Tolerable versus actual soil erosion rates in Europe

Erosion is a major threat to soil resources in Europe, and may impair their ability to deliver a range of ecosystem goods and services. This is reflected by the European Commission's Thematic Strategy for Soil Protection, which recommends an indicator-based approach for monitoring soil erosion. Defined baseline and threshold values are essential for the evaluation of soil monitoring data. Therefore, accurate spatial data on both soil loss and soil genesis are required, especially in the light of predicted changes in climate patterns, notably frequency, seasonal distribution and intensity of precipitation. Rates of soil loss are reported that have been measured, modelled or inferred for most types of soil erosion in a variety of landscapes, by studies across the spectrum of the Earth sciences. Natural rates of soil formation can be used as a basis for setting tolerable soil erosion rates, with soil formation consisting of mineral weathering as well as dust deposition. This paper reviews the concept of tolerable soil erosion and summarises current knowledge on rates of soil formation, which are then compared to rates of soil erosion by known erosion types, for assessment of soil erosion monitoring at the European scale

Squelched Galaxies and Dark Halos

There is accumulating evidence that the faint end of the galaxy luminosity function might be very different in different locations. The luminosity function might be rising in rich clusters and flat or declining in regions of low density. If galaxies form according to the model of hierarchical clustering then there should be many small halos compared to the number of big halos. If this theory is valid then there must be a mechanism that eliminates at least the visible component of galaxies in low density regions. A plausible mechanism is photoionization of the intergalactic medium at a time before the epoch that most dwarf galaxies form in low density regions but after the epoch of formation for similar systems that ultimately end up in rich clusters. The dynamical timescales are found to accommodate this hypothesis in a flat universe with Omega_m < 0.4. If small halos exist but simply cannot be located because they have never become the sites of significant star formation, they still might have dynamical manifestations. These manifestations are hard to identify in normal groups of galaxies because small halos do not make a significant contribution to the global mass budget. However, it could be entertained that there are clusters of halos where there are only small systems, clusters that are at the low mass end of the hierarchical tree. There may be places where only a few small galaxies managed to form, enough for us to identify and use as test probes of the potential. It turns out that such environments might be common. Four probable groups of dwarfs are identified within 5 Mpc and the assumption they are gravitationally bound suggests M/L_B ~ 300 - 1200 M_sun/L_sun, 6 +/- factor 2 times higher than typical values for groups with luminous galaxies.Comment: Accepted ApJ 569, (April 20), 2002, 12 pages, 6 figures, 1 tabl

The Kinematics in the Core of the Low Surface Brightness Galaxy DDO 39

We present a high resolution, SparsePak two-dimensional velocity field for the center of the low surface brightness (LSB) galaxy DDO 39. These data are a significant improvement on previous HI or Halpha long slit data, yet the inner rotation curve is still uncertain due to significant noncircular and random motions. These intrinsic uncertainties, probably present in other LSB galaxies too, result in a wide range of inner slopes being consistent with the data, including those expected in cold dark matter (CDM) simulations. The halo concentration parameter provides a more useful test of cosmological models than the inner slope as it is more tightly constrained by observations. DDO 39's concentration parameter is consistent with, but on the low end of the distribution predicted by CDM.Comment: 4 pages, accepted for publication in ApJ Letter

The curious case of J113924.74+164144.0: a possible new group of galaxies at z = 0.0693

J113924.74+164144.0 is an interesting galaxy at z = 0.0693, i.e. D_L ~ 305 Mpc, with tidal-tail-like extended optical features on both sides. There are two neighbouring galaxies, a spiral galaxy J113922.85+164136.3 which has a strikingly similar 'tidal' morphology, and a faint galaxy J113923.58+164129.9. We report HI 21 cm observations of this field to search for signatures of possible interaction. Narrow HI emission is detected from J113924.74+164144.0, but J113922.85+164136.3 shows no detectable emission. The total HI mass detected in J113924.74+164144.0 is 7.7 x 10^9 M_solar. The HI emission from the galaxy is found to be extended and significantly offset from the optical position of the galaxy. We interpret this as signature of possible interaction with the neighbouring spiral galaxy. There is also a possible detection of HI emission from another nearby galaxy J113952.31+164531.8 at z = 0.0680 at a projected distance of 600 kpc, and with a total HI mass of 5.3 x 10^9 M_solar, suggesting that all these galaxies form a loose group at z ~ 0.069.Comment: 5 pages, 1 table, 6 figures. Accepted for publication in MNRAS Letters. The definitive version will be available at http://www.blackwell-synergy.com

