How does particulate organic matter (POM) swelling affect soil -water interactions and soil structural stability on different scales?

Particulate organic matter (POM), root mucilage and synthetic polymers are swellable polymeric substances (“hydrogels”) which form a three-dimensional polymer network between soil particles. On the one hand, hydrogels can alter soil hydrological properties via their strong influence on water holding capacity and soil wettability. On the other hand, it has been recently shown that the presence of swollen hydrogel structures between soil particles can significantly contribute to soil structural stability. However, until now, only model polymer hydrogels have been used, and the findings still need to be transferred to soils which contain natural swellable organic substances. In this study, we investigated how the swelling of different POM fractions in soil contributes to soil-water-hydrogel interactions and to soil structural stability on different scales. We assumed that the swelling of easily available inter-aggregate POM (frPOM) and occluded intra-aggregate POM (iPOM) differ in their contribution to soil structural stability. For this purpose, we investigated the structural stability and soil-water interactions of a silty sand soil in a 2x2 nested design comprising tilled and non-tilled as well as compost-fertilized and non-fertilized sub-treatments. POM fractions were isolated by soil density fractionation and subsequently characterized for their swelling and water binding properties. Soil-water interactions in terms of water distribution and water mobility were assessed by one- and two-dimensional 1H-NMR relaxometry and pulsed-field-gradient (PFG) NMR. Results from 1H‑NMR measurements were linked with soil structural stability measurements conducted on the micro- and macroscale using soil rheology, wet sieving and crushing tests. On the micro- and macroscale, soil structural stability was higher for compost-fertilized samples than for non-fertilized with different effects of tillage. This was especially related to the presence of frPOM- and iPOM-associated water which revealed a significantly higher viscosity than mineral pore water. On the microscale, frPOM showed the highest contribution to soil structural stability, whereas iPOM predominantly stabilized the soil structure on the macroscale. The relationships suggest that the spatial location and hence the swellability of organic structures in soil could explain the nature of hydrogel-induced soil structural stability

Einfluss der Wurzel- und Regenwurmaktivität auf die Morphologie von Bioporen im Unterboden

Abstract Zugänglichkeit und Mobilisierung von Nährstoffressourcen aus dem Unterboden durch Bioporennetzwerke sind nach wie vor im Fokus aktueller Forschung [1][2][3]. Wichtig ist hierbei die Generierung von quantitativen Daten zu Eigenschaften der Rhizo-Drilosphäre und der Porenarchitektur. Um ein besseres Verständnis der 3D-Dynamik von Bioporen alspräferentielle Fließpfade undderen Effekt auf die Nährstoffaufnahme aus dem Untergrund zu erhalten, werden hoch aufgelöste dreidimensionale Rauminformationen benötigt. Mit der Röntgen-Mikrotomographie (μCT) und 3D-Bildanalyse wurden mikrostrukturelle Eigenschaften von Bioporennetzwerken, die durch Wurzeln und Regenwürmer erzeugt wurden, als Funktion des Abstandes von der Bioporenwandung bestimmt . Dazu wurden in 1 bis 10 mm Abstand die zugängliche Oberfläche, das Porenvolumen und die Porosität innerhalb der Rhizo-Drilosphäre quantifiziert. Erkenntnisse über den Einfluss der Bioporengenese auf die Porengeometrien und somit auf den potentiellen Gas- und Wasseraustausch zwischen dem Gesamtboden und der Rhizo-Drilosphäre führen wiederum zu einem besseren Verständnis über die Nährstoffzugänglichkeit und mikrobiologische Aktivität in den Bioporen

Beyond Spheroids and Discs: Classifications of CANDELS Galaxy Structure at 1.4 < z < 2 via Principal Component Analysis

