Intracluster Entropy from Joint X-ray and Sunyaev-Zel'dovich Observations

The temperature and density of the hot diffuse medium pervading galaxy groups and clusters combine into one significant quantity, the entropy. Here we express the entropy levels and profiles in model-independent forms by joining two observables, the X-ray luminosity and the change in the CMB intensity due to the Sunyaev-Zel'dovich (SZ) effect. Thus we present both global scaling relations for the entropy levels from clusters and groups, and a simple expression yielding the entropy profiles in individual clusters from resolved X-ray surface brightness and SZ spatial distributions. We propose that our approach provides two useful tools for comparing large data samples with models, in order to probe the processes that govern the thermal state of the hot intracluster medium. The feasibility of using such a diagnostic for the entropy is quantitatively assessed, based on current X-ray and upcoming SZ measurements

Probing the evolution of galaxy clusters with the SZ effect

In galaxy clusters the thermal Sunyaev-Zel'dovich (SZ) effect from the hot intracluster medium (ICM) provides a direct, self-contained measure of the pressure integrated over crossing lines of sight, that is intrinsically independent of redshift and well suited for evolutionary studies. We show in detail how the size of the effect and its pattern on the sky plane are directly related to the entropy levels in the ICM, and how they characterize the cluster cores and outskirts independently. We find that at redshifts z 72 0.3 the signals to be expected in the cores considerably exceed those detected at 10' resolution with the Planck satellite. We propose that at 1' resolutions as implemented on recent ground instrumentation for mapping features in individual clusters, the average patterns of the SZ signals can provide a direct and effective way to find and count cool, low-entropy cores and hot, high-entropy outskirts out to z ~ 2. Such counts will tell the timing and the mode of the processes that drive the evolution of the ICM from the distant to the local cluster population

Entropy Flattening, Gas Clumping and Turbulence in Galaxy Clusters

Several physical processes and formation events are expected in cluster outskirts, a vast region up to now essentially not covered by observations. The recent \textsl{Suzaku} (X-ray) and \textsl{Planck} (Sunayev-Zeldovich effect) observations out to the virial radius have highlighted in these peripheral regions a rather sharp decline of the intracluster gas temperature, an entropy flattening in contrast with the theoretically expected power law increase, the break of the hydrostatic equilibrium even in some relaxed clusters, a derived gas mass fraction above the cosmic value measured from several CMB experiments, and a total X-ray mass lower than the weak lensing mass determinations. Here we present the analysis of four clusters (A1795, A2029, A2204 and A133) with the SuperModel that includes a nonthermal pressure component due to turbulence to sustain the hydrostatic equilibrium also in the cluster outskirts. In such way we obtain a correct determination of the total X-ray mass and of the gas mass fraction; this in turn allows to determine the level of the gas clumping that can affect the shape of the entropy profiles reported by the \textsl{Suzaku} observations. Our conclusion is that the role of the gas clumping is very marginal and that the observed entropy flattening is due to the rapid decrement of the temperature in the cluster outskirts caused by non gravitational effects. Moreover, we show that the X-ray/SZ joint analysis from \textsl{ROSAT} and \textsl{Planck} data, as performed in some recent investigations, is inadequate to discriminate between a power law increase and a flattening of the entropy

Empirical Evidence of Nonminimally Coupled Dark Matter in the Dynamics of Local Spiral Galaxies?

We look for empirical evidence of a nonminimal coupling (NMC) between dark matter (DM) and gravity in the dynamics of local spiral galaxies. In particular, we consider a theoretically motivated NMC that may arise dynamically from the collective behavior of the coarse-grained DM field (e.g., via Bose–Einstein condensation) with averaging/coherence length L. In the Newtonian limit, this NMC amounts to modify the Poisson equation by a term L2∇2ρ proportional to the Laplacian of the DM density itself. We show that such a term, when acting as a perturbation over the standard Navarro–Frenk–White profile of cold DM particles, can substantially alter the dynamical properties of galaxies, in terms of their total radial acceleration within the disk and rotation velocity. Specifically, we find that this NMC model can properly fit the stacked rotation curves (RCs) of local spiral galaxies with different velocities at the optical radius, including dwarfs and low-surface-brightness systems, at a level of precision comparable to, and in some instances even better than, the phenomenological Burkert profile. Finally, we show that by extrapolating down to smaller masses the scaling of L versus halo mass found from the above RC analysis, the NMC model can adequately reproduce the radial acceleration relation in shape and normalization down to the dwarf spheroidal galaxy range, a task which constitutes a serious challenge for alternative DM models even inclusive of baryonic effects

Guanine Oxidation in Double-stranded DNA by MnTMPyP/KHSO5: At Least Three Independent Reaction Pathways

In order to better define the mechanism and the products of guanine oxidation within DNA, we investigated the details of the mechanism of guanine oxidation by a metalloporphyrin, Mn-TMPyP, associated to KHSO5 on oligonucleotides. We found that the three major products of guanine oxidation are formed by independent reaction routes. The oxidized guanidinohydantoin (1) and the proposed spiro compound 3 derivatives are not precursors of imidazolone lesion (Iz). These guanine lesions as well as their degradation products, may account for non-detected guanine oxidation products on oxidatively damaged DNA

DMAW 2010 LEGACY the Presentation Review: Dark Matter in Galaxies with its Explanatory Notes

