A population of Optically Quiescent Quasars from WISE and SDSS

The growth of active galactic nuclei (AGNs) occurs under some form of obscuration in a large fraction of the population. The difficulty in constraining this population leads to high uncertainties in cosmic X-ray background and galaxy evolution models. Using an SDSS–WISE cross-match, we target infrared luminous AGN (W1 − W2 > 0.8, and monochromatic rest-frame luminosity above λLλ(12 μm) ≈ 3 × 1044 erg s−1), but with passive galaxy-like optical spectra (Optically Quiescent Quasars; OQQs). We find 47 objects that show no significant [O III]λ5007 emission, a typically strong AGN optical emission line. As a comparison sample, we examine SDSS-selected Type 2 quasars (QSO2s), which show a significant [O III]λ5007 line by definition. We find a 1:16 ratio of OQQs compared to QSO2s, suggesting that the OQQ duty cycle is likely much shorter than that of QSO2s (though selection biases are not fully quantified). We consider observed properties in comparison with other galaxy types, and examine them for consistency with theories on their intrinsic nature: chiefly (a) a high covering factor for surrounding obscuring matter, preventing the detection of high-ionisation emission lines – ‘cocooned AGN’; or (b) ionized gas being absent on the kpc scales of the Narrow Line Region (NLR), perhaps due to a ‘switching on’ or ‘young’ AGN. OQQs do not obviously fit the standard paradigm for merger-driven AGN and host galaxy evolution, implying we may be missing part ofthe flow of AGN evolution

Direct reflectance measurements from drones: sensor absolute radiometric calibration and system tests for forest reflectance characterization

Drone-based remote sensing has evolved rapidly in recent years. Miniaturized hyperspectral imaging sensors are becoming more common as they provide more abundant information of the object compared to traditional cameras. Reflectance is a physically defined object property and therefore often preferred output of the remote sensing data capture to be used in the further processes. Absolute calibration of the sensor provides a possibility for physical modelling of the imaging process and enables efficient procedures for reflectance correction. Our objective is to develop a method for direct reflectance measurements for drone-based remote sensing. It is based on an imaging spectrometer and irradiance spectrometer. This approach is highly attractive for many practical applications as it does not require in situ reflectance panels for converting the sensor radiance to ground reflectance factors. We performed SI-traceable spectral and radiance calibration of a tuneable Fabry-Pérot Interferometer -based (FPI) hyperspectral camera at the National Physical Laboratory NPL (Teddington, UK). The camera represents novel technology by collecting 2D format hyperspectral image cubes using time sequential spectral scanning principle. The radiance accuracy of different channels varied between ±4% when evaluated using independent test data, and linearity of the camera response was on average 0.9994. The spectral response calibration showed side peaks on several channels that were due to the multiple orders of interference of the FPI. The drone-based direct reflectance measurement system showed promising results with imagery collected over Wytham Forest (Oxford, UK)

Obscuration beyond the nucleus: infrared quasars can be buried in extreme compact starbursts

In the standard quasar model, the accretion disk obscuration is due to the canonical dusty torus. Here, we argue that a substantial part of the quasar obscuration can come from the interstellar medium (ISM) when the quasars are embedded in compact starbursts. We use an obscuration-unbiased sample of 578 infrared (IR) quasars at $z\approx 1-3$ and archival ALMA submillimeter host galaxy sizes to investigate the ISM contribution to the quasar obscuration. We calculate SFR and ISM column densities for the IR quasars and a control sample of submillimeter galaxies (SMGs) not hosting quasar activity and show that: (1) the quasar obscured fraction is constant up to $\rm SFR\approx 300 \: M_{\odot} \: yr^{-1}$, and then increases towards higher SFR, suggesting that the ISM obscuration plays a significant role in starburst host galaxies, and (2) at $\rm SFR\gtrsim 300 \: M_{\odot} \: yr^{-1}$, the SMGs and IR quasars have similarly compact submillimeter sizes ($R_{\rm e}\approx 0.5-3\rm \: kpc$) and, consequently, the ISM can heavily obscure the quasar, even reaching Compton-thick ($N_{\rm H}>10^{24} \rm \: cm^{-2}$) levels in extreme cases. Based on our results, we infer that $\approx 10-30\%$ of the IR quasars with $\rm SFR\gtrsim 300 \: M_{\odot} \: yr^{-1}$ are obscured solely by the ISM.Comment: Accepted for publication in MNRAS Letter

