The field of IC 2602: Strömgren‐Hβ photometry approach

A homogeneous data‐base collating all uvbyβ photometry available at present for O‐B9 stars in the field of IC 2602 is presented. The characteristics of the field are studied. Four spatially coherent groups can be distinguished. A low reddened compact group located at 156 ± 6 pc is identi.ed with IC 2602, followed by background layers at 546 ± 33 pc, 1117 ± 61 pc, and possibly at 2626 ± 163 pc. The apparent depth of the first three layers is about 1 kpc, which is consistent with the thickness of a spiral arm. There is an indication for the existence of a region free of massive luminous stars between 1.2 and 2.6 kpc, which could be associated with interarm space between the Local Association and the distant spiral structures toward Carina. A comparison between the photometric and Hipparcos parallaxes is presented. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Eigenschaften singularitätenfreier,statischer, zentralsymmetrischer Lösungen gewisser Gravitationsfeldgleichungen 4. Ordnung

FIEDLER and SCHIMMING (1983) proved that the fourth order gravitational field equations with a linear combination of Bach's and Einstein's tensors on the left-hand side, which were proposed by TREDER , admit static centrally symmetric solutions which are analytical and non-flat in some neighbourhood of the centre of symmetry. The existence of these solutions, known at first only in a small neighbourhood of r = o (r radius), can now be extended to intervals o ≦ r ≦ α with arbitrarily large α , using the abstract theorem on inverse functions. Further it is proved that the Schwarzschild metrics are in a certain sense the only solutions of the above equations that are analytic, asymptotically flat, static and centrally symmetric around r = +∞.     

The Ardón L6 ordinary chondrite: A long‐hidden Spanish meteorite fall

We report and describe an L6 ordinary chondrite fall that occurred in Ardón, León province, Spain (longitude 5.5605°W, latitude 42.4364°N) on July 9th, 1931. The 5.5 g single stone was kept hidden for 83 yr by Rosa González Pérez, at the time an 11 yr old who had observed the fall and had recovered the meteorite. According to various newspaper reports, the event was widely observed in Northern Spain. Ardón is a very well‐preserved, fresh, strongly metamorphosed (petrologic type 6), and weakly shocked (S3) ordinary chondrite with well‐equilibrated and recrystallized minerals. The mineral compositions (olivine Fa_23.7±0.3, low‐Ca pyroxene Fs_20.4±0.2Wo_1.5±0.2, plagioclase An_10.3±0.5Ab_84.3±1.2), magnetic susceptibility (log χ = 4.95 ± 0.05 × 10^?9 m³ kg^?1), bulk density (3.49 ± 0.05 g   cm^?3), grain density (3.58 ± 0.05 g   cm^?3), and porosity (2.5 vol%) are typical for L6 chondrites. Short‐lived radionuclides confirm that the meteorite constitutes a recent fall. The ²¹Ne and ³⁸Ar cosmic ray exposure ages are both about 20–30 Ma, similar to values for many other L chondrites. The cosmogenic ²²Ne/²¹Ne ratio indicates that preatmospheric Ardón was a relatively large body. The fact that the meteorite was hidden in private hands for 83 yr makes one wonder if other meteorite falls may have experienced the same fate, thus possibly explaining the anomalously low number of falls reported in continental Spain in the 20th century.     

Merging History of Massive Galaxies at 3 < z < 6

The observational data of high redshift galaxies become increasingly abundant, especially since the operation of the James Webb Space Telescope, which allows us to verify and optimize the galaxy formation model at high redshifts. In this work, we investigate the merging history of massive galaxies at 3 < z < 6 using a well-developed semi-analytic galaxy formation catalog. We find that the major merger rate increases with redshift up to 3 and then flattens. The fraction of wet mergers, duri...