TY - JOUR
T1 - X-ray spectroscopy and variability of AGN detected in the 2 Ms Chandra Deep Field-North Survey
AU - Bauer, F. E.
AU - Vignali, C.
AU - Alexander, D. M.
AU - Brandt, W. N.
AU - Garmire, G. P.
AU - Hornschemeier, A. E.
AU - Broos, P. S.
AU - Townsley, L. K.
AU - Schneider, D. P.
N1 - Funding Information:
We gratefully acknowledge the financial support of NSF CAREER award AST-9983783 (FEB, CV, DMA, WNB), NASA Grant NAS 8-38252 (GPG, PI), NASA GSRP Grant NGT5-50247 (AEH), and NSF Grant AST-9900703 (DPS). This work would not have been possible without the support of the entire Chandra and ACIS teams.
PY - 2004
Y1 - 2004
N2 - We investigate the nature of the faint X-ray source population through X-ray spectroscopy and variability analyses of 136 active galactic nuclei (AGN) detected in the 2 Ms Chandra Deep Field-North Survey with >200 background-subtracted 0.5-8.0 keV counts [F 0.5-8.0 keV = (1.4-200) × 10 -15 erg cm -2 s -1 ]. Our preliminary spectral analyses yield median spectral parameters of T = 1.61 and intrinsic N H - 6.2 × 10 21 cm -2 (z = 1 assumed when no redshift available) when the AGN spectra are fitted with a simple absorbed power-law model. However, considerable spectral complexity is apparent (e.g., reflection, partial covering) and must be taken into account to model the data accurately. Moreover, the choice of spectral model (i.e., free vs. fixed photon index) has a pronounced effect on the derived JVH distribution and, to a lesser extent, the X-ray luminosity distribution. We also=find that among the 136 AGN, 10 (≈7%) show significant Fe Kα emission-line features with equivalent widths in the range 0.1-1.3 keV. Two of these emission-line AGN could potentially be Compton thick (i.e., Γ < 1.0 and large Fe Kα equivalent width). Finally, we find that 81 (≈60%) of the 136 AGN show signs of variability, and that this fraction increases significantly (≈80-90%) when better photon statistics are available.
AB - We investigate the nature of the faint X-ray source population through X-ray spectroscopy and variability analyses of 136 active galactic nuclei (AGN) detected in the 2 Ms Chandra Deep Field-North Survey with >200 background-subtracted 0.5-8.0 keV counts [F 0.5-8.0 keV = (1.4-200) × 10 -15 erg cm -2 s -1 ]. Our preliminary spectral analyses yield median spectral parameters of T = 1.61 and intrinsic N H - 6.2 × 10 21 cm -2 (z = 1 assumed when no redshift available) when the AGN spectra are fitted with a simple absorbed power-law model. However, considerable spectral complexity is apparent (e.g., reflection, partial covering) and must be taken into account to model the data accurately. Moreover, the choice of spectral model (i.e., free vs. fixed photon index) has a pronounced effect on the derived JVH distribution and, to a lesser extent, the X-ray luminosity distribution. We also=find that among the 136 AGN, 10 (≈7%) show significant Fe Kα emission-line features with equivalent widths in the range 0.1-1.3 keV. Two of these emission-line AGN could potentially be Compton thick (i.e., Γ < 1.0 and large Fe Kα equivalent width). Finally, we find that 81 (≈60%) of the 136 AGN show signs of variability, and that this fraction increases significantly (≈80-90%) when better photon statistics are available.
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U2 - 10.1016/j.asr.2003.02.082
DO - 10.1016/j.asr.2003.02.082
M3 - Article
AN - SCOPUS:9544251406
SN - 0273-1177
VL - 34
SP - 2555
EP - 2560
JO - Advances in Space Research
JF - Advances in Space Research
IS - 12 SPEC.ISS.
ER -