Structural parameters for globular clusters in NGC 5128 – III. ACS surface brightness profiles and model fits     

Dean E. McLaughlin  Pauline Barmby  William E. Harris  Duncan A. Forbes  Gretchen L. H. Harris 《Monthly notices of the Royal Astronomical Society》2008,384(2):563-590

We present internal surface brightness profiles, based on Hubble Space Telescope /ACS imaging in the F 606 W bandpass, for 131 globular cluster (GC) candidates with luminosities   L ≃ 10⁴–3 × 10⁶ L_⊙  in the giant elliptical galaxy NGC 5128. Several structural models are fitted to the profile of each cluster and combined with mass-to-light ratios ( M / L values) from population-synthesis models, to derive a catalogue of fundamental structural and dynamical parameters parallel in form to the catalogues recently produced by McLaughlin & van der Marel and by Barmby et al. for GCs and massive young star clusters in Local Group galaxies. As part of this, we provide corrected and extended parameter estimates for another 18 clusters in NGC 5128, which we observed previously. We show that, like GCs in the Milky Way and some of its satellites, the majority of globulars in NGC 5128 are well fitted by isotropic Wilson models, which have intrinsically more distended envelope structures than the standard King lowered isothermal spheres. We use our models to predict internal velocity dispersions for every cluster in our sample. These predictions agree well in general with the observed dispersions in a small number of clusters for which spectroscopic data are available. In a subsequent paper, we use these results to investigate scaling relations for GCs in NGC 5128.  相似文献   

Misdirected QSOs in the most luminous infrared galaxies     

Dean C. Hines 《Astrophysics and Space Science》1999,266(1-2):273-278

I discuss imaging and spectropolarimetry results which show that buried QSOs (monsters) are sufficient to power hyperluminous infrared galaxies.  相似文献   

Extragalactic integral field spectroscopy on the Gemini telescopes     

A. Bunker  J. Smith  I. Parry  R. Sharp  A. Dean  G. Gilmore  R. Bower  M. Swinbank  R. Davies  R. B. Metcalf  R. de Grijs 《Astronomische Nachrichten》2004,325(2):139-142

We have been undertaking a programme on the Gemini 8‐m telescopes to demonstrate the power of integral field spectroscopy, using the optical GMOS spectrograph, and the new CIRPASS instrument in the near‐infrared. Here we present some preliminary results from 3D spectroscopy of extra‐galactic objects, mapping the emission lines in a 3CR radio galaxy and in a gravitationally lensed arc, exploring dark matter sub‐structure through observations of an Einstein Cross gravitational lens, and the star formation time‐scales of young massive clusters in the starburst galaxy NGC 1140. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Sorby on sedimentology: A collection of papers from 1851 to 1908 by Henry Clifton Sorby. Geological milestones, 1: C.H. Summerson (editor). University of Miami,Miami, Fla., 1976, 225 pp., U.S. $7.50     

Dean A. McManus 《Marine Geology》1976,22(3):207-208

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Particle motions in coronal streamers and type III radio bursts     

Dean F. Smith  G. W. Pneuman 《Solar physics》1972,25(2):461-477

Both individual and collective motions of electron and proton streams in the current sheet which is thought to exist near the center of a coronal streamer are considered. Unlike previous analyses, closed field lines which must exist when finite conductivity is taken into account as well as a B _ø field due to solar rotation are present. It is shown on the basis of individual particle motions that neither electrons nor protons could move in most of the sheet in the manner required to explain type III bursts since they are effectively tied to the closed field lines.The possibility that the stream could collectively drag the closed field lines out with itself is considered. It is shown that impossibly high densities are required for electron streams and improbable densities for proton streams. Thus the particles responsible for type III bursts cannot travel in the densest part of a coronal streamer, but presumably travel close to this region. Moreover, the current sheet cannot act as a channeling agent to help explain the transverse coherency of type III burst sources.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

WETLAND LOSS IN COASTAL LOUISIANA     

Menglou WANG  Donald Dean ADRIAN 《国际泥沙研究》1998,(1)

