able to gain unprecedentedly detailed information on a large sample of galaxies which will then be explored with MOONS (part of the data were already used to develop the MOONS science case). The results from the project will provide some of the strongest tests/constraints to the most sophisticated models of galaxy formation and evolution (e.g. EAGLE, Illustris), but the student will also be encouraged, towards the end of the PhD, to model and interpret the observations. The results will also be fully compared and contrasted to the best surveys at z~0 and to other very complimentary surveys. Several detailed follow-up studies are foreseen, particularly with X-SHOOTER, MOSFIRE and other instruments.
Starting date: 2015/10/01
2014/B004 Fellow: Íris P. Breda (ongoing)
PhD Topic (2014/307): The nature and formation history of pseudo-bulges in galaxies
The featureless appearance of bulges in Hubble-type galaxies has for decades sustained the view that these high-surface brightness spheroidal components are largely “simple” in terms of their assembly history, formed on a short timescale early on, and having experienced little evolution over the past several Gyr. However, our early understanding of bulges as essentially scaled ellipticals has undergone a substantial revision over the last years. It is now recognized that central luminosity components that closely resemble classical bulges can also form over much longer timescales through disk instabilities and ensuing star forming activity at the centers of galaxies. The nature and formation history of these “pseudo-bulges” is enigmatic and of considerable relevance to our understanding of the structural and spectrophotometric evolution of galaxies in general.
This PhD project aims at a spatially resolved investigation of the star formation- and chemical enrichment history of pseudo-bulges. A unique aspect of its methodology is the combined application of surface photometry and spectral population synthesis to a large sample of galaxies from the Calar Alto Legacy Integral Field spectroscopy Area survey (http://califa.caha.es) with the goal of conclusively addressing the star formation history (SFH) and the chemical abundance patterns of pseudo-bulges. One of the central questions to be investigated is whether pseudo-bulges form in a quasi-continuous manner over several Gyrs of galactic evolution and their SFH can be parametrized through a simple functional form involving integral or structural properties of their host galaxy (e.g., total stellar mass; central surface brightness and exponential scale length of the underlying disk). Additionally, this project will include a comparative study of pseudo-bulges and classical bulges with the goal of the identification of new empirical discriminators between them and yield robust observational constraints to theoretical models of pseudo-bulge formation and evolution.
Starting date: 2014/11/01
2014/B003 Fellow: Ana S. P. Afonso (ongoing)
PhD Topic (2014/302): The KMOS/VLT revolution: rotation curves, metallicities, dust extinction and galaxy formation and evolution with hundreds of galaxies at 0.8 < z < 2.23 vs z~0
What are the physical drivers of galaxy formation and evolution? How much (and why) did galaxies like our own change across cosmic time (e.g. metallicities, dynamics)? When, how and through which physical mechanisms are galaxies “quenched”? In order to make progress, the student will explore our unique, large ~10 deg2 narrow-band surveys that have yielded 1000s of galaxies (similar to the Milky Way), selected in the same way across the last 11 billion years (with WIRCam/CFHT and WFCAM/UKIRT). These are ideal samples to study the metallicities, dust extinction and rotation curves of “typical” star-forming galaxies and how these have evolved from the peak of the star-formation history (z~2.5) till today. By using KMOS (observations already started and thus all data is guaranteed both as PI and as part of GTO collaboration), the student will be able to gain unprecedentedly detailed information on a large sample of galaxies. KMOS, with its 24 Integral Field Units (IFUs) allows to target up to 24 galaxies at the same time, obtaining an image and a near-infrared spectrum for each pixel. This is a unique opportunity to map the distribution and intensity of star formation, dynamics and metallicity on ~4 kpc scales and address (and to fully interpret them): (i) What is the fraction of primitive disks, spheroids and mergers? (ii) Is the distribution of star formation at high-z more centrally concentrated than comparably luminous/turbulent galaxies at z~0? and iii) Are chemical abundance gradients weaker or stronger than local spiral galaxies and do those change with time? Answers to these questions using our well selected samples will provide some of the strongest tests/constraints to the most sophisticated models of galaxy formation and evolution. By selection, all of the targets have known Hα fluxes and all are sufficiently bright so their resolved properties can be recovered and the survey efficiency will be >95% (GTO observations already yielded samples of ~400 galaxies). The results will be fully compared and contrasted to the best local IFU surveys (including artificially redshifting a variety of local galaxies and fully addressing biases and systematics), and will be interpreted using our unique 3D modelling capabilities developed at CAUP. Another unique aspect of this project is that there are significant over-densities in the very large samples of Hα emitters, and thus, with KMOS, the student will be able to confirm and characterise the high redshift structures, derive accurate metallicities, measure the mass-metallicity relation, obtain Balmer decrement extinctions and identify AGN for a sample of hundreds of Hα-selected galaxies and investigate if the environment plays a role in setting these galaxy properties.
Notes: Mixed fellowship (up to one year in Durham).
Starting date: 2014/11/01