We investigate the evolution of the galaxy star formation rate function (SFRF) and cosmic star formation rate density (CSFRD) of z ~ 1-4 galaxies, using cosmological smoothed particle hydrodynamic ...(SPH) simulations and a compilation of ultraviolet (UV), infrared (IR) and Ha observations. These tracers represent different populations of galaxies with the IR light being a probe of objects with high star formation rates and dust contents, while UV and Ha observations provide a census of low star formation galaxies where mild obscuration occurs. We compare the above SFRFs with the results of SPH simulations run with the code P-GADGET3(XXL). We focus on the role of feedback from active galactic nuclei (AGN) and supernovae in form of galactic winds. The AGN feedback prescription that we use decreases the simulated CSFRD at z < 3 but is not sufficient to reproduce the observed evolution at higher redshifts. We explore different wind models and find that the key factor for reproducing the evolution of the observed SFRF and CSFRD at z ~ 1-4 is the presence of a feedback prescription that is prominent at high redshifts (z greater than or equal to 4) and becomes less efficient with time. We show that variable galactic winds which are efficient at decreasing the SFRs of low-mass objects are quite successful in reproducing the observables.
ABSTRACT
There is a severe tension between the observed star formation rate (SFR)–stellar mass (M⋆) relations reported by different authors at z = 1–4. In addition, the observations have not been ...successfully reproduced by state-of-the-art cosmological simulations that tend to predict a factor of 2–4 smaller SFRs at a fixed M⋆. We examine the evolution of the SFR–M⋆ relation of z = 1–4 galaxies using the skirt simulated spectral energy distributions of galaxies sampled from the Evolution and Assembly of GaLaxies and their Environments simulations. We derive SFRs and stellar masses by mimicking different observational techniques. We find that the tension between observed and simulated SFR–M⋆ relations is largely alleviated if similar methods are used to infer the galaxy properties. We find that relations relying on infrared wavelengths (e.g. 24 ${\rm \, \mu m}$, MIPS – 24, 70, and 160 ${\rm \, \mu m}$ or SPIRE – 250, 350, and 500 ${\rm \, \mu m}$) have SFRs that exceed the intrinsic relation by 0.5 dex. Relations that rely on the spectral energy distribution fitting technique underpredict the SFRs at a fixed stellar mass by −0.5 dex at z ∼ 4 but overpredict the measurements by 0.3 dex at z ∼ 1. Relations relying on dust-corrected rest-frame ultraviolet luminosities, are flatter since they overpredict/underpredict SFRs for low/high star-forming objects and yield deviations from the intrinsic relation from 0.10 to −0.13 dex at z ∼ 4. We suggest that the severe tension between different observational studies can be broadly explained by the fact that different groups employ different techniques to infer their SFRs.
ABSTRACT
We present spatially resolved Echelle spectroscopy of an intervening Mg ii–Fe ii–Mg i absorption-line system detected at zabs = 0.73379 towards the giant gravitational arc PSZ1 ...G311.65–18.48. The absorbing gas is associated with an inclined disc-like star-forming galaxy, whose major axis is aligned with the two arc-segments reported here. We probe in absorption the galaxy’s extended disc continuously, at ≈3 kpc sampling, from its inner region out to 15× the optical radius. We detect strong ($W_0^{2796}\gt 0.3$Å) coherent absorption along 13 independent positions at impact parameters D = 0–29 kpc on one side of the galaxy, and no absorption at D = 28–57 kpc on the opposite side (all de-lensed distances at zabs). We show that (1) the gas distribution is anisotropic; (2) $W_0^{2796}$, $W_0^{2600}$, $W_0^{2852}$, and the ratio $W_0^{2600}\!/W_0^{2796}$, all anticorrelate with D; (3) the $W_0^{2796}$–D relation is not cuspy and exhibits significantly less scatter than the quasar-absorber statistics; (4) the absorbing gas is co-rotating with the galaxy out to D ≲ 20 kpc, resembling a ‘flat’ rotation curve, but at D ≳ 20 kpc velocities decline below the expectations from a 3D disc-model extrapolated from the nebular O ii emission. These signatures constitute unambiguous evidence for rotating extra-planar diffuse gas, possibly also undergoing enriched accretion at its edge. Arguably, we are witnessing some of the long-sought processes of the baryon cycle in a single distant galaxy expected to be representative of such phenomena.
