Spitzer observations of extragalactic H II regions - III. NGC 6822 and the hot star, H II region connection

Using the short-high module of the Infrared Spectrograph on the Spitzer Space Telescope, we have measured the [S IV] 10.51, [Ne II] 12.81, [Ne III] 15.56, and [S III] 18.71-micron emission lines in nine H II regions in the dwarf irregular galaxy NGC 6822. These lines arise from the dominant ionization states of the elements neon (Ne$^{++}$, Ne$^+$) and sulphur (S$^{3+}$, S$^{++}$), thereby allowing an analysis of the neon to sulphur abundance ratio as well as the ionic abundance ratios Ne$^+$/Ne$^{++}$ and S$^{3+}$/S$^{++}$. By extending our studies of H II regions in M83 and M33 to the lower metallicity NGC 6822, we increase the reliability of the estimated Ne/S ratio. We find that the Ne/S ratio appears to be fairly universal, with not much variation about the ratio found for NGC 6822: the median (average) Ne/S ratio equals 11.6 (12.2$\pm$0.8). This value is in contrast to Asplund et al.'s currently best estimated value for the Sun: Ne/S = 6.5. In addition, we continue to test the predicted ionizing spectral energy distributions (SEDs) from various stellar atmosphere models by comparing model nebulae computed with these SEDs as inputs to our observational data, changing just the stellar atmosphere model abundances. Here we employ a new grid of SEDs computed with different metallicities: Solar, 0.4 Solar, and 0.1 Solar. As expected, these changes to the SED show similar trends to those seen upon changing just the nebular gas metallicities in our plasma simulations: lower metallicity results in higher ionization. This trend agrees with the observations.Comment: 22 pages, 13 figures. To be published in MNRAS. reference added and typos fixed. arXiv admin note: text overlap with arXiv:0804.0828, which is paper II by Rubin et al. (2008

Animal waste management

"71/1M""Livestock producers have asked for guidelines on animal waste management that will be feasible and enduring. The Missouri Water Pollution Board has been aware of the need for improvements in methods of handling waste from confined feeding operations and for guidelines for producers. Chapter 204 of Missouri Statutes, as amended, gives the Water Pollution Board the responsibility and authority to correct and/or prevent "pollution" of "waters of the state." These terms are defined in the law and discussed briefly in the first section. With these facts in mind, staff engineers of the Water Pollution Board held a series of meetings with staff members of the Extension Division and Department of Agricultural Engineering of the University of Missouri-Columbia to develop guidelines for disposing of waste from confinement feeding operations. This report is a result of their combined efforts. Others assisting with various phases of development of these guidelines included: School of Engineering, University of Missouri-Columbia; State Department of Health, and the Soil Conservation Service. Research data and experience in handling livestock wastes have been used to develop the guidelines for planning, design, construction, and management of alternative systems of livestock waste management. The information and design guidelines herein are intended primarily for the use of personnel in agencies concerned with animal waste management problems." --PrefaceMissouri Water Pollution Board and Extension Division, University of Missouri - Columbia

