Wavelength-resolved Reverberation Mapping of quasar CTSC30.10: Dissecting MgII and FeII emission regions

Abstract

Context. We present the results of the reverberation monitoring aimed at MgII broad line and FeII pseudocontinuum for the luminous quasar CTS C30.10 (z = 0.90052) with the Southern African Large Telescope covering the years 2012-2021. Aims. We aimed at disentangling the MgII and UV FeII variability and the first measurement of UV FeII time delay for a distant quasar. Methods. We used several methods for time-delay measurements, and determined both FeII and MgII time delays as well as performed a wavelength-resolved time delay study for a combination of MgII and FeII in the 2700 -2900 Å restframe wavelength range. Results. We obtain the time delay for MgII of 275.5 +12.4 −19.5 days in the rest frame, while for FeII we have two possible solutions of 270.0 +13.8 −25.3 days and 180.3 +26.6 −30.0 in the rest frame. Combining this result with the old measurement of FeII UV time delay for NGC 5548 we discuss for the first time the radius-luminosity relation for UV FeII with the slope consistent with 0.5 within uncertainties. Conclusions. Since FeII time delay has a shorter time-delay component but lines are narrower than MgII, we propose that the line delay measurement is biased towards the BLR part facing the observer, with the bulk of the Fe II emission may arise from the more distant BLR region, one that is shielded from the observer.

Consistency study of high- and low-accreting Mg ii quasars: No significant effect of the Fe ii to Mg ii flux ratio on the radius-luminosity relation dispersion

“…3 More recently, we performed similar analyses using the largest available compilation of 118 H𝛽 QSO sources, where we found that the 2-parameter 𝑅 − 𝐿 relation H𝛽 cosmological constraints were somewhat (∼ 2𝜎) inconsistent with those from better-established cosmological probes (Khadka et al 2021a). To try to reduce the intrinsic dispersion of the QSO sample, attempts have previously been made to correct for the accretion-rate effect observed in the 2-parameter 𝑅 − 𝐿 relation (Du & Wang 2019;Martínez-Aldama et al 2020b;Zajaček et al 2021;Prince et al 2022) by extending it to a 3-parameter 𝑅 − 𝐿 relation. Partially to determine whether such a procedure might alter the H𝛽 cosmological constraints, we also considered a 3-parameter 𝑅 − 𝐿 relation, with optical R Fe being the third parameter (Khadka et al 2021a).…”

“…12 The scatter is partially also driven by the time-delay uncertainties since the determination of the broad-line time-delay requires long enough monitoring to be reliable. Adding just a few extra years of monitoring can change the rest-frame time-delay by as much as a factor of two, as was the case for one of the Mg quasars CTS C30.10 (Czerny et al 2019;Prince et al 2022). This can be mitigated by continued monitoring of already reverberation-mapped sources and by enlarging the sample using extensive photometric and spectroscopic surveys of higherredshift quasars.…”

Accretion disks, quasars and cosmology:meandering towards understanding.

“…Nearby faint sources require very dense monitoring while bright distance quasars require long monitoring of several years to measure the delay of the broad emission lines (e.g. Lira et al, 2018;Czerny et al, 2019;Zajaček et al, 2020Zajaček et al, , 2021Prince et al, 2022), the time delay for the continuum has not been measured so far for distant quasars, and all this can be done best with dedicated telescopes. Such dedicated, source-oriented monitoring combined with extensive simulations can also provide correction factors for massive surveys.…”