Cosmological Probes Research Articles

Multipole expansion for 21 cm intensity mapping power spectrum: Forecasted cosmological parameters estimation for the SKA observatory

ABSTRACTThe measurement of the large-scale distribution of neutral hydrogen in the late Universe, obtained with radio telescopes through the hydrogen 21 cm line emission, has the potential to become a key cosmological probe in the upcoming years. We explore the constraining power of 21 cm intensity mapping observations on the full set of cosmological parameters that describe the ΛCDM model. We assume a single-dish survey for the SKA Observatory and simulate the 21 cm linear power spectrum monopole and quadrupole within six redshift bins in the range $z$ = 0.25–3. Forecasted constraints are computed numerically through Markov Chain Monte Carlo techniques. We extend the sampler CosmoMC by implementing the likelihood function for the 21 cm power spectrum multipoles. We assess the constraining power of the mock data set alone and combined with Planck 2018 CMB observations. We find that 21 cm multipoles observations alone are enough to obtain constraints on the cosmological parameters comparable with other probes. Combining the 21 cm data set with CMB observations results in significantly reduced errors on all the cosmological parameters. The strongest effect is on Ωch2 and H0, for which the error is reduced by almost a factor four. The percentage errors we estimate are $\sigma _{\Omega _ch^2} = 0.25~{{\ \rm per\ cent}}$ and $\sigma _{H_0} = 0.16~{{\ \rm per\ cent}}$, to be compared with the Planck only results $\sigma _{\Omega _ch^2} = 0.99~{{\ \rm per\ cent}}$ and $\sigma _{H_0} = 0.79~{{\ \rm per\ cent}}$. We conclude that 21 cm SKAO observations will provide a competitive cosmological probe, complementary to CMB and, thus, pivotal for gaining statistical significance on the cosmological parameters constraints, allowing a stress test for the current cosmological model.

A possible signature of the influence of tidal perturbations in dwarf galaxy scaling relations

ABSTRACT Dwarf galaxies are excellent cosmological probes, because their shallow potential wells make them very sensitive to the key processes that drive galaxy evolution, including baryonic feedback, tidal interactions, and ram pressure stripping. However, some of the key parameters of dwarf galaxies, which help trace the effects of these processes, are still debated, including the relationship between their sizes and masses. We re-examine the Fornax Cluster dwarf population from the point of view of isomass-radius–stellar mass relations (IRSMRs) using the Fornax Deep Survey Dwarf galaxy Catalogue, with the centrally located (among dwarfs) $3.63 \mathcal {M}_{\odot }$ pc−2 isodensity radius defining our fiducial relation. This relation is a powerful diagnostic tool for identifying dwarfs with unusual structure, as dwarf galaxies’ remarkable monotonicity in light profile shapes, as a function of stellar mass, reduces the relation’s scatter tremendously. By examining how different dwarf properties (colour, 10th nearest neighbour distance, etc.) correlate with distance from our fiducial relation, we find a significant population of structural outliers with comparatively lower central mass surface density and larger half-light-radii, residing in locally denser regions in the cluster, albeit with similar red colours. We propose that these faint, extended outliers likely formed through tidal disturbances, which make the dwarfs more diffuse, but with little mass-loss. Comparing these outliers with ultra-diffuse galaxies (UDGs), we find that the term UDG lacks discriminatory power; UDGs in the Fornax Cluster lie both on and off of IRSMRs defined at small radii, while IRSMR outliers with masses below $\sim 10^{7.5} \mathcal {M}_{\odot }$ are excluded from the UDG classification due to their small effective radii.

