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

2020 ◽  
Vol 500 (2) ◽  
pp. 2000-2011
Author(s):  
Jindra Gensior ◽  
J M Diederik Kruijssen
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Galaxy Formation ◽  
High Redshift ◽  
Formation Rate ◽  
Cosmic Time ◽  
Free Fall ◽  
Isolated Galaxies ◽  
The Galaxy ◽  
Galaxy Masses

ABSTRACT 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 hypothesized 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.

scholarly journals Quasi-equilibrium models of high-redshift disc galaxy evolution

2020 ◽  
Vol 500 (3) ◽  
pp. 3394-3412
Author(s):  
Steven R Furlanetto
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Galaxy Formation ◽  
High Redshift ◽  
Formation Rate ◽  
New Physics ◽  
Small Scale ◽  
Quasi Equilibrium ◽  
Mass Relation ◽  
Disc Galaxy

ABSTRACT In recent years, simple models of galaxy formation have been shown to provide reasonably good matches to available data on high-redshift luminosity functions. However, these prescriptions are primarily phenomenological, with only crude connections to the physics of galaxy evolution. Here, we introduce a set of galaxy models that are based on a simple physical framework but incorporate more sophisticated models of feedback, star formation, and other processes. We apply these models to the high-redshift regime, showing that most of the generic predictions of the simplest models remain valid. In particular, the stellar mass–halo mass relation depends almost entirely on the physics of feedback (and is thus independent of the details of small-scale star formation) and the specific star formation rate is a simple multiple of the cosmological accretion rate. We also show that, in contrast, the galaxy’s gas mass is sensitive to the physics of star formation, although the inclusion of feedback-driven star formation laws significantly changes the naive expectations. While these models are far from detailed enough to describe every aspect of galaxy formation, they inform our understanding of galaxy formation by illustrating several generic aspects of that process, and they provide a physically grounded basis for extrapolating predictions to faint galaxies and high redshifts currently out of reach of observations. If observations show violations from these simple trends, they would indicate new physics occurring inside the earliest generations of galaxies.

scholarly journals Fast molecular outflow from a dusty star-forming galaxy in the early Universe

Science ◽  
2018 ◽  
Vol 361 (6406) ◽  
pp. 1016-1019 ◽  
Author(s):  
J. S. Spilker ◽  
M. Aravena ◽  
M. Béthermin ◽  
S. C. Chapman ◽  
C.-C. Chen ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Large Fraction ◽  
Formation Rate ◽  
Free Fall ◽  
Big Bang ◽  
Star Forming ◽  
Molecular Outflow ◽  
The Galaxy ◽  
The Big Bang

Galaxies grow inefficiently, with only a small percentage of the available gas converted into stars each free-fall time. Feedback processes, such as outflowing winds driven by radiation pressure, supernovae, or supermassive black hole accretion, can act to halt star formation if they heat or expel the gas supply. We report a molecular outflow launched from a dust-rich star-forming galaxy at redshift 5.3, 1 billion years after the Big Bang. The outflow reaches velocities up to 800 kilometers per second relative to the galaxy, is resolved into multiple clumps, and carries mass at a rate within a factor of 2 of the star formation rate. Our results show that molecular outflows can remove a large fraction of the gas available for star formation from galaxies at high redshift.

scholarly journals Quenching and morphological evolution due to circumgalactic gas expulsion in a simulated galaxy with a controlled assembly history

2020 ◽  
Vol 501 (1) ◽  
pp. 236-253
Author(s):  
Jonathan J Davies ◽  
Robert A Crain ◽  
Andrew Pontzen
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Galaxy Evolution ◽  
Galaxy Formation ◽  
Morphological Evolution ◽  
Formation Rate ◽  
Random Number Generator ◽  
Dark Matter Halo ◽  
Close Coupling ◽  
The Galaxy

