The elongated structure of the Hercules dwarf spheroidal galaxy from deep Large Binocular Telescope imaging

Matthew G. Coleman; Jelte T.A. De Jong; Nicolas F. Martin; Hans Walter Rix; David J. Sand; Eric F. Bell; Richard W. Pogge; David J. Thompson; H. Hippelein; E. Giallongo; R. Ragazzoni; Andrea DiPaola; Jacopo Farinato; Riccardo Smareglia; Vincenzo Testa; Jill Bechtold; John M. Hill; Peter M. Garnavich; Richard F. Green

doi:10.1086/522672

The elongated structure of the Hercules dwarf spheroidal galaxy from deep Large Binocular Telescope imaging

Matthew G. Coleman, Jelte T.A. De Jong, Nicolas F. Martin, Hans Walter Rix, David J. Sand, Eric F. Bell, Richard W. Pogge, David J. Thompson, H. Hippelein, E. Giallongo, R. Ragazzoni, Andrea DiPaola, Jacopo Farinato, Riccardo Smareglia, Vincenzo Testa, Jill Bechtold, John M. Hill, Peter M. Garnavich, Richard F. Green

Research output: Contribution to journal › Article › peer-review

73 Scopus citations

Abstract

We present a deep, wide-field photometric survey of the newly discovered Hercules dwarf spheroidal galaxy (dSph), based on data from the Large Binocular Telescope. Images in B, V, and r were obtained with the Large Binocular Camera covering a 23′ × 23′ field of view to a magnitude of ∼25.5 (5 σ;). This permitted the construction of color-magnitude diagrams that reach approximately 1.5 mag below the Hercules main-sequence turnoff. Three-filter photometry allowed us to preferentially select probable Hercules member stars and to examine the structure of this system at a previously unattained level. We find that the Hercules dwarf is highly elongated (3: 1) considerably more so than any other dSph satellite of the Milky Way, except the disrupting Sagittarius dwarf. Although we cannot rule out that the unusual structure is intrinsic to Hercules as an equilibrium system, our results suggest tidal disruption as a likely cause of this highly elliptical structure. Given the relatively large galactocentric distance of this system (± 12 kpc), signs of tidal disruption would require the Hercules dwarf to be on a highly eccentric orbit around the Milky Way.

Original language	English (US)
Pages (from-to)	L43-L46
Journal	Astrophysical Journal
Volume	668
Issue number	1 PART 2
DOIs	https://doi.org/10.1086/522672
State	Published - 2007

Keywords

Galaxies: Individual (Hercules dwarf spheroidal galaxy)
Galaxies: Kinematics and dynamics

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1086/522672

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Coleman, M. G., De Jong, J. T. A., Martin, N. F., Rix, H. W., Sand, D. J., Bell, E. F., Pogge, R. W., Thompson, D. J., Hippelein, H., Giallongo, E., Ragazzoni, R., DiPaola, A., Farinato, J., Smareglia, R., Testa, V., Bechtold, J., Hill, J. M., Garnavich, P. M., & Green, R. F. (2007). The elongated structure of the Hercules dwarf spheroidal galaxy from deep Large Binocular Telescope imaging. Astrophysical Journal, 668(1 PART 2), L43-L46. https://doi.org/10.1086/522672

Coleman, MG, De Jong, JTA, Martin, NF, Rix, HW, Sand, DJ, Bell, EF, Pogge, RW, Thompson, DJ, Hippelein, H, Giallongo, E, