AGN Dust Lags

With debates of possible systematic e↵ects in any single type of probe (Efstathiou 2014, Planck consortium XXIII, 2015), complementary standard candles that test a similar range in redshift as SNe Ia are highly desirable. We propose to piggy-back on VEILS and the parallel DES survey to measure the time lags between accretion disk variability and the hot dust response around AGN to fully establish the AGN dust lags as standardisable candles in cosmology at 0

VEILS o↵ers a unique and, for some time, last opportunity to establish AGN dust lags as cosmological probes for only a relatively cheap observational cost, given that the only constraint is the cadencing of the total KS band exposure time required by our other science cases. We simulated VEILS for AGN dust lags, using the current knowledge and systematics in the lag-luminosity relation. All details are available in a technical white paper available at http://tinyurl.com/veils-agn-cosmo, building on our previous experience (Hoenig 2014, Hoenig et al. 2014). We show in Fig. 2 the constraints we will obtain on w⇤CDM cosmology, how they compare to the current SN Ia JLA sample, and how constraints improve when combining AGN and SNe. Most importantly, we will be able to (1) address systematic uncertainties in the SNe, (2) cross-calibrate both standardised candles in about 20-30 objects, and (3) achieve unprecedented low-z parameter constraints given the large number of objects in the combined sample. In terms of legacy, the AGN dust time lags will provide the much-needed low-z calibration for future high-redshift AGN cosmology surveys out to z ⇠ 6 (e.g. King et al. 2014, 2015).