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I. de Martino

Publications and source records attributed to I. de Martino.

4 recordsLinked to original sources

New Constraints on Spatial Variations of the Fine Structure Constant from Clusters of Galaxies

We have constrained the spatial variation of the fine structure constant using multi-frequency measurements of the thermal Sunyaev-Zeldovich effect of 618 X-ray selected clusters. Although our results are not competitive with the ones from quasar absorption lines, we improved by a factor 10 and ~2.5 previous results from Cosmic Microwave Background power spectrum and from galaxy clusters, respectively.

astro-ph.CO↗

Constraining spatial variations of the fine structure constant using clusters of galaxies and Planck data

We propose an improved methodology to constrain spatial variations of the fine structure constant using clusters of galaxies. We use the {\it Planck} 2013 data to measure the thermal Sunyaev-Zeldovich effect at the location of 618 X-ray selected clusters. We then use a Monte Carlo Markov Chain algorithm to obtain the temperature of the Cosmic Microwave Background at the location of each galaxy cluster. When fitting three different phenomenological parameterizations allowing for monopole and dipole amplitudes in the value of the fine structure constant we improve the results of earlier analysis involving clusters and the CMB power spectrum, and we also found that the best-fit direction of a hypothetical dipole is compatible with the direction of other known anomalies. Although the constraining power of our current datasets do not allow us to test the indications of a fine-structure constant dipole obtained though high-resolution optical/UV spectroscopy, our results do highlight that clusters of galaxies will be a very powerful tool to probe fundamental physics at low redshift.

astro-ph.CO↗

A $f(R)$-gravity model of the Sunyaev-Zeldovich profile of the Coma cluster compatible with {\it Planck} data

In the weak field limit, analytic $f(R)$ models of gravity introduce a Yukawa-like correction to the Newtonian gravitational potential. These models have been widely tested at galactic scales and provide an alternative explanation to the dynamics of galaxies without Dark Matter. We study if the temperature anisotropies due to the thermal Sunyaev-Zeldovich effect are compatible with these Extended Theories of Gravity. We assume that the gas is in hydrostatic equilibrium within the modified Newtonian potential and it is well described by a polytropic equation of state. We particularize the model for the Coma cluster and the predicted anisotropies are compared with those measured in the foreground cleaned maps obtained using the Planck Nominal maps released in 2013. We show that the computed $f(R)$ pressure profile fits the data giving rise to competitive constraints of the Yukawa scale length $L=(2.19\pm1.02) \rm{\, Mpc}$, and of the deviation parameter $ δ=-0.48\pm0.22$. Those are currently the tightest constraints at galaxy cluster scale, and support the idea that Extended Theories of Gravity provide an alternative explanation to the dynamics of self-gravitating systems without requiring Dark Matter.

astro-ph.CO↗

Constraining the redshift evolution of the Cosmic Microwave Background black-body temperature with PLANCK data

We constrain the deviation of adiabatic evolution of the Universe using the data on the Cosmic Microwave Background (CMB) temperature anisotropies measured by the {\it Planck} satellite and a sample of 481 X-ray selected clusters with spectroscopically measured redshifts. To avoid antenna beam effects, we bring all the maps to the same resolution. We use a CMB template to subtract the cosmological signal while preserving the Thermal Sunyaev-Zeldovich (TSZ) anisotropies; next, we remove galactic foreground emissions around each cluster and we mask out all known point sources. If the CMB black-body temperature scales with redshift as $T(z)=T_0(1+z)^{1-α}$, we constrain deviations of adiabatic evolution to be $α=-0.007\pm 0.013$, consistent with the temperature-redshift relation of the standard cosmological model. This result could suffer from a potential bias $δα$ associated with the CMB template, that we quantify it to be $|δα|\le 0.02$ and with the same sign than the measured value of $α$, but is free from those biases associated with using TSZ selected clusters; it represents the best constraint to date of the temperature-redshift relation of the Big-Bang model using only CMB data, confirming previous results.

astro-ph.CO↗