K-band Imaging of strong CaII-absorber host galaxies at z~1

We present K-band imaging of fields around 30 strong CaII absorption line systems, at 0.7<z<1.1, three of which are confirmed Damped Lyman-alpha systems. A significant excess of galaxies is found within 6"0 (~50kpc) from the absorber line-of-sight. The excess galaxies are preferentially luminous compared to the population of field galaxies. A model in which field galaxies possess a luminosity-dependent cross-section for CaII absorption of the form (L/L*)^0.7 reproduces the observations well. The luminosity-dependent cross-section for the CaII absorbers appears to be significantly stronger than the established (L/L*)^0.4 dependence for MgII absorbers. The associated galaxies lie at large physical distances from the CaII-absorbing gas; we find a mean impact parameter of 24kpc (H0=70km\s\Mpc). Combined with the observed number density of CaII absorbers the large physical separations result in an inferred filling factor of only ~10 per cent. The physical origin of the strong CaII absorption remains unclear, possible explanations vary from very extended disks of the luminous galaxies to associated dwarf galaxy neighbours, remnants of outflows from the luminous galaxies, or tidal debris from cannibalism of smaller galaxies.Comment: 18 pages, 5 figures. Accepted by MNRAS. Version with full resolution figures available at http://www.mpa-garching.mpg.de/~vwild/CaII/CaII_ukirt.pd

A Characterization Theorem for a Modal Description Logic

Modal description logics feature modalities that capture dependence of knowledge on parameters such as time, place, or the information state of agents. E.g., the logic S5-ALC combines the standard description logic ALC with an S5-modality that can be understood as an epistemic operator or as representing (undirected) change. This logic embeds into a corresponding modal first-order logic S5-FOL. We prove a modal characterization theorem for this embedding, in analogy to results by van Benthem and Rosen relating ALC to standard first-order logic: We show that S5-ALC with only local roles is, both over finite and over unrestricted models, precisely the bisimulation invariant fragment of S5-FOL, thus giving an exact description of the expressive power of S5-ALC with only local roles

Peering through the OH Forest: public release of sky-residual subtracted spectra for SDSS DR7

The Sloan Digital Sky Survey (SDSS) automated spectroscopic reduction pipeline provides >1.5 million intermediate resolution, R~2000, moderate signal-to-noise ratio (SNR), SNR~15, astronomical spectra of unprecedented homogeneity that cover the wavelength range 3800-9200AA. However, there remain significant systematic residuals in many spectra due to the sub-optimal subtraction of the strong OH sky emission lines longward of 6700AA. The OH sky lines extend over almost half the wavelength range of the SDSS spectra, and the SNR over substantial wavelength regions in many spectra is reduced by more than a factor two over that expected from photon counting statistics. Following the OH line subtraction procedure presented in Wild & Hewett (2005), we make available to the community sky-residual subtracted spectra for the Sloan Digital Sky Survey Data Relase 7. Here we summarise briefly the method, including minor changes in the implementation of the procedure with respect to WH05. The spectra are suitable for many science applications but we highlight some limitations for certain investigations. Details of the data model for the sky-residual subtracted spectra and instructions on how to access the spectra are provided.Comment: 11 pages, 5 figures. Spectra may be downloaded from the JHU SDSS server http://www.sdss.jhu.edu/skypca/spSpec, additionally the QSOs can be found on the DR7 Value Added Catalogue web page: http://www.sdss.org/dr7/products/value_added/index.html#quasar

