In the present mainstream cosmology, matter and spacetime emerged from a singularity and evolved through four distinct periods: early inflation, radiation, dark matter and late-time inflation (driven by dark energy). During the radiation and dark matter dominated stages, the universe is decelerating while the early and late-time inflations are accelerating stages. A possible connection between the accelerating periods remains unknown, and, even more intriguing, the best dark energy candidate powering the present accelerating stage (Lambda-vacuum) is plagued with the cosmological constant and coincidence puzzles. Here we propose an alternative solution for such problems based on a large class of time-dependent vacuum energy density models in the form of power series of the Hubble rate, Lambda=Lambda(H). The proposed class of Lambda(H)-decaying vacuum model provides: i) a new mechanism for inflation (different from the usual inflaton models), (ii) a natural mechanism for a graceful exit, which is universal for the whole class of models; iii) the currently accelerated expansion of the universe, iv) a mild dynamical dark energy at present; and v) a final de Sitter stage. Remarkably, the late-time cosmic expansion history of our class of models is very close to the concordance LambdaCDM model, but above all it furnishes the necessary smooth link between the initial and final de Sitter stages through the radiation- and matter-dominated epochs.
Exact solutions of the perturbations equations in the magnetized LambdaCDM scenario are presented. They apply during the dark ages and, more specifically, after the baryons are freed from the drag of the photons. The magnetized growth rate of matter perturbations is compared with the growth index obtained in the concordance paradigm and under the assumption that dark energy does not cluster for a redshift window ranging from the epoch of reionization to the stage of dark-energy dominance. The constraints derived from this analysis are shown to be qualitatively complementary and quantitatively …
Cosmologies with running cosmological term (Lambda) and gravitational Newton's coupling (G) may naturally be expected if the evolution of the universe can ultimately be derived from the first principles of Quantum Field Theory or String Theory. In this paper, we derive the general cosmological perturbation equations for models with variable G and Lambda in which the fluctuations in both variables are explicitly included. We demonstrate that, if matter is covariantly conserved, the late growth of matter density perturbations is independent of the wavenumber. Furthermore, if Lambda is negligible…
We study the cosmic history of the scalaron in $F(R)$ gravity with constructing the time evolution of the cosmic environment and discuss the chameleonic dark matter based on the chameleon mechanism in the early and current Universe. We then find that the scalaron can be a dark matter. We also propose an interesting possibility that the $F(R)$ gravity can address the coincidence problem.
The characteristics of the cosmic microwave background provide circumstantial evidence that the hot radiation-dominated epoch in the early universe was preceded by a period of inflationary expansion. Here, we show how a measurement of the stochastic gravitational wave background can reveal the cosmic history and the physical conditions during inflation, subsequent pre- and re-heating, and the beginning of the hot big bang era. This is exemplified with a particularly well-motivated and predictive minimal extension of the Standard Model which is known to provide a complete model for particle phy…
We propose a simple technique to detect any anisotropic expansion stage in the history of the universe starting from the inflationary stage to the surface of last scattering from the CMBR data. We use the property that any anisotropic expansion in the universe would deform the shapes of the primordial density perturbations and this deformation can be detected in a shape analysis of superhorizon fluctuations in CMBR. Using this analysis we obtain the constraint on any previous anisotropic expansion of the universe to be less than about 35%.