ABSTRACT We examine the influence of dark matter halo assembly on the evolution of a simulated ∼L⋆ galaxy. Starting from a zoom-in simulation of a star-forming galaxy evolved with the EAGLE galaxy formation model, we use the genetic modification technique to create a pair of complementary assembly histories: one in which the halo assembles later than in the unmodified case, and one in which it assembles earlier. Delayed assembly leads to the galaxy exhibiting a greater present-day star formation rate than its unmodified counterpart, while in the accelerated case the galaxy quenches at z ≃ 1, and becomes spheroidal. We simulate each assembly history nine times, adopting different seeds for the random number generator used by EAGLE’s stochastic subgrid implementations of star formation and feedback. The systematic changes driven by differences in assembly history are significantly stronger than the random scatter induced by this stochasticity. The sensitivity of ∼L⋆ galaxy evolution to dark matter halo assembly follows from the close coupling of the growth histories of the central black hole (BH) and the halo, such that earlier assembly fosters the formation of a more massive BH, and more efficient expulsion of circumgalactic gas. In response to this expulsion, the circumgalactic medium reconfigures at a lower density, extending its cooling time and thus inhibiting the replenishment of the interstellar medium. Our results indicate that halo assembly history significantly influences the evolution of ∼L⋆ central galaxies, and that the expulsion of circumgalactic gas is a crucial step in quenching them.

scholarly journals First Light And Reionization Epoch Simulations (FLARES) – I. Environmental dependence of high-redshift galaxy evolution

2020 ◽  
Vol 500 (2) ◽  
pp. 2127-2145
Author(s):  
Christopher C Lovell ◽  
Aswin P Vijayan ◽  
Peter A Thomas ◽  
Stephen M Wilkins ◽  
David J Barnes ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Galaxy Formation ◽  
Dynamic Range ◽  
High Redshift ◽  
Formation Rate ◽  
Mass Function ◽  
Distribution Functions ◽  
Large Area ◽  
Composite Distribution ◽  
Environmental Dependence

ABSTRACT We introduce the First Light And Reionisation Epoch Simulations (FLARES), a suite of zoom simulations using the EAGLE model. We resimulate a range of overdensities during the Epoch of Reionization (EoR) in order to build composite distribution functions, as well as explore the environmental dependence of galaxy formation and evolution during this critical period of galaxy assembly. The regions are selected from a large $(3.2 \, \mathrm{cGpc})^{3}$ parent volume, based on their overdensity within a sphere of radius 14 h−1 cMpc. We then resimulate with full hydrodynamics, and employ a novel weighting scheme that allows the construction of composite distribution functions that are representative of the full parent volume. This significantly extends the dynamic range compared to smaller volume periodic simulations. We present an analysis of the galaxy stellar mass function (GSMF), the star formation rate distribution function (SFRF), and the star-forming sequence (SFS) predicted by FLARES, and compare to a number of observational and model constraints. We also analyse the environmental dependence over an unprecedented range of overdensity. Both the GSMF and the SFRF exhibit a clear double-Schechter form, up to the highest redshifts (z = 10). We also find no environmental dependence of the SFS normalization. The increased dynamic range probed by FLARES will allow us to make predictions for a number of large area surveys that will probe the EoR in coming years, carried out on new observatories such as Roman and Euclid.

Extreme variations in star formation activity in the first galaxies

2019 ◽  
Vol 15 (S341) ◽  
pp. 226-230
Author(s):  
Christian Binggeli ◽  
Erik Zackrisson ◽  
Xiangcheng Ma ◽  
Akio K. Inoue ◽  
Anton Vikaeus ◽  
...  
Keyword(s):  
Star Formation ◽  
Rest Frame ◽  
High Redshift ◽  
Formation Rate ◽  
High Redshift Galaxies ◽  
James Webb Space Telescope ◽  
Star Formation Activity ◽  
The Galaxy ◽  
First Galaxies ◽  
Star Formation Histories

