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Louise O. V. Edwards † Carmelle Robert Mercedes Mollá Sean L. McGee 《Monthly notices of the Royal Astronomical Society》2009,396(4):1953-1971
We present integral field spectroscopy of the nebular line emission in a sample of nine brightest cluster galaxies (BCGs). The sample was chosen to probe both cooling flow and non-cooling flow clusters, as well as a range of cluster X-ray luminosities. The line emission morphology and velocity gradients suggest a great diversity in the properties of the line emitting gas. While some BCGs show evidence for filamentary or patchy emission (Abell 1060, Abell 1668 and MKW 3s), others have extended emission (Abell 1204, Abell 2199), while still others have centrally concentrated emission (Abell 2052). We examine diagnostic line ratios to determine the dominant ionization mechanisms in each galaxy. Most of the galaxies show regions with active galactic nucleus like spectra, however, for two BCGs, Abell 1060 and Abell 1204, the emission line diagnostics suggest regions which can be described by the emission from young stellar populations. The diversity of emission-line properties in our sample of BCGs suggests that the emission mechanism is not universal, with different ionization processes dominating different systems. Given this diversity, there is no evidence for a clear distinction of the emission-line properties between cooling flow and non-cooling flow BCGs. It is not always cooling flow BCGs which show emission (or young stellar populations), and non-cooling flow BCGs which do not. 相似文献
74.
As an important measurement parameter, global total electron content (TEC) is appropriate for the study of the Sun–Earth connection.
In this paper, the wavelet technique is employed to investigate the periodicities in global mean TEC during 1995–2008. Analysis
results show several remarkable components (including 27-day, semiannual and annual cycles) existing in global mean TEC with
obvious time-variable characteristics, besides 11-year cycle. After analyzing sunspot numbers and solar extreme ultra-violet
(EUV) radiation variations during this time period, except for semiannual variations, close correlation between global mean
TEC and solar variations is found, especially, a strong resemblance of the 27-day fluctuation exists in global mean TEC, sunspot
and solar EUV radiation variations. 相似文献
75.
The US Minerals Management Service (MMS) is responsible for safe and environmentally sound management of offshore oil and gas resources. In recent years, there has been a tremendous increase in both activities and plans for deepwater development of these resources in the Gulf of Mexico (GOM). As the industry meets the enormous technical challenges involved, there is a concomitant effort to assure environmental protection of deep-ocean and coastal resources. This paper will outline the research planning and program currently underway to assess impacts, identify potential problems, and discover more about unknown resources of the deep ocean. 相似文献
76.
本文应用CFD软件对多种流场的强大模拟功能,模拟小尺度的兰州市城关区风环境。选用SRTM资料表征兰州市城关区的地形,应用ArcGIS生成兰州市地形模型,计算相关参数,将计算得到的地形粗糙度和兰州多年气候资料转化为CFD模型的数字参数及模拟边界条件等,首次模拟得到河谷型地区兰州城关区的风环境。结果表明:(1)河谷型地区中,气流过山时风速达最大值,依山体高度增大,而在背风坡风速值明显降低,达到0~1 m·s-1;(2)气流过境时在沿河谷前进,且在谷底风速值达0~1 m·s-1;(3)在模拟城市热岛效应的对比实验中,地块加热对气流过境有停滞作用。 相似文献
77.
荒漠河岸胡杨(Populus euphratica)树干液流的时滞效应 总被引:1,自引:0,他引:1
以2012年4—9月树干液流速率与环境因子的实测数据,分析了荒漠河岸胡杨(Populus euphratica)树干液流的时滞效应。结果表明:不同月份胡杨树干液流速率对不同环境因子的时滞不同;4—9月,胡杨树干液流速率峰值时间比太阳辐射峰值时间晚约1h,比空气温度峰值时间早约1h,比水汽压差峰值时间早约2h,比空气相对湿度谷值时间早约2h;对影响胡杨树干液流速率的环境因子进行了主成分分析,发现胡杨树干液流速率与1h以前的第1主成分、第2主成分相关性最高,相关系数分别为0.864、0.875;对错位前后胡杨树干液流速率与环境因子进行多元线性回归分析发现,在胡杨树干液流的数值模拟中,考虑液流相对于环境因子的时滞效应可以提高模型的拟合精度。 相似文献
78.
新疆表壳元素地球化学特征 总被引:1,自引:1,他引:1
本次研究以国家"305"项目新获得积累的新疆地球化学勘查数据为基础,以岩石地层分区为框架,按照岩石地层单元出露情况,利用面积加权方法,在地理信息系统和数理统计分析系统下,对新疆及其三个主要地层区--塔里木地层区、中南天山-北山地层区和北疆地层区进行了39种元素的表壳元素丰度计算.计算结果显示新疆及其三个主要地层区表壳元素丰度总体表现出上陆壳的特点,但又各具差异,反映出新疆地壳的不均一性,塔里木地层区主要表现出成熟上陆壳,北疆地层区表现为年轻上陆壳,中南天山-北山地层区则呈现过渡特点.通过统计、对比,本次研究指出新疆表壳元素丰度受岩石地层单元元素丰度和岩石地层单元地表出露面积控制,其变化是地壳演化历史的产物,总体上并不服从正态分布,前人利用迭代剔除法获得的结果是值得商榷的. 相似文献
79.
论文在提出海洋和“新海洋”广度、深度空间概念的基础上,进一步诠释了作为新的海洋权益的控制权,及其在未来政治、经济、外交、军事等领域的重要作用。由于海洋蕴藏着巨大的可再生能源,论文从能源开发利用的视角分析了开发利用海洋深度空间的重要战略意义,并对解决我国海洋争端,开发海洋新能源及综合践行海洋深度空间权战略提出了应对策略。 相似文献
80.
The practice of gathering and harvesting wild foods has seen renewed interest in recent decades. In addition to contributing to food security and food sovereignty, foraging plays a role in promoting socioecological resilience and creating communities of belonging. However, foraging is generally prohibited by regulations governing public lands in the United States and elsewhere. The growth in food forests suggests public policymakers and land managers’ may be interested in reconsidering this broad prohibition of foraging but require an information base to do so. While a body of research on foraging exists, news media coverage of foraging represents an additional, readily available source of input. As a consequence, framings of foraging in media coverage likely influence managers’ deliberations on this practice. The current paper uses automated content analysis to understand how the practice of gathering and consuming wild foods is framed in print and digital news media, and how these depictions have varied in a 15-year period that includes the Great Recession. Our results show that prevalent framings of foraging represent it variously as a self-provisioning practice or a source of luxury commodities and experiences, with economic uncertainty appearing to affect the frequency of each framing by news media sources. Given managers’ ease of access to them, these distinct framings may influence future regulatory landscapes of foraging. 相似文献