Pegasus IV: Discovery and Spectroscopic Confirmation of an Ultra-faint Dwarf Galaxy in the Constellation Pegasus

被引：27

作者：

Cerny, W. ^{[1
,2
]}

Simon, J. D. ^{[3
]}

Li, T. S. ^{[4
]}

Drlica-Wagner, A. ^{[1
,2
,5
]}

Pace, A. B. ^{[6
]}

Martinez-Vazquez, C. E. ^{[7
,8
]}

Riley, A. H. ^{[9
,10
]}

Mutlu-Pakdil, B. ^{[1
,2
]}

Mau, S. ^{[11
,12
]}

Ferguson, P. S. ^{[13
]}

Erkal, D. ^{[14
]}

Munoz, R. R. ^{[15
]}

Bom, C. R. ^{[16
]}

Carlin, J. L. ^{[17
]}

Carollo, D. ^{[18
]}

Choi, Y. ^{[19
]}

Ji, A. P. ^{[1
,2
]}

Manwadkar, V. ^{[2
]}

Martinez-Delgado, D. ^{[20
]}

Miller, A. E. ^{[21
,22
]}

Noel, N. E. D. ^{[14
]}

Sakowska, J. D. ^{[14
]}

Sand, D. J. ^{[23
]}

Stringfellow, G. S. ^{[24
]}

Tollerud, E. J. ^{[19
]}

Vivas, A. K. ^{[8
]}

Carballo-Bello, J. A. ^{[25
]}

Hernandez-Lang, D. ^{[26
]}

James, D. J. ^{[27
]}

Nidever, D. L. ^{[28
,29
]}

Castellon, J. L. Nilo ^{[30
,31
]}

Olsen, K. A. G. ^{[29
]}

Zenteno, A. ^{[8
]}

机构：

[1] Univ Chicago, Kavli Inst Cosmol Phys, Chicago, IL 60637 USA

[2] Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA

[3] Observ Carnegie Inst Sci, 813 St Barbara St, Pasadena, CA 91101 USA

[4] Univ Toronto, Dept Astron & Astrophys, 50 St George St, Toronto, ON M5S 3H4, Canada

[5] Fermilab Natl Accelerator Lab, PO, Box 500, Batavia, IL 60510 USA

[6] Carnegie Mellon Univ, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USA

[7] Gemini Observ, NSF NOIRLab, 670 North Aohoku Pl, Hilo, HI 96720 USA

[8] NSF Natl Opt Infrared Astron Res Lab, Cerro Tololo Interamer Observ, Casilla 603, La Serena, Chile

[9] Texas A&M Univ, George P & Cynthia Woods Mitchell Inst Fundamental, College Stn, TX 77843 USA

[10] Texas A&M Univ, Dept Phys & Astron, College Stn, TX 77843 USA

[11] Stanford Univ, Dept Phys, 382 Via Pueblo Mall, Stanford, CA 94305 USA

[12] Stanford Univ, Kavli Inst Particle Astrophys & Cosmol, POB 2450, Stanford, CA 94305 USA

[13] Univ Wisconsin Madison, Dept Phys, Madison, WI 53706 USA

[14] Univ Surrey, Dept Phys, Guildford GU2 7XH, England

[15] Univ Chile, Dept Astron, Camino Observ 1515, Santiago, Chile

[16] Ctr Brasileiro Pesquisas Fis, Rua Doutor Xavier Sigaud 150, BR-22290180 Rio De Janeiro, RJ, Brazil

[17] AURA, Rubin Observ, 950 North Cherry Ave, Tucson, AZ 85719 USA

[18] INAF Osservatorio Astron Trieste, I-34143 Trieste, Italy

[19] Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA

[20] CSIC, Inst Astrofis Andalucia, E-18080 Granada, Spain

[21] Leibniz Inst Astrophys Potsdam AIP, Sternwarte 16, D-14482 Potsdam, Germany

[22] Univ Potsdam, Inst Phys & Astron, Haus 28,Karl Liebknecht Str 24, D-14476 Potsdam, Germany

[23] Steward Observ, Dept Astron, 933 North Cherry Ave,Room N204, Tucson, AZ 85721 USA

[24] Univ Colorado, Ctr Astrophys & Space Astron, 389 UCB, Boulder, CO 80309 USA

[25] Univ Tarapaca, Inst Alta Invest, Sede Esmeralda, Ave Luis Emilio Recabarren 2477, Iquique, Chile

[26] Ludwig Maximilians Univ Munchen, Scheinerstr 1, Munich, Germany

[27] ASTRAVEO LLC, POB 1668, Gloucester, MA 01931 USA

[28] Montana State Univ, Dept Phys, POB 173840, Bozeman, MT 59717 USA

[29] NSFss Natl Opt Infrared Astron Res Lab, 950 North Cherry Ave, Tucson, AZ 85719 USA

[30] Univ Serena, Dept Astron, Ave Juan Cisternas 1200, La Serena, Chile

[31] Univ Serena, Direcc Invest & Desarrollo, Ave Raul Bitran Nachary 1305, La Serena, Chile

来源：

ASTROPHYSICAL JOURNAL | 2023年 / 942卷 / 02期

基金：

美国国家科学基金会;

关键词：

MILKY-WAY SATELLITE; RR LYRAE STARS; LARGE-MAGELLANIC-CLOUD; EXPLORING HALO SUBSTRUCTURE; DARK-MATTER ANNIHILATION; METAL-POOR STARS; PROPER MOTIONS; GLOBULAR-CLUSTERS; MASS-DISTRIBUTION; GIANT STARS;

D O I：

10.3847/1538-4357/aca1c3

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

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) kpc. Based on spectra of seven nonvariable member stars observed with Magellan/IMACS, we confidently resolve Pegasus IV's velocity dispersion, measuring s = sigma(v) 3.3(-1.1)(+1.7) km s(-1) (after excluding three velocity outliers); this implies a mass-to-light ratio of M1/2LV ,(1/2)=167(-99)(+224) M-?/L-? 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 (mu(alpha*, mu delta)) = (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.

引用

页数：18

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