Nearest Neighbor: The Low-mass Milky Way Satellite Tucana III

J. D. Simon; T. S. Li; A. Drlica-Wagner; K. Bechtol; J. L. Marshall; D. J. James; M. Y. Wang; L. Strigari; E. Balbinot; K. Kuehn; A. R. Walker; T. M.C. Abbott; S. Allam; J. Annis; A. Benoit-Lévy; D. Brooks; E. Buckley-Geer; D. L. Burke; A. Carnero Rosell; M. Carrasco Kind; J. Carretero; C. E. Cunha; C. B. D'Andrea; L. N.Da Costa; D. L. Depoy; S. Desai; P. Doel; E. Fernandez; B. Flaugher; J. Frieman; J. García-Bellido; E. Gaztanaga; D. A. Goldstein; D. Gruen; G. Gutierrez; N. Kuropatkin; M. A.G. Maia; P. Martini; F. Menanteau; C. J. Miller; R. Miquel; E. Neilsen; B. Nord; R. Ogando; A. A. Plazas; A. K. Romer; E. S. Rykoff; E. Sanchez; B. Santiago; V. Scarpine; M. Schubnell; I. Sevilla-Noarbe; R. C. Smith; F. Sobreira; E. Suchyta; M. E.C. Swanson; G. Tarle; L. Whiteway; B. Yanny

doi:10.3847/1538-4357/aa5be7

Nearest Neighbor: The Low-mass Milky Way Satellite Tucana III

J. D. Simon, T. S. Li, A. Drlica-Wagner, K. Bechtol, J. L. Marshall, D. J. James, M. Y. Wang, L. Strigari, E. Balbinot, K. Kuehn, A. R. Walker, T. M.C. Abbott, S. Allam, J. Annis, A. Benoit-Lévy, D. Brooks, E. Buckley-Geer, D. L. Burke, A. Carnero Rosell, M. Carrasco KindJ. Carretero, C. E. Cunha, C. B. D'Andrea, L. N.Da Costa, D. L. Depoy, S. Desai, P. Doel, E. Fernandez, B. Flaugher, J. Frieman, J. García-Bellido, E. Gaztanaga, D. A. Goldstein, D. Gruen, G. Gutierrez, N. Kuropatkin, M. A.G. Maia, P. Martini, F. Menanteau, C. J. Miller, R. Miquel, E. Neilsen, B. Nord, R. Ogando, A. A. Plazas, A. K. Romer, E. S. Rykoff, E. Sanchez, B. Santiago, V. Scarpine, M. Schubnell, I. Sevilla-Noarbe, R. C. Smith, F. Sobreira, E. Suchyta, M. E.C. Swanson, G. Tarle, L. Whiteway, B. Yanny

Department of Physics

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Abstract

© 2017. The American Astronomical Society. All rights reserved. We present Magellan/IMACS spectroscopy of the recently discovered Milky Way satellite Tucana III (Tuc III). We identify 26 member stars in Tuc III from which we measure a mean radial velocity of v hel = -102.3 ±0.4 (stat.) ±2.0 (sys.)km s-1, a velocity dispersion of 0.1+0.7-0.1 km s-1, and a mean metallicity of (Fe/H)= -2.42+0.07-0.08. The upper limit on the velocity dispersion is σ < 1.5 at 95.5% confidence, and the corresponding upper limit on the mass within the half-light radius of Tuc III is 9.0 × 104 M o. We cannot rule out mass-to-light ratios as large as 240 M oL/o for Tuc III, but much lower mass-to-light ratios that would leave the system baryon-dominated are also allowed. We measure an upper limit on the metallicity spread of the stars in Tuc III of 0.19 dex at 95.5% confidence. Tuc III has a smaller metallicity dispersion and likely a smaller velocity dispersion than any known dwarf galaxy, but a larger size and lower surface brightness than any known globular cluster. Its metallicity is also much lower than those of the clusters with similar luminosity. We therefore tentatively suggest that Tuc III is the tidally stripped remnant of a dark matter-dominated dwarf galaxy, but additional precise velocity and metallicity measurements will be necessary for a definitive classification. If Tuc III is indeed a dwarf galaxy, it is one of the closest external galaxies to the Sun. Because of its proximity, the most luminous stars in Tuc III are quite bright, including one star at V = 15.7 that is the brightest known member star of an ultra-faint satellite.

