The effect of mass ratio on the morphology and time-scales of disc galaxy mergers: Effect of mass ratio on merger morphology

By J. Lotz, P. Jonsson, Thomas J. Cox, Joel R. Primack. 2009

185 citations recorded by the source corpus.

The majority of galaxy mergers are expected to be minor mergers. The observational signatures of minor mergers are not well understood, thus there exist few constraints on the minor merger rate. This paper seeks to address this gap in our understanding by determining if and when minor mergers exhibit disturbed morphologies and how they differ from the morphology of major mergers. We simulate a series of unequalmass moderate gas-fraction disc galaxy mergers. With the resulting g-band images, we determine how the time-scale for identifying galaxy mergers via projected separation and quantitative morphology (the Gini coefficient G, asymmetry A, and the secondorder moment of the brightest 20% of the light M20) depends on the merger mass ratio, relative orientations and orbital parameters. We find that G−M20 is as sensitive to 9:1 baryonic mass ratio mergers as 1:1 mergers, with observability time-scales ∼ 0.2−0.4 Gyr. In contrast, asymmetry finds mergers with baryonic mass ratios between 4:1 and 1:1 (assuming local disc galaxy gas-fractions). Asymmetry time-scales for moderate gas-fraction major disc mergers are∼ 0.2−0.4 Gyr, and less than 0.06 Gyr for moderate gas-fraction minor mergers. The relative orientations and orbits have little effect on the time-scales for morphological disturbances. Observational studies of close pairs often select major mergers by choosing paired galaxies with similar luminosities and/or stellar masses. Therefore, the various ways of finding galaxy mergers (G − M20, A, close pairs) are sensitive to galaxy mergers of different mass ratios. By comparing the frequency of mergers selected by different techniques, one may place empirical constraints on the major and minor galaxy merger rates.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Computer Vision and Pattern Recognition

View Paper: https://www.semanticscholar.org/paper/d70576f22752956b3041e42b8f98e07da480d830

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 Atomic and Molecular Physics, and Optics

In Computer Vision and Pattern Recognition

Citations in the corpus

THE MAJOR AND MINOR GALAXY MERGER RATES AT z < 1.5 (2011, methodology): “This is consistent with the results from galaxy merger simulations, which predict that G −M20 identifies merging systems for only a short period while double nuclei are evident (Lotz et al. 2008; Lotz et al. 2010a, b).”
Systematic investigation of the expected gravitational wave signal from supermassive black hole binaries in the pulsar timing band (2012, methodology): “We complemented their equation (10) with a≈ q−0.3 dependence extracted by fitting the results of a set of full hydrodynamical simulation of galaxy mergers presented by Lotz et al. (2010).”
Galaxy morphology and star formation in the Illustris Simulation at z = 0 (2015, methodology): “We measure non-parametric morphologies by using code originally developed for idealized merger simulations (Lotz et al. 2008a, 2010a,b) and also applied to galaxy surveys (Lotz et al. 2004, 2008b, 2011).”
OVERVIEW OF THE SDSS-IV MaNGA SURVEY: MAPPING NEARBY GALAXIES AT APACHE POINT OBSERVATORY (2014, methodology): “Through comparisons with suites of hydrodynamical merger simulations (e.g., Lotz et al. 2010a,b), new statistical metrics can be devised that will help diagnose the merger phase (i.e., first approach, second passage, final coalescence) and the mass ratio of the interacting galaxies.”
Galaxy pairs in the Sloan Digital Sky Survey – VIII. The observational properties of post-merger galaxies (2013, background): “The visual or automated selection of post-mergers, both of which rely on galaxy asymmetry, is likely to be highly skewed towards major mergers, with approximately equal stellar masses (e.g. Lotz et al. 2010).”
SUBMILLIMETER GALAXIES AS PROGENITORS OF COMPACT QUIESCENT GALAXIES (2014, background): “Over the next 10 Gyr, these then grow gradually, primarily through minor merging, into local elliptical galaxies.”
The Evolution of Galaxy Structure Over Cosmic Time (2014, methodology): “Lotz et al. (2008, 2010a) find that the asymmetry time-scales for gas-rich major mergers are 0.2-0.4 Gyr, and 0.06 Gyr for minor mergers (Lotz et al. 2010a).”
Morphologies of z ∼ 0.7 AGN host galaxies in CANDELS: no trend of merger incidence with AGN luminosity (2014, background): “Theoretical models generally predict a delay of about 100 Myr between coalescence and the peak quasar activity (see e.g. Di Matteo et al. 2005; Hopkins et al. 2008), which is a time-scale on which merger signatures should stay very apparent (Lotz et al. 2010a,b).”
ON SIZES, KINEMATICS, M/L GRADIENTS, AND LIGHT PROFILES OF MASSIVE COMPACT GALAXIES AT z ∼ 2 (2010, background): “The timescales of a morphological merger signature depend on mass ratio (Lotz et al. 2010a) and gas fraction (Lotz et al. 2010b) of the merger.”
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).”
CONSTRAINTS ON THE ASSEMBLY AND DYNAMICS OF GALAXIES. I. DETAILED REST-FRAME OPTICAL MORPHOLOGIES ON KILOPARSEC SCALE OF z ∼ 2 STAR-FORMING GALAXIES (2010, background): “There are several inherent difficulties in studies based on morphologies, including bandshifting, intrinsically complex structure, and uncertainties in the timescales over which key merger signatures are observable (e.g., Toft et al. 2007; Elmegreen et al. 2007, 2009; Lotz et al. 2008, 2010a,b).”
CANDELS: CONSTRAINING THE AGN–MERGER CONNECTION WITH HOST MORPHOLOGIES AT z ∼ 2 (2011, background): “If this delay is of the same order as the relaxation time of the galaxy (typically ∼ few 100 Myr), the most obvious signatures of morphological disturbance will have faded by the time it is identified as an X-ray bright AGN (Lotz et al. 2010).”
MERGERS IN ΛCDM: UNCERTAINTIES IN THEORETICAL PREDICTIONS AND INTERPRETATIONS OF THE MERGER RATE (2010, background): “This makes the merger time within ∼ 20− 50kpc shorter by a factor≈ 2, relative to that estimated without baryonic galaxies (see e.g. Lotz et al. 2008a, 2010b,a), and can even lead to the merger and/or destruction of the baryonic galaxiesbeforethe subhalo (their bound dark matter) is significantly…”