scholarly journals Submillimetre galaxies in cosmological hydrodynamical simulations – an opportunity for constraining feedback models

2021 ◽  
Vol 502 (2) ◽  
pp. 2922-2933
Author(s):  
Christopher C Hayward ◽  
Martin Sparre ◽  
Scott C Chapman ◽  
Lars Hernquist ◽  
Dylan Nelson ◽  
...  
Keyword(s):  
Large Volume ◽  
High Mass ◽  
Scaling Relation ◽  
Redshift Distribution ◽  
Cosmological Simulations ◽  
Hydrodynamical Simulation ◽  
Hydrodynamical Simulations ◽  
Post Hoc ◽  
Number Counts ◽  
Lower Redshift

ABSTRACT Submillimetre galaxies (SMGs) have long posed a challenge for theorists, and self-consistently reproducing the properties of the SMG population in a large-volume cosmological hydrodynamical simulation has not yet been achieved. We use a scaling relation derived from previous simulations plus radiative transfer calculations to predict the submm flux densities of simulated SMGs drawn from cosmological simulations from the Illustris and IllustrisTNG projects based on the simulated galaxies’ star formation rates (SFRs) and dust masses, and compare the predicted number counts with observations. We find that the predicted SMG number counts based on IllustrisTNG are significantly less than observed (more than 1 dex at S850 ≳ 4 mJy). The simulation from the original Illustris project yields more SMGs than IllustrisTNG: the predicted counts are consistent with those observed at both S850 ≲ 5 mJy and S850 ≳ 9 mJy and only a factor of ∼2 lower than those observed at intermediate flux densities. The redshift distribution of SMGs with S850 > 3 mJy in IllustrisTNG is consistent with the observed distribution, whereas the Illustris redshift distribution peaks at significantly lower redshift (1.5 versus 2.8). We demonstrate that IllustrisTNG hosts fewer SMGs than Illustris because in the former, high-mass ($M_{\star }\sim 10^{11} \, \text{M}_{\odot }$) z ∼ 2–3 galaxies have lower dust masses and SFRs than in Illustris owing to differences in the subgrid models for stellar and/or active galactic nucleus feedback between the two simulations (we unfortunately cannot isolate the specific cause(s) post hoc). Our results demonstrate that because our method enables predicting SMG number counts in post-processing with a negligible computational expense, SMGs can provide useful constraints for tuning subgrid models in future large-volume cosmological simulations.

scholarly journals The anisotropy of the power spectrum in periodic cosmological simulations

2021 ◽  
Vol 503 (4) ◽  
pp. 5638-5645
Author(s):  
Gábor Rácz ◽  
István Szapudi ◽  
István Csabai ◽  
László Dobos
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Initial Conditions ◽  
Power Spectra ◽  
Cosmological Simulations ◽  
Spherical Collapse ◽  
Lower Amplitude ◽  
Hydrodynamical Simulations

ABSTRACT The classical gravitational force on a torus is anisotropic and always lower than Newton’s 1/r2 law. We demonstrate the effects of periodicity in dark matter only N-body simulations of spherical collapse and standard Lambda cold dark matter (ΛCDM) initial conditions. Periodic boundary conditions cause an overall negative and anisotropic bias in cosmological simulations of cosmic structure formation. The lower amplitude of power spectra of small periodic simulations is a consequence of the missing large-scale modes and the equally important smaller periodic forces. The effect is most significant when the largest mildly non-linear scales are comparable to the linear size of the simulation box, as often is the case for high-resolution hydrodynamical simulations. Spherical collapse morphs into a shape similar to an octahedron. The anisotropic growth distorts the large-scale ΛCDM dark matter structures. We introduce the direction-dependent power spectrum invariant under the octahedral group of the simulation volume and show that the results break spherical symmetry.

scholarly journals Counts of quasars at faint magnitudes: a new complete sample

1986 ◽  
Vol 119 ◽  
pp. 33-36
Author(s):  
G. Zamorani ◽  
V. Zitelli ◽  
B. Marano
Keyword(s):  
The Other ◽  
Search Technique ◽  
Complete Sample ◽  
Redshift Distribution ◽  
Redshift Range ◽  
Color Selection ◽  
Integral Number ◽  
Other Hand ◽  
Luminosity Functions ◽  
Number Counts

