We present joint constraints on the distribution of Mg II absorption around high redshift galaxies obtained by combining two orthogonal probes, the integrated Mg II absorption seen in stacked ...background galaxy spectra and the distribution of parent galaxies of individual strong Mg II systems as seen in the spectra of background quasars. In general, we find that variations in the absorption strength with azimuthal angles provide much stronger constraints on the intrinsic geometry of the Mg II absorption than the dependence on the inclination of the galaxies. It is shown that either composite models consisting of a simple bipolar component plus a spherical or disk component, or a single highly softened bipolar distribution, can well represent the azimuthal dependencies observed in both the stacked spectrum and quasar absorption-line data sets within 40 kpc. We conclude that the distribution of Mg II gas at low impact parameters is not the same as that found at high impact parameters.
Photo-z performance for precision cosmology Bordoloi, R.; Lilly, S. J.; Amara, A.
Monthly notices of the Royal Astronomical Society,
August 2010, Letnik:
406, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Current and future weak-lensing surveys will rely on photometrically estimated redshifts of very large numbers of galaxies. In this paper, we address several different aspects of the demanding ...photo-z performance that will be required for future experiments, such as the proposed ESA Euclid mission. It is first shown that the proposed all-sky near-infrared photometry from Euclid, in combination with anticipated ground-based photometry (e.g. PanStarrs-2 or DES) should yield the required precision in individual photo-z of σz(z) ≤ 0.05(1 +z) at IAB≤ 24.5. Simple a priori rejection schemes based on the photometry alone can be tuned to recognize objects with wildly discrepant photo-z and to reduce the outlier fraction to ≤0.25 per cent with only modest loss of otherwise usable objects. Turning to the more challenging problem of determining the mean redshift 〈z〉 of a set of galaxies to a precision of |Δ〈z〉| ≤ 0.002(1 +z) we argue that, for many different reasons, this may be best accomplished by relying on the photo-z themselves rather than on the direct measurement of 〈z〉 from spectroscopic redshifts of a representative subset of the galaxies, as has usually been envisaged. We present in Appendix A an analysis of the substantial difficulties in the latter approach that arise from the presence of large-scale structure in spectroscopic survey fields. A simple adaptive scheme based on the statistical properties of the photo-z likelihood functions is shown to meet this stringent systematic requirement, although further tests on real data will be required to verify this. We also examine the effect of an imprecise correction for Galactic extinction on the photo-z and the precision with which the Galactic extinction can be determined from the photometric data itself, for galaxies with or without spectroscopic redshifts. We also explore the effects of contamination by fainter overlapping objects in photo-z determination. The overall conclusion of this paper is that the acquisition of photometrically estimated redshifts with the precision required for Euclid, or other similar experiments, will be challenging but possible.
Fertilization of nitrogen (N)-limited ecosystems by anthropogenic atmospheric nitrogen deposition (N
) may promote CO
removal from the atmosphere, thereby buffering human effects on global radiative ...forcing. We used the biogeochemical ecosystem model N14CP, which considers interactions among C (carbon), N and P (phosphorus), driven by a new reconstruction of historical N
, to assess the responses of soil organic carbon (SOC) stocks in British semi-natural landscapes to anthropogenic change. We calculate that increased net primary production due to N
has enhanced detrital inputs of C to soils, causing an average increase of 1.2 kgCm
(c. 10%) in soil SOC over the period 1750-2010. The simulation results are consistent with observed changes in topsoil SOC concentration in the late 20
Century, derived from sample-resample measurements at nearly 2000 field sites. More than half (57%) of the additional topsoil SOC is predicted to have a short turnover time (c. 20 years), and will therefore be sensitive to future changes in N
. The results are the first to validate model predictions of N
effects against observations of SOC at a regional field scale. They demonstrate the importance of long-term macronutrient interactions and the transitory nature of soil responses in the terrestrial C cycle.
