A Merger-driven Scenario for Cosmological Disk Galaxy Formation

By Brant Robertson, James S. Bullock, Thomas J. Cox, T. Di Matteo, L. Hernquist, Volker Springel, Naoki Yoshida. 2005

441 citations recorded by the source corpus.

The hierarchical nature of the ΛCDM cosmology poses serious difficulties for the formation of disk galaxies. To help resolve these issues, we describe a new, merger-driven scenario for the cosmological formation of disk galaxies at high redshifts that supplements the standard dissipational collapse model. In this picture, large gaseous disks may be produced from high angular momentum mergers of systems that are gas dominated, i.e., Mgas/(Mgas + M⋆) ≳ 0.5 at the height of the merger. Pressurization from the multiphase ISM prevents the complete conversion of gas into stars during the merger, and if enough gas remains to form a disk, the remnant eventually resembles a disk galaxy. We perform numerical simulations of galaxy mergers to study how supernovae feedback strength, black hole feedback, progenitor gas fraction, merger mass ratio, and orbital geometry impact the formation of remnant disks. We find that disks can build angular momentum through mergers and the degree of rotational support of the baryons in the remnant is primarily related to feedback processes associated with star formation. Disk-dominated remnants are restricted to form in mergers that are gas dominated at the time of final coalescence. We also show that the formation of rotationally supported stellar systems in mergers is not restricted to idealized orbits, and both gas-rich major and minor mergers can produce disk-dominated stellar remnants. We suggest that the hierarchical nature of the ΛCDM cosmology and the physics of the ISM may act together to form spiral galaxies by building the angular momentum of disks through gas-dominated mergers at high redshifts.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/e3fe0cd054dca925603e15c346b9454367f31b1d

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In Astronomy and Astrophysics

