Forming early-type galaxies without AGN feedback: a combination of merger-driven outflows and inefficient star formation

Kretschmer, Michael; Teyssier, Romain

doi:10.1093/mnras/stz3495

Cited by 43 publications

(37 citation statements)

References 104 publications

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“…Numerically, our results are in agreement with (but considerably extend) previous simulations of similar systems (e.g. Martig et al 2013;Semenov et al 2016;Su et al 2019;Kretschmer & Teyssier 2020). Like ours, these simulations predict that gas dynamics influence star formation only in sufficiently gas-poor galaxies.…”

Section: Implications For Galaxy Evolution and Quenchingsupporting

confidence: 92%

The elephant in the bathtub: when the physics of star formation regulate the baryon cycle of galaxies

Gensior

Kruijssen

2020

Monthly Notices of the Royal Astronomical Society

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In simple models of galaxy formation and evolution, star formation is solely regulated by the amount of gas present in the galaxy. However, it has recently been shown that star formation can be suppressed by galactic dynamics in galaxies that contain a dominant spheroidal component and a low gas fraction. This ‘dynamical suppression’ is hypothesised to also contribute to quenching gas-rich galaxies at high redshift, but its impact on the galaxy population at large remains unclear. In this paper, we assess the importance of dynamical suppression in the context of gas regulator models of galaxy evolution through hydrodynamic simulations of isolated galaxies, with gas-to-stellar mass ratios of 0.01–0.20 and a range of galactic gravitational potentials from disc-dominated to spheroidal. Star formation is modelled using a dynamics-dependent efficiency per free-fall time, which depends on the virial parameter of the gas. We find that dynamical suppression becomes more effective at lower gas fractions and quantify its impact on the star formation rate as a function of gas fraction and stellar spheroid mass surface density. We combine the results of our simulations with observed scaling relations that describe the change of galaxy properties across cosmic time, and determine the galaxy mass and redshift range where dynamical suppression may affect the baryon cycle. We predict that the physics of star formation can limit and regulate the baryon cycle at low redshifts (z ≲ 1.4) and high galaxy masses (M⋆ ≳ 3 × 1010 M⊙), where dynamical suppression can drive galaxies off the star formation main sequence.

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Section: Implications For Galaxy Evolution and Quenchingsupporting

confidence: 92%

The elephant in the bathtub: when the physics of star formation regulate the baryon cycle of galaxies

Gensior

Kruijssen

2020

Monthly Notices of the Royal Astronomical Society

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“…This is called "subgrid turbulent velocities", which is not taken into account in our simulation or in the previous computation of the turbulent velocity based on neighboring cells. Some other Ramses simulations quantify those subgrid motions on-the-fly (e.g., Agertz et al 2015;Kretschmer & Teyssier 2020). In this work we assume a uniform turbulence in every cell of the simulation, accounting for those two kinds of turbulence.…”

Section: Radiative Transfer Of the Linesmentioning

confidence: 99%

UV absorption lines and their potential for tracing the Lyman continuum escape fraction

Mauerhofer

Verhamme

Blaizot

et al. 2021

A&A

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Context. The neutral intergalactic medium above redshift ∼6 is opaque to ionizing radiation, and therefore indirect measurements of the escape fraction of ionizing photons are required from galaxies of this epoch. Low-ionization-state absorption lines are a common feature in the rest-frame ultraviolet (UV) spectrum of galaxies, showing a broad diversity of strengths and shapes. As these spectral features indicate the presence of neutral gas in front of UV-luminous stars, they have been proposed to carry information on the escape of ionizing radiation from galaxies. Aims. We aim to decipher the processes that are responsible for the shape of the absorption lines in order to better understand their origin. We also aim to explore whether the absorption lines can be used to predict the escape fraction of ionizing photons. Methods. Using a radiation-hydrodynamical cosmological zoom-in simulation and the radiative transfer postprocessing code RASCAS we generated mock C II λ1334 and Lyβ lines of a virtual galaxy at z = 3 with M1500 = −18.5 as seen from many directions of observation. We also computed the escape fraction of ionizing photons in those directions and looked for correlations between the escape fraction and properties of the absorption lines, in particular their residual flux. Results. We find that the resulting mock absorption lines are comparable to observations and that the lines and the escape fractions vary strongly depending on the direction of observation. The effect of infilling due to the scattering of the photons and the use of different apertures of observation both result in either strong or very mild changes of the absorption profile. Gas velocity and dust always affect the absorption profile significantly. We find no strong correlations between observable Lyβ or C II λ1334 properties and the escape fraction. After correcting the continuum for attenuation by dust to recover the intrinsic continuum, the residual flux of the C II λ1334 line correlates well with the escape fraction for directions with a dust-corrected residual flux larger than 30%. For other directions, the relations have a strong dispersion, and the residual flux overestimates the escape fraction for most cases. Concerning Lyβ, the residual flux after dust correction does not correlate with the escape fraction but can be used as a lower limit.