After decades of successful hot big-bang paradigm, Cosmology still lacks a framework in which the early inflationary phase of the universe smoothly matches the radiation epoch and evolves to the present `quasi' de Sitter spacetime. No less intriguing is that the current value of the effective vacuum energy density is vastly smaller than the value that triggered inflation. In this Essay we propose a new class of cosmologies capable of overcoming, or highly alleviating, some of these acute cosmic puzzles. Powered by a decaying vacuum energy density, the spacetime emerges from a pure nonsingular …
Massive gravity provides a natural solution for the dark energy problem of cosmology and is also a candidate for resolving the dark matter problem. I demonstrate that, assuming reasonable scaling relations, massive gravity can provide for Milgrom's law of gravity (or "modified Newtonian dynamics") which is known to remove the need for particle dark matter from galactic dynamics. Milgrom's law comes with a characteristic acceleration, Milgrom's constant, which is observationally constrained to $a_0\approx1.1\times10^{-10}$ m/s$^2$. In the derivation presented here, this constant arises naturall…
We propose an inflationary primordial feature model that can explain both the large and small-scale anomalies in the currently measured cosmic microwave background (CMB) anisotropy spectra, revealing a clip of adventurous history of the Universe during its primordial epoch. Although the model is currently statistically indistinguishable from the Standard Model, we show that future observations such as the Simons Observatory and LiteBIRD will complement each other in distinguishing the model differences due to their accurate E-mode polarization measurements, and the PICO mission, if funded, can…
By confronting the two independent Boltzmann codes CLASS and CAMB, we establish that for concordance cosmology and for a given recombination history, lensed CMB and matter power spectra can be computed by current codes with an accuracy of 0.01%. We list a few tiny changes in CAMB which are necessary in order to reach such a level. Using the common limit of the two codes as a set of reference spectra, we derive precision settings corresponding to fixed levels of error in the computation of a CMB likelihood. We find that for a given precision level, CLASS is about 2.5 times faster than CAMB for …
We present constraints on the cosmic growth history with recent cosmological data, allowing for deviations from Lambda CDM as might arise if cosmic acceleration is due to modifications to GR or inhomogeneous dark energy. We combine measures of the cosmic expansion history, from Type 1a supernovae, baryon acoustic oscillations and the CMB, with constraints on the growth of structure from recent galaxy, CMB and weak lensing surveys along with ISW-galaxy cross-correlations. Deviations from Lambda CDM are parameterized by phenomenological modifications to the Poisson equation and the relationship …
In this paper, we consider a simple form of expansion history of Universe referred to as the hybrid expansion law - a product of power-law and exponential type of functions. The ansatz by construction mimics the power-law and de Sitter cosmologies as special cases but also provides an elegant description of the transition from deceleration to cosmic acceleration. We point out the Brans-Dicke realization of the cosmic history under consideration. We construct potentials for quintessence, phantom and tachyon fields, which can give rise to the hybrid expansion law in general relativity. We invest…
We investigate the effects of the change of cosmological parameters and star formation (SF) models on the cosmic SF history using cosmological smoothed particle hydrodynamics (SPH) simulations based on the cold dark matter (CDM) model. We vary the cosmological parameters within 1-sigma error from the WMAP best-fit parameters, and find that such changes in cosmological parameters mostly affect the amplitude of the cosmic SF history. At high redshift (hereafter high-z), the star formation rate (SFR) is sensitive to the cosmological parameters that control the small-scale power of the primordial …
We use a model for the evolution of galaxies in the far-IR based on the LambdaCDM cosmology to make detailed predictions for upcoming cosmological surveys with the Herschel Space Observatory. We use the combined GALFORM semi-analytical galaxy formation model and GRASIL spectrophotometric code to compute galaxy SEDs including the reprocessing of radiation by dust. The model, which is the same as that in Baugh et al. (2005), assumes two different IMFs: a normal solar neighbourhood IMF for quiescent star formation in disks, and a very top-heavy IMF in starbursts triggered by galaxy mergers. We ha…
