Astrophysics

Generation of magnetic field during inflation can explain its presence over a wide range of scales in the Universe. In Ref.\cite{sharma2017}, we proposed a model to generate these fields during inflation. These fields have nonzero anisotropic stress which lead to the generation of a stochastic background of gravitational waves (GW) in the early universe. Here we show that for a scenario of magnetogenesis where reheating takes place around QCD epoch, this stochastic GW background lies in the 95% confidence region of the GW signal probed by NANOGrav collaboration. This is the case when the generated electromagnetic field (EM) energy density is 3??0% of the background energy density at the end of reheating. For this case, the values of magnetic field strength B 0 ??3.8??.9)? 10 ??1 G and its coherence length ??0 kpc at the present epoch. These values are for the models in which EM fields are of nonhelical nature. For the helical nature of the fields, these values are B 0 ??1.1??.9)? 10 ?? G and its coherence length ??.8 Mpc.

We propose a new reionization probe that uses cosmic microwave background (CMB) observations: the cross-correlation between fluctuations in the CMB optical depth which probes the integrated electron density, δ? , and the Compton y -map which probes the integrated electron pressure. This cross-correlation is much less contaminated than the y -map power spectrum by late-time cluster contributions; in addition, this cross-correlation can constrain the temperature of ionized bubbles while the optical-depth fluctuations and kinetic SZ effect can not. We measure this new observable using a Planck y -map as well as a map of optical-depth fluctuations that we reconstruct from Planck CMB temperature data. We use our measurements to derive a first CMB-only upper limit on the temperature inside ionized bubbles, T b ??.0? 10 5 K ( 2? ). We also present future forecasts, assuming a fiducial model with characteristic reionization bubble size R b =5 Mpc and T b =5? 10 4 K. The signal-to-noise ratio of the fiducial cross-correlation using a signal dominated PICO-like y -map becomes ?? with CMB-S4 δ? and ??3 with CMB-HD δ? . For the fiducial model, we predict that the CMB-HD ??PICO cross-correlation should achieve an accurate measurement of the reionization parameters: T b ??49800 +4500 ??100 K and R b ??5.09 +0.66 ??.79 Mpc. Since the power spectrum of the electron density fluctuations is constrained by the δ? auto spectrum, the temperature constraints should be only weakly model-dependent on the details of the electron distributions and should be statistically representative of the temperature in ionized bubbles during reionization. This cross-correlation could, therefore, become an important observable for future CMB experiments.

The kinematic Sunyaev-Zel'dovich (kSZ) effect -- the Doppler boosting of cosmic microwave background (CMB) photons scattering off free electrons with non-zero line-of-sight velocity -- is an excellent probe of the distribution of baryons in the Universe. In this paper, we measure the kSZ effect due to ionized gas traced by infrared-selected galaxies from the \emph{unWISE} catalog. We employ the "projected-field" kSZ estimator, which does not require spectroscopic galaxy redshifts. To suppress non-kSZ foreground signals associated with the galaxies (e.g., dust emission and thermal SZ), this estimator requires cleaned CMB maps, which we obtain from \emph{Planck} and \emph{WMAP} data. Using a new "asymmetric" estimator that combines different foreground-cleaned CMB maps to maximize the signal-to-noise, we measure the kSZ 2 -galaxy cross-power spectrum for three subsamples of the \emph{unWISE} galaxy catalog, which peak at mean redshifts z??0.6, 1.1, and 1.5, have average halo mass ?? - 5? 10 13 h ?? M ??, and in total contain over 500 million galaxies. After marginalizing over CMB lensing contributions, we measure the amplitude of the kSZ signal A kS Z 2 =0.42±0.31 , 5.02±1.01 , and 8.23±3.23 , for the three subsamples, where A kS Z 2 =1 corresponds to our fiducial model. The combined kSZ detection S/N > 5. We discuss possible explanations for the excess kSZ signal associated with the z??.1 sample, and show that foreground contamination in the CMB maps is very unlikely to be the cause. Our measurements illustrate clearly that no baryons are missing on large scales at low redshifts.

We present forecasted cosmological constraints from combined measurements of galaxy cluster abundances from the Simons Observatory and galaxy clustering from a DESI-like experiment on two well-studied modified gravity models, the chameleon-screened f(R) Hu-Sawicki model and the nDGP braneworld Vainshtein model. A Fisher analysis is conducted using ? 8 constraints derived from thermal Sunyaev-Zel'dovich (tSZ) selected galaxy clusters, as well as linear and mildly non-linear redshift-space 2-point galaxy correlation functions. We find that the cluster abundances drive the constraints on the nDGP model while f(R) constraints are led by galaxy clustering. The two tracers of the cosmological gravitational field are found to be complementary, and their combination significantly improves constraints on the f(R) in particular in comparison to each individual tracer alone. For a fiducial model of f(R) with log 10 ( f R0 )=?? and n=1 we find combined constraints of ?( log 10 ( f R0 ))=0.48 and ?(n)=2.3 , while for the nDGP model with n nDGP =1 we find ?( n nDGP )=0.087 . Around a fiducial General Relativity (GR) model, we find a 95% confidence upper limit on f(R) of f R0 ??.68? 10 ?? . Our results present the exciting potential to utilize upcoming galaxy and CMB survey data available in the near future to discern and/or constrain cosmic deviations from GR.

