Planck Surveyor Research Articles

Deep Photometry of Suspected Gravitational Lensing Events: Potential Detection of a Cosmic String

Cosmic strings (CS) are one-dimensional cosmological-size objects predicted in realistic models of the early Universe. Analysis of the cosmic microwave background (CMB) anisotropy data from the Wilkinson Microwave Anisotropy Probe (WMAP) and Planck surveys revealed several CS candidates. One of the candidates, CSc-1, was found to be most reliable because of the statistically significant chains of gravitational lensing (GL) candidates in its field. We observed the brightest of the objects in the CSc-1 field, a galaxy pair SDSSJ110429.61+233150.3. The significant correlation between the spectra of the two components indicates the possible GL nature of the pair. Our simulations of observational data in the CSc-1 field shows that a large number of pairs can be explained by the complex geometry of the CS. Simulations of the SDSSJ110429 galaxy pair has shown that the observed angle between the components of the pair can be explained if the CS is strongly inclined and, possibly, bent in the image plane. In our preliminary data, we also detected the sign of the sharp isophotal edge in one image, which along with CMB and spectral data strongly suggests the possibility of a CS detection.

Optical Identification of Galaxy Clusters among SRG/eROSITA X-ray Sources Based on Photometric Redshift Estimates for Galaxies

We discuss an algorithm whereby the massive galaxy clusters detected in the SRG/eROSITA all-sky survey are identified and their photometric redshifts are estimated. For this purpose, we use photometric redshift estimates for galaxies and WISE forced photometry. To estimate the algorithm operation quality, we used a sample of 634 massive galaxy clusters from the Planck survey with known spectroscopic redshifts in the range 0,1zspec0,6. The accuracy of the photometric redshift estimates for this sample is bzphot/(1+zphot)=0,5%, the fraction of large deviations is 1.3%. We show that these large deviations arise mainly from the projections of galaxy clusters or other large-scale structures at different redshifts in the X-ray source field. Measuring the infrared (IR) luminosities of galaxy clusters allows one to estimate the reliability of the optical identification of the clusters detected in the SRG/eROSITA survey and to obtain an additional independent measurement of their total gravitational masses, M500. We show that the masses M500 of the galaxy clusters estimated from their IR luminosity measurements have an accuracy @logM500=0,124, comparable to the accuracy of the mass estimation for the galaxy clusters from their X-ray luminosities.

Understanding technological spillovers: The case of main astrophysics European missions

Due to the complexity and relevance of the scientific problems they address, astrophysical exploration missions can be a fertile ground for technological spillover.In the past, various space technologies, particularly in telecommunications, transportation, health care, and even military defense, spilled over or have been transferred from Space Agencies to industrial sectors. The boundaries between these two kind of actions are not always defined, for this reason we use the two concepts interchangeably. This article presents the results of a study on spillovers generated by six of the most important astrophysical missions launched by the European Space Agency in the first two decades of this century. These are notably: Integral, Planck Surveyor, XMM-Newton, Agile, Solar Orbiter, and Plato. In addition to some positive social effects, the results of the survey highlight the relevance of some technological innovations realized by small enterprises and then “transferred” to the industrial sector. The results also indicate the financial and organizational obstacles that could limit the possibility of transfer and thus the wider dissemination of innovations obtained in the development path of the Missions.

AGN feedback duty cycle in Planck SZ selected clusters using Chandra observations

ABSTRACT We present a systematic study of X-ray cavities using archival Chandra observations of nearby galaxy clusters selected by their Sunyaev–Zel’dovich (SZ) signature in the Planck survey, which provides a nearly unbiased mass-selected sample to explore the entire AGN feedback duty cycle. Based on X-ray image analysis, we report that 30 of the 164 clusters show X-ray cavities, which corresponds to a detection fraction of 18 per cent. After correcting for spatial resolution to match the high-$\mathit{ z}$ SPT-SZ sample, the detection fraction decreases to 9 per cent, consistent with the high-z sample, hinting that the AGN feedback has not evolved across almost 8 Gyrs. Our finding agrees with the lack of evolution of cool-core clusters fraction. We calculate the cavity power, Pcav, and find that most systems of our sample have enough AGN heating to offset the radiative losses of the intracluster medium.

