2005/01/01 by A. W. McConnachie, Alan W. McConnachie, M. J. Irwin +7 · 16 citations
Physics and Astronomy · #Absolute magnitude #Andromeda #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Dwarf galaxy #Dwarf spheroidal galaxy #Elliptical galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy group #Interacting galaxy #Local Group #Metallicity #Milky Way #Photometry (optics) #Physics #Red-giant branch #Stars #Stellar, planetary, and galactic studies
paper · pdf · doi:10.1111/j.1365-2966.2004.08514.x
openalex publication_date 2005/01/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
We have obtained Johnson V and Gunn i photometry for a large number of Local Group galaxies using the Isaac Newton Telescope Wide Field Camera (INT WFC). The majority of these galaxies are members of the M31 subgroup and the observations are deep enough to study the top few magnitudes of the red giant branch in each system. We previously measured the location of the tip of the red giant branch (TRGB) for Andromeda I, Andromeda II and M33 to within systematic uncertainties of typically <0.05 mag. As the TRGB acts as a standard candle in old, metal-poor stellar populations, we were able to derive distances to each of these galaxies. Here we derive TRGB distances to the giant spiral galaxy M31 and 13 additional dwarf galaxies – NGC 205, 185, 147, Pegasus, WLM, LGS3, Cetus, Aquarius, And III, V, VI, VII and the newly discovered dwarf spheroidal And IX. The observations for each of the dwarf galaxies were intentionally taken in photometric conditions. In addition to the distances, we also self-consistently derive the median metallicity of each system from the colour of their red giant branches. This allows us to take into account the small metallicity variation of the absolute I magnitude of the TRGB. The homogeneous nature of our data and the identical analysis applied to each of the 17 Local Group galaxies ensures that these estimates form a reliable set of distance and metallicity determinations that are ideal for comparative studies of Local Group galaxy properties.