FORMING REALISTIC LATE-TYPE SPIRALS IN A ΛCDM UNIVERSE: THE ERIS SIMULATION

By J. Guedes, Simone Callegari, P. Madau, Lucio Mayer. 2011

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Simulations of the formation of late-type spiral galaxies in a cold dark matter (ΛCDM) universe have traditionally failed to yield realistic candidates. Here we report a new cosmological N-body/smooth particle hydrodynamic simulation of extreme dynamic range in which a close analog of a Milky Way disk galaxy arises naturally. Named “Eris,” the simulation follows the assembly of a galaxy halo of mass Mvir = 7.9 × 1011 M☉ with a total of N = 18.6 million particles (gas + dark matter + stars) within the final virial radius, and a force resolution of 120 pc. It includes radiative cooling, heating from a cosmic UV field and supernova explosions (blastwave feedback), a star formation recipe based on a high gas density threshold (nSF = 5 atoms cm−3 rather than the canonical nSF = 0.1 atoms cm−3), and neglects any feedback from an active galactic nucleus. Artificial images are generated to correctly compare simulations with observations. At the present epoch, the simulated galaxy has an extended rotationally supported disk with a radial scale length Rd = 2.5 kpc, a gently falling rotation curve with circular velocity at 2.2 disk scale lengths of V2.2 = 214 km s−1, an i-band bulge-to-disk ratio B/D = 0.35, and a baryonic mass fraction within the virial radius that is 30% below the cosmic value. The disk is thin, has a typical H i-to-stellar mass ratio, is forming stars in the region of the ΣSFR–ΣH i plane occupied by spiral galaxies, and falls on the photometric Tully–Fisher and the stellar-mass–halo-virial-mass relations. Hot (T > 3 × 105 K) X-ray luminous halo gas makes up only 26% of the universal baryon fraction and follows a “flattened” density profile ∝r−1.13 out to r = 100 kpc. Eris appears then to be the first cosmological hydrodynamic simulation in which the galaxy structural properties, the mass budget in the various components, and the scaling relations between mass and luminosity are all consistent with a host of observational constraints. A twin simulation with a low star formation density threshold results in a galaxy with a more massive bulge and a much steeper rotation curve, as in previously published work. A high star formation threshold appears therefore key in obtaining realistic late-type galaxies, as it enables the development of an inhomogeneous interstellar medium where star formation and heating by supernovae occur in a clustered fashion. The resulting outflows at high redshifts reduce the baryonic content of galaxies and preferentially remove low-angular-momentum gas, decreasing the mass of the bulge component. Simulations of even higher resolution that follow the assembly of galaxies with different merger histories shall be used to verify our results.

Subfields: Astronomy and Astrophysics, Instrumentation, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/6d719f03d2c15aa809c54b72e36c939c49533d37