Euclid preparation

Euclid’s photometric galaxy cluster survey has the potential to be a very competitive cosmological probe. The main cosmological probe with observations of clusters is their number count, within which the halo mass function (HMF) is a key theoretical quantity. We present a new calibration of the analytic HMF, at the level of accuracy and precision required for the uncertainty in this quantity to be subdominant with respect to other sources of uncertainty in recovering cosmological parameters from Euclid cluster counts. Our model is calibrated against a suite of N-body simulations using a Bayesian approach taking into account systematic errors arising from numerical effects in the simulation. First, we test the convergence of HMF predictions from different N-body codes, by using initial conditions generated with different orders of Lagrangian Perturbation theory, and adopting different simulation box sizes and mass resolution. Then, we quantify the effect of using different halo finder algorithms, and how the resulting differences propagate to the cosmological constraints. In order to trace the violation of universality in the HMF, we also analyse simulations based on initial conditions characterised by scale-free power spectra with different spectral indexes, assuming both Einstein–de Sitter and standard ΛCDM expansion histories. Based on these results, we construct a fitting function for the HMF that we demonstrate to be sub-percent accurate in reproducing results from 9 different variants of the ΛCDM model including massive neutrinos cosmologies. The calibration systematic uncertainty is largely sub-dominant with respect to the expected precision of future mass–observation relations; with the only notable exception of the effect due to the halo finder, that could lead to biased cosmological inference.

Offset between X-ray and optical centers in clusters of galaxies: Connecting eROSITA data with simulations

Context.The characterization of the dynamical state of galaxy clusters is key to studying their evolution, evaluating their selection, and using them as a cosmological probe. In this context, the offsets between different definitions of the center have been used to estimate the cluster disturbance.Aims.Our goal is to study the distribution of the offset between the X-ray and optical centers in clusters of galaxies. We study the offset for clusters detected by the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Spectrum-Roentgen-Gamma (SRG) observatory. We aim to connect observations to predictions by hydrodynamical simulations andN-body models. We assess the astrophysical effects affecting the displacements.Methods.We measured the offset for clusters observed in the eROSITA Final Equatorial-Depth Survey (eFEDS) and the first eROSITA all-sky survey (eRASS1). We focus on a subsample of 87 massive eFEDS clusters at low redshift, withM500c> 1×1014 M⊙and 0.15 <z< 0.4. We compared the displacements in such sample to those predicted by the TNG and the Magneticum simulations. We additionally link the observations to the offset parameterXoffmeasured for dark matter halos inN-body simulations, using the hydrodynamical simulations as a bridge.Results.We find that, on average, the eFEDS clusters show a smaller offset compared to eRASS1 because the latter contains a larger fraction of massive and disturbed structures. We measured an average offset of ΔX−O = 76.3−27.1+30.1kpc, when focusing on the subsample of 87 eFEDS clusters. This is in agreement with the predictions from TNG and Magneticum, and the distribution ofXofffrom dark matter only (DMO) simulations. However, the tails of the distributions are different. Using ΔX − Oto classify relaxed and disturbed clusters, we measured a relaxed fraction of 31% in the eFEDS subsample. Finally, we found a correlation between the offset measured on hydrodynamical simulations andXoffmeasured on their parent dark-matter-only run and we calibrated the relation between them.Conclusions.We conclude that there is good agreement between the offsets measured in eROSITA data and the predictions from simulations. Baryonic effects cause a decrement (increment) in the low (high) offset regime compared to theXoffdistribution from dark matter-only simulations. The offset–Xoffrelation provides an accurate prediction of the trueXoffdistribution in Magneticum and TNG. It allows for the offsets to be introduced in a cosmological context with a new method in order to marginalize over selection effects related to the cluster dynamical state.

New constraints on macroscopic dark matter using radar meteor detectors

We show that dark-matter candidates with large masses and large nuclear interaction cross sections are detectable with terrestrial radar systems. We develop our results in close comparison to successful radar searches for tiny meteoroids, aggregates of ordinary matter. The path of a meteoroid (or suitable dark-matter particle) through the atmosphere produces ionization deposits that reflect incident radio waves. We calculate the equivalent radar echoing area or `radar cross section' for dark matter. By comparing the expected number of dark-matter-induced echoes with observations, we set new limits in the plane of dark-matter mass and cross section, complementary to pre-existing cosmological limits. Our results are valuable because (A) they open a new detection technique for which the reach can be greatly improved and (B) in case of a detection, the radar technique provides differential sensitivity to the mass and cross section, unlike cosmological probes.

