Unveiling VVV/WISE Mira variables on the far side of the Galactic disk: Distances, kinematics and a new extinction law

• Main Authors: Albarracín, Rogelio, Zoccali, M, Carvajal, J. Olivares, Rojas-Arriagada, Á, Minniti, J. H, Catelan, M, De Leo, M, Gran, F, Ramos, R. Contreras, Navarro, Á. Valenzuela, Salvo-Guajardo, C
• Format: Journal Article
• Language: English
• Published: 07-11-2024
• Subjects: Physics - Astrophysics of Galaxies
• DOI: 10.48550/arxiv.2411.04623

The structure and kinematics of the Milky Way disk are largely inferred from
the solar vicinity. To gain a comprehensive understanding, it is essential to
find reliable tracers in less-explored regions like the bulge and the far side
of the disk. Mira variables, which are well-studied and bright standard
candles, offer an excellent opportunity to trace intermediate and old
populations in these complex regions. We aim to isolate a clean sample of Miras
in the Vista Variables in the V\'ia L\'actea survey using Gaussian process
algorithms. This sample will be used to study intermediate and old age
populations in the Galactic bulge and far disk. Near- and mid-infrared
time-series photometry were processed using Gaussian Process algorithms to
identify Mira variables and model their light curves. We calibrated selection
criteria with a visually inspected sample to create a high-purity sample of
Miras, integrating multi-band photometry and kinematic data from proper
motions. We present a catalog of 3602 Mira variables. By analyzing photometry,
we classify them by O-rich or C-rich surface chemistry and derive
selective-to-total extinction ratios of $A_{K_{s}}/E(J - K_{s}) = 0.471 \pm
0.01$ and $A_{K_{s}}/E(H - K_{s}) = 1.320 \pm 0.020$. Using the Mira period-age
relation, we find evidence supporting the inside-out formation of the Milky Way
disk. The distribution of proper motions and distances aligns with the Galactic
rotation curve and disk kinematics. We extend the rotation curve up to R$_{\rm
GC} \sim 17 \ \rm{kpc}$ and find no strong evidence of the nuclear stellar disk
in our Mira sample. This study constitutes the largest catalog of variable
stars on the far side of the Galactic disk to date.