We present H alpha integral field spectroscopy of well-resolved, UV/optically selected image star-forming galaxies as part of the SINS survey with SINFONI on the ESO VLT. Our laser guide star ...adaptive optics and good seeing data show the presence of turbulent rotating star-forming outer rings/disks, plus central bulge/inner disk components, whose mass fractions relative to the total dynamical mass appear to scale with the N ii/H alpha flux ratio and the star formation age. We propose that the buildup of the central disks and bulges of massive galaxies at image can be driven by the early secular evolution of gas-rich proto-disks. High-redshift disks exhibit large random motions. This turbulence may in part be stirred up by the release of gravitational energy in the rapid 'cold' accretion flows along the filaments of the cosmic web. As a result, dynamical friction and viscous processes proceed on a timescale of <1 Gyr, at least an order of magnitude faster than in image disk galaxies. Early secular evolution thus drives gas and stars into the central regions and can build up exponential disks and massive bulges, even without major mergers. Secular evolution along with increased efficiency of star formation at high surface densities may also help to account for the short timescales of the stellar buildup observed in massive galaxies at image.
Summary
The change in soil carbon (C) stock over a 19–31‐year period (mean 25 years) has been measured at 179 sites on a 20‐km grid across Scotland. Sampling was by horizon from a profile pit. ...Although soil bulk density determinations were absent at the first sampling time, we used bulk density values from the second sampling time calibrated against NIR spectra to predict the missing values. There was no detectable change in overall total soil C stock (mean ± standard error, to a depth of 100 cm), which was 266 ± 15 and 270 ± 15 t C ha−1 for the first and second sampling times, respectively, or generally in C stock within specific vegetation or soil types. The exception was for soils under woodland, excluding those on deep peat, which exhibited a significant (P = 0.05) gain of 1.0 t C ha−1 year−1. Soils under woodland (mainly coniferous plantation) also showed a significant (P = 0.04) increase in C content (g kg−1), a significant decrease in bulk density (P = 0.006) and an increase in the thickness of the Litter‐Fermentation‐Humus (LFH) layer (P = 0.06). Recalculating the C stock to a depth of 15 cm showed a significant increase in overall C stock (when deep peat sites were excluded) as well as specifically in moorland and woodland soils, suggesting that had we sampled only to 15 cm, we would have reached a different conclusion. Both improved grassland soils and those initially under arable cultivation showed a significant decrease in C content. However, the mean thickness of Ap horizons increased from 29 to 32 cm, with a concomitant decrease in C content and a slight increase in bulk density; this we ascribe to deeper ploughing between the sample periods. In the context of possible soil C losses, we can be 95% confident that the mean loss does not exceed 0.2% year−1 and 99% confident that it does not exceed 0.4% year−1.
Faraday rotation (rotation measure RM) probes of magnetic fields in the universe are sensitive to cosmological and evolutionary effects as z increases beyond image1 because of the scalings of ...electron density and magnetic fields, and the growth in the number of expected intersections with galaxy-scale intervenors, image. In this new global analysis of an unprecedented large sample of RMs of high-latitude quasars extending out to image, we find that the distribution of RM broadens with redshift in the 20-80 rad m super(-2 ) range, despite the super(-2) wavelength dilution expected in the observed Faraday rotation. Our results indicate that the universe becomes increasingly 'Faraday-opaque' to sources beyond image ; that is, as z increases, progressively fewer sources are found with a 'small' RM in the observer's frame. This is in contrast to sources at image. They suggest that the environments of galaxies were significantly magnetized at high redshifts, with magnetic field strengths that were at least as strong within a few Gyr of the big bang as at the current epoch. We separately investigate a simple unevolving toy model in which the RM is produced by Mg ii absorber systems, and find that it can approximately reproduce the observed trend with redshift. An additional possibility is that the intrinsic RM associated with the radio sources was much higher in the past, and we show that this is not a trivial consequence of the higher radio luminosities of the high-redshift sources.
The underground developments are likely to deteriorate the water quality, which causes damage to the structure. The pollutant levels largely affect the aquifer properties and alter the ...characteristics of the water quality. Ferritin nanoparticle usage proves to be an effective technology for reducing the pollutant level of the salts, which are likely to affect the underground structure. The observation wells are selected around the underground Metro Rail Corridor, and the secondary observation wells are selected around the corridors. Ferritin is a common iron storage protein as a powder used in the selected wells identified in the path of underground metro rail corridors. Water sampling was done to assess the water quality in the laboratory. The water quality index plots for the two phases (1995-2008) and (2009-2014) using GIS explains the water quality scenario before and after the Ferritin treatment. The Ferritin treatment in water was very effective in reducing the pollutants level of Fluoride and sulphate salts which is likely to bring damage to the structure.
