Skip to main content
OSTI.GOVU.S. Department of Energy Office of Scientific and Technical Information
U.S. Department of Energy
Office of Scientific and Technical Information
 

Eridanus III and DELVE 1: Carbon-rich Primordial Star Clusters or the Smallest Dwarf Galaxies?

Journal Article · · Astrophys.J.
 [1];  [2];  [3];  [4];  [5];  [6];  [7];  [8];  [9];  [10];  [11]
  1. Carnegie Inst. Observ.
  2. Toronto U., Astron. Dept.
  3. Chicago U.; Chicago U., KICP
  4. Carnegie Mellon U.
  5. Rome U.; Gran Sasso
  6. Yale U.
  7. Princeton U., Astrophys. Sci. Dept.; Carnegie Inst. Observ.
  8. Edinburgh U., Inst. Astron.; Cambridge U., Inst. of Astron.
  9. Fermilab; Chicago U., KICP; Chicago U.
  10. Stanford U.; KIPAC, Menlo Park
  11. Notre Dame U.
+ Show Author Affiliations
We present spectroscopy of the ultra-faint Milky Way satellites Eridanus III (Eri III) and DELVE 1. We identify eight member stars in each satellite and place non-constraining upper limits on their velocity and metallicity dispersions. The brightest star in each object is very metal-poor, at [Fe/H] = -3.1 for Eri III and [Fe/H] = -2.8 for DELVE 1. Both of these stars exhibit large overabundances of carbon and very low abundances of the neutron-capture elements Ba and Sr, and we classify them as CEMP-no stars. Because their metallicities are well below those of the Milky Way globular cluster population, and because no CEMP-no stars have been identified in globular clusters, these chemical abundances could suggest that Eri III and DELVE 1 are dwarf galaxies. On the other hand, the two systems have half-light radii of 8 pc and 6 pc, respectively, which is more compact than any known ultra-faint dwarfs. We conclude that Eri III and DELVE 1 are either the smallest dwarf galaxies yet discovered, or they are representatives of a new class of star clusters that underwent chemical evolution distinct from that of ordinary globular clusters. In the latter scenario, such objects are likely the most primordial star clusters surviving today. These possibilities can be distinguished by future measurements of carbon and/or iron abundances for larger samples of stars or improved stellar kinematics for the two systems.
Research Organization:
Cambridge U., Inst. of Astron.; Carnegie Inst. Observ.; Carnegie Mellon U.; Chicago U.; Chicago U., KICP; Edinburgh U., Inst. Astron.; Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Gran Sasso; Notre Dame U.; Princeton U., Astrophys. Sci. Dept.; Rome U.; SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Stanford U.; Toronto U., Astron. Dept.; Yale U.
Sponsoring Organization:
US Department of Energy
Grant/Contract Number:
89243024CSC000002; AC02-07CH11359
OSTI ID:
2563248
Report Number(s):
FERMILAB-PUB-24-1019-PPD; oai:inspirehep.net:2912582; arXiv:2410.08276
Journal Information:
Astrophys.J., Journal Name: Astrophys.J. Vol. 976
Country of Publication:
United States
Language:
English

Similar Records

Eridanus IV: an Ultra-faint Dwarf Galaxy Candidate Discovered in the DECam Local Volume Exploration Survey
Journal Article · Sun Oct 24 20:00:00 EDT 2021 · Astrophys.J.Lett. · OSTI ID:1824804
AN EXTREMELY CARBON-RICH, EXTREMELY METAL-POOR STAR IN THE SEGUE 1 SYSTEM
Journal Article · Sun Oct 10 00:00:00 EDT 2010 · Astrophysical Journal Letters · OSTI ID:21452746

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CEMP stars
Dwarf galaxies
Galaxy chemical evolution
Globular star clusters
Nucleosynthesis
R-process
Stellar abundances