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Chemical tagging of stellar debris from disrupted open clusters and associations underpins the science cases for next-generation multi-object spectroscopic surveys. As part of the Galactic Archaeology project TraCD (Tracking Cluster Debris), a preliminary attempt at reconstructing the birth clouds of now phase-mixed thin disk debris is undertaken using a parametric minimum spanning tree (MST) approach. Empirically-motivated chemical abundance pattern uncertainties (for a 10-dimensional chemistry-space) are applied to NBODY6-realised stellar associations dissolved into a background sea of field stars, all evolving in a Milky Way potential. We demonstrate that significant population reconstruction degeneracies appear when the abundance uncertainties approach 0.1 dex and the parameterised MST approach is employed; more sophisticated methodologies will be required to ameliorate these degeneracies., To appear in "Multi-Object Spectroscopy in the Next Decade: Big Questions, Large Surveys and Wide Fields"; Held: Santa Cruz de La Palma, Canary Islands, Spain, 2-6 Mar 2015; ed. I Skillen & S. Trager; ASP Conference Series (Figures now optimised for B&W printing)

We use the same physical model to simulate four galaxies that match the relation between stellar and total mass, over a mass range that includes the vast majority of disc galaxies. The resultant galaxies, part of the Making Galaxies in a Cosmological Context (MaGICC) program, also match observed relations between luminosity, rotation velocity, size, colour, star formation rate, HI mass, baryonic mass, and metallicity. Radiation from massive stars and supernova energy regulate star formation and drive outflows, balancing the complex interplay between cooling gas, star formation, large scale outflows, and recycling of gas in a manner which correctly scales with the mass of the galaxy. Outflows also play a key role in simulating galaxies with exponential surface brightness profiles, flat rotation curves and dark matter cores. Our study implies that large scale outflows are the primary driver of the dependence of disc galaxy properties on mass. We show that the amount of outflows invoked in our model is required to meet the constraints provided by observations of OVI absorption lines in the circum-galactic-media of local galaxies.

A model which allows the simultaneous monitoring of the chemical, photometric, and thermal evolution of the gaseous and stellar components of spheroidal star systems has been developed. Supernovae-driven superwinds are initiated once the magnitude of the interstellar medium (ISM) thermal energy exceeds that of its binding energy, causing the cessation of star formation and the ejection of the remaining, enriched ISM to the intergalactic medium. Wind models of this nature successfully reproduce many of the correlations amongst observable properties of ellipticals (e.g. colour and magnitude; mass and metallicity), and are generally accepted as the mechanism responsible for the observed galaxy cluster intracluster medium (1CM) heavy element abundances. A detailed accounting of the model sensitivity to the important input ingredients is provided (e.g. initial mass function (IMF); nucleosynthesis; adopted evolutionary scenario for the supernovae (SNe) remnant interior thermal energy). Previous models seem to have underestimated the energy per SNe, made available to the ISM for powering a galactic wind, by assuming that all remnants evolve and expand in isolation, ad infinitum. In reality, shells overlap with adjacent expanding remnants, radically altering each individual remnant’s dynamical evolution, as well as the ISM’s global thermal evolution, resulting in earlier “blow-out” epochs than previously encountered. We have also examined the role played by thermalised kinetic energy from massive star pre-SN mass-loss and find it is an important component for low mass dwarf galaxies, but can be readily neglected for giant ellipticals. The origin of the a-element-to-Iron ratio and the Iron mass-to-luminosity ratio (IMLR) in cluster ICMs is also investigated. The stellar initial mass function in cluster galaxies is shown to be a crucial parameter in determining the mass and abundance ratios of heavy elements, and in particular, we can exclude simple bimodal IMF/star formation models for ellipticals. Models incorporating IMFs mildly flatter than the Salpeter IMF are preferred, provided the intracluster medium IMLR and [α/Fe]>0 X-ray observational constraint, present-day elliptical galaxy colour-luminosity-metallicity relationships, and their stellar population’s Magnesium overabundance relative to Iron, are to be honoured. These models pollute the intracluster medium by means of early winds (i.e. before Iron enrichment from Type Ia SNe exceeds greatly that from Type II, thereby driving the [α/Fe] ratio to negative values), and retain the gas restored by stars afterwards. Conversely, models with Salpeter-like initial mass functions can reproduce the Iron mass-to-luminosity ratio only if they eject all of the stellar gas restored after the early winds (e.g. via ram pressure stripping), with the detrimental effect of yielding a negative [α/Fe] in disagreement with the observations. We demonstrate that the total mass of gas ejected by cluster ellipticals is insufficient to explain the bulk of the ICM X-ray emitting gas, lending support to the notion that the majority of it is of primordial origin. Our work is the first of its kind to couple self-consistently the photometric, chemical, and thermal evolution of the ISM and stellar populations, as well as the resultant effects upon the 1CM abundances and abundance ratios, all within the framework of the supernovae-driven galactic wind model for elliptical galaxies.

A 2.7-meter Liquid Mirror Telescope (LMT) is currently under construction at the University of British Columbia. The stationary, parabolic primary mirror is formed by uniformly rotating the highly reflective liquid, metallic mercury. Compensation for the lack of mechanical tracking will be accomplished by using the Time Delay and Integrate (TDI) readout technique with our Ford 2048 x 2048 CCD detector. The ability to produce large, diffraction-limited mirrors in the laboratory has been previously demonstrated; this project, the first of its kind, is an investigation into their potential for astronomical survey-work, in a working observatory environment. A set of 40 intermediate-band filters, one filter to be used per "photometric" night, will facilitate the collection of Spectral Energy Distributions (SEDs) of all objects, to a limiting stellar V[symbol omitted] ~21, in the 83.0 deg² strip (1/3 deg wide) available to this telescope. A catalog of >10⁵ galaxy and ~3,000 quasar SEDs is expected, providing the largest database of its type to date. A detailed stress-tensor analysis of the mercury-loaded mirror cell is given. The maximum flexure of the cell (at the mirror rim) was found to be ≲0.32 mm. The high resonant frequency of the cell was designed to minimise the excitement of both gravity and capillary waves, surface phenomena which can degrade image quality. An analysis of the support structure indicated that its maximum deflection under wind loading (≲0.3µm) would be significantly less than the Ford CCD's physical pixel size of 15 µm. Temperature-sensitive autofocussing was needed to ensure that thermal expansion/ contraction of the support structure did not lead to defocussing. Star-trail curvature at non-zero latitudes and the discrete nature of the TDI readout mode leads to elongation of north-south (NS) and east-west (EW) image structure, respectively. Convolving stellar Point Spread Functions (e.g. Gaussian) with the CCD's pixel width showed image broadening of ~5% (EW) and ~9% (NS). While these effects are expected to be negligible for our instrument, quantifying them under on-site testing will be imperative before proceeding with the development of larger LMTs.