Recovering physical parameters from galaxy spectra using MOPED

We derive physical parameters of galaxies from their observed spectra using MOPED, the optimized data compression algorithm of Heavens, Jimenez & Lahav. Here we concentrate on parametrizing galaxy properties, and apply the method to the NGC galaxies in Kennicutt's spectral atlas. We focus on deriving the star formation history, metallicity and dust content of galaxies. The method is very fast, taking a few seconds of CPU time to estimate ∼17 parameters, and is therefore specially suited to studying large data sets, such as the Anglo-Australian two-degree-field (2dF) galaxy survey and the Sloan Digital Sky Survey (SDSS). Without the power of MOPED, the recovery of star formation histories in these surveys would be impractical. In Kennicutt's atlas, we find that for the spheroidals a small recent burst of star formation is required to provide the best fit to the spectrum. There is clearly a need for theoretical stellar atmospheric models with spectral resolution better than 1 Å if we are to extract all the rich information that large redshift surveys contain in their galaxy spectra.     

PHOSPHATE-SULFIDE ASSEMBLAGES AND Al/Ca RATIOS IN TYPE-3 CHONDRITES

Phosphate-sulfide assemblages are common constituents in type-3 carbonaceous and ordinary chondrites. CV3 chondrites contain assemblages of pentlandite-merrillite and troilite-merrillite as well as isolated grains of Ca-pyroxene; CO3 chondrites contain troilite-merrillite (± schreibersite) as well as isolated grains of plagioclase; and, H-L-LL3 chondrites contain troilite-merrillite (± metal), troilite-chlorapatite, and metal-chlorapatite. The phosphate-bearing assemblages probably formed in the following manner: (1) metal grains with significant P formed in the nebula at high temperatures; (2) Schreibersite exsolved and crystallized at metal grain boundaries during cooling; (3) some metal grains were sulfurized at lower temperatures by H₂S; (4) the metal-schreibersite and sulfide-schreibersite assemblages accreted rims of finegrained silicates; and, (5) the Schreibersite reacted with Ca, O and Cl from these silicates to form merrillite and chlorapatite. The reported bulk compositions of chondritic constituents have ***CI-normalized Al/Ca ratios >1, whereas whole-rock ratios are unfractionated. Even though the phosphate-bearing assemblages and isolated grains of Ca-bearing silicates are ubiquitous in type-3 chondrites, they are insufficiently abundant to lower the Al/Ca ratios of the major chondritic components to those of the whole-rocks. It seems probable that some of the analytical data are incorrect; bulk compositions determined by microprobe may yield erroneously high Al/Ca ratios if samples are analyzed with a broader electron beam than used for analyzing the standards. We recommend analyzing standards and samples with the same size beam.     

Ground temperature histories in eastern and central Canada from geothermal measurements: evidence of climatic change

Inverse and direct methods have been used to analyze a large number of borehole temperature logs in order to infer past climatic changes. Results indicate a warming of 1–2°C in eastern and central Canada during the past 150 years. A period of cooling between 500 and 200 years before present, corresponding to the time of the “Little Ice Age”, has also been identified in the same areas. A regional ground temperature history is estimated for eastern and central Canada from the simultaneous inversion of several temperature logs. The inferred temperature changes appear correlated with the concentration of atmospheric carbon dioxide as reported from a Greenland ice core, and agree with existing meteorological and dendrochronological records for the area.     

Order-of-scattering and doubling method for the solution of transfer equations

A method to obtain scattering and transmission functions for computational purposes has been developed in this paper. This method can be easily extended to the scattering atmosphere involving internal energy and may be to the time-dependent case. Special cases such as the homogeneous process, the Helmholtz's principle of reciprocity and the self-adjoint are presented.     

Canonical forms for symplectic and Hamiltonian matrices

This paper gives a constructive method for finding canonical forms for symplectic and Hamiltonian matrices. No restrictions are made on the eigen values or their multiplicity. Real canonical forms are treated in detail.     

The Hadley Rille enstatite chondrite and its agglutinate-like rim: Impact melting during accretion to the Moon

Abstract— Hadley Rille is a millimeter-size EH chondrite containing euhedral and acicular enstatite grains, kamacite globules and preferentially aligned silicate aggregates separated by elongated kamacite-rich patches. The Hadley Rille chondrite was significantly impact melted when it accreted to the lunar regolith at relative velocities of ～>3 km s^?1; ～65–75% of the chondrules present initially were melted. During the impact, portions of the local regolith were melted and an agglutinate-like rim formed around the chondritic projectile; the rim consists of flow-banded vesicular glass, blebs of troilite and low-Ni metallic Fe, rock fragments, glass(?) shards, and mineral grains. The mineral grains include enstatite (which is otherwise absent from the Moon and must have been derived from the projectile) and poorly characterized, micrometer-size phases enriched in light rare-earth-elements (LREE), which probably formed during the impact. Several of the rock fragments contain <33 mg/g Cl, which was probably derived through impact-induced volatilization of Cl from chondrule mesostases in the EH projectile.     

Interaction between aggrading geomorphic surfaces and the formation of a late pleistocene paleosol in the palouse loess of eastern Washington state

Variable rates of loess deposition contributed to dramatic regional variation in a soil-stratigraphic unit, the Washtucna Soil, in the Palouse loess deposits in the Channeled Scabland of eastern Washington state. Throughout most of the Channeled Scabland, the morphology of the Washtucna Soil is that of a single buried soil, but it bifurcates into two well-developed and pedologically distinct buried soils in areas immediately downwind of the major source of loessial sediment. Regional loess stratigraphy confirms that the two well-developed soils formed during the same interval of time during which only one soil formed in areas that are distal to loess source areas. The variable and perhaps rapid rates of soil formation suggested by the stratigraphy resulted from an interaction between variable rates of loess deposition and the formation of superimposed calcic soils. Petrocalcic horizons with weak Stage IV morphology formed as the zone of carbonate accumulation moved up into former A and cambic horizons that had been profusely burrowed by cicadas. The development of cicada burrows in one phase of soil development that were subsequently engulfed by pedogenic carbonate under a rising land surface seems to have greatly accelerated the development of the petrocalcic horizons. Accelerated rates of formation of the petrocalcic horizons occurred when extrinsic (pulses of loess deposition) and intrinsic (engulfment of burrowed horizons) thresholds were exceeded. Stratigraphic evidence suggests that the soil formation that accompanied the rise in the land surface due to additional loess deposition may have occurred during the late Wisconsin glaciation when giant glacial outburst floods in the channeled Scabland triggered a new cycle of loess deposition.