Observed galaxies with high stellar masses or in dense environments have low specific star formation rates, i.e. they are quenched. Based on cosmological hydrodynamic simulations that include a ...prescription where quenching occurs in regions dominated by hot (>105.4 K) gas, we argue that this hot gas quenching in haloes >1012 M⊙ drives both mass quenching (i.e. central quenching) and environment quenching (i.e. satellite quenching). These simulations reproduce a broad range of locally observed trends among quenching, halo mass, stellar mass, environment, and distance to halo centre. Mass quenching is independent of environment because ∼1012–1013 M⊙ ‘mass quenching haloes’ inhabit a large range of environments. On the other hand, environment quenching is independent of stellar mass because galaxies of all stellar masses may live in dense environments as satellites of groups and clusters. As in observations, the quenched fraction of satellites increases with halo mass and decreases with distance to the centre of the group or cluster. We investigate pre-processing in group haloes, ejected former satellites, and hot gas that extends beyond the virial radius. The agreement of our model with key observational trends suggests that hot gas in massive haloes plays a leading role in quenching low-redshift galaxies.
Abstract
We examine the cosmic growth of the red sequence in a cosmological hydrodynamic simulation that includes a heuristic prescription for quenching star formation that yields a realistic passive ...galaxy population today. In this prescription, haloes dominated by hot gas are continually heated to prevent their coronae from fuelling new star formation. Hot coronae primarily form in haloes above ∼1012 M⊙, so that galaxies with stellar masses ∼1010.5 M⊙ are the first to be quenched and move on to the red sequence at z > 2. The red sequence is concurrently populated at low masses by satellite galaxies in large haloes that are starved of new fuel, resulting in a dip in passive galaxy number densities around ∼1010 M⊙. Stellar mass growth continues for galaxies even after joining the red sequence, primarily through minor mergers with a typical mass ratio ∼1:5. For the most massive systems, the size growth implied by the distribution of merger mass ratios is typically approximately two times the corresponding mass growth, consistent with observations. This model reproduces mass-density and colour-density trends in the local Universe, with essentially no evolution to z = 1, with the hint that such relations may be washed out by z ∼ 2. Simulated galaxies are increasingly likely to be red at high masses or high local overdensities. In our model, the presence of surrounding hot gas drives the trends with both mass and environment.
ABSTRACT
We investigate the Baryonic Tully–Fisher relation (BTFR) in the $(100\, h^{-1}{\rm Mpc})^3$simba hydrodynamical galaxy formation simulation together with a higher resolution $(25\, ...h^{-1}{\rm Mpc})^3$simba run, for over 10 000 disc-dominated, H i-rich galaxies. We generate simulated galaxy rotation curves from the mass distribution, which we show yields similar results to using the gas rotational velocities. From this, we measure the galaxy rotation velocity Vcirc using four metrics: $V_{\rm max}, V_{\rm flat}, V_{2R_e},$ and Vpolyex. We compare the predicted BTFR to the SPARC observational sample and find broad agreement. In detail, however, simba is biased towards higher Vcirc by up to 0.1 dex. We find evidence for the flattening of the BTFR in Vcirc > 300 km s−1 galaxies, in agreement with recent observational findings. simba’s rotation curves are more peaked for lower mass galaxies, in contrast with observations, suggesting overly bulge-dominated dwarf galaxies in our sample. We investigate for residuals around the BTFR versus H i mass, stellar mass, gas fraction, and specific star formation rate, which provide testable predictions for upcoming BTFR surveys. simba’s BTFR shows sub-optimal resolution mass convergence, with the higher resolution run lowering V in better agreement with data.
Abstract Mid-infrared (mid-IR) observations are powerful in identifying heavily obscured active galactic nuclei (AGN) that have weak emission in other wavelengths. Data from the Mid-Infrared ...Instrument (MIRI) on board the James Webb Space Telescope provides an excellent opportunity to perform such studies. We take advantage of the MIRI imaging data from the Cosmic Evolution Early Release Science Survey to investigate the AGN population in the distant universe. We estimate the source properties of MIRI-selected objects by utilizing spectral energy distribution (SED) modeling, and classify them into star-forming galaxies (SFs), SF-AGN mixed objects, and AGN. The source numbers of these types are 433, 102, and 25, respectively, from four MIRI pointings covering ∼9 arcmin 2 . The sample spans a redshift range of ≈0–5. We derive the median SEDs for all three source types, respectively, and publicly release them. The median MIRI SED of AGN is similar to the typical SEDs of hot dust-obscured galaxies and Seyfert 2s, for which the mid-IR SEDs are dominated by emission from AGN-heated hot dust. Based on our SED-fit results, we estimate the black hole accretion density (BHAD; i.e., total BH growth rate per comoving volume) as a function of redshift. At z < 3, the resulting BHAD agrees with the X-ray measurements in general. At z > 3, we identify a total of 27 AGN and SF-AGN mixed objects, leading to that our high- z BHAD is substantially higher than the X-ray results (∼0.5 dex at z ≈ 3–5). This difference indicates MIRI can identify a large population of heavily obscured AGN missed by X-ray surveys at high redshifts.
We present the H I emission project within the MIGHTEE survey, currently being carried out with the newly commissioned MeerKAT radio telescope. This is one of the first deep, blind, medium-wide ...interferometric surveys for neutral hydrogen (H I ) ever undertaken, extending our knowledge of H I emission to z = 0.6. The science goals of this medium-deep, medium-wide survey are extensive, including the evolution of the neutral gas content of galaxies over the past 5 billion years. Simulations predict nearly 3000 galaxies over 0 < z < 0.4 will be detected directly in H I , with statistical detections extending to z = 0.6. The survey allows us to explore H I as a function of galaxy environment, with massive groups and galaxy clusters within the survey volume. Additionally, the area is large enough to contain as many as 50 local galaxies with H I mass < 10 8 M ⊙ , which allows us to study the low-mass galaxy population. The 20 deg 2 main survey area is centred on fields with exceptional multi-wavelength ancillary data, with photometry ranging from optical through far-infrared wavelengths, supplemented with multiple spectroscopic campaigns. We describe here the survey design and the key science goals. We also show first results from the Early Science observations, including kinematic modelling of individual sources, along with the redshift, H I , and stellar mass ranges of the sample to date.