\u3cem\u3eSpitzer\u3c/em\u3e Reveals what is Behind Orion\u27s Bar

We present Spitzer Space Telescope observations of 11 regions south-east (SE) of the Bright Bar in the Orion Nebula, along a radial from the exciting star θ1 Ori C, extending from 2.6 to 12.1 arcmin. Our Cycle 5 programme obtained deep spectra with matching Infrared Spectrograph (IRS) short-high (SH) and long-high (LH) aperture grid patterns. Most previous IR missions observed only the inner few arcmin (the ‘Huygens’ Region). The extreme sensitivity of Spitzer in the 10–37 μm spectral range permitted us to measure many lines of interest to much larger distances from θ1 Ori C. Orion is the benchmark for studies of the interstellar medium, particularly for elemental abundances. Spitzer observations provide a unique perspective on the neon and sulphur abundances by virtue of observing the dominant ionization states of Ne (Ne+, Ne++) and S (S++, S3 +) in Orion and H II regions in general. The Ne/H abundance ratio is especially well determined, with a value of (1.02 ± 0.02) × 10−4 or in terms of the conventional expression, 12 + log(Ne/H) = 8.01 ± 0.01. We obtained corresponding new ground-based spectra at Cerro Tololo Inter-American Observatory (CTIO). These optical data are used to estimate the electron temperature, electron density, optical extinction and the S+/S++ ionization ratio at each of our Spitzer positions. That permits an adjustment for the total gas-phase sulphur abundance because no S+ line is observed by Spitzer. The gas-phase S/H abundance ratio is (7.68 ± 0.25) × 10−6 or 12 + log(S/H) = 6.89 ± 0.02. The Ne/S abundance ratio may be determined even when the weaker hydrogen line, H(7–6) here, is not measured. The mean value, adjusted for the optical S+/S++ ratio, is Ne/S =13.0 ± 0.2. We derive the electron density (Ne) versus distance from θ1 Ori C for [S III] (Spitzer) and [S II] (CTIO). Both distributions are for the most part decreasing with increasing distance. The values for Ne[S II] fall below those of Ne[S III] at a given distance except for the outermost position. This general trend is consistent with the commonly accepted blister model for the Orion Nebula. The natural shape of such a blister is concave with an underlying decrease in density with increasing distance from the source of photoionization. Our spectra are the deepest ever taken in these outer regions of Orion over the 10–37 μm range. Tracking the changes in ionization structure via the line emission to larger distances provides much more leverage for understanding the far less studied outer regions. A dramatic find is the presence of high-ionization Ne++ all the way to the outer optical boundary ∼12 arcmin from θ1 Ori C. This IR result is robust, whereas the optical evidence from observations of high-ionization species (e.g. O++) at the outer optical boundary suffers uncertainty because of scattering of emission from the much brighter inner Huygens Region. The Spitzerspectra are consistent with the Bright Bar being a high-density ‘localized escarpment’ in the larger Orion Nebula picture. Hard ionizing photons reach most solid angles well SE of the Bright Bar. The so-called Orion foreground ‘Veil’, seen prominently in projection at our outermost position 12 arcmin from θ1 Ori C, is likely an H II region–photo-dissociation region (PDR) interface. The Spitzer spectra show very strong enhancements of PDR lines –[Si II] 34.8 μm, [Fe II] 26.0 μm and molecular hydrogen – at the outermost position

Spitzer reveals what's behind Orion's Bar

We present Spitzer Space Telescope observations of 11 regions SE of the Bright Bar in the Orion Nebula, along a radial from the exciting star theta1OriC, extending from 2.6 to 12.1'. Our Cycle 5 programme obtained deep spectra with matching IRS short-high (SH) and long-high (LH) aperture grid patterns. Most previous IR missions observed only the inner few arcmin. Orion is the benchmark for studies of the ISM particularly for elemental abundances. Spitzer observations provide a unique perspective on the Ne and S abundances by virtue of observing the dominant ionization states of Ne (Ne+, Ne++) and S (S++, S3+) in Orion and H II regions in general. The Ne/H abundance ratio is especially well determined, with a value of (1.01+/-0.08)E-4. We obtained corresponding new ground-based spectra at CTIO. These optical data are used to estimate the electron temperature, electron density, optical extinction, and the S+/S++ ratio at each of our Spitzer positions. That permits an adjustment for the total gas-phase S abundance because no S+ line is observed by Spitzer. The gas-phase S/H abundance ratio is (7.68+/-0.30)E-6. The Ne/S abundance ratio may be determined even when the weaker hydrogen line, H(7-6) here, is not measured. The mean value, adjusted for the optical S+/S++ ratio, is Ne/S = 13.0+/-0.6. We derive the electron density versus distance from theta1OriC for [S III] and [S II]. Both distributions are for the most part decreasing with increasing distance. A dramatic find is the presence of high-ionization Ne++ all the way to the outer optical boundary ~12' from theta1OriC. This IR result is robust, whereas the optical evidence from observations of high-ionization species (e.g. O++) at the outer optical boundary suffers uncertainty because of scattering of emission from the much brighter inner Huygens Region.Comment: 60 pages, 16 figures, 10 tables. MNRAS accepte

