Luminosity-Diameter Relations for Globular Clusters and Dwarf Spheroidal Galaxies

It is shown that globular clusters and the dwarf spheroidal companions of the Galaxy have a different distribution of flattening values, and appear to occupy adjacent regions of the M_v versus log R_h plane that can be separated by what will be referred to as the Shapley line. Surprisingly, typical dwarf spheroidal companions to the Milky Way System are fainter than the average Galactic globular cluster.Comment: includes two colour figures; MNRAS (Letters) in pres

Purposes almost infinitely varying: archives as sources for labour biography

Sir Hilary Jenkinson, sometime Deputy Keeper of the United Kingdom Public Record Office, wrote in his Manual of Archive Administration about the two common features of archives ‘of extraordinary value and importance’: Impartiality and Authenticity. He referred to the purposes for creating archives and the purposes to which they are put: Drawn up for purposes almost infinitely varying – the administrative or executive control of every species of human undertaking – [archives] are potentially useful … for the information they can give on a range of subjects totally different and equally wide … the only safe prediction concerning the Research ends which Archives may be made to serve is that … these will not be the purposes which were contemplated by the people by whom the Archives were drawn up and preserved.1 That is, archives created for one purpose will invariably end up being used for another purpose entirely. This is challenging for archivists tasked to decide what it is we keep and what we let go: the fact that we need to predict future research use when not even those creating the records know to what uses they will be put

Marketing archives in the digital age: what can a small archives do?

This joint project between the Australian Society of Archivists and the Council of Australasian Archives and Records Authorities took as its target audience ‘the broad Australian public’ and particularly ‘people who might think that archives are of no interest to them’. The idea of the publication was that it would convince this audience that archives were relevant to them

OCCUPATIONAL SAFETY AND HEALTH AS A CASE STUDY: A REACTION

Health Economics and Policy,

Multiperson Utility

We approach the problem of preference aggregation by endowing both individuals and coalitions with partially-ordered or incomplete cardinal preferences. Consistency across preferences for coalitions comes in the form of the Extended Pareto Rule: if two disjoint coalitions A and B prefer x to y, then so does the coalition A*B. The Extended Pareto Rule has important consequences for the social aggregation of individual preferences. Restricting attention to the case of complete individual preferences, and assuming complete preferences for some pairs of agents (interpersonal comparisons of utility units), we discover that the Extended Pareto Rule imposes a "no arbitrage" condition in the terms of utility comparison between agents. Furthermore, if all the individuals and pairs have complete preferences and certain non-degeneracy conditions are met, then we witness the emergence of a complete preference ordering for coalitions of all sizes. The corresponding utilities are a weighted sum of individual utilities, with the n-1 independent weights obtained from the preferences of n-1 pairs forming a spanning tree in the group. Keywords: Preference aggregation, Incomplete preferences, Extended Pareto Rule.

Substructure within the SSA22 protocluster at z≈3.09z\approx3.09

We present the results of a densely sampled spectroscopic survey of the SSA22 protocluster at $z\approx 3.09$. Our sample with Keck/LRIS spectroscopy includes 106 Ly$\alpha$ Emitters (LAEs) and 40 Lyman Break Galaxies (LBGs) at $z=3.05-3.12$. These galaxies are contained within the $9'\times9'$ region in which the protocluster was discovered, which also hosts the maximum galaxy overdensity in the SSA22 region. The redshift histogram of our spectroscopic sample reveals two distinct peaks, at $z=3.069$ (blue, 43 galaxies) and $z=3.095$ (red, 103 galaxies). Furthermore, objects in the blue and red peaks are segregated on the sky, with galaxies in the blue peak concentrating towards the western half of the field. These results suggest that the blue and red redshift peaks represent two distinct structures in physical space. Although the double-peaked redshift histogram is traced in the same manner by LBGs and LAEs, and brighter and fainter galaxies, we find that nine out of 10 X-ray AGNs in SSA22, and all seven spectroscopically-confirmed giant Ly$\alpha$ "blobs," reside in the red peak. We combine our dataset with sparsely sampled spectroscopy from the literature over a significantly wider area, finding preliminary evidence that the double-peaked structure in redshift space extends beyond the region of our dense spectroscopic sampling. In order to fully characterize the three-dimensional structure, dynamics, and evolution of large-scale structure in the SSA22 overdensity, we require the measurement of large samples of LAE and LBG redshifts over a significantly wider area, as well as detailed comparisons with cosmological simulations of massive cluster formation.Comment: 6 pages, 4 figures, Accepted to ApJ Letter