Abstract
We use a suite of cosmological zoom galaxy formation simulations and dust radiative transfer calculations to explore the use of the monochromatic 850
μ
m luminosity (
L
ν
,850
) as a ...molecular gas mass (
M
mol
) estimator in galaxies between 0 <
z
< 9.5 for a broad range of masses. For our fiducial simulations, where we assume that the dust mass is linearly related to the metal mass, we find that empirical
L
ν
,850
–
M
mol
calibrations accurately recover the molecular gas mass of our model galaxies and that the
L
ν
,850
-dependent calibration is preferred. We argue that the major driver of scatter in the
L
ν
,850
–
M
mol
relation arises from variations in the molecular gas-to-dust mass ratio, rather than variations in the dust temperature, in agreement with the previous study of Liang et al. Emulating a realistic measurement strategy with ALMA observing bands that are dependent on the source redshift, we find that estimating
S
ν
,850
from continuum emission at a different frequency contributes 10%–20% scatter to the
L
ν
,850
–
M
mol
relation. This additional scatter arises from a combination of mismatches in assumed
T
dust
and
β
values, as well as the fact that the SEDs are not single-temperature blackbodies. However, this observationally induced scatter is a subdominant source of uncertainty. Finally, we explore the impact of a dust prescription in which the dust-to-metals ratio varies with metallicity. Though the resulting mean dust temperatures are ∼50% higher, the dust mass is significantly decreased for low-metallicity halos. As a result, the observationally calibrated
L
ν
,850
–
M
mol
relation holds for massive galaxies, independent of the dust model, but below
L
ν
,850
≲ 10
28
erg s
−1
(metallicities
) we expect that galaxies may deviate from literature observational calibrations by ≳0.5 dex.
We present measurements of the specific angular momentum content (j) of galaxies drawn from the Simba cosmological hydrodynamic simulations. For the stellar, Hi and baryonic matter components we ...demonstrate the existence of extremely tight relations between j and the mass contained within the radius at which the Hi mass surface density decreases to 1 M⊙ pc−2. These relations are broadly consistent with a variety of empirical measurements. We confirm the observational result that the scatter in the stellar j–M relation is driven largely by Hi content, and measure the dependence of its scatter on the deviations of galaxies from other important scaling relations. For a given stellar mass, Hi-rich/poor galaxies have more/less-than-average stellar specific angular momentum. A similar, yet weaker, correlation exists for Hi mass fraction. Overall, our results demonstrate the utility of the Simba simulations as a platform for understanding and contextualising the data and results from forthcoming large galaxy surveys.
A multi-scale modeling approach is formulated which combines the use of the discrete element method (DEM) and population balance model (PBM) to simulate the evolution of particle size distribution ...(PSD) in dry milling. As a major novelty, a pseudo-coupled DEM–non-linear PBM approach is proposed, in which the parameters of a non-linear PBM were calibrated using the DEM simulations of the microdynamic environment in a mill by using the DEM intermittently. To demonstrate the application of this approach, breakage dynamics of silica particles in a vibrating cylindrical vessel containing an alumina grinding ball was simulated numerically. DEM simulations were performed to obtain the collision frequency and impact energy spectra, calculate the first-order breakage rate parameters from short milling of mono-sized feeds, and calibrate the parameters of the effectiveness factor of the non-linear PBM. As another novelty, the form of the effectiveness factor chosen accounted for both acceleration effects and deceleration effects simultaneously, which have been observed in various experimental milling studies. By incorporating DEM input, the non-linear PBM with the effectiveness factor was used to simulate the evolution of the PSD. This study demonstrates that a non-linear PBM, whose parameters were calibrated using DEM at early milling times, could predict the PSD evolution during prolonged milling and potentially obviate the need for using computationally expensive DEM simulations for the whole milling duration.
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•Proposed a novel multi-scale DEM–non-linear PBM approach for simulating dry milling•Applied it to breakage of silica particles in a vibratory vessel with grinding ball•Predicted specific breakage rate using DEM microdynamic data at early milling time•Calibrated the non-linear PBM parameters using the microdynamic data from DEM•Simulated evolution of the particle size accurately, obviating frequent use of DEM
Massive galaxies today typically are not forming stars despite being surrounded by hot gaseous haloes with short central cooling times. This likely owes to some form of 'quenching feedback' such as ...merger-driven quasar activity or radio jets emerging from central black holes. Here we implement heuristic prescriptions for these phenomena on-the-fly within cosmological hydrodynamic simulations. We constrain them by comparing to observed luminosity functions and colour-magnitude diagrams from the SDSS. We find that quenching from mergers alone does not produce a realistic red sequence, because 1-2 Gyr after a merger the remnant accretes new fuel and star formation re-ignites. In contrast, quenching by continuously adding thermal energy to hot gaseous haloes quantitatively matches the red galaxy luminosity function and produces a reasonable red sequence. Small discrepancies remain - a shallow red-sequence slope suggests that our models underestimate metal production or retention in massive red galaxies, while a deficit of massive blue galaxies may reflect the fact that observed heating is intermittent rather than continuous. Overall, injection of energy into hot halo gas appears to be a necessary and sufficient condition to broadly produce red and dead massive galaxies as observed.
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