Work

Massive star population in the Sextans A dwarf galaxy from HST UV photometry

Year: 2026

Type: article

Abstract: ABSTRACT We build a catalogue of massive (M > 8 M$_\odot$) main-sequence stars in the metal-poor (${\sim} 0.1$ Z$_\odot$) dwarf irregular galaxy Sextans A. HST (Hubble Space Telescope) WFC3 (Wide Field Camera 3) ultraviolet (UV) photometry in the 275 and 336 nm wideband filters is arranged in a colour–magnitude diagram (CMD), and overlaid on top of stellar evolutionary tracks from the mist (mesa Isochrones and Stellar Tracks) library. The star properties (mass, age, etc.) are computed with a finite element (FE) interpolation of the stellar tracks. The FE method, originally developed to solve structural analysis problems, provides a general framework for interpolating fields inside domains of complex geometry. Besides the interpolated properties, the algorithm computes their gradients with respect to the photometry. These sensitivities yield a direct and efficient estimate of the associated uncertainties. Our catalogue contains 655 stars, with the most massive one estimated at $58\pm 11$ M$_\odot$. A comparison with a ground-based spectroscopic census of OB stars yields only eight matches, evidencing the minimal overlap between both data sets. The mass estimates derived from the UV CMD and the spectral classification are in good agreement for the majority of O-type stars found in both data sets. Our catalogue provides an extensive list of candidates for follow-up spectroscopic observation to improve our understanding of the early evolutionary stages of massive low-metallicity stars.

Source: Monthly Notices of the Royal Astronomical Society

DOI: 10.1093/mnras/stag635

Authors: Roberto Flores, E Fantino, G Battaglia, A Aparicio

Institutions: Khalifa University of Science and Technology, Universidad de La Laguna, Instituto de Astrofísica de Canarias

Language: English

Topic: Stellar, planetary, and galactic studies

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,046