Extinction law and stellar mass in the nuclear bulge from kinematically selected red clump stars

The nuclear bulge of the Milky Way harbors stellar populations that provide crucial insights into galaxy formation processes and serve as a nearby analog for understanding bulge formation in external galaxies. However, detailed studies of this region are severely hampered by extreme and highly variable interstellar extinction, which obscures the intrinsic stellar properties and impedes accurate stellar mass determinations. Our goal is to measure the extinction law toward the nuclear bulge and to estimate its stellar density. We developed a method for determining the extinction law toward the nuclear bulge by kinematically selecting red clump stars that belong to this region. We created a reddening map with a high spatial resolution and computed stellar mass with completeness-corrected red clump star counts, scaled from empirical measurements. We find a total-to-selective extinction ratio of mathrm A_K/ E_ H-K = 1.259 ± 0.074 and an extinction ratio of = 1.794 ± 0.046, which are consistent with previous works. The reddending map with the high spatial resolution shows clear filamentary structures and a gradient in the extinction over the giant molecular cloud G0.253+0.016 (i.e., the Brick). From the star counts, we measured a stellar mass of M_⊙ for the nuclear bulge, in agreement with other mass estimates.