We present results on a new sample of optically selected quasar candidates. The “standard” multicolor technique for selecting quasar candidates has been applied to all the objects brighter than J = 22.0 in a field of 0.69 square degrees. Additional candidates have been selected from a search on grism plates obtained in the same area. Spectroscopy for all the candidates brighter than J = 20.9 has provided a sample of 22 confirmed quasars. The redshift distribution of these objects is essentially flat from z = 0.6 up to z = 2.8. Three out of the eight quasars with redshift larger than two were selected from the grism plates and were missed by our color selection. This result, although based on a small number of objects, suggests that the luminosity functions computed in this redshift range from samples which are only color selected might have to be increased by a factor up to 1.5. On the other hand, these possible losses of the multicolor search technique are negligible (of the order of 15% only) for the estimates of the integral number counts at magnitudes of the order 20–21.

scholarly journals Galactic ionizing photon budget during the epoch of reionization in the Cosmic Dawn II simulation

2020 ◽  
Vol 496 (4) ◽  
pp. 4342-4357 ◽  
Author(s):  
Joseph S W Lewis ◽  
Pierre Ocvirk ◽  
Dominique Aubert ◽  
Jenny G Sorce ◽  
Paul R Shapiro ◽  
...  
Keyword(s):  
Formation Rate ◽  
Mass Range ◽  
Mass Function ◽  
High Mass ◽  
Relative Contribution ◽  
Fully Coupled ◽  
The Universe ◽  
Lower Redshift ◽  
Galactic Haloes

ABSTRACT Cosmic Dawn II yields the first statistically meaningful determination of the relative contribution to reionization by galaxies of different halo mass, from a fully coupled radiation-hydrodynamics simulation of the epoch of reionization large enough (∼100 Mpc) to model global reionization while resolving the formation of all galactic haloes above ${\sim}10^8 \, {\rm M}_{\odot }$. Cell transmission inside haloes is bi-modal – ionized cells are transparent, while neutral cells absorb the photons their stars produce – and the halo escape fraction fesc reflects the balance of star formation rate (SFR) between these modes. The latter is increasingly prevalent at higher halo mass, driving down fesc (we provide analytical fits to our results), whereas halo escape luminosity, proportional to fesc × SFR, increases with mass. Haloes with dark matter masses within $6\times 10^{8} \, {\rm M}_{\odot }\lt M_{\rm halo}\lt 3 \times 10^{10} \, {\rm M}_{\odot }$ produce ∼80 per cent of the escaping photons at z = 7, when the universe is 50 per cent ionized, making them the main drivers of cosmic reionization. Less massive haloes, though more numerous, have low SFRs and contribute less than 10 per cent of the photon budget then, despite their high fesc. High-mass haloes are too few and too opaque, contributing <10 per cent despite their high SFRs. The dominant mass range is lower (higher) at higher (lower) redshift, as mass function and reionization advance together (e.g. at z = 8.5, xH i = 0.9, $M_{\rm halo}\lt 5\times 10^9 \, {\rm M}_{\odot }$ haloes contributed ∼80 per cent). Galaxies with UV magnitudes MAB1600 between −12 and −19 dominated reionization between z = 6 and 8.

scholarly journals V471 Tauri and SuWt 2: The Exotic Descendants of Triple Systems?