ABSTRACT We present a spectroscopic survey of galaxies in the COSMOS field using the Fiber Multi-object Spectrograph (FMOS), a near-infrared instrument on the Subaru Telescope. Our survey is ...specifically designed to detect the H emission line that falls within the H-band (1.6-1.8 m) spectroscopic window from star-forming galaxies with 1.4 < z < 1.7 and Mstellar 1010 M . With the high multiplex capability of FMOS, it is now feasible to construct samples of over 1000 galaxies having spectroscopic redshifts at epochs that were previously challenging. The high-resolution mode (R ∼ 2600) effectively separates H and N iiλ6585, thus enabling studies of the gas-phase metallicity and photoionization state of the interstellar medium. The primary aim of our program is to establish how star formation depends on stellar mass and environment, both recognized as drivers of galaxy evolution at lower redshifts. In addition to the main galaxy sample, our target selection places priority on those detected in the far-infrared by Herschel/PACS to assess the level of obscured star formation and investigate, in detail, outliers from the star formation rate (SFR)-stellar mass relation. Galaxies with H detections are followed up with FMOS observations at shorter wavelengths using the J-long (1.11-1.35 m) grating to detect Hβ and O iiiλ5008 which provides an assessment of the extinction required to measure SFRs not hampered by dust, and an indication of embedded active galactic nuclei. With 460 redshifts measured from 1153 spectra, we assess the performance of the instrument with respect to achieving our goals, discuss inherent biases in the sample, and detail the emission-line properties. Our higher-level data products, including catalogs and spectra, are available to the community.
We have studied the properties of giant star-forming clumps in five z {approx} 2 star-forming disks with deep SINFONI AO spectroscopy at the ESO VLT. The clumps reside in disk regions where the ...Toomre Q-parameter is below unity, consistent with their being bound and having formed from gravitational instability. Broad H{alpha}/N II line wings demonstrate that the clumps are launching sites of powerful outflows. The inferred outflow rates are comparable to or exceed the star formation rates, in one case by a factor of eight. Typical clumps may lose a fraction of their original gas by feedback in a few hundred million years, allowing them to migrate into the center. The most active clumps may lose much of their mass and disrupt in the disk. The clumps leave a modest imprint on the gas kinematics. Velocity gradients across the clumps are 10-40 km s{sup -1} kpc{sup -1}, similar to the galactic rotation gradients. Given beam smearing and clump sizes, these gradients may be consistent with significant rotational support in typical clumps. Extreme clumps may not be rotationally supported; either they are not virialized or they are predominantly pressure supported. The velocity dispersion is spatially rather constant and increases only weakly with star formation surface density. The large velocity dispersions may be driven by the release of gravitational energy, either at the outer disk/accreting streams interface, and/or by the clump migration within the disk. Spatial variations in the inferred gas phase oxygen abundance are broadly consistent with inside-out growing disks, and/or with inward migration of the clumps.
We present the Zurich Extragalactic Bayesian Redshift Analyzer (zebra). The current version of zebra combines and extends several of the classical approaches to produce accurate photometric redshifts ...down to faint magnitudes. In particular, zebra uses the template-fitting approach to produce Maximum Likelihood and Bayesian redshift estimates based on the following points.
An automatic iterative technique to correct the original set of galaxy templates to best represent the Spectral Energy Distributions (SEDs) of real galaxies at different redshifts.
A training set of spectroscopic redshifts for a small fraction of the photometric sample to improve the robustness of the photometric redshift estimates.
An iterative technique for Bayesian redshift estimates, which extracts the full two-dimensional redshift and template probability function for each galaxy.
We demonstrate the performance of zebra by applying it to a sample of 866 I
AB
≤ 22.5 COSMOS galaxies with available u*, B, V, g′, r′, i′, z′ and K
s
photometry and zCOSMOS spectroscopic redshifts in the range 0 < z < 1.3. Adopting a 5σ clipping that excludes ≤10 galaxies, both the Maximum Likelihood and Bayesian zebra estimates for this sample have an accuracy σΔz/(1+z) smaller than 0.03. Similar accuracies are recovered using mock galaxies.
zebra is made available at http://www.exp-astro.phys.ethz.ch/ZEBRA.
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