The cosmic expansion history proceeds in broad terms from a radiation dominated epoch to matter domination to an accelerated, dark energy dominated epoch. We investigate whether intermittent periods of acceleration are possible in the early universe -- between Big Bang nucleosynthesis (BBN) and recombination and beyond. We establish that the standard picture is remarkably robust: observations of anisotropies in the cosmic microwave background exclude any extra period of accelerated expansion between 1 \leq z \lesssim 10^5 (corresponding to 5\times10^{-4}\ {\rm eV} \leq T \lesssim 25\ {\rm eV})…
This review describes the discovery of the cosmic microwave background radiation in 1965 and its impact on cosmology in the 50 years that followed. This discovery has established the Big Bang model of the Universe and the analysis of its fluctuations has confirmed the idea of inflation and led to the present era of precision cosmology. I discuss the evolution of cosmological perturbations and their imprint on the CMB as temperature fluctuations and polarization. I also show how a phase of inflationary expansion generates fluctuations in the spacetime curvature and primordial gravitational wave…
In this paper we present conjoined constraints on several cosmological models from the expansion history $H(z)$ and cosmic growth $fσ_8(z)$. The models we study include the CPL $w_0w_a$ parametrization, the Holographic Dark Energy (HDE) model, the Time varying vacuum ($Λ_t$CDM) model, the Dvali, Gabadadze and Porrati (DGP) and Finsler-Randers (FRDE) models, a power law $f(T)$ model and finally the Hu-Sawicki $f(R)$ model. In all cases we perform a simultaneous fit to the SnIa, CMB, BAO, $H(z)$ and growth data, while also following the conjoined visualization of $H(z)$ and $fσ_8(z)$ as in Linde…
If ultra-high-energy cosmic rays originate from extragalactic sources, the offsets of their arrival directions from these sources imply an upper limit on the strength of the extragalactic magnetic field. The Pierre Auger Collaboration has recently reported that anisotropy in the arrival directions of cosmic rays is correlated with several types of extragalactic objects. If these cosmic rays originate from these objects, they imply a limit on the extragalactic magnetic field strength of B < 0.7-2.2 x 10^-9 (lambda_B / 1 Mpc)^-1/2 G for coherence lengths lambda_B < 100 Mpc and B < 0.7-2.2 x 10^-…
We investigate the creation of cold dark matter (CCDM) cosmology as an alternative to explain the cosmic acceleration. Particular attention is given to the evolution of density perturbations and constraints coming from recent observations. By assuming negligible effective sound speed we compare CCDM predictions with redshift-space-distortion based f(z) sigma_8(z) measurements. We identify a subtle issue associated with which contribution in the density contrast should be used in this test and then show that the CCDM results are the same as those obtained with LambdaCDM. These results are then …
A continuous transition from early Friedmann-like radiation era through to late time cosmic acceleration passing through a long Friedmann-like matter dominated era followed by a second phase of radiation era has been realized in modified theory of gravity containing a combination of curvature squared term, a linear term, a three-half term and an ideal fluid. Thus the history of cosmic evolution is explained by modified theory of gravity singlehandedly. The second phase of radiation-like era might provide an explanation to the hydrogen and helium reionization at low redshift.
I review our current understanding of massive black hole (MBH) formation and evolution along the cosmic history. After a brief introductory overview of the relevance of MBHs in the hierarchical structure formation paradigm, I discuss the main viable channels for seed BH formation at high redshift and for their subsequent mass growth and spin evolution. The emerging hierarchical picture, where MBHs grow through merger triggered accretion episodes, acquiring their mass while shining as quasars, is overall robust, but too simplistic to explain the diversity observed in MBH phenomenology. I briefl…
Multiple astrophysical probes of the cosmic star formation history yield widely different inferences of this rate at redshifts z > 1. While all probes seem to indicate a period of peak star formation known as the cosmic noon between 1.5 < z < 3, the detailed inferences from these probes are in disagreement. In particular, the magnitude of the peak star formation rate density indicated by H-alpha data is higher by a factor of ~ 4 compared to the magnitude of the peak indicated by UV/IR data. In this work, we explore the potential of future measurements of the diffuse supernova neutrino backgrou…
