X-RAY ABSORPTION OF HIGH-REDSHIFT QUASARS
نویسندگان
چکیده
منابع مشابه
X - ray spectral properties of high - redshift radio - loud quasars beyond redshift 4 — first results ⋆
We present the results of X-ray spectroscopic observations with XMM-Newton for four high-redshift radio-loud quasars at z > 4. Among these, three objects, namely, GBB1508+5714, PMNJ0324-2918, and PKSB1251-407 do not show soft X-ray spectral flattening; the derived upper limits on assumed intrinsic absorption are (3.3 − 17.3) × 10 cm, the least of which is among the most stringent limits for z >...
متن کاملSoft X-Ray Absorption by High-Redshift Intergalactic Helium.
The Lyalpha absorption from intergalactic, once-ionized helium (He ii) has been measured with the Hubble Space Telescope in four quasars over the last few years in the redshift range 2.4<z<3.2. These observations have indicated that the He ii reionization may not have been completed until z approximately 2.8 and that large fluctuations in the intensity of the He ii-ionizing background were pres...
متن کاملHigh Redshift Hi 21cm Absorption toward Red Quasars
We have searched for redshifted absorption in the 21 cm line of neutral hydrogen toward 'red quasars', which are extragalactic radio sources with a steep spectral drop between optical and infrared wavelengths. The success rate for detecting HI 21cm absorption toward a representative sample of such sources is 80%. This compares to the much lower success rate of 11% for detecting HI 21cm absorpti...
متن کاملHigh - redshift obscured quasars
Using mid-infrared and radio criteria, we select a sample of candidate z ∼ 2 obscured quasars. Optical spectroscopy confirms about half of these as type-2 quasars, and modelling the population suggests 50-80% of the quasars are obscured. We find some flat radio spectrum type-2 quasars, and tentative evidence for obscuration unrelated to the torus. Using a similar sample, we also find evidence f...
متن کاملHigh resolution X-ray spectra of quasars
Past X-ray observations by ASCA suggest that warm absorbers (Ovii and Oviii edges) are apparently rare in high luminosity AGNs (quasars) while they are more common in low luminosity AGNs (Seyferts). However, this could be a selection effect if high luminosity AGNs have mostly narrow absorption lines (with no strong bound free edges), which escaped detection by the low resolution of ASCA. To che...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: The Astrophysical Journal
سال: 2013
ISSN: 0004-637X,1538-4357
DOI: 10.1088/0004-637x/774/1/29