On inflationary parameters in scalar–tensor theories

The equivalence between [Formula: see text] and scalar–tensor theories is revisited, we consequently explored different [Formula: see text] models. After consideration of specific definition of the scalar field, we derived the potentials [Formula: see text] for each [Formula: see text] model focusing on the early Universe, mostly the inflation epoch. For a given potential, we applied the slow-roll approximation approach to each [Formula: see text] model and obtained the expressions for the spectral index [Formula: see text] and tensor-to-scalar ratio [Formula: see text]. We determined the corresponding numerical values associated with each of the [Formula: see text] models. Our results showed that for certain choice of parameter space, the values of [Formula: see text] and [Formula: see text] are consistent with the Planck survey results and others produce numerical values that are in the same range as suggested by Planck data. We further constructed the Klein–Gordon equations (KGEs) of each [Formula: see text] model. We found numerical solutions to each KGE considering different values of free parameters and initial conditions of each [Formula: see text] model. All models showed that the scalar field decreases as time increases, an indication that there is less content of the scalar field in the late Universe.

Decomposing magnetic fields in three dimensions over the central molecular zone

ABSTRACT Measuring magnetic fields in the interstellar medium and obtaining their distribution along line-of-sight (LOS) is very challenging with the traditional techniques. The Velocity Gradient Technique (VGT), which utilizes anisotropy of magnetohydrodynamic turbulence, provides an attractive solution. Targeting the central molecular zone (CMZ), we test this approach by applying the VGT to $\rm ^{12}CO$ and $\rm ^{13}CO$ (J = 1–0) data cubes. We first used the scousepy algorithm to decompose the CO line emissions into separate velocity components, and then we constructed pseudo-Stokes parameters via the VGT to map the plane-of-the-sky magnetic fields in three-dimension. We present the decomposed magnetic field maps and investigate their significance. While the LOS integrated magnetic field orientation is shown to be consistent with the polarized dust emission from the Planck survey at 353 GHz, individual velocity components may exhibit different magnetic fields. We present a scheme of magnetic field configuration in the CMZ based on the decomposed magnetic fields. In particular, we observe a nearly vertical magnetic field orientation in the dense clump near the Sgr B2 and a change in the outflow regions around the Sgr A*. Two high-velocity structures associated with an expanding ring in the CMZ show distinct swirling magnetic field structures. These results demonstrate the potential power of the VGT to decompose velocity or density-dependent magnetic structures.

Search for candidate strongly lensed dusty galaxies in the Planck satellite catalogues

The shallow, all-sky Planck surveys at sub-millimetre wavelengths have detected the brightest strongly gravitationally lensed dusty galaxies in the sky. The combination of their extreme gravitational flux-boosting and image-stretching offers the unique possibility of measuring in extraordinary detail the galaxy structure and kinematics in early evolutionary phases through high-resolution imaging and spectroscopic follow-up. This enables us to gain otherwise unaccessible direct information on physical processes in action. However, the extraction of candidate strongly lensed galaxies from Planck catalogues is hindered by the fact that they are generally detected with a poor signal-to-noise ratio, except for the few brightest galaxies. Their photometric properties are therefore strongly blurred, which makes them very difficult to single out. We have devised a method capable of increasing the number of identified Planck-detected strongly lensed galaxies by a factor of about three to four, although with an unavoidably limited efficiency. Our approach exploits the fact that the sub-millimetre colours of strongly lensed galaxies are definitely colder than those of nearby dusty galaxies, which constitute the overwhelming majority of extragalactic sources detected by Planck. The sub-millimetre colours of the 47 confirmed or very likely Planck-detected strongly lensed galaxies have been used to estimate the colour range spanned by objects of this type. Moreover, most nearby galaxies and radio sources can be confirmed by cross-matching with the IRAS and PCNT catalogues, respectively. We present samples of lensed candidates selected at 545, 857, and 353 GHz, comprising 177, 97, and 104 sources, respectively. The efficiency of our approach, tested by exploiting data from the SPT survey covering ≃2500 deg2, is estimated to be in the range 30%−40%. We also discuss stricter selection criteria to increase the estimated efficiency to ≃50%, at the cost of a somewhat lower completeness. Our analysis of SPT data has identified a dozen galaxies that can reliably be considered previously unrecognized Planck-detected strongly lensed galaxies. Extrapolating the number of Planck-detected confirmed or very likely strongly lensed galaxies found within the SPT and H-ATLAS survey areas, we expect ≃150 to ≃190 such sources over the full |b|> 20° sky.