2002 ◽  
Vol 187 ◽  
pp. 239-243 ◽  
Author(s):  
Howard E. Bond ◽  
M. Sean O’Brien ◽  
Edward M. Sion ◽  
Dermott J. Mullan ◽  
Katrina Exter ◽  
...  
Keyword(s):  
Main Sequence ◽  
Central Star ◽  
High Mass ◽  
Eclipsing Binary ◽  
Triple Systems ◽  
Common Envelope ◽  
Short Period ◽  
Efficiency Parameter ◽  
Hydrodynamical Simulations ◽  
Good Agreement

AbstractV471 Tauri is a short-period eclipsing binary, and a member of the Hyades. It is composed of a hot DA white dwarf (WD) and a cool main-sequence dK2 companion. HST radial velocities of the WD, in combination with the ground-based spectroscopic orbit of the K star, yield dynamical masses of MWD = 0.84 and MdK = 0.93 M⊙. During the UV observations we serendipitously detected coronal mass ejections from the K star, passing in front of the WD and appearing as sudden, transient metallic absorption. Eclipse timings show that the active dK star is 18% larger than a main-sequence star of the same mass, an apparent consequence of its extensive starspot coverage. The high Teff and high mass of the WD are paradoxical: the WD is the most massive in the Hyades, but also the youngest. A plausible scenario is that the progenitor system was a triple, with a close inner pair that merged after several × 108 yr to produce a single blue straggler. When this star evolved to the AGB phase, it underwent a common-envelope interaction with a distant dK companion, which spiraled down to its present separation and ejected the envelope. The common-envelope efficiency parameter, αCE, was of order 0.3–1.0, in good agreement with recent hydrodynamical simulations.SuWt 2 is a southern-hemisphere planetary nebula (PN) with an unusual ring-shaped morphology. The central star is an eclipsing binary with a period of 4.9 days. Surprisingly, the binary is composed of two main-sequence A-type stars with similar masses of ~ 2.5 M⊙. We discuss scenarios involving a third companion which ejected and ionizes the PN.WeBo 1 is a northern PN with a ring morphology remarkably similar to that of SuWt 2. Although we hoped that its central star would shed light on the nature of SuWt 2, it has proven instead to be a late-type barium star!

scholarly journals Testing the impact of satellite anisotropy on large- and small-scale intrinsic alignments using hydrodynamical simulations

2019 ◽  
Vol 491 (4) ◽  
pp. 5330-5350 ◽  
Author(s):  
S Samuroff ◽  
R Mandelbaum ◽  
T Di Matteo
Keyword(s):  
Power Spectra ◽  
Theoretical Description ◽  
Small Scale ◽  
Spherically Symmetric ◽  
Number Density ◽  
Simulated Likelihood ◽  
Hydrodynamical Simulation ◽  
Likelihood Analysis ◽  
Hydrodynamical Simulations ◽  
The Impact

ABSTRACT Galaxy intrinsic alignments (IAs) have long been recognized as a significant contaminant to weak lensing-based cosmological inference. In this paper we seek to quantify the impact of a common modelling assumption in analytic descriptions of IAs: that of spherically symmetric dark matter haloes. Understanding such effects is important as the current generation of IA models are known to be limited, particularly on small scales, and building an accurate theoretical description will be essential for fully exploiting the information in future lensing data. Our analysis is based on a catalogue of 113 560 galaxies between z = 0.06 and 1.00 from massiveblack-ii, a hydrodynamical simulation of box length $100 \, h^{-1}$ Mpc. We find satellite anisotropy contributes at the level of $\ge 30\!-\!40{{\ \rm per\ cent}}$ to the small-scale alignment correlation functions. At separations larger than $1 \, h^{-1}$ Mpc the impact is roughly scale independent, inducing a shift in the amplitude of the IA power spectra of $\sim 20{{\ \rm per\ cent}}$. These conclusions are consistent across the redshift range and between the massiveblack-ii and the illustris simulations. The cosmological implications of these results are tested using a simulated likelihood analysis. Synthetic cosmic shear data are constructed with the expected characteristics (depth, area, and number density) of a future LSST-like survey. Our results suggest that modelling alignments using a halo model based upon spherical symmetry could potentially induce cosmological parameter biases at the ∼1.5σ level for S8 and w.

scholarly journals The nature of submillimetre and highly star-forming galaxies in the EAGLE simulation

