The Evolution of Galaxy Structure Over Cosmic Time

By Christopher J. Conselice. 2014

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I present a comprehensive review of the evolution of galaxy structure in the Universe from the first galaxies currently observable at z ∼ 6 down to galaxies observable in the local Universe. Observed changes in galaxy structures reveal formation processes that only galaxy structural analyses can provide. This pedagogical review provides a detailed discussion of the major methods used to study galaxies morphologically and structurally, including the well-established visual method for morphology; S´ ersic fitting to measure galaxy sizes and surface brightness profile shapes; and nonparametric structural methods [such as the concentration (C), asymmetry (A), clumpiness (S) (CAS) method and the Gini/M20 parameters, as well as newer structural indices]. These structural indices measure fundamental properties of galaxies, such as their scale, star-formation rate, and ongoing merger activity. Extensive observational results demonstrate how broad galaxy morphologies and structures change with time up to z ∼ 3, from small, compact and peculiar systems in the distant Universe to the formation of the Hubble sequence, dominated by spirals and ellipticals. Structural methods accurately identify galaxies in mergers and allow measurements of the merger history out to z ∼ 3. I depict properties and evolution of internal structures of galaxies, such as bulges, disks, bars, and at z > 1 large star-forming clumps. I describe the structure and morphologies of host galaxies of active galactic nuclei and starbursts/submillimeter galaxies, along with how morphological galaxy quenching occurs. The role of environment in producing structural changes in galaxies over cosmic time is also discussed. Galaxy sizes can also change with time, with measured sizes up to a factor of 2–5 smaller at high redshift at a given stellar mass. I conclude with a discussion of how the evolving trends, in sizes, structures, and morphologies, reveal the formation mechanisms behind galaxies and provides a new and unique way to test theories of galaxy formation.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/add14145b9dafc9bc4632dc0bfa78fb063e9ccbb

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Citations in the corpus

Galaxy And Mass Assembly (GAMA): mass–size relations of z < 0.1 galaxies subdivided by Sérsic index, colour and morphology (2014, background): “…be the oldest in our sample and hence would have had more time to re-distribute their stellar populations (in part aided by major mergers; see e.g. Conselice 2014) so that we see less stellar population (or colour) gradients and hence their Re and Sérsic index should change less with wavelength.”
Introducing the Illustris Project: the evolution of galaxy populations across cosmic time (2014, background): “7 G A L A X Y M O R P H O L O G I E S Deep observations of high-redshift galaxies reveal that galaxy morphology changes significantly with cosmic time (Conselice 2014).”
The LOFAR Two-metre Sky Survey. I. Survey description and preliminary data release (2016, background): “…density of powerful AGN as well as the peak of the star formation rate and the merger rate of galaxies (Jarvis & Rawlings 2000, Rigby et al. 2015, Madau & Dickinson 2014 and Conselice 2014), and will thus help to provide the necessary data for a full census of radio sources over this cosmic epoch.”
Structure and Kinematics of Early-Type Galaxies from Integral Field Spectroscopy (2016, methodology): “These provided the ability to trace galaxy evolution back in time (see Conselice 2014, for a review).”
FORMING COMPACT MASSIVE GALAXIES (2015, background): “INTRODUCTION Many studies have shown that massive galaxies with low star formation rates were remarkably compact atz& 2 (e.g., Daddi et al. 2005; Trujillo et al. 2006; van Dokkum et al. 2008; Damjanov et al. 2011; Conselice 2014).”
Evidence for an Intermediate-mass Milky Way from Gaia DR2 Halo Globular Cluster Motions (2018, background): “However, the second Gaia data release (Gaia Collaboration et al. 2018a) has greatly expanded our view of the local Universe.”
Galaxy Interactions Trigger Rapid Black Hole Growth: an unprecedented view from the Hyper Suprime-Cam Survey (2017, methodology): “For the precise formulation of these parameters we refer the reader to Section 2.3 of the review by Conselice (2014) and Hoyos et al. (2012).”
First results from the TNG50 simulation: the evolution of stellar and gaseous discs across cosmic time (2019, methodology): “The observational quantification of galaxy stellar morphologies has a century-long history with methods including visual inspection, light profile fits, and non-parametric measures (see e.g. Conselice 2014, and references therein for a review).”
THE EVOLUTION OF GALAXY NUMBER DENSITY AT z < 8 AND ITS IMPLICATIONS (2016, background): “As discussed in e.g., Conselice (2014) this is also a major way in which galaxy formation occurs at these epochs.”
The ALPINE-ALMA [CII] survey (2020, background): “Galaxy mergers, major and minor, are observed at all epochs (e.g., Conselice 2014), with a major merger rate increasing from the local universe to z ∼ 2 (e.g., Lotz et al. 2011; LópezSanjuan et al. 2013; Mantha et al. 2018), and possibly flattening to z ∼ 4−5 (e.g., Tasca et al. 2014; Ventou et al.…”
Physical Models of Galaxy Formation in a Cosmological Framework (2014, methodology): “There are many different methods for quantifying and classifying galaxy morphology, and this subject is reviewed in Conselice (2014); see also the more nearby-Universe focussed discussion in Buta (2013).”