科研之友
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摘要
We explore the environment of z approximate to 1 AGNs using a sample of 53 spectroscopically identified X-ray sources in the All-Wavelength Extended Groth Strip International Survey. We quantify the local density in the vicinity of an X-ray source by measuring the projected surface density of spectroscopically identified optical galaxies within a radius defined by the third-nearest neighbor. Our main result is that X-ray-selected AGNs at z approximate to 1 avoid underdense regions at a 99.89% confidence level. Moreover, although we find that the overall population shares the same (rich) environment with optical galaxies of the similar and U - B and M-B, there is also tentative evidence (96%) that AGNs with blue colors (U - B less than or similar to 1) reside in denser environments compared to optical galaxies. We argue that the results above are a consequence of the whereabouts of massive galaxies capable of hosting supermassive black holes at their centers, with available cold-gas reservoirs, the fuel for AGN activity. At z approximate to 1 an increasing fraction of such systems is found in dense regions.
- 出版日期2007-5-1