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

Citations in the corpus

• Riding the Spiral Waves: Implications of Stellar Migration for the Properties of Galactic Disks (2008, background): “In a universe where mass assembles by accretion of progressively larger constituents, thin disks of galaxies form during quiescent evolution following the major merging epoch (Brook et al. 2004; Robertson et al. 2006).”
• Misaligned angular momentum in hydrodynamic cosmological simulations: warps, outer discs and thick discs (2010, background): “…assemble primarily from the quiescent cooling of shock-heated gas after the last major merger (e.g. Fall & Efstathiou 1980; Brook et al. 2004; Robertson et al. 2006), although depending on the mass of the galaxy, cold accretion also plays an important role in providing disc gas (e.g. Kereš…”
• Merger Histories of Galaxy Halos and Implications for Disk Survival (2007, background): “Multiple events of this kind could be important in forming elliptical galaxies (Hernquist 1993; Boylan-Kolchin et al. 2005; Robertson et al. 2006a; Naab et al. 2006).”
• Constraining the galaxy–halo connection over the last 13.3 Gyr: star formation histories, galaxy mergers and structural properties (2017, background): “Galaxy major dry mergers are expected to change morphologies (e.g. Toomre & Toomre 1972; Barnes & Hernquist 1996; Robertson et al. 2006b,a; Burkert et al. 2008).”
• BULGES OF NEARBY GALAXIES WITH SPITZER: SCALING RELATIONS IN PSEUDOBULGES AND CLASSICAL BULGES (2010, background): “Robertson et al. (2006) show that rotationally supported disks can be formed in very gas-rich mergers which are more likely at high redshift.”
• Cosmological simulations of black hole growth: AGN luminosities and downsizing (2013, unknown): “…to the Bondi–Hoyle–Littleton formula was assumed (Di Matteo, Springel & Hernquist 2005; Springel, Di Matteo & Hernquist 2005; Hopkins et al. 2006; Robertson et al. 2006; Li et al. 2007; Sijacki et al. 2007; Johansson, Naab & Burkert 2009; Fabjan et al. 2010; Choi et al. 2013; Barai et al.…”
• MERGERS IN ΛCDM: UNCERTAINTIES IN THEORETICAL PREDICTIONS AND INTERPRETATIONS OF THE MERGER RATE (2010, background): “…Abadi et al. 2003; Governato et al. 2007; Okamoto et al. 2005; Scannapieco et al. 2008, and references therein) and emphasis on gas-richness as a stabilizing factor (Robertson et al. 2006; Hopkins et al. 2009a; Stewart et al. 2009b; Moster et al. 2010a) that allows disks to survive such mergers.”
• The effect of mass ratio on the morphology and time-scales of disc galaxy mergers: Effect of mass ratio on merger morphology (2009, background): “Most previous theoretical studies of minor mergers have focused on the structures of the merger remnants (e.g. Hopkins et al. 2009; Naab et al. 2009; Robertson et al 2006; Bournaud, Jog, & Combes et al. 2004; Johnston et al. 1996) or spanned a very limited range of parameter space (Conselice 2006).”
• Galaxy merger morphologies and time-scales from simulations of equal-mass gas-rich disc mergers (2008, background): “Also, simulations of galaxy mergers often show significant star-formation and disc components well after the merger event (Springel & Hernquist 2005; Robertson et al. 2006a; Naab, Jesseit, & Burkert 2006; Cox et al. 2006, 2008; Khalatyan et al 2008), thus the photometric and morphological…”
• The Relation between Quasar and Merging Galaxy Luminosity Functions and the Merger-driven Star Formation History of the Universe (2006, methodology): “Feedback from supernovae is captured in this subresolution model through an effective equation of state for star-forming gas, enabling us to stably evolve disks with arbitrary gas fractions (see, e.g., Springel et al. 2005b; Springel & Hernquist 2005; Robertson et al. 2004, 2006b).”
• Compact high-redshift galaxies are the cores of the most massive present-day spheroids (2009, background): “…as in these cases the relevant physics lead to qualitatively different behaviour in mergers, and will not necessarily make spheroids at all (Robertson et al. 2006; Hopkins et al. 2009b,f). observations suggest that of the order of half of the massive cores of today’s massive ellipticals…”
• Structure and Kinematics of Early-Type Galaxies from Integral Field Spectroscopy (2016, background): “…for easily measurable properties of galaxies as a function of time (redshift), which can be directly compared with numerical simulations (e.g. Robertson et al. 2006; Boylan-Kolchin et al. 2006; Oser et al. 2012; Porter et al. 2014); and (ii) due to the fact that scaling parameters are…”
• The Kinematic Structure of Merger Remnants (2006, methodology): “However, these simulations did not include gas physics, and hence would not induce starbursts, quasar activity, nor satisfy the scaling relations of elliptical galaxies (Robertson et al. 2006a).”
• The ATLAS3D project – I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria (2010, background): “…the gas tends to form a disk, so that the end result of the merger, after the gas has been removed from the system by ejection, heating or conversion to stars, will be a red stellar system dominated by rotation (Cox et al. 2006; Naab et al. 2006; Robertson et al. 2006; Jesseit et al. 2009).”
• Molecular Hydrogen and Global Star Formation Relations in Galaxies (2007, methodology): “Artificial fragmentation of the ISM in disks may be closely relat d to the angular momentum problem for producing realistic disk galaxies in cosmological simulations (see, e.g., §6 ofRobertson et al. (2004) and Robertson et al. (2006a)).”
• DISSIPATION AND EXTRA LIGHT IN GALACTIC NUCLEI. II. “CUSP” ELLIPTICALS (2008, methodology): “We consider a series of several hundred simulations of colliding galaxies, described in Robertson et al. (2006b, 2006c) and Cox et al. (2006a, 2006b).”
• A semi-analytic model for the co-evolution of galaxies, black holes and active galactic nuclei (2008, methodology): “Di Matteo et al. (2005) and Robertson et al. (2006c) found that the merger simulations naturally produced black holes and spheroidal remnants that obeyed the observed BH mass versus spheroid mass relationship.”
• THICK DISKS OF EDGE-ON GALAXIES SEEN THROUGH THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S4G): LAIR OF MISSING BARYONS? (2011, background): “Later models using disk–disk gas-rich mergers (Robertson et al. 2006; Brook et al. 2007; Richard et al. 2010) are able to produce reasonable thick disks from stars from the progenitor galaxies plus stars created during the merger, with the stars which are created later settling in a thin disk.”
• THE THICK DISKS OF SPIRAL GALAXIES AS RELICS FROM GAS-RICH, TURBULENT, CLUMPY DISKS AT HIGH REDSHIFT (2009, background): “In the cosmological model of galaxy formation, gas-rich mergers are necessary to preserve disks and build spiral galaxies (e.g., Robertson et al. 2006).”
• How do massive black holes get their gas (2009, methodology): “These simulations and the methodology used for building the initial galaxies are described in more detail in a series of papers (see e.g. Di Matteo et al. 2005; Cox et al. 2006; Robertson et al. 2006a; Younger et al. 2008).”