Measuring the health-related Sustainable Development Goals in 188 countries : a baseline analysis from the Global Burden of Disease Study 2015

Background In September, 2015, the UN General Assembly established the Sustainable Development Goals (SDGs). The SDGs specify 17 universal goals, 169 targets, and 230 indicators leading up to 2030. We provide an analysis of 33 health-related SDG indicators based on the Global Burden of Diseases, Injuries, and Risk Factors Study 2015 (GBD 2015). Methods We applied statistical methods to systematically compiled data to estimate the performance of 33 health-related SDG indicators for 188 countries from 1990 to 2015. We rescaled each indicator on a scale from 0 (worst observed value between 1990 and 2015) to 100 (best observed). Indices representing all 33 health-related SDG indicators (health-related SDG index), health-related SDG indicators included in the Millennium Development Goals (MDG index), and health-related indicators not included in the MDGs (non-MDG index) were computed as the geometric mean of the rescaled indicators by SDG target. We used spline regressions to examine the relations between the Socio-demographic Index (SDI, a summary measure based on average income per person, educational attainment, and total fertility rate) and each of the health-related SDG indicators and indices. Findings In 2015, the median health-related SDG index was 59.3 (95% uncertainty interval 56.8-61.8) and varied widely by country, ranging from 85.5 (84.2-86.5) in Iceland to 20.4 (15.4-24.9) in Central African Republic. SDI was a good predictor of the health-related SDG index (r(2) = 0.88) and the MDG index (r(2) = 0.2), whereas the non-MDG index had a weaker relation with SDI (r(2) = 0.79). Between 2000 and 2015, the health-related SDG index improved by a median of 7.9 (IQR 5.0-10.4), and gains on the MDG index (a median change of 10.0 [6.7-13.1]) exceeded that of the non-MDG index (a median change of 5.5 [2.1-8.9]). Since 2000, pronounced progress occurred for indicators such as met need with modern contraception, under-5 mortality, and neonatal mortality, as well as the indicator for universal health coverage tracer interventions. Moderate improvements were found for indicators such as HIV and tuberculosis incidence, minimal changes for hepatitis B incidence took place, and childhood overweight considerably worsened. Interpretation GBD provides an independent, comparable avenue for monitoring progress towards the health-related SDGs. Our analysis not only highlights the importance of income, education, and fertility as drivers of health improvement but also emphasises that investments in these areas alone will not be sufficient. Although considerable progress on the health-related MDG indicators has been made, these gains will need to be sustained and, in many cases, accelerated to achieve the ambitious SDG targets. The minimal improvement in or worsening of health-related indicators beyond the MDGs highlight the need for additional resources to effectively address the expanded scope of the health-related SDGs.Peer reviewe

Octopus as predators of Haliotis laevigata on an abalone sea ranch of south-western Australia