Evidence for dust reddening in DLAs identified through CaII H&K absorption

We present a new sample of 31 CaII(H&K) 3935,3970 absorption line systems with 0.84<z_abs<1.3 discovered in the spectra of Sloan Digital Sky Survey (SDSS) Data Release 3 quasars, together with an analysis of their dust content. The presence of Calcium absorption together with measurements of the MgII 2796, FeII 2600 and MgI 2853 lines lead to the conclusion that the majority of our systems are Damped Ly-alpha (DLA) absorbers. The composite spectrum in the rest frame of the absorber shows clear evidence for reddening. Large and Small Magellanic Cloud extinction curves provide satisfactory fits, with a best-fit E(B-V) of 0.06, while the Galactic dust extinction curve provides a poor fit due to the lack of a strong 2175A feature. A trend of increasing dust content with equivalent width of CaII is present. Monte Carlo techniques demonstrate that the detection of reddening is significant at >99.99% confidence. The discovery of significant amounts of dust in a subsample of DLAs has direct implications for studies of the metallicity evolution of the universe and the nature of DLAs in relation to high redshift galaxies. The gas:dust ratio is discussed. Our results suggest that at least ~40% of the CaII absorption systems are excluded from the magnitude-limited SDSS quasar sample as a result of the associated extinction, a fraction similar to the upper limit deduced at higher redshifts from radio-selected surveys.Comment: 5 pages, 2 figures, accepted MNRAS Letter

A report on the sea otter, Enhydra lutris L., in California

This report discusses in detail findings and observations of 5 years of research on the sea otter population and its relationship to the nearshore marine environment in California. Initial efforts were directed at providing some relief to the commercial abalone fishery in the Cambria - Point Estero area north of Morro Bay. This fishery has subsequently collapsed along with other commercial and sport abalone and sport crab fisheries throughout the sea otter's range due to continued sea otter foraging. Capturing, tagging and translocation studies, censusing studies, examination of sea otter remains, habitat surveys, food habits observations and studies on otters in captivity provide a broad base of information on the expanding sea otter population in California and its effects on resources utilized by man. Recommendations for sea otter management consistent with esthetic, recreational, and commercial uses of marine resources are included in this report. (95pp.

The star formation rate of CaII and damped Lyman-alpha absorbers at 0.4<z<1.3

[abridged] Using stacked Sloan Digital Sky Survey spectra, we present the detection of [OII]3727,3730 nebular emission from galaxies hosting CaII and MgII absorption line systems. Both samples of absorbers, 345 CaII systems and 3461 MgII systems, span the redshift interval 0.4 < z < 1.3; all of the former and half the latter sample are expected to be bona-fide damped Lyman-alpha (DLA) absorbers. The measured star formation rate (SFR) per absorber from light falling within the SDSS fibre apertures (corresponding to physical radii of 6-9 h^-1 kpc) is 0.11-0.14 Msol/yr for the MgII-selected DLAs and 0.11-0.48 Msol/yr for the CaII absorbers. These results represent the first estimates of the average SFR in an absorption-selected galaxy population from the direct detection of nebular emission. Adopting the currently favoured model in which DLAs are large, with radii >9h^-1 kpc, and assuming no attenuation by dust, leads to the conclusion that the SFR per unit area of MgII-selected DLAs falls an order of magnitude below the predictions of the Schmidt law, which relates the SFR to the HI column density at z~0. The contribution of both DLA and CaII absorbers to the total observed star formation rate density in the redshift range 0.4 < z < 1.3, is small, <10% and <3% respectively. The result contrasts with the conclusions of Hopkins et al. that DLA absorbers can account for the majority of the total observed SFR density in the same redshift range. Our results effectively rule out a picture in which DLA absorbers are the sites in which a large fraction of the total SFR density at redshifts z < 1 occurs.Comment: Accepted for publication in MNRAS, 13 pages, 6 figure

Collinsville solar thermal project: yield forecasting (final report)

