Light-cone distortion of the clustering and abundance of massive galaxies at high redshifts

Observational surveys of galaxies are not trivially related to single-epoch snapshots from computer simulations. Observationally, an increase in the distance along the line of sight corresponds to an earlier cosmic time at which the properties of the surveyed galaxy population may change. The effect of observing a survey volume along the light cone must be considered in the regime where the mass function of galaxies varies exponentially with redshift. This occurs when the haloes under consideration are rare, that is either when they are very massive or observed at high redshift. While the effect of the light cone is negligible for narrow-band surveys of Lyα emitters, it can be significant for dropout surveys of Lyman-break galaxies (LBGs) where the selection functions of the photometric bands are broad. Since there are exponentially more haloes at the low-redshift end of the survey, the low-redshift tail of the selection function contains a disproportionate fraction of the galaxies observed in the survey. This leads to a redshift probability distribution for the dropout LBGs with a mean less than that of the photometric selection function (PHSF) by an amount of order the standard deviation of the PHSF. The inferred mass function of galaxies is then shallower than the true mass function at a single redshift with the abundance at the high-mass end being twice or more as large as expected. Moreover, the statistical moments of the count of galaxies calculated ignoring the light-cone effect deviate from the actual values.     

The difference PDF of 21-cm fluctuations: a powerful statistical tool for probing cosmic reionization

A new generation of radio telescopes are currently being built with the goal of tracing the cosmic distribution of atomic hydrogen at redshifts 6–15 through its 21-cm line. The observations will probe the large-scale brightness fluctuations sourced by ionization fluctuations during cosmic reionization. Since detailed maps will be difficult to extract due to noise and foreground emission, efforts have focused on a statistical detection of the 21-cm fluctuations. During cosmic reionization, these fluctuations are highly non-Gaussian and thus more information can be extracted than just the one-dimensional function that is usually considered, i.e. the correlation function. We calculate a two-dimensional function that if measured observationally would allow a more thorough investigation of the properties of the underlying ionizing sources. This function is the probability distribution function (PDF) of the difference in the 21-cm brightness temperature between two points, as a function of the separation between the points. While the standard correlation function is determined by a complicated mixture of contributions from density and ionization fluctuations, we show that the difference PDF holds the key to separately measuring the statistical properties of the ionized regions.     

Groundwater flow dynamics in the complex aquifer system of Gidabo River Basin (Ethiopian Rift): a multi-proxy approach

Hydrochemical and isotope data in conjunction with hydraulic head and spring discharge observations were used to characterize the regional groundwater flow dynamics and the role of the tectonic setting in the Gidabo River Basin, Ethiopian Rift. Both groundwater levels and hydrochemical and isotopic data indicate groundwater flow from the major recharge area in the highland and escarpment into deep rift floor aquifers, suggesting a deep regional flow system can be distinguished from the shallow local aquifers. The δ¹⁸O and δ²H values of deep thermal (≥30 °C) groundwater are depleted relative to the shallow (<60 m below ground level) groundwater in the rift floor. Based on the δ¹⁸O values, the thermal groundwater is found to be recharged in the highland around 2,600 m a.s.l. and on average mixed with a proportion of 30 % shallow groundwater. While most groundwater samples display diluted solutions, δ¹³C data of dissolved inorganic carbon reveal that locally the thermal groundwater near fault zones is loaded with mantle CO₂, which enhances silicate weathering and leads to anomalously high total dissolved solids (2,000–2,320 mg/l) and fluoride concentrations (6–15 mg/l) exceeding the recommended guideline value. The faults are generally found to act as complex conduit leaky barrier systems favoring vertical mixing processes. Normal faults dipping to the west appear to facilitate movement of groundwater into deeper aquifers and towards the rift floor, whereas those dipping to the east tend to act as leaky barriers perpendicular to the fault but enable preferential flow parallel to the fault plane.     

Seismic refraction profiles between Cyprus and Israel and their interpretation

Summary. A long seismic refraction profile was carried out between southern Israel and Cyprus. The seismic energy was generated by 33 sea shots each of 0.8 t explosives and was recorded by land stations in Israel and Cyprus and by ocean bottom seismographs deployed along the profile.
The results showed that the continental crust of southern Israel thins towards the Mediterranean underneath a northward thickening sedimentary cover. Cyprus is underlain by a 35 km thick continental crust thinning south-wards and extending to Mt Eratosthenes. Between Mt Eratosthenes and the Israel continental shelf the crystalline crust is composed of high velocity (6.5 km s^-1)material and is about 8 km thick. It is covered by 12–14 km of sediments and may represent a fossil oceanic crust.     

Natural boron-free kornerupine and its breakdown products in a sapphirine rock of the Limpopo Belt,Southern Africa

Large crystals of boron-free kornerupine occurring in MgAl-rich inclusions within meta-anorthosites are partially replaced by symplectitic pseudomorphs consisting essentially of the assemblage sapphirine-cordieritegedrite. The highly magnesian, hydrous kornerupines (F= 0.10–0.14) have compositions close to the oxide ratio (Mg, Fe) O· Al₂O₃· SiO₂. Sapphirines (F=0.09) show decreasing Al-contents with continued grain growth and equilibration. Gedrite (F=0.15) contains sodium in amounts near the limit of solid solution, although the kornerupine starting material is free of this element and it is very rare in the enclosing rock. Cordierite (F=0.05) is also free from sodium.For conditions of P _H2O = P _tot the appearance of boron-free kornerupine requires relatively high temperatures (> 700 °C) and a minimum pressure near 4 kb within this zone of the Limpopo Belt. The subsequent replacement reaction occurred nearly isochemically except for Na and probably H₂O, which were introduced into the symplectite. Textural features suggest that the breakdown reaction of kornerupine is actually governed by the magnitude of sodium activity: Relatively low values would favor the appearance of boron-free kornerupine, whereas higher values lead to the more common assemblage sapphirine-cordierite-gedrite.     

