Bayesian Soft Target Zones.

Several authors have postulated econometric models for exchange rates restricted to lie within known target zones. However, it is not uncommon to observe exchange rate data with known limits that are not fully 'credible'; that is, where some of the observations fall outside the stated range. An empirical model for exchange rates in a soft target zone where there is a controlled probability of the observed rates exceeding the stated limits is developed in this paper. A Bayesian approach is used to analyse the model, which is then demonstrated on Deutschemark-French franc and ECU-French franc exchange rate data.Bayesian estimation, griddy-Gibbs sampler, credible target zones, soft margins, European Monetary System

Developing resilience as a policy strategy: the impact of policy as mediated by Ofsted

In this thesis I argue that education policy, as mediated by the schools’ regulator, aims to achieve the policy strategy of developing resilient school leaders and teachers from a neoliberal perspective; and perpetuates the racism that, for recent critics, is so entrenched in educational, political and legal systems (DeCuir and Dixson, 2004; Taylor, 2016; McCoy and Rodricks, 2015). My argument is founded on an analysis of the discourse contained within Ofsted’s annual reports using van Dijk’s (2016) Sociocognitive approach to critical discourse studies and a lens provided by Critical Race Theory, drawing on work from leading authors in this field. By analysing the annual reports covering the period 2013 to 2018, I consider how the discourse generated by two Ofsted administrations has potentially influenced the development and maintenance of resilience in school leaders, teachers and learners. In particular, I examine how this contributes to the development of meaningful identity, ‘a powerful source of resilience’ (Beauregard et al, 2017, p. 114), as a crucial part of the ‘a never-ending marathon’ of transformational change (Teach First, 2018, p. 13). My analysis offers three findings. First, it reveals a tension between Ofsted’s mediation of policy, and the government’s stated objective of reforming education to allow every child to ‘shap[e] their own destiny, and becom[e] masters of their own fate’ (DfE, 2010, p. 6). Second, it supports the notion that membership of the in-group is dependent on the property of whiteness and compliance, rather than resilience. Finally, echoing recent critical studies in this field, it highlights the way the regulator has failed to hear the voice of subordinated peoples and is guilty of acts underpinned by interest convergence and differential racialisation

Does Social Media Influence Consumer Buying Behavior? An Investigation Of Recommendations And Purchases

This research investigates consumers who made a purchase of an item based on the recommendation of a peer or contact via social media (e.g., Facebook; Twitter). Using a sample of 249 consumer purchases, this research analyzes the type of product purchased, the cost of the item, and numerous other product dimensions related to the purchase. Results of the study, along with direction for future research, are presented

Bulge Globular Clusters in Spiral Galaxies

There is now strong evidence that the metal-rich globular clusters (GC) near the center of our Galaxy are associated with the Galactic bulge rather than the disk as previously thought. Here we extend the concept of bulge GCs to the GC systems of nearby spiral galaxies. In particular, the kinematic and metallicity properties of the GC systems favor a bulge rather than a disk origin. The number of metal-rich GCs normalized by the bulge luminosity is roughly constant (i.e. bulge S_N ~ 1) in nearby spirals, and this value is similar to that for field ellipticals when only the red (metal--rich) GCs are considered. We argue that the metallicity distributions of GCs in spiral and elliptical galaxies are remarkably similar, and that they obey the same correlation of mean GC metallicity with host galaxy mass. We further suggest that the metal-rich GCs in spirals are the direct analogs of the red GCs seen in ellipticals. The formation of a bulge/spheroidal stellar system is accompanied by the formation of metal-rich GCs. The similarities between GC systems in spiral and elliptical galaxies appear to be greater than the differences.Comment: 5 pages, Latex, 2 figures, 1 table, Accepted for publication in ApJ Letter

Hubble Space Telescope Imaging of the Globular Cluster System around NGC 5846

Bimodal globular cluster metallicity distributions have now been seen in a handful of large ellipticals. Here we report the discovery of a bimodal distribution in the dominant group elliptical NGC 5846, using the Hubble Space Telescope's Wide Field and Planetary Camera 2 (WFPC2). The two peaks are located at V-I = 0.96 and 1.17, which roughly correspond to metallicities of [Fe/H] = -1.2 and -0.2 respectively. The luminosity functions of the blue and red subpopulations appear to be the same, indicating that luminosity does not correlate with metallicity within an individual galaxy's globular cluster system. Our WFPC2 data cover three pointings allowing us to examine the spatial distribution of globular clusters out to 30 kpc (or 2.5 galaxy effective radii). We find a power law surface density with a very flat slope, and a tendency for globular clusters to align close to the galaxy minor axis. An extrapolation of the surface density profile, out to 50 kpc, gives a specific frequency S_N = 4.3 +/- 1.1. Thus NGC 5846 has a much lower specific frequency than other dominant ellipticals in clusters but is similar to those in groups. The central galaxy regions reveal some filamentary dust features, presumably from a past merger or accretion of a gas-rich galaxy. This dust reaches to the very nucleus and so provides an obvious source of fuel for the radio core. We have searched for proto-globular clusters that may have resulted from the merger/accretion and find none. Finally, we briefly discuss the implications of our results for globular cluster formation mechanisms.Comment: 22 pages, Latex. To be published in the Astronomical Journal. Full paper available at http://www.ucolick.org/~forbes/home.htm

Damp Mergers: Recent Gaseous Mergers without Significant Globular Cluster Formation?

