A Simple Model for the Size Evolution of Elliptical Galaxies

By S. Khochfar, J. Silk. 2006

219 citations recorded by the source corpus.

We use semianalytical modeling of galaxy formation to predict the redshift-size evolution of elliptical galaxies. Using a simple model in which relative sizes of elliptical galaxies of a given mass correlate with the fraction of stars formed in a starburst during a major merger event, we are able to reproduce the observed redshift-size evolution. The size evolution is a result of the amount of cold gas available during the major merger. Mergers at high redshifts are gas-rich and produce ellipticals with smaller sizes. In particular, we find a power-law relation between the sizes at different redshifts, with the power-law index giving a measure of the relative amount of dissipation during the mergers that lead to the formation of an elliptical. The size evolution is found to be stronger for more massive galaxies as they involve more gas at high redshifts when they form, compared to less massive ellipticals. Local ellipticals more massive than 5 × 1011 M☉ will be approximately 4 times larger than their counterparts at z = 2. Our results indicate that the scatter in the size of similar massive present-day elliptical galaxies is a result of their formation epoch, with smaller ellipticals being formed earlier.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/443830a0aeeba311d732b3d3e72ad53d3c17fffe

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Citations in the corpus

The Evolution of Galaxy Structure Over Cosmic Time (2014, background): “…as a function of the ratio with the average size of galaxies at the same stellar mass measurements with M∗ > 1011 M⊙ at z = 0 from Shen et al. (2003). without significantly increasing mass (e.g., Khochfar & Silk 2006; Naab et al. 2009; Bluck et al. 2012; Oser et al. 2012; Shankar et al. 2013).”
The DEEP3 Galaxy Redshift Survey: the impact of environment on the size evolution of massive early-type galaxies at intermediate redshift (2011, background): “…gas-poor, collisionless (or ‘dry’) minor mergers are often invoked as a means for puffing up the stellar component of these massive systems (e.g. Khochfar & Silk 2006; Naab, Khochfar & Burkert 2006; Bournaud, Jog & Combes 2007; Boylan-Kolchin & Ma 2007; Naab et al. 2007; Cenarro & Trujillo…”
THE COSMOLOGICAL SIZE AND VELOCITY DISPERSION EVOLUTION OF MASSIVE EARLY-TYPE GALAXIES (2011, background): “…al. (2010) we investigated this two phase scenario in more detail with a larger sample of resimulations and found a connection between galaxy mass, size, and the assembly history (see also Khochfar & Silk 2006a; De Lucia & Blaizot 2007; Guo & White 2008; Hopkins et al. 2009b; Feldmann et al. 2010).”
Compact high-redshift galaxies are the cores of the most massive present-day spheroids (2009, background): “Given the gas-richness of high-redshift galaxies, some size evolution is naturally predicted in models, with high-redshift systems being more dominated by the dense, dissipational remnant (Khochfar & Silk 2006; Hopkins et al. 2009c).”
CAN MINOR MERGING ACCOUNT FOR THE SIZE GROWTH OF QUIESCENT GALAXIES? NEW RESULTS FROM THE CANDELS SURVEY (2011, background): “They are therefore expected theoretically to experience less dissipation in their formation, possibly leading to less compact remnants (Robertson et al. 2006; Khochfar & Silk 2006; Hopkins et al. 2010b; Shankar et al. 2011).”
How do minor mergers promote inside-out growth of ellipticals, transforming the size, density profile and dark matter fraction? (2012, background): “…start forming their stars at a redshift of z ∼ 6 in a dissipative environment and can rapidly become very massive (∼ 1011M⊙) by z = 2 (Kereš et al. 2005; Khochfar & Silk 2006; De Lucia et al. 2006; Kriek et al. 2006; Naab et al. 2007, 2009; Joung et al. 2009; Dekel et al. 2009; Kereš et al.…”
