| We have investigated the detection of cosmic reionizational signal in fre-quency space through relatively comprehensive and precise simulation for fore-ground components, and trials of foreground removal by polynomial fitting. Be-sides, we have researched, in galaxy group RGH 80, the efficects of ram pressurestripping caused by mergers in metal enrichment of the inter-galactic medium.The detection of the cosmological 21cm signal from the reionization epochis currently the most important method of obtaining information about the uni-verse in this epoch, and has become a popular frontier subject in Astrophysics.We introduce the radiation mechanism, power spectrum and simulation of 21cmsignal. Then we simulate the foregrounds and detector noise in 21cm signalprobe. For the foregrounds, we discuss the contribution from Milky Way Galaxy,AGNs (FRI&FRIIs, radio-quiet AGNs and GPS&CSSs), star-forming galaxiesand galaxy clusters. As for detector noise, we simulate it as Gaussian Whitenoise, referring to the instrument parameters of 21CMA and LOFAR. With thesimulation result, we try the foreground removal and find the quadratic polyno-mial fitting method has certain risk of over-fitting large-scale structure of 21cmsignal into foregrounds. Despite this, this method is still able to reconstructpower spectrum of the 21cm signal for wavenumber k > 0.4 Mpc-1.The second part of this dissertation is about research on the contributionof ram pressure stripping to metal enrichment of the inter-galactic medium. Westudy the high-quality Chandra ACIS data of RGH 80 group, in which an arm-like X-ray feature was found. We calculate the two dimensional temperature andabundance maps of its X-ray gas and find a high-abundance arc structure onits abundance map, in which the metal abundance is significantly higher than the surrounding regions by 0.3 Z . We prove that there are tight spatialcorrelations among the arm-like feature on X-ray map, the high-abundance arcon abundance map, and the member galaxy PGC 046529, and we speculatethat the high-abundance arc is the remnant of the inter-stellar medium of PGC046529, which was stripped out of this galaxy by ram pressure caused by themotion of PGC 046529. This case shows that ram pressure can also serve as anefficient metal enrichment mechanism in galaxy groups. |
