VVV Survey Microlensing: the Galactic Latitude Dependence

We search for microlensing events in fields along the Galactic minor axis, ranging from the Galactic center to -37 b < 39 using the VISTA Variables in the Via Lactea (VVV) survey near-IR photometry. The new search is made across VVV tiles b291, b305, b319, b347, b361, and b375, covering a total area of about 11.5 deg(2). We find a total of N = 238 new microlensing events in this new area, N = 74, which are classified as bulge red clump (RC) giant sources. Combining them with N = 122 events that we had previously reported in the Galactic center (VVV tile b333), allows us to study the latitude distribution of the microlensing events reaching the Galactic plane at b = 0(0) for the first time. We find a very strong dependence of the number of microlensing events with Galactic latitude, a number that increases rapidly toward the Galactic center by one order of magnitude from b = 0 degrees with a much steeper gradient than with Galactic longitude. The microlensing event population shows a flattened distribution (axial ratio b/a 1.5). The final sample shows a shorter mean timescale distribution than the Galactic plane sample for both the complete population and RC stars.