Galaxy clusters are connected at their peripheries to the large-scale structures by cosmic filaments that funnel accreting material. These filamentary structures are studied to investigate both ...environment-driven galaxy evolution and structure formation and evolution. In the present work, we probe in a statistical manner the azimuthal distribution of galaxies around clusters as a function of the cluster-centric distance, cluster richness, and star-forming or passive galaxy activity. We performed a harmonic decomposition in large photometric galaxy catalogue around 6400 SDSS clusters with masses
M
> 10
14
solar masses in the redshift range of 0.1 <
z
< 0.3. The same analysis was performed on the mock galaxy catalogue from the light cone of a Magneticum hydrodynamical simulation. We used the multipole analysis to quantify asymmetries in the 2D galaxy distribution. In the inner cluster regions at
R
< 2
R
500
, we confirm that the galaxy distribution traces an ellipsoidal shape, which is more pronounced for richest clusters. In the outskirts of the clusters (
R
= 2 − 8
R
500
), filamentary patterns are detected in harmonic space with a mean angular scale
m
mean
= 4.2 ± 0.1. Massive clusters seem to have a larger number of connected filaments than lower-mass clusters. We also find that passive galaxies appear to trace the filamentary structures around clusters better. This is the case even if the contribution of star-forming galaxies tends to increase with the cluster-centric distance, suggesting a gradient of galaxy activity in filaments around clusters.
We present a mass estimate of the Planck-discovered cluster PLCK G100.2-30.4, derived from a weak lensing analysis of deep Subaru griz images. We perform a careful selection of the background ...galaxies using the multi-band imaging data, and undertake the weak lensing analysis on the deep (1 h) r −band image. The shape measurement is based on the Kaiser-Squires-Broadhurst algorithm; we adopt the PSFex software to model the point spread function (PSF) across the field and correct for this in the shape measurement. The weak lensing analysis is validated through extensive image simulations. We compare the resulting weak lensing mass profile and total mass estimate to those obtained from our re-analysis of XMM-Newton observations, derived under the hypothesis of hydrostatic equilibrium. The total integrated mass profiles agree remarkably well, within 1σ across their common radial range. A mass M500 ~ 7 × 1014M⊙ is derived for the cluster from our weak lensing analysis. Comparing this value to that obtained from our reanalysis of XMM-Newton data, we obtain a bias factor of (1−b) = 0.8 ± 0.1. This is compatible within 1σ with the value of (1-b) obtained in Planck 2015 from the calibration of the bias factor using newly available weak lensing reconstructed masses.
We investigate the potential of next-generation surveys of the cosmic microwave background and large-scale structure, to constrain the nature of dark energy, by means of the cross-correlation of the ...Integrated Sachs-Wolfe effect with the galaxy distribution. We first complete a signal-to-noise analysis to decide the most appropriate properties of a survey required to detect the correlated signal at a significance level of higher than 4σ. We find that more than 35% of the sky should be covered, the galaxy distribution should be probed out to a median redshift higher than 0.8, and the number of galaxies detected should be higher than a few per squared arcmin. We then consider in particular forthcoming surveys DUNE, LSST, SNAP, PanSTARRS. We independently compute the constraints that the DUNE survey can place on the nature of dark energy, by means of different parametrisations of its equation of state, using a standard Fisher matrix analysis. We confirm that, with respect to limits placed by pure CMB, cross-correlation constraints can help to break the degeneracies between dark energy and cosmological parameters. The strength of the constraints is not, of course, independent of the dark-energy model. The constraints are complementary to, despite being weaker than, some other probes of dark energy such as gravitational weak-lensing, because they are sensitive to the high-redshift behaviour of the dark energy.
Using the publicly available eROSITA Final Equatorial Depth Survey (eFEDS) data, we detected the stacked X-ray emissions at the position of 463 filaments at a significance of 3.8
σ
based on the ...combination of all energy bands. In parallel, we found that the probability of the measurement under the null hypothesis is ∼0.0017. The filaments were identified with galaxies in the Sloan Digital Sky Survey survey, ranging from 30 Mpc to 100 Mpc in length at 0.2 <
z
< 0.6. The stacking of the filaments was performed with the eFEDS X-ray count-rate maps in the energy range between 0.4 and 2.3 keV after masking the resolved galaxy groups and clusters and the identified X-ray point sources from the ROSAT,
Chandra
,
XMM-Newton
, and eROSITA observations. In addition, diffuse X-ray foreground and background emissions or any residual contribution were removed by subtracting the signal in the region between 10 and 20 Mpc from the filament spines. For the stacked signal, we performed an X-ray spectral analysis, which indicated that the signal is associated with a thermal emission. According to a model with the astrophysical plasma emission code for the plasma emission and with a
β
-model gas distribution with
β
= 2/3, the detected X-ray signal can be interpreted as emission from hot gas in the filaments with an average gas temperature of 1.0
−0.2
+0.3
keV and a gas overdensity of 21 ± 5 at the center of the filaments.