We show that the cumulative CO emission from galaxies throughout cosmic history distorts the spectrum of the cosmic microwave background (CMB) at a level that is well above the detection limit of future instruments, such as the Primordial Inflation Explorer (PIXIE). The modeled CO signal has a prominent bump in the frequency interval 100-200 GHz, with a characteristic peak intensity of ~ 2$\times$10$^{-23}$ W m$^{-2}$ Hz$^{-1}$ sr$^{-1}$. Most of the CO foreground originates from modest redshifts, z ~ 2-5, and needs to be efficiently removed for more subtle distortions from the earlier univers…
Cosmic history can be traced considering further curvature contributions inside the gravitational action. Assuming that standard General Relativity can be extended by other curvature invariants, we discuss the possibility that an action containing higher-order curvature terms can fit, in principle, the whole universe evolution. In particular, a theory like $F(R,{\cal G})$, with $R$ the Ricci scalar and $\cal G$ the Gauss-Bonnet topological term, contains all the curvature invariants that, depending on the energy regime, can address inflation, matter dominated and dark energy regimes. In this p…
We present a quantitative analysis of the constraints on the total equation of state parameter that can be obtained from measuring the red shift evolution of the cosmic shear. We compare the constraints that can be obtained from measurements of the spin two angular multipole moments of the cosmic shear to those resulting from the two dimensional and three dimensional power spectra of the cosmic shear. We find that if the multipole moments of the cosmic shear are measured accurately enough for a few red shifts the constraints on the dark energy equation of state parameter improve significantly …
Cosmic Reionization imprints its signature on the temperature and polarization anisotropies of the cosmic microwave background (CMB). Advances in CMB telescopes have already placed a significant constraint on the history of reionization. As near-future CMB telescopes target the maximum sensitivity, or observations limited only by the cosmic variance (CV), we hereby forecast the potential of future CMB observations in constraining the history of reionization. In this study, we perform Markov Chain Monte Carlo analysis for CV-limited E-mode polarization observations such as the LiteBIRD (Light s…
The cosmological constant $Λ$ can be achieved as the result of entangled and statistically correlated minisuperspace cosmological states, built up by using a minimal choice of observable quantities, i.e. $Ω_{m}$ and $Ω_{k}$, which assign the cosmic dynamics. In particular, we consider a cosmological model where two regions, corresponding to two correlated eras, are involved; the present universe description would be, in this way, given by a density matrix $\hat ρ$, corresponding to an entangled final state. Starting from this assumption, it is possible to infer some considerations on the cosmi…
We present charm (cosmic history agnostic reconstruction method), a novel inference algorithm that reconstructs the cosmic expansion history as encoded in the Hubble parameter $H(z)$ from SNe Ia data. The novelty of the approach lies in the usage of information field theory, a statistical field theory that is very well suited for the construction of optimal signal recovery algorithms. The charm algorithm infers non-parametrically $s(a)=\ln(ρ(a)/ρ_{\mathrm{crit}0})$, the density evolution which determines $H(z)$, without assuming an analytical form of $ρ(a)$ but only its smoothness with the sca…
Space based gravitational wave astronomy will open a completely new window on the Universe and massive black holes binaries are expected to be among the primary actors on this upcoming stage. The New Gravitational-wave Observatory (NGO) is a space interferometer proposal derived from the former Laser Interferometer Space Antenna (LISA) concept. We describe here its capabilities of observing massive black hole binaries throughout the Universe, measuring their relevant parameters (masses, spins, distance to the observer) to high precision. The statistical properties of the population of detected…
The 21-cm PDF (i.e., distribution of pixel brightness temperatures) is expected to be highly non-Gaussian during reionization and to provide important information on the distribution of density and ionization. We measure the 21-cm PDF as a function of redshift in a large simulation of cosmic reionization and propose a simple empirical fit. Guided by the simulated PDF, we then carry out a maximum likelihood analysis of the ability of upcoming experiments to measure the shape of the 21-cm PDF and derive from it the cosmic reionization history. Under the strongest assumptions, we find that upcomi…
It has been suggested that the cosmic history might repeat in cycles, with an infinite series of similar aeons in the past and the future. Here, we instead propose that the cosmic history repeats itself exactly, constructing a universe on a periodic temporal history, which we call Periodic Time Cosmology. In particular, the primordial power spectrum, convolved with the transfer function throughout the cosmic history, would form the next aeon's primordial power spectrum. By matching the big bang to the infinite future using a conformal rescaling (a la Penrose), we uniquely determine the primord…
