The X-Ray Spectrum of the z=6.30 QSO SDSS J1030+0524

Abstract

We present a deep XMM-Newton observation of the z=6.30 QSO SDSS J1030+0524, the second most distant quasar currently known. The data contain sufficient counts for spectral analysis, demonstrating the ability of XMM-Newton to measure X-ray spectral shapes of z~6 QSOs with integration times >~100 ks. The X-ray spectrum is well fitted by a power law with index Γ=2.12+/-0.11, an optical-X-ray spectral slope of α_ox=-1.80, and no absorption excess to the Galactic value, although our data are also consistent with a power-law index in the range 2.02<Γ<2.5 and excess absorption in the range 0<N_H(cm^-2)<8×10²². There is also a possible detection (~2 σ) of FeKα emission. The X-ray properties of this QSO are, overall, similar to those of lower redshift radio-quiet QSOs. This is consistent with the statement that the X-ray properties of radio-quiet QSOs show no evolution over 0<z<6.3. Combined with previous results, this QSO appears indistinguishable in any way from lower redshift QSOs, indicating that QSOs comparable to those seen locally existed less than 1 Gyr after the big bang.