Star Formation and Tidal Encounters with the Low Surface Brightness Galaxy UGC 12695 and Companions

We present VLA H I observations of the low surface brightness galaxy UGC 12695 and its two companions, UGC 12687 and a newly discovered dwarf galaxy 2333+1234. UGC 12695 shows solid body rotation but has a very lopsided morphology of the H I disk, with the majority of the H I lying in the southern arm of the galaxy. The H I column density distribution of this very blue, LSB galaxy coincides in detail with its light distribution. Comparing the H I column density of UGC 12695 with the empirical (but not well understood) value of Sigma_c = 10E21 atoms/cm^2 found in, i.e., Skillman's 1986 paper shows the star formation to be a local affair, occurring only in those regions where the column density is above this star formation threshold. The low surface brightness nature of this galaxy could thus be attributed to an insufficient gas surface density, inhibiting star formation on a more global scale. Significantly, though, the Toomre criterion places a much lower critical density on the galaxy (+/-10E20 atoms/cm^2), which is shown by the galaxy's low SFR to not be applicable. Within a projected distance of 300kpc/30kms of UGC 12695 lie two companion galaxies - UGC 12687, a high surface brightness barred spiral galaxy, and 2333+1234, a dwarf galaxy discovered during this investigation. The close proximity of the three galaxies, combined with UGC 12695's extremely blue color and regions of localized starburst and UGC 12687's UV excess bring to mind mutually induced star formation through tidal activity.Comment: 14 pages, 8 figures (2 color), To be published in A.J., May 2000

Applying infrared thermography to soil surface temperature monitoring: Case study of a high-resolution 48 h survey in a vineyard (Anadia, Portugal)

The soil surface albedo decreases with an increasing biochar application rate as a power decay function, but the net impact of biochar application on soil temperature dynamics remains to be clarified. The objective of this study was to assess the potential of infrared thermography (IRT) sensing by monitoring soil surface temperature (SST) with a high spatiotemporal and thermal resolution in a scalable agricultural application. We monitored soil surface temperature (SST) variations over a 48 h period for three treatments in a vineyard: bare soil (plot S), 100% biochar cover (plot B), and biochar-amended topsoil (plot SB). The SST of all plots was monitored at 30 min intervals with a tripod-mounted IR thermal camera. The soil temperature at 10 cm depth in the S and SB plots was monitored continuously with a 5 min resolution probe. Plot B had greater daily SST variations, reached a higher daily temperature peak relative to the other plots, and showed a faster rate of T increase during the day. However, on both days, the SST of plot B dipped below that of the control treatment (plot S) and biochar-amended soil (plot SB) from about 18:00 onward and throughout the night. The diurnal patterns/variations in the IRT-measured SSTs were closely related to those in the soil temperature at a 10 cm depth, confirming that biochar-amended soils showed lower thermal inertia than the unamended soil. The experiment provided interesting insights into SST variations at a local scale. The case study may be further developed using fully automated SST monitoring protocols at a larger scale for a range of environmental and agricultural applications

Electrodynamics of superconductors

An alternate set of equations to describe the electrodynamics of superconductors at a macroscopic level is proposed. These equations resemble equations originally proposed by the London brothers but later discarded by them. Unlike the conventional London equations the alternate equations are relativistically covariant, and they can be understood as arising from the 'rigidity' of the superfluid wave function in a relativistically covariant microscopic theory. They predict that an internal 'spontaneous' electric field exists in superconductors, and that externally applied electric fields, both longitudinal and transverse, are screened over a London penetration length, as magnetic fields are. The associated longitudinal dielectric function predicts a much steeper plasmon dispersion relation than the conventional theory, and a blue shift of the minimum plasmon frequency for small samples. It is argued that the conventional London equations lead to difficulties that are removed in the present theory, and that the proposed equations do not contradict any known experimental facts. Experimental tests are discussed.Comment: Small changes following referee's and editor's comments; to be published in Phys.Rev.

