Speaker
Description
Quasar winds blown from the accretion disc are potentially capable of expelling large quantities of gas from their host galaxies and may thus be an important mechanism for feedback. These winds are evident in rest-frame UV spectra in the form of blueshifted broad emission lines. How such winds are launched – and how such launching relates to the physical state of the accretion disc system that powers quasars – remains a key open question. SDSS-V follow-up of eROSITA sources is yielding a large quasar sample for which we have access to their wind properties and (via measurements of the X-ray, UV and optical emission) constraints on their accretion state. I will present new measurements for a sample of redshift 1.5-3.5 quasars that quantify how the strength of quasar accretion disc-winds (from the CIV emission line) depends on both the strength of the UV ionising continuum (probed via HeII emission) and the X-ray properties derived from the eROSITA spectra (i.e., photon index and $N_H$ column density). We show that quasars with a given X-ray luminosity have a broad range of wind properties that appear to depend on the presence (or lack) of a strong, UV-bright inner accretion disc (revealed by the HeII emission line strength). A strong UV component can lead to over-ionisation of the wind such that the outflow strength is decreased. These results point to radiation-driven winds whose strength and presence are highly sensitive to the physical structure of the accretion system. With this information in hand we can investigate what, if any, X-ray conditions are required for driving winds and gain a new perspective of the wind properties of the X-ray selected quasars.