Structure and Star Formation in Galaxies out to z = 3: Evidence for Surface Density Dependent Evolution and Upsizing (2008, background): “Two processes are likely responsible for their small sizes: the halos were smaller and denser, and additionally their gas fractions were higher, and dissipation during merging was stronger, as suggested by Khochfar & Silk (2006).”
MINOR MERGERS AND THE SIZE EVOLUTION OF ELLIPTICAL GALAXIES (2009, background): “…and stellar accretion events are the prime candidates for the strong mass and size evolution of stellar spheroids at z < 2 (Naab et al. 2006; Khochfar & Silk 2006; Bell et al. 2006a,b; Ruszkowski & Springel 2009; Hopkins et al. 2009; van der Wel et al. 2009) as the additional presence of a…”
Formation of Early-Type Galaxies from Cosmological Initial Conditions (2005, background): “From those two examples, we find that 15%Y35% of the final stellar mass was assembled by accretion of stars that formed outside the galaxy (see Khochfar & Silk 2006b).”
Size Evolution of the Most Massive Galaxies at 1.7 < z < 3 from GOODS NICMOS Survey Imaging (2008, background): “Models suggest that at very early times galaxies contain large amounts of cold gas, resulting in efficient starbursts (e.g., Khochfar & Silk 2006).”
Discriminating Between the Physical Processes that Drive Spheroid Size Evolution (2009, background): “As is discussed in detail in Khochfar & Silk (2006) and Hopkins et al. (2009d), this occurs naturally in merger models: at the same mass, higher redshift discs have larger observed gas fractions.”
THE EVOLVING RELATIONS BETWEEN SIZE, MASS, SURFACE DENSITY, AND STAR FORMATION IN 3 × 104 GALAXIES SINCE z = 2 (2009, background): “However, theoretical models have yet to converge on a definitive explanation – some proposed models predict galaxy sizes dramatically different from those observed (Joung et al. 2009), while others match observed sizes atz= 2 andz= 0 (Khochfar & Silk 2006) but not atz∼ 1 (van der Wel et al. 2008).”
The Dramatic Size Evolution of Elliptical Galaxies and the Quasar Feedback (2008, background): “1, we predict significant evolution for galaxies withM⋆ ≥ 2×1010 M⊙, well below the threshold of M⋆ ≥ 5×1011M⊙ implied by the semi-analytic model of Khochfar & Silk (2006).”
GALAXY STRUCTURE AND MODE OF STAR FORMATION IN THE SFR–MASS PLANE FROM z ∼ 2.5 TO z ∼ 0.1 (2011, result): “…van der Wel et al. 2008; van Dokkum et al. 2008, but see Mancini et al. 2010 for a contrasting view), in agreement with expectations from binary merger scenarios in which the gas content of the progenitors increases with redshift (Khochfar & Silk 2006; Hopkins et al. 2009; Wuyts et al. 2010).”
MERGERS AND BULGE FORMATION IN ΛCDM: WHICH MERGERS MATTER? (2009, background): “Similar conclusions are reached even by mod- els with significantly different bulge formation prescriptions (Khochfar & Silk 2006).”
Hubble Space Telescope and Spitzer Imaging of Red and Blue Galaxies at z ~ 2.5: A Correlation between Size and Star Formation Activity from Compact Quiescent Galaxies to Extended Star-forming Galaxies (2007, background): “…are more likely to be gas-rich than galaxies that merge later, since they have had less time to exhaust their gas reservoirs, and as a consequence,massive ellipticals (M > 5 ; 1011 M ) are predicted to be 4 times smaller at z ¼ 2 than galaxies of similar mass at z ¼ 0 (Khochfar & Silk 2006).”
The Horizon-AGN Simulation: Morphological Diversity of Galaxies ,Promoted by AGN Feedback (2016, background): “…the mergers to be efficient enough to turn the remnant into an elliptical galaxy and increase its size, it needs to be dissipation-less, i.e. contain a low amount of cold star-forming gas, or, otherwise will decrease the galaxy size (Khochfar & Silk 2006; Wellons et al. 2015; Welker et al. 2015a).”
MERGERS IN ΛCDM: UNCERTAINTIES IN THEORETICAL PREDICTIONS AND INTERPRETATIONS OF THE MERGER RATE (2010, methodology): “Galaxy structural properties are followed using energetic arguments and scalings motivated by simulations (Khochfar & Silk 2006).”