Academic Journal
Pegasus IV: Discovery and Spectroscopic Confirmation of an Ultra-faint Dwarf Galaxy in the Constellation Pegasus
| العنوان: | Pegasus IV: Discovery and Spectroscopic Confirmation of an Ultra-faint Dwarf Galaxy in the Constellation Pegasus |
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| المؤلفون: | W. Cerny, J. D. Simon, T. S. Li, A. Drlica-Wagner, A. B. Pace, C. E. Martínez-Vázquez, A. H. Riley, B. Mutlu-Pakdil, S. Mau, P. S. Ferguson, D. Erkal, R. R. Munoz, C. R. Bom, J. L. Carlin, D. Carollo, Y. Choi, A. P. Ji, V. Manwadkar, D. Martínez-Delgado, A. E. Miller, N. E. D. Noël, J. D. Sakowska, D. J. Sand, G. S. Stringfellow, E. J. Tollerud, A. K. Vivas, J. A. Carballo-Bello, D. Hernandez-Lang, D. J. James, D. L. Nidever, J. L. Nilo Castellon, K. A. G. Olsen, A. Zenteno, DELVE Collaboration |
| المصدر: | The Astrophysical Journal, Vol 942, Iss 2, p 111 (2023) |
| بيانات النشر: | IOP Publishing |
| سنة النشر: | 2023 |
| المجموعة: | Directory of Open Access Journals: DOAJ Articles |
| مصطلحات موضوعية: | Galactic archaeology, RR Lyrae variable stars, Dark matter, Dwarf galaxies, Spectroscopy, Sky surveys, Astrophysics, QB460-466 |
| الوصف: | We report the discovery of Pegasus IV, an ultra-faint dwarf galaxy found in archival data from the Dark Energy Camera processed by the DECam Local Volume Exploration Survey. Pegasus IV is a compact, ultra-faint stellar system ( ${r}_{1/2}={41}_{-6}^{+8}$ pc; M _V = −4.25 ± 0.2 mag) located at a heliocentric distance of ${90}_{-6}^{+4}\,\mathrm{kpc}$ . Based on spectra of seven nonvariable member stars observed with Magellan/IMACS, we confidently resolve Pegasus IV’s velocity dispersion, measuring ${\sigma }_{v}={3.3}_{-1.1}^{+1.7}$ km s ^−1 (after excluding three velocity outliers); this implies a mass-to-light ratio of ${M}_{1/2}/{L}_{V,1/2}={167}_{-99}^{+224}{M}_{\odot }/{L}_{\odot }$ for the system. From the five stars with the highest signal-to-noise spectra, we also measure a systemic metallicity of [Fe/H] = $-{2.63}_{-0.30}^{+0.26}$ dex, making Pegasus IV one of the most metal-poor ultra-faint dwarfs. We tentatively resolve a nonzero metallicity dispersion for the system. These measurements provide strong evidence that Pegasus IV is a dark-matter-dominated dwarf galaxy, rather than a star cluster. We measure Pegasus IV’s proper motion using data from Gaia Early Data Release 3, finding ( μ _α _* , μ _δ ) = (0.33 ± 0.07, −0.21 ± 0.08) mas yr ^−1 . When combined with our measured systemic velocity, this proper motion suggests that Pegasus IV is on an elliptical, retrograde orbit, and is currently near its orbital apocenter. Lastly, we identify three potential RR Lyrae variable stars within Pegasus IV, including one candidate member located more than 10 half-light radii away from the system’s centroid. The discovery of yet another ultra-faint dwarf galaxy strongly suggests that the census of Milky Way satellites is still incomplete, even within 100 kpc. |
| نوع الوثيقة: | article in journal/newspaper |
| اللغة: | English |
| تدمد: | 1538-4357 |
| Relation: | https://doi.org/10.3847/1538-4357/aca1c3; https://doaj.org/toc/1538-4357; https://doaj.org/article/cedd560cef764487aed65e31e7cd2b2c |
| DOI: | 10.3847/1538-4357/aca1c3 |
| الاتاحة: | https://doi.org/10.3847/1538-4357/aca1c3 https://doaj.org/article/cedd560cef764487aed65e31e7cd2b2c |
| رقم الانضمام: | edsbas.E9FB7583 |
| قاعدة البيانات: | BASE |
Full Text Finder | تدمد: | 15384357 |
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| DOI: | 10.3847/1538-4357/aca1c3 |