A calibration of the relation between the abundance of close galaxy pairs and the rate of galaxy mergers

By Manfred G. Kitzbichler, Simon D. M. White. 2008

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Estimates of galaxy merger rates based on counts of close pairs typically assume that most of the observed systems will merge within a few hundred Myr (for projected pair separations 6 25h −1 kpc). Here we investigate these assumptions using virtual galaxy catalogues derived from the Millennium Simulation, a very large N-body simulation of structure formation in the concordanceCDM cosmology. These catalogues have been shown to be at least roughly consistent with a wide range of properties of the observed galaxy population at both low and high redshift. Here we show that they also predict close pair abundances at low redshift which agree with those observed. They thus embed a realistic and realistically evolving galaxy population within the standard structure formation paradigm, and so are well-suited to calibrate the relation between close galaxy pairs and mergers. We show that observational methods, when applied to our mock galaxy surveys, do indeed identify pairs which are physically close and due to merge. The sample-averaged merging time depends only weakly on the stellar mass and redshift of the pair. At z 6 2 this time-scale is TTor25M −0.3 ∗ , where r25 is the maximum projected separation of the pair sample in units of 25h −1 kpc, M∗ is the typical stellar mass of the pairs in units of 3 × 10 10 h −1 M⊙, and the coefficient T0 is 1.1 Gyr for samples selected to have line-of-sight velocity difference smaller than 300 km/s and 1.6 Gyr for samples where this velocity difference is effectively unconstrained. These timescales increase slightly with redshift and are longer t han assumed in most observational studies, implying that merger rates have typically been overestimated.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/cce9359fa2a07b6be10605548c907e1738f19b68

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In Astronomy and Astrophysics