Executive Summary 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Introduction This report’s primary aim is to provide yield projections for the proposed Linear Fresnel Reflector (LFR) technology plant at Collinsville, Queensland, Australia.&nbsp; However, the techniques developed in this report to overcome inadequate datasets at Collinsville to produce the yield projections are of interest to a wider audience because inadequate datasets for renewable energy projects are commonplace.&nbsp; Our subsequent report called ‘Energy economics and dispatch forecasting’ (Bell, Wild &amp; Foster 2014a) uses the yield projections from this report to produce long-term wholesale market price and dispatch forecasts for the plant.&nbsp; 2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Literature review The literature review discusses the four drivers for yield for LFR technology: DNI (Direct Normal Irradiance) Temperature Humidity Pressure Collinsville lacks complete historical datasets of the four drivers to develop yield projections but its three nearby neighbours possess complete datasets, so could act as proxies for Collinsville.&nbsp; However, analysing the four drivers for Collinsville and its three nearby sites shows that there is considerable difference in their climates.&nbsp; This difference makes them unsuitable to act as proxies for yield calculations.&nbsp; Therefore, the review investigates modelling the four drivers for Collinsville. We introduce the term “effective” DNI to help clarify and ameliorate concerns over the dust and dew effects on terrestrial DNI measurement and LFR technology. We also introduce a modified Typical Metrological Year (TMY) technique to overcome technology specific TMYs.&nbsp; We discuss the effect of climate change and the El Niño Southern Oscillation (ENSO) on yield and their implications for a TMY. 2.1&nbsp;&nbsp;&nbsp;&nbsp; Research questions Research questions arising from the literature review include: The overarching research question: Can modelling the weather with limited datasets produce greater yield predictive power than using the historically more complete datasets from nearby sites? This overarching question has a number of smaller supporting research questions: Does BoM adequately adjust its DNI satellite dataset for cloud cover at Collinsville? Given the dust and dew effects, is using raw satellite data sufficient to model yield? Does elevation between Collinsville and nearby sites affect yield? How does the ENSO cycle affect yield? Given the 2007-12 electricity demand data constraint, will the 2007-13 based TMY provide a “Typical” year over the ENSO cycle? How does climate change affect yield? Is the method to use raw satellite DNI data to calculate yield and retrospectively adjusting the calculated yield with an effective to satellite DNI energy per area ratio suitable? How has climate change affected the ENSO cycle? A further research question arises in the methodology but is included here for completeness. What is the expected frequency of oversupply from the Linear Fresnel Novatec Solar Boiler? 3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Methodology In the methodology section, we discuss the data preparation and the model selection process for the four drivers of yield. &nbsp;We also discuss the development of the technology specific TMY and sensitivity analysis to address the research questions on climate change and elevation. 4&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Results and analysis In the results section we present the selection process for the four driver models.&nbsp; We also present the effective to satellite DNI ratio, the annual variation in gross yield, the selection of TMMs for the TMY based on monthly yield, the sensitivity analysis results on climate change and elevation, and the frequency of gross yield exceeding 30 MW. 5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Discussion We analyse the results within a wider context, in particular, we make a comparison with the yield calculations for Rockhampton to address the overarching research question.&nbsp; We find that the modelling of weather at Collinsville using incomplete weather data has higher predictive performance that using the complete weather data at Rockhampton but recommend using the BoM’s one-minute solar data to improve the comparative test.&nbsp; Other findings include the requirement to increase the current TMM’s selection period 2007-13 to incorporate more of the ENSO cycle.&nbsp; There is less than 0.3% change in gross yield from the plant in the most likely case of climate change but there is a requirement to determine the effect of climate change on electricity demand and the ensuing change in wholesale electricity prices. 6&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Conclusion In this report, we have addressed the key research questions, produced the yield projections for our subsequent report ‘Energy economics and dispatch forecasting’ (Bell, Wild &amp; Foster 2014a) and made recommendations for further research

Collinsville solar thermal project: energy economics and dispatch forecasting (final report)

