Sunyaev-Zel'dovich Surveys: Analytic treatment of cluster detection

Abstract

Thanks to advances in detector technology and observing techniques, true Sunyaev-Zel'dovich (SZ) surveys will soon become a reality. This opens up a new window into the Universe, in many ways analogous to the X-ray band and inherently well-adapted to reaching high redshifts. I discuss the nature, abundance and redshift distributions of objects detectable in ground-based searches with state-of-the-art technology. An advantage of the SZ approach is that the total SZ flux density depends only on the thermal energy of the intracluster gas and not on its spatial or temperature structure, in contrast to the X-ray luminosity. Because ground-based surveys will be characterized by arcminute angular resolution, they will resolve a large fraction of the cluster population. I quantify the resulting consequences for the cluster selection function; these include less efficient cluster detection compared to idealized point sources and corresponding steeper integrated source counts. This implies, contrary to expectations based on a point source approximation, that deep surveys are better than wide ones in terms of maximizing the number of detected objects. At a given flux density sensitivity and angular resolution, searches at millimeter wavelengths (bolometers) are more efficient than centimeter searches (radio), due to the form of the SZ spectrum. Possible ground-based surveys could discover up to $\sim 100$ clusters per square degree at a wavelength of 2 mm and $\sim 10$/sq. deg. at 1 cm, modeling clusters as a simple self-similar population.