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“…Traditionally, ǫ ff is chosen to be a constant, close to 1 per cent, and star formation is allowed only in gas cells above a prescribed density threshold and below a prescribed temperature threshold. This is motivated by observations of inefficient star formation on galactic kpc scales (Bigiel et al 2008) as well as in Milky Way giant molecular clouds (GMCs) (Krumholz & Tan 2007) In this paper, we use a novel approach for which ǫ ff depends on the turbulent state of the gas following the so-called multifree-fall approach (Federrath & Klessen 2012;Semenov, Kravtsov & Gnedin 2016;Kretschmer & Teyssier 2020). Indeed, in a turbulent medium, like the interstellar medium (ISM), the gas density distribution is well described by a lognormal probability distribution function (PDF):…”

Section: Galaxy Formation Physicsmentioning

confidence: 99%

“…is the local virial number which can be interpreted as an estimator for the local stability, x is the cell size and σ is the turbulent 1D velocity dispersion which is computed by the subgrid scale (SGS) turbulent energy model (see Schmidt, Niemeyer & Hillebrandt 2006;Semenov et al 2016;Kretschmer & Teyssier 2020, for more details). As a consequence, the efficiency is not a constant anymore but a function of the state of the gas in a computational cell which is characterized through the local virial parameter α vir and the turbulent Mach number M. This model therefore has two star formation channels, either α vir < 1 where the whole cell is collapsing under gravity or if M is large, such that large density fluctuations caused by supersonic turbulence occur.…”

Section: Galaxy Formation Physicsmentioning

confidence: 99%

“…While strong feedback is a promising way to explain the low efficiency of galaxy and star formation, the same strong feedback can also destroy the thin galactic discs, leading to non-physical thick and turbulent discs at low redshifts (Governato et al 2007;Agertz et al 2011;Gibsonetal.2013;Stinson et al 2013b;Roškar et al 2014;Kretschmer & Teyssier 2020). Invoking strong feedback alone is therefore not sufficient.…”

Section: Introductionmentioning

confidence: 99%

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Rapid filamentary accretion as the origin of extended thin discs

Kretschmer

Agertz

Teyssier

2020

Monthly Notices of the Royal Astronomical Society

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Galactic outflows driven by stellar feedback are crucial for explaining the inefficiency of star formation in galaxies. Although strong feedback can promote the formation of galactic discs by limiting star formation at early times and removing low angular momentum gas, it is not understood how the same feedback can result in diverse objects such as elliptical galaxies or razor thin spiral galaxies. We investigate this problem using cosmological zoom-in simulations of two galaxies forming within 1012 M⊙ halos with almost identical mass accretion histories and halo spin parameters. However, the two resulting galaxies end up with very different bulge-to-disc ratios at z = 0. At z > 1.5, the two galaxies feature a surface density of star formation ΣSFR ≃ 10 M⊙ yr−1 kpc−2, leading to strong outflows. After the last starburst episode, both galaxies feature a dramatic gaseous disc growth from 1 kpc to 5 kpc during 1 Gyr, a decisive event we dub “the Grand Twirl”. After this event, the evolutionary tracks diverge strongly, with one galaxy ending up as a bulge-dominated galaxy, whereas the other ends up as a disc-dominated galaxy. The origins of this dichotomy are the angular momentum of the accreted gas, and whether it adds constructively to the initial disc angular momentum. The build-up of this extended disc leads to a rapid lowering of ΣSFR by over two orders of magnitude with ΣSFR ≲ 0.1 M⊙ yr−1 kpc−2, in remarkable agreement with what is derived from Milky Way stellar populations. As a consequence, supernovae explosions are spread out and cannot launch galactic outflows anymore, allowing for the persistence of a thin, gently star forming, extended disc.

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Forming early-type galaxies without AGN feedback: a combination of merger-driven outflows and inefficient star formation

Cited by 43 publications

References 104 publications

The elephant in the bathtub: when the physics of star formation regulate the baryon cycle of galaxies

The elephant in the bathtub: when the physics of star formation regulate the baryon cycle of galaxies

UV absorption lines and their potential for tracing the Lyman continuum escape fraction

Rapid filamentary accretion as the origin of extended thin discs

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