The primary aim of this report is to help negotiate a Power Purchase Agreement (PPA) for the proposed hybrid gas-Linear Frensel Reflector (LFR) plant at Collinsville, Queensland, Australia. &nbsp;The report’s wider appeal is the discussion of the current situation in Australian National Electricity Market (NEM) and techniques and methods used to model the NEM’s demand and wholesale spot prices for the lifetime of the proposed plant. Executive Summary 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Introduction This report primarily aims to provide both dispatch and wholesale spot price forecasts for the proposed hybrid gas-solar thermal plant at Collinsville, Queensland, Australia for its lifetime 2017-47.&nbsp; These forecasts are to facilitate Power Purchase Agreement (PPA) negotiations and to evaluate the proposed dispatch profile in Table 3.&nbsp; The solar thermal component of the plant uses Linear Fresnel Reflector (LFR) technology. &nbsp;The proposed profile maintains a 30 MW dispatch during the weekdays by topping up the yield from the LFR by dispatch from the gas generator and imitates a baseload function currently provided by coal generators.&nbsp; This report is the second of two reports and uses the findings of our first report on yield forecasting (Bell, Wild &amp; Foster 2014b). 2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Literature review The literature review discusses demand and supply forecasts, which we use to forecast wholesale spot prices with the Australian National Electricity Market (ANEM) model. The review introduces the concept of gross demand to supplement the Australian Electricity Market Operator’s (AEMO) “total demand”.&nbsp; This gross demand concept helps to explain the permanent transformation of the demand in the National Electricity Market (NEM) region and the recent demand over forecasting by the AEMO.&nbsp; We also discuss factors causing the permanent transformation.&nbsp; The review also discusses the implications of the irregular ENSO cycle for demand and its role in over forecasting demand. Forecasting supply requires assimilating the information in the Electricity Statement of Opportunities (ESO) (AEMO 2013a, 2014c).&nbsp; AEMO expects a reserve surplus across the NEM beyond 2023-24.&nbsp; Compounding this reserve surplus, there is a continuing decline in manufacturing, which is freeing up supply capacity elsewhere in the NEM.&nbsp; The combined effect of export LNG prices and declining total demand are hampering decisions to transform proposed gas generation investment into actual investment and hampering the role for gas as a bridging technology in the NEM.&nbsp; The review also estimates expected lower and upper bounds for domestic gas prices to determine the sensitivity of the NEM’s wholesale spot prices and plant’s revenue to gas prices. The largest proposed investment in the NEM is from wind generation but the low demand to wind speed correlation induces wholesale spot price volatility.&nbsp; However, McKinsey Global Institute (MGI 2014) and Norris et al. (2014a) expect economically viable energy storage shortly beyond the planning horizon of the ESO in 2023-24.&nbsp; We expect that this viability will not only defer investment in generation and transmission but also accelerate the growth in off-market produced and consumed electricity within the NEM region. 2.1&nbsp;&nbsp;&nbsp;&nbsp; Research questions The report has the following overarching research questions: What is the expected dispatch of the proposed plant’s gas component given the plant’s dispatch profile and expected LFR yield? What are the wholesale spots prices on the NEM given the plant’s dispatch profile? The literature review refines the latter research question into five more specific research questions ready for the methodology: What are the half-hourly wholesale spots prices for the plant’s lifetime without gas as a bridging technology? Assuming a reference gas price of between $5.27/GJ to$7.19/GJ for base-load gas generation (depending upon nodal location;) and for peak-load gas generation of between $6.59/GJ to$8.99/GJ; and given the plant’s dispatch profile What are the half-hourly wholesale spots prices for the plant’s lifetime with gas as a bridging technology? Assuming some replacement of coal with gas generation How sensitive are wholesale spot prices to higher gas prices? Assuming high gas prices are between $7.79/GJ to$9.71/GJ for base-load gas generation (depending upon nodal location); and for peak-load gas generation of between $9.74/GJ to$12.14/GJ; and What is the plant’s revenue for the reference gas prices? How sensitive is the plant’s revenue to gas as a bridging technology? How sensitive is the plant’s revenue to the higher gas prices? What is the levelised cost of energy for the proposed plant? 