Research

ON_Poster_Me4_Equation_LinesThe question of how the galaxies and the large-scale structure formed is extremely complex. The answers involve a great many details related to star formation, dark matter, supernova feedback, active galactic nuclei, gas accretion, and cosmology that are still unknown. We study how galaxies formed and evolved as a function of time and place in the cosmic web. We use multi-wavelength observations from the X-rays to the radio from the world’s main ground- and space based observatories (for example, VLT, Hubble Space Telescope, Chandra, Spitzer, etc.). We also use detailed theoretical predictions and cosmological simulations in order to better understand the observational results and in order to create better models. We are performing small, targeted research programs, as well as participating in a number of large international collaborations in order to find the answers to the many intriguing questions.

Motivation for doing Extra-galactic Astrophysics in Brazil

Originally from Holland, I have spent many years being trained and working in some of the best astrophysics departments around the world (Leiden Observatory in Holland, Johns Hopkins University and the University of Texas in the United States, and the Max-Planck Institute for Astrophysics in Germany). I joined the Observatório Nacional in Rio de Janeiro in 2013 in order to contribute to the development of extra-galactic astrophysics and astronomy in general in Brazil. Today is a very exciting time for young people to be interested in astronomy in Brazil, with some amazing opportunities to do fore-front research with the world’s best telescopes (Gemini, Subary, SDSS, CFHT, ALMA, VLT, etc.). Especially in the field of extragalactic research, we are benefiting from the many exciting international projects and telescopes that were unavailable to Brazilian researchers until only relatively recently. Also, the extra-galactic community in Brazil is still relatively small compared to other areas of astronomy, so we can play a big role in building up extragalactic astrophysics research!

Research areas

The formation of galaxy clusters – Galaxy clusters are the largest gravitationally-bound objects in the universe. We study how to find them at high redshifts, and how to study the cluster formation process by comparing clusters and the progenitors of clusters (“proto- clusters”) at high and low redshift.

The formation and evolution of galaxies – At high redshift, the Hubble Space Telescope has found small galaxies that are the building blocks of the present-day population of spiral and elliptical galaxies. How did this process happen? By using detailed observations of both high redshift and nearby galaxies, we are trying to piece together the complicated puzzle. This teaches us new details about star-formation and supernova winds, merging and gas kinematics, black hole formation, and metal enrichment.

Active galaxies and black holes – Active galactic nuclei (AGN) are extremely energetic phenomena occurring in the cores of some galaxies. They are the result of the inflow of matter onto a supermassive black hole. We are especially interested in the role of AGN in the formation of galaxies and their black holes, and the relation with large-scale structure. We study a variety of AGN, such as quasars, radio galaxies and low-luminosity AGN in starburst galaxies.

Properties of the first galaxies – Telescopes can now quite easily select galaxies at redshifts z~>6, corresponding to only ~0.5-1.0 Gyr after the Big Bang. We are trying to measure the properties of these galaxies, in order to get an idea of what this first population looked like and what it may have evolved into at later times. They also offer an important probe of the epoch of cosmic reionization.

Virtual theoretical observatory and cosmological simulations – We make frequent use of a so-called theoretical virtual observatory, developed by us. The virtual observatory creates simulated telescope images based on cosmological dark matter N-body simulations and semi-analytic models of galaxy formation. The use of such virtual observations is a very new concept in astrophysics, and there are a great many projects associated with this new tool.

The Sloan Digital Sky Survey – We are a member of the large international SDSS-IV survey project, doing projects such as a large integral field survey of 10,000 nearby galaxies (MaNGA) and a high redshift spectroscopic survey that will target 1 million distant galaxies and quasars (eBOSS). Various projects related to galaxy and large-scale structure evolution are in progress.

The J-PAS Survey – J-PAS is a project of Spain and Brazil that will image 8000 deg^2 in 56 optical filters to measure dark energy, galaxy evolution, stars, and solar system bodies. We will study the evolution of the galaxy population out to z~1. The survey will start around 2015. Our group aims to prepare the J-PAS galaxy studies that will be eventually possible.

The Subaru Prime Focus Spectrograph Survey – We are partner of a very large collaboration to build a new multi-object spectrograph for the Subaru Telescope. The goal is to measure dark energy, galaxy evolution and AGN at z>1 and z<8. The collaboration is led by IPMU in Tokyo, and the other partners are Princeton, Caltech, Johns Hopkins, Marseille, Taiwan, and LNA/USP in Brazil. I am the only scientist in Rio de Janeiro in the project. With PFS, our group aims to study galaxies, galaxy clusters, and AGN at high redshifts to a level of detail provided by no other survey around 2018.

Other projects – The universe is a very big place and extragalactic astrophysics is a very broad area of research that is always changing!

 

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