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Stellar Kinematics and Metallicities in the Ultra-Faint Dwarf Galaxy Reticulum II | | J. D. Simon
; A. Drlica-Wagner
; T. S. Li
; B. Nord
; M. Geha
; K. Bechtol
; E. Balbinot
; E. Buckley-Geer
; H. Lin
; J. Marshall
; B. Santiago
; L. Strigari
; M. Wang
; R. H. Wechsler
; B. Yanny
; T. Abbott
; A. H. Bauer
; G. M. Bernstein
; E. Bertin
; D. Brooks
; D. L. Burke
; D. Capozzi
; A. Carnero Rosell
; M. Carrasco Kind
; C. B. D'Andrea
; L. N. da Costa
; D. L. DePoy
; S. Desai
; H. T. Diehl
; S. Dodelson
; C. E Cunha
; J. Estrada
; A. E. Evrard
; A. Fausti Neto
; E. Fernandez
; D. A. Finley
; B. Flaugher
; J. Frieman
; E. Gaztanaga
; D. Gerdes
; D. Gruen
; R. A. Gruendl
; K. Honscheid
; D. James
; K. Kuehn
; N. Kuropatkin
; O. Lahav
; M. A. G. Maia
; M. March
; P. Martini
; C. J. Miller
; R. Miquel
; R. Ogando
; A. K. Romer
; A. Roodman
; E. S. Rykoff
; M. Sako
; E. Sanchez
; M. Schubnell
; I. Sevilla
; R. C. Smith
; M. Soares-Santos
; F. Sobreira
; E. Suchyta
; M. E. C. Swanson
; G. Tarle
; J. Thaler
; D. Tucker
; V. Vikram
; A. R. Walker
; W. Wester
; | | Date: |
11 Apr 2015 | | Abstract: | We present Magellan/M2FS, VLT/GIRAFFE, and Gemini South/GMOS spectroscopy of
the newly discovered Milky Way satellite Reticulum II. Based on the spectra of
25 Ret II member stars selected from Dark Energy Survey imaging, we measure a
mean heliocentric velocity of 62.8 +/- 0.5 km/s and a velocity dispersion of
3.3 +/- 0.7 km/s. The mass-to-light ratio of Ret II within its half-light
radius is 470 +/- 210 Msun/Lsun, demonstrating that it is a strongly dark
matter-dominated system. Despite its spatial proximity to the Magellanic
Clouds, the radial velocity of Ret II differs from that of the LMC and SMC by
199 and 83 km/s, respectively, suggesting that it is not gravitationally bound
to the Magellanic system. The likely member stars of Ret II span 1.3 dex in
metallicity, with a dispersion of 0.28 +/- 0.09 dex, and we identify several
extremely metal-poor stars with [Fe/H] < -3. In combination with its
luminosity, size, and ellipticity, these results confirm that Ret II is an
ultra-faint dwarf galaxy. With a mean metallicity of [Fe/H] = -2.65 +/- 0.07,
Ret II matches Segue~1 as the most metal-poor galaxy known. Although Ret II is
the third-closest dwarf galaxy to the Milky Way, the line-of-sight integral of
the dark matter density squared is log J = 18.8 +/- 0.6 Gev^2/cm^5 within 0.2
degrees, indicating that the predicted gamma-ray flux from dark matter
annihilation in Ret II is lower than that of several other dwarf galaxies. | | Source: | arXiv, 1504.2889 | | Services: | Forum | Review | PDF | Favorites | |
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