3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Methodology In the methodology section, we discuss the following items: dispatch forecasting for the proposed plant; supply capacity for the years 2014-47 for the NEM; demand forecasting using a Typical Meteorological Year (TMY); and wholesale spot prices calculation using ANEM, supply capacity and total demand define three scenarios to address the research questions: reference gas prices; gas as a bridging technology; and high gas prices. The TMY demand matches the solar thermal plant’s TMY yield forecast that we developed in our previous report (Bell, Wild &amp; Foster 2014b).&nbsp; Together, these forecasts help address the research questions. 4&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Results In the results section we will present the findings for each research question, including the TMY yield for the LFR and the dispatch of the gas generator given the proposed dispatch profile in Table 3; Average annual wholesale spot prices from 2017 to 2047 for the plant’s node for: Reference gas prices scenario from $18/MWh to$38/MWh Gas as a bridging technology scenario from $18/MWh to$110/MWh High gas price scenario from $20/MWh to$41/MWh The combined plants revenue without subsidy given the proposed profile: Reference gas price scenario $36 million Gas as a bridging technology scenario$52 million High gas price scenario $47 million 5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Discussion In the discussion section, we analyse: reasons for the changes in the average annual spot prices for the three scenarios; and the frequency that the half-hourly spot price exceeds the Short Run Marginal Cost (SRMC) of the gas generator for the three scenarios for: day of the week; month of the year; and time of the day. If the wholesale spot price exceeds the SRMC, dispatch from the gas plant contributes towards profits.&nbsp; Otherwise, the dispatch contributes towards a loss.&nbsp; We find that for both reference and high gas price scenarios the proposed profile in Table 3 captures exceedances for the day of the week and the time of the day but causes the plant to run at a loss for several months of the year.&nbsp; Figure 14 shows that the proposed profile captures the exceedance by hour of the day and Figure 16 shows that only operating the gas component Monday to Friday is well justified.&nbsp; However, Figure 15 shows that operating the gas plant in April, May, September and October is contributing toward a loss.&nbsp; Months either side of these four months have a marginal number of exceedances.&nbsp; In the unlikely case of gas as a bridging scenario, extending the proposed profile to include the weekend and operating from 6 am to midnight would contribute to profits. We offer an alternative strategy to the proposed profile because the proposed profile in the most likely scenarios proves loss making when considering the gas component’s operation throughout the year.&nbsp; The gas-LFR plant imitating the based-load role of a coal generator takes advantage of the strengths of the gas and LFR component, that is, the flexibility of gas to compensate for the LFR’s intermittency, and utilising the LFR’s low SRMC.&nbsp; However, the high SRMC of the gas component in a baseload role loses the flexibility to respond to market conditions and contributes to loss instead of profit and to CO2 production during periods of low demand. The alternative profile retains the advantages of the proposed profile but allows the gas component freedom to exploit market conditions.&nbsp; Figure 17 introduces the perfect day’s yield profile calculated from the maximum hourly yield from the years 2007-13.&nbsp; The gas generator tops up the actual LFR yield to the perfect day’s yield profile to cover LFR intermittency.&nbsp; The residual capacity of the gas generator is free to meet demand when spot market prices exceed SRMC and price spikes during Value-of-Lost-Load (VOLL) events.&nbsp; The flexibility of the gas component may prove more advantageous as the penetration of intermittent renewable energy increases. 6&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Conclusion We find that the proposed plant is a useful addition to the NEM but the proposed profile is unsuitable because the gas component is loss making for four months of the year and producing CO2 during periods of low demand.&nbsp; We recommend further research using the alternative perfect day’s yield profile. 7&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Further Research We discuss further research compiled from recommendation elsewhere in the report. 8&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Appendix A Australian National Electricity Market Model Network This appendix provides diagrams of the generation and load serving entity nodes and the transmission lines that the ANEM model uses.&nbsp; There are 52 nodes and 68 transmission lines, which make the ANEM model realistic.&nbsp; In comparison, many other models of the NEM are highly aggregated. 9&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Appendix B Australian National Electricity Market Model This appendix describes the ANEM model in detail and provides additional information on the assumptions made about the change in the generation fleet in the NEM during the lifetime of the proposed plant

