Quasar Accretion Disk Sizes from Continuum Reverberation Mapping in the DES Standard-star Fields

Abstract

Measurements of the physical properties of accretion disks in active galactic nuclei are important for better understanding the growth and evolution of supermassive black holes. We present the accretion disk sizes of 22 quasars from continuum reverberation mapping with data from the Dark Energy Survey (DES) standard-star fields and the supernova C fields. We construct continuum light curves with the griz photometry that span five seasons of DES observations. These data sample the time variability of the quasars with a cadence as short as 1 day, which corresponds to a rest-frame cadence that is a factor of a few higher than most previous work. We derive time lags between bands with both JAVELIN and the interpolated cross-correlation function method and fit for accretion disk sizes using the JAVELIN thin-disk model. These new measurements include disks around black holes with masses as small as ∼10 7 M e , which have equivalent sizes at 2500 Å as small as ∼0.1 lt-day in the rest frame. We find that most objects have accretion disk sizes consistent with the prediction of the standard thin-disk model when we take disk variability into account. We have also simulated the expected yield of accretion disk measurements under various observational scenarios for the Large Synoptic Survey Telescope Deep Drilling Fields. We find that the number of disk measurements would increase significantly if the default cadence is changed from 3 days to 2 days or 1 day.

Current and Future Applications of Reverberation-Mapped Quasars in Cosmology

“…LSST will provide additional high quality photometry for these sources that will substantially improve these estimations. The proposed cadence (∼2 nights) of the observations of AGNs and the expected re-visits during the 10-year run will allow to (1) ensure a high lag recovery fraction for the relatively short accretion-disk lags expected (Yu et al, 2018); and (2) allow investigations of secular evolution of these lags that test the underlying model. LSST will also perform quality accretion disk reverberation mapping for ∼3000 AGNs in the DDFs.…”

OzDES multi-object fibre spectroscopy for the Dark Energy Survey: results and second data release

“…DES data have been used in many studies covering a diverse range of fields (Dark Energy Survey 2016). Notable examples include studies of bodies in the outer solar system (Khain et al 2018, for example), AGN accretion disk sizes (Mudd et al 2018;Yu et al 2020), dwarf galaxies and stellar streams in the halo of the Milky Way (Marshall et al 2019;Li et al 2019, for example) and rare transients such as merging neutron stars (Palmese et al 2017), super-luminous supernovae (Smith et al 2018;Angus et al 2019), and rapidly evolving transients (Pursiainen et al 2018).…”

“…It is one of the DES standard star fields that was observed during twilight. Yu et al (2020) used quasars in this field to study continuum reverberation mapping.…”

“…They follow the format presented in Yu15 and Ch17. The MaxVis field (Yu et al 2020) was observed for 155 minutes during run 28 on 25 and 26 December 2017.…”

Dust Reverberation Mapping in Distant Quasars from Optical and Mid-infrared Imaging Surveys

“…For surveys with multiband coverage, we also include r-band data (converted to g band) to increase the cadence; we only include PS1 and DES i-band data (converted to g band) when there are no g-band or r-band data within ±1 yr; no other bands were used given uncertainties in color transformations. We can safely ignore the small delays (a few days) across optical continuum bands owing to accretion disk RM for our quasars (e.g., Jiang et al 2017;Mudd et al 2018;Homayouni et al 2019;Yu et al 2020).…”