Eifelite,KNa3Mg4Si12O30, a new mineral of the osumilite group with octahedral sodium

Eifelite of variable composition is uniaxial positive withn ₀ near 1.543 andn _e near 1.544, a between 10.14 and 10.15 Å, andc about 14.22 Å, space groupP 6/m 2/c 2/c. There is a complete series of solid solution between the eifelite end member KNa₃Mg₄Si₁₂O₃₀ and roedderite, KNaMg₅Si₁₂O₃₀, following the 2 Na?Mg substitution. Both eifelite and roedderite have milarite-type structures, but Na is always in six-coordinated sites: In roedderite Na occupies solely a newly defined B′^[6]-position which is slightly displaced alongc from the ideal B_[9]-position lying on the (001/2)-mirror plane in K₂Mg₅Si₁₂O₃₀. In eifelite Na is located both inB′^[6] and in theA _[6]-positions, where it partially replaces Mg. Eifelite has the highest cation occupancy of all osumilite group minerals known thus far. Both eifelite and roedderite occur in vesicles of contact metamorphosed basement xenoliths ejected with the leucite tephrite lava of the Quaternary Bellerberg volcano in the Eifel, West Germany. They are considered to be precipitates from highly alkaline, MgSi-rich, but Al-deficient gas phases that originated through interaction of gaseous igneous differentiates with the xenoliths.     

Minerals of the viridine hornfels from Darmstadt,Germany

Viridine containing the highest amounts of Mn₂O₃ detected thus far (up to 20.5 mol % “Mn₂SiO₅”) coexists in a metasedimentary hornfels with spessartine, Mn-phlogopite (mangan-ophyllite), Mn-phengite (alurgite), hematite, quartz and probably some primary braunite. In layers poorer in viridine spessartine is absent but piemontite appears as an additional phase. Microprobe analyses of all these phases are presented which indicate very strong fractionation of Mg and Mn in coexisting phlogopite and garnet, and of Fe and Mn in coexisting hematite and braunite. Sericitic aggregates consisting of phengitic muscovite and braunite are interpreted as retrograde alteration products of viridine, but might partly be pinitic alterations of a former Mg-rich cordierite. Due to the occurrence of the assemblage spessartine-viridine-quartz Mn-cordierite cannot have been a stable phase prior to retrograde alterations. In general the stability field of viridine is extended towards higher temperatures as compared to that of pure andalusite, Al₂SiO₅. Due to the coexistence of phlogopite and muscovite (phengite) the temperature of contact metamorphism cannot have exceeded some 550°–650° C depending on the prevailing water pressure.     

Lithium in NaBe-cordierites from El Peñón,Sierra de Córdoba,Argentina

NaBe-cordierites (Fe/(Fe+Mn+Mg)=0.49–0.57) with BeO contents up to 1.16 weight % and additional Li₂O contents up to 0.21 wt.% occur in cordierite-apatite-uraninite-muscovite-biotite-chlorite-feldspar-quartz nodules within pegmatites penetrating gneissic roof pendants of a lower Palaeozoic granite batholith. Occasional small crystals of beryl are interpreted to coexist stably with unaltered cordierite. Be and Li are incorporated in cordieriteaccording to the substitutions Na^[Channel] + Be^[4] Al^[4] and Na^[Ch]+Li_[6]R^2+[6], respectively. The coexisting phyllosilicates do apparently not contain appreciable amounts of Li. According to powder IR-data, the analyzed water contents of the cordierites are dominantly of type II, and there is also little CO₂. Their distortion indices are rather low (0.121–0.145) and so are their optic angles (2V=50-51_°). Considering all eleven NaBeLi-cordierites known thus far there is a strong positive correlation between Na and (Be+Li) with a slope close to 1.0. However, there is virtually no correlation between Be and Li, their incorporation into cordierite depending on the local geochemical environment. A strong negative correlation exists between the distortion indices of the NaBeLi-cordierites and their Be contents. Li has a disturbing influence on this relationship, and the versus Na correlation is also statistically worse than versus Be.Deceased December 20, 1984     

High-magnesium staurolite in a sapphirine-garnet rock from the Limpopo Belt,Southern Africa

Unusually Mg-rich staurolite with F=Fe/(Fe+ Mg) = 0.51 occurs in a peraluminous silica-deficient sapphirine-garnet-gedrite-spinel-corundum-phlogopite rock as relic inclusions within pyrope-almandine garnet (F=0.43–0.48), from which it is generally separated by sapphirine (F=0.19). Gedrite has F=0.24–0.27, phlogopite 0.19, and spinel 0.43. The gradual disappearance of staurolite is due to a shift of the 3-phase AFM assemblage staurolite-garnetsapphirine to more Fe-rich compositions according to probably prograde reactions between staurolite and garnet to form sapphirine together with either quartz or gedrite. Thus still more Mg-rich staurolite seems to have existed in the rock at earlier stages of metamorphism characterized by lower temperatures and perhaps higher pressures. The local equilibria now frozen in indicate minimum pressures of 7–8 kbar and temperatures in excess of about 800° C.Staurolite is free from Zn, very low in Si, and richer in Ti than any other staurolite found thus far. Most notable is the unique Mg/Fe fraction between staurolite and garnet with staurolite being the more Fe-rich phase (K_D=1.32).