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12th of December 2022
by Karachentsev et al.
The HI Parkes All Sky Survey (HIPASS) survey was conducted with 20cm multi-beam receiver on the Parkes 64m telescope, Murriyang, in the late 1990s and early 2000s. HIPASS J1131–31 was discovered in that survey as a source of HI emission at low redshift, but in such close proximity to a bright star that optical follow-up observations were not possible at the time. However, the star turned out to be a fast-moving one, and with time it has moved far enough away from the line-of-sight to the galaxy that the galaxy can now be studied. Hubble Space Telescope images resolve the dwarf irregular galaxy into stars, leading to a distance estimate of 7 Mpc (23 million light years). Spectral optical observations with the Southern African Large Telescope reveal HIPASS J1131–31 to be one of the most extremely metal-poor galaxies known. Karachentsev et al. have dubbed it the Peekaboo galaxy because of the way it has been hiding and because of its potential importance. The red giant branch of the system is tenuous compared with the prominence of the features of young populations in the color-magnitude diagram, inviting speculation that star formation in the galaxy only began in the last few Gyr. The image above is an optical HST image of the dwarf galaxy HIPASS J1131–31, with dimensions of 70 arcseconds × 45 arcseconds. The 10.4 magnitude foreground star is located ∼15 arcsec to the North. The spikes of the HST's diffraction pattern, caused by light diffracting around the struts supporting the secondary mirror, are evident in the image. The results will be published in the Monthly Notices of the Royal Astronomical Society.

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