VVV catalog of ab-type RR Lyrae in the inner Galactic bulge
M. Zoccali, C. Quezada, R. Contreras Ramos, E. Valenti, A., Valenzuela-Navarro, J. Olivares Carvajal, A. Rojas Arriagada, J. H. Minniti,, F. Gran, and M. De Leo

TL;DR
This paper presents a new catalog of nearly 16,500 ab-type RR Lyrae stars in the inner Galactic bulge, used to analyze the shape and distribution of the old, metal-poor stellar population, revealing an elongated spheroid structure.
Contribution
The study provides the largest high-purity RRab star catalog in the bulge and constrains its shape and orientation, improving understanding of the old bulge component.
Findings
The RR Lyrae distribution forms an elongated spheroid with b/a~0.7.
The spheroid is inclined at approximately 20 degrees to the line of sight.
Observational biases significantly affect distance and shape measurements.
Abstract
Context. Observational evidence has accumulated in the past years, showing that the Galactic bulge includes two populations, a metal poor and a metal rich one that, in addition to a different metallicity, show different alpha over iron abundances, spatial distribution, and kinematics. While the metal rich, barred component has been fairly well characterized, the metal poor, spheroidal component has been more elusive and harder to describe. RR Lyrae variables are clean tracers of the old bulge component, and they are, on average, more metal poor than red clump stars. Aims. In the present paper, we provide a new catalog of 16488 ab type RR Lyrae variables in the bulge region within -10<l<10 and -2.8<b<2.8, extracted from multi epoch PSF photometry performed on VISTA Variable in the Via Lactea survey data. We used the catalog to constrain the shape of the old, metal poor, bulge stellar…
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