Probing the nuclear activity with supermassive black holes     

V.D. Ivanov  A. Alonso-Herrero 《Astrophysics and Space Science》2003,284(2):565-568

We report three new or updated techniques for probing the parameters of active galaxies based on the masses of their central black holes M_BH). First, we derived a near-IR analog of the bulge luminosity versus M_BH relationship. The low scatter makes it a promising new tool to study the black hole demographics. Next, we present relations between M_BH and the10 μm and 2-10 keV nuclear luminosity. They may help to study the M_BH evolution over wide redshift ranges. Finally, we measured M_BH in quasars from z ∼ 3.4 to z ∼ 0.3 to search directly for M_BH growth. Surprisingly, we found no evidence for growth implying that the majority of quasar host galaxies have undergone their last major merger at z ≥ 3. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Interstellar Extinction and the Intrinsic Colors of Classical Cepheids in the Galaxy, the LMC, and the SMC     

G. V. Abrahamyan 《Astrophysics》2003,46(3):304-318

New methods are applied to samples of classical cepheids in the galaxy, the Large Magellanic Cloud, and the Small Magellanic Cloud to determine the interstellar extinction law for the classical cepheids, R _B:R _V:R _I:R _J:R _H:R _K= 4.190:3.190:1.884:0.851:0.501:0.303, the color excesses for classical cepheids in the galaxy, E(B-V)=-0.382-0.168logP+0.766(V-I), and the color excesses for classical cepheids in the LMC and SMC, E(B-V)=-0.374-0.166logP+0.766(V-I). The dependence of the intrinsic color (B-V)₀ on the metallicity of classical cepheids is discussed. The intrinsic color (V-I)₀ is found to be absolutely independent of the metallicity of classical cepheids. A high precision formula is obtained for calculating the intrinsic colors of classical cepheids in the galaxy: (<B>-<V>)₀=0.365(±0.011)+0.328(±0.012)logP.  相似文献   

Characters of the Pco2 and CO2 Flux in the East China Sea in Autumn     

纪雷  崔鹤  辛淑平  王军  张龙军  陆贤昆 《中国海洋湖沼学报》2003,21(2):180-186

Pco2 of air and seawater samples from the East China Sea(ECS) were measured in situ in autumn, 1994,Ocean currents,terrestrial fluviation,biological activities,etc.,Pco2 char-acters in air and seawater were investigated,CO2 flux and its character in the East China Sea are discussed on the basis of the Pco2 profiles of air and seawater,It was clear that the nearshore was the source of CO2;and tht the oulter sea area was the sink of CO2; and that the shelf area of the EXS is a net sink for atmospheric CO2 in autumn.  相似文献   

STUDY ON THE INTERACTION BETWEEN NDVI PROFILE AND THE GROWING STATUS OF CROPS   总被引：5，自引：1，他引：4  

JIANGDong WANGNai-bin YANGXIao-huan WANGJi-hua 《中国地理科学(英文版)》2003,13(1):62-65

Daily and ten-day Normalized Difference Vegetation Index(NDVI) of crops were retrieved from meteorological statellite NOAA AVHRR images ,The temporal variations of the NDVI were analyzed during the whole growing season,and thus the principle of the interaction between NDIV profile and the growing status of crops was discussed,As a case in point,the relationship between integral NDVI and winter wheat yield of Henan Province in 1999 had been analyzed.By putting integral NDVI values of 60 sample counties into the winter wheat yield-integral NDVI coordination,scattering map was plotted. It demonstrated that integral NDVI had a close relation with winter wheat yield.These relation could be described with linear,cubic polynomial ,and exponential regression,and the cubic polynomial regression was the best way,In general ,NDVI reflects growing status of green vegetation ,so crop monitoring and crop yield estimation could be realized by using remote sensing technique on the basis of time serial NDVI data together with agriculture calendars.  相似文献   

Photometric Study of the W Uma-Type Eclipsing Binary System GSC 4832.400     

M. Jurado Vargas  P. Merchán BenÍtez 《Astrophysics and Space Science》2003,288(3):237-244

We present a photometric analysis of the eclipsing binary systemGSC4832.400 based on 732 photometric observations obtained on sixteen clear nights during 1999–2000 in the V-Johnson and yb-Strömgren filters. The observed times of the minima yielded a linear ephemeris showing that the system has a constant period of 0.313150 ± 0.000002days. The light curve corresponds to a circular orbit for the system and clearly shows that GSC4832.400 has the defining characteristics of a W UMa-type eclipsing binary. It also shows a small O'Connell effect, which could be due to the presence of a hot spot in the primary star. A preliminary photometric solution based on the assumption of an over contact systemsatis factorily reproduced the observed light curve.  相似文献   