AbstractRecently, spectroscopic detections of O[III] 88 μm and Ly-α emission lines from the z ≍ 9.1 galaxy MACS1149-JD1 have been presented, and with these, some interesting properties of this galaxy were uncovered. One such property is that MACS1149-JD1 exhibits a significant Balmer break at around rest-frame 4000 Å, which may indicate that the galaxy has experienced large variations in star formation rate prior to z ∼ 9, with a rather long period of low star formation activity. While some simulations predict large variations in star formation activity in high-redshift galaxies, it is unclear whether the simulations can reproduce the kind of variations seen in MACS1149-JD1. Here, we utilize synthetic spectra of simulated galaxies from two simulation suites in order to study to what extent these can accurately reproduce the spectral features (specifically the Balmer break) observed in MACS1149-JD1. We show that while the simulations used in this study produce galaxies with varying star formation histories, galaxies such as MACS1149-JD1 would be very rare in the simulations. In principle, future observations with the James Webb Space Telescope may tell us if MACS1149-JD1 represents something rare, or if such galaxies are more common than predicted by current simulations.

scholarly journals Heart of darkness: the influence of galactic dynamics on quenching star formation in galaxy spheroids

2020 ◽  
Vol 495 (1) ◽  
pp. 199-223 ◽  
Author(s):  
Jindra Gensior ◽  
J M Diederik Kruijssen ◽  
Benjamin W Keller
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Formation Rate ◽  
Free Fall ◽  
Galactic Centre ◽  
Causal Connection ◽  
Isolated Galaxies ◽  
Stellar Halo ◽  
Hydrodynamical Simulations ◽  
The Impact

ABSTRACT Quenched galaxies are often observed to contain a strong bulge component. The key question is whether this reflects a causal connection – can star formation be quenched dynamically by bulges or the spheroids of early-type galaxies? We systematically investigate the impact of these morphological components on star formation, by performing a suite of hydrodynamical simulations of isolated galaxies containing a spheroid. We vary the bulge mass and scale radius, while the total initial stellar, halo, and gas mass are kept constant, with a gas fraction of 5 per cent. In addition, we consider two different sub-grid star formation prescriptions. The first follows most simulations in the literature by assuming a constant star formation efficiency per free-fall time, whereas in the second model it depends on the gas virial parameter, following high-resolution simulations of turbulent fragmentation. Across all simulations, central spheroids increase the gas velocity dispersion towards the galactic centre. This increases the gravitational stability of the gas disc, suppresses fragmentation and star formation, and results in galaxies hosting extremely smooth and quiescent gas discs that fall below the galaxy main sequence. These effects amplify when using the more sophisticated, dynamics-dependent star formation model. Finally, we discover a pronounced relation between the central stellar surface density and star formation rate (SFR), such that the most bulge-dominated galaxies show the strongest deviation from the main sequence. We conclude that the SFR of galaxies is not only set by the balance between accretion and feedback, but carries a (sometimes dominant) dependence on the gravitational potential.

scholarly journals Cooling flow solutions for the circumgalactic medium

2019 ◽  
Vol 488 (2) ◽  
pp. 2549-2572 ◽  
Author(s):  
Jonathan Stern ◽  
Drummond Fielding ◽  
Claude-André Faucher-Giguère ◽  
Eliot Quataert
Keyword(s):  
Galaxy Formation ◽  
Milky Way ◽  
High Redshift ◽  
Formation Rate ◽  
Free Fall ◽  
Cooling Time ◽  
Cooling Flow ◽  
Similar Solutions ◽  
Cooling Function ◽  
Milky Way Halo

