Oral Programme Abstracts Monday, 18th July 2011 13 Galaxy-wide star formation processes Prof Robert Kennicutt Institute of Astronomy, University of Cambridge [email protected] Abstract Thanks to an infusion of multi-wavelength observations of star-forming galaxies near and far, we are now able to study the systematic patterns and scaling laws governing large-scale star formation in unprecedented detail. These new observations reveal deeper insights into the physical regulation of star formation, as well as new complications and inconsistencies which challenge the simple empirical prescriptions and theoretical descriptions which underlie most models and simulations of star-forming galaxies. This talk will review the current state of this rapidly evolving subject, and identify key issues to be addressed with ALMA and other new facilities. Notes Galaxy Formation, Durham, Monday, 18th July 2011 14 The formation and evolution of the galaxy population Prof Simon White MPA [email protected] Abstract The current and past systematic properties of the galaxy population – abundances and clustering as a function of mass, size, characteristic velocity, morphology, star-formation rate and metallicity, as well as scaling relations between these proper- ties – provide our principal source of information about the processes regulating the formation and evolution of galaxies. Techniques for simulating the global properties of large populations of galaxies, rather than the detailed internal structure of one or a few systems, began to be developed in the late 1990’s and have made dramatic progress in the subsequent decade. It is now possible to follow the formation and evolution of the full galaxy population from Local Group dwarf spheroidals to giant cluster cD’s within a single simulation, and so to investigate how observed abundances, clustering and scaling re- lations constrain the efficiency and parameter dependences of processes such as the sequestration of baryons in galaxies, galaxy merging, the growth of central black holes, and the ejection of mass, energy and heavy elements in galactic winds. The largest simulations to date follow the formation and evolution of hundreds of millions of galaxies within volumes similar to those planned for next generation cosmological surveys. Recent technical advances of importance in this area include the im- plementation of MCMC techniques for the systematic exploration of high-dimensional parameter spaces, the development of a scaling scheme which allows a dark matter simulation carried out in one cosmology to represent structure formation Galaxy in any other cosmology consistent with current CMB and large-scale structure constraints, and the construction of virtual telescopes which allow past light-cones in the simulations to be rendered as images directly comparable to those of deep HST or ground-based surveys. These developments open up the possibility of investigating directly and systematically how Formation, uncertainties in galaxy formation physics will affect the precision of cosmological inferences from future surveys. Notes Durham, Monday, 18th July 2011 15 Clues to galaxy formation from local populations Dr Guinevere Kauffmann MPA [email protected] Abstract I will discuss what the past generation of large spectroscopic galaxy surveys have taught us about relations between the physical properties of galaxies, as well as the relations between the physical properties of galaxies and their environments and dark matter halo masses. I will then focus on the so-called “galaxy bi-modality”, reviewing the physical processes that might be at work in shaping this fundamental relation. I will attempt to elucidate the kinds of observations that may finally clarify why the LCDM Universe produces two such different classes of galaxy. Notes Galaxy Formation, Durham, Monday, 18th July 2011 16 Late galaxy evolution (z < 2) Prof Simon Lilly ETH Zurich [email protected] Abstract I will briefly review some of the main observational results concerning the evolution of the galaxy population, especially at z 2 and later. I will introduce the broad range of phenomena concerned, including flows of gas onto and off of galaxies, but will mostly focus on those underlying simplicities of the galaxy population that have emerged from large surveys. These can be used to derive the analytic form(s) for the dominant evolutionary processes concerned. Notes Galaxy Formation, Durham, Monday, 18th July 2011 17 Star formation at intermediate redshift Dr David Elbaz CEA – Saclay [email protected] Abstract Most present-day stars were formed at intermediate redshifts, i.e. z = 0:5–2.5. This is also the epoch when the cosmic star formation history peaked and started to decline until present-day. The cause of this decline has been a major theme of debate and various physical mechanisms have been invoked to explain it ranging from a drop of the rate of mergers to the quenching of star formation from AGN feedback or simply the exhaustion of the gas content of galaxies. Imaging with HST of the dominant galaxy population at these redshifts revealed the