Pisces VII / Triangulum III HST

Pisces VII / Triangulum III HST

Credit: NASA/ESA/Hubble, M.G. Jones, G. Donatiello

 

 

Pisces VII / Triangulum III: What could be more exciting than seeing an object you discovered imaged by the Hubble Space Telescope?

 

 

Pisces VII / Triangulum III is an ultra-faint dwarf (UFD) galaxy that I found in September 2020 while analyzing data from the DESI LIS, a survey that was not designed to search for satellite galaxies in the Andromeda system (M31), but for dark energy.

 

The study, using deep images taken by our Telescopio Nazionale Galileo (TNG), confirmed that the source was in the M31 subgroup and that, indeed, it could be a strong candidate for a satellite of Triangulum (M33), the LB dwarf spiral galaxy believed to be its largest satellite. In other words, it was a satellite of another satellite, flanking Andromeda XXII.

 

Data analysis led to an estimate of its distance at about 3 million light-years.

Thanks to new Hubble data, the distance has now been refined to 929 ±48 kpc, essentially the same distance already estimated with TNG data (Michael G. Jones et al. 2025).

 

Of the 11 dwarf spheroidal and UFD galaxies I've discovered so far, HST has observed five: Donatiello II, Donatiello III, Donatiello IV, Pisces VII, and Pegasus V (image coming soon).

 

 

References on Pisces VII:

David Martínez-Delgado et al., Monthly Notices of the Royal Astronomical Society, Volume 509, Issue 1, January 2022, Pages 16–24

Michelle L M Collins et al., Monthly Notices of the Royal Astronomical Society, Volume 528, Issue 2, February 2024, Pages 2614–2620

 

(My elaboration from the original FITS via MAST Archive)

Done