ABSTRACT In several models of galaxy formation feedback occurs in cycles or mainly at high redshift. At times and in regions where feedback heating is ineffective, hot gas in the galaxy halo is expected to form a cooling flow, where the gas advects inward on a cooling timescale. Cooling flow solutions can thus be used as a benchmark for observations and simulations to constrain the timing and extent of feedback heating. Using analytic calculations and idealized 3D hydrodynamic simulations, we show that for a given halo mass and cooling function, steady-state cooling flows form a single-parameter family of solutions, while initially hydrostatic gaseous haloes converge on one of these solutions within a cooling time. The solution is thus fully determined once either the mass inflow rate ${\dot{M}}$ or the total halo gas mass are known. In the Milky Way halo, a cooling flow with ${\dot{M}}$ equal to the star formation rate predicts a ratio of the cooling time to the free-fall time of ∼10, similar to some feedback-regulated models. This solution also correctly predicts observed $\rm{O\,{\small VII}}$ and $\rm{O\,{\small VIII}}$ absorption columns, and the gas density profile implied by $\rm{O\,{\small VII}}$ and $\rm{O\,{\small VIII}}$ emission. These results suggest ongoing heating by feedback may be negligible in the inner Milky-Way halo. Extending similar solutions out to the cooling radius however underpredicts observed $\rm{O\,{\small VI}}$ columns around the Milky-Way and around other low-redshift star-forming galaxies. This can be reconciled with the successes of the cooling flow model with either a mechanism which preferentially heats the $\rm{O\,{\small VI}}$-bearing outer halo, or alternatively if $\rm{O\,{\small VI}}$ traces cool photoionized gas beyond the accretion shock. We also demonstrate that the entropy profiles of some of the most relaxed clusters are reasonably well described by a cooling flow solution.

scholarly journals Prospects for distinguishing galaxy evolution models with surveys at redshifts z ≳ 4

2020 ◽  
Vol 499 (3) ◽  
pp. 4534-4544 ◽  
Author(s):  
Jordan Mirocha
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Galaxy Formation ◽  
Duty Cycle ◽  
Cosmic Time ◽  
Galaxy Surveys ◽  
Stellar Feedback ◽  
Luminosity Functions ◽  
Galaxy Bias ◽  
The Masses

ABSTRACT Many semi-empirical galaxy formation models have recently emerged to interpret high-z galaxy luminosity functions and make predictions for future galaxy surveys. A common approach assumes a ‘universal’ star formation efficiency, f*, independent of cosmic time but strongly dependent on the masses of dark matter haloes. Though this class of models has been very successful in matching observations over much of cosmic history, simple stellar feedback models do predict redshift evolution in f* and are commonly used in semi-analytic models. In this work, we calibrate a set of universal f* and feedback-regulated models to the same set of rest-ultraviolet z ≳ 4 observations and find that a rapid, ∼(1 + z)−3/2 decline in both the efficiency of dust production and duty cycle of star formation are needed to reconcile feedback-regulated models with current observations. By construction, these models remain nearly identical to universal f* models in rest-ultraviolet luminosity functions (UVLFs) and colours. As a result, the only way to distinguish these competing scenarios is either via (i) improved constraints on the clustering of galaxies – universal and feedback-regulated models differ in predictions for the galaxy bias by 0.1 ≲ Δ〈b〉 ≲ 0.3 over 4 ≲ z ≲ 10 – or (ii) independent constraints on the dust contents and/or duty cycle of star formation. This suggests that improved constraints on the ‘dustiness’ and ‘burstiness’ of high-z galaxies will not merely add clarity to a given model of star formation in high-z galaxies, but rather fundamentally determine our ability to identify the correct model in the first place.

scholarly journals Simulating JWST deep extragalactic imaging surveys and physical parameter recovery

2020 ◽  
Vol 640 ◽  
pp. A67
Author(s):  
O. B. Kauffmann ◽  
O. Le Fèvre ◽  
O. Ilbert ◽  
J. Chevallard ◽  
C. C. Williams ◽  
...  
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
High Redshift ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Spectral Energy ◽  
Photometric Redshifts ◽  
The Galaxy ◽  
Stellar Masses ◽  
The Impact

