A Corotating Group of Dwarf Galaxies around NGC 2750 as a Centaurus A Analog

Sanjaya Paudel, Suk Jin Yoon, Rory Smith

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3 Citations (Scopus)


We study a low-mass spiral galaxy NGC 2750 (∼5 times less massive than the Milky Way), located ∼40 Mpc away in a sparse region that hosts seven satellite galaxies within a projected distance of 150 Kpc. Among them six are star-forming dwarfs with stellar masses of >≈107 M o˙ and one is an early-type dwarf with a stellar mass of 2.6 106 M o˙. The star-forming dwarfs are gas rich, with gas mass fractions as high as Log(M H i /M ∗) = 1.2 and their star formation rates vary between 0.03 and 0.35 M o˙ yr-1. The projected distances and measured radial velocities of the six star-forming satellites provide a high probability that they are members of the group. The radial velocity distribution of the six satellites exhibits evidence of a systematic corotation. We devise a method to quantify such a corotation signal by calculating the correlation coefficient between satellites' relative line-of-sight velocities (ΔV r) and their sky-projected distances from the host (R p). For the NGC 2750 system, we show a clear correlation between ΔV r and R p, with a Pearson's R correlation coefficient c = 0.90 and p-value = 0.005. We compare the NGC 2750 system with the Centaurus A (NGC 5128) system, a previously known corotating group, and conclude that the former could be a small version of the latter but is located in an isolated field, away from the influence of the large-scale structure. The results open up opportunities to explore the galactic anisotropy phenomenon on a low-mass scale and in a rarified environment.

Original languageEnglish
Article numberL18
JournalAstrophysical Journal Letters
Issue number2
Publication statusPublished - 2021 Aug 20

Bibliographical note

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© 2021. The American Astronomical Society. All rights reserved..

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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