Formation of a Spiral Galaxy in a Major Merger

By Volker Springel, L. Hernquist. 2004

332 citations recorded by the source corpus.

We use numerical simulations to examine the structure of merger remnants resulting from collisions of gas-rich spiral galaxies. When the gas fraction of the progenitors is small, the remnants structurally and kinematically resemble elliptical galaxies, in agreement with earlier work. However, if the progenitor disks are gas-dominated, new types of outcomes are possible, where a prominent disk may survive in certain cases. To illustrate this scenario, we analyze an extreme example with progenitor galaxies consisting of dark matter halos, pure gas disks, and no bulges, as might be appropriate for mergers at high redshifts. While rapid star formation triggered by tidal torques during the merger forms a central, rotating bulge in the remnant, not all the gas is consumed in the burst. The remaining gas cools quickly and settles into an extended star-forming disk, yielding an object similar to a spiral galaxy and not an early-type galaxy. This is contrary to the usual view that major mergers invariably destroy disks. The morphological evolution of galaxies can therefore be more complicated than often assumed, and in particular, theoretical constraints based on the fragility of spiral disks need to be reevaluated.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/266bf5a4f2261c22f9302571a579be88283d951b

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In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. R. Somerville
4. Volker Springel
5. Thomas J. Cox
6. A. Dekel
7. R. Dav'e
8. T. Naab

In Instrumentation

1. P. Hopkins
2. L. Hernquist
3. R. Somerville
4. Thomas J. Cox
5. A. Dekel
6. M. Cappellari
7. Volker Springel
8. R. Dav'e