Important but rare and subtle processes driving galaxy morphology and star-formation may be missed by traditional spiral, elliptical, irregular or S\'ersic bulge/disk classifications. To overcome this limitation, we use a principal component analysis of non-parametric morphological indicators (concentration, asymmetry, Gini coefficient, $M_{20}$, multi-mode, intensity and deviation) measured at rest-frame $B$-band (corresponding to HST/WFC3 F125W at 1.4 $10^{10} M_{\odot}$) galaxy morphologies. Principal component analysis (PCA) quantifies the correlations between these morphological indicators and determines the relative importance of each. The first three principal components (PCs) capture $\sim$75 per cent of the variance inherent to our sample. We interpret the first principal component (PC) as bulge strength, the second PC as dominated by concentration and the third PC as dominated by asymmetry. Both PC1 and PC2 correlate with the visual appearance of a central bulge and predict galaxy quiescence. PC1 is a better predictor of quenching than stellar mass, as as good as other structural indicators (S\'ersic-n or compactness). We divide the PCA results into groups using an agglomerative hierarchical clustering method. Unlike S\'ersic, this classification scheme separates compact galaxies from larger, smooth proto-elliptical systems, and star-forming disk-dominated clumpy galaxies from star-forming bulge-dominated asymmetric galaxies. Distinguishing between these galaxy structural types in a quantitative manner is an important step towards understanding the connections between morphology, galaxy assembly and star-formation.Comment: 31 pages, 24 figures, accepted for publication in MNRA

Keck-I MOSFIRE spectroscopy of compact star-forming galaxies at z≳\gtrsim2: High velocity dispersions in progenitors of compact quiescent galaxies

We present Keck-I MOSFIRE near-infrared spectroscopy for a sample of 13 compact star-forming galaxies (SFGs) at redshift $2\leq z \leq2.5$ with star formation rates of SFR$\sim$100M$_{\odot}$ y$^{-1}$ and masses of log(M/M$_{\odot}$)$\sim10.8$. Their high integrated gas velocity dispersions of $\sigma_{\rm{int}}$=230$^{+40}_{-30}$ km s$^{-1}$, as measured from emission lines of H$_{\alpha}$ and [OIII], and the resultant M$_{\star}-\sigma_{\rm{int}}$ relation and M$_{\star}$$-$M$_{\rm{dyn}}$ all match well to those of compact quiescent galaxies at $z\sim2$, as measured from stellar absorption lines. Since log(M$_{\star}$/M$_{\rm{dyn}}$)$=-0.06\pm0.2$ dex, these compact SFGs appear to be dynamically relaxed and more evolved, i.e., more depleted in gas and dark matter ($<$13$^{+17}_{-13}$\%) than their non-compact SFG counterparts at the same epoch. Without infusion of external gas, depletion timescales are short, less than $\sim$300 Myr. This discovery adds another link to our new dynamical chain of evidence that compact SFGs at $z\gtrsim2$ are already losing gas to become the immediate progenitors of compact quiescent galaxies by $z\sim2$.Comment: 12 pages, 7 figures, submitted to Ap

A Non-MLE Approach for Satellite Scatterometer Wind Vector Retrievals in Tropical Cyclones

Satellite microwave scatterometers are the principal source of global synoptic-scale ocean vector wind (OVW) measurements for a number of scientific and operational oceanic wind applications. However, for extreme wind events such as tropical cyclones, their performance is significantly degraded. This paper presents a novel OVW retrieval algorithm for tropical cyclones which improves the accuracy of scatterometer based ocean surface winds when compared to low-flying aircraft with in-situ and remotely sensed observations. Unlike the traditional maximum likelihood estimation (MLE) wind vector retrieval technique, this new approach sequentially estimates scalar wind directions and wind speeds. A detailed description of the algorithm is provided along with results for ten QuikSCAT hurricane overpasses (from 2003-2008) to evaluate the performance of the new algorithm. Results are compared with independent surface wind analyses from the National Oceanic and Atmospheric Administration (NOAA) Hurricane Research Division\u27s H*Wind surface analyses and with the corresponding SeaWinds Project\u27s L2B-12.5 km OVW products. They demonstrate that the proposed algorithm extends the SeaWinds capability to retrieve wind speeds beyond the current range of approximately 35 m/s (minimal hurricane category-1) with improved wind direction accuracy, making this new approach a potential candidate for current and future conically scanning scatterometer wind retrieval algorithms

