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Reading between the (Spectral) Lines: Magellan/IMACS Spectroscopy of the Ultrafaint Dwarf Galaxies Eridanus IV and Centaurus I

2024; IOP Publishing; Volume: 961; Issue: 2 Linguagem: Inglês

10.3847/1538-4357/ad0cf7

ISSN

1538-4357

Autores

Mairead Heiger, Ting S. Li, Andrew B. Pace, Joshua D. Simon, Alexander P. Ji, Anirudh Chiti, C. R. Bom, J. A. Carballo-Bello, Jeffrey L. Carlin, W. Cerny, Yumi Choi, A. Drlica-Wagner, D. J. James, C. E. Martínez-Vázquez, G. E. Medina, Burçı̇n Mutlu-Pakdı̇l, Mahdieh Navabi, N. E. D. Noël, J. D. Sakowska, Guy S. Stringfellow,

Tópico(s)

Gamma-ray bursts and supernovae

Resumo

Abstract 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 sys = − 31.5 − 1.2 + 1.3 km s − 1 , and velocity dispersion σ v = 6.1 − 0.9 + 1.2 km s − 1 . Additionally, we measure the metallicities of 16 member stars of Eri IV. We find a metallicity of [ Fe / 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 σ v = 4.2 − 0.5 + 0.6 km 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 σ [ Fe / 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.

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