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Caption: Figure 6.
Representative luminosity and redshift coverage of core BHM time-domain (left) and X-ray-selected (right) surveys of AGNs. Left panel: the distribution of absolute magnitude vs. redshift for BHM core time-domain spectra of SDSS quasars (here, highlighting a subset of ∼6000 with i < 19.1) enabled from the first year of SDSS-V. Both AQMES and RM targets are included, but AQMES predominates in this figure: the number of RM targets (especially at the plotted limit of i < 19.1) is comparatively small, though such RM targets are observed at a comparatively high cadence. The colors in this panel encode the number of time differences Δt between various pairs of optical spectral epochs (archival SDSS spectra, plus BHM spectra taken early with plates from APO). Building on the existing SDSS DR16 quasar survey allows BHM to efficiently expand spectral time-domain studies: the number of Δt values for a quasar scales as n(n − 1)/2, where n is the number of distinct SDSS spectral epochs; the number of SDSS quasar Δt values realized by BHM (to i < 19.1) via its first year alone roughly doubles that previously available for the entire DR16 quasar sample. Right panel: for the SPIDERS X-ray/optical survey, the larger and denser the coverage in this parameter space, the more stringent the constraints that can be placed on the history of accretion onto SMBHs in the Universe. The central plot in this panel compares SDSS-V’s eROSITA follow-up program (orange contours; ∼392,000 targets) and other current state-of-the-art AGN surveys: SDSS-IV/SPIDERS (blue; ∼4600 targets), a compilation of deep Chandra and XMM-Newton fields (black; CDFS, CDFN, COSMOS, Lockman Hole, XMM-XXL; ∼4000 targets), and SDSS-IV/V mini-survey (green; ∼10,000 targets). The top and right histograms in this panel show the number of AGNs expected in each of these comparison X-ray/optical samples. Note the logarithmic y-axes in both histograms: the eROSITA X-ray and SDSS-V optical sample will be about 100× larger than any existing sample, spanning a wide range of redshift and luminosities. The pink shading at z > 4 highlights the ∼10× improvement in the X-ray-selected SPIDERS AGN sample size at high redshift.
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© 2025. The Author(s). Published by the American Astronomical Society.
