High Redshift Galaxies And Active Galaxies In The Deep Fields

With the launch of Chandra X-ray telescope in1999, the dawn of X-ray astronomy is coming. Chandra reveals many deep fields which have dramatic scientific values, such as Chandra Deep Field North and South. My thesis work started from analyzing the data from Chandra Deep Fields, then concentrate on the X-ray spectra of two special quasars in CDF-S. Due to the excellent spatial resolution of Chandra X-ray telescope, the X-ray data in Chandra Deep Fields are not only important for quasars and active galaxies, but also offer a new view on high-redshift galaxies. Recently there are many works to find high-redshift Lyman-a emitting (LAEs) galaxies through narrowband sur-veys, and these LAEs are key features for us to understand the formation and evolution of galaxies, especially at early universe. With the X-ray data in Chandra Deep Fields, we analyzed the X-ray properties of high-redshift Lya emitting galaxies, got the AGN fractions in these samples, derived the upper limit of SFR from X-ray, and constrain the escape fraction of Lya photons. Later we extended our research to the optical observa-tion and analysis of high-redshift LAEs, including the optical spectral confirmation, the Lya luminosity functions, equivalent width distribution of Lya, and clustering of these galaxies.In Chapter1, we introduced the development of X-ray astronomy and the Chandra Deep Fields, as well as the cosmic star formation history and methods for searching high-redshift star-forming galaxies. The following chapters are around the two main topics.In chapter2, we introduced the X-ray catalog based on the174ks Chandra X-ray exposure in LALA Cetus field. We showed the way from X-ray raw data to fits file used for final X-ray catalog. We also applied new co-adding method in this field for the analysis of cosmic X-ray background.The Chandra Deep Field South, where exists4incontinuus1Ms exposure, is the deepest X-ray field. We analyzed the Chandra observation of CDFS. Previous work by Prof. Junxian Wang found two quasars with relativistic outflows from their X-ray spectra in the first1Ms data in2000. We confirmed the existence of relativistic outflows in the second1Ms exposure in2007. This confirmation is necessary for the special observational feature (to exclude the background noise fluctuation). We found changes in both line center and line intensity, implying either the decrease of outflow velocity or change of outflow inoizational state.In Chapter4, we turned to analyze the X-ray properties of Lya emitting galaxies (LAEs) at z-4.5in CDF-S. Only1LAE with X-ray detection was confirmed as type1quasar at z=4.48, the others show non-detection. Even after applying X-ray stacking analysis, we did not find any X-ray signal, and only got an average (3σ) upper limit of (L0.5-2keV)<2.4x1042erg s-1. With the already known LAE-AGN found at other redshifts, we found that their EW(Lyα) are relativally small (<200A). Compared with the type1AGN templete and typical type2AGNs, we found that the AGN fraction in our sample should be very low, and these hidden AGNs might show low EW(Lya).In Chapter5, we continued the method introduced in Chapter4, to analyze the X-ray propertis of LAEs at redshift0.3,1.0,2.1,3.1,3.2,4.5,5.7and6.5. Only LAEs at z-0.3show X-ray detection, and their X-ray radiation are from star-formation pro-cesses. At higher redshifts, we did not find any detection even with stacking (excluded the LAE-AGNs). Since the X-ray is in-sensitive to dust, we can follow the Lx-SFR (star formation rate) relations to derive SFRX as the intrinsic SFR, and SFR from Lya, to constrain the Lya escape fraction in LAEs. Our results show consistence with Lya escape fraction derived from other methods. We found that, at z～2-3, the escape frac-tion of Lya photons is fLyαesc>14%(confidence level84%). We reject fLyαesc<5.7%at99.87%confidence level.From Chapter6-8, we analyze the spectroscopic observation of the z～4.5LAEs. With the spectroscopically confirmed LAEs, we discussed the Lyα Luminosity func-tions, the EW(Lya) distribution, and the clustering of LAEs at Chapter6,7, and8, re-spectively. In Chapter6, we combined previous z～4.5LAE surveys to get the unified Lya luminosity function at z～4.5, and compared with Lya LF at other redshifts. We found evolutions of Lya LFs, and integrated Lyα LFs over Lya luminosity, we found same luminosity density trend with integrated UV LFs over UV luminosity. The ratio of the two gave the global Lya escape fraction, which showed consistence over redshift2-4.5. In Chapter7about the distribution of EW(Lya), we used band ratio instead of observed EW(Lya) to ananlyze the intrinsic EW distribution. We found EW is inde-pedent with line intensity, and EW distribution following an exponential law through monte carlo simulations. The simulations also help for the further narrowband surveys. In Chapter8, we discuss the clustering properties of our spectroscopically confirmed LAEs, confirmed previous clustering work based on photometric sample only. We also found sub-samples of LAEs with larger Lya luminosity does not show larger clustering, which is not same to previous works.