
I have chosen as the subject of today’s talk the X-ray observation of extragalactic objects. Since several talks will be given at this meeting regarding the study of nearby normal and active galaxies, I Will confine myself to discuss these objects that are particularly interesting from the point of view of evolution of structure in the universe. In particular I will highlight the progress brought about by the Einstein mission in our understanding of clusters, quasars and X-ray background and on future lines of research on these topics.
| selected citations These citations are derived from selected sources. This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | 4 | |
| popularity This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network. | Top 10% | |
| influence This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | Top 10% | |
| impulse This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network. | Top 10% |
