| Autor: |
M. E. Heiger, T. S. Li, A. B. Pace, J. D. Simon, A. P. Ji, A. Chiti, C. R. Bom, J. A. Carballo-Bello, J. L. Carlin, W. Cerny, Y. Choi, A. Drlica-Wagner, D. J. James, C. E. Martínez-Vázquez, G. E. Medina, B. Mutlu-Pakdil, M. Navabi, N. E. D. Noël, J. D. Sakowska, G. S. Stringfellow, (DELVE Collaboration) |
| Jazyk: |
angličtina |
| Rok vydání: |
2024 |
| Předmět: |
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| Zdroj: |
The Astrophysical Journal, Vol 961, Iss 2, p 234 (2024) |
| Druh dokumentu: |
article |
| ISSN: |
1538-4357 |
| DOI: |
10.3847/1538-4357/ad0cf7 |
| Popis: |
We present a spectroscopic analysis of Eridanus IV (Eri IV) and Centaurus I (Cen I), two ultrafaint dwarf galaxies of the Milky Way. Using IMACS/Magellan spectroscopy, we identify 28 member stars of Eri IV and 34 member stars of Cen I. For Eri IV, we measure a systemic velocity of ${v}_{\mathrm{sys}}=-{31.5}_{-1.2}^{+1.3}\ \mathrm{km}\,{{\rm{s}}}^{-1}$ , and velocity dispersion ${\sigma }_{v}={6.1}_{-0.9}^{+1.2}\ \mathrm{km}\,{{\rm{s}}}^{-1}$ . Additionally, we measure the metallicities of 16 member stars of Eri IV. We find a metallicity of $[\mathrm{Fe}/{\rm{H}}]=-{2.87}_{-0.07}^{+0.08}$ , and resolve a dispersion of σ _[Fe/H] =0.20 ± 0.09. The mean metallicity is marginally lower than all other known ultrafaint dwarf galaxies, making it one of the most metal-poor galaxies discovered thus far. Eri IV also has a somewhat unusual right-skewed metallicity distribution. For Cen I, we find a velocity v _sys = 44.9 ± 0.8 km s ^−1 , and velocity dispersion ${\sigma }_{v}={4.2}_{-0.5}^{+0.6}\ \mathrm{km}\,{{\rm{s}}}^{-1}$ . We measure the metallicities of 27 member stars of Cen I, and find a mean metallicity [Fe/H] = −2.57 ± 0.08, and metallicity dispersion ${\sigma }_{[\mathrm{Fe}/{\rm{H}}]}={0.38}_{-0.05}^{+0.07}$ . We calculate the systemic proper motion, orbit, and the astrophysical J-factor for each system, the latter of which indicates that Eri IV is a good target for indirect dark matter detection. We also find no strong evidence for tidal stripping of Cen I or Eri IV. Overall, our measurements confirm that Eri IV and Cen I are dark-matter-dominated galaxies with properties largely consistent with other known ultrafaint dwarf galaxies. The low metallicity, right-skewed metallicity distribution, and high J-factor make Eri IV an especially interesting candidate for further follow-up. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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