Octopuses play key ecological roles within coastal marine environments around the world. Their short-lived, rapid-growing lifecycle commands high feeding rates, which has the potential to impose strong top-down controls on the benthic communities where they are found. This Thesis investigated two major questions on the predatory role of octopuses on an abalone sea ranch in south-western Australia: (i) does the distribution of octopus on the sea ranch affect the mortality of Greenlip Abalone, Haliotis laevigata (Chapter 2), and (ii) what is the diet and nutrient assimilation (δ13C and δ15N) of Octopus cf. tetricus in this ecosystem (Chapter 3). Data were collected by commercial divers over a 27-month period on octopus abundance and the number of empty abalone shells at ~fortnightly to monthly intervals, and the number of abalone surviving on artificial abalone habitats (“Abitats”) every six months. These data were used to examine whether the number of empty shells, and the counts of surviving abalone were related to the presence of octopus. Negative binomial generalised linear models showed that the presence of octopus had a significant impact on the number of empty abalone shells collected and estimated that the shell counts are 78% higher when O. cf. tetricus is present when adjusting for location (“Line”) and Season. The Abitats provide an ideal habitat for octopuses, offering shelter and an abundant food supply. The relationship between octopus and shell counts was also influenced by the spatial position of the Abitats (Line) and Season, which may be linked to environmental variability and the time at which abalone are seeded. The results from time series (AR1) models for the relationship between octopus presence and abalone survival were not significant, contradicting those from the negative binomial models. This result is likely an artefact of the random sampling design for counting abalone to estimate survival and uncertainty in the number of abalone seeded onto each Abitat. A subsample of 110 shells collected by the divers was examined for evidence of octopus predation. Twenty shells (18%) had a small, slightly ovoid hole with a bevelled edge, consistent with the holes made by octopuses. These results confirm that octopuses are a major source of mortality on the sea ranch, supporting the results of the negative binomial models. Gastric tract and stable isotope analyses were undertaken to determine the dietary composition of different sizes of O. cf. tetricus, and its significance as a predator of H. laevigata on the abalone sea ranch. The crops and stomachs of 44 individuals were examined to assess whether diet differed between these digestive organs, or with increasing body size ( 1,000 g were available for analysis. The nitrogen (δ15N) and carbon (δ13C) isotope signatures of octopus, fish, abalone, and benthic primary producers were examined to understand the assimilation of nitrogen and carbon by O. cf. tetricus, and the trophic position of this species within the Flinders Bay sea ranch food web. Examination of δ15N values revealed that O. cf. tetricus (8.08 ± 0.19) occupies a mid-trophic level, slightly below teleosts (10.10 ± 0.22) and loliginid squids (9.47 ± 0.27). The δ13C signature of O. cf. tetricus (-23.63 ± 0.42) was similar to three benthic teleosts, Coris auricularis and Opthalmolepis lineolatus, and Upeneichthys vlamingii, highlighting the overlap in use of benthic food resources by several consumers in this system. While gastric tract analyses suggest that O. cf. tetricus is an important predator of H. laevigata, stable isotope analyses show a less obvious trend. This is indicated by the enrichment of δ13C by ~4‰ between abalone and octopus. The results from this Thesis provide information on the predatory role of O. cf. tetricus, their significance as predators of H. laevigata, and their trophic positioning within this coastal marine system

Life history, ecology, and population dynamics of the Australian Fairy Tern and implications for their conservation

