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 , and velocity dispersion . Additionally, we measure the metallicities of 16 member stars of Eri IV. We find a metallicity of , 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 . 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 . 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.
Heiger, M. E., et al. "Reading between the (Spectral) Lines: Magellan/IMACS Spectroscopy of the Ultrafaint Dwarf Galaxies Eridanus IV and Centaurus I." The Astrophysical Journal, vol. 961, no. 2, Jan. 2024. https://doi.org/10.3847/1538-4357/ad0cf7
Heiger, M. E., Li, T. S., Pace, A. B., Simon, J. D., Ji, A. P., Chiti, A., Bom, C. R., Carballo-Bello, J. A., Carlin, J. L., Cerny, W., Choi, Y., Drlica-Wagner, A., James, D. J., Martínez-Vázquez, C. E., Medina, G. E., Mutlu-Pakdil, B., Navabi, M., Noël, N. E. D., Sakowska, J. D., & Stringfellow, G. S. (2024). Reading between the (Spectral) Lines: Magellan/IMACS Spectroscopy of the Ultrafaint Dwarf Galaxies Eridanus IV and Centaurus I. The Astrophysical Journal, 961(2). https://doi.org/10.3847/1538-4357/ad0cf7
Heiger, M. E., Li, T. S., Pace, A. B., et al., "Reading between the (Spectral) Lines: Magellan/IMACS Spectroscopy of the Ultrafaint Dwarf Galaxies Eridanus IV and Centaurus I," The Astrophysical Journal 961, no. 2 (2024), https://doi.org/10.3847/1538-4357/ad0cf7
@article{osti_2283259,
author = {Heiger, M. E. and Li, T. S. and Pace, A. B. and Simon, J. D. and Ji, A. P. and Chiti, A. and Bom, C. R. and Carballo-Bello, J. A. and Carlin, J. L. and Cerny, W. and others},
title = {Reading between the (Spectral) Lines: Magellan/IMACS Spectroscopy of the Ultrafaint Dwarf Galaxies Eridanus IV and Centaurus I},
annote = {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. },
doi = {10.3847/1538-4357/ad0cf7},
url = {https://www.osti.gov/biblio/2283259},
journal = {The Astrophysical Journal},
issn = {ISSN 0004-637X},
number = {2},
volume = {961},
place = {United States},
publisher = {American Astronomical Society},
year = {2024},
month = {01}}