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Abstract We present new Chandra observations of seven luminous quasars atz> 6.5. Combined with archival Chandra observations of all other known quasars, they form nearly complete X-ray observations of all currently knownz∼ 7 quasars withM1450< –26.5, except for J0313−1806 atz= 7.642 and J0910−0414 atz= 6.636. Together with existing ground-based near-infrared spectroscopy and Atacama Large Millimeter Array observations, we investigate the correlations between X-ray emission (the X-ray luminosityLXand the optical/UV-to-X-ray spectral slopeαOX) and various quasar properties (rest-UV luminosityL2500 Å, bolometric luminosityLbol, Civblueshift, and infrared luminosityLIR). We find mostz> 6.5 quasars follow a similarαOX–L2500 Årelation asz∼ 1–6 quasars, but also display a large scatter. We find a potential correlation betweenαOXand the Civblueshift, suggesting a soft optical/UV-to-X-ray spectral energy distribution shape is frequently associated with fast disk winds. Furthermore, we analyze the X-ray spectrum of 11 quasars atz> 6.5 with Chandra detection, and find that the best-fit photon index, Γ, is 2.41 ± 0.27, which is likely driven by high accretion rates ofz> 6.5 quasars. In addition, we find there are no significant correlations between eitherLXandLIR, norLbolandLIR, suggesting no strong correlations between quasar luminosity and star formation luminosity for the most luminous quasars atz> 6.5.
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Gemini Near Infrared Spectrograph–Distant Quasar Survey: The Chandra View
Abstract We present Chandra observations of 63 sources from the Gemini Near Infrared Spectrograph−Distant Quasar Survey, of which 54 were targeted by snapshot observations in Cycle 24. A total of 55 sources are clearly detected in at least one X-ray band, and we set stringent upper limits on the X-ray fluxes of the remaining eight sources. In combination with rest-frame ultraviolet–optical spectroscopic data for these sources, we assess whether X-rays can provide a robust accretion rate indicator for quasars, particularly at the highest accessible redshifts. We utilize a recently modified Hβ-based Eddington luminosity ratio estimator, as well as the Civλ1549 emission-line parameter space, to investigate trends and correlations with the optical–X-ray spectral slope (αox) and the effective hard X-ray power-law photon index (Γ). We find thatαoxdoes not improve current accretion rate estimates based on Hβor Civ. Instead, within the limitations of our sample, we confirm previous findings that the Civparameter space may be a better indicator of the accretion rate up toz ∼ 3.5. We also find that the average Γ values for a small subset of our sources, as well as the average Γ value in different groupings of our sources, are consistent with their respective relatively high Eddington luminosity ratios. Deeper X-ray observations of our X-ray-detected sources are needed for measuring Γ accurately and testing whether this parameter can serve as a robust, unbiased accretion rate diagnostic.
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- Award ID(s):
- 2407089
- PAR ID:
- 10688964
- Publisher / Repository:
- The Astrophysical Journal
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 991
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 91
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.3847/1538-4357/adf4dd