Original language	English
Article number	11
Journal	Astrophysical Journal
Volume	838
Issue number	1
DOIs	https://doi.org/10.3847/1538-4357/aa5be7
Publication status	Published - 20 Mar 2017

Keywords

dark matter
galaxies: dwarf
galaxies: individual (Tucana III)
galaxies: stellar content
Local Group
stars: abundances

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10.3847/1538-4357/aa5be7

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Simon, J. D., Li, T. S., Drlica-Wagner, A., Bechtol, K., Marshall, J. L., James, D. J., Wang, M. Y., Strigari, L., Balbinot, E., Kuehn, K., Walker, A. R., Abbott, T. M. C., Allam, S., Annis, J., Benoit-Lévy, A., Brooks, D., Buckley-Geer, E., Burke, D. L., Rosell, A. C., ... Yanny, B. (2017). Nearest Neighbor: The Low-mass Milky Way Satellite Tucana III. Astrophysical Journal, 838(1), [11]. https://doi.org/10.3847/1538-4357/aa5be7

@article{c26f2f72fa1c4097bc55601d20fbe063,

title = "Nearest Neighbor: The Low-mass Milky Way Satellite Tucana III",

abstract = "{\textcopyright} 2017. The American Astronomical Society. All rights reserved. We present Magellan/IMACS spectroscopy of the recently discovered Milky Way satellite Tucana III (Tuc III). We identify 26 member stars in Tuc III from which we measure a mean radial velocity of v hel = -102.3 ±0.4 (stat.) ±2.0 (sys.)km s-1, a velocity dispersion of 0.1+0.7-0.1 km s-1, and a mean metallicity of (Fe/H)= -2.42+0.07-0.08. The upper limit on the velocity dispersion is σ < 1.5 at 95.5% confidence, and the corresponding upper limit on the mass within the half-light radius of Tuc III is 9.0 × 104 M o. We cannot rule out mass-to-light ratios as large as 240 M oL/o for Tuc III, but much lower mass-to-light ratios that would leave the system baryon-dominated are also allowed. We measure an upper limit on the metallicity spread of the stars in Tuc III of 0.19 dex at 95.5% confidence. Tuc III has a smaller metallicity dispersion and likely a smaller velocity dispersion than any known dwarf galaxy, but a larger size and lower surface brightness than any known globular cluster. Its metallicity is also much lower than those of the clusters with similar luminosity. We therefore tentatively suggest that Tuc III is the tidally stripped remnant of a dark matter-dominated dwarf galaxy, but additional precise velocity and metallicity measurements will be necessary for a definitive classification. If Tuc III is indeed a dwarf galaxy, it is one of the closest external galaxies to the Sun. Because of its proximity, the most luminous stars in Tuc III are quite bright, including one star at V = 15.7 that is the brightest known member star of an ultra-faint satellite.",

keywords = "dark matter, galaxies: dwarf, galaxies: individual (Tucana III), galaxies: stellar content, Local Group, stars: abundances",

