The Kinematic Structure of Merger Remnants

By Thomas J. Cox, S. Dutta, T. Di Matteo, L. Hernquist, P. Hopkins, Brant Robertson, Volker Springel Harvard-CfA, Carnegie-Mellon, Mpa. 2006

315 citations recorded by the source corpus.

We use numerical simulations to study the kinematic structure of remnants formed from mergers of equal-mass disk galaxies. In particular, we show that remnants of dissipational mergers, which include the radiative cooling of gas, star formation, feedback from supernovae, and the growth of supermassive black holes, are smaller, rounder, have, on average, a larger central velocity dispersion, and show significant rotation compared to remnants of dissipationless mergers. The increased rotation speed of dissipational remnants owes its origin to star formation that occurs in the central regions during the galaxy merger. We have further quantified the anisotropy, three-dimensional shape, minor-axis rotation, and isophotal shape of each merger remnant, finding that dissipational remnants are more isotropic, closer to oblate, have the majority of their rotation along their major axis, and are more disky than dissipationless remnants. Individual remnants display a wide variety of kinematic properties. A large fraction of the dissipational remnants are oblate isotropic rotators. Many dissipational remnants, and all of the dissipationless ones, are slowly rotating and anisotropic. The remnants of gas-rich major mergers can well reproduce the observed distribution of projected ellipticities, rotation parameter (V/σ)*, kinematic misalignments, Ψ, and isophotal shapes. The dissipationless remnants are a poor match to this data. We also investigate the properties of merger remnants as a function of initial disk gas fraction, orbital angular momentum, and the mass of the progenitor galaxies. Our results support the merger hypothesis for the origin of low-luminosity elliptical galaxies provided that the progenitor disks are sufficiently gas-rich, however our remnants are a poor match to the bright ellipticals that are slowly rotating and uniformly boxy.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/fb134dc82807f0c1d7b7234b2753708393e5b441

