2007A&A...461..893A


C.D.S. - SIMBAD4 rel 1.7 - 2019.08.22CEST23:09:37

2007A&A...461..893A - Astronomy and Astrophysics, volume 461, 893-909 (2007/1-3)

Spectral shape of the UV ionizing background and HeII absorption at redshifts 1.8 < z < 2.9.

AGAFONOVA I.I., LEVSHAKOV S.A., REIMERS D., FECHNER C., TYTLER D., SIMCOE R.A. and SONGAILA A.

Abstract (from CDS):

The shape of the UV ionizing background is reconstructed from optically thin metal absorption-line systems identified in spectra of HE 2347-4342, Q 1157+3143, and HS 1700+6416 in the redshift interval 1.8<z<2.9. The systems are analyzed by means of the Monte Carlo Inversion method completed with the spectral shape recovering procedure. The UVB spectral shape fluctuates at 2.4<z<2.9 mostly due to radiative transfer processes in the clumpy IGM. At z≲1.8, the IGM becomes almost transparent both in the HI and HeII Lyman continua and the variability of the spectral shape comes from diversity of spectral indices describing the QSO/AGN intrinsic radiation. At z>2.4, the recovered spectral shapes show intensity depression between 3 and 4Ryd due to HeII Lyα absorption in the IGM clouds (line blanketing) and continuous medium (true Gunn-Petersen effect). The mean HeII Lyα opacity estimated from the depth of this depression corresponds within 1-2σ to the values directly measured from the HI/HeII Lyα forest towards the quasars studied. The observed scatter in η= N(HeII)/N(HI) and anti-correlation between N(HI) and η can be explained by the combined action of variable spectral softness and differences in the mean gas density between the absorbing clouds. Neither of the recovered spectral shapes show features which can be attributed to the putative input of radiation from soft sources like starburst galaxies.

Abstract Copyright:

Journal keyword(s): cosmology: observations - line: formation - line: profiles - quasars: absorption lines - quasars: general - cosmology: diffuse radiation

Simbad objects: 7

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Number of rows : 7

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 QSO J0143-3917 QSO 01 43 33.6332299840 -39 17 00.065618732     16.28     ~ 23 0
2 QSO B0747+4259 QSO 07 50 54.6476110802 +42 52 19.234255219   16.43 16.23     ~ 39 0
3 QSO B0940-1050 QSO 09 42 53.5076745009 -11 04 25.929146122   16.96 16.6 16.6   ~ 82 0
4 QSO B1157+3143 QSO 12 00 06.2494598212 +31 26 30.839054589   16.76 16.47     ~ 55 0
5 HS 1700+6416 QSO 17 01 00.6195618802 +64 12 09.118927057   16.39 16.17     ~ 327 0
6 [CPS2005] QSO J2350-4325 abs 2.735 ALS 23 50 34.2 -43 26 00           ~ 2 0
7 QSO B2347-4342 QSO 23 50 34.2595236845 -43 25 59.680334378   16.3 16.3     ~ 156 0

    Equat.    Gal    SGal    Ecl

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2019.08.22-23:09:37

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