An 8.0% Determination of the Baryon Fraction in the Intergalactic Medium from Localized Fast Radio Bursts

The dispersion measure (DM)–redshift relation of fast radio bursts (FRBs) has been proposed as a potential new tool for probing the intergalactic medium (IGM) and for studying cosmology. However, poor knowledge of the baryon fraction in the IGM (f IGM) and its degeneracy with cosmological parameters impose restrictions on the cosmological applications of FRBs. Furthermore, DMs contributed by the IGM (DMIGM) and host galaxy (DMhost), important cosmological quantities, cannot be exactly extracted from observations, which would bring uncontrolled systematic uncertainties in FRB cosmology. In this work, we use 17 localized FRBs to constrain f IGM and its possible redshift evolution. Other cosmological probes such as type Ia supernovae, baryon acoustic oscillations, and cosmic microwave background radiation are combined to break parameter degeneracy. Taking into account the probability distributions of DMIGM and DMhost derived from the IllustrisTNG simulation, we obtain a robust measurement of f IGM = 0.927 ± 0.075, representing a precision of 8.0%. We find that there is no strong evidence for the redshift dependence of f IGM at the current observational data level. The rapid progress in localizing FRBs will significantly improve the constraints on f IGM.

Doppler Boosted Dust Emission and Cosmic Infrared Background-Galaxy Cross-Correlations: A New Probe of Cosmology and Astrophysics.

We identify a new cosmological signal, the Doppler-boosted cosmic infrared background (DB CIB), arising from the peculiar motion of the galaxies whose thermal dust emission source the cosmic infrared background (CIB). This new observable is an independent probe of the cosmic velocity field, highly analogous to the well-known kinematic Sunyaev-Zel'dovich (KSZ) effect. Interestingly, DB CIB does not suffer from the "KSZ optical depth degeneracy," making it immune from the complex astrophysics of galaxy formation. We forecast that the DB CIB effect is detectable in the cross-correlation of CCAT-Prime and DESI-like experiments. We show that it also acts as a new CMB foreground which can bias future KSZ cross-correlations, if not properly accounted for.

Intensity mapping of post-reionization 21-cm signal and its cross-correlations as a probe of f(R) gravity

We propose the intensity mapping of the redshifted Hi 21-cm signal from the post-reionization epoch as a cosmological probe of f(R) gravity. We consider the Hu–Sawicki family of f(R) gravity models characterized by a single parameter $$f_{,R0}$$ . The f(R) modification to gravity affects the post-reionization 21-cm power spectrum through the change in the growth rate of density fluctuations. We find that a radio interferometric observation with a SKA1-mid-like radio telescope in both auto-correlation and cross-correlation with galaxy weak-lensing and Lyman- $$\alpha $$ forest may distinguish f(R) models from $$\Lambda $$ CDM cosmology at a precision, which is competitive with other probes of f(R) gravity.

Probing large-scale ionizing background fluctuation with Lyman α forest and galaxy cross-correlation at z = 2.4

ABSTRACT The amplitude of the metagalactic ultraviolet background (UVB) at large scales is impacted by two factors. First, it naturally attenuates at scales larger than mean-free path of UVB photons due to the absorption by neutral intergalactic medium. Second, there are discrete and rare ionizing sources distributing in the Universe, emitting the UVB photons, and thus enhancing the local UVB amplitude. Therefore, for cosmological probe that is sensitive to the UVB amplitude and capable of detecting the large scale like Lyman α forest spectrum, the fluctuation due to the clustering of ionizing sources becomes a significant factor for Lyman α flux transmission and leave imprints on Lyman α flux power spectrum at these large scales. In this work, we make use of a radiative transfer model that parametrizes the UVB source distribution by its bias bj and shot noise $\overline{n}_{\rm j}$. We estimate the constraints on this model through the cross-correlation between Lyman α forest survey and galaxy survey, using the DESI Lyman α forest survey and the Roman Space Telescope emission line galaxy survey as an example. We show the detection sensitivity improvement for UVB parameters from disjoint to maximal overlap of DESI + Roman survey strategy. We also show that the degeneracy of two ionizing source parameters can be broken by increasing the overlapping survey area. Our results motivate survey strategies more dedicated to probe the UVB large-scale fluctuations.

