Home Cosmology Measuring ISW with next-generation radio surveys. (arXiv:1812.01636v1 )

Measuring ISW with next-generation radio surveys. (arXiv:1812.01636v1 [astro-ph.CO])


Authors: Mario Ballardini, Roy Maartens

The late-time integrated Sachs-Wolfe (ISW) signal in the CMB temperature
anisotropies is an important probe of dark energy when it can be detected by
cross-correlation with large-scale structure surveys. Because of their huge
volume, surveys in the radio are well-suited to ISW detection. We show that
21cm intensity mapping and radio continuum surveys with the SKA in Phase~1
promise a $sim5sigma$ detection, with a similar forecast for the precursor
EMU survey. In SKA2, the 21cm galaxy redshift survey could deliver a
$sim6sigma$ detection, which is probably the maximum achievable level. Our
analysis includes the observational effects on the radio surveys of lensing
magnification, Doppler and other relativistic corrections. These effects alter
the shape of the measured ISW signal, especially at high redshift. The
cross-correlation between lensing magnification and CMB temperature at high
redshift is not a direct probe of dark energy and could bias the ISW
reconstruction. We find that cross-correlation between different redshift bins
compensates the shift due to adding the relativistic corrections in the ISW
detection and improves the quality of the ISW reconstruction.


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