Developing effective wildlife conservation strategies requires an understanding of animal behaviour, their life history strategy, population demographics, resource use, and the processes threatening survival. Despite being classified as Vulnerable to extinction and in urgent need of conservation action, there have been no major studies on the Australian Fairy Tern (hereafter Fairy Tern) Sternula nereis nereis. This thesis investigated various aspects of Fairy Tern behaviour, life history, population movements, and ecology with a view to help inform future conservation actions. First, I used a mark-recapture study and coordinated community-based resighting’s of marked birds to understand the seasonal movements, meta-population structure and site use of Fairy Terns across their breeding range in Western Australia (Chapter 2). Two distinct populations were identified: a widely distributed, partially migratory spring/summer-breeding population; and a smaller, sedentary, winter-breeding population in the Pilbara. Based on the likely spatial extent of exchange among breeding adults and natal recruits, seven management units were proposed. Second, a bird banding study, supported by extensive field observations, photographic recapture of marked birds and sunrise to sunset video observation was used to understand mating systems, colony formation processes, egg-laying and incubation periods, time to fledging and post-hatching care (Chapter 3). The median distance from the nearest neighbour, at a colony in North Fremantle, was 0.71 m, which increased with time. Birds laying earlier in the season selected nest sites with higher beach shell cover compared to those that laid later. The mean incubation period (n = 86) was 21 days, with both pairs contributing, almost equally, to incubation. On average, chicks fledged 22 days after hatching (n = 10), leaving the colony with their parents within 8 days of fledging. Third, I used a novel bird banding method and photographic recapture to describe plumage development and age-related behaviour of juvenile Fairy Terns up to 100 days of age (Chapter 4). This information may be used for the development of a field ageing guide, enabling the collection of standardised information on colony demographics and juvenile development. Fourth, I investigated prey composition among colonies, between years, times of day and feeding stages, i.e. courtship vs chick feeding, using non-invasive digital photography (Chapter 5). Significant differences were identified for each factor, likely driven by differences in environmental conditions and fish species assemblages at each site, diurnal patterns in prey behaviour, Fairy Tern behaviour, and differing prey handling capabilities and nutritional requirements between adult females and chicks. Overall, the diet of Fairy Terns was dominated by three main taxa: Blue Sprat Spratelloides robustus; hardyheads (Atherinidae); and garfishes Hyporhamphus spp., which contributed ≥ 75% of all prey at each site. This feeding study demonstrated that colony site selection is likely associated with habitats that support a large biomass of small, pelagic schooling fishes. However, the strong reliance on Blue Sprat, a short lived (< 1 year) schooling clupeid, highlights a potential vulnerability of Fairy Terns to changes in prey biomass during the breeding season. Finally, I assessed whether simulated conspecific cues, i.e. call playbacks and decoys, increased the likelihood of attracting Fairy Terns to potentially suitable nesting habitats. To understand the influence of playbacks compared to decoys, I measured the behavioural response of terns to the different cues using a full cross-over design (Chapter 6). While settling decisions varied between sites, call playbacks were the primary cues needed to attract terns but may be required over several seasons before colonies are established

