Multitemporal and Multispectral Remote Sensing of Soils in Cultured Landscapes of North Germany

Different techniques have been tested since 1974 to meet the difficult task of soil remote sensing in intensively cultured and small-parcelled landscapes of North Germany. Conventional stereo - interpretation of physiographic elements and patterns of landscapes by pan, color and infrared air photographs lowers the necessary number of soil borings and the cost of survey appreciably as well as increasing the information content and accuracy of soil maps. Especially, man-induced soil erosion and accumulation of hilly young moraines, position of sand dunes and old river beds on outwash terraces and appearance of periglacial polygon soils on flattened old moraines, only partly or not detectable in the field, were made visible with remote sensing. To increase the information content of remote sensing data and make interpretation more reproducible the multispectral remission was measured by an 11-channel-scanner. These data were calibrated by spectral photometry of soil samples within the wavelength range of 250 - 1400 nm to estimate by multiple regression analysis soil components, especially organic matter, free iron and clay. Additional information was achieved by measuring three times a day the multitemporal thermal emission with the scanner in autumn and spring of test areas. The data were interpreted by experiments in the field and laboratory, which measured the heat balance of soils in relation to external factors and the soil moisture regime

The PAU Survey: a new constraint on galaxy formation models using the observed colour redshift relation

We use the GALFORM semi-analytical galaxy formation model implemented in the Planck Millennium N-body simulation to build a mock galaxy catalogue on an observer’s past lightcone. The mass resolution of this N-body simulation is almost an order of magnitude better than in previous simulations used for this purpose, allowing us to probe fainter galaxies and hence build a more complete mock catalogue at low redshifts. The high time cadence of the simulation outputs allows us to make improved calculations of galaxy properties and positions in the mock. We test the predictions of the mock against the Physics of the Accelerating Universe Survey, a narrow-band imaging survey with highly accurate and precise photometric redshifts, which probes the galaxy population over a lookback time of 8 billion years. We compare the model against the observed number counts, redshift distribution, and evolution of the observed colours and find good agreement; these statistics avoid the need for model-dependent processing of the observations. The model produces red and blue populations that have similar median colours to the observations. However, the bimodality of galaxy colours in the model is stronger than in the observations. This bimodality is reduced on including a simple model for errors in the GALFORM photometry. We examine how the model predictions for the observed galaxy colours change when perturbing key model parameters. This exercise shows that the median colours and relative abundance of red and blue galaxies provide constraints on the strength of the feedback driven by supernovae used in the model

The PAU survey: measurements of the 4000 rA spectral break with narrow-band photometry

Galaxie

Lyman continuum leaker candidates among highly ionised, low-redshift dwarf galaxies selected from He

Context. Contemporary research suggests that the reionisation of the intergalactic medium (IGM) in the early Universe was predominantly realised by star-forming (proto-)galaxies (SFGs). Due to observational constraints, our knowledge on the origins of sufficient amounts of ionising Lyman continuum (LyC) photons and the mechanisms facilitating their transport into the IGM remains sparse. Recent efforts have thus focussed on the study of local analogues to these high-redshift objects. Aims. We aim to acquire a set of very low-redshift SFGs that exhibit signs of a hard radiation field being present. A subsequent analysis of their emission line properties is intended to shed light on how the conditions prevalent in these objects compare to those predicted to be present in early SFGs that are thought to be LyC emitters (LCEs). Methods. We used archival spectroscopic SDSS DR12 data to select a sample of low-redshift He I

The PAU survey: measurements of the 4000 rA spectral break with narrow-band photometry

The D4000 spectral break index is one of the most important features in the visible spectrum, as it is a proxy for stellar ages and is also used in galaxy classification. However, its direct measurement has always been reserved to spectroscopy. Here, we present a general method to directly measure the D4000 with narrow-band (NB) photometry; it has been validated using realistic simulations, and then evaluated with PAUS NBs, cross-matched with VIPERS spectra (iAB 3. The cigale D4000n has [SNR ]∼ 20, but underestimates the error by >50 per cent. Furthermore, the direct method recreates well the D4000-SFR relation, as well as the D4000-mass relation for blue galaxies (for red galaxies, selection effects impact the results). On the other hand, cigale accurately classifies galaxies into red and blue populations. We conclude that the direct measurement of D4000 with narrow-band photometry is a promising tool to determine average properties of galaxy samples, with results compatible with spectroscopy

Euclid. I. Overview of the Euclid mission

International audienceThe current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. Euclid is a medium-class mission in the Cosmic Vision 2015-2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14,000 deg^2 of extragalactic sky. In addition to accurate weak lensing and clustering measurements that probe structure formation over half of the age of the Universe, its primary probes for cosmology, these exquisite data will enable a wide range of science. This paper provides a high-level overview of the mission, summarising the survey characteristics, the various data-processing steps, and data products. We also highlight the main science objectives and expected performance