2019 ◽  
Vol 488 (2) ◽  
pp. 2440-2454 ◽  
Author(s):  
Stuart McAlpine ◽  
Ian Smail ◽  
Richard G Bower ◽  
A M Swinbank ◽  
James W Trayford ◽  
...  
Keyword(s):  
Reasonable Agreement ◽  
Lower Mass ◽  
Redshift Distribution ◽  
Gas Reservoir ◽  
Massive Galaxies ◽  
Star Forming ◽  
Hydrodynamical Simulation ◽  
Galaxy Population ◽  
Gas Fractions ◽  
Selection Of

ABSTRACT We exploit EAGLE, a cosmological hydrodynamical simulation, to reproduce the selection of the observed submillimetre (submm) galaxy population by selecting the model galaxies at z ≥ 1 with mock submm fluxes $S_{850\, \mu \mathrm{m}}$ ≥ 1 mJy. We find a reasonable agreement between the model galaxies within this sample and the properties of the observed submm population, such as their star formation rates (SFRs) at z < 3, redshift distribution, and many integrated galaxy properties. We find that the median redshift of the $S_{850\, \mu \mathrm{m}}$ ≥ 1 mJy model population is z ≈ 2.5, and that they are massive galaxies (M* ∼ 1011 M⊙) with high dust masses (Mdust ∼ 108 M⊙), gas fractions (fgas ≈ 50 per cent), and SFRs ($\dot{M}_* \approx 100$ M⊙ yr−1). In addition, we find that they have major and minor merger fractions similar to the general population, suggesting that mergers are not the sole driver of the high SFRs in the model submm galaxies. Instead, the $S_{850\, \mu \mathrm{m}}$ ≥ 1 mJy model galaxies yield high SFRs primarily because they maintain a significant gas reservoir as a result of hosting an undermassive black hole relative to comparably massive galaxies. Not all ‘highly star-forming’ ($\dot{M}_* \ge 80$ M⊙ yr−1) eagle galaxies have submm fluxes $S_{850\, \mu \mathrm{m}}$ ≥ 1 mJy. We investigate the nature of these highly star-forming ‘Submm-Faint’ galaxies (i.e. $\dot{M}_* \ge 80$ M⊙ yr−1 but $S_{850\, \mu \mathrm{m}}$ < 1 mJy) and find that they are similar to the model submm galaxies, being gas rich and hosting undermassive black holes. However, they are also typically at higher redshifts (z > 4) and are lower mass (M* ∼ 1010 M⊙). These typically higher redshift galaxies show stronger evidence for having been triggered by major mergers, and critically, they are likely missed by most current submm surveys due to their higher dust temperatures and lower dust masses.

scholarly journals A first quantification of the effects of absorption for H I intensity mapping experiments

2019 ◽  
Vol 631 ◽  
pp. A115
Author(s):  
Sambit Roychowdhury ◽  
Clive Dickinson ◽  
Ian W. A. Browne
Keyword(s):  
Optical Depth ◽  
Column Density ◽  
Radio Continuum ◽  
Redshift Distribution ◽  
Emission Signal ◽  
Intensity Mapping ◽  
Integrated Optical ◽  
Number Counts ◽  
The Impact ◽  
Flux Incident

