High redshift QSOs and cool dwarfs in the Deep Lens Survey

The Deep Lens Survey, a 20 deg2 optical survey, was used to search for two types of rare, very red objects: faint high-redshift (z \u3e 5.4) quasars, which trace structure formation in the early Universe and can be used to study reionization; and ultracool dwarf stars and brown dwarfs, the most numerous constituents of our own Galaxy, which are seldom detected beyond the solar neighborhood due to their low luminosities. To distinguish between these two populations, we added near-infrared imaging to a portion of the Deep Lens Survey area, covering 1.12 deg2 with survey J-band (1.2 μm) imaging, and successfully targeting 181 out of a planned 280 very red targets over an additional 2.4 deg2. These observations were reduced and cataloged, producing colors or color limits for 1626 very red objects in the field. The colors were corrected using a combination of outside photometric standards and internal checks, and a model for the colors of the target populations was created from existing measurements in the literature. The relative classification probabilities were estimated for each object by using a color model, and those probabilities were used to generate Monte Carlo realizations of the populations, either for comparison to a simulated Galaxy (for ultracool dwarfs) or for the calculation of a luminosity function (for high-redshift QSOs). For QSOs, the results were consistent with the most recent work on faint QSOs: we measured a bright-end power-law slope of for the luminosity function. Citing the similarity to earlier results for brighter QSOs, we rule out QSOs as the dominant source of ionizing photons at the time of reionization (although they may have contributed at the 10-20% level). For ultracool dwarfs, the model that best reproduced our measured magnitudes was a sech2 vertical disk profile with for the earliest spectral type range (M9-L2), with hints of a lower scale height for later spectral types. We integrate a range of best-fit models to predict the number of ultracool dwarfs to be found in future surveys, and estimate the errors introduced into current surveys by over-simplified models of the Galaxy. Spectroscopic observations were obtained for a few of our very red objects; these are displayed and analyzed. Although none of the targeted objects was definitively identified as a QSO, they showed interesting and unusual spectral features nonetheless. The methods demonstrated here for probabilistic classification of galactic and extragalactic objects will be essential to exploit the full potential of future wide deep surveys, such as LSST. These surveys will reach such faint objects that spectroscopy will be difficult or impossible for many years to come, yet we have shown that the imaging alone, augmented when necessary with follow-up photometry in specific bands, can provide the classifications needed to explore these unknown populations

Using video as textural input to a computer graphic database

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1989.Includes bibliographical references (leaves 19-20).by Christopher P. Thorman.B.S

An improved method for object detection in astronomical images

This paper introduces an improved method for detecting objects of interest (galaxies and stars) in astronomical images. After applying a global detection scheme, further refinement is applied by dividing the entire image into several irregularly sized sub-regions using the watershed segmentation method. A more refined detection procedure is performed in each sub-region by applying adaptive noise reduction and a layered strategy to detect bright objects and faint objects, respectively. Finally, a multi-threshold technique is used to separate blended objects. On simulated data, this method can detect more real objects than SExtractor at comparable object counts (91 per cent versus 83 per cent true detections) and has an increased chance of successfully detecting very faint objects, up to 2 mag fainter than SExtractor on similar data. Our method has also been applied to real observational image data sets to verify its effectiveness

Characterizing and Propagating Modeling Uncertainties in Photometrically-Derived Redshift Distributions

The uncertainty in the redshift distributions of galaxies has a significant potential impact on the cosmological parameter values inferred from multi-band imaging surveys. The accuracy of the photometric redshifts measured in these surveys depends not only on the quality of the flux data, but also on a number of modeling assumptions that enter into both the training set and SED fitting methods of photometric redshift estimation. In this work we focus on the latter, considering two types of modeling uncertainties: uncertainties in the SED template set and uncertainties in the magnitude and type priors used in a Bayesian photometric redshift estimation method. We find that SED template selection effects dominate over magnitude prior errors. We introduce a method for parameterizing the resulting ignorance of the redshift distributions, and for propagating these uncertainties to uncertainties in cosmological parameters.Comment: 13 pages, 12 figures, version published in Ap

Does liming grasslands increase biomass productivity without causing detrimental impacts on net greenhouse gas emissions?

Acknowledgements This work contributes to the SUPER-G project (funded under EU Horizon 2020 programme). We appreciate the support from the Estonian Research Council (PRG352) and the European Regional Development Fund (Centre of Excellence EcolChange, Estonia).We are grateful to Sarah Perryman for proving us with pictures from the Park Grass Experiment.Peer reviewedPublisher PD

Permanent grasslands in Europe : Land use change and intensification decrease their multifunctionality

Acknowledgments We acknowledge the financial support of this work by European Union Horizon 2020 research and innovation programme, under grant agreement 774124, project SUPER-G (Developing Sustainable Permanent Grassland Systems and Policies).Peer reviewedPublisher PD

LSST Science Book, Version 2.0

A survey that can cover the sky in optical bands over wide fields to faint magnitudes with a fast cadence will enable many of the exciting science opportunities of the next decade. The Large Synoptic Survey Telescope (LSST) will have an effective aperture of 6.7 meters and an imaging camera with field of view of 9.6 deg^2, and will be devoted to a ten-year imaging survey over 20,000 deg^2 south of +15 deg. Each pointing will be imaged 2000 times with fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a total point-source depth of r~27.5. The LSST Science Book describes the basic parameters of the LSST hardware, software, and observing plans. The book discusses educational and outreach opportunities, then goes on to describe a broad range of science that LSST will revolutionize: mapping the inner and outer Solar System, stellar populations in the Milky Way and nearby galaxies, the structure of the Milky Way disk and halo and other objects in the Local Volume, transient and variable objects both at low and high redshift, and the properties of normal and active galaxies at low and high redshift. It then turns to far-field cosmological topics, exploring properties of supernovae to z~1, strong and weak lensing, the large-scale distribution of galaxies and baryon oscillations, and how these different probes may be combined to constrain cosmological models and the physics of dark energy.Comment: 596 pages. Also available at full resolution at http://www.lsst.org/lsst/sciboo

Devotions for Lent 2023 Hymns of Lent

This Lent, we will continue reflecting on hymns of faith, namely, some of our most beloved Lenten hymns. 10 such hymns have been chosen to fill the 40(+) days of Lent. Therefore, this devotional, different from previous editions, does not proceed on a weekly basis, but merely flows from one hymn to the next. Also different from previous editions, the devotional reflections are specifically based on the stanzas of the selected hymns. Therefore, each day’s reflection features the text of the hymn stanza, a devotion based on that stanza, a prayer, and then a Scripture passage or passages for further meditation. I pray these reflections may be of edification for you during this Lenten season.https://scholar.csl.edu/osp/1022/thumbnail.jp