Multiple sampling and interpolation in the classical Fock space

We study multiple sampling, interpolation and uniqueness for the classical Fock space in the case of unbounded mul-tiplicities

Discovery of a Proto-cluster Associated with a Ly-α\alpha Blob Pair at z=2.3

Bright Ly-$\alpha$ blobs (LABs) --- extended nebulae with sizes of $\sim$100kpc and Ly-$\alpha$ luminosities of $\sim$10$^{44}$erg s$^{-1}$ --- often reside in overdensities of compact Ly-$\alpha$ emitters (LAEs) that may be galaxy protoclusters. The number density, variance, and internal kinematics of LABs suggest that they themselves trace group-like halos. Here we test this hierarchical picture, presenting deep, wide-field Ly-$\alpha$ narrowband imaging of a 1$^\circ$ $\times$ 0.5$^\circ$ region around a LAB pair at $z$ = 2.3 discovered previously by a blind survey. We find 183 Ly-$\alpha$ emitters, including the original LAB pair and three new LABs with Ly-$\alpha$ luminosities of (0.9--1.3)$\times$10$^{43}$erg s$^{-1}$ and isophotal areas of 16--24 arcsec$^2$. Using the LAEs as tracers and a new kernel density estimation method, we discover a large-scale overdensity (Bo{\"o}tes J1430+3522) with a surface density contrast of $\delta_{\Sigma}$ = 2.7, a volume density contrast of $\delta$ $\sim$ 10.4, and a projected diameter of $\approx$ 20 comoving Mpc. Comparing with cosmological simulations, we conclude that this LAE overdensity will evolve into a present-day Coma-like cluster with $\log{(M/M_\odot)}$ $\sim$ $15.1\pm0.2$. In this and three other wide-field LAE surveys re-analyzed here, the extents and peak amplitudes of the largest LAE overdensities are similar, not increasing with survey size, implying that they were indeed the largest structures then and do evolve into rich clusters today. Intriguingly, LABs favor the outskirts of the densest LAE concentrations, i.e., intermediate LAE overdensities of $\delta_\Sigma = 1 - 2$. We speculate that these LABs mark infalling proto-groups being accreted by the more massive protocluster

Star Formation in the COSMOS Field : A radio view on the build-up of stellar mass over 12 billion years

In this thesis I study the evolution of galaxies with a special focus on their star forming ability by using the extensive multi-wavelength data sets available for the 2 square degree COSMOS deep field. The deep radio continuum data from Very Large Array observations at a frequency of 1.4 GHz (a wavelength of 20 cm) form the basis of my analysis of the cosmic star formation history unaffected by dust obscuration. A newly developed stacking algorithm enabled an unprecedentedly representative view on the evolution of the average star formation rate within galaxies down to low limiting (stellar) masses since a redshift of z~3 (i.e. ~2 billion years after the Big Bang). My findings are in good agreement with results from different star formation diagnostics that often suffer from large dust corrections or significantly worse statistics. A main result of this thesis is the identification of a constant characteristic mass for star forming galaxies. It implies that galaxies with masses similar to our Milky Way have always been the main sites of star formation. Therefore the often debated 'downsizing scenario' where the characteristic mass decreases with cosmic time is ruled out. In the young universe (<1.5 billion years of cosmic age) I successfully searched for the most extreme star forming environments. These provide critical constraints on cosmic structure formation and dust enshrouded star formation at early times. A detailed case study not only reveals large amounts of molecular gas but also a powerful hidden active galactic nucleus in one such massive starburst. This finding demonstrates the diversity of this cosmologically important galaxy population