2004MNRAS.349..193S

We present the reddening [E (V -I)] and extinction maps in the V band (A_V) and the I band (A_I) for 48 Optical Gravitational Lensing Experiment II (OGLE-II) Galactic bulge (GB) fields, covering a range of -11° < l < 11°, with the total area close to 11 deg². These measurements are based on two-band photometry of red clump giant (RCG) stars in OGLE-II VI maps of the GB. We confirm the anomalous value of the ratio of total to selective extinction R_VI≡A_V/E (V -I) = 1.9-2.1, depending on the line of sight, as measured recently by Udalski. By using the average value of R_VI = 1.964 with the standard deviation sdev = 0.085, we measured E (V -I), A_V and A_I, and we obtained extinction and reddening maps with a high spatial resolution of 26.7-106.8 arcsec, depending on the stellar density of each field. We have assumed that average, reddening corrected colours of RCGs are the same in every field. The maps cover the ranges 0.42 < E (V -I) < 3.5, 0.83 < A_V< 6.9 and 0.41 < A_I< 3.4 mag, respectively. The zero-points of these maps are calibrated by using V -K colours of 20 RR Lyrae ab variables (RRab) in Baade's window. The apparent reddening corrected I -band magnitudes of the RCGs change by +0.4 mag while the Galactic coordinate l varies from +5° to -5°, indicating that these stars are in the Galactic bar. The reddening corrected colour of RRab and RCGs in the GB are consistent with colours of local stars, while in the past these colours were claimed to be different.