An analytic investigation of the scatter in the integrated X-ray properties of galaxy groups and clusters     

Michael L. Balogh  Arif Babul  G. Mark Voit  Ian G. McCarthy  Laurence R. Jones  Geraint F. Lewis  Harald Ebeling 《Monthly notices of the Royal Astronomical Society》2006,366(2):624-634

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Possible evidence for on-going volcanism on Mars as suggested by thin, elliptical sheets of low-albedo particulate material around pits and fissures close to Cerberus Fossae     

Gerald Patrick Roberts  Ian A. Crawford  David Peacock  Joyce Vetterlein  Elisabeth Parfitt  Louise Bishop 《Earth, Moon, and Planets》2007,100(1-2):1-16

High quality CCD images obtained at two different observatories in North Italy allowed the identification of four morphological structures near the nuclear region of the comet Ikeya-Zhang (I-Z): haloes, jets, shells and spirals. The interpretation of the nature of these structures has been attempted by means of a comparison of different up-to-date image processing techniques, which led to a single common estimate of the rotation period (p=1.48±0.20 days).  相似文献   

Remelting of refractory inclusions in the chondrule‐forming regions: Evidence from chondrule‐bearing type C calcium‐aluminum‐rich inclusions from Allende     

Alexander N. Krot  Hisayoshi Yurimoto  Ian D. Hutcheon  Marc Chaussidon  Glenn J. MacPherson  Julie Paque 《Meteoritics & planetary science》2007,42(7-8):1197-1219

Abstract— We describe the mineralogy, petrology, oxygen, and magnesium isotope compositions of three coarse‐grained, igneous, anorthite‐rich (type C) Ca‐Al‐rich inclusions (CAIs) (ABC, TS26, and 93) that are associated with ferromagnesian chondrule‐like silicate materials from the CV carbonaceous chondrite Allende. The CAIs consist of lath‐shaped anorthite (An₉₉), Cr‐bearing Al‐Ti‐diopside (Al and Ti contents are highly variable), spinel, and highly åkermanitic and Na‐rich melilite (Åk_63–74, 0.4–0.6 wt% Na₂O). TS26 and 93 lack Wark‐Lovering rim layers; ABC is a CAI fragment missing the outermost part. The peripheral portions of TS26 and ABC are enriched in SiO₂ and depleted in TiO₂ and Al₂O₃ compared to their cores and contain relict ferromagnesian chondrule fragments composed of forsteritic olivine (Fa_6–8) and low‐Ca pyroxene/pigeonite (Fs₁Wo_1–9). The relict grains are corroded by Al‐Ti‐diopside of the host CAIs and surrounded by haloes of augite (Fs_0.5Wo_30–42). The outer portion of CAI 93 enriched in spinel is overgrown by coarse‐grained pigeonite (Fs_0.5–2Wo_5–17), augite (Fs_0.5Wo_38–42), and anorthitic plagioclase (An₈₄). Relict olivine and low‐Ca pyroxene/pigeonite in ABC and TS26, and the pigeonite‐augite rim around 93 are ¹⁶O‐poor (Δ17O ～ ?1‰ to ?8‰). Spinel and Al‐Ti‐diopside in cores of CAIs ABC, TS26, and 93 are ¹⁶O‐enriched (Δ17O down to ?20‰), whereas Al‐Ti‐diopside in the outer zones, as well as melilite and anorthite, are ¹⁶O‐depleted to various degrees (Δ17O = ?11‰ to 2‰). In contrast to typical Allende CAIs that have the canonical initial ²⁶Al/²⁷Al ratio of ～5 × 10^?5 ABC, 93, and TS26 are ²⁶Al‐poor with (²⁶Al/²⁷Al)₀ ratios of (4.7 ± 1.4) × 10^?6 (1.5 ± 1.8) × 10^?6 <1.2 × 10^?6 respectively. We conclude that ABC, TS26, and 93 experienced remelting with addition of ferromagnesian chondrule silicates and incomplete oxygen isotopic exchange in an ¹⁶O‐poor gaseous reservoir, probably in the chondrule‐forming region. This melting episode could have reset the ²⁶Al‐²⁶Mg systematics of the host CAIs, suggesting it occurred ～2 Myr after formation of most CAIs. These observations and the common presence of relict CAIs inside chondrules suggest that CAIs predated formation of chondrules.  相似文献   