ＷＥＴＬＡＮＤＬＯＳＳＩＮＣＯＡＳＴＡＬＬＯＵＩＳＩＡＮＡＭｅｎｇｌｏｕＷＡＮＧ１ａｎｄＤｏｎａｌｄＤｅａｎＡＤＲＩＡＮ２ＡＢＳＴＲＡＣＴＷｅｔｌａｎｄｓｉｎｔｈｅＭｉｓｉｓｓｉｐｐｉＲｉｖｅｒｄｅｌｔａｉｃｐｌａｉｎａｒｅｖａｌｕａｂｌｅｒｅｓｏｕ...  相似文献   

利用岩石地球化学特征判断西秦岭寒武系含矿硅岩建造的沉积环境   总被引：10，自引：0，他引：10  

刘家军  刘建明 《沉积学报》1998,16(4):42-49

西秦岭寒武系硅岩建造是拉尔玛、邛莫金矿床和牙相金矿点的赋矿岩系。其主要由炭质硅岩和炭质板岩组成。其中的含矿硅岩构造十分丰富,有块状、条带状、层纹状、多孔状和同生角砾状等。硅岩单层厚度一般为30～200 m。其主要成分除SiO₂( 平均含量 95. 30%) 外,其它氧化物含量能达1% 者仅有 FeO 、Fe₂O₃和 P₂O₅,且 FeO/Fe₂O₃比值大于 1, 而 Sr/Ba 比值小于 1 。硅岩建造中有机炭含量相当高,一般为(0.12～8.14) %,高者达 22 %。硅岩中稀土以总量低(3.29×10-6～100×10-6)、铈亏损为特征。硅岩建造中沉积黄铁矿的δ34S值变化在-10‰～ +46.9‰之 间。 硅岩的δ300Si值主要变化在+0.4 ‰～+0.8‰之间。硅岩建造的上述特点反映其主要是在深海-半深海环境下形成的。  相似文献   

Liquidus phase relationships on the join anorthiteforsterite-quartz at 20 kbar with applications to basalt petrogenesis and igneous sapphirine     

Teh-Ching Liu  Dean C. Presnall 《Contributions to Mineralogy and Petrology》1990,104(6):735-742

Liquidus phase relationships determined on the join anorthite-forsterite-quartz at 20 kbar show primary phase fields for quartz (q), forsterite (fo), enstatite (en), spinel (sp), anorthite (an), sapphirine (sa), and corundum (cor). Increasing pressure causes (1) thefo andan primary phase fields to contract, (2) theen, q, andcor fields to expand, (3) thefo-en boundary line to move away from the Q apex, (4) theen-q boundary line to move also away from the Q apex but by a smaller amount, and (5) a primary phase field forsa to appear at a pressure between 10 and 20 kbar. Seven liquidus piercing points at 20 kbar have been located as follows:

Crystalline phases  相似文献    139. Neutralization and stabilization of particle streams in the corona and type III radio bursts      Dean F. Smith 《Solar physics》1972,23(1):191-203 The processes by which streams of charged particles become charge and current neutralized in the corona are investigated. It is shown that a large amplitude plasma wave, which is related to precursor phenomenon in type III bursts and possibly plasma radiation from type IV bursts, will be excited at the head of the stream. The energy extracted from the stream to produce this plasma wave is computed and used to set conservative upper limits on the densities of possible excitors for type III bursts. For electron streams the density n s < 10–5 n e, where n e is the density of the background plasma. For proton streams n s < 1.8 × 10–2 n e. The energy extracted from the stream is also used to set upper limits on the lifetimes of relativistic electrons stored in the corona and it is concluded that for n e > 102 cm–3 this loss must be taken into account. Since electron streams cannot produce their own stabilizing ionacoustic waves because they would violate the condition n s < 10–5 n e, other mechanisms for producing ion-acoustic waves in the corona are examined. Another stabilization mechanism due to velocity inhomogeneity is investigated.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献    140. BEYOND THE GEOGRAPHY OF DEVELOPMENT      Dean Forbes  M.A.  Ph.D. 《Singapore journal of tropical geography》1981,2(2):68-80   相似文献    [首页] « 上一页 [9] [10] [11] [12] [13] 14 [15] [16] [17] [18] [19] 下一页 » 末  页»