The extinction law in the inner 3 × 3 deg2 of the Milky Way and the red clump absolute magnitude in the inner bar-bulge

The extinction law from $0.9$ to $8$ microns in the inner $3\times3$ deg$^2$ of Milky Way is measured using data VISTA Variables Via Lactea, GLIMPSE and WISE. Absolute ratios are found by requiring that observed red clump density peaks at GRAVITY collaboration distance Galactic centre. When combined with selective bulge giant colour-colour diagrams, we find an $A_Z:A_Y:A_J:A_H:A_{K_s}:A_{W1}:A_{[3.6]}:A_{[4.5]}:A_{W2}:A_{[5.8]}:A_{[8.0]} =7.19(0.30):5.11(0.20):3.23(0.11):1.77(0.04):1:0.54(0.02):0.46(0.03):0.34(0.03):0.32(0.03):0.24(0.04):0.28(0.03)$ valid for low extinctions where non-linearities unimportant. These results imply Rayleigh Jeans colour excess method (RJCE) $A_{K_s}=0.677(H-[4.5]-0.188)$. We little evidence significant ratio variation over inspected region (around $5\%$). Assuming absolute do not vary across gives independent measurement $K_s$ magnitude Centre $(-1.61\pm0.07)\,\mathrm{mag}$. This very similar value solar neighbourhood stars giving confidence use as standard candles Galaxy. As part our analysis, inspect completeness PSF photometry VVV survey artificial star tests, finding $90\%$ $K_s\approx16 \,(17)$ high (low) regions good agreement number counts respect GALACTICNUCLEUS DECAPS catalogues small survey.