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Citations in the corpus

• MERGERS AND BULGE FORMATION IN ΛCDM: WHICH MERGERS MATTER? (2009, methodology): “…also attempt to calibrate 18 The merger timescale from simulations at this radius is shorter than the time obtained assuming dynamical friction and circularorbits in e.g. an isothermal sphere, as has commonly been done (this is assumed in e.g. both Patton et al. 2002; Kitzbichler & White 2008).”
• Integral field spectroscopy with SINFONI of VVDS galaxies I. Galaxy dynamics and mass assembly at 1.2 < z < 1.6 (2009, background): “The merging timescale would be around 0.4 Gyr (from Kitzbichler & White 2008).”
• The VIMOS VLT Deep Survey - Evolution of the major merger rate since z ~ 1 from spectroscopically confirmed galaxy pairs (2008, unknown): “We are thankful to Simon White for forwarding us a preprint of the Kitzbichler and White (2008) work ahead of publication.”
• The effect of mass ratio on the morphology and time-scales of disc galaxy mergers: Effect of mass ratio on merger morphology (2009, methodology): “We compare our results to the merger time-scales of Boylan-Kolchin, Ma & Quataert (2008) for GADGET-2 mergers of dark matter haloes, and of Kitzbichler & White (2008) derived from the Millenium Simulation semi-analytic model.”
• THE ROCKSTAR PHASE-SPACE TEMPORAL HALO FINDER AND THE VELOCITY OFFSETS OF CLUSTER CORES (2011, background): “…in simulations; however, as recently as for the Millennium Simulation, simulators have found that they needed to add “orphan” satellite galaxies (galaxies which exist without a corresponding subhalo) in order to match the small-scale clustering seen in observations (Kitzbichler & White 2008).”
• THE CONTRIBUTION OF STARBURSTS AND NORMAL GALAXIES TO INFRARED LUMINOSITY FUNCTIONS AT z < 2 (2012, background): “The fact that the evolution of the IR LF is compatible with a universal starburst fraction is surprising since merger rates are expected to decrease with cosmic time (e.g., Kitzbichler & White 2008).”
• What determines satellite galaxy disruption (2009, methodology): “Several analyses assume that a satellite galaxy survives the disruption of its subhalo and eventually merges with its central galaxy by imposing an analytic infall timescale to a galaxy after subhalo disruption (Springel et al. 2001; Kitzbichler & White 2008; Saro et al. 2008; Moster et al. 2009).”
• CAN MINOR MERGING ACCOUNT FOR THE SIZE GROWTH OF QUIESCENT GALAXIES? NEW RESULTS FROM THE CANDELS SURVEY (2011, methodology): “The paradoxical result that the galaxy merger rate remains flat as the halo merger rate increases with redshift has been explored in many theoretical works (e.g., Berrier et al. 2006; Kitzbichler & White 2008).”
• INSPIRALLING SUPERMASSIVE BLACK HOLES: A NEW SIGNPOST FOR GALAXY MERGERS (2008, background): “…formation suggest that close pairs may not be good proxies for mergers (Wetzel et al. 2008) and that merger timescales are typically underestimated (Kitzbichler & White 2008), while morphological merger identification often misclassifies galaxies (De Propris et al. 2007; Lotz et al. 2008).”
• THE GREATER IMPACT OF MERGERS ON THE GROWTH OF MASSIVE GALAXIES: IMPLICATIONS FOR MASS ASSEMBLY AND EVOLUTION SINCE z ≃ 1 (2009, methodology): “The Merger Rate and Merger Rate Mass Function Keeping in mind the substantial uncertainty involved with converting from fpair to a merger rate, we derive merger rates using the assumptions in both Kitzbichler & White (2008) and Patton & Atfield (2008).”
• Galaxy pairs in the Sloan Digital Sky Survey - IV: Interactions trigger AGN (2011, background): “Since the merger timescale may be as long as a gigayear (Kitzbichler & White 2008), this does not provide a strong constraint on a delay between triggered star formation and AGN activity.”
• Dark Matter Substructure in Numerical Simulations: A Tale of Discreteness Noise, Runaway Instabilities, and Artificial Disruption (2018, unknown): “…facilitating a more accurate modeling of ‘orphan galaxies’ in semianalytical models of galaxy formation (e.g., Springel et al. 2001; Kang et al. 2005; Kitzbichler & White 2008), subhalo abundance matching models (e.g., Conroy et al. 2006; Guo & White 2013; Campbell et al. 2017) and empirical…”
• Disruption of Dark Matter Substructure: Fact or Fiction? (2017, background): “…& White 2013; Moster et al. 2017; Campbell et al. 2017), semi-analytical models for galaxy formation (e.g., Springel et al. 2001; Kang et al. 2005; Kitzbichler & White 2008), and other studies that rely on the phase-space distribution of subhaloes (e.g., Faltenbacher & Diemand 2006; Wu et al.…”
• THE MAJOR AND MINOR GALAXY MERGER RATES AT z < 1.5 (2011, background): “It is worth noting that close pair samples are likely to be biased towards objects in groups or clusters (Barton et al. 2007), although simulations suggest that the majority of these objects will merge (Kitzbichler & White 2008).”
• MERGERS IN ΛCDM: UNCERTAINTIES IN THEORETICAL PREDICTIONS AND INTERPRETATIONS OF THE MERGER RATE (2010, methodology): “…(±0.15Gyr).14 We use 14 The merger timescale from simulations at this radius is somewhat shorter than the time obtained assuming dynamical frictionand circular orbits in e.g. an isothermal sphere, as has commonly been done (thisis as umed in e.g. both Patton et al. 2002; Kitzbichler & White 2008).”
• Galaxy merger morphologies and time-scales from simulations of equal-mass gas-rich disc mergers (2008, background): “…the observed number density of galaxy mergers into a galaxy merger rate ⋆ NOAO Leo Goldberg Fellow † W.M. Keck Fellow and the comparison of this galaxy merger rate to the cosmological predictions for dark matter halo assembly (e.g. Berrier et al. 2007; Guo & White 2008; Kitzbichler & White 2008).”
• THE ASSEMBLY OF MILKY-WAY-LIKE GALAXIES SINCE z ∼ 2.5 (2013, background): “Furthermore, major mergers may be too rare to form many bulges (e.g., Kitzbichler & White 2008), and several studies have suggested alternative waysto build up central mass concentrations.”
• Expected properties of the first gravitational wave signal detected with pulsar timing arrays (2015, methodology): “Finally, we take merger time-scales τ estimated by Kitzbichler & White (2008) and Lotz et al. (2010).”
• 3D-HST: A WIDE-FIELD GRISM SPECTROSCOPIC SURVEY WITH THE HUBBLE SPACE TELESCOPE (2012, methodology): “Within the 3D-HST sample, the pair fraction can be measured as a function of mass and redshift, and the fractions can be turned into a merger rate using models (e.g., Kitzbichler & White 2008; Lotz et al. 2011; Williams et al. 2011).”
• Systematic investigation of the expected gravitational wave signal from supermassive black hole binaries in the pulsar timing band (2012, methodology): “Galaxy merger timescalesτ were carefully estimated by Kitzbichler & White (2008) using mock catalogues of galaxy pairs in the Millennium simulation (Springel et al. 2005).”