New Techniques for Relating Dynamically Close Galaxy Pairs to Merger and Accretion Rates: Application to the Second Southern Sky Redshift Survey

By David R. Patton, R. Carlberg, R. Marzke, C. Pritchet, Luiz Nicolaci da Costa, P. Pellegrini. 2000

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The galaxy merger and accretion rates, and their evolution with time, provide important tests for models of galaxy formation and evolution. Close pairs of galaxies are the best available means of measuring redshift evolution in these quantities. In this study, we introduce two new pair statistics, which relate close pairs to the merger and accretion rates. We demonstrate the importance of correcting these (and other) pair statistics for selection effects related to sample depth and completeness. In particular, we highlight the severe bias that can result from the use of a flux-limited survey. The first statistic, Nc, gives the number of companions per galaxy within a specified range in absolute magnitude. Nc is directly related to the galaxy merger rate. The second statistic, Lc, gives the total luminosity in companions, per galaxy. This quantity can be used to investigate the mass accretion rate. Both Nc and Lc are related to the galaxy correlation function ξ and luminosity function ϕ(M) in a straightforward manner. Both statistics have been designed with selection effects in mind. We outline techniques that account for various selection effects and demonstrate the success of this approach using Monte Carlo simulations. If one assumes that clustering is independent of luminosity (which is appropriate for reasonable ranges in luminosity), then these statistics may be applied to flux-limited surveys. These techniques are applied to a sample of 5426 galaxies in the Second Southern Sky Redshift Survey (SSRS2). This is the first large, well-defined low-z survey to be used for pair statistics. Using close (5 h-1 kpc ≤ rp ≤ 20 h-1 kpc) dynamical (Δv ≤ 500 km s-1) pairs, we find Nc(-21 ≤ MB ≤ -18) = 0.0226 ± 0.0052 and Lc(-21 ≤ MB ≤ -18) = 0.0216 ± 0.0055 × 1010 h2 L☉ at z = 0.015. These are the first secure estimates of low-redshift pair statistics, and they will provide local benchmarks for ongoing and future pair studies. If Nc remains fixed with redshift, simple assumptions imply that ~6.6% of present day galaxies with -21 ≤ MB ≤ -18 have undergone mergers since z = 1. When applied to redshift surveys of more distant galaxies, these techniques will yield the first robust estimates of evolution in the galaxy merger and accretion rates.

Subfields: Applied Mathematics, Astronomy and Astrophysics, Statistics and Probability

View Paper: https://www.semanticscholar.org/paper/6977f413f1296cfa348bf741f7b4c05b29969f9b

