Carregant...
Fitxers
Tipus de document
ArticleVersió
Versió publicadaData de publicació
Tots els drets reservats
Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/142068
The Chandra COSMOS-Legacy Survey: Source X-Ray Spectral Properties
Títol de la revista
Director/Tutor
ISSN de la revista
Títol del volum
Recurs relacionat
Resum
We present the X-ray spectral analysis of the 1855 extragalactic sources in the Chandra COSMOS-Legacy survey catalog having more than 30 net counts in the 0.5-7 keV band. A total of 38% of the sources are optically classified type 1 active galactic nuclei (AGNs), 60% are type 2 AGNs, and 2% are passive, low-redshift galaxies. We study the distribution of AGN photon index Γ and of the intrinsic absorption ${N}_{{\rm{H}},{\rm{z}}}$ based on the sources' optical classification: type 1 AGNs have a slightly steeper mean photon index Γ than type 2 AGNs, which, on the other hand, have average ${N}_{{\rm{H}},{\rm{z}}}\,\sim 3$ times higher than type 1 AGNs. We find that ~15% of type 1 AGNs have ${N}_{{\rm{H}},{\rm{z}}}\gt {10}^{22}$ cm−2, i.e., are obscured according to the X-ray spectral fitting; the vast majority of these sources have ${L}_{2\mbox{--}10\mathrm{keV}}\,\gt $ 1044 erg s−1. The existence of these objects suggests that optical and X-ray obscuration can be caused by different phenomena, the X-ray obscuration being, for example, caused by dust-free material surrounding the inner part of the nuclei. Approximately 18% of type 2 AGNs have ${N}_{{\rm{H}},{\rm{z}}}\lt {10}^{22}$ cm−2, and most of these sources have low X-ray luminosities (L ${}_{2\mbox{--}10\mathrm{keV}}\,\lt $ 1043 erg s−1). We expect a part of these sources to be low-accretion, unobscured AGNs lacking broad emission lines. Finally, we also find a direct proportional trend between ${N}_{{\rm{H}},{\rm{z}}}$ and host-galaxy mass and star formation rate, although part of this trend is due to a redshift selection effect.
Matèries
Matèries (anglès)
Citació
Citació
MARCHESI, Simone, LANZUISI, G., CIVANO, F., IWASAWA, Kazushi, SUH, H., COMASTRI, A., ZAMORANI, G., ALLEVATO, V., GRIFFITHS, R., MIYAJI, T., RANALLI, P., SALVATO, M., SCHAWINSKI, K., SILVERMAN, John d., TREISTER, E., URRY, C. m., VIGNALI, C.. The Chandra COSMOS-Legacy Survey: Source X-Ray Spectral Properties. _Astrophysical Journal_. 2016. Vol. 830, núm. 2. [consulta: 20 de gener de 2026]. ISSN: 0004-637X. [Disponible a: https://hdl.handle.net/2445/142068]