DISASTER ANALYSIS AND COUNTERMEASURES OF LAND SUBSIDENCE CAUSED BY COAL CUTTING IN CHINA     

YANGYong-liang SHITong-guang JLANGLU-guang LIYue 《中国地理科学(英文版)》2003,13(2):130-133

In recent years, many coal-producing countries have paid great attention to the land subsidence causedby coal cutting. In China, because of the dense population in coalfield areas, the land subsidence hazard is more seri-ous. After a brief analysis on the mechanism of land subsidence, this paper gives a comprehensive and systematical ac-count on all kinds of hazards caused by the land subsidence in China. The study shows that land subsidence has endan-gered land, buildings, traffic and communication lines, dykes and dams. It also causes damage to ecological and socialenvironment. In order to lessen the hazard of land subsidence, preventive measures should be taken to reduce the col-lapse amount, such as extraction with stowing, banded mining system, succession and coordination mining system, orhigh-pressure mudflow between rock strata. Measures of reinforcing or moving certain buildings should also be taken toreduce the destructive degree. In order to harness the subsidence land and bring them under control for fanning, mea-sures should be taken such as filling with spoil or fine breeze, excavating the deeper and covering the shallower land.  相似文献   

The shape of the rotation curves of edge-on galaxies     

A. V. Zasov  A. V. Khoperskov 《Astronomy Letters》2003,29(7):437-446

We consider the effects of projection, internal absorption, and gas-or stellar-velocity dispersion on the measured rotation curves of galaxies with edge-on disks. Axisymmetric disk models clearly show that the rotational velocity in the inner galaxy is highly underestimated. As a result, an extended portion that imitates nearly rigid rotation appears. At galactocentric distances where the absorption is low (i.e., it does not exceed 0.3–0.5^m kpc^?1), the line profiles can have two peaks, and a rotation curve with minimum distortions can be obtained by estimating the position of the peak that corresponds to a higher rotational velocity. However, the high-velocity peak disappears in high-absorption regions and the actual shape of the rotation curve cannot be reproduced from line-of-sight velocity estimates. In general, the optical rotation curves for edge-on galaxies are of little use in reconstructing the mass distribution in the inner regions, particularly for galaxies with a steep velocity gradient in the central region. In this case, estimating the rotation velocities for outer (transparent) disk regions yields correct results.  相似文献   

Radiation from hot, bare, strange stars     

A. G. Aksenov  M. Milgrom  V. V. Usov 《Monthly notices of the Royal Astronomical Society》2003,343(3):L69-L72

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SORPTION AND DESORPTION CHARACTERISTICS OF CADMIUM BY FOUR DIFFERENT SOILS IN NORTHEAST CHINA   总被引：3，自引：0，他引：3  

ZHANG Lei SONG Feng-bin 《中国地理科学(英文版)》2005,15(4):343-347

1IN TR O D U C TIO NA s a persistentand toxic pollutant, cadm ium (C d) canresultin m any adverse health effects in a variety oftis-suesand organssuch asthe lung,kidney,urinary,blad-der,pancreas,breast and prostate (SA TA R U G etal.,2003).C adm ium in so…  相似文献   

Rigidly rotating modes of the solar magnetic field     

D. V. Erofeev 《Solar physics》1996,167(1-2):25-45

Discrete rigidly rotating components (modes) of the large-scale solar magnetic field have been investigated. We have used a specially calculated basic set of functions to resolve the observed magnetic field into discrete components. This adaptive set of functions, as well as the expansion coefficients, have been found by processing a series of digitized synoptic maps of the background magnetic field over a 20-year period. As a result, dependences have been obtained which describe the spatial structure and the temporal evolution of the 27-day and 28-day rigidly rotating modes of the Sun's magnetic field.The spatial structure of the modes has been compared with simulations based on the known flux-transport equation. In the simulations, the rigidly rotating modes were regarded as stationary states of the magnetic field whose rigid rotation and stability were maintained by a balance between the emergence of magnetic flux from stationary sources located at low latitudes and the horizontal transport of flux by turbulent diffusion and poleward directed meridional flow. Under these assumptions, the structure of the modes is determined solely by the horizontal velocity field of the plasma, except for the low-latitude zone where sources of magnetic flux concentrate. We have found a detailed agreement between the simulations and the results of the data analysis, provided that the amplitude of the meridional flow velocity and the diffusion constant are equal to 9.5 m s^–1 and 600 km² s^–1, respectively.The analysis of the expansion coefficients has shown that the rigidly rotating modes undergo rapid step-like variations which occur quasi-periodically with a period of about two years. These variations are caused by separate surges of magnetic flux in the photosphere, so that each new surge gives rise to a rapid replacement of old large-scale magnetic structures by newly arisen ones.  相似文献