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71.
72.
C.S. Botzler J. Snigula R. Bender N. Drory G. Feulner G.J. Hill U. Hopp C. Maraston C. Mendes de Oliveira 《Astrophysics and Space Science》2003,284(2):393-396
The Munich Near-IR Cluster Survey (MUNICS) is a wide-area, medium-deep, photometric survey selected in the K' band. The project's
main scientific aims are the identification of galaxy clusters up to redshifts of unity and the selection of a large sample
of field early-type galaxies up to z < 1.5 for evolutionary studies. We created a Large Scale Structure catalog, using a new structure finding technique specialized
for photometric datasets, that we developed on the basis of a friends-of-friends algorithm. We tested the plausibility of
the resulting galaxy group and cluster catalog with the help of Color-Magnitude Diagrams (CMD), as well as a likelihood- and
Voronoi-approach.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
73.
74.
We explore the possibility of searching for groups of radio sources from the FIRST catalog on angular scales 1′–5′. We developed an efficient method of searching for such groups that takes into account the need for combining the components of extended sources represented in the catalog by separate objects. We found 31 groups of radio sources with angular sizes <5′ that contain no fewer than five sources with flux densities ≥3 mJy. This number is at least triple the expected number of such groups for a random Poisson distribution of radio sources in the sky. The prospects for using groups of radio sources to detect and study distant systems of galaxies are discussed. 相似文献
75.
The remnant resulting from the merger of two neutron stars produces neutrinos in copious amounts. In this paper we present the neutrino emission results obtained via Newtonian, high-resolution simulations of the coalescence event. These simulations use three-dimensional smoothed particle hydrodynamics together with a nuclear, temperature-dependent equation of state and a multiflavour neutrino leakage scheme. We present the details of our scheme, discuss the neutrino emission results from a neutron star coalescence and compare them with the core-collapse supernova case where neutrino emission has been studied for several decades. The average neutrino energies are similar to those in the supernova case, but contrary to the latter, the luminosities are dominated by electron-type antineutrinos that are produced in the hot, neutron-rich, thick disc of the merger remnant. The cooler parts of this disc contain substantial fractions of heavy nuclei, which, however, do not influence the overall neutrino emission results significantly. Our total neutrino luminosities from the merger event are considerably lower than those found in previous investigations. This imposes constraints on the ability of neutron star mergers to produce a gamma-ray burst via neutrino annihilation. The neutrinos are emitted preferentially along the initial binary rotation axis, an event seen 'pole-on' would appear much brighter in neutrinos than a similar event seen 'edge-on'. 相似文献
76.
Harold C. CONNOLLY D. S. BURNETT Kevin D. McKEEGAN 《Meteoritics & planetary science》2003,38(2):197-224
Abstract— Minor element variations in MgAl2O4 spinel from the type B1 calcium‐aluminum‐rich inclusion (CAI) Allende TS‐34 confirm earlier studies in showing correlations between the minor element chemistry of spinels with their location within the inclusion and with the chemistry of host silicate phases. These correlations result from a combination of crystallization of a liquid produced by re‐melting event(s) and local re‐equilibration during subsolidus reheating. The correlation of the Ti and V in spinel inclusions with the Ti and V in the adjacent host clinopyroxene can be qualitatively explained by spinel and clinopyroxene crystallization prior to melilite, following a partial melting event. There are, however, difficulties in quantitative modeling of the observed trends, and it is easier to explain the Ti correlation in terms of complete re‐equilibration. The correlation of V in spinel inclusions with that in the adjacent host clinopyroxene also cannot be quantitatively modeled by fractional crystallization of the liquid produced by re‐melting, but it can be explained by partial re‐equilibration. The distinct V and Ti concentrations in spinel inclusions in melilite from the edge regions of the CAI are best explained as being affected by only a minor degree of re‐equilibration. The center melilites and included spinels formed during crystallization of the liquid produced by re‐melting, while the edge melilites and included spinels are primary. The oxygen isotope compositions of TS‐34 spinels are uniformly 16O‐rich, regardless of the host silicate phase or its location within the inclusion. Similar to other type B1 CAIs, clinopyroxene is 16O‐rich, but melilite is relatively 16O‐poor. These data require that the oxygen isotope exchange in TS‐34 melilite occurred subsequent to the last re‐melting event. 相似文献
77.
M.P. Collings J.W. Dever H.J. Fraser M.R.S. McCoustra 《Astrophysics and Space Science》2003,285(3-4):633-659
The interaction of carbon monoxide (CO) with vapour-deposited water(H2O) ices has been studied using temperature programmed desorption (TPD) and Fourier transform reflection-absorption infrared
spectroscopy (FT-RAIRS) over a range of astrophysically relevant temperatures. Such measurements have shown that CO desorption
from amorphous H2Oices is a much more complex process than current astrochemical models suggest. Re-visiting previously reported laboratory
experiments (Collings et al., 2003), a rate model has been constructed to explain, in a phenomenological manner, the desorption
of CO over astronomically relevant time scales. The model presented here can be widely applied to a range of astronomical
environments where depletion of CO from the gas phase is relevant. The model accounts for the two competing processes of CO
desorption and migration, and also enables the entrapment of some of the CO in the ice matrix and its subsequent release as
the water ice crystallises and then desorbs. The astronomical implications of this model are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
78.
We report multi-frequency and multi-epoch radio continuum observations with multi-spatial resolution for the low-luminosity active galactic nucleus (LLAGN) NGC 266. In the centimetre regime, we find diffuse components with Very Large Array (VLA) observations, and a variable compact core with a rising spectrum with Very Long Baseline Array (VLBA) observations. Although the spectral index of the rising spectrum is consistent with the prediction of the simple advection-dominated accretion flow (ADAF) model, the observed radio power is slightly high compared with that of the model prediction. A spectral break at centimetre-to-millimetre wavelengths is inferred from the upper limits of flux densities from Nobeyama Millimetre Array (NMA) and James Clerk Maxwell Telescope (JCMT) data at millimetre and submillimetre wavelengths, respectively. More complicated considerations are required for the theoretical model to interpret such observed radio properties. 相似文献
79.
K. R. Subramanian R. Ramesh M. S. Sundara Rajan Ch. V. Sastry 《Astrophysics and Space Science》1996,243(1):259-262
Observations of the Sun at two frequencies (51 and 77 MHz) using the East-West arm of the Gauribidanur Radio heliograph are presented. 相似文献
80.