About 2100 star-forming galaxy protocluster candidates at
z
∼ 1 − 4 were identified at sub-millimetre wavelengths in the
Planck
all-sky survey. Follow-up spectroscopic observations of a few ...candidates have confirmed the presence of actual galaxy overdensities with large star formation rates (SFRs). In this work, we use state-of-the-art hydrodynamical simulations to investigate whether the
Planck
high-
z
sub-millimetre sources (PHz) are progenitors of massive clusters at
z
= 0. To match the PHz sources with simulated halos, we select the most star-forming (SF) halos in 19 redshift bins from
z
= 3 to
z
= 1.3 in the TNG300 simulation of the IllustrisTNG project. At each redshift, the total SFR of the simulated protocluster candidates is computed from the SFR of all the galaxies within an aperture corresponding to the
Planck
beam size, including those along the line of sight (LOS). The simulations reproduce the
Planck
-derived SFRs as the sum of both the SFR of at least one of the most SF high-
z
halos and the average contribution from SF sources along the LOS. Focusing on the spectroscopically confirmed
z
∼ 2 PHz protoclusters, we compare the observed properties of their galaxy members with those in the most SF simulated halos. We find a good agreement in the stellar mass and SFR distributions, and in the galaxy number counts, but the SFR-stellar mass relation of the simulated galaxies tends to be shifted to lower SFRs with respect to the observed galaxies. Based on the estimated final masses of the simulated halos, we infer that between 63% and 72% of the
Planck
-selected protoclusters will evolve into massive galaxy clusters by
z
= 0. Despite contamination from star-forming galaxies along the LOS, we thus confirm the efficiency of
Planck
in selecting star-forming protoclusters at cosmic noon with the simulations, and provide a new criterion for selecting the most massive cluster progenitors at high-
z
, using observables such as the number of galaxy members and their SFR distribution.
We have performed a multi-wavelength analysis of two galaxy cluster systems selected with the thermal Sunyaev-Zel’dovich (tSZ) effect and composed of cluster pairs and an inter-cluster filament. We ...have focused on one pair of particular interest: A399-A401 at redshift
z
~ 0.073 seperated by 3 Mpc. We have also performed the first analysis of one lower-significance newly associated pair: A21-PSZ2 G114.09-34.34 at
z
~ 0.094, separated by 4.2 Mpc. We have characterised the intra-cluster gas using the tSZ signal from
Planck
and, when possible, the galaxy optical and infrared (IR) properties based on two photometric redshift catalogues: 2MPZ and WISExSCOS. From the tSZ data, we measured the gas pressure in the clusters and in the inter-cluster filaments. In the case of A399-A401, the results are in perfect agreement with previous studies and, using the temperature measured from the X-rays, we further estimate the gas density in the filament and find
n
0
= (4.3 ± 0.7) × 10
-4
cm
-3
. The optical and IR colour–colour and colour–magnitude analyses of the galaxies selected in the cluster system, together with their star formation rate, show no segregation between galaxy populations, both in the clusters and in the filament of A399-A401. Galaxies are all passive, early type, and red and dead. The gas and galaxy properties of this system suggest that the whole system formed at the same time and corresponds to a pre-merger, with a cosmic filament gas heated by the collapse. For the other cluster system, the tSZ analysis was performed and the pressure in the clusters and in the inter-cluster filament was constrained. However, the limited or nonexistent optical and IR data prevent us from concluding on the presence of an actual cosmic filament or from proposing a scenario.
Abstract
We present a multifrequency approach which optimizes the constraints on cosmological parameters with respect to extragalactic point source and secondary anisotropy contamination on small ...scales. We model with a minimal number of parameters the expected dominant contaminations in intensity, such as unresolved point sources and the thermal Sunyaev-Zel'dovich effect. The model for unresolved point sources, either Poisson distributed or clustered, uses data from Planck early results. The method presented is the first one where the models of the point-source contributions are based on the Planck early data. To reduce the number of parameters necessary to characterize the residuals, the method uses the knowledge of the frequency dependences of the residual signals coming from the data. The dependences are directly included in the parametrizations, allowing us to reduce the number of the residual parameters to the minimum of three. The overall three amplitudes of the residual contributions are included in a Markov chain Monte Carlo analysis for the estimate of cosmological parameters. We show that our method is robust: as long as the main contaminants are taken into account, the constraints on the cosmological parameters are unbiased regardless of the realistic uncertainties on the contaminants. Although general, the method is applied only to Planck.
Using the PV observation of A1795, we illustrate the capability of XMM-EPIC to measure cluster temperature profiles, a key ingredient for the determination of cluster mass profiles through the ...equation of hydrostatic equilibrium. We develop a methodology for spatially resolved spectroscopy of extended sources, adapted to XMM background and vignetting characteristics. The effect of the particle induced background is discussed. A simple unbiased method is proposed to correct for vignetting effects, in which every photon is weighted according to its energy and location on the detector. We were able to derive the temperature profile of A1795 up to 0.4 times the virial radius. A significant and spatially resolved drop in temperature towards the center ($r< 200 {\rm kpc}$) is observed, which corresponds to the cooling flow region of the cluster. Beyond that region, the temperature is constant with no indication of a fall-off at large radii out to 1.2 Mpc.
In the simple case of a constant equation of state, redshift distribution of collapsed structures may constrain dark energy models. Different dark energy models having the same energy density today ...but different equations of state give quite different number counts. Moreover, we show that introducing the possibility that dark energy collapses with dark matter (“inhomogeneous” dark energy) significantly complicates the picture. We illustrate our results by comparing four dark energy models to the standard Λ-model. We investigate a model with a constant equation of state equal to -0.8, a phantom energy model and two scalar potentials (built out of a combination of two exponential terms). Although their equations of state at present are almost indistinguishable from a Λ-model, both scalar potentials undergo quite different evolutions at higher redshifts and give different number counts. We show that phantom dark energy induces opposite departures from the Λ-model as compared with the other models considered here. Finally, we find that inhomogeneous dark energy enhances departures from the Λ-model with maximum deviations of about 15% for both number counts and integrated number counts. Larger departures from the Λ-model are obtained for massive structures which are rare objects making it difficult to statistically distinguish between models.
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