More variable quasars have stronger emission lines
  The UV/optical variation, likely driven by accretion disc turbulence, is a
defining characteristic of type 1 active galactic nuclei (AGNs) and quasars. In
this work we investigate an interesting consequence of such turbulence using
quasars in SDSS Stripe 82 for which the measurements of the UV/optical
variability amplitude are available from $\sim$ 10 years long light curves. We
discover positive correlations between UV/optical variability amplitude
$\sigma_{rms}$ and equivalent widths of CIV, Mg II and [OIII]5007 emission
lines. Such correlations remain statistically robust through partial
correlation analyses, i.e., after controlling the effects of other variables
including bolometric luminosity, central supermassive black hole mass,
Eddington ratio and redshift. This, for the first time, indicates a causal link
between disc turbulence and emission line production. We propose two potential
underlying mechanisms both of which may be involved: 1) quasars with stronger
disc turbulence have on average bluer/harder broadband SED, an expected effect
of the disc thermal fluctuation model; 2) stronger disc turbulence could lead
to launch of emission line regions with larger covering factors.
