A near-infrared stellar atlas of the Galactic plane from the VVVX survey

TL;DR

This work delivers a near-infrared stellar atlas of the Galactic plane and outer bulge from the VVVX survey, addressing severe optical extinction by leveraging PSF photometry in the J, H, and K_s bands. By expanding the VVV footprint to ~1700 deg^2 and combining with the original VVV data, the authors produce a deep catalog of over 1.5 billion sources, including more than 700 million newly imaged sources in the VVVX regions. They detail DoPHOT-based PSF photometry, astrometric/photometric calibrations, and multi-epoch, multi-band merging to generate a high-quality JHK_s catalog (vvvxPsfDophotJHKsSource) publicly available via the VISTA Science Archive; density maps and CMDs reveal Galactic structure, extinction patterns, and features such as the Carina arm tangency and Sagittarius stream, as well as numerous clusters. The atlas enhances studies of the Galactic disk and bulge, supports future surveys (Rubin, Roman) and spectroscopic campaigns (VVVX-GalCen), and provides a valuable resource for identifying low-extinction windows and stellar populations in crowded, highly reddened regions.

Abstract

The VISTA Variables in the Via Lactea eXtended (VVVX) ESO public survey observed the Galactic plane and the outer Galactic bulge in the near-infrared to mitigate the effects of extinction that severely limit optical observations of these regions. By significantly expanding the area covered by the original VVV survey, VVVX enables a deeper and broader exploration of the most obscured and crowded regions of the Milky Way. We aim to extend and complete our photometric catalogs of the entire Galactic plane region accessible from the southern hemisphere, focusing on the areas newly covered by the VVVX survey. Building on previous work, we applied point-spread function fitting techniques to detect point sources and extract their deep J, H, and Ks photometry across the VVVX footprint. The resulting catalogs were calibrated using astrometric and photometric reference data. Cross-matching between filters and epochs was used to ensure a high level of reliability and completeness. We produce a deep, highly complete near-infrared catalog of more than 700 million sources in the Galactic plane and outer Galactic bulge. When combined with our previous VVV atlas, the full catalog includes over 1.5 billion sources. The derived density maps and color-magnitude diagrams enable detailed studies of Galactic structure, extinction, and stellar populations, and highlight features such as the Carina arm tangency, the Sagittarius stream, and numerous star clusters. This extended atlas provides an unprecedented view of the innermost regions of the Milky Way. It is now publicly available through the VISTA Science Archive, offering a valuable resource for the astronomical community to investigate the structure and evolution of the Galactic disk and bulge.

Figures (9)

• Figure 1: Footprint of the VVVX survey. The original VVV area, analyzed in alo18, is shown in gray. The extended region newly covered by VVVX is shown in green. Selected fields used for the completeness tests described in Sect. \ref{['sec_psf']} are marked in red.
• Figure 2: Seeing (left) and ellipticity (right) of the sources in the VVVX images used to construct our PSF near-infrared atlas. $J$-band images are shown in blue, $H$-band in green, and $K_s$-band in red.
• Figure 3: Completeness profiles for representative fields in the VVVX outermost bulge (left), the VVVX disk outside the Galactic plane (middle), and the VVVX disk near the Galactic plane (right). $J$-band results are shown in blue, $H$-band in green, and $K_s$-band in red.
• Figure 4: Ratio of the number of detected sources as a function of magnitude between our PSF photometry and CASU aperture photometry catalogs, for representative fields in the VVVX outermost bulge (left), the VVVX disk outside the Galactic plane (middle), and the VVVX disk close to the Galactic plane (right). $J$-band results are shown in blue, and $K_s$-band in red.
• Figure 5: Near-infrared CMDs of selected regions in the outer Galactic bulge within the VVVX footprint. Darker colors indicate higher source densities. Each field corresponds to a circular region within $r<15^\prime$ of the coordinates shown above the panels.