CANDELS/GOODS-S, CDFS, ECDFS: Photometric Redshifts For Normal and for X-Ray-Detected Galaxies

We present photometric redshifts and associated probability distributions for all detected sources in the Extended Chandra Deep Field South (ECDFS). The work makes use of the most up-to-date data from the Cosmic Assembly Near-IR Deep Legacy Survey (CANDELS) and the Taiwan ECDFS Near-Infrared Survey (TENIS) in addition to other data. We also revisit multi-wavelength counterparts for published X-ray sources from the 4Ms-CDFS and 250ks-ECDFS surveys, finding reliable counterparts for 1207 out of 1259 sources ($\sim 96\%$). Data used for photometric redshifts include intermediate-band photometry deblended using the TFIT method, which is used for the first time in this work. Photometric redshifts for X-ray source counterparts are based on a new library of AGN/galaxy hybrid templates appropriate for the faint X-ray population in the CDFS. Photometric redshift accuracy for normal galaxies is 0.010 and for X-ray sources is 0.014, and outlier fractions are $4\%$ and $5.4\%$ respectively. The results within the CANDELS coverage area are even better as demonstrated both by spectroscopic comparison and by galaxy-pair statistics. Intermediate-band photometry, even if shallow, is valuable when combined with deep broad-band photometry. For best accuracy, templates must include emission lines.Comment: The paper has been accepted by ApJ. The materials we provide are available under [Surveys] > [CDFS] through the portal http://www.mpe.mpg.de/XraySurvey

CANDELS Multi-wavelength Catalogs: Source Detection and Photometry in the GOODS-South Field

We present a UV-to-mid infrared multi-wavelength catalog in the CANDELS/GOODS-S field, combining the newly obtained CANDELS HST/WFC3 F105W, F125W, and F160W data with existing public data. The catalog is based on source detection in the WFC3 F160W band. The F160W mosaic includes the data from CANDELS deep and wide observations as well as previous ERS and HUDF09 programs. The mosaic reaches a 5$\sigma$ limiting depth (within an aperture of radius 0.17 arcsec) of 27.4, 28.2, and 29.7 AB for CANDELS wide, deep, and HUDF regions, respectively. The catalog contains 34930 sources with the representative 50% completeness reaching 25.9, 26.6, and 28.1 AB in the F160W band for the three regions. In addition to WFC3 bands, the catalog also includes data from UV (U-band from both CTIO/MOSAIC and VLT/VIMOS), optical (HST/ACS F435W, F606W, F775W, F814W, and F850LP), and infrared (HST/WFC3 F098M, VLT/ISAAC Ks, VLT/HAWK-I Ks, and Spitzer/IRAC 3.6, 4.5, 5.8, 8.0 $\mu$m) observations. The catalog is validated via stellar colors, comparison with other published catalogs, zeropoint offsets determined from the best-fit templates of the spectral energy distribution of spectroscopically observed objects, and the accuracy of photometric redshifts. The catalog is able to detect unreddened star-forming (passive) galaxies with stellar mass of 10^{10}M_\odot at a 50% completeness level to z$\sim$3.4 (2.8), 4.6 (3.2), and 7.0 (4.2) in the three regions. As an example of application, the catalog is used to select both star-forming and passive galaxies at z$\sim$2--4 via the Balmer break. It is also used to study the color--magnitude diagram of galaxies at 0<z<4.Comment: The full resolution article is now published in ApJS (2013, 207, 24). 22 pages, 21 figures, and 5 tables. The catalogue is available on the CANDELS website: http://candels.ucolick.org/data_access/GOODS-S.html MAST: http://archive.stsci.edu/prepds/candels and Rainbow Database: https://arcoiris.ucolick.org/Rainbow_navigator_public and https://rainbowx.fis.ucm.es/Rainbow_navigator_publi