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Galaxy morphology and star formation in the Illustris Simulation at z = 0 (2015, background): “Therefore, observational constraints which have been tested with idealized merger simulations (Cox et al. 2006; Moody et al. 2014b) or small samples of cosmological simulations (Naab et al. 2014) can also now be tested with large-scale hydrodynamical simulations.”
Feedback in simulations of disc-galaxy major mergers (2005, background): “…1996; Springel 2000; Naab & Trujillo 2005), the kinematic structure of merger remnants (Naab & Burkert 2003; González-Garćıa & van Albada 2005a,b; Cox et al. 2006), or if the merger remnants fall on the fundamental plane (Bekki & Shioya 1997; Bekki 1998; Naab & Burkert 2003; Dantas et al.…”
Formation of z~6 Quasars from Hierarchical Galaxy Mergers (2006, background): “…the MBH- relation (Di Matteo et al. 2005; Robertson et al. 2006b), galaxy colors (Springel et al. 2005a; Hopkins et al. 2006c), X-ray gas emission (Cox et al. 2006a), elliptical kinematics (Cox et al. 2006b), the fundamental plane (Robertson et al. 2006a), quasar properties (Hopkins et al. 2005a,…”
Luminous Infrared Galaxies with the Submillimeter Array. I. Survey Overview and the Central Gas to Dust Ratio (2008, methodology): “Finally, we will make detailed comparisons between the molecular gas and dust properties of these U/LIRGs and the predictions of numerical simulations of merging galaxies (e.g., Cox et al. 2006; Chakrabarti et al. 2007).”
The SAURON project – X. The orbital anisotropy of elliptical and lenticular galaxies: revisiting the (V/σ, ɛ) diagram with integral‐field stellar kinematics (2007, methodology): “In addition, current numerical simulations of gas-free major mergers seem to generate large fractions of strongly triaxial or prolate galaxies (0.2<∼ ε<∼ 0.6) than we donot observe (e.g. Boylan-Kolchin, Ma, & Quataert 2005; Burkert & Naab 2005; González-Garcı́a & van Albada 2005; Cox et al. 2006).”
The mean star formation rate of X-ray selected active galaxies and its evolution from z~2.5: results from PEP-Herschel (2012, methodology): “We use the models studied by Wuyts et al. (2010) which focus on progenitor galaxies with size and high gas content as expected for z∼2 mergers, as well as a fully analogous set of models which encompass the larger sizes and lower gas content of local mergers (Cox et al. 2006).”
Moving mesh cosmology: numerical techniques and global statistics (2011, methodology): “These properties have made the method also popular for applications other than cosmic structure growth, e.g. for isolated merger simulations (Barnes & Hernquist 1991, 1992, 1996; Mihos & Hernquist 1994, 1996; Naab & Burkert 2003; Cox et al. 2006).”
Bursty stellar populations and obscured active galactic nuclei in galaxy bulges (2007, background): “…of the galaxies, normalized to the same flux scale for each class. gas-rich mergers also produce starbursts (Cattaneo et al. 2005; Di Matteo et al. 2005) and indicate that dynamical signatures on the merger remnants can remain for as much as several Gyr after the original merger (Cox et al. 2006).”
The effect of galaxy mass ratio on merger-driven starbursts (2007, methodology): “This is in contrast to the star–formation history of an isolated spiral, which, as shown in Figure 2 (and in Cox et al. 2006), is independent of the feedback model.”
Forming a large disc galaxy from a z < 1 major merger (2008, background): “…shown how the bulge-todisc (B/D) ratio resulting from a major merger might depend on the orbital parameters, the internal spin of the progenitors, the gas fraction of the parent discs and the efficiency of supernova (SN) feedback (Barnes & Hernquist 1996; Cox et al. 2006; Scannapieco et al. 2008).”
HOW DO DISKS SURVIVE MERGERS? (2008, methodology): “We have also tested our predicted scalings with limited subsets of simulations that vary the pericentric passage distance and the energy of the orbit, described in Robertson et al. (2006a) and Cox et al. (2006b), and find that our estimates are robust to these variations.”
Simulations of binary galaxy mergers and the link with fast rotators, slow rotators, and kinematically distinct cores (2011, background): “…with observed properties of ETGs (Naab & Burkert 2003; Bournaud, Combes & Jog 2004; Bournaud, Jog & Combes 2005; Naab, Jesseit & Burkert 2006a; Cox et al. 2006a, 2008; Rothberg & Joseph 2006; Di Matteo et al. 2007; Burkert et al. 2008; Jesseit et al. 2009; Hoffman et al. 2010; Chilingarian et…”
An analytic model of angular momentum transport by gravitational torques: from galaxies to massive black holes (2010, unknown): “We do not present any new simulations, but instead draw on results that have been described previously in a number of papers (see e.g. Di Matteo et al. 2005; Robertson et al. 2006b; Cox et al. 2006; Younger et al. 2008; Hopkins & Quataert 2010a).”
How do massive black holes get their gas (2009, methodology): “The orbit is a moderately tilted prograde, parabolic case (orbit in Cox et al. 2006).”
A semi-analytic model for the co-evolution of galaxies, black holes and active galactic nuclei (2008, methodology): “Also, some additional metals may be driven out of the galaxies by strong shocks during mergers (Cox et al. 2006a).”
A Cosmological Framework for the Co-Evolution of Quasars, Supermassive Black Holes, and Elliptical Galaxies. I. Galaxy Mergers and Quasar Activity (2007, background): “…(Hopkins et al. 2005a) and starbursts (Chakrabarti et al. 2007) would evolve in this scenario, and to quantify structural properties of the remnant and how they depend on, e.g., the gas fractions of the merging galaxies (Cox et al. 2006a, 2006b; Robertson et al. 2006b, 2006c; Hopkins et al. 2007c).”
DISSIPATION AND EXTRA LIGHT IN GALACTIC NUCLEI. IV. EVOLUTION IN THE SCALING RELATIONS OF SPHEROIDS (2008, methodology): “…with central cusps (power-law nuclear slopes), rapid rotation, or disky isophotal shapes as opposed to central cores, slow rotation, or boxy isophotal shapes (indicators of wet versus dry mergers, discussed in detail in e.g. Paper II and Faber et al. 1997; Naab et al. 2006a; Cox et al. 2006).”
A Theoretical Interpretation of the Black Hole Fundamental Plane (2007, methodology): “…represented as a “tilted” correlation between BH mass and bulge binding energy,MBH ∝ (M∗ σ2)0.71. entrain the larger-scale material and the outflow fails to halt accretion (typical of the early-stage weak winds seen in our simulations in earlier merger stages; see Figure 1 in Cox et al. 2006a).”
The effects of gas on morphological transformation in mergers: implications for bulge and disc demographics (2009, methodology): “…H09), we developed a physical model to explain this behaviour, and used a large suite of hydrodynamic simulations (see Robertson et al. 2006c,b; Cox et al. 2006b,a, 2008) to show that the suppression of bulge formation in mergers of more gas-rich discs can be predicted analytically, and is…”
A Cosmological Framework for the Co-Evolution of Quasars, Supermassive Black Holes, and Elliptical Galaxies. II. Formation of Red Ellipticals (2007, methodology): “Star formation rapidly falls by orders of magnitude after the merger, even in the ‘‘no feedback’’ case, as the majority of the gas supply has been rapidly consumed in a central starburst and much of the remaining gas shock-heated into an X-ray halo (Cox et al. 2006a).”