Long-term NIR Variability in the UKIDSS Ultra Deep Survey:a new probe of AGN activity at high redshift

We present the first attempt to select AGN using long-term NIR variability. By analysing the K-band light curves of all the galaxies in the UKIDSS Ultra Deep Survey, the deepest NIR survey over ~1 sq degree, we have isolated 393 variable AGN candidates. A comparison to other selection techniques shows that only half of the variable sources are also selected using either deep Chandra X-ray imaging or IRAC colour selection, suggesting that using NIR variability can locate AGN that are missed by more standard selection techniques. In particular, we find that long-term NIR variability identifies AGN at low luminosities and in host galaxies with low stellar masses, many of which appear relatively X-ray quiet.Comment: 12 pages, 18 figures, accepted for publication in MNRAS, an error in Equation 1 has been fixed in this versio

Infrared lags in the light curves of AGN measured using a deep survey

Information on the structure around active galactic nuclei (AGNs) has long been derived from measuring lags in their varying light output at different wavelengths. In principle, infrared data would reach to larger radii, potentially even probing reprocessed radiation in any surrounding dusty torus. In practice, this has proved challenging because high quality data are required to detect such variability, and the observations must stretch over a long period to probe the likely month-scale lags in variability. In addition, large numbers of sources would need to be observed to start searching for any patterns in such lags. Here, we show that the UKIDSS Ultra Deep Survey, built up from repeated observations over almost a decade, provides an ideal data set for such a study. For 94 sources identified as strongly varying AGNs within its square-degree field, we find that the K-band light curves systematically lag the J-band light curves by an average of around a month. The lags become smaller at higher redshift, consistent with the band shift to optical rest-frame emission. The less luminous AGNs also display shorter lags, as would be expected if their physical size scales with luminosity

The environmental dependence of the structure of outer galactic discs in STAGES spiral galaxies

We present an analysis of V-band radial surface brightness profiles for spiral galaxies from the field and cluster environments using Hubble Space Telescope/Advanced Camera for Surveys imaging and data from the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). We use a large sample of ~330 face-on to intermediately inclined spiral galaxies and assess the effect of the galaxy environment on the azimuthally averaged radial surface brightness mu profiles for each galaxy in the outer stellar disc (24 < mu < 26.5 mag per sq arcsec). For galaxies with a purely exponential outer disc (~50 per cent), we determine the significance of an environmental dependence on the outer disc scalelength h_out. For galaxies with a broken exponential in their outer disc, either down-bending (truncation, ~10 per cent) or up-bending (anti-truncation, ~40 per cent), we measure the strength T (outer-to-inner scalelength ratio, log_10(h_out/h_in) of the mu breaks and determine the significance of an environmental dependence on break strength T. Surprisingly, we find no evidence to suggest any such environmental dependence on either outer disc scalelength h_out or break strength T, implying that the galaxy environment is not affecting the stellar distribution in the outer stellar disc. We also find that for galaxies with small effective radii (r_e < 3 kpc) there is a lack of outer disc truncations in both the field and cluster environments. Our results suggest that the stellar distribution in the outer disc of spiral galaxies is not significantly affected by the galaxy environment.Comment: Accepted to MNRAS. Appendix A available at http://www.nottingham.ac.uk/~ppxdtm/STAGES_profiles_appendix.pd

Going to the exclusive show : exhibition strategies and moviegoing memories of Disneys animated feature films in Ghent (1937-1982)

This is a case study of the exploitation and experience of Disney's animated feature films from the 1930s to the 1980s in Ghent (Belgium). It is a historical study of programming practices and financial strategies which constructed childhood memories on watching Disney. The study is a contribution to a historical understanding of the implications of global distribution of film as cultural products and the counter pull of localism. Using a multi-method approach, the argument is made that the scarce screenings were strategically programmed to uplift the moviegoing experience into something out of the ordinary in everyday life. Programming and revenue data characterize the screenings as exclusive and generating high intakes. Consequently, the remembered screenings did not exhale an easy accessible social status nor an image of pervasiveness of popular childhood film, contradictory to conventional accounts of Disney's ubiquity in popular culture

Attributional style, self-esteem, and celebrity worship

Two studies were carried out to investigate the relationship between attributional style (Study 1), self-esteem (Study 2), and different forms of celebrity worship. Entertainment social celebrity worship (the most normal form considered) was unrelated to attributional style or self-esteem; intense personal celebrity worship was related positively to self-esteem but also to a propensity toward stable and globalattributions; and borderline pathological celebrity worship (the most negative form considered) was related to external, stable, and global attributions. These results were independent of whether participants were located in Europe or North America, and are discussed in terms of whether celebrity worship should be regarded as positive or negative and as a unitary concept

Developing autonomous learning in first year university students using perspectives from positive psychology

Autonomous learning is a commonly occurring learning outcome from university study, and it is argued that students require confidence in their own abilities to achieve this. Using approaches from positive psychology, this study aimed to develop confidence in first‐year university students to facilitate autonomous learning. Psychological character strengths were assessed in 214 students on day one at university. Two weeks later their top three strengths were given to them in study skills modules as part of a psycho‐educational intervention designed to increase their self‐efficacy and self‐esteem. The impact of the intervention was assessed against a control group of 40 students who had not received the intervention. The results suggested that students were more confident after the intervention, and that levels of autonomous learning increased significantly compared to the controls. Character strengths were found to be associated with self‐efficacy, self‐esteem and autonomous learning in ways that were theoretically meaningful

A new automatic method to identify galaxy mergers - I. Description and application to the Space Telescope A901/902 Galaxy Evolution Survey