Constraining Coupling Constants’ Variation with Supernovae, Quasars, and GRBs

Dirac, in 1937, proposed the potential variation of coupling constants derived from his large numbers hypothesis. Efforts have continued since then to constrain their variation by various methods, including astrophysical and cosmological observations. We briefly discuss several methods used for the purpose while focusing primarily on the use of supernovae type 1a, quasars, and gamma-ray bursts as cosmological probes for determining cosmological distances. Supernovae type Ia (SNeIa) are considered the best standard candles since their intrinsic luminosity can be determined precisely from their light curves. However, they have only been observed up to about redshift z=2.3, mostly at z≤1.5. Quasars are the brightest non-transient cosmic sources in the Universe. They have been observed up to z=7.5. Certain types of quasars can be calibrated well enough for their use as standard candles but with a higher degree of uncertainty in their intrinsic luminosity than SNeIa. Gamma-ray bursts (GRBs) are even brighter than quasars, and they have been observed up to z=9.4. They are sources of highly transient radiation lasting from tens of milliseconds to several minutes and, in rare cases, a few hours. However, they are even more challenging to calibrate as standard candles than quasars. Both quasars and GRBs use SNeIa for distance calibration. What if the standard candles’ intrinsic luminosities are affected when the coupling constants become dynamic and depend on measured distances? Assuming it to be constant at all cosmic distances leads to the wrong constraint on the data-fitted model parameters. This paper uses our earlier finding that the speed of light c, the gravitational constant G, the Planck constant h, and the Boltzmann constant k vary in such a way that their variation is interrelated as G~c3~h3~k3/2 with G˙/G=3c˙/c=3h˙/h=1.5k˙/k =3.90±0.04×10−10 yr−1 and corroborates it with SNeIa, quasars, and GRBs observational data. Additionally, we show that this covarying coupling constant model may be better than the standard ΛCDM model for using quasars and GRBs as standard candles and predict that the mass of the GRBs scales with z as 1+z1/3−1. Noether’s symmetry on the coupling constants is now transferred effectively to the constant in the function relating to their variation.

Exploring bulk viscous unified scenarios with gravitational waves standard sirens

ABSTRACT We consider the unified bulk viscous scenarios and constrain them using the Cosmic Microwave Background observations from Planck 2018 and the Pantheon sample from Type Ia supernovae. Then we generate the luminosity distance measurements from ${\cal O}(10^3)$ mock Gravitational Wave Standard Sirens (GWSS) events for the proposed Einstein Telescope. We then combine these mock luminosity distance measurements from the GWSS with the current cosmological probes in order to forecast how the mock GWSS data could be effective in constraining these bulk viscous scenarios. Our results show that a non-zero time dependent bulk viscosity in the universe sector is strongly preferred by the current cosmological probes and will possibly be confirmed at many standard deviations by the future GWSS measurements. We further mention that the addition of GWSS data can significantly reduce the uncertainties of the key cosmological parameters obtained from the usual cosmological probes employed in this work.

It takes two to know one: computing accurate one-point PDF covariances from effective two-point PDF models

One-point probability distribution functions (PDFs) of the cosmic matter density are powerful cosmological probes that extract non-Gaussian properties of the matter distribution and complement two-point statistics. Computing the covariance of one-point PDFs is key for building a robust galaxy survey analysis for upcoming surveys like Euclid and the Rubin Observatory LSST and requires good models for the two-point PDFs characterising spatial correlations. In this work, we obtain accurate PDF covariances using effective shifted lognormal two-point PDF models for the mildly non-Gaussian weak lensing convergence and validate our predictions against large sets of Gaussian and non-Gaussian maps. We show how the dominant effects in the covariance matrix capturing super-sample covariance arise from a large-separation expansion of the two-point PDF and discuss differences between the covariances obtained from small patches and full sky maps. Finally, we describe how our formalism can be extended to characterise the PDF covariance for 3D-dimensional spectroscopic fields using the 3D matter PDF as an example. We describe how covariances from simulated boxes with fixed overall density can be supplemented with the missing super-sample covariance effect by relying on theoretical predictions validated against separate-universe style simulations.