author = "Simon, {J. D.} and Li, {T. S.} and A. Drlica-Wagner and K. Bechtol and Marshall, {J. L.} and James, {D. J.} and Wang, {M. Y.} and L. Strigari and E. Balbinot and K. Kuehn and Walker, {A. R.} and Abbott, {T. M.C.} and S. Allam and J. Annis and A. Benoit-L{\'e}vy and D. Brooks and E. Buckley-Geer and Burke, {D. L.} and Rosell, {A. Carnero} and Kind, {M. Carrasco} and J. Carretero and Cunha, {C. E.} and D'Andrea, {C. B.} and Costa, {L. N.Da} and Depoy, {D. L.} and S. Desai and P. Doel and E. Fernandez and B. Flaugher and J. Frieman and J. Garc{\'i}a-Bellido and E. Gaztanaga and Goldstein, {D. A.} and D. Gruen and G. Gutierrez and N. Kuropatkin and Maia, {M. A.G.} and P. Martini and F. Menanteau and Miller, {C. J.} and R. Miquel and E. Neilsen and B. Nord and R. Ogando and Plazas, {A. A.} and Romer, {A. K.} and Rykoff, {E. S.} and E. Sanchez and B. Santiago and V. Scarpine and M. Schubnell and I. Sevilla-Noarbe and Smith, {R. C.} and F. Sobreira and E. Suchyta and Swanson, {M. E.C.} and G. Tarle and L. Whiteway and B. Yanny",

year = "2017",

month = mar,

day = "20",

doi = "10.3847/1538-4357/aa5be7",

language = "English",

volume = "838",

journal = "Astrophysical Journal",

issn = "0004-637X",

number = "1",

}

Simon, JD, Li, TS, Drlica-Wagner, A, Bechtol, K, Marshall, JL, James, DJ, Wang, MY, Strigari, L, Balbinot, E, Kuehn, K, Walker, AR, Abbott, TMC, Allam, S, Annis, J, Benoit-Lévy, A, Brooks, D, Buckley-Geer, E, Burke, DL, Rosell, AC, Kind, MC, Carretero, J, Cunha, CE, D'Andrea, CB, Costa, LND, Depoy, DL, Desai, S, Doel, P, Fernandez, E, Flaugher, B, Frieman, J, García-Bellido, J, Gaztanaga, E, Goldstein, DA, Gruen, D, Gutierrez, G, Kuropatkin, N, Maia, MAG, Martini, P, Menanteau, F, Miller, CJ, Miquel, R, Neilsen, E, Nord, B, Ogando, R, Plazas, AA, Romer, AK, Rykoff, ES, Sanchez, E, Santiago, B, Scarpine, V, Schubnell, M, Sevilla-Noarbe, I, Smith, RC, Sobreira, F, Suchyta, E, Swanson, MEC, Tarle, G, Whiteway, L & Yanny, B 2017, 'Nearest Neighbor: The Low-mass Milky Way Satellite Tucana III', Astrophysical Journal, vol. 838, no. 1, 11. https://doi.org/10.3847/1538-4357/aa5be7

TY - JOUR

T1 - Nearest Neighbor: The Low-mass Milky Way Satellite Tucana III

AU - Simon, J. D.

AU - Li, T. S.

AU - Drlica-Wagner, A.

AU - Bechtol, K.

AU - Marshall, J. L.

AU - James, D. J.

AU - Wang, M. Y.

AU - Strigari, L.

AU - Balbinot, E.

AU - Kuehn, K.

AU - Walker, A. R.

AU - Abbott, T. M.C.

AU - Allam, S.

AU - Annis, J.

AU - Benoit-Lévy, A.

AU - Brooks, D.

AU - Buckley-Geer, E.

AU - Burke, D. L.

AU - Rosell, A. Carnero

AU - Kind, M. Carrasco

AU - Carretero, J.

AU - Cunha, C. E.

AU - D'Andrea, C. B.

AU - Costa, L. N.Da

AU - Depoy, D. L.

AU - Desai, S.

AU - Doel, P.

AU - Fernandez, E.

AU - Flaugher, B.

AU - Frieman, J.

AU - García-Bellido, J.

AU - Gaztanaga, E.

AU - Goldstein, D. A.

AU - Gruen, D.

AU - Gutierrez, G.

AU - Kuropatkin, N.

AU - Maia, M. A.G.

AU - Martini, P.

AU - Menanteau, F.

AU - Miller, C. J.

AU - Miquel, R.

AU - Neilsen, E.

AU - Nord, B.

AU - Ogando, R.

AU - Plazas, A. A.

AU - Romer, A. K.

AU - Rykoff, E. S.

AU - Sanchez, E.

AU - Santiago, B.

AU - Scarpine, V.