Local patch analysis for testing statistical isotropy of the Planck convergence map

The small but measurable effect of weak gravitational lensing on the cosmic microwave background radiation provide information about the large-scale distribution of matter in the universe.We use the all sky distribution of matter, as represented by the convergence map that is inferred from CMB lensing measurement by Planck survey, to test the fundamental assumption of Statistical Isotropy (SI) of the universe. For the analysis we use the α statistic that is devised from the contour Minkowski tensor, a tensorial generalization of the scalar Minkowski functional, the contour length. In essence, the α statistic captures the ellipticity of iso-field contours at any chosen threshold value of a smooth random field and provides a measure of anisotropy.The SI of the observed convergence map is tested against the suite of realistic simulations of the convergence map provided by the Planck collaboration.We first carry out a global analysis using the full sky data after applying the galactic and point sources mask. We find that the observed data is consistent with SI.Further we carry out a local search for departure from SI in small patches of the sky using α. This analysis reveals several sky patches which exhibit deviations from simulations with statistical significance higher than 95% confidence level (CL). Our analysis indicates that the source of the anomalous behaviour of most of the outlier patches is inaccurate estimation of noise. We identify two outlier patches which exhibit anomalous behaviour originating from departure from SI at higher than 95% CL. Most of the anomalous patches are found to be located roughly along the ecliptic plane or in proximity to the ecliptic poles.

Predicting the Curvature of the Cosmos, and Point of Volume Contraction in a Big Bounce Scenario

Based on the latest Planck surveys, the universe is close to being remarkably flat, and yet, within observational error, there is still room for a slight curvature. If the curvature is positive, then this would lead to a closed universe, as well as allow for a big bounce scenario. Working within these assumptions, and using a simple model, we predict that the cosmos may have a positive curvature in the amount, Ω0=1.001802, a value within current observational bounds. For the scaling laws associated with the density parameters in Friedmann’s equations, we will assume a susceptibility model for space, where, , equals the smeared cosmic susceptibility. If we allow the to decrease with increasing cosmic scale parameter, “a”, then we can predict a maximum Hubble volume, with minimum CMB temperature for the voids, before contraction begins, as well as a minimum volume, with maximum CMB temperature, when expansion starts. A specific heat engine model for the cosmos is also entertained for this model of a closed universe.

Galaxy Cluster Contribution to the Diffuse Extragalactic Ultraviolet Background

Abstract The diffuse ultraviolet background radiation has been mapped over most of the sky with 2′ resolution using data from the Galaxy Evolution Explorer survey. We utilize this map to study the correlation between the UV background and clusters of galaxies discovered via the Sunyaev–Zeldovich effect in the Planck survey. We use only high Galactic latitude ( ) galaxy clusters to avoid contamination by Galactic foregrounds, and we only analyze clusters with a measured redshift. This leaves us with a sample of 142 clusters over the redshift range of 0.02 ≤ z ≤ 0.72, which we further subdivide into four redshift bins. In analyzing our stacked samples binned by redshift, we find evidence for a central excess of UV background light compared to local backgrounds for clusters with z < 0.3. We then stacked these z < 0.3 clusters to find a statistically significant excess of 12 ± 2.3 photon cm−2 s−1 sr−1 Å−1 over the median of ∼380 photon cm−2 s−1 sr−1 Å−1 measured around random blank fields. We measure the stacked radial profile of these clusters, and find that the excess UV radiation decays to the level of the background at a radius of ∼1 Mpc, roughly consistent with the maximum radial extent of the clusters. Analysis of possible physical processes contributing to the excess UV brightness indicates that non-thermal emission from relativistic electrons in the intracluster medium and faint, unresolved UV emission from cluster member galaxies and intracluster light are likely the dominant contributors.