Probing the consistency of cosmological contours for supernova cosmology

Abstract As the scale of cosmological surveys increases, so does the complexity in the analyses. This complexity can often make it difficult to derive the underlying principles, necessitating statistically rigorous testing to ensure the results of an analysis are consistent and reasonable. This is particularly important in multi-probe cosmological analyses like those used in the Dark Energy Survey (DES) and the upcoming Legacy Survey of Space and Time, where accurate uncertainties are vital. In this paper, we present a statistically rigorous method to test the consistency of contours produced in these analyses and apply this method to the Pippin cosmological pipeline used for type Ia supernova cosmology with the DES. We make use of the Neyman construction, a frequentist methodology that leverages extensive simulations to calculate confidence intervals, to perform this consistency check. A true Neyman construction is too computationally expensive for supernova cosmology, so we develop a method for approximating a Neyman construction with far fewer simulations. We find that for a simulated dataset, the 68% contour reported by the Pippin pipeline and the 68% confidence region produced by our approximate Neyman construction differ by less than a percent near the input cosmology; however, they show more significant differences far from the input cosmology, with a maximal difference of 0.05 in $\Omega_{M}$ and 0.07 in w. This divergence is most impactful for analyses of cosmological tensions, but its impact is mitigated when combining supernovae with other cross-cutting cosmological probes, such as the cosmic microwave background.

H0 Tension on the Light of Supermassive Black Hole Shadows Data

Cosmological tensions in current times have opened a wide door to study new probes to constrain cosmological parameters, specifically, to determine the value of the Hubble constant H0 through independent techniques. The two standard methods to measure/infer H0 rely on: (i) anchored observables for the distance ladder, and (ii) establishing the relationship of the H0 to the angular size of the sound horizon in the recombination era assuming a standard Cosmological Constant Cold Dark Matter (ΛCDM) cosmology. However, the former requires a calibration with observables at nearby distances, while the latter is not a direct measurement and is model-dependent. The physics behind these aspects restrains our possibilities in selecting a calibration method that can help minimise the systematic effects or in considering a fixed cosmological model background. Anticipating the possibility of deeply exploring the physics of new nearby observables such as the recently detected black hole shadows, in this paper we propose standard rules to extend the studies related to these observables. Supermassive black hole shadows can be characterised by two parameters: the angular size of the shadow and the black hole mass. We found that it is possible to break the degeneracy between these parameters by forecasting and fixing certain conditions at high(er) redshifts, i.e., instead of considering the ≈10% precision from the EHT array, our results reach a ≈4%, a precision that could be achievable in experiments in the near future. Furthermore, we found that our estimations provide a value of H0=72.89±0.12 km/s/Mpc and, for the baryonic mass density, Ωm=0.275±0.002, showing an improvement in the values reported so far in the literature. We anticipate that our results can be a starting point for more serious treatments of the physics behind the SMBH shadow data as cosmological probes to relax tension issues.