Young and intermediate-age massive star clusters

An overview of our current understanding of the formation and evolution of star clusters is given, with main emphasis on high-mass clusters. Clusters form deeply embedded within dense clouds of molecular gas. Left-over gas is cleared within a few million years and, depending on the efficiency of star formation, the clusters may disperse almost immediately or remain gravitationally bound. Current evidence suggests that a few percent of star formation occurs in clusters that remain bound, although it is not yet clear if this fraction is truly universal. Internal two-body relaxation and external shocks will lead to further, gradual dissolution on timescales of up to a few hundred million years for low-mass open clusters in the Milky Way, while the most massive clusters (> 10^5 Msun) have lifetimes comparable to or exceeding the age of the Universe. The low-mass end of the initial cluster mass function is well approximated by a power-law distribution, dN/dM ~ M^{-2}, but there is mounting evidence that quiescent spiral discs form relatively few clusters with masses M > 2 x 10^5 Msun. In starburst galaxies and old globular cluster systems, this limit appears to be higher, at least several x 10^6 Msun. The difference is likely related to the higher gas densities and pressures in starburst galaxies, which allow denser, more massive giant molecular clouds to form. Low-mass clusters may thus trace star formation quite universally, while the more long-lived, massive clusters appear to form preferentially in the context of violent star formation.Comment: 21 pages, 3 figures. To appear as invited review article in a special issue of the Phil. Trans. Royal Soc. A: Ch. 9 "Star clusters as tracers of galactic star-formation histories" (ed. R. de Grijs). Fully peer reviewed. PDFLaTeX, requires rspublic.cls style fil

Free beer, and what else can we get you?: archives catering for the economic historian

"... the collection started over 50 years ago by Noel Butlin,Professor of Economic History at the Australian National University from 1962 to 1986, to support his and his colleagues’ economic history research is now used more by researchers in other disciplines, and not just history and economics, but Aboriginal studies, anthropology, archaeology, art history, environmental studies, epidemiology, geography, international relations, law, linguistics, musicology, occupational health, political science, psychology and sociology ... A particular problem for archivists is taking a gamble on what might prove useful in the future – you have to sort and catalogue the material, house it in acid-free boxes, shelve it, and promote it, but what if having done all those things and having kept it for 50 years, nobody has ever used it? At what point do you decide not to persevere, though it is almost inevitable that the current fashion will wane and the records will be in demand again at some point? So let me leave you with that last question in particular: Are we collecting the right stuff? Or how can archives cater better for the economic historian?"Economic History Society of Australia and New Zealand

Biases in metallicity measurements from global galaxy spectra: the effects of flux-weighting and diffuse ionized gas contamination

Galaxy metallicity scaling relations provide a powerful tool for understanding galaxy evolution, but obtaining unbiased global galaxy gas-phase oxygen abundances requires proper treatment of the various line-emitting sources within spectroscopic apertures. We present a model framework that treats galaxies as ensembles of HII and diffuse ionized gas (DIG) regions of varying metallicities. These models are based upon empirical relations between line ratios and electron temperature for HII regions, and DIG strong-line ratio relations from SDSS-IV MaNGA IFU data. Flux-weighting effects and DIG contamination can significantly affect properties inferred from global galaxy spectra, biasing metallicity estimates by more than 0.3 dex in some cases. We use observationally-motivated inputs to construct a model matched to typical local star-forming galaxies, and quantify the biases in strong-line ratios, electron temperatures, and direct-method metallicities as inferred from global galaxy spectra relative to the median values of the HII region distributions in each galaxy. We also provide a generalized set of models that can be applied to individual galaxies or galaxy samples in atypical regions of parameter space. We use these models to correct for the effects of flux-weighting and DIG contamination in the local direct-method mass-metallicity and fundamental metallicity relations, and in the mass-metallicity relation based on strong-line metallicities. Future photoionization models of galaxy line emission need to include DIG emission and represent galaxies as ensembles of emitting regions with varying metallicity, instead of as single HII regions with effective properties, in order to obtain unbiased estimates of key underlying physical properties.Comment: 37 pages, 29 figures, 4 tables. Accepted to ApJ. See Figures 15-17 for typical global galaxy biases in strong-line ratios, electron temperatures, and direct-method metallicitie