Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

First Sardinia Radio Telescope detection of the Sunyaev-Zel'dovich effect at 18.6 GHz

S. Cocchi, F. Loi, M. Murgia, P. Marchegiani, V. Vacca, F. Govoni, F. Gandossi, G. Rodighiero

Abstract

Galaxy clusters imprint a distinctive signature on the cosmic microwave background through the thermal Sunyaev-Zel'dovich (SZ) effect, which enables to study the intracluster plasma distribution and makes them powerful cosmological probes. We present the first Sardinia Radio Telescope (SRT) detection of the SZ effect in the galaxy cluster MACS J1752+4440 at 18.6 GHz, with a resolution of 0.9'. We detected a decrement in brightness toward the cluster centre, which we attributed to the thermal SZ effect. We modelled the signal using a spherically symmetric $β$ model for the electron density distribution and we employed a Bayesian retrieval to estimate the core radius, central electron density, and $β$ parameter of the cluster. We found values consistent with expectations for a galaxy cluster of the mass of MACS J1752+4440: a core radius of ($160 \pm 30$) kpc, a central electron density of ($2.5^{+0.7}_{-0.5} \cdot 10^{-3}$) cm$^{-3}$, and $β$=$0.6\pm0.1$. The mean Compton-$y$ parameter within a radius of 3.5' is $(2.6 \pm 0.3) \cdot 10^{-5}$, higher than the value reported by Planck, which is coherent considering the different resolution of the instruments and the modelling adopted. This work demonstrates the potential of the SRT to detect the onset of the SZ decrement at low frequencies, providing higher angular resolution than current all-sky surveys and enabling an improved reconstruction of the SZ decrement profile and the plasma distribution in the intracluster medium.

First Sardinia Radio Telescope detection of the Sunyaev-Zel'dovich effect at 18.6 GHz

Abstract

Galaxy clusters imprint a distinctive signature on the cosmic microwave background through the thermal Sunyaev-Zel'dovich (SZ) effect, which enables to study the intracluster plasma distribution and makes them powerful cosmological probes. We present the first Sardinia Radio Telescope (SRT) detection of the SZ effect in the galaxy cluster MACS J1752+4440 at 18.6 GHz, with a resolution of 0.9'. We detected a decrement in brightness toward the cluster centre, which we attributed to the thermal SZ effect. We modelled the signal using a spherically symmetric model for the electron density distribution and we employed a Bayesian retrieval to estimate the core radius, central electron density, and parameter of the cluster. We found values consistent with expectations for a galaxy cluster of the mass of MACS J1752+4440: a core radius of () kpc, a central electron density of () cm, and =. The mean Compton- parameter within a radius of 3.5' is , higher than the value reported by Planck, which is coherent considering the different resolution of the instruments and the modelling adopted. This work demonstrates the potential of the SRT to detect the onset of the SZ decrement at low frequencies, providing higher angular resolution than current all-sky surveys and enabling an improved reconstruction of the SZ decrement profile and the plasma distribution in the intracluster medium.
Paper Structure (6 sections, 4 equations, 3 figures, 1 table)

This paper contains 6 sections, 4 equations, 3 figures, 1 table.

Table of Contents

  1. Introduction
  2. Observations and data reduction
  3. Total intensity results and decrement detection
  4. Decrement modelling
  5. Discussion and conclusions
  6. Parameter retrieval: Corner plot

Figures (3)

  • Figure 1: SRT total intensity image at 18.6 GHz with beam of 0.9, pixel size of 15. Contours at 2, 3, 5, 10, and 20 $\sigma_{NVSS}$ from the NVSS image condon1998 at 1.4 GHz, with $\sigma_{NVSS}$=0.4 mJy/beam.
  • Figure 2: Left: Map of the observed surface brightness decrement in the cluster centre from SRT data at 18.6 GHz. The profile reported on the right was obtained by blanking the radio sources and tracing annuli around the centre of the cluster, at intervals of a half-beam radius from one another. The blue arrow marks a localised surface-brightness excess in the south-eastern region. Right: Observed average surface brightness on annuli around the centre of the cluster, in blue. The continuous line shows the fit of the SZ decrement referred to the models from Eqs. \ref{['eq decrement']} and \ref{['electrondensity']}.
  • Figure 3: Retrieval of parameters for the density profile using $emcee$. The continuous line represents the median of the distribution. The dashed lines show the 16th and 84th percentiles.