We report here the results of an Effective Field Theory (EFT) WIMP search analysis using LUX data. We build upon previous LUX analyses by extending the search window to include nuclear recoil energies up to ??180 keV nr , requiring a reassessment of data quality cuts and background models. In order to use a binned Profile Likelihood statistical framework, the development of new analysis techniques to account for higher-energy backgrounds was required. With a 3.14 ? 10 4 kg ??day exposure using data collected between 2014 and 2016, we set 90\% C.L. exclusion limits on non-relativistic EFT WIMP couplings to neutrons and protons, providing the most stringent constraints on a significant fraction of the possible EFT WIMP interactions. Additionally, we report world-leading exclusion limits on inelastic EFT WIMP-nucleon recoils.

Large-scale coherent magnetic fields in the intergalactic medium are presumed to play a key role in the formation and evolution of the cosmic web, and in large scale feedback mechanisms. However, they are theorized to be extremely weak, in the nano-Gauss regime. To search for a statistical signature of these weak magnetic fields we perform a cross-correlation between the Faraday rotation measures of 1742 radio galaxies at z>0.5 and large-scale structure at 0.1<z<0.5 , as traced by 18 million optical and infrared foreground galaxies. No significant correlation signal was detected within the uncertainty limits. We are able to determine model-dependent 3? upper limits on the parallel component of the mean magnetic field strength of filaments in the intergalactic medium of ??0 nG for coherence scales between 1 and 2.5 Mpc , corresponding to a mean upper bound RM enhancement of ??.8 rad/ m 2 due to filaments along all probed sight-lines. These upper bounds are consistent with upper bounds found previously using other techniques. Our method can be used to further constrain intergalactic magnetic fields with upcoming future radio polarization surveys.

Measurements for strong gravitational lensing time delays between multiple images of background quasars can provide an independent probe to explore the expansion history of the late-time universe. In this paper, we employ the new results of the time-delay (TD) measurements for six strong gravitational lens systems to constrain interacting dark energy (IDE) model. We mainly focus on the model of vacuum energy (with w=?? ) interacting with cold dark matter, and consider four typical cases of the interaction form. Our main findings include: (i) the IDE models with Q??? de have an advantage in alleviating the H 0 tension between the cosmic microwave background and TD observations; (ii) when the TD data are combined with the latest local distance-ladder result, the H 0 tension can be alleviated from 5.3? (in the standard ? CDM cosmology) to 1.7? in the IDE model with the interaction term Q=βH ? de ; (iii) the coupling parameter β in all the considered IDE models are preferred to be positive around 1 ? range when the late-universe measurements (TD+SN) are used to perform constraint, implying a mild preference for the case of cold dark matter decaying into dark energy by the late-universe observations.

In this paper I compare the quality of the fit of a simple power law model of cosmic expansion to the standard ? CDM model. I analyze a data set consisting of cosmic chronometer, standard ruler, and standard candle measurements, finding that the ? CDM model provides a better fit to most combinations of these data than does the power law model

The recent observations of the global 21cm signal by EDGES and gravitational waves by LIGO/VIGO have revived interest in PBHs. Different from previous works, we investigate the influence of PBHs on the evolution of the IGM for the mass range 6× 10 13 g≲ M PBH ≲3× 10 14 g . Since the lifetime of these PBHs is smaller than the present age of the Universe, they have evaporated by the present day. Due to Hawking radiation, the heating effects of PBHs on the IGM can suppress the absorption amplitude of the global 21cm signal. In this work, by requiring that the differential brightness temperature of the global 21cm signals in the redshift range of 10≲z≲30 , e.g., δ T b ≲−100 mK , we obtain upper limits on the initial mass fraction of PBHs. We find that the strongest upper limit is β PBH ∼2× 10 −30 . Since the formation of PBHs is related to primordial curvature perturbations, by using the constraints on the initial mass fraction of PBHs we obtain the upper limits on the power spectrum of primordial curvature perturbations for the scale range 8.0× 10 15 ≲k≲1.8× 10 16 Mp c −1 , corresponding to the mass range considered here. We find that the strongest upper limit is P R (k)∼0.0046 . By comparing with previous works, we find that for the mass range (or the scale range) investigated in this work the global 21cm signals or the 21cm power spectrum should give the strongest upper limits on the initial mass fraction of PBHs and on the power spectrum of primordial curvature perturbations.

Extracting the bispectrum information from the large scale structure observations is challenging due to the complex models and the computational costs to measure the signal and its covariance. Recently, the skew spectrum was proposed to access parts of the bispectrum information with a more effective way and has been confirmed it can provide complementary information to that enclosed in the power spectrum measurements. In this work, we generalize the theory to apply the multitracer technique and explore its ability to constrain the local type primordial non-Gaussianity. Using the spectra and their covariance estimated from N -body simulations, we find the multitracer approach is effective to reduce the cosmic variance noise. The 1σ marginalized errors for b 2 1 A s , n s and f loc NL are reduced by 50\%, 52\% and 73\% comparing with the results using only power spectrum obtained from a single tracer. It indicate that both the skew spectrum and the multitracer technique are useful to constrain the primordial non-Gaussianity with the forthcoming wide-field galaxy surveys.