Citations in the corpus

• Evolution of magnetic fields in galaxies and future observational tests with the Square Kilometre Array (2008, background): “The disk started forming in galaxies with M >∼ 1011 M immediately after the last gas-rich major merger with substantial stellar feedback (Elmegreen et al. 2005; Springel & Hernquist 2005) at zllm ∼ 2.”
• Star formation in galaxy mergers with realistic models of stellar feedback and the interstellar medium (2012, methodology): “Even a small mass fraction of a few per cent formed in these nuclear starbursts can have dramatic implications for the mass profile structure (Mihos & Hernquist 1994a), phase-space densities (Hernquist et al. 1993), rotation and higher order kinematics (Cox et al. 2006b), kinematically decoupled com”
• Modelling feedback from stars and black holes in galaxy mergers (2004, methodology): “In our new simulations, the remnants have smoother C© 2005 RAS, MNRAS 361, 776–794 Downloaded from https://academic.oup.com/mnras/article-abstract/361/3/776/972342 by guest on 30 July 2018 luminosity profiles into their centres, in much better agreement with observations of elliptical galaxies (Spri”
• Black Holes in Galaxy Mergers: Evolution of Quasars (2005, methodology): “Together with the modeling presented by Di Matteo et al. (2005), Springel et al. (2005a,b), Springel & Hernquist (2005), Hopkins et al. (2005a,b,c), and Robertson et al. (2005), the results described here motivate the following picture for galaxy formation and evolution.”
• The effects of gas on morphological transformation in mergers: implications for bulge and disc demographics (2009, background): “…of bulge formation in the merger owing to its gas-richness, combined with rapid large-scale gas inflows concurrent with and subsequent to the merger, both contribute to the rapid rebuilding of a disc-dominated galaxy following the event (Springel & Hernquist 2005; Robertson et al. 2006a).”
• MERGERS AND BULGE FORMATION IN ΛCDM: WHICH MERGERS MATTER? (2009, background): “…what has now been seen in essentially all simulations of sufficiently high gas-fraction disks (both high-resolution and cosmological; see e.g. Springel & Hernquist 2005; Robertson et al. 2006; Cox et al. 2008; Robertson & Bullock 2008; Okamoto et al. 2005; Scannapieco et al. 2008; Governato…”
• Formation of z~6 Quasars from Hierarchical Galaxy Mergers (2006, methodology): “This EOS describes the dynamics of star-forming gas, accounts for the consequences of stellar feedback on galactic scales, and enables us to construct equilibrium disk models even with large gas fractions (Robertson et al. 2004; Springel & Hernquist 2005).”
• Moving mesh cosmology: numerical techniques and global statistics (2011, background): “Thus, conclusions drawn from studies of galaxy collisions with SPH, such as the stellar profiles of merger remnants and their evolution (e.g. Hopkins et al. 2008, 2009a,b,c) or the survivability of discs during mergers (Springel & Hernquist 2005), are likely robust to variations in the hydro solver.”
• Forming disc galaxies in ΛCDM simulations (2006, background): “Other recent papers have investigated the roles of a top heavy initial mass function (IMF) (Okamoto et al. 2005) and of massive galaxy outflows driven by quasi-stellar object (QSO) activity (Binney, Gerhard & Silk 2001; Granato et al. 2004; Di Matteo, Springel & Hernquist 2005) in regulating galaxy ”
• A Merger-driven Scenario for Cosmological Disk Galaxy Formation (2005, methodology): “Remarkably, some highly noncoplanar encounters produce remnants whose entire stellar remnant is rapidly rotating (models GCoF and GCoO), demonstrating that merger-driven disk formation is not limited to the single coplanar orbit discussed by Springel & Hernquist (2005).”
• How do massive black holes get their gas (2009, methodology): “Feedback from the starburst and a central active galactic nucleus (AGN) may also be important, both for regulating the BH’s growth (Di Matteo, Springel & Hernquist 2005; Hopkins et al. 2005; Johansson, Burkert & Naab 2009b; DeBuhr et al. 2010) and for shutting down future star formation (Springel, D”
• Discriminating Between the Physical Processes that Drive Spheroid Size Evolution (2009, methodology): “Those simulations include self-consistent models for star formation and BH growth, and feedback from both, that enable the stable evolution of even very gas rich systems (Springel & Hernquist 2005; Springel, Di Matteo & Hernquist 2005b).”
• The effect of gas fraction on the morphology and time-scales of disc galaxy mergers (2009, background): “…NOAO Leo Goldberg Fellow † W.M. Keck Fellow Jesseit, & Burkert 2006; Khalatyan et al. 2008), while the remnants of extremely gas-rich mergers can preserve discs large enough to resemble present-day spiral galaxies (e.g. Springel & Hernquist 2005; Robertson et al. 2006b; Hopkins et al. 2009).”
• Galaxy formation theory (2010, background): “Under certain conditions, major mergers of very gas rich systems can lead to the reformation of a disk after the merger is over (Barnes 2002; Springel and Hernquist 2005; Robertson et al. 2006a).”
• There's no place like home? Statistics of Milky Way-mass dark matter haloes (2009, background): “…studies have shown that factors such as the orbits and gas content of the merging galaxies can have a substantial impact on remnant properties (Springel & Hernquist 2005; Kazantzidis et al. 2008, 2009; Scannapieco et al. 2009; Hopkins et al. 2009; Purcell et al. 2009; Stewart et al. 2009;…”
• CONNECTING ANGULAR MOMENTUM AND GALACTIC DYNAMICS: THE COMPLEX INTERPLAY BETWEEN SPIN, MASS, AND MORPHOLOGY (2015, background): “This could indicate that there are different formation channels for disk-like systems, e.g., gas-rich major mergers, as discussed in Springel & Hernquist (2005) and Schlachtberger (2014).”
• Photometric scaling relations of lenticular and spiral galaxies (2010, background): “In this picture, a new disk is formed of the gas, which gradually settles into the disk plane from the dark matter halo (Kauffman et al. 1999; Springel & Hernquist 2005).”
• Toy models for galaxy formation versus simulations (2013, methodology): “The average growth of a halo, following its main progenitor, has been derived by a fit to merger trees from the Millennium cosmological simulation (Springel & Hernquist 2005), using a functional form that is motivated by the EPS approximation (Neistein & Dekel 2008b).”
• Theoretical Challenges in Galaxy Formation (2016, background): “Assuming a Bondi-like accretion and a relatively simple scaling for energy feedback in a sub-resolution model , it was also possible to provide an explanation for the observed stellar mass black hole mass relation (Di Matteo, Springel & Hernquist 2005).”