We use the machine learning techniques, for the first time, to study the background evolution of the universe in light of 30 cosmic chronometers. From 7 machine learning algorithms, using the principle of mean squared error minimization on testing set, we find that Bayesian ridge regression is the optimal method to extract the information from cosmic chronometers. By use of a power-law polynomial expansion, we obtain the first Hubble constant estimation $H_0=65.95^{+6.98}_{-6.36}$ km s$^{-1}$ Mpc$^{-1}$ from machine learning. From the view of machine learning, we may rule out a large number of…
Significant progress has been made in the last few years on understanding how supermassive black holes form and grow. In this paper, we begin by reviewing the spectral signatures of Active Galactic Nuclei (AGN) ranging from radio to hard X-ray wavelengths. We then describe the most commonly used methods to find these sources, including optical/UV, radio, infrared and X-ray emission and optical emission lines. We then describe the main observational properties of the obscured and unobscured AGN population. Finally, we summarize the cosmic history of black hole accretion, i.e., when in the histo…
The standard disc formation scenario postulates that disc forms as the gas cools and flows into the centre of the dark matter halo, conserving the specific angular momentum. Major mergers have been shown to be able to destroy or highly perturb the disc components. More recently, the alignment of the material that is accreted to form the galaxy has been pointed out as a key ingredient to determine galaxy morphology. However, in a hierarchical scenario galaxy formation is a complex process that combines these processes and others in a non-linear way so that the origin of galaxy morphology remain…
We compare the results from several sets of cosmological simulations of cosmic reionization, produced under Cosmic Reionization On Computers (CROC) project, with existing observational data on the high-redshift Ly-alpha forest and the abundance of Ly-alpha emitters. We find good consistency with the observational measurements and the previous simulation work. By virtue of having several independent realizations for each set of numerical parameters, we are able to explore the effect of cosmic variance on observable quantities. One unexpected conclusion we are forced into is that cosmic variance…
The recent EDGES measurements of the global 21-cm signal from the cosmic dawn suggest that the kinetic temperature of the inter-galactic medium (IGM) might be significantly lower compared to its expected value. The colder IGM directly affects the hydrogen recombination of the universe during the cosmic dawn and dark ages by enhancing the rate of recombinations. Here, we study and quantify, the impact of the colder IGM scenario on the recombination history of the universe in the context of DM-baryonic interaction model which is widely used to explain the depth of the EDGES 21-cm signal. We find…
During cosmic reionization, the 21-cm brightness fluctuations were highly non-Gaussian, and complementary statistics can be extracted from the distribution of pixel brightness temperatures that are not derivable from the 21-cm power spectrum. One such statistic is the 21-cm difference PDF, the probability distribution function of the difference in the 21-cm brightness temperatures between two points, as a function of the distance between the points. Guided by 21-cm difference PDFs extracted from simulations, we perform a maximum likelihood analysis on mock observational data, and analyze the a…
We constrain the history of reionization using the data from Planck 2015 Cosmic Microwave Background (CMB) temperature and polarization anisotropy observations. We also use prior constraints on the reionization history at redshifts $\sim7-8$ obtained from Lyman-$α$ emission observations. Using the free electron fractions at different redshifts as free parameters, we construct the complete reionization history using polynomials. Our construction provides an extremely flexible framework to search for the history of reionization as a function of redshifts. We present a conservative and an optimis…
Astronomical observations suggest that today's Universe is dominated by a dark energy of unknown physical origin. One of the most notable consequences in many models is that dark energy should cause the expansion of the Universe to accelerate: but the expansion rate as a function of time has proven very difficult to measure directly. We present a new determination of the cosmic expansion history by combining distant supernovae observations with a geometrical analysis of large-scale galaxy clustering within the WiggleZ Dark Energy Survey, using the Alcock-Paczynski test to measure the distortio…