We present a new prospective analysis of deep multi-band imaging with the James Webb Space Telescope (JWST). In this work, we investigate the recovery of high-redshift 5 <  z <  12 galaxies through extensive image simulations of accepted JWST programs, including the Early Release Science in the EGS field and the Guaranteed Time Observations in the HUDF. We introduced complete samples of ∼300 000 galaxies with stellar masses of log(M*/M⊙) > 6 and redshifts of 0 <  z <  15, as well as galactic stars, into realistic mock NIRCam, MIRI, and HST images to properly describe the impact of source blending. We extracted the photometry of the detected sources, as in real images, and estimated the physical properties of galaxies through spectral energy distribution fitting. We find that the photometric redshifts are primarily limited by the availability of blue-band and near-infrared medium-band imaging. The stellar masses and star formation rates are recovered within 0.25 and 0.3 dex, respectively, for galaxies with accurate photometric redshifts. Brown dwarfs contaminating the z >  5 galaxy samples can be reduced to < 0.01 arcmin−2 with a limited impact on galaxy completeness. We investigate multiple high-redshift galaxy selection techniques and find that the best compromise between completeness and purity at 5 <  z <  10 using the full redshift posterior probability distributions. In the EGS field, the galaxy completeness remains higher than 50% at magnitudes mUV <  27.5 and at all redshifts, and the purity is maintained above 80 and 60% at z ≤ 7 and 10, respectively. The faint-end slope of the galaxy UV luminosity function is recovered with a precision of 0.1–0.25, and the cosmic star formation rate density within 0.1 dex. We argue in favor of additional observing programs covering larger areas to better constrain the bright end.

scholarly journals Physics of a clumpy lensed galaxy at z = 1.6

2018 ◽  
Vol 619 ◽  
pp. A15 ◽  
Author(s):  
M. Girard ◽  
M. Dessauges-Zavadsky ◽  
D. Schaerer ◽  
J. Richard ◽  
K. Nakajima ◽  
...  
Keyword(s):  
Star Formation ◽  
Gravitational Lensing ◽  
Near Infrared ◽  
High Redshift ◽  
Formation Rate ◽  
Far Infrared ◽  
Rotating Disk ◽  
Cluster Galaxy ◽  
Star Forming ◽  
The Galaxy

Observations have shown that massive star-forming clumps are present in the internal structure of high-redshift galaxies. One way to study these clumps in detail with a higher spatial resolution is by exploiting the power of strong gravitational lensing which stretches images on the sky. In this work, we present an analysis of the clumpy galaxy A68-HLS115 at z = 1.5858, located behind the cluster Abell 68, but strongly lensed by a cluster galaxy member. Resolved observations with SINFONI/VLT in the near-infrared (NIR) show Hα, Hβ, [NII], and [OIII] emission lines. Combined with images covering the B band to the far-infrared (FIR) and CO(2–1) observations, this makes this galaxy one of the only sources for which such multi-band observations are available and for which it is possible to study the properties of resolved star-forming clumps and to perform a detailed analysis of the integrated properties, kinematics, and metallicity. We obtain a stability of υrot/σ0 = 2.73 by modeling the kinematics, which means that the galaxy is dominated by rotation, but this ratio also indicates that the disk is marginally stable. We find a high intrinsic velocity dispersion of 80 ± 10 km s−1 that could be explained by the high gas fraction of fgas = 0.75 ± 0.15 observed in this galaxy. This high fgas and the observed sSFR of 3.12 Gyr−1 suggest that the disk turbulence and instabilities are mostly regulated by incoming gas (available gas reservoir for star formation). The direct measure of the Toomre stability criterion of Qcrit = 0.70 could also indicate the presence of a quasi-stable thick disk. Finally, we identify three clumps in the Hα map which have similar velocity dispersions, metallicities, and seem to be embedded in the rotating disk. These three clumps contribute together to ∼40% on the SFRHα of the galaxy and show a star formation rate density about ∼100 times higher than HII regions in the local Universe.

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