Quantification and analysis of icebergs in a tidewater glacier fjord using an object-based approach

Tidewater glaciers are glaciers that terminate in, and calve icebergs into, the ocean. In addition to the influence that tidewater glaciers have on physical and chemical oceanography, floating icebergs serve as habitat for marine animals such as harbor seals (Phoca vitulina richardii). The availability and spatial distribution of glacier ice in the fjords is likely a key environmental variable that influences the abundance and distribution of selected marine mammals; however, the amount of ice and the fine-scale characteristics of ice in fjords have not been systematically quantified. Given the predicted changes in glacier habitat, there is a need for the development of methods that could be broadly applied to quantify changes in available ice habitat in tidewater glacier fjords. We present a case study to describe a novel method that uses object-based image analysis (OBIA) to classify floating glacier ice in a tidewater glacier fjord from high-resolution aerial digital imagery. Our objectives were to (i) develop workflows and rule sets to classify high spatial resolution airborne imagery of floating glacier ice; (ii) quantify the amount and fine-scale characteristics of floating glacier ice; (iii) and develop processes for automating the object-based analysis of floating glacier ice for large number of images from a representative survey day during June 2007 in Johns Hopkins Inlet (JHI), a tidewater glacier fjord in Glacier Bay National Park, southeastern Alaska. On 18 June 2007, JHI was comprised of brash ice ([Formula: see text] = 45.2%, SD = 41.5%), water ([Formula: see text] = 52.7%, SD = 42.3%), and icebergs ([Formula: see text] = 2.1%, SD = 1.4%). Average iceberg size per scene was 5.7 m2 (SD = 2.6 m2). We estimate the total area (± uncertainty) of iceberg habitat in the fjord to be 455,400 ± 123,000 m2. The method works well for classifying icebergs across scenes (classification accuracy of 75.6%); the largest classification errors occur in areas with densely-packed ice, low contrast between neighboring ice cover, or dark or sediment-covered ice, where icebergs may be misclassified as brash ice about 20% of the time. OBIA is a powerful image classification tool, and the method we present could be adapted and applied to other ice habitats, such as sea ice, to assess changes in ice characteristics and availability

Glacier area changes in the Arctic and high latitudes using satellite remote sensing

ABSTRACTGlaciers have been retreating over the last century as a result of climate change, particularly in the Arctic, causing sea levels to rise, affecting coastal communities and potentially changing global weather and climate patterns. In this study, we mapped 2203 glaciers in Novaya Zemlya (Russian Arctic), Penny Ice Cap (Baffin Island), Disko Island (Qeqertarsuaq, Greenland) and part of Kenai (Alaska), using Object-Based Image Analysis (OBIA) applied to multispectral Landsat satellite imagery in Google Earth Engine (GEE) to quantify the glacier area changes over three decades. Between 1985–89 and 2019–21, the results show that the overall glacier area loss in Novaya Zemlya is 1319 ± 419 km2 (5.7% of area), 452 ± 227 km2 (6.6%) for Penny Ice Cap, 457 ± 168 km2 (23.6%) in Disko Island and 196 ± 84 km2 (25.7%) in Kenai. A total of seventy-three glaciers have disappeared completely, including sixty-nine on Disko Island, three in Novaya Zemlya and one in Kenai

Spatial and numerical distribution of brash ice within Johns Hopkins Inlet.

<p>(a)Distribution of brash ice in Johns Hopkins Inlet on 18 June 2007, as a percentage of each aerial image. Histogram (blue) and probability density functions (PDF) (red) for percent coverage of brash ice (b) and water (c).</p

Workflow from aerial image acquisition to generation of distribution maps and statistics for seals and icebergs.

<p>Workflow from aerial image acquisition to generation of distribution maps and statistics for seals and icebergs.</p