presence of large clumps of star formation suggesting that the gas reservoirs participating to these major events of star formation were subject to strong dynamical instabilities. These instabilities could either result from major mergers of galaxies or be driven by intergalactic infall of material through filaments, the so-called cold flows. The recent finding that star formation obeyed some simple scaling laws at all redshifts relating star formation in galaxies with their stellar mass and gas content, extending the Schmidt-Kennicutt relation to high redshifts, has been invoked to favor the cold flow scenario. However, the determination of the star formation rate of galaxies suffers from strong uncertainties due to dust obscuration. With Herschel, it is now possible to determine with unprecedented accuracy the actual SFR of distant galaxies and make a major step forward in the understanding of the dominant factors playing a role in the building of present-day galaxies. Galaxy We will review some of the recent results obtained in this context and present evidence for an infrared scaling law for star- forming galaxies. Formation, Notes Durham, Monday, 18th July 2011 18 SPH simulations of the formation and evolution of galaxies Dr Joop Schaye Leiden University [email protected] Abstract I will review methods and recent developments in large volume SPH simulations of the formation and evolution of galaxies. I will also present some recent results from the OWLS project. Notes Galaxy Formation, Durham, Monday, 18th July 2011 19 Gas flows in galaxies: mergers versus bars Dr Sara Ellison University of Victoria [email protected] Abstract Bars and galaxy-galaxy mergers represent the two main mechanisms for triggering gas inflows that lead to central star for- mation in galaxies. I will present a comparative study of these two mechanisms which uses the star formation rates and gas-phase metallicities measured in SDSS galaxies to probe the efficiency of gas flows. These results will reveal the relative contributions of bars and merger-induced gas inflows in contributing to the build-up of the stellar bulge. Notes Galaxy Formation, Durham, Monday, 18th July 2011 20 Quantifying the mixing due to bars Dr Patricia Sanchez-Blazquez Universidad Autonoma de Madrid [email protected] Abstract We will present star formation histories and the stellar and gaseous metallicity gradients in the disk of a sample of 50 face-on spiral galaxies with and without bars with the aim of quantifying the redistribution of mass and angular momentum in the galactic disks due to bars by comparying both the gas-phase and star-phase metallicity gradients on the disk of barred and non-barred galaxies. Numerical simulations have shown that strong gravitational torque by non-axisymmetric components induce evolutionary processes such as redistribution of mass and angular momentum in the galactic disks (Sellwood & Bin- ney 2002) and consequent change of chemical abundance profiles. If we hope to understand chemical evolution gradients and their evolution we must understand the secular processes and re-arrangement of material by non-axisymmetric com- ponents and vice-versa. Furthermore, the re-arrangement of stellar disk material influences the interpretation of various critical observed metrics of Galaxy evolution, including the age-metallicity relation in the solar neighborhood and the local G-dwarf metallicity distribution. Perhaps the most obvious of these aforementioned non-axisymmetric components are bars - at least 2/3 of spiral galaxies host a bar, and possibly all disk galaxies have hosted a bar at some point in their evolution. While observationally it has been found that barred galaxies have shallower gas-phase metallicity gradients than non-barred galaxies, a complementary analysis of the stellar abundance profiles has not yet been undertaken. This is unfortunate be- Galaxy cause the study of both gas and stars is important in providing a complete picture, as the two components undergo (and suffer from) very different evolutionary process. Formation, Notes Durham, Monday, 18th July 2011 21 Transforming spirals into S0s Prof Alfonso Aragon-Salamanca University of Nottingham [email protected] Abstract Evidence is mounting indicating that S0s were once spiral galaxies that ceased forming stars and subsequently changed their morphology. Studying the timing, location and physical mechanism(s) involved in this transformation is not only interesting in itself, but it can also provide very useful clues on how galaxies evolve and the possible role of the environment. During the last few years we have been following several lines of research to test whether this transformation is indeed taking place, find out where it happens, and look for the physics driving it. At low redshift we have studied in detail the final products of the transformation - the S0s themselves - while at intermediate redshifts (z∼0.5) we have concentrated on the putative progenitors - spiral galaxies - and the galaxies caught in the act of transforming. In this talk I present some of our more interesting results.