The Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the... Show moreThe Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the case that a breakthrough in angular resolution imaging capabilities is required in order to unravel the processes involved in planet formation. PFI will be optimised to provide a complete census of the protoplanet population at all stellocentric radii and over the age range from 0.1 to 100 Myr. Within this age period, planetary systems undergo dramatic changes and the final architecture of planetary systems is determined. Our goal is to study the planetary birth on the natural spatial scale where the material is assembled, which is the "Hill Sphere" of the forming planet, and to characterise the protoplanetary cores by measuring their masses and physical properties. Our science working group has investigated the observational characteristics of these young protoplanets as well as the migration mechanisms that might alter the system architecture. We simulated the imprints that the planets leave in the disk and study how PFI could revolutionise areas ranging from exoplanet to extragalactic science. In this contribution we outline the key science drivers of PFI and discuss the requirements that will guide the technology choices, the site selection, and potential science/technology tradeoffs. Show less
Santini, P.; Castellano, M.; Fontana, A.; Merlin, E.; Maiolino, R.; Mason, C.; ... ; Valiante, R. 2016
The nature of the Dark Matter is one of the biggest open questions in modern cosmology and particle physics. The work in this thesis concerns a search for the observational effects of one... Show moreThe nature of the Dark Matter is one of the biggest open questions in modern cosmology and particle physics. The work in this thesis concerns a search for the observational effects of one particular class of hypothetical Dark Matter particles, namely those that are allowed to decay. In decaying, X-ray photons are emitted and should be observable. One part of the thesis details the discovery of a potential Dark Matter decay signal in X-ray spectra of galaxies and galaxy clusters, and the subsequent efforts to identify its origin. To this end archival data and new observations are compared to the respective Dark Matter masses of the observed objects. Interpretations of the signal as an instrumental effect, or due to regular astrophysical processes are unsatisfactory. Although the Dark Matter interpretation remains plausible, definitive conclusions about the origin of the signal can not be drawn yet and will require measurements by next generation observatories. The last chapter of the thesis contains the proof-of-concept of a novel technique to search for such weak signals that combines increased statistical power with the ability to determine the physical origin of a signal, while avoiding some of the disadvantages of traditional methods. Show less
In this thesis we present multiple techniques to suppress starlight in order to better directly image planets around other stars. We propose a laboratory setup to test a new focal-plane... Show more In this thesis we present multiple techniques to suppress starlight in order to better directly image planets around other stars. We propose a laboratory setup to test a new focal-plane wavefront sensing technique. We also show an optical device that suppresses starlight using liquid crystals (the vector Apodizing Phase Plate or vAPP). A broadband prototype (500-900 nm) is tested in the optical lab and its properties are determined. We suggest an simple but effective adaptation called the grating-vAPP which is insensitive to one of the common manufacturing errors (retardance offset). Two versions are tested on-sky. One narrow-band prototype at the Large Binocular Telescope that shows that the concept of the grating vAPP works. A second at Magellan/Clay that shows that we can produce a single optic with a broadband behaviour from 2 to 5 microns bandwidth that suppresses both sides of the star simultaneously. The on-sky 5 sigma contrast is 8.3 magnitudes at 2 lambda/D and 12.2 magnitudes at 3.5 lambda/D which makes this coronagraph extremely suited for imaging and characterizing planets close to nearby bright stars. Show less
More men are studying and working in science fields than women. This could be an effect of the prevalence of gender stereotypes (e.g., science is for men, not for women). Aside from the media and... Show moreMore men are studying and working in science fields than women. This could be an effect of the prevalence of gender stereotypes (e.g., science is for men, not for women). Aside from the media and people’s social lives, such stereotypes can also occur in education. Ways in which stereotypes are visible in education include the use of gender-biased visuals, language, teaching methods, and teachers’ attitudes. The goal of this study was to determine whether science education resources for primary school contained gender-biased visuals. Specifically, the total number of men and women depicted, and the profession and activity of each person in the visuals were noted. The analysis showed that there were more men than women depicted with a science profession and that more women than men were depicted as teachers. This study shows that there is a stereotypical representation of men and women in online science education resources, highlighting the changes needed to create a balanced representation of men and women. Even if the stereotypical representation of men and women in science is a true reflection of the gender distribution in science, we should aim for a more balanced representation. Such a balance is an essential first step towards showing children that both men and women can do science, which will contribute to more gender-balanced science and technology fields. Show less
Kazandjian, M.; Pelupessy, F.I.; Meijerink, R.; Israel, F.P.; Spaans, M. 2016
This thesis is centered around the embedded phase of star formation and the chemical links between the various stages of evolution. The primary goal of this work is to pinpoint the origins... Show more This thesis is centered around the embedded phase of star formation and the chemical links between the various stages of evolution. The primary goal of this work is to pinpoint the origins of cometary complex organic molecules in the preceding protoplanetary disk and prestellar stages, both in the gas and solid phases. The grand motivation is to identify our interstellar roots. This work is unique in comparison to earlier publications due to the dynamic nature of the models used in combination with the large comprehensive chemical network. Three chapters in this book pertain to physicochemical models and an additional one is of observational nature. Altogether, this thesis is an attempt to piece together the chemical connection between the prestellar core, the protoplanetary disk and the protoplanetary and cometary materials. The main take-home message is that the seeding of infant Solar System building blocks with complex organic molecules is unavoidable as a result of chemistry during protoplanetary disk assembly. Show less
According to Einstein's theory of general relativity the light of an object is deflected by a mass in its foreground. The deflections can be very weak or so strong that they are visible by eye... Show moreAccording to Einstein's theory of general relativity the light of an object is deflected by a mass in its foreground. The deflections can be very weak or so strong that they are visible by eye yielding strangely distorted arcs or even multiple images of the same source. Measurements of strong or weak lensing let us infer the total mass of the light-deflecting object which is an important cosmological observable. In this thesis we employ gravitational lensing to measure key cosmological observables, such as dark matter and dark energy. Instead of observing the effects of gravitational lensing around single galaxies or galaxy clusters, the Universe itself can be used as a lens: light travelling to us through the cosmic large-scale structure is also weakly lensed by it. Measuring this effect at different cosmic times allows us to infer the evolution of structure in the cosmic web. Hence, we can study how that is affected by dark energy or massive neutrinos. A key result of this thesis is that we find a lower amplitude for the clustering of matter at fixed matter density than that inferred from the most recent measurements of the cosmic microwave background radiation by the Planck satellite. Show less
Inaugural lecture by Prof.dr. Bernhard Rainer Brandl on the acceptance of his position of professor of Infrared Astronomy at the Universiteit Leiden and Astronomy and Instrumentation at the... Show moreInaugural lecture by Prof.dr. Bernhard Rainer Brandl on the acceptance of his position of professor of Infrared Astronomy at the Universiteit Leiden and Astronomy and Instrumentation at the Technische Universiteit Delft on Monday, September 26th, 2016 Show less
This thesis uses novel observations from the Low Frequency Array to address open questions on the topic of galaxy evolution. The highest resolution images at ultra low radio frequencies are used to... Show moreThis thesis uses novel observations from the Low Frequency Array to address open questions on the topic of galaxy evolution. The highest resolution images at ultra low radio frequencies are used to investigate the physical processes present in the radio emission from distant galaxies. Detections of spectral features from carbon atoms in a nearby galaxy are also presented and used to constrain the temperature and density of cold gas that is a key component of all galaxies. Show less