Self-consistent nonspherical isothermal halos embedding zero-thickness disks

Disk-halo decompositions of galaxy rotation curves are generally performed in a parametric way. We construct self-consistent models of nonspherical isothermal halos embedding a zero-thickness disk, by assuming that the halo distribution function is a Maxwellian. The method developed here can be used to study other physically-based choices for the halo distribution function and the case of a disk accompanied by a bulge. In a preliminary investigation we note the existence of a fine tuning between the scalelengths R_{\Omega} and h, respectively characterizing the rise of the rotation curve and the luminosity profile of the disk, which surprisingly applies to both high surface brightness and low surface brightness galaxies. This empirical correlation identifies a much stronger conspiracy than the one required by the smoothness and flatness of the rotation curve (disk-halo conspiracy). The self-consistent models are characterized by smooth and flat rotation curves for very different disk-to-halo mass ratios, hence suggesting that conspiracy is not as dramatic as often imagined. For a typical rotation curve, with asymptotically flat rotation curve at V_{\infty} (the precise value of which can also be treated as a free parameter), and a typical density profile of the disk, self-consistent models are characterized by two dimensionless parameters, which correspond to the dimensional scales (the disk mass-to-light ratio M/L and the halo central density) of standard disk-halo decompositions. We show that if the rotation curve is decomposed by means of our self-consistent models, the disk-halo degeneracy is removed and typical rotation curves are fitted by models that are below the maximum-disk prescription. Similar results are obtained from a study of NGC 3198. Finally, we quantify the flattening of the spheroidal halo, which is significant, especially on the scale of the visible disk.Comment: accepted for publication in A&

The line-of-sight warp of the spiral galaxy ESO 123-G23

We present 3-D modelling of the distribution and kinematics of the neutral hydrogen in the spiral galaxy ESO 123-G23. The optical appearance of this galaxy is an almost perfectly edge-on disk, while the neutral hydrogen is found to extend vertically out to about 15 kpc on either side of the galactic plane. The HI layer and the major features of the HI data cube can be successfully explained by a model dominated by a strong (about 30 degrees) line-of-sight warp. Other models were tried, including a flare model and a two-component model, but they clearly do not reproduce the data. This is the first unambiguous detection of a galactic warp that has the maximum deviation from the central plane almost along the line-of-sight. No evidence for the presence of any companion galaxy is found in the HI data cube. Line-of-sight warps in edge-on galaxies are probably frequent, but escape detection as they are too weak. Moreover they may easily be mistaken as flares or 'thick disks'. A 3-D modelling of the HI layer as the one presented here is needed in order to distinguish between these possibilities.Comment: 5 pages, 5 figures, accepted by A&

Morphologies and stellar populations of galaxies in the core of Abell 2218

SUMMARIZED ABSTRACT: We present a study of the stellar populations and morphologies of galaxies in the core of the galaxy cluster Abell 2218. Integral field spectroscopy was obtained using PMAS/[email protected] CAHA to obtain a complete flux limited sample of cluster members within its field-of-view (~74"X64"). In addition of 31 galaxies with known redshifts in the outer regions, we built up a final sample of 59 spectroscopically confirmed cluster members. Multiban photometry and detailed morphologies were obtained using deep images taken with the HST/ACS camera in the BVRI and z-bands. The CM diagram shows that the E-type galaxies cover the range of brighter and redder colors. A large fraction of spiral galaxies ($\sim$50%) is found. They cover a wide range in colors. This result, together with the distributions of ages, metallicities and masses, indicates that E-type galaxies are more massive and have older stellar populations, while L-type galaxies are less massive and have a wider range of stellar Our results agree with a proposed two-step scenario for the evolution of galaxies in clusters. In addition, an extremely blue merging galaxy system is found at the core, with the nominal redshift of the cluster.Comment: 29 pages, 17 figures, accepted for publishing in MNRAS. (HST/ACS composite image: http://www.caha.es/sanchez/abell2218/BRI_big.jpg