Constraining the galaxy-halo connection of infrared-selected unWISE galaxies with galaxy clustering and galaxy-CMB lensing power spectra

We present the first detailed analysis of the connection between galaxies and their dark matter halos for the unWISE galaxy catalog -- a full-sky, infrared-selected sample built from WISE data, containing over 500 million galaxies. Using unWISE galaxy-galaxy auto-correlation and Planck CMB lensing-galaxy cross-correlation measurements down to 10 arcmin angular scales, we constrain the halo occupation distribution (HOD), a model describing how central and satellite galaxies are distributed within dark matter halos, for three unWISE} galaxy samples at mean redshifts $\bar{z} \approx 0.6$, $1.1$, and $1.5$. We constrain the characteristic minimum halo mass to host a central galaxy, $M_\mathrm{min}^\mathrm{HOD} = 1.83^{+0.41}_{-1.63} \times 10^{12} M_\odot/h$, $5.22^{+0.34}_{-4.80} \times 10^{12} M_\odot/h$, $6.60 ^{+0.30}_{-1.11} \times 10^{13} M_\odot/h$ for the unWISE samples at $\bar{z}\approx 0.6$, $1.1$, and $1.5$, respectively. We find that all three samples are dominated by central galaxies, rather than satellites. Using our constrained HOD models, we infer the effective linear galaxy bias for each unWISE sample, and find that it does not evolve as steeply with redshift as found in previous perturbation-theory-based analyses of these galaxies. We discuss possible sources of systematic uncertainty in our results, the most significant of which is the uncertainty on the galaxy redshift distribution. Our HOD constraints provide a detailed, quantitative understanding of how the unWISE galaxies populate the underlying dark matter halo distribution. These constraints will have a direct impact on future studies employing the unWISE galaxies as a cosmological and astrophysical probe, including measurements of ionized gas thermodynamics and dark matter profiles via Sunyaev-Zel'dovich and lensing cross-correlations.

Using the cosmological recombination radiation to probe early dark energy and fundamental constant variations

ABSTRACT The cosmological recombination radiation (CRR) is one of the guaranteed spectral distortion signals from the early Universe. The CRR photons from hydrogen and helium pre-date the last scattering process and as such allow probing physical phenomena in the pre-recombination era. Here, we compute the modifications to the CRR caused by early dark energy models and varying electromagnetic fundamental constants. These new physics examples have seen increased recent activity in connection with the Hubble tension, motivating the exploratory study presented here. The associated CRR responses are spectrally rich but the level of the signals is small. We forecast the possible sensitivity of future spectrometers to these effects. Our estimates demonstrate that the CRR directly depends to changes in the expansion history and recombination physics during the pre-recombination era. However, futuristic sensitivities are required for spectrometer-only constraints that are competitive with other cosmological probes. Nevertheless, measurements of the CRR can directly reach into phases that otherwise remain inaccessible, highlighting the potential these types of observations could have as a probe of the early Universe. A combination with Planck data further shows that a synergistic approach is very promising.

Importance of intracluster scattering and relativistic corrections from tSZ effect with cosmic infrared background

ABSTRACT The Sunyaev–Zeldovich effect towards clusters of galaxies has become a standard probe of cosmology. It is caused by the scattering of photons from the cosmic microwave background (CMB) by the hot cluster electron gas. In a similar manner, other photon backgrounds can be scattered when passing through the cluster medium. This problem has been recently considered for the radio and the cosmic infrared background. Here, we revisit the discussion of the cosmic infrared background (CIB) including several additional effects that were omitted before. We discuss the intracluster scattering of the CIB and the role of relativistic temperature corrections to the individual cluster and all-sky averaged signals. We show that the all-sky CIB distortion introduced by the scattering of the photon field was underestimated by a factor of ≃1.5 due to neglecting the intracluster scattering contribution. The CIB photons can scatter with the thermal electrons of both the parent halo or another halo, meaning that there are two ways to gain energy. Therefore, energy is essentially transferred twice from the thermal electrons to the CIB. We carefully clarify the origin of various effects in the calculation of the average CIB and also scattered signals. The single-cluster CIB scattering signal also exhibits a clear redshift dependence, which can be used in cosmological analyses, as we describe both analytically and numerically. This may open a new way for cosmological studies with future CMB experiments.

