Early and Rapid Merging as a Formation Mechanism of Massive Galaxies: Empirical Constraints

By Christopher J. Conselice. 2005

157 citations recorded by the source corpus.

We present the results of a series of empirical computations regarding the role of major mergers in forming the stellar masses of modern galaxies based on measured galaxy merger and star formation histories from z ~ 0.5 to 3. We reconstruct the merger history of normal field galaxies from z ~ 3 to z ~ 0 as a function of initial mass using published pair fractions and merger fractions from structural analyses. We calibrate the observed merger timescale and mass ratios for galaxy mergers using self-consistent N-body models of mergers with mass ratios from 1 : 1 to 1 : 5 at various orbital properties and viewing angles. We use these simulations to determine the timescales and mass ratios that produce structures that would be identified as major mergers. Based on these calculations, we argue that a typical massive galaxy at z ~ 3 with M* > 1010 M☉ undergoes 4.4 major mergers at z > 1. We find that by z ~ 1.5 the stellar mass of an average massive galaxy is relatively established, a scenario qualitatively favored in a Λ-dominated universe. We argue that the final masses of these systems increase by as much as a factor of 100, allowing Lyman break galaxies, which tend to have low stellar masses, to become the most massive galaxies in today's universe with M > M*. Induced star formation, however, only accounts for 10%-30% of the stellar mass formed in these galaxies at z < 3. A comparison to semianalytic models of galaxy formation shows that cold dark matter (CDM) models consistently underpredict the merger fraction, and rate of merging, of massive galaxies at high redshift. This suggests that massive galaxy formation occurs through more merging than predicted in CDM models, rather than a rapid early collapse.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/faeeec503e9760c22d32da0329686817dc43db3c

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Instrumentation

Citations in the corpus

The Redshift Evolution of Wet, Dry, and Mixed Galaxy Mergers from Close Galaxy Pairs in the DEEP2 Galaxy Redshift Survey (2008, methodology): “…1995; Neuschaefer et al. 1997; Patton et al. 1997; Carlberg et al. 2000; Le Fèvre et al. 2000; Patton et al. 2002; Conselice et al. 2003; Bundy et al. 2004; Lin et al. 2004; Cassata et al. 2005; Conselice 2006; Bell et al. 2006b; Lotz et al. 2008; Kampczyk et al. 2007; Kartaltepe et al. 2007).”
CANDELS: THE COSMIC ASSEMBLY NEAR-INFRARED DEEP EXTRAGALACTIC LEGACY SURVEY (2011, unknown): “Detailed numerical simulations of merging galaxies are able to predict the visibility of mergers using different methods (e.g., Lotz et al. 2008; Conselice 2006).”
The structures of distant galaxies – I. Galaxy structures and the merger rate to z∼ 3 in the Hubble Ultra-Deep Field (2007, methodology): “As explained in detail in Conselice (2006), there are majormergers with AB 0.35, and thus we are not complete in finding mergers by using this definition.”
Galaxy merger morphologies and time-scales from simulations of equal-mass gas-rich disc mergers (2008, background): “Such low bulge-to-disc ratio galaxies are more likely to experience strong starbursts (Mihos & Hernquist 1996, Cox et al. 2008) and stronger morphological disturbances (Conselice 2006).”
The effect of mass ratio on the morphology and time-scales of disc galaxy mergers: Effect of mass ratio on merger morphology (2009, background): “Most previous theoretical studies of minor mergers have focused on the structures of the merger remnants (e.g. Hopkins et al. 2009; Naab et al. 2009; Robertson et al 2006; Bournaud, Jog, & Combes et al. 2004; Johnston et al. 1996) or spanned a very limited range of parameter space (Conselice 2006).”
The Evolution of Galaxy Structure Over Cosmic Time (2014, methodology): “This quantitatively expands into other physical parameters as well (e.g., Roberts 1963; Roberts & Haynes 1994; Conselice 2006a; Allen et al. 2006).”
THE EVOLUTION OF GALAXY NUMBER DENSITY AT z < 8 AND ITS IMPLICATIONS (2016, background): “This compares well with the directly derived merger rates from Conselice (2006) who find that the merger rate for M∗ > 10 8 M⊙ galaxies is R ∼ 0.03 mergers Gyr −1 Mpc−3, while for M∗ > 10 9 M⊙ galaxies the rate is R ∼ 0.01 mergers Gyr−1 Mpc−3.”
Galaxy Zoo: the fraction of merging galaxies in the SDSS and their morphologies (2009, background): “These issues include the formation of galaxies (White & Rees 1978; Lacey & Cole 1993; Conselice 2006a; De Lucia et al. 2006), environmental effects on morphology (Capak et al. 2007; Park et al. 2007; Ball et al. 2008; Van der Wel 2008) and the distribution of the dark matter that drives the merger…”
THE DEPENDENCE OF QUENCHING UPON THE INNER STRUCTURE OF GALAXIES AT 0.5 ⩽ z < 0.8 IN THE DEEP2/AEGIS SURVEY (2012, result): “Studies that have measured the galaxy merger rate often present different results (e.g., Bell et al. 2006; Conselice 2006; Lin et al. 2008; Lotz et al. 2008b; Bundy et al. 2009; Xu et al. 2011; Bluck et al. 2011).”
HISTORY OF GALAXY INTERACTIONS AND THEIR IMPACT ON STAR FORMATION OVER THE LAST 7 Gyr FROM GEMS (2009, methodology): “Comparison with simulations suggest that the CAS criterion (A > 0.35 and A > S; Conselice 2003) capture major mergers about 1/3 of the time, while the eye is sensitive to major merger features over twice as long (e.g., Conselice 2006; § 3.4).”
The merger rate of galaxies in the Illustris simulation: a comparison with observations and semi-empirical models (2015, methodology): “0.2), which are converted into merger rates by using the mass-dependent merger time-scales from Conselice (2006).”
Very Small Scale Clustering and Merger Rate of Luminous Red Galaxies (2005, result): “Nevertheless our result is, in principle, consistent with the extrapolation of the best fits to samples at higher redshifts or fainter samples (Conselice 2006).”
The fundamental properties of galaxies and a new galaxy classification system (2006, background): “The merger idea for the origin of ellipticals is currently popular, with both indirect and direct supporting evidence (e.g., Schweizer & Seiter 1988; Conselice 2006).”
The structures of distant galaxies – III. The merger history of over 20 000 massive galaxies at z < 1.2 (2008, methodology): “As shown in Conselice (2006) there are phases of a merger which will not be picked up by the CAS technique.”