The inner Galactic bar traced by the VVV survey

Details The inner Galactic bar traced by the VVV survey The inner Galactic bar traced by the VVV survey

2011-10-05

arxiv.org/abs/1110.0925v1

Astronomy and Astrophysics

Astrophysics

Galaxy Astrophysics

Accepted for publication in A&A Letters

Scientific paper

We use the VVV survey observations in bulge regions close to the Galactic plane to trace the bar inclination at the Galactic latitude b\sim\pm1{\deg} and to investigate a distinct structure in the inner regions of the bar that was previously detected at positive latitude (b=+1{\deg}). We use the (J-Ks) colors of the red clump stars to obtain reddening values on 6 x 6 arcmin scale, minimizing the problems arising from differential extinction. Dereddened magnitudes are then used to build the luminosity function of the bulge in regions of ~0.4 sq deg to obtain the mean red clump magnitudes. These are used as distance indicators to trace the bar structure. The luminosity function clearly shows the red clump mean magnitude variation with longitude, as expected from a large scale bar oriented towards us at positive Galactic longitude, with a dereddened magnitude varying from Ks_0=13.4 at l=-10{\deg} to Ks_0=12.4 at l=+10{\deg}. We detect a change in the orientation of the bar in the central regions with |l|<4{\deg} at b=\pm1{\deg}, in agreement with results obtained at positive latitudes by other authors. Our results are based on a different dataset and at different latitude, which shows that this change in the bar orientation is real. This suggests that there is an inner structure distinct to the large-scale Galactic bar, with a different orientation angle. This inner structure could be a secondary, inner bar, with a semi-major axis of ~500 pc that is symmetric with respect to the Galactic plane.

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