Context. HI intensity mapping (IM) will be used to do precision cosmology, using many existing and upcoming radio observatories. It will measure the integrated HI 21 cm emission signal from “voxels” of the sky at different redshifts. The signal will be contaminated due to absorption, the largest component of which will be the flux absorbed by the HI emitting sources themselves from the potentially bright flux incident on them from background radio continuum sources. Aims. We, for the first time, provide a quantitative estimate of the magnitude of the absorbed flux compared to the emitted HI flux. The ratio of the two fluxes was calculated for various voxels placed at redshifts between 0.1 and 2.5. Methods. We used a cosmological sky simulation of the atomic HI emission line, and summed over the emitted and absorbed fluxes for all sources within voxels at different redshifts. In order to determine the absorbed flux, for each HI source the flux incident from background radio continuum sources was estimated by determining the numbers, sizes, and redshift distribution of radio continuum sources that lie behind it, based on existing observations and simulations. The amount of this incident flux that is absorbed by each HI source was calculated using a relation between integrated optical depth with HI column density determined using observations of damped Lyman-α systems (DLAs) and sub-DLAs. Results. We find that for the same co-moving volume of sky, the HI emission decreases quickly with increasing redshift, while the absorption varies much less with redshift and follows the redshift distribution of faint sources that dominate the number counts of radio continuum sources. This results in the fraction of absorption compared to emission to be negligible in the nearby Universe (up to a redshift of ∼0.5), increases to about 10% at a redshift of one, and continues to increase to about 30% up to a redshift of 2.5. These numbers can vary significantly due to the uncertainty on the exact form of the following relations: firstly, the number counts of radio continuum sources at sub-mJy flux densities; secondly, the relation between integrated optical depth and HI column density of HI sources; and thirdly, the redshift distribution of radio continuum sources up to the highest redshifts. Conclusions. Absorption of the flux incident from background radio continuum sources might become an important contaminant to HI IM signals beyond redshifts of 0.5. The impact of absorption needs to be quantified more accurately using inputs from upcoming deep surveys of radio continuum sources, H I absorption, and HI emission with the Square Kilometre Array and its precursors.

scholarly journals STUDYING THE INTERACTION BETWEEN MICROQUASAR JETS AND THEIR ENVIRONMENTS

2008 ◽  
Vol 17 (10) ◽  
pp. 1939-1945 ◽  
Author(s):  
M. PERUCHO ◽  
V. BOSCH-RAMON
Keyword(s):  
Binary System ◽  
Surrounding Medium ◽  
High Mass ◽  
Strong Interactions ◽  
Stellar Winds ◽  
Two Dimensional ◽  
Pressure Balance ◽  
Inverse Compton ◽  
Hydrodynamical Simulations ◽  
Accelerated Particles

In high-mass microquasars (HMMQ), strong interactions between jets and stellar winds at binary system scales could occur. In order to explore this possibility, we have performed numerical two-dimensional hydrodynamical simulations of jets crossing the dense stellar material to study how the jet will be affected by these interactions. We find that the jet head generates strong shocks in the wind. These shocks reduce the jet advance speed, and compress and heat up the jet and wind material. In addition, strong recollimation shocks can occur where pressure balance between the jet side and the surrounding medium is reached. All this, together with jet bending, could lead to the destruction of jets with power < 1036 erg/s . The conditions around the outflow shocks would be convenient for accelerating particles up to ~ TeV energies. These accelerated particles could emit via synchrotron and inverse Compton (IC) scattering if they were leptons, and via hadronic processes if they were hadrons.

scholarly journals Influences of protoplanet-induced three-dimensional gas flow on pebble accretion

2020 ◽  
Vol 643 ◽  
pp. A21
Author(s):  
Ayumu Kuwahara ◽  
Hiroyuki Kurokawa
Keyword(s):  
Gas Flow ◽  
Planet Formation ◽  
Early Stage ◽  
Three Dimensional ◽  
Stokes Number ◽  
Flow Shear ◽  
Outer Planets ◽  
Symmetric Structure ◽  
Hydrodynamical Simulation ◽  
Hydrodynamical Simulations