The hierarchical formation of a stellar cluster   总被引：1，自引：0，他引：1  

Ian A. Bonnell  Matthew R. Bate  Stephen G. Vine 《Monthly notices of the Royal Astronomical Society》2003,343(2):413-418

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Clump lifetimes and the initial mass function     

Paul C. Clark  Ralf S. Klessen  Ian A. Bonnell 《Monthly notices of the Royal Astronomical Society》2007,379(1):57-62

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Chemical and isotopic constraints on the formation and crystallization of SA-1, a basaltic Allende plagioclase-olivine inclusion     

Allen K. Kennedy  Ian D. Hutcheon 《Meteoritics & planetary science》1992,27(5):539-554

Abstract— SA-1, an unusual basaltic plagioclase-olivine inclusion (POI) in Allende, has concentric textural and mineralogic zones, a fine-grained, 100μm outer border and a coarse-grained interior with subophitic texture. Fassaite, diopside and olivine from the exterior border and interior of SA-1 have uniform intrinsic mass fractionation with isotopically heavy Mg (F_Mg = 3.6 ± 1.8‰/amu). In contrast, spinels from the spinel-rich regions adjacent to the fine-grained border have normal Mg isotopic composition (F_Mg = 0.1 ± 1.5‰/amu). The cores of large calcic (An_90,99) plagioclase have no excess ²⁶Mg, corresponding to ²⁶Mg*/ ²⁷Al < 3.7 × 10^?6. The Mg isotopic heterogeneity in SA-1 requires initial cooling rates of spinel-rich regions adjacent to the fine-grained border to be greater than ～75 °C/hr. In contrast, the subophitic texture of the interior suggests cooling rates of 5–20 °C/ hr. The minerals in SA-1 exhibit a wide range of REE abundances. Lanthanum concentrations vary from 1 × chondritic (ch) in early crystallizing diopside to 100 × ch in late crystallizing fassaite. Nepheline has 18–20 × ch LREE and 11–25 × ch HREE and iron-rich mesostasis is highly enriched in the REE with 270–400 × ch LREE and 230–280 × ch HREE. The complementary REE patterns of clinopyroxene and plagioclase and the enrichment of incompatible trace elements in the mesostasis and late crystallizing phases is consistent with closed system crystallization. The REE data for nepheline and the iron-rich mesostasis indicate these phases are in equilibrium and that nepheline crystallized from a melt. Influx of alkalies, minor Fe and halogens must have occurred during the last stages of crystallization or the inclusion must have been partially molten during Na influx as both anorthite (An₉₉) and nepheline are present in this inclusion. The preservation of isotopic heterogeneity in an inclusion that crystallized from a melt implies that melting was incomplete, allowing for survival of the relict spinels. The major and trace element abundances in SA-1 are inconsistent with formation as a mixture of nebular materials and suggest that SA-1 contains a chemically fractionated component produced by igneous differentiation.  相似文献   

The Sunyaev–Zeldovich background     

Gilbert P. Holder †  Ian G. McCarthy  A. Babul 《Monthly notices of the Royal Astronomical Society》2007,382(4):1697-1706

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The 2dF Galaxy Redshift Survey: galaxy clustering per spectral type     

Darren S. Madgwick  Ed Hawkins  Ofer Lahav  Steve Maddox  Peder Norberg  John A. Peacock  Ivan K. Baldry  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Carole Jackson  Ian Lewis  Stuart Lumsden  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2003,344(3):847-856

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X-ray astronomy in the new millennium     

Ian Carstairs 《Astronomy& Geophysics》2002,43(2):2.27-2.28

A two-day discussion meeting on the latest developments in X-ray astronomy was held on 19 and 20 February 2002 at the Royal Society, organized by Roger Blandford, Andy Fabian and Ken Pounds. Ian Carstairs reports.  相似文献   

The 2dF Galaxy Redshift Survey: the population of nearby radio galaxies at the 1-mJy level     

Manuela Magliocchetti  Steve J. Maddox  Carole A. Jackson  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto de Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Ofer Lahav  Ian Lewis  Stuart Lumsden  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,333(1):100-120

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