ABSTRACT
We present gravitational-arc tomography of the cool-warm enriched circumgalactic medium (CGM) of an isolated galaxy (‘G1’) at z ≈ 0.77. Combining VLT/MUSE adaptive-optics and Magellan/MagE ...echelle spectroscopy, we obtain partially resolved kinematics of Mg ii in absorption and O ii in emission. The unique arc configuration allows us to probe 42 spatially independent arc positions transverse to G1, plus four positions in front of it. The transverse positions cover G1’s minor and major axes at impact parameters of ≈10–30 and ≈60 kpc, respectively. We observe a direct kinematic connection between the cool-warm enriched CGM (traced by Mg ii) and the interstellar medium (traced by O ii). This provides strong evidence for the existence of an extended disc that co-rotates with the galaxy out to tens of kiloparsecs. The Mg ii velocity dispersion (σ ≈ 30–100 km s−1, depending on position) is of the same order as the modelled galaxy rotational velocity (vrot ≈ 80 km s−1), providing evidence for the presence of a turbulent and pressure-supported CGM component. We regard the absorption to be modulated by a galactic-scale outflow, as it offers a natural scenario for the observed line-of-sight dispersion and asymmetric profiles observed against both the arcs and the galaxy. An extended enriched co-rotating disc together with the signatures of a galactic outflow, are telltale signs of metal recycling in the z ∼ 1 CGM.
We study the role of feedback from supernovae (SN) and black holes in the evolution of the star formation rate function (SFRF) of z ∼ 4-7 galaxies. We use a new set of cosmological hydrodynamic ...simulations, Angus (AustraliaN
GADGET-3
early Universe Simulations), run with a modified and improved version of the parallel TreePM-smoothed particle hydrodynamics code GADGET-3 called P-GADGET3(XXL), that includes a self-consistent implementation of stellar evolution and metal enrichment. In our simulations both SN-driven galactic winds and active galactic nuclei (AGN) act simultaneously in a complex interplay. The SFRF is insensitive to feedback prescription at z > 5, meaning that it cannot be used to discriminate between feedback models during reionization. However, the SFRF is sensitive to the details of feedback prescription at lower redshift. By exploring different SN-driven wind velocities and regimes for the AGN feedback, we find that the key factor for reproducing the observed SFRFs is a combination of 'strong' SN winds and early AGN feedback in low-mass galaxies. Conversely, we show that the choice of initial mass function and inclusion of metal cooling have less impact on the evolution of the SFRF. When variable winds are considered, we find that a non-aggressive wind scaling is needed to reproduce the SFRFs at z 4. Otherwise, the amount of objects with low SFRs is greatly suppressed and at the same time winds are not effective enough in the most massive systems.
ABSTRACT
We use spatially resolved spectroscopy of a distant giant gravitational arc to test orientation effects on Mg ii absorption equivalent width (EW) and covering fraction (〈κ〉) in the ...circumgalactic medium of a foreground star-forming galaxy (G1) at z ∼ 0.77. Forty-two spatially-binned arc positions uniformly sample impact parameters (D) to G1 between 10 and 30 kpc and azimuthal angles α between 30° and 90° (minor axis). We find an EW-D anticorrelation, akin to that observed statistically in quasar absorber studies, and an apparent correlation of both EW and 〈κ〉 with α, revealing a non-isotropic gas distribution. In line with our previous results on Mg ii kinematics suggesting the presence of outflows in G1, at minimum a simple 3D static double-cone model (to represent the trace of bipolar outflows) is required to recreate the EW spatial distribution. The D and α values probed by the arc cannot confirm the presence of a disc, but the data highly disfavour a disc alone. Our results support the interpretation that the EW-α correlation observed statistically using other extant probes is partly shaped by bipolar metal-rich winds.
We present spatially resolved Echelle spectroscopy of an intervening Mg II–Fe II–Mg I absorption-line system detected at zabs = 0.73379 towards the giant gravitational arc PSZ1 G311.65–18.48. The ...absorbing gas is associated with an inclined disc-like star-forming galaxy, whose major axis is aligned with the two arc-segments reported here. We probe in absorption the galaxy’s extended disc continuously, at ≈3 kpc sampling, from its inner region out to 15× the optical radius. We detect strong (W27960>0.3Å) coherent absorption along 13 independent positions at impact parameters D = 0–29 kpc on one side of the galaxy, and no absorption at D = 28–57 kpc on the opposite side (all de-lensed distances at zabs). We show that (1) the gas distribution is anisotropic; (2) W27960, W26000, W28520, and the ratio W26000/W27960, all anticorrelate with D; (3) the W27960–D relation is not cuspy and exhibits significantly less scatter than the quasar-absorber statistics; (4) the absorbing gas is co-rotating with the galaxy out to D ≲ 20 kpc, resembling a ‘flat’ rotation curve, but at D ≳ 20 kpc velocities decline below the expectations from a 3D disc-model extrapolated from the nebular O II emission. These signatures constitute unambiguous evidence for rotating extra-planar diffuse gas, possibly also undergoing enriched accretion at its edge. Arguably, we are witnessing some of the long-sought processes of the baryon cycle in a single distant galaxy expected to be representative of such phenomena.
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