Context. Pebble accretion is among the major theories of planet formation. Aerodynamically small particles, called pebbles, are highly affected by the gas flow. A growing planet embedded in a protoplanetary disk induces three-dimensional (3D) gas flow. In our previous work, Paper I, we focused on the shear regime of pebble accretion and investigated the influence of planet-induced gas flow on pebble accretion. In Paper I, we found that pebble accretion is inefficient in the planet-induced gas flow compared to that of the unperturbed flow, particularly when St ≲ 10−3, where St is the Stokes number. Aims. Following on the findings of Paper I, we investigate the influence of planet-induced gas flow on pebble accretion. We did not consider the headwind of the gas in Paper I. Here, we extend our study to the headwind regime of pebble accretion. Methods. Assuming a nonisothermal, inviscid sub-Keplerian gas disk, we performed 3D hydrodynamical simulations on the spherical polar grid hosting a planet with the dimensionless mass, m = RBondi∕H, located at its center, where RBondi and H are the Bondi radius and the disk scale height, respectively. We then numerically integrated the equation of motion for pebbles in 3D using hydrodynamical simulation data. Results. We first divided the planet-induced gas flow into two regimes: flow-shear and flow-headwind. In the flow-shear regime, where the planet-induced gas flow has a vertically rotational symmetric structure, we find that the outcome is identical to what we obtained in Paper I. In the flow-headwind regime, the strong headwind of the gas breaks the symmetric structure of the planet-induced gas flow. In the flow-headwind regime, we find that the trajectories of pebbles with St ≲ 10−3 in the planet-induced gas flow differ significantly from those of the unperturbed flow. The recycling flow, where gas from the disk enters the gravitational sphere at low latitudes and exits at high latitudes, gathers pebbles around the planet. We derive the flow transition mass analytically, mt, flow, which discriminates between the flow-headwind and flow-shear regimes. From the relation between m, mt, flow and mt, peb, where mt, peb is the transition mass of the accretion regime of pebbles, we classify the results obtained in both Paper I and this study into four groups. In particular, only when the Stokes gas drag law is adopted and m < min(mt, peb, mt, flow), where the accretion and flow regime are both in the headwind regime, the accretion probability of pebbles with St ≲ 10−3 is enhanced in the planet-induced gas flow compared to that of the unperturbed flow. Conclusions. Combining our results with the spacial variety of turbulence strength and pebble size in a disk, we conclude that the planet-induced gas flow still allows for pebble accretion in the early stage of planet formation. The suppression of pebble accretion due to the planet-induced gas flow occurs only in the late stage of planet formation, more specifically, in the inner region of the disk. This may be helpful for explaining the distribution of exoplanets and the architecture of the Solar System, both of which have small inner and large outer planets.

scholarly journals Solar p-mode damping rates: Insight from a 3D hydrodynamical simulation

2019 ◽  
Vol 625 ◽  
pp. A20 ◽  
Author(s):  
K. Belkacem ◽  
F. Kupka ◽  
R. Samadi ◽  
H. Grimm-Strele
Keyword(s):  
Normal Modes ◽  
Turbulent Convection ◽  
Time Duration ◽  
Definitive Answer ◽  
Physical Mechanisms ◽  
Relative Contribution ◽  
Hydrodynamical Simulation ◽  
Red Giant ◽  
Hydrodynamical Simulations ◽  
Mixing Length Theory

Space-borne missions such as CoRoT and Kepler have provided a rich harvest of high-quality photometric data for solar-like pulsators. It is now possible to measure damping rates for hundreds of main-sequence and thousands of red-giant stars with an unprecedented precision. However, among the seismic parameters, mode damping rates remain poorly understood and thus barely used for inferring the physical properties of stars. Previous approaches to model mode damping rates were based on mixing-length theory or a Reynolds-stress approach to model turbulent convection. While they can be used to grasp the main physics of the problem, such approaches are of little help to provide quantitative estimates as well as a definitive answer on the relative contribution of each physical mechanism. Indeed, due to the high complexity of the turbulent flow and its interplay with the oscillations, those theories rely on many free parameters which inhibits an in-depth understanding of the problem. Our aim is thus to assess the ability of 3D hydrodynamical simulations to infer the physical mechanisms responsible for damping of solar-like oscillations. To this end, a solar high-spatial resolution and long-duration hydrodynamical 3D simulation computed with the ANTARES code allows probing the coupling between turbulent convection and the normal modes of the simulated box. Indeed, normal modes of the simulation experience realistic driving and damping in the super-adiabatic layers of the simulation. Therefore, investigating the properties of the normal modes in the simulation provides a unique insight into the mode physics. We demonstrate that such an approach provides constraints on the solar damping rates and is able to disentangle the relative contribution related to the perturbation (by the oscillation) of the turbulent pressure, the gas pressure, the radiative flux, and the convective flux contributions. Finally, we conclude that using the normal modes of a 3D numerical simulation is possible and is potentially able to unveil the respective role of the different physical mechanisms responsible for mode damping provided the time-duration of the simulation is long enough.

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