The Galactic Faraday depth sky revisited

Context. The Galactic Faraday depth sky is a tracer for both the Galactic magnetic field and the thermal electron distribution. It was previously reconstructed from polarimetric measurements of extra-Galactic point sources. Aims. Here we improve on these works by using an updated inference algorithm and by taking into account the electron emission measure as traced by free–free emission measured by the Planck survey. In the future the data situation will improve drastically thanks to the next generation Faraday rotation measurements from the SKA and its pathfinders. Anticipating this, a further aim of this paper is to update the map reconstruction method with some of the latest developments in Bayesian imaging. Methods. To this end we made use of information field theory, an inference scheme that is particularly powerful in cases of noisy and incomplete data. Results. We demonstrate the validity of the new algorithm by applying it to an existing data compilation. Even though we used exactly the same data set, a number of novel findings are made; for example, a non-parametric reconstruction of an overall amplitude field resembles the free–free emission measure map of the Galaxy. Folding this emission measure map into the analysis provides more detailed predictions. The joint inference enables us to identify regions with deviations from the assumed correlations between the emission measure and Faraday data, thereby pointing us to Galactic structures with distinguishably different physics. We find evidence for an alignment of the magnetic field within the lines of sight along both directions of the Orion arm.

Multifrequency Study of GHz-peaked Spectrum Sources

Gigahertz-Peaked spectrum (GPS) sources are compact active galactic nuclei, presumably young precursors of bright radio sources. The study of GPS radio properties provides information about the features of synchrotron radiation in extragalactic sources. Also in applied research GPS sources are useful as compact stationary radio sources in the sky for astrometric purposes. This paper presents the results of a multifrequency GPS study based on quasi-simultaneous measurements with the RATAN-600 radio telescope during the 2006-2017. The catalog containing spectral flux densities measured at six frequencies (1.1, 2.3, 4.8, 7.7/8.2, 11.2, and 21.7 GHz) have been obtained. In addition, for the analysis of radio spectra, data from the following low-frequency surveys have been used: GLEAM (GaLactic and Extragalactic All-sky Murchison widefield array survey) and TGSS (Tata institute for fundamental research GMRT Sky Survey) and high-frequency measurements from Planck survey. A total number of 164 GPS and candidates to GPS have been identified (17 of them are new discoveries), which makes up a small fraction of GPS in the initial sample of bright AGNs, about 2%. The physical properties and formation conditions of synchrotron radiation is found to be quite different in GPS of different AGN types. The deficit of distant GPS ($z > 2$) with low maximum frequencies (less than 1 GHz) is confirmed. The existing 'size - peak frequency' anticorrelation is continuous. The continuum radio spectra are found to become statistically steeper with increasing redshift.

Relation between X-ray and Sunyaev—Zeldovich Galaxy Cluster Mass Measurements

We investigate the possibility of transferring the galaxy cluster mass scale calibrations from weak-lensing measurements to X-ray cluster mass measurements using Planck cluster mass measurements. For this purpose, we compare the mass measurements for 47 galaxy clusters that simultaneously enter the X-ray sample of clusters from Vikhlinin et al. (2009a, 2009b) and the sample of galaxy clusters from the second Planck catalogue of Sunyaev-Zeldovich sources. We show that except for a few outliers in the measurements, most of which arise from cluster projection effects in the Planck data, the scatter in the mass ratio turns out to be small, ~15%, while the accuracy of determining the mean mass ratio for this sample is about 2%. This allows the existing cluster mass measurement calibrations in the Planck survey to be transferred to Chandra X-ray mass measurements almost without any loss of accuracy. Using the derived relations and based on new cluster mass scale calibrations from weak-lensing measurements in clusters, we have obtained corrections to the constraints on cosmological parameters from Vikhlinin et al. (2009b). Given these corrections, σ8 increases approximately by 4%, within one standard deviation of the uncertainty in the constraint on this quantity at constant Ωm. We show that, given the systematic uncertainties, all of the currently available galaxy cluster mass function measurements yield approximately identical constraints on the parameters σ8 and Ωm.

