Gemini Near Infrared Spectrograph$-$Distant Quasar Survey: the Chandra View
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| Format: | Preprint |
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2025
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| author | Marlar, Andrea Shemmer, Ohad Brotherton, Michael S. Richards, Gordon T. Dix, Cooper Matthews, Brandon M. Brandt, W. N. Plotkin, R. M. |
| author_facet | Marlar, Andrea Shemmer, Ohad Brotherton, Michael S. Richards, Gordon T. Dix, Cooper Matthews, Brandon M. Brandt, W. N. Plotkin, R. M. |
| contents | We present Chandra observations of 63 sources from the Gemini Near Infrared Spectrograph$-$Distant Quasar Survey (GNIRS-DQS) 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 H$β$-based Eddington luminosity ratio estimator, as well as the C IV $λ$1549 emission-line parameter space to investigate trends and correlations with the optical-X-ray spectral slope ($α_{\mathrm{ox}}$) and the effective hard-X-ray power-law photon index ($Γ$). We find that $α_{\mathrm{ox}}$ does not improve current accretion-rate estimates based on H$β$ or C IV. Instead, within the limitations of our sample, we confirm previous findings that the C IV parameter space may be a better indicator of the accretion rate up to $z\sim3.5$. 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, un-biased accretion-rate diagnostic. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_22272 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Gemini Near Infrared Spectrograph$-$Distant Quasar Survey: the Chandra View Marlar, Andrea Shemmer, Ohad Brotherton, Michael S. Richards, Gordon T. Dix, Cooper Matthews, Brandon M. Brandt, W. N. Plotkin, R. M. Astrophysics of Galaxies We present Chandra observations of 63 sources from the Gemini Near Infrared Spectrograph$-$Distant Quasar Survey (GNIRS-DQS) 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 H$β$-based Eddington luminosity ratio estimator, as well as the C IV $λ$1549 emission-line parameter space to investigate trends and correlations with the optical-X-ray spectral slope ($α_{\mathrm{ox}}$) and the effective hard-X-ray power-law photon index ($Γ$). We find that $α_{\mathrm{ox}}$ does not improve current accretion-rate estimates based on H$β$ or C IV. Instead, within the limitations of our sample, we confirm previous findings that the C IV parameter space may be a better indicator of the accretion rate up to $z\sim3.5$. 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, un-biased accretion-rate diagnostic. |
| title | Gemini Near Infrared Spectrograph$-$Distant Quasar Survey: the Chandra View |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2507.22272 |