Extinction ratios in the inner Galaxy as revealed by the VVV survey
  Interstellar extinction towards the Galactic Center is large and
significantly differential. Its reddening and dimming effects in red clump
stars in the Galactic Bulge can be exploited to better constrain the extinction
law towards the innermost Galaxy. By virtue of a deep and complete catalog of
more than 30 million objets at $|l|\le2.7\deg$ and $|b|\le1.55\deg$ obtained
from VVV survey observations, we apply the red clump method to infer the
selective-to-total extinction ratios in the $Z$, $Y$, $J$, $H$ and $K_s$
broadband near-infrared filters. The measured values are smaller than
previously reported, and are not constant, with mean values, e.g.,
$A_{K_S}/E(J-K_s)=0.428\pm0.005\pm0.04$ and
$A_{K_S}/E(H-K_s)=1.104\pm0.022\pm0.2$. We also obtain a ratio
$A_Z$:$A_Y$:$A_J$:$A_H$:$A_{K_S}$ of 7.74:5.38:3.30:1.88:1.0, implying
extinction towards the Galactic Center to follow a distribution as a function
of wavelength steeper than previously reported, consistent with a power law
$A_{\lambda}\propto{\lambda}^{-2.47}$ in the near-infrared.
