Dr Jacopo Chevallard

Abstract:

Far-ultraviolet (FUV; ~1200-2000 angstroms) spectra are fundamental to our understanding of star-forming galaxies, providing a unique window on massive stellar populations, chemical evolution, feedback processes, and reionization. The launch of JWST will soon usher in a new era, pushing the UV spectroscopic frontier to higher redshifts than ever before, however, its success hinges on a comprehensive understanding of the massive star populations and gas conditions that power the observed UV spectral features. This requires a level of detail that is only possible with a combination of ample wavelength coverage, signal-to-noise, spectral-resolution, and sample diversity that has not yet been achieved by any FUV spectral database. We present the COS Legacy Spectroscopic SurveY (CLASSY) treasury and its first high level science product, the CLASSY atlas. CLASSY builds on the HST archive to construct the first high-quality (S/N_1500 >~ 5/resel), high-resolution (R~15,000) FUV spectral database of 45 nearby (0.002 < z < 0.182) star-forming galaxies. The CLASSY atlas, available to the public via the CLASSY website, is the result of optimally extracting and coadding 170 archival+new spectra from 312 orbits of HST observations. The CLASSY sample covers a broad range of properties including stellar mass (6.2 < logM_star(M_sol) < 10.1), star formation rate (-2.0 < log SFR (M_sol/yr) < +1.6), direct gas-phase metallicity (7.0 < 12+log(O/H) < 8.8), ionization (0.5 < O_32 < 38.0), reddening (0.02 < E(B-V < 0.67), and nebular density (10 < n_e (cm^-3) < 1120). CLASSY is biased to UV-bright star-forming galaxies, resulting in a sample that is consistent with z~0 mass-metallicity relationship, but is offset to higher SFRs by roughly 2 dex, similar to z >~2 galaxies. This unique set of properties makes the CLASSY atlas the benchmark training set for star-forming galaxies across cosmic time.Comment: Accepted for publication in Ap

Abstract:

How does a public policy reform become seemingly inevitable? How and why does bureaucratic “common sense” override empirical evidence? What are the overlaps between accountability and corruption? These open-ended questions drive my study of a neglected object of analysis: the well-intentioned people and institutions working within Australia’s Indigenous affairs local government policy arena. In July 2008 the Northern Territory’s local government sector underwent the most sweeping reform of its history, when 53 councils (governing predominantly rural and majority-Indigenous communities) were forcibly amalgamated into eight regional shires. According to the official narrative, the sector had reached a point of crisis: many councils were administratively too small to manage their growing responsibilities. Despite trenchant popular opposition, amalgamations were justified as technically effective, financially efficient -- even morally imperative. Based on a decade of ethnographic research in the Northern Territory including extensive interviews and professional involvement over many years, my thesis moves beyond an empirical evaluation of these events to explore how government actors establish, maintain and self-assess a policy reform. Despite bureaucracy’s claims on rationality and evidence, I argue that factors such morality, routines and aesthetics play more important roles in policy formation than acknowledged. Influenced by the Deleuzian concepts of assemblage and the minor event, I analyse this reform through mundane bureaucratic habits, obscured settler colonial social relations, and near-forgotten events: the rendering of Indigenous totemic art into a corporate logo; a sport and recreation funding agreement as a site of bureaucratic violence; the mobilisation of a created statistic. This perspective invites an alternative to orthodox policy evaluation, whereby the policy cycle is understood ecologically, as a complex assemblage of force, violence and effect. In July 2008 the Northern Territory’s local government sector underwent the most sweeping reform of its history, when 53 councils (governing predominantly rural and majority-Indigenous communities) were forcibly amalgamated into eight regional shires. According to the official narrative, the sector had reached a point of crisis: many councils were administratively too small to manage their growing responsibilities. Despite trenchant popular opposition, amalgamations were justified as technically effective, financially efficient -- even morally imperative. Based on a decade of ethnographic research in the Northern Territory including extensive interviews and professional involvement over many years, my thesis moves beyond an empirical evaluation of these events to explore how government actors establish, maintain and self-assess a policy reform. Despite bureaucracy’s claims on rationality and evidence, I argue that factors such morality, routines and aesthetics play more important roles in policy formation than acknowledged. Influenced by the Deleuzian concepts of assemblage and the minor event, I analyse this reform through mundane bureaucratic habits, obscured settler colonial social relations, and near-forgotten events: the rendering of Indigenous totemic art into a corporate logo; a sport and recreation funding agreement as a site of bureaucratic violence; the mobilisation of a created statistic. This perspective invites an alternative to orthodox policy evaluation, whereby the policy cycle is understood ecologically, as a complex assemblage of force, violence and effect

Abstract:

We present an analysis of the optical properties of three Ultra Luminous X-ray (ULX) sources identified in NGC 925. We use Integral field unit data from the George Mitchel spectrograph in the context of the Metal-THINGS survey. The optical properties for ULX-1 and ULX-3 are presented, while the spaxel associated with ULX-2 had a low S/N, which prevented its analysis. We also report the kinematics and dimensions of the optical nebula associated with each ULX using ancillary data from the PUMA Fabry-Perot spectrograph. A BPT analysis demonstrates that most spaxels in NGC 925 are dominated by star-forming regions, including those associated with ULX-1 and ULX-3. Using the resolved gas-phase metallicities, a negative metallicity gradient is found, consistent with previous results for spiral galaxies, while the ionization parameter tends to increase radially throughout the galaxy. Interestingly, ULX-1 shows a very low gas metallicity for its galactocentric distance, identified by two independent methods, while exhibiting a typical ionization. We find that such low gas metallicity is best explained in the context of the high-mass X-ray binary population, where the low-metallicity environment favours active Roche lobe overflows that can drive much higher accretion rates. An alternative scenario invoking accretion of a low-mass galaxy is not supported by the data in this region. Finally, ULX-3 shows both a high metallicity and ionization parameter, which is consistent with the progenitor being a highly-accreting neutron star within an evolved stellar population region.Comment: Accepted by Ap