The Seminar "Dark Matter in Galaxies" was delivered, within the Dark Matter Awareness Week (1-8 December 2010) at 140 institutes in 46 countries and it was followed by 4200 people. A documentation of this worldwide initiative is at http://www.youtube.com/watch?v=AOBit8a-1Fw. A reference presentation, prepared by a coordinated pool of leading scientists in the field, was available to speakers. In response to feedbacks and suggestions, we upgraded it to a "Presentation Review" of which we provide here the Explanatory Notes, the link to the .pptx file, and some image of the slides. This Presentation Review is an innovative scientific product to meet the request of information about the phenomenology of the DM mystery at galactic scale. This Review concerns the mass discrepancy phenomenon detected in galaxies, usually accounted by postulating the presence of a non luminous non baryonic component. In the theoretical framework of Newtonian Gravity we recall the properties of Dark Matter halos as emerging from the state-of-the-art of numerical simulations performed in the current $\Lambda CDM$ scenario. Then, the simple but much-telling phenomenology of the distribution of dark and luminous matter in Spirals, Ellipticals, and dwarf Spheroidals is reported. We show that a coherent observational framework emerges from reliable data of different large samples of objects and it is obtained by different methods of investigation. We then highlight the impressive evidence that the distribution of dark and luminous matter are closely correlated and that have universal features. Hints on the cosmological role of this phenomenological scenario are then given. Finally, we discuss the constraints on the elusive nature of the dark particle that the actual distribution of DM around galaxies pose on its direct and indirect searches.Comment: 29 pages, 1 Figure, 1 List. The .pptx file of the Presentation can be downloaded at http://www.sissa.it/ap/dmg/dmaw_presentation.htm

Astrophysical and Cosmological Relevance of the High-Frequency Features in the Stochastic Gravitational-Wave Background

The stochastic gravitational-wave background (SGWB) produced by merging neutron stars features a peak in the kHz frequency band. In this paper, we develop a theoretical framework to exploit such a distinguishing feature through a Markov Chain Monte Carlo analysis using a simulated data-set of SGWB measurements within this frequency band. The aim is to use the peak of the SGWB as an observable to constrain a selection of astrophysical and cosmological parameters that accurately describe the SGWB. We examine how the variation of these parameters impacts the morphology of the SGWB. Given our priors on astrophysical and cosmological parameters, we show that the values of the chirp mass and common envelope efficiency of the binary systems are retrieved with percent accuracy, as well as the cosmological expansion history populated by these binaries, represented by the Hubble constant, the matter abundance and the effective equation of state of the dark energy.Comment: 10 pages, 6 figure

Astroparticle Constraints from the Cosmic Star Formation Rate Density at High Redshift: Current Status and Forecasts for JWST

We exploit the recent determination of cosmic star formation rate (SFR) density at redshifts $z\gtrsim 4$ to derive astroparticle constraints on three common dark matter scenarios alternative to standard cold dark matter (CDM): warm dark matter (WDM), fuzzy dark matter ($\psi$DM) and self-interacting dark matter (SIDM). Our analysis relies on the UV luminosity functions measured by the Hubble Space Telescope out to $z\lesssim 10$ and down to UV magnitudes $M_{\rm UV}\lesssim -17$. We extrapolate these to fainter yet unexplored magnitude ranges, and perform abundance matching with the halo mass functions in a given DM scenario, so obtaining a relationship between the UV magnitude and the halo mass. We then compute the cosmic SFR density by integrating the extrapolated UV luminosity functions down to a faint magnitude limit $M_{\rm UV}^{\rm lim}$, which is determined via the above abundance matching relationship by two free parameters: the minimum threshold halo mass $M_{\rm H}^{\rm GF}$ for galaxy formation, and the astroparticle quantity $X$ characterizing each DM scenario (namely, particle mass for WDM and $\psi$DM, and kinetic temperature at decoupling $T_X$ for SIDM). We perform Bayesian inference on such parameters via a MCMC technique by comparing the cosmic SFR density from our approach to the current observational estimates at $z\gtrsim 4$, constraining the WDM particle mass to $m_X\approx 1.2^{+0.3\,(11.3)}_{-0.4\,(-0.5)}$ keV, the $\psi$DM particle mass to $m_X\approx 3.7^{+1.8\,(+12.9.3)}_{-0.4\,(-0.5)}\times 10^{-22}$ eV, and the SIDM temperature to $T_X\approx 0.21^{+0.04\,(+1.8)}_{-0.06\,(-0.07)}$ keV at $68\%$ ($95\%$) confidence level. We then forecast how such constraints will be strengthened by upcoming refined estimates of the cosmic SFR density, if the early data on the UV luminosity function at $z\gtrsim 10$ from JWST will be confirmed down to ultra-faint magnitudes.Comment: 18 pages, accepted in MDPI Universe. arXiv admin note: text overlap with arXiv:2205.0947

Searching for anisotropic stochastic gravitational-wave backgrounds with constellations of space-based interferometers

Many recent works have shown that the angular resolution of ground-based detectors is too poor to characterize the anisotropies of the stochastic gravitational-wave background (SGWB). For this reason, we asked ourselves if a constellation of space-based instruments could be more suitable. We consider the Laser Interferometer Space Antenna (LISA), a constellation of multiple LISA-like clusters, and the Deci-hertz Interferometer Gravitational-wave Observatory (DECIGO). Specifically, we test whether these detector constellations can probe the anisotropies of the SGWB. For this scope, we considered the SGWB produced by two astrophysical sources: merging compact binaries and a recently proposed scenario for massive black-hole seed formation through multiple mergers of stellar remnants. We find that measuring the angular power spectrum of the SGWB anisotropies is almost unattainable. However, it turns out that it could be possible to probe the SGWB anisotropies through cross-correlation with the CMB fluctuations. In particular, we find that a constellation of two LISA-like detectors and CMB-S4 can marginally constrain the cross-correlation between the CMB lensing convergence and the SGWB produced by the black hole seed formation process. Moreover, we find that DECIGO can probe the cross-correlation between the CMB lensing and the SGWB from merging compact binaries.Comment: 17 pages, 9 figures, accepted by Ap