The Splashback Radius of Planck SZ Clusters*

Abstract We present evidence for the existence of the splashback radius in galaxy clusters selected using the Sunyaev–Zeldovich effect, a sample unaffected by systematics related to cluster finding in the optical wavelength range. We show that the deprojected cross-correlation of galaxy clusters found in the Planck survey with galaxies detected photometrically in the Pan-STARRS survey shows a sharp steepening feature (a logarithmic slope steeper than −3), which we associate with the splashback radius. We infer the 3D splashback radius for the SZ cluster sample to be , where the cluster sample has an average halo mass of M 500c = 3.0 × 1014 at an average redshift of z = 0.18. The inferred value of the splashback radius appears marginally consistent with the expected location for dark matter halos in the standard cold dark matter paradigm. However, given the limited precision of our measurements, we cannot conclusively confirm or rule out the smaller splashback radius measured so far in the literature for optically selected galaxy clusters. We show that the splashback radius does not depend on the galaxy magnitude for galaxies fainter than and is present at a consistent location in galaxy populations divided by color. The presence of the splashback radius in the star-forming galaxy population could potentially be used to put lower limits on the quenching timescales for galaxies. We can marginally rule out the contamination of the star-forming galaxy sample by quenched galaxies, but the results would need further verification with deeper data sets.

Inflationary universe in F(R) gravity with antisymmetric tensor fields and their suppression during its evolution

The intriguing question, why the present scale of the universe is free from any perceptible footprints of rank-2 antisymmetric tensor fields? (generally known as Kalb-Ramond fields) is addressed. A quite natural explanation of this issue is given from the angle of higher-curvature gravity, both in four- and in five-dimensional spacetime. The results here obtained reveal that the amplitude of the Kalb-Ramond field may be actually large and play a significant role during the early universe, while the presence of higher-order gravity suppresses this field during the cosmological evolution, so that it eventually becomes negligible in the current universe. Besides the suppression of the Kalb-Ramond field, the extra degree of freedom in $F(R)$ gravity, usually known as scalaron, also turns out to be responsible for inflation. Such F(R) gravity with Kalb-Ramond fields may govern the early universe to undergo an inflationary stage at early times (with the subsequent graceful exit) for wider range of F(R) gravity than without antisymmetric fields.. Furthermore, the models---in four- and five-dimensional spacetimes---are linked to observational constraints, with the conclusion that the corresponding values of the spectral index and tensor-to-scalar ratio closely match the values provided by the Planck survey 2018 data.

Predicting Dark Energy Survey Results Using the Flat Space Cosmology Model

The Flat Space Cosmology (FSC) model is utilized to show how this model predicts the value of the Hubble parameter at each epoch of cosmic expansion. Specific attention in this paper is given to correlating the observable galactic redshifts since the beginning of the “cosmic dawn” reionization epoch. A graph of the log of the Hubble parameter as a function of redshift z is presented as the FSC prediction of the pending Dark Energy Survey results. In the process, it is discovered that the obvious tension between the SHOES local Hubble constant value and the 2018 Planck Survey and the 2018 Dark Energy Survey global Hubble constant values may be explained by a time-variable, scalar, Hubble parameter acting in accordance with the FSC model.

The Clusters Hiding in Plain Sight (CHiPS) Survey: A First Discovery of a Massive Nearby Cluster around PKS 1353−341

Abstract We introduce the first result of the Clusters Hiding in Plain Sight (CHiPS) survey, which aims to discover new nearby massive galaxy clusters that were incorrectly identified as isolated point sources in the ROSAT All-sky Survey. We present a Chandra X-ray observation of our first newly discovered low-redshift (z = 0.223) galaxy cluster with a central X-ray bright point source, PKS 1353−341. After removing the point source contribution to the cluster core (L nuc ∼ 1.8 × 1044 erg s−1), we determine various properties of the cluster. The presence of a relaxed X-ray morphology, a central temperature drop, and a central cooling time around 400 Myr indicates that it is a strong cool-core cluster. The central galaxy appears to be forming stars at the rate of 6.2 ± 3.6 M ⊙ yr−1, corresponding to ∼1% of the classical cooling prediction. The supermassive black hole in the central galaxy appears to be accreting at ∼0.1% of the Eddington rate with a total power output of ∼5 × 1045 erg s−1, split nearly equally between radiative and mechanical power. We see weak evidence of localized excess entropy at a radius of 200 kpc, which, if true, could imply a recent (∼180 Myr) energetic outburst in the core that has risen buoyantly to a larger radius. Comparing the cluster’s bulk properties with those of other known clusters (e.g., the total mass M 500 is , and the bolometric X-ray luminosity L X is 7 × 1044 erg s−1), we show that this cluster, which is massive enough that it was detected (but not confirmed) by the Planck survey, is also sufficiently luminous that it would have been identified as a cluster in the ROSAT All-sky Survey if it did not have such a bright central point source. This discovery demonstrates the potential of the CHiPS survey to find massive nearby clusters with extreme central properties that may have been missed or misidentified by previous surveys.

