ELT requirements for future observations of the Intergalactic Medium

We summarise the science cases for an ELT that were presented in the parallel session on the intergalactic medium, and the open discussion that followed the formal presentations. Observations of the IGM with an ELT provides tremendous potential for dramatic improvements in current programmes in a very wide variety of subjects. These range from fundamental physics (expansion of the Universe, nature of the dark matter, variation of physical constants), cosmology (geometry of the Universe, large-scale structure), reionisation (ionisation state of the IGM at high redshift>6, to more traditional astronomy, such as the interactions between galaxies and the IGM (metal enrichment, galactic winds and other forms of feedback), and the study of the interstellar medium in high redshift galaxies through molecules. The requirements on ELTs and their instruments for fulfilling this potential are discussed.Comment: proceedings IAU 232 "Extremely Large Telescopes", eds Whitelock, Leibundgut and Dennefeld, comments welcom

The Anti-Corruption Argument for High Public Official Remuneration in Singapore

This chapter investigates the anti-corruption argument for a principle of comparability between public and private sectors determining HPO remuneration in Singapore. The analysis use the argumentative structure of Stephen Toulmin and the associated methodology of Analytic Discourse Evaluation, developed by Teun Dekker, as the primary tool of investigation. Part 1 describes the circumstances surrounding the comparably high wages in the Singaporean public sector. Part 2 reconstructs the anti-corruption argument for comparative remuneration of high public officials (HPOs) in Singapore, showing it to rest on normative Claims about fairness. Part 3 evaluates the reconstruction, focusing on the plausibility of the general Claim that a comparative salary reduces HPO corruption, on the mechanism of the principle of comparability, and on the Claim that a comparable salary is a demand of justice

Numerical simulations of quasar absorbers

The physical state of the intergalactic medium can be probed in great detail with the intervening absorption systems seen in quasar spectra. The properties of the Hydrogen absorbers depend on many cosmological parameters, such as the matter-power spectrum, reionisation history, ionising background and the nature of the dark matter. The spectra also contain metal lines, which can be used to constrain the star formation history and the feedback processes acting in large and small galaxies. Simulations have been instrumental in investigating to what extent these parameters can be unambiguously constrained with current and future data. This paper is meant as an introduction to this subject, and reviews techniques and methods for simulating the intergalactic medium.Comment: 20 pages, to appear in IAU 199 conf proc, "Probing Galaxies through Quasar Absorption Lines," eds. Williams, Shu, Menar

Dissociation through enhanced cooperation or collective withdrawal

NWOVI.Veni.201R.061Institutions, Decisions and Collective Behaviou

The Iκεα model of feedback-regulated galaxy formation

We present the Iκεα model of galaxy formation, in which a galaxy’s star formation rate is set by the balance between energy injected by feedback from massive stars and energy lost by the deepening of the potential of its host dark matter halo due to cosmological accretion. Such a balance is secularly stable provided that the star formation rate increases with the pressure in the star forming gas. The Iκεα model has four parameters that together control the feedback from star formation and the cosmological accretion rate onto a halo. Iκεα reproduces accurately the star formation rate as a function of halo mass and redshift in the EAGLE hydrodynamical simulation, even when all four parameters are held constant. It predicts the emergence of a star forming main sequence along which the specific star formation rate depends weakly on stellar mass with an amplitude that increases rapidly with redshift. We briefly discuss the emerging mass-metallicity relation, the evolution of the galaxy stellar mass function, and an extension of the model that includes feedback from active galactic nuclei (AGN). These self-regulation results are independent of the star formation law and the galaxy’s gas content. Instead, star forming galaxies are shaped by the balance between stellar feedback and cosmological accretion, with accurately accounting for energy losses associated with feedback a crucial ingredient

A halo model for cosmological Lyman-limit systems

We present an analytical model for cosmological Lyman-limit systems (LLSs) that successfully reproduces the observed evolution of the mean free path (L) of ionizing photons. The evolution of the co-moving mean free path is predominantly a consequence of the changing meta galactic photo-ionization rate and the increase with cosmic time of the minimum mass below which halos lose their gas due to photo-heating. In the model, Lyman-limit absorption is caused by highly ionized gas in the outskirt of dark matter halos. We exploit the association with halos to compute statistical properties of LLSs and of their bias, b. The latter increases from 1.5 to 2.6 from redshifts 2 to 6. Combined with the rapid increase with redshift of the bias of the halos that host a quasar, the model predicts a rapid drop in the value of L when measured in quasar spectra from z=5 to 6, whereas the actual value of L falls more smoothly. We derive an expression for the effective optical depth due to Lyman limit absorption as a function of wavelength and show that it depends sensitively on the poorly constrained number density of LLSs as a function of column density. The optical depth drops below unity for all wavelengths below a redshift of 2.5, which is therefore the epoch when the Universe first became transparent to ionizing photons.Comment: 18 page

Democratic backsliding and the poverty of the European Commission’s conception of democracy

The European Commission has had a central role in debates over democratic backsliding in EU member states. But what type of democracy does the Commission uphold? Drawing on an analysis of speeches by European Commissioners, Alvaro Oleart and Tom Theuns write the Commission tends to articulate a technocratic and legalistic conception of democracy. They argue that if the Commission were to adopt a more pluralistic approach, it would be better equipped to tackle democratic backsliding

A halo model for cosmological Lyman-limit systems

We present an analytical model for cosmological Lyman-limit systems (LLS) that successfully reproduces the observed evolution of the mean free path (λeff) of ionizing photons. The evolution of the co-moving mean free path is predominantly a consequence of the changing meta galactic photoionization rate and the increase with cosmic time of the minimum mass below which haloes lose their gas due to photoheating. In the model, Lyman-limit absorption is caused by highly ionized gas in the outskirt of dark matter haloes. We exploit the association with haloes to compute statistical properties of λeff and of the bias, b, of LLS. The latter increases from b ∼ 1.5 → 2.6 from redshifts z = 2 → 6. Combined with the rapid increase with redshift of the bias of the haloes that host a quasar, the model predicts a rapid drop in the value of λeff when measured in quasar spectra from z = 5 → 6, whereas the actual value of λeff falls more smoothly. We derive an expression for the effective optical depth due to Lyman limit absorption as a function of wavelength and show that it depends sensitively on the poorly constrained number density of LLS as a function of column density. The optical depth drops below unity for all wavelengths below a redshift of ∼2.5 which is therefore the epoch when the Universe first became transparent to ionizing photons