Here we test the idea that new globular clusters (GCs) are formed in the same gaseous ("wet") mergers or interactions that give rise to the young stellar populations seen in the central regions of many early-type galaxies. We compare mean GC colors with the age of the central galaxy starburst. The red GC subpopulation reveals remarkably constant mean colors independent of galaxy age. A scenario in which the red GC subpopulation is a combination of old and new GCs (formed in the same event as the central galaxy starburst) can not be ruled out; although this would require an age-metallicity relation for the newly formed GCs that is steeper than the Galactic relation. However, the data are also well described by a scenario in which most red GCs are old, and few, if any, are formed in recent gaseous mergers. This is consistent with the old ages inferred from some spectroscopic studies of GCs in external systems. The event that induced the central galaxy starburst may have therefore involved insufficient gas mass for significant GC formation. We term such gas-poor events "damp" mergers.Comment: 17 pages, 5 figures, ApJ accepte

Cold gas and star formation in a merging galaxy sequence

We explore the evolution of the cold gas and star-formation activity during galaxy interactions, using a merging galaxy sequence comprising both pre- and post-mergers. Data for this study come from the literature but supplemented by new radio observations presented here. Firstly, we confirm that the star-formation efficiency (SFE) increases close to nuclear coalescence. At post-merger stages there is evidence that the SFE declines to values typical of ellipticals. This trend can be attributed to M(H_2) depletion due to interaction induced star-formation. However, there is significant scatter, likely to arise from differences in the interaction details of individual systems. Secondly, we find that the central molecular hydrogen surface density, increases close to the final stages of the merging of the two nuclei. Such a trend is also predicted by numerical simulations. Furthermore, there is evidence for a decreasing fraction of cold gas mass from early interacting systems to merger remnants, attributed to gas conversion into other forms. The evolution of the total-radio to blue-band luminosity ratio, reflecting the disk+nucleus star-formation activity, is also investigated. Although this ratio is on average higher than that of isolated spirals, we find a marginal increase along the merging sequence, attributed to the relative insensitivity of disk star-formation to interactions. However, a similar result is also obtained for the nuclear radio emission, although galaxy interactions are believed to significantly affect the activity in the central galaxy regions. Finally, we find that the FIR--radio flux ratio distribution of interacting galaxies is consistent with star-formation being the main energising source.Comment: 18 pages, 17 figures, accepted for publication in MNRA

Radio Observations of Super Star Clusters in Dwarf Starburst Galaxies

We present new radio continuum observations of two dwarf starburst galaxies, NGC3125 and NGC5408, with observations at 4.80GHz (6cm) and 8.64GHz (3cm), taken with the Australia Telescope Compact Array (ATCA). Both galaxies show a complex radio morphology with several emission regions, mostly coincident with massive young star clusters. The radio spectral indices of these regions are negative (with alpha ~ -0.5 - -0.7), indicating that the radio emission is dominated by synchrotron emission associated with supernova activity from the starburst. One emission region in NGC5408 has a flatter index (alpha ~ -0.1) indicative of optically thin free-free emission, which could indicate it is a younger cluster. Consequently, in these galaxies we do not see regions with the characteristic positive spectral index indicative of optically obscured star-formation regions, as seen in other dwarf starbursts such as Hen 2-10.Comment: Accepted for publication in MNRA

Keck Imaging of the Globular Cluster Systems in the Early--type Galaxies NGC 1052 and NGC 7332

The presence of two globular cluster subpopulations in early-type galaxies is now the norm rather than the exception. Here we present two more examples for which the host galaxy appears to have undergone a recent merger. Using multi-colour Keck imaging of NGC 1052 and NGC 7332 we find evidence for a bimodal globular cluster colour distribution in both galaxies, with roughly equal numbers of blue and red globular clusters. The blue ones have similar colours to those in the Milky Way halo and are thus probably very old and metal-poor. If the red GC subpopulations are at least solar metallicity, then stellar population models indicate young ages. We discuss the origin of globular clusters within the framework of formation models. We conclude that recent merger events in these two galaxies have had little effect on their overall GC systems. We also derive globular cluster density profiles, global specific frequencies and in the case of NGC 1052, radial colour gradients and azimuthal distribution. In general these globular cluster properties are normal for early-type galaxies.Comment: 11 pages, Latex, 15 figures, 2 tables, accepted by MNRA

The optical and near-infrared properties of nearby groups of galaxies

We present a study of the optical (BRI) and near-infrared (JHK) luminosity fuctions (LFs) of the GEMS sample of 60 nearby groups of galaxies between 0<z<0.04, with our optical CCD photometry and near-IR photometry from the 2MASS survey. The LFs in all filters show a depletion of galaxies of intermediate luminosity, two magnitudes fainter than L*, within 0.3 R{500} from the centres of X-ray faint groups. This feature is not as pronounced in X-ray bright gropus, and vanishes when LFs are found out to R{500}, even in the X-ray dim groups. We argue that this feature arises due to the enhanced merging of intermediate-mass galaxies in the dynamically sluggish environment of low velocity-dispersion groups, indicating that merging is important in galaxy evolution even at z~0.Comment: to appear in the proceedings of the ESO workshop "Groups of Galaxies in the Nearby Universe", Santiago, Dec 5-9, 2005. Eds. I. Saviane, V. Ivanov, & J. Borissova (Springer Verlag); 5 page