We present a new automatic method to identify galaxy mergers using the morphological information contained in the residual images of galaxies after the subtraction of a smooth Sérsic model. The removal of the bulk signal from the host galaxy light is done with the aim of detecting the much fainter and elusive minor mergers. The specific morphological parameters that are used in the merger diagnostic suggested here are the residual flux fraction (RFF) and the asymmetry of the residuals [A(Res)]. The new diagnostic has been calibrated and optimized so that the resulting merger sample is very complete. However, the contamination by non-mergers is also high. If the same optimization method is adopted for combinations of other structural parameters such as the Concentration, Asymmetry, clumpineSs (CAS) system, the merger indicator we introduce yields merger samples of equal or higher statistical quality than the samples obtained through the use of other structural parameters. We investigate the ability of the method presented here to select minor mergers by identifying a sample of visually classified mergers that would not have been picked up by the use of the CAS system, when using its usual limits. However, given the low prevalence of mergers among the general population of galaxies and the optimization used here, we find that the merger diagnostic introduced in this work is best used as a negative merger test, that is, it is very effective at selecting non-merging galaxies. In common with all the currently available automatic methods, the sample of merger candidates selected is heavily contaminated by non-mergers, and further steps are needed to produce a clean merger sample. This merger diagnostic has been developed using the Hubble Space Telescope/ACS F606W images of the A901/902 multiple cluster system (z= 0.165) obtained by the Space Telescope A901/902 Galaxy Evolution Survey team. In particular, we have focused on a mass- and magnitude-limited sample (log M/M⊙ > 9.0, RVega, Total≤ 23.5 mag) which includes 905 cluster galaxies and 655 field galaxies of all morphological type

A New Automatic Method to Identify Galaxy Mergers I. Description and Application to the STAGES Survey

We present an automatic method to identify galaxy mergers using the morphological information contained in the residual images of galaxies after the subtraction of a Sersic model. The removal of the bulk signal from the host galaxy light is done with the aim of detecting the fainter minor mergers. The specific morphological parameters that are used in the merger diagnostic suggested here are the Residual Flux Fraction and the asymmetry of the residuals. The new diagnostic has been calibrated and optimized so that the resulting merger sample is very complete. However, the contamination by non-mergers is also high. If the same optimization method is adopted for combinations of other structural parameters such as the CAS system, the merger indicator we introduce yields merger samples of equal or higher statistical quality than the samples obtained through the use of other structural parameters. We explore the ability of the method presented here to select minor mergers by identifying a sample of visually classified mergers that would not have been picked up by the use of the CAS system, when using its usual limits. Given the low prevalence of mergers among the general population of galaxies and the optimization used here, we find that the merger diagnostic introduced in this work is best used as a negative merger test, i.e., it is very effective at selecting non-merging galaxies. As with all the currently available automatic methods, the sample of merger candidates selected is contaminated by non-mergers, and further steps are needed to produce a clean sample. This merger diagnostic has been developed using the HST/ACS F606W images of the A901/02 cluster (z=0.165) obtained by the STAGES team. In particular, we have focused on a mass and magnitude limited sample (log M/M_{O}>9.0, R_{Vega}<23.5mag)) which includes 905 cluster galaxies and 655 field galaxies of all morphological types.Comment: 25 pages, 14 figures, 4 tables. To appear in MNRA

Cosmic evolution of the H2 mass density and the epoch of molecular gas

© 2021. The American Astronomical Society. All rights reserved. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.3847/1538-4357/abec81We present new empirical constraints on the evolution of ρ H2, the cosmological mass density of molecular hydrogen, back to z ≈ 2.5. We employ a statistical approach measuring the average observed 850 μm flux density of near-infrared selected galaxies as a function of redshift. The redshift range considered corresponds to a span where the 850 μm band probes the Rayleigh-Jeans tail of thermal dust emission in the rest frame, and can therefore be used as an estimate of the mass of the interstellar medium. Our sample comprises of ≈150,000 galaxies in the UK InfraRed Telescope Infrared Deep Sky Survey Ultra-Deep Survey field with near-infrared magnitudes K AB ≤ 25 mag and photometric redshifts with corresponding probability distribution functions derived from deep 12-band photometry. With a sample approximately 2 orders of magnitude larger than in previous works we significantly reduce statistical uncertainties on ρ H2 to z ≈ 2.5. Our measurements are in broad agreement with recent direct estimates from blank field molecular gas surveys, finding that the epoch of molecular gas coincides with the peak epoch of star formation with ρ H2, 2×107,MȮ Mpc-3at z ≈ 2. We demonstrate that rho; H2, can be broadly modeled by inverting the star formation rate (SFR) density with a fixed or weakly evolving star formation efficiency. This "constant efficiency"model shows a similar evolution to our statistically derived ρ H2,, indicating that the dominant factor driving the peak star formation history at z ≈ 2 is a larger supply of molecular gas in galaxies rather than a significant evolution of the SFR efficiency within individual galaxies.Peer reviewe

Artificial drainage of peatlands: hydrological and hydrochemical process and wetland restoration

Peatlands have been subject to artificial drainage for centuries. This drainage has been in response to agricultural demand, forestry, horticultural and energy properties of peat and alleviation of flood risk. However, the are several environmental problems associated with drainage of peatlands. This paper describes the nature of these problems and examines the evidence for changes in hydrological and hydrochemical processes associated with these changes. Traditional black-box water balance approaches demonstrate little about wetland dynamics and therefore the science of catchment response to peat drainage is poorly understood. It is crucial that a more process-based approach be adopted within peatland ecosystems. The environmental problems associated with peat drainage have led, in part, to a recent reversal in attitudes to peatlands and we have seen a move towards wetland restoration. However, a detailed understanding of hydrological, hydrochemical and ecological process-interactions will be fundamental if we are to adequately restore degraded peatlands, preserve those that are still intact and understand the impacts of such management actions at the catchment scale