Collinsville solar thermal project: yield forecasting (draft report)

The final report has been published and is available here. Executive Summary 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Introduction This report’s primary aim is to provide yield projections for the proposed Linear Fresnel Reflector (LFR) technology plant at Collinsville, Queensland, Australia.&nbsp; However, the techniques developed in this report to overcome inadequate datasets at Collinsville to produce the yield projections are of interest to a wider audience because inadequate datasets for renewable energy projects are commonplace.&nbsp; The subsequent report called ‘Energy economics and dispatch forecasting’ (Bell, Wild &amp; Foster 2014a) uses the yield projections from this report to produce long-term wholesale market price and dispatch forecasts for the plant.&nbsp; 2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Literature review The literature review discusses the four drivers for yield for LFR technology: DNI (Direct Normal Irradiance) Temperature Humidity Pressure Collinsville lacks complete historical datasets of the four drivers to develop yield projects but its three nearby neighbours do possess complete datasets, so could act as proxies for Collinsville.&nbsp; However, analysing the four drivers for Collinsville and its three nearby sites shows that there is considerable difference in their climates.&nbsp; This difference makes them unsuitable to act as proxies for yield calculations.&nbsp; Therefore, the review investigates modelling the four drivers for Collinsville. We introduce the term “effective” DNI to help clarify and ameliorate concerns over the dust and dew effects on terrestrial DNI measurement and LFR technology. We also introduce a modified TMY technique to overcome technology specific Typical Metrological Year (TMY).&nbsp; We discuss the effect of climate change and the El Nino Southern Oscillation (ENSO) on yield and their implications for a TMY. 2.1&nbsp;&nbsp;&nbsp;&nbsp; Research questions Research question arising from the literature review include: The overarching research question: Can modelling the weather with limited datasets produce greater yield predictive power than using the historically more complete datasets from nearby sites? This overarching question has a number of smaller supporting research questions: Is BoM’s DNI satellite dataset adequately adjusted for cloud cover at Collinsville? Given the dust and dew effects, is using raw satellite data sufficient to model yield? Does elevation between Collinsville and nearby sites affect yield? How does the ENSO affect yield? Given the 2007-2012 constraint, will the TMY process provide a “Typical” year over the ENSO cycle? How does climate change affect yield? A further research question arises in the methodology but is included here for completeness. What is the expected frequency of oversupply from the Linear Fresnel Novatec Solar Boiler? 3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Methodology In the methodology section, we discuss the data preparation and the model selection process for the four drivers of yield. 4&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Results and analysis In the results section we present the four driver models selected and the process that was undertaken to arrive at the models. 5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Discussion We analyse the extent to which the research questions are informed by the results. 6&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Conclusion In this report, we have identified the key research questions and established a methodology to address these questions.&nbsp; The models for the four drivers have been established allowing the calculation of the yield projections for Collinsville

Direct Observational Test Rules Out Small MgII Absorbers

Recent observations suggest the incidence of strong intervening MgII absorption systems along the line-of-sight to gamma ray burst (GRB) afterglows is significantly higher than expected from analogous quasar sightlines. One possible explanation is a geometric effect, arising because MgII absorbers only partially cover the quasar continuum regions, in which case MgII absorbers must be considerably smaller than previous estimates. We investigate the production of abnormal absorption profiles by partial coverage and conclude that the lack of any known anomalous profiles in observed systems, whilst constraining, cannot on its own rule out patchy MgII absorbers. In a separate test, we look for differences in the distribution function of MgII equivalent widths over quasar continuum regions and CIII] emission lines. We show that these anomalies should be observable in any scenario where MgII absorbers are very small, but they are not present in the data. We conclude that models invoking small MgII cloudlets to explain the excess of absorbers seen towards GRBs are ruled out.Comment: Accepted for publication in MNRAS Letters. 5 pages, 2 figure