Variability and stellar populations with deep optical-IR images of the Milky Way disk: matching VVV with VLT/VIMOS data

TL;DR

This study combines deep optical and infrared observations to analyze stellar variability and populations in the Milky Way disk, revealing new variable stars and insights into galactic structure and dust distribution.

Contribution

It presents the first detection of most variables in this region, compares observations with the Besancon model, and investigates the distribution of dust and stellar populations.

Findings

Detected 333 variables, mostly eclipsing binaries and delta Scuti pulsators.

Eclipsing/ellipsoidal variables occur at a rate of ~0.28%, close to ground-based detections.

Identified absorbing clouds at 11-13 kpc from the Sun in the Carina-Sagittarius Arm.

Abstract

We have used deep V-band and JHKs-band observations to investigate variability and stellar populations near the Galactic plane in Centaurus, and compared the observations with the Galactic model of Besancon. By applying image subtraction technique to a series of over 580 V-band frames taken with the ESO VLT/VIMOS instrument during two contiguous nights in April 2005, we have detected 333 variables among 84,734 stars in the brightness range 12.7<V<26.0 mag. Infrared data collected in March 2010 with the new ESO VISTA telescope allowed us to construct deep combined optical-IR colour-magnitude and colour-colour diagrams. All detected variables but four transit candidates are reported for the first time. The majority of the variables are eclipsing/ellipsoidal binaries and delta Scuti-type pulsators. The occurrence rate of eclipsing/ellipsoidal variables reached ~0.28% of all stars. This is very close to the highest fraction of binary systems detected using ground-based data so far (0.30%), but still about four times less than the average occurrence rate recently obtained from the Kepler space mission after 44 days of operation. Comparison of the observed Ks vs. V-Ks diagram with a diagram based on the Besancon model shows significant effects of both distance and reddening in the investigated direction of the sky. We demonstrate that the best model indicates the presence of absorbing clouds at distances 11-13 kpc from the Sun in the minor Carina-Sagittarius Arm.