Constraining primordial non-Gaussianity with the X-ray eROSITA cluster survey

Annalisa Pillepich
UC Santa Cruz


According to the standard scenario, the large-scale structure of the Universe that we recognize today under the form of groups and clusters of galaxies, filaments, and sheets is the result of gravitational instability of small density fluctuations generated at very early times. The statistical properties of these seeds are still unclear. The simplest inflationary models produce Gaussian fluctuations but other plausible scenarios give rise to mildly non-Gaussian density perturbations. For the first time, the upcoming generation of cosmic microwave background studies and galaxy and galaxy-cluster surveys should be able to detect signatures of primordial non-Gaussianity.

In this talk, I will show how primordial non-Gaussianity affects the statistical properties of the matter distribution at low redshift, thus I will discuss how the abundance and clustering of galaxy groups and clusters from current and future surveys can be used to detect primordial non-Gaussianity. In particular, I analyze the potential of the german/russian X-ray telescope eROSITA, planned to be launched in September 2013, to simultaneously constrain cosmological and X-ray scaling-relation parameters via measurement of the number counts and angular powerspectra of an all-sky photon-count limited sample of galaxy-clusters up to z~1.5.