The Mira–Titan Universe – IV. High-precision power spectrum emulation

ABSTRACT Modern cosmological surveys are delivering data sets characterized by unprecedented quality and statistical completeness; this trend is expected to continue in the future as new ground- and space-based surveys come online. In order to maximally extract cosmological information from these observations, matching theoretical predictions are needed. At low redshifts, the surveys probe the non-linear regime of structure formation where cosmological simulations are the primary means of obtaining the required information. The computational cost of sufficiently resolved large-volume simulations makes it prohibitive to run very large ensembles. Nevertheless, precision emulators built on a tractable number of high-quality simulations can be used to build very fast prediction schemes to enable a variety of cosmological inference studies. We have recently introduced the Mira–Titan Universe simulation suite designed to construct emulators for a range of cosmological probes. This gravity-only set of simulations covers the standard six cosmological parameters {ωm, ωb, σ8, h, ns, w0} and, in addition, includes massive neutrinos and a dynamical dark energy equation of state {ων, wa}. In this paper, we present the final emulator for the matter power spectrum based on 111 cosmological simulations, each covering a (2.1 Gpc)3 volume and evolving 32003 particles. An additional set of 1776 lower resolution simulations and TimeRG perturbation theory results for the power spectrum are used to cover scales straddling the linear to mildly non-linear regimes (maximum wavenumber k = 5 Mpc−1). The emulator provides predictions at the 2–3 per cent level of accuracy over a wide range of cosmological parameters and is publicly released as part of this paper.

Cosmological constraint precision of photometric and spectroscopic multi-probe surveys of China Space Station Telescope (CSST)

ABSTRACT As a Stage IV space-based telescope, the China Space Station Telescope (CSST) can perform photometric and spectroscopic surveys simultaneously to explore the Universe efficiently in extreme precision. In this work, we investigate several powerful CSST cosmological probes, including cosmic shear, galaxy–galaxy lensing, photometric and spectroscopic galaxy clustering, and number counts of galaxy clusters, and study the capability of these probes by forecasting the results of joint constraints on the cosmological parameters. By referring to real observational results, we generate mock data and estimate the measured errors based on CSST observational and instrumental designs. To study systematic effects on the results, we also consider a number of systematics in CSST photometric and spectroscopic surveys, such as the intrinsic alignment, shear calibration uncertainties, photometric redshift uncertainties, galaxy bias, non-linear effects, instrumental effects, etc. The Fisher matrix method is used to derive the constraint results on the cosmological and systematic parameters from individual or joint surveys. We find that the joint constraints achieved by including all these CSST cosmological probes can significantly improve the results from current observations by one order of magnitude at least, which gives Ωm and σ8 <1 per cent accuracy and w0 and wa <5 and 20 per cent accuracy, respectively. This indicates that CSST photometric and spectroscopic multi-probe surveys could provide powerful tools with which to explore the Universe and greatly improve the studies of relevant cosmological problems.

Imprint of f(R) gravity in the cosmic magnification

ABSTRACT f(R) gravity is one of the simplest viable modifications to General Relativity: it passes local astrophysical tests, predicts both the early-time cosmic inflation and the late-time cosmic acceleration, and describes dark matter. In this paper, we probe cosmic magnification on large scales in f(R) gravity, using the well-known Hu-Sawicki model as an example. Our results indicate that at redshifts $z \, {\lt }\, 3$, values of the model exponent $n \, {\gt }\, 1$ lead to inconsistent behaviour in the evolution of the scalar perturbations. Moreover, when relativistic effects are taken into account in the large-scale analysis, our results show that as z increases, large-scale changes in the cosmic magnification angular power spectrum owing to integral values of n tend to share a similar pattern, while those of decimal values tend to share another. This feature could be searched for in the experimental data, as a potential ‘smoking gun’ for the given class of gravity models. Furthermore, we found that at $z \, {=}\, 1$ and lower, relativistic effects lead to a suppression of the cosmic magnification on large scales in f(R) gravity, relative to the concordance model; whereas, at $z \, {\gt }\, 1$, relativistic effects lead to a relative boost of the cosmic magnification. In general, relativistic effects enhance the potential of the cosmic magnification as a cosmological probe.