Double funding success for cosmologist studying clumps of Dark Matter

Dr Peder Norberg
Dr Peder Norberg

Dr Peder Norberg of the Institute for Astronomy (IfA) is among the Royal Society's 30 new University Research Fellows (URFs) for 2010. He has also been awarded a European Research Council Starting Grant (ERC StG).

The combined value of the awards is around €1.8million over approximately five years. Both awards are intended to support outstanding early-career researchers and enable them to carry out their pioneering ideas.

Peder's research aims to critically test the successful Cold Dark Matter model, and improve our knowledge of galaxy formation and Dark Energy. The ERC citation noted the IfA's strong record of research in this area.

Peder said: 'The combination of these awards presents a unique opportunity to establish myself as a true leader in my field and build a full research team to critically test the most successful cosmological model to date - the standard Cold Dark Matter model – and to provide key insights into the formation of galaxies over time. This frontier research utilizes the most recent galaxy surveys, including the Galaxy And Mass Assembly survey, of which I am Co-Project Leader, and the proprietary Pan-STARRS PS1 survey.'

Peder’s ERC Starting Grant is one of five awarded to the University this year and there are now three ERC grant holders at the IfA, making it unusually successful among astronomy institutes in this respect.

Below, Peder explains the background to his work.

ERC Starting Grants

ERC Starting Grants are prestigious awards which allow researchers in any subject (save nuclear research) who finished their PhD 2-12 years ago to undertake cutting-edge research at any European research institution. Awards last for up to 5 years and provide significant funding – up to EUR 1.5 million – to support the investigator and team. While the scheme is competitive, more cash is being invested in it each year by the European Commission.

Anyone in the School who would like to apply for ERC funding should first contact David Dougal at ERI: David.Dougal [at] Tel: 0131 650 9025


A universe filled with undetected cold dark matter and mysterious dark energy

Dr Peder Norberg

Galaxies are not distributed uniformly: they tend to clump together in groups and clusters. Our grasp of this distribution was revolutionised by the "Sloan Digital Sky Survey" (SDSS) and the "2dF Galaxy Redshift Survey", which mapped out the distances of millions of bright galaxies by measuring their redshift.

This key information on how galaxies are distributed in space contributed directly towards a standard model that describes the observed Universe, composed of three parts: ~5% ordinary matter; ~20% Cold Dark Matter (CDM), a theoretically motivated materia, yet to be directly detected; ~75% Dark Energy, a hypothetical form of energy filling the entire Universe. Hence we are faced with a real enigma as 95% of the content of the Universe is unknown to mankind. This drives my quest to further test the validity of the successful CDM model and to better understand what Dark Energy is.

Gama: a multi-wavelength and spectroscopic survey to test a key model prediction

The properties of CDM are accurately predicted via computer models. Dark Matter tends to cluster, forming large clumps (halos) connected by filaments, creating a so-called cosmic web. This is very similar to the observed distribution of galaxies. In this structure formation model, CDM becomes hence the natural skeleton on which galaxies form and evolve. The main problem is the lack of a distinct proof of its existence, including its non-detection in underground experiments.

I am a co-leader of the "Galaxy And Mass Assembly" (GAMA) redshift survey. GAMA will measure 400,000 new galaxy redshifts and provide a complete account of all galaxy positions in the nearby Universe. It is designed to provide a constraint to a key CDM model prediction, as given by the number of Dark Matter halos per unit volume as function of their mass. Our estimate will rely on counting the number of galaxy groups in GAMA and measuring their masses. Such analyses require the use of many state-of-the-art mock Universes, created from large CDM simulations populated with galaxies following either some galaxy formation recipe or some statistical framework calibrated on real GAMA data.

Pan-STARRS: a unique imaging survey to probe the properties of Dark Energy

Dark Energy, unlike CDM, is theoretically poorly understood and observationally its properties are barely constrained. This led to the construction of several gigantic galaxy surveys, including Pan-STARRS, with main cosmological aim to determine whether Dark Energy changes with time. To help answer that crucial question, my goal is to study the galaxy distribution in Pan-STARRS and quantify its degree of clumpiness at times when the Universe was just half its current age.

Unlike GAMA, Pan-STARRS is an imaging survey with approximate estimates of galaxy distances. Those photometric distances rely on observations at different wavelengths and extra input, like the composition of galaxies and stellar evolution. Their uncertainty and the planned survey sizes are such that new dedicated clustering techniques have to be developed to best extract the underlying signal. Within Pan-STARRS, I lead the group that considers these new statistics, with which we aim to characterise the relation between the observed galaxy light and the underlying mass over time. This work is a vital step towards measuring the evolution of Dark Energy.