TY - JOUR
T1 - The 500 ks Chandra observation of the z = 6.31 QSO SDSS J1030 + 0524
AU - Nanni, R.
AU - Gilli, R.
AU - Vignali, C.
AU - Mignoli, M.
AU - Comastri, A.
AU - Vanzella, E.
AU - Zamorani, G.
AU - Calura, F.
AU - Lanzuisi, G.
AU - Brusa, M.
AU - Tozzi, P.
AU - Iwasawa, K.
AU - Cappi, M.
AU - Vito, F.
AU - Balmaverde, B.
AU - Costa, T.
AU - Risaliti, G.
AU - Paolillo, M.
AU - Prandoni, I.
AU - Liuzzo, E.
AU - Rosati, P.
AU - Chiaberge, M.
AU - Caminha, G. B.
AU - Sani, E.
AU - Cappelluti, N.
AU - Norman, C.
N1 - Funding Information:
Acknowledgements. We acknowledge useful discussion with S. Ettori, G. Brunetti, G. Ghisellini, R. Decarli, E. Torresi, E. Lusso, S. Gallerani. We thank the anonymous referee for his/her useful comments and suggestions that improved the quality of this work. We acknowledge financial contribution from the agreement ASI-INAF n.2017-14-H.O and ASI-INAF I/037/12/0. The scientific results reported in this article are based on observations made by the Chandra X-ray Observatory. This work made use of data taken under the ESO program ID 095.A-0714(A). FC acknowledges funding from the INAF PRIN-SKA 2017 program 1.05.01.88.04.
PY - 2018/6/1
Y1 - 2018/6/1
N2 - We present the results from a ∼ 500 ks Chandra observation of the z = 6.31 QSO SDSS J1030 + 0524. This is the deepest X-ray observation to date of a z ∼ 6 QSO. The QSO is detected with a total of 125 net counts in the full (0.500A0-7 keV) band and its spectrum can be modeled by a single power-law model with photon index of Γ = 1.81 ± 0.18 and full band flux of f = 3.95 × 10-15 erg s-1 cm-2. When compared with the data obtained by XMM-Newton in 2003, our Chandra observation in 2017 shows a harder (ΔΓ ≈-0.6) spectrum and a 2.5 times fainter flux. Such a variation, in a timespan of ∼ 2 yr rest-frame, is unexpected for such a luminous QSO powered by a > 109M· black hole. The observed source hardening and weakening could be related to an intrinsic variation in the accretion rate. However, the limited photon statistics does not allow us to discriminate between an intrinsic luminosity and spectral change, and an absorption event produced by an intervening gas cloud along the line of sight. We also report the discovery of diffuse X-ray emission that extends for 30″ × 20″ southward of the QSO with a signal-to-noise ratio (S/N) of approximately six, hardness ratio of HR = 0.03+0.20 -0.25, and soft band flux of f0.5-keV = 1.1+0.3 -0.3 × 10-15 erg s-1 cm-2, that is not associated to a group or cluster of galaxies. We discuss two possible explanations for the extended emission, which may be either associated with the radio lobe of a nearby, foreground radio galaxy (at z ≈ 1-2), or ascribed to the feedback from the QSO itself acting on its surrounding environment, as proposed by simulations of early black hole formation.
AB - We present the results from a ∼ 500 ks Chandra observation of the z = 6.31 QSO SDSS J1030 + 0524. This is the deepest X-ray observation to date of a z ∼ 6 QSO. The QSO is detected with a total of 125 net counts in the full (0.500A0-7 keV) band and its spectrum can be modeled by a single power-law model with photon index of Γ = 1.81 ± 0.18 and full band flux of f = 3.95 × 10-15 erg s-1 cm-2. When compared with the data obtained by XMM-Newton in 2003, our Chandra observation in 2017 shows a harder (ΔΓ ≈-0.6) spectrum and a 2.5 times fainter flux. Such a variation, in a timespan of ∼ 2 yr rest-frame, is unexpected for such a luminous QSO powered by a > 109M· black hole. The observed source hardening and weakening could be related to an intrinsic variation in the accretion rate. However, the limited photon statistics does not allow us to discriminate between an intrinsic luminosity and spectral change, and an absorption event produced by an intervening gas cloud along the line of sight. We also report the discovery of diffuse X-ray emission that extends for 30″ × 20″ southward of the QSO with a signal-to-noise ratio (S/N) of approximately six, hardness ratio of HR = 0.03+0.20 -0.25, and soft band flux of f0.5-keV = 1.1+0.3 -0.3 × 10-15 erg s-1 cm-2, that is not associated to a group or cluster of galaxies. We discuss two possible explanations for the extended emission, which may be either associated with the radio lobe of a nearby, foreground radio galaxy (at z ≈ 1-2), or ascribed to the feedback from the QSO itself acting on its surrounding environment, as proposed by simulations of early black hole formation.
KW - Galaxies: active
KW - Galaxies: high-redshift
KW - Quasars: general
KW - X-rays: general
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U2 - 10.1051/0004-6361/201832694
DO - 10.1051/0004-6361/201832694
M3 - Article
AN - SCOPUS:85049650815
VL - 614
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
SN - 0004-6361
M1 - A121
ER -