A matched filter approach for blind joint detection of galaxy clusters in X-ray and SZ surveys

The combination of X-ray and Sunyaev–Zeldovich (SZ) observations can potentially improve the cluster detection efficiency, when compared to using only one of these probes, since both probe the same medium, the hot ionized gas of the intra-cluster medium. We present a method based on matched multifrequency filters (MMF) for detecting galaxy clusters from SZ and X-ray surveys. This method builds on a previously proposed joint X-ray–SZ extraction method and allows the blind detection of clusters, that is finding new clusters without knowing their position, size, or redshift, by searching on SZ and X-ray maps simultaneously. The proposed method is tested using data from the ROSAT all-sky survey and from the Planck survey. The evaluation is done by comparison with existing cluster catalogues in the area of the sky covered by the deep SPT survey. Thanks to the addition of the X-ray information, the joint detection method is able to achieve simultaneously better purity, better detection efficiency, and better position accuracy than its predecessor Planck MMF, which is based on SZ maps alone. For a purity of 85%, the X-ray–SZ method detects 141 confirmed clusters in the SPT region; to detect the same number of confirmed clusters with Planck MMF, we would need to decrease its purity to 70%. We provide a catalogue of 225 sources selected by the proposed method in the SPT footprint, with masses ranging between 0.7 and 14.5 ×1014 M⊙ and redshifts between 0.01 and 1.2.

Dark matter distribution in X-ray luminous galaxy clusters with Emergent Gravity

Abstract We present the radial distribution of the dark matter in two massive, X-ray luminous galaxy clusters, Abell 2142 and Abell 2319, and compare it with the quantity predicted as apparent manifestation of the baryonic mass in the context of the ‘Emergent Gravity’ scenario, recently suggested from Verlinde. Thanks to the observational strategy of the XMM–Newton Cluster Outskirt Programme (X-COP), using the X-ray emission mapped with XMM–Newton and the Sunyaev–Zel'dovich signal in the Planck survey, we recover the gas density, temperature and thermal pressure profiles up to ∼R200, allowing us to constrain at an unprecedented level the total mass through the hydrostatic equilibrium equation. We show that, also including systematic uncertainties related to the X-ray-based mass modelling, the apparent ‘dark’ matter shows a radial profile that has a shape different from the traditional dark matter distribution, with larger discrepancies (by a factor of 2–3) in the inner (r < 200 kpc) cluster's regions and a remarkable agreement only across R500.

Modelling and simulation of large-scale polarized dust emission over the southern Galactic cap using the GASS Hi data

The Planck survey has quantified polarized Galactic foregrounds and established that they are a main limiting factor in the quest for the cosmic microwave background B-mode signal induced by primordial gravitational waves during cosmic inflation. Accurate separation of the Galactic foregrounds therefore binds this quest to our understanding of the magnetized interstellar medium. The two most relevant empirical results from analysis of Planck data are line of sight depolarization arising from fluctuations of the Galactic magnetic field orientation and alignment of filamentary dust structures with the magnetic field at high Galactic latitude. Furthermore, Planck and H I emission data in combination indicate that most of the filamentary dust structures are in the cold neutral medium. The goal of this paper is to test whether these salient observational results, taken together, can account fully for the statistical properties of the dust polarization over a selected low column density region comprising 34% of the southern Galactic cap (b ≤ −30°). To do this, we construct a dust model that incorporates H I column density maps as tracers of the dust intensity structures and a phenomenological description of the Galactic magnetic field. By adjusting the parameters of the dust model, we were able to reproduce the Planck dust observations at 353GHz in the selected region. Realistic simulations of the polarized dust emission enabled by such a dust model are useful for testing the accuracy of component separation methods, studying non-Gaussianity, and constraining the amount of decorrelation with frequency.