In this paper we give a brief review of the astrophysics of active galactic nuclei (AGN). After a general introduction motivating the study of AGNs, we discuss our present understanding of the inner workings of the central engines, most likely accreting black holes with masses between a million and ten billion solar masses. We highlight recent results concerning the jets (collimated outflows) of AGNs derived from X-ray observations (Chandra) of kpc-scale jets and gamma-ray observations of AGNs (Fermi, Cherenkov telescopes) with jets closely aligned with the lines of sight (blazars), and discus…
The standard relation between the cosmological redshift and cosmic scale factor underlies cosmological inference from virtually all kinds of cosmological observations, leading to the emergence of the LambdaCDM cosmological model. This relation is not a fundamental theory and thus observational determination of this function (redshift remapping) should be regarded as an insightful alternative to holding its standard form in analyses of cosmological data. Here we present non-parametric reconstructions of redshift remapping in dark-matter-dominated models and constraints on cosmological parameter…
Intermediate-mass black holes (IMBHs) have not been detected beyond any reasonable doubt through either dynamical or accretion signatures. Gravitational waves (GWs) represent an unparalleled opportunity to survey the sky and detect mergers of IMBHs, making it possible for the first time to constrain their formation, growth, and merger history across cosmic time. While the current network LIGO-Virgo-KAGRA is significantly limited in detecting mergers of IMBH binaries, the next generation of ground-based observatories and space-based missions promise to shed light on the IMBH population through …
The Cosmic Expansion History from Line-Intensity Mapping
University of Barcelona（巴塞罗那大学）；Institut d’Estudis Espacials de Catalunya (IEEC)（加泰罗尼亚空间研究学院）；University of Toronto（多伦多大学）；Ben-Gurion University（本-古里安大学）
The measurement of the expansion history of the Universe from the redshift unknown gravitational wave (GW) sources (dark GW sources) detectable from the network of \texttt{LIGO-Virgo-KAGRA} (\texttt{LVK}) detectors depends on the synergy with the galaxy surveys having accurate redshift measurements over a broad redshift range, large sky coverage, and detectability of fainter galaxies. In this work, we explore the possible synergy of the LVK with the spectroscopic galaxy surveys such as \texttt{DESI} and \texttt{SPHEREx} to measure the cosmological parameters which are related to the cosmic exp…
From the time the first stars formed over 13 billion years ago to the present, star formation has had an unexpectedly dynamic history. At first, the star formation rate density increased dramatically, reaching a peak 10 billion years ago more than ten times the present day value. Observations of the initial rise in star formation remain difficult, poorly constraining it. Theoretical modeling has trouble predicting this history because of the difficulty in following the feedback of energy from stellar radiation and supernova explosions into the gas from which further stars form. Observations fr…
Marginal likelihoods for the cosmic expansion rates are evaluated using the recent `Constitution' data of 397 supernovas, thereby updating the results in some previous works. Even when beginning with a very strong prior probability that favors an accelerated expansion, we end up with a marginal likelihood for the deceleration parameter $q_0$ peaked around zero in the spatially flat case. This is in agreement with some other analysis of the Constitution data. It is also found that the new data significantly constrains the cosmic expansion rates, when compared to the previous analysis. Here agai…
Significant historic cosmic evolution for the formation rate of stellar black holes is inferred from current theoretical models of the evolution of massive stars, the multiple observations of compact stellar remnants in the near and distant universe, and the cosmic chemical evolution. The mean mass of stellar black holes, the fraction of black holes/neutron stars, and the fraction of black hole high mass X-ray binaries (BH-HMXBs)/solitary black holes increase with redshift. The energetic feedback from large populations of BH-HMXBs form in the first generations of star burst galaxies has been o…
Revealing the cosmic reionisation history is at the frontier of extragalactic astronomy. The power spectrum of the cosmic microwave background (CMB) polarisation can be used to constrain the reionisation history. Here we propose a CMB-independent method using fast radio bursts (FRBs) to directly measure the ionisation fraction of the intergalactic medium (IGM) as a function of redshift. FRBs are new astronomical transients with millisecond timescales. Their dispersion measure (DM$_{\rm IGM}$) is an indicator of the amount of ionised material in the IGM. Since the differential of DM$_{\rm IGM}$…