AU - Schubnell, M.

AU - Sevilla-Noarbe, I.

AU - Smith, R. C.

AU - Sobreira, F.

AU - Suchyta, E.

AU - Swanson, M. E.C.

AU - Tarle, G.

AU - Whiteway, L.

AU - Yanny, B.

PY - 2017/3/20

Y1 - 2017/3/20

N2 - © 2017. The American Astronomical Society. All rights reserved. We present Magellan/IMACS spectroscopy of the recently discovered Milky Way satellite Tucana III (Tuc III). We identify 26 member stars in Tuc III from which we measure a mean radial velocity of v hel = -102.3 ±0.4 (stat.) ±2.0 (sys.)km s-1, a velocity dispersion of 0.1+0.7-0.1 km s-1, and a mean metallicity of (Fe/H)= -2.42+0.07-0.08. The upper limit on the velocity dispersion is σ < 1.5 at 95.5% confidence, and the corresponding upper limit on the mass within the half-light radius of Tuc III is 9.0 × 104 M o. We cannot rule out mass-to-light ratios as large as 240 M oL/o for Tuc III, but much lower mass-to-light ratios that would leave the system baryon-dominated are also allowed. We measure an upper limit on the metallicity spread of the stars in Tuc III of 0.19 dex at 95.5% confidence. Tuc III has a smaller metallicity dispersion and likely a smaller velocity dispersion than any known dwarf galaxy, but a larger size and lower surface brightness than any known globular cluster. Its metallicity is also much lower than those of the clusters with similar luminosity. We therefore tentatively suggest that Tuc III is the tidally stripped remnant of a dark matter-dominated dwarf galaxy, but additional precise velocity and metallicity measurements will be necessary for a definitive classification. If Tuc III is indeed a dwarf galaxy, it is one of the closest external galaxies to the Sun. Because of its proximity, the most luminous stars in Tuc III are quite bright, including one star at V = 15.7 that is the brightest known member star of an ultra-faint satellite.

AB - © 2017. The American Astronomical Society. All rights reserved. We present Magellan/IMACS spectroscopy of the recently discovered Milky Way satellite Tucana III (Tuc III). We identify 26 member stars in Tuc III from which we measure a mean radial velocity of v hel = -102.3 ±0.4 (stat.) ±2.0 (sys.)km s-1, a velocity dispersion of 0.1+0.7-0.1 km s-1, and a mean metallicity of (Fe/H)= -2.42+0.07-0.08. The upper limit on the velocity dispersion is σ < 1.5 at 95.5% confidence, and the corresponding upper limit on the mass within the half-light radius of Tuc III is 9.0 × 104 M o. We cannot rule out mass-to-light ratios as large as 240 M oL/o for Tuc III, but much lower mass-to-light ratios that would leave the system baryon-dominated are also allowed. We measure an upper limit on the metallicity spread of the stars in Tuc III of 0.19 dex at 95.5% confidence. Tuc III has a smaller metallicity dispersion and likely a smaller velocity dispersion than any known dwarf galaxy, but a larger size and lower surface brightness than any known globular cluster. Its metallicity is also much lower than those of the clusters with similar luminosity. We therefore tentatively suggest that Tuc III is the tidally stripped remnant of a dark matter-dominated dwarf galaxy, but additional precise velocity and metallicity measurements will be necessary for a definitive classification. If Tuc III is indeed a dwarf galaxy, it is one of the closest external galaxies to the Sun. Because of its proximity, the most luminous stars in Tuc III are quite bright, including one star at V = 15.7 that is the brightest known member star of an ultra-faint satellite.

KW - dark matter

KW - galaxies: dwarf

KW - galaxies: individual (Tucana III)

KW - galaxies: stellar content

KW - Local Group

KW - stars: abundances

U2 - 10.3847/1538-4357/aa5be7

DO - 10.3847/1538-4357/aa5be7

M3 - Article

VL - 838

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1

M1 - 11

ER -

Nearest Neighbor: The Low-mass Milky Way Satellite Tucana III

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Keywords

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