The selection, analysis and implications of rare AGN in large surveys

There is a known connection between supermassive black hole growth and galaxy evolution (e.g., Kormendy and Ho, 2013). Grasping the nature of this connection requires understanding of both the growth of black holes via accretion, and how these processes can affect their host galaxies. In order to understand the feedback between them it is necessary to work towards a full census of the highly diverse population of AGN types. This thesis aims to address the work needed to complete this census by assessing the ‘missing’ AGN, applying different selection techniques to fill the gaps, and analysing the AGN found in this way.Lack of a complete census of AGN means that knowledge of vital population statistics such as accretion rates or obscuration depths is incomplete. This thesis takes a first step to solving this problem through all-sky searches in the immediate, local universe via the Local AGN Survey (LASr; Asmus et al., 2020). In Chapter 2 we construct an unbiased sample of local AGN, including both known AGN and candidate AGN. We select these candidates using mid-infrared techniques, to identify AGN that have been missed in photometric surveys at other wavelengths. The aim of this is to work towards a complete sample of local AGN, and thus we must follow up the AGN candidates to confirm them as true AGN or discard them from the census. We construct the most complete all-sky galaxy sample within 100 Mpc (90% completeness for log(M⋆/M⊙)∼9.4), four times deeper than the current reference (the Two Micron All-Sky Survey Redshift Survey; 2MRS), which misses ∼20% of known luminous AGN. Using MIR selection with WISE, we find 221 galaxies with Lnuc (12 μm) &gt;~1042.3 erg s−1. Among these are 61 new AGN candidates. We begin a follow-up campaign with these objects, aiming to use optical and near-infrared spectroscopy to perform AGN diagnostics and assess the results of our AGN candidate selection. Here we present results from the first three targets where we find two probable AGN, and analysis of an object believed to be a Compact Obscured Nucleus.A major difficulty in selecting AGN - and hence an area where known AGN in LASr are scarce - is recognising heavily obscured AGN. Almost every selection technique is significantly biased against these objects and thus they are often missed from surveys, despite possibly representing periods of intense growth in AGN life cycles. The most promising method of selection is with hard X-rays ( &gt; 10 keV). Selected from the 80-month NuSTAR Serendipitous survey (Klindt et al., 2022, submitted), and expanding on previous work on the 40-month catalogue (Lansbury et al., 2017a,b), in Chapter 3 we find sources with an excess of emission in the hard band (8-24 keV) compared to the soft band (3-8 keV), implying thick obscuration. We combine the NuSTAR data with available soft X-ray data (XMM-Newton, Chandra, or Swift-XRT depending on availability and exposure) to study the properties of these rare AGN. From 14 hard X-ray selected candidate Compton thick (CT) AGN we analyse the 9 with net sources &gt; 100, finding 4 CT (log NH &gt; 24 cm−2) and the remainder heavily obscured (log NH &gt;∼23 cm-2), implying a Compton thick fraction for NuSTAR selected AGN within z &lt; 0.07 of 15+10−6 % (combined with previous results from Lansbury et al., 2017a). Of the CT AGN, 29+21−12 % appear to be in actively interacting systems.In Chapter 4, at higher redshift we focus on one specific niche – Optically Quiescent Quasars (OQQs) – which are optically bright, IR-coloured AGN (WISE W1 − W2 &gt; 0.8, and monochromatic luminosity above λLλ(12 μm) ≈ 3×1044 erg s−1) that lack major optical signatures. Initially we examine SDSS J075139.06+402810.9, a prototypical candidate at z=0.587, with an [OIII] λ5007Å limiting flux about two dex below Type 2 quasars at similar IR power. The source is significantly detected over 0.5–16 keV with XMM-Newton and NuSTAR, unambiguously confirming the presence of current accretion activity. Spectral modelling yields an intrinsic luminosity L2−10 keV ≈ 4.4×1043 erg s−1, well within the AGN regime, but underluminous relative to its infrared power. Expanding to the wider population in Chapter 5, we select 64 objects that show no significant [O III] λ5007 emission as our OQQ sample. This would typically be a strong optical emission line in AGN, and thus objects without it would normally be discarded. As a comparison sample, we examine SDSS-selected Type 2 quasars (QSO2s), which show a significant [O III] λ5007 line, but have otherwise similar properties to OQQs. We find a 1:16 ratio of OQQs compared to QSO2s, suggesting that the OQQ duty cycle is likely much shorter than the duty cycle of QSO2s (though selection biases are not fully quantified). These may represent the fully enshrouded or ‘cocooned’ phase of AGN growth, and comprehensive searches of such populations are thus vital to constrain AGN properties at important junctions in their evolution. Well-tested techniques based on searching for isotropically emitted AGN signatures would be ineffective tofind such ‘cocooned’ phases, so this research aims to combine multi-wavelength selection techniques to uncover these hidden black holes. Alternatively, the observed lack of optical signatures may represent a true intrinsic lack of emission lines; for example, from a ‘young’ AGN only recently ‘switched on’. Either of these possibilities make OQQs an interesting and under-studied avenue of AGN evolution.With these three sections, I demonstrate the incomplete nature of our knowledge of the true AGN population. I show how different selection techniques can begin to fill in the gaps - firstly with ideal selection instruments operating over small areas to discover objects that are hard to find but not intrinsically rare, and secondly with more general vast surveys across large areas of the sky, finding rarer objects that may represent under-examined areas of AGN evolution. With NuSTAR I reveal three previously unknown Compton thick AGN and confirm another. Using a combination of MIR selection and optical non-AGN appearance I select a group of AGN and classify them as ‘Optically Quiescent Quasars’. I make a detailed study of their properties, including an in depth analysis of a prototype OQQ. Finally, in Chapter 6 I conclude by placing these chapters into context with each other and with the wider AGN zoo

Setup for studying speckle noise of spectroradiometer diffusers in Earth observation applications

Diffusers in in-orbit spectroradiometers cause speckle under partially coherent solar radiation. A speckle pattern entering a spectroradiometer through a small slit creates systematic spectral deviations in measured spectra. We have developed a setup to characterise the spatial speckle of diffusers and the related spectral features. The decorrelation angles measured at 532 nm for Spectralon, Diffusil, and Heraeus diffusers were 0.021, 0.014, and 0.005 respectively. This information can be used for compensating speckle-related spectral features from the radiometric satellite measurements by averaging over multiple decorrelated spectra.Peer reviewe