In the past 25 years cosmology has evolved from a speculative brach of theoretical physics to a precision science on the intersection of gravity, particle- and astro physics. Ever increasing access to big-data probing the structure of our Universe through space and time, will further strengthen the field of cosmology as an empirical science. Despite tremendous achievements, one of the unanswered questions remains how structure in the Universe originated. The PI and collaborators have developed novel techniques and proposed new observables that could help answer this question. Furthermore, the Universe is a product of causal physics, and observables are generally correlated, each presenting a piece of a coherent puzzle describing its origin, which motivates a consistent multi-tracer analysis. The aim of this Vidi project is to find evidence for primordial scale dependence, non-Gaussianity and tensors by means of a joint analysis of large cosmological data in the form of the cosmic microwave background (CMB) and redshifted 21cm field. In particular, my research will make progress in three prominent science objectives: to determine the statistical properties of the seeds of structure; to obtain evidence for primordial tensors, determine their source and probe their statistical properties; and to optimally combine multiple observables to find evidence for new physics. These objectives will be pursued using analytical modelling, advanced statistical methods, numerical simulations and data analysis. The PI is a member of the Planck collaboration, and the CORE, Simons Observatory and CMB-S4 working groups, which presents the ideal position to develop this ambitious research program. At the same time, 21cm intensity mapping experiments are currently being built, strongly motivating a detailed study of the capabilities of these experiments. As such, the proposed research will make key contributions towards maximizing the science output of current and future CMB an 21cm surveys.

We propose strengthening the collaboration between astronomers and instrumentation groups in the Netherlands and the state of São Paulo structured around the Long Latin American Millimeter Array (LLAMA) which will start scientific observations in early 2017. Funding is requested for the NOVA-ALMA group in the Netherlands to provide a state-of-the-art submillimeter Band-9 receiver covering the 602-720 GHz atmospheric window, to undertake the integration and verification of the frontend with the first generation LLAMA receivers, presently covering the atmospheric windows for Band-5 and Band-9. In parallel we propose to develop a joint São Paulo Netherlands observing program using the Band-9 receiver on LLAMA to undertake molecular line surveys for studying star formation processes in our Galaxy and in nearby external galaxies. For this part of the program we request funds for travel and joint scientific and technical workshops. Furthermore we propose a joint instrumentation development to assure that LLAMA will remain at the forefront of submillimeter astronomy. For the initial phase we request funding for a study involving a PhD student and a postdoc to develop array receivers based on on-chip integration of mixer, Local Oscillator and cryogenic amplifiers. The approach will be to separate the frequency dependent and independent parts as much as possible.

Following the Memorandum OF Understanding between the CHINA NATIONAL SPACE ADMINISTRATION (CNSA) and the NETHERLANDS SPACE OFFICE (NSO) concerning the cooperation on the Chang’E-4 mission, the Netherlands-China Low frequency Explorer (NCLE) payload is currently being developed by the joint Sino-Dutch teams. NCLE is regarded as a pathfinder mission for a future space-based low-frequency radio interferometer which aims at investigating the evolution and formation of the structures in the Dark Ages and Cosmic Dawn. Here we propose for two PhD positions to prepare for and to execute the science exploitation of the NCLE payload. The PhDs will become part of the NCLE team, collaborating with both scientist and engineers on the Dutch and Chinese side. We propose that in phase I of the project the PhDs take part in the commissioning of the NCLE instrument, while one PhD has the focus on the calibration of the instrument and the other focusses more on the design, implementation and calibration of the data pipeline. In phase II we identify constraining the 21-cm line emission global Dark Ages and Cosmic Dawn signal as the major science case, while the study of the emission from the Sun and the large planets is considered science that can easily be addressed by NCLE during the 4 year PhD tracks. In addition, a number of ancillary science cases are identified, ranging from the production of a low-frequency radio sky map to the study of the Lunar ionosphere. Finally, in collaboration with technical teams at the Chinese and Dutch side, we propose that an important outcome of the 2 PhD tracks will be a future concept for a space-based low-frequency radio facility. The work proposed here supports this unique Sino-Dutch project and helps preparing for the science exploitation of NCLE well in time for the launch in May 2018.

Most matter in our Universe is not in the form of atoms and electrons: the ordinary matter of which we have direct experience; instead, it consists of "dark matter”, whose nature is still unknown. Our current dark matter theory explains well the formation of most galaxies in the Universe except for so-called ultra-diffuse galaxies that show an anomalous behaviour. In analogy to the anomaly in Mercury’s orbit that 100 years ago opened the path to Einstein’s General Relativity, this project will explore whether these galaxies may indicate a crack in our current theory and unveil the nature of dark matter.

There are a number of big questions that ongoing and planned surveys of neutral hydrogen (HI) in galaxies aim to address, including: - How do galaxies form and evolve and what role does neutral atomic hydrogen play in these processes? - What transformation processes in terms of accretion and gas loss occur in galaxy clusters? - How does the neutral hydrogen in galaxies relate to the star formation rate and how does this evolve with cosmic time? - How is mass (in the form of galaxies and clusters) distributed in the local Universe and how does the large scale structure influence the local velocity flow fields? In this proposal we aim to address many different aspects of these questions within the various sub-projects listed below which include both ongoing HI surveys as well as preparation for surveys on the SKA precursor instruments, MeerKAT, APERTIF and the JVLA. South African and Dutch astronomers are closely linked by their collaborations on these surveys. There are already active collaborations in various areas including software development, collaborative data analysis for projects already underway (e.g. CHILES, Coma Cluster), technical planning for data reduction, co-supervised students, etc. Further details are listed by sub-project in the main proposal.