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Citations in the corpus

Ongoing assembly of massive galaxies by major merging in large groups and clusters from the SDSS (2007, background): “Many studies have identified major-merger candidates by either close pairs (Carlberg et al. 1994; Patton et al. 2000; Carlberg et al. 2000; Patton et al. 2002; Bundy et al. 2004; Lin et al. 2004) or disturbed morphologies (Le Fèvre et al. 2000; Conselice et al. 2003; Lotz & et al. 2006), but these…”
THE FREQUENCY OF TIDAL FEATURES ASSOCIATED WITH NEARBY LUMINOUS ELLIPTICAL GALAXIES FROM A STATISTICALLY COMPLETE SAMPLE (2009, methodology): “As an alternative approach we analyze the interacting pairs in the sample using friction timescale approximations as suggested by, e.g., Patton et al. (2000).”
The role of minor mergers in the recent star formation history of early-type galaxies (2007, background): “We should mention first that several observational studies have looked at closepairs from a variety of surveys across a range of redshifts (e.g. Patton et al. 2000; Le Fèvre et al. 2000).”
Early and Rapid Merging as a Formation Mechanism of Massive Galaxies: Empirical Constraints (2005, methodology): “Merger fractions and histories derived using pairs of galaxies (§3.1) come from Patton et al. (2000), Le Févre et al. (2000), Patton et al. (2002) and Lin et al. (2005) at z < 1.”
Galaxy pairs in the Sloan Digital Sky Survey – VI. The orbital extent of enhanced star formation in interacting galaxies (2013, methodology): “Following Patton et al. (2000), we weight the observed pair fraction bythe reciprocal of the overall spectroscopic completeness of the survey (88 per cent according to Patton & Atfield 2008), and also weight close angular pairs by an additional factor of 3.08 (see Section 3), and find that 12.3 per…”
ACTIVE GALACTIC NUCLEUS HOST GALAXY MORPHOLOGIES IN COSMOS (2009, methodology): “We define the maximum projected physical separation of close pairs as Rmaxp , and use R max p = 20,50,100h−1 kpc in three separate trials (see Patton et al. 2000, 2002).”
Very Small Scale Clustering and Merger Rate of Luminous Red Galaxies (2005, methodology): “In previous work, there are two main methods for measuring merger rates; the most popular one is to convert the close pair statistics to a merger rate (e.g., Zepf & Koo 1989; Burkey et al. 1994; Patton et al. 1997, 2000; Carlberg et al. 2000; Bell et al. 2006).”
The DEEP2 Galaxy Redshift Survey: Evolution of Close Galaxy Pairs and Major-Merger Rates up to z ~ 1.2 (2004, background): “Although mergers are rare today (Patton et al. 2000, hereafter P2000), cold dark matter N -body simulations show merger rates of halos increasing with redshift as (1 + z)m, with 2.5 ≤ m ≤ 3.5 (Governato et al. 1999; Gottlöber, Klypin, & Kravtsov 2001).”
Gravitational Waves Probe the Coalescence Rate of Massive Black Hole Binaries (2002, methodology): “Carlberg et al. (2000), following the method of Patton et al. (2000), estimate the galaxy merger rate out to z ’ 1 in the CNOC2 and CFGRS redshift surveys.”
Star formation in close pairs selected from the Sloan Digital Sky Survey (2004, background): “This is a relaxed constraint. which, according to Patton et al. (2000, 2002), includes all potentially interacting systems and avoids a bias toward dynamically bound systems.”
Galaxy merger morphologies and time-scales from simulations of equal-mass gas-rich disc mergers (2008, background): “No such weighting is done for the close pair time-scales as this factor is generally included in the merger rate calculation (e.g. Patton et al. 2000): Γ = 0.5 φ Nc p(merg) T −1 pair (19) where φ is the number density of galaxies within the magnitude range of the observed pairs, Nc is the average…”
Galaxy Interactions Trigger Rapid Black Hole Growth: an unprecedented view from the Hyper Suprime-Cam Survey (2017, background): “…developed to assess the distribution of light within an image in order to separate/quantify a galaxy’s Hubble class and/or interaction stage (e.g., Patton et al. 2000, 2002; Lin et al. 2004; De Propris et al. 2007; Lin et al. 2008; Robaina et al. 2010; Bluck et al. 2012; Glikman et al. 2015 for…”
The Relation between Quasar and Merging Galaxy Luminosity Functions and the Merger-driven Star Formation History of the Universe (2006, background): “…well with previous estimates of the local pair fraction (e.g., Zepf & Koo 1989; Burkley et al. 1994; Carlberg et al. 1994; Yee & Ellingson 1995; Patton et al. 1997, 2000) and the B-band luminosity function of paired galaxies (e.g., Xu& Sulentic 1991; Sulentic & Rabaca 1994; Keel &Wu 1995;…”
THE GREATER IMPACT OF MERGERS ON THE GROWTH OF MASSIVE GALAXIES: IMPLICATIONS FOR MASS ASSEMBLY AND EVOLUTION SINCE z ≃ 1 (2009, background): “Both quantities are uncertain, but previous work has typically assumed that roughly half of close pairs will merge with a typical timescale of 0.5 Gyr (e.g., Patton et al. 2000).”
Galaxy Zoo: the fraction of merging galaxies in the SDSS and their morphologies (2009, background): “For example, Patton et al. (2000) concluded that ∼ 1.1% of nearby galaxies with −21 < MB < −18 are undergoing a merger (but not necessarily a major merger by our definition).”
The effect of mass ratio on the morphology and time-scales of disc galaxy mergers: Effect of mass ratio on merger morphology (2009, background): “No such weighting is done for the close pair time-scales as this factor is generally included in the merger rate calculation (e.g. Patton et al. 2000).”