We have evaluated the contribution of the AGN population to the ionization history of the Universe based on a semi-analytic model of galaxy formation and evolution in the CDM cosmological scenario. The model connects the growth of black holes and of the ensuing AGN activity to galaxy interactions. In the model we have included a self consistent physical description of the escape of ionizing UV photons; this is based on the blast-wave model for the AGN feedback we developed in a previous paper to explain the distribution of hydrogen column densities in AGNs of various redshifts and luminosities…
We extend the existing analytical model of reionization by Furlanetto et al. (2004) to include the biasing of reionization sources and additional absorption by Lyman Limit systems. Our model is, by construction, consistent with the observed evolution of the galaxy luminosity function at z<8 and with the observed evolution of Ly-α forest at z<6. We also find that, for a wide range of values for the relative escape fraction that we consider reasonable, and which are consistent with the observational constraints on the relative escape fraction from lower redshifts, our reionization model is consi…
Present-day clusters are massive halos containing mostly quiescent galaxies, while distant protoclusters are extended structures containing numerous star-forming galaxies. We investigate the implications of this fundamental change in a cosmological context using a set of N-body simulations and semi-analytic models. We find that the fraction of the cosmic volume occupied by all (proto)clusters increases by nearly three orders of magnitude from z=0 to z=7. We show that (proto)cluster galaxies are an important, and even dominant population at high redshift, as their expected contribution to the c…
The cosmic expansion history, mapped by the Hubble parameter as a function of redshift, offers the most direct probe of the dark energy equation of state. One way to determine the Hubble parameter at different redshifts is essentially differentiating the cosmic age or distance with respect to redshift, which may incur large numerical errors with observational data. Taking the scenario that the Hubble parameter increases monotonically with redshift as a reasonable prior, we propose to enforce the monotonicity when reconstructing the Hubble parameter at a series of redshifts. Tests with mock typ…
Both simulations and observations have shown that turbulence is a pervasive phenomenon in cosmic scenarios, yet it is particularly difficult to model numerically due to its intrinsically multiscale character which demands high resolutions. Additionally, turbulence is tightly connected to the dynamical state and the formation history of galaxies and galaxy clusters, producing a diverse phenomenlogy which requires large samples of such structures to attain robust conclusions. In this work, we use an adaptive mesh refinement (AMR) cosmological simulation to explore the generation and dissipation …
Cosmic voids are underdense regions filling up most of the volume in the Universe. They are expected to emerge in regions comprising negative initial density fluctuations, and subsequently expand as the matter around them collapses and forms walls, filaments and clusters. We report results from the analysis of a cosmological simulation specially designed to accurately describe low-density regions, such as cosmic voids. Contrary to the common expectation, we find that voids also experience significant mass inflows over cosmic history. On average, $10\%$ of the mass of voids in the sample at $z …
We use a suite of cosmological, hydrodynamical simulations to investigate the chemical enrichment history of the Universe. Specifically, we trace the origin of the metals back in time to investigate when various gas phases were enriched and by what halo masses. We find that the age of the metals decreases strongly with the density of the gas in which they end up. At least half of the metals that reside in the diffuse intergalactic medium (IGM) at redshift zero (two) were ejected from galaxies above redshift two (three). The mass of the haloes that last contained the metals increases rapidly wi…
We reveal cosmic star-formation history obscured by dust using deep infrared observation with the AKARI. A continuous filter coverage in the mid-IR wavelength (2.4, 3.2, 4.1, 7, 9, 11, 15, 18, and 24um) by the AKARI satellite allows us to estimate restframe 8um and 12um luminosities without using a large extrapolation based on a SED fit, which was the largest uncertainty in previous work. We found that restframe 8um (0.38<z<2.2), 12um (0.15<z<1.16), and total infrared (TIR) luminosity functions (LFs) (0.2<z<1.6) constructed from the AKARI NEP deep data, show a continuous and strong evolution t…
