Atmospheric aerosol samples collected in Beijing during 17-21 September 2004 were analyzed using the proton-induced X-ray emissions (PIXE) method,yielding concentrations of 20 elements.Analyzing the aerosol element si...Atmospheric aerosol samples collected in Beijing during 17-21 September 2004 were analyzed using the proton-induced X-ray emissions (PIXE) method,yielding concentrations of 20 elements.Analyzing the aerosol element size-spectrum distribution,enrichment factor (EF) and source over Beijing showed that under strong wind weather conditions,there were double peak distributions in the element size-spectra of Cu,S,K,Mn,As,Br,and Pb:one in fine mode and another in coarse mode.The peak in fine mode resulted from local emissions related to human activities,while the peak in coarse mode was caused by long range transport.The EF values of elements Ni,Cu,Zn,As,Se,Br,and Pb were relatively high,suggesting an evident characteristic polluted by regional aerosol.Results from factor analysis indicated that soil dust,coal-burning,industry and vehicle emissions contributed considerably to the autumn aerosol pollution in Beijing.展开更多
We present a systematic study to reveal the effect of host galaxy contamination to the identification of X-ray "unobscured" Seyfert 2 galaxies.We compiled a sample of 14 X-ray "unobscured" Seyfert ...We present a systematic study to reveal the effect of host galaxy contamination to the identification of X-ray "unobscured" Seyfert 2 galaxies.We compiled a sample of 14 X-ray "unobscured" Seyfert 2 galaxies and 29 X-ray obscured Seyfert 2s,with infrared [Ne II] and [O IV] emission line flux measurements.In this work we classify Seyfert 2s as "unobscured" or obscured in X-ray simply based on X-ray spectral fitting.We find that our X-ay "unobscured" Seyfert 2s have statistically higher [Ne II]/[O IV] line ratios,compared with obscured ones.Since the [Ne II]/[O IV] line ratio reflects the relative strength of star formation activity comparing with the SMBH accretion,the observed differences in [Ne II]/[O IV] line ratios clearly indicate relatively stronger X-ray contamination from star formation in the host galaxies in X-ray "unobscured" Seyfert 2s.Therefore we could attribute the X-ray "unobscured" appearance to host galaxy contamination for most(if not all) of our X-ray "unobscured" Seyfert 2s.Further analysis indicates that "unobscured" Seyfert 2s have intrinsically lower AGN luminosity but similar star formation rates,compared with obscured ones.This is also consistent with previous studies showing most X-ray "unobscured" Seyfert 2s are at lower luminosities,and relatively stronger contaminations from the host galaxies are thus expected.Finally we develop a screening criterion to distinguish potential pure Seyfert 2s from X-ray "unobscured" appearances which could be caused by strong host galaxy contamination.展开更多
基金supported by the National Basic Research Program of China (No. 2010CB428503)Project of the Beijing Municipal Financial Bureau (No. PXM2008_178305_ 06995)
文摘Atmospheric aerosol samples collected in Beijing during 17-21 September 2004 were analyzed using the proton-induced X-ray emissions (PIXE) method,yielding concentrations of 20 elements.Analyzing the aerosol element size-spectrum distribution,enrichment factor (EF) and source over Beijing showed that under strong wind weather conditions,there were double peak distributions in the element size-spectra of Cu,S,K,Mn,As,Br,and Pb:one in fine mode and another in coarse mode.The peak in fine mode resulted from local emissions related to human activities,while the peak in coarse mode was caused by long range transport.The EF values of elements Ni,Cu,Zn,As,Se,Br,and Pb were relatively high,suggesting an evident characteristic polluted by regional aerosol.Results from factor analysis indicated that soil dust,coal-burning,industry and vehicle emissions contributed considerably to the autumn aerosol pollution in Beijing.
基金supported by the National Natural Sciences Foundation of China (Grant No. 10825321)
文摘We present a systematic study to reveal the effect of host galaxy contamination to the identification of X-ray "unobscured" Seyfert 2 galaxies.We compiled a sample of 14 X-ray "unobscured" Seyfert 2 galaxies and 29 X-ray obscured Seyfert 2s,with infrared [Ne II] and [O IV] emission line flux measurements.In this work we classify Seyfert 2s as "unobscured" or obscured in X-ray simply based on X-ray spectral fitting.We find that our X-ay "unobscured" Seyfert 2s have statistically higher [Ne II]/[O IV] line ratios,compared with obscured ones.Since the [Ne II]/[O IV] line ratio reflects the relative strength of star formation activity comparing with the SMBH accretion,the observed differences in [Ne II]/[O IV] line ratios clearly indicate relatively stronger X-ray contamination from star formation in the host galaxies in X-ray "unobscured" Seyfert 2s.Therefore we could attribute the X-ray "unobscured" appearance to host galaxy contamination for most(if not all) of our X-ray "unobscured" Seyfert 2s.Further analysis indicates that "unobscured" Seyfert 2s have intrinsically lower AGN luminosity but similar star formation rates,compared with obscured ones.This is also consistent with previous studies showing most X-ray "unobscured" Seyfert 2s are at lower luminosities,and relatively stronger contaminations from the host galaxies are thus expected.Finally we develop a screening criterion to distinguish potential pure Seyfert 2s from X-ray "unobscured" appearances which could be caused by strong host galaxy contamination.
