Faint galaxies in the Zone of Avoidance revealed by JWST/NIRCam

¹ Departamento Astronomía, Facultad de Ciencias, Universidad de La Serena. Av. Raul Bitran 1305, La Serena, Chile
² Instituto de Astronomía Teórica y Experimental, (IATE, CONICET, UNC), Laprida 854, X5000BGR Córdoba, Argentina
³ Observatorio Astronómico de Córdoba, Universidad Nacional de Córdoba, Laprida 854, X5000BGR Córdoba, Argentina
⁴ Instituto de Investigación en Astronomía y Ciencias Planetarias, Universidad de Atacama, Av. Copayapu 485, Copiapó, Chile
⁵ Instituto de Astrofísica, Facultad de Ciencias Exactas, Universidad Andrés Bello, Av. Fernandez Concha 700, Las Condes, Santiago, Chile
⁶ Vatican Observatory, V00120 Vatican City State, Italy
⁷ Center for Space Science and Technology, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
⁸ Center for Research and Exploration in Space Science and Technology, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁹ Centro de Astronomía (CITEVA), Universidad de Antofagasta, Av. Angamos 601, Antofagasta, Chile
¹⁰ Steward Observatory, University of Arizona 933N Cherry Avenue, Tucson, AZ 85751, USA
¹¹ Instituto de Altos Estudios Espaciales “Mario Gulich” (CONAE – UNC), Falda de Cañete, Argentina

^★ Corresponding author: jnilo@userena.cl

Received: 31 July 2025
Accepted: 13 October 2025

Abstract

Context. The Zone of Avoidance (ZoA) remains one of the last frontiers in constructing a comprehensive three-dimensional map of the Universe. Galactic extinction, stellar crowding, and confusion noise have historically limited the detection of background galaxies in these regions, with implications for large-scale structure and cosmological measurements.

Aims. We assess the capability of the James Webb Space Telescope (JWST) Near Infrared Camera (NIRCam) to detect extragalactic sources in a heavily contaminated region of the Milky Way.

Methods. We analyzed JWST/NIRCam wide-filter images of NGC 3324 with a customized implementation of SExtractor v2.28. Sources were detected in the F444W band, cross-matched with F090W and F200W, and validated against recent DAOPHOT point spread function photometry. A refined sample was obtained using full width at half maximum (FWHM)–signal-to-noise ratio criteria and visual inspection.

Results. We identified 102 galaxies across the JWST/NIRCam field of view. The magnitude (F444W) distribution is bimodal, with ∼10% brighter than m_F444W < 15 mag and ∼60% in the range 17 < m_F444W < 19 mag. Typical sizes are FWHM ≈ 6.5″, from compact to extended systems with isophotal areas of up to ∼2000 pixels (∼7.9 arcsec²). Morphologies span from compact to spiral and lenticular systems, including a compact group at the eastern edge of the field. We also report the detection of transnebular galaxies, visible through the most opaque regions of the molecular cloud.

Conclusions. These results demonstrate the potential of JWST/NIRCam to probe extragalactic sources through highly obscured Galactic regions, opening new avenues for mapping large-scale structures across the ZoA.