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Citations in the corpus

The Fermi Galactic Center GeV Excess and Implications for Dark Matter (2017, background): “Modified NFW profiles with γ>1 are expected from numerical simulations of DM halos including baryons (e.g., Guedes et al. 2011).”
ON THE INTERPLAY BETWEEN STAR FORMATION AND FEEDBACK IN GALAXY FORMATION SIMULATIONS (2014, background): “As shown in the figure, the constant threshold model is in fairly good agreement with the SFH of the Eris simulation (Guedes et al. 2011), which also adopted the constant threshold based star formation model, but with the threshold of n?”
THE ASSEMBLY OF MILKY-WAY-LIKE GALAXIES SINCE z ∼ 2.5 (2013, background): “…data also provide key constraints on the ingredients in recent hydrodynamical models: these models now succeed in reproducing many of the properties of the present-day Milky Way (Brooks et al. 2011; Guedes et al. 2011) and to improve them further we need to test their predictions at earlier times.”
Towards a more realistic population of bright spiral galaxies in cosmological simulations (2013, methodology): “Disk fractions in simulations are sometimes quantified by mock photometric surface brightness decompositions (see e.g. Agertz et al. 2011; Guedes et al. 2011).”
Galaxy Evolution in Cosmological Simulations with Outflows II: Metallicities and Gas Fractions (2011, background): “In high-resolution simulations of individual galaxies (e.g. Guedes et al. 2011), it is seen that raising the threshold density does lower the gas fraction, but this is also sensitively dependent on their feedback algorithm which is quite different than ours.”
Cosmic ray driven outflows in global galaxy disc models (2013, background): “The IMF is probably the most uncertain (e.g. Cappellari et al. 2012), and our choice is relatively conservative (for instance Guedes et al. 2011, who adopt an effective SNe 1.8 times larger than this).”
MaGICC discs: matching observed galaxy relationships over a wide stellar mass range (2012, background): “A contrasting model invoking energy ‘feedback’ from supernovae (SNe) to regulate star formation has successfully simulated dwarf and Milky Way mass galaxies that share many properties of observed galaxies (Governato et al. 2010; Guedes et al. 2011; Piontek & Steinmetz 2011).”
THE HISTORY OF R-PROCESS ENRICHMENT IN THE MILKY WAY (2014, methodology): “R-Process Production Sites and Injection History The key ingredient in our analysis is the realistic star formation history (SFH) of a galaxy simulated in a cosmological context which at redshiftz = 0 is a close analog of the Milky Way (Guedes et al. 2011).”
THE DEPENDENCE OF QUENCHING UPON THE INNER STRUCTURE OF GALAXIES AT 0.5 ⩽ z < 0.8 IN THE DEEP2/AEGIS SURVEY (2012, background): “It is good to be cautious since the ERIS Milky Way simulation (Guedes et al. 2011) develops a red bulge and high central stellar density quite naturally through mergers and/or inter al disk evolution.”
Radial migration in disc galaxies — I. Transient spiral structure and dynamics (2011, background): “We hope that it shouldsoon be possible to use state-of-the-art cosmological simulations (e.g. Guedes et al. 2011; Agertz et al. 2011) for detailed studies of radial migration. c© 0000 RAS, MNRAS000, 000–000”
A DIRECT MEASUREMENT OF THE BARYONIC MASS FUNCTION OF GALAXIES AND IMPLICATIONS FOR THE GALACTIC BARYON FRACTION (2012, methodology): “For example, the high-resolution Eris simulation (Guedes et al. 2011) has managed to produce a Milky-Way type object with values of η∗ in agreement with those that we see in Fig.”
Moving mesh cosmology: numerical techniques and global statistics (2011, methodology): “…have been made recently in studying disc formation numerically using zoom-in procedures in cosmological SPH simulations (e.g. Agertz et al. 2011; Guedes et al. 2011), we do not think that these successes provide much evidence for the numerical reliability of SPH, although this misconception…”
BARYONS MATTER: WHY LUMINOUS SATELLITE GALAXIES HAVE REDUCED CENTRAL MASSES (2012, background): “However, Governato et al. (2010) and Guedes et al. (2011) showed that, even at high resolution, if star formation is allowed to occur diffusely across the disk, no large scale outflows are generated.”
Galaxy morphology and star formation in the Illustris Simulation at z = 0 (2015, background): “By including significant feedback from supernovae, massive star formation, and supermassive black holes, the realism of resulting galaxy models has continued to improve (e.g., Crain et al. 2009; Guedes et al. 2011; Ceverino et al. 2014; Cen 2014).”
A DIVERSITY OF PROGENITORS AND HISTORIES FOR ISOLATED SPIRAL GALAXIES (2012, background): “An exception has recently been published by Guedes et al. (2011), whose disk galaxy does sit on the observed stellar-to-halo mass relation.”
Introducing the Illustris Project: simulating the coevolution of dark and visible matter in the Universe (2014, methodology): “These cosmological simulations of the formation of representative galaxy populations are different from studies where the computational power is focused on a single galaxy (e.g. Guedes et al. 2011; Scannapieco et al. 2012; Aumer et al. 2013; Kim et al. 2014; Marinacci, Pakmor & Springel 2014a).”
A model for cosmological simulations of galaxy formation physics: multi-epoch validation (2013, background): “…simulations of the formation of representative galaxy populations are markedly different from studies where the computational power is focused on a single galaxy (e.g., Governato et al. 2010; Agertz et al. 2011; Guedes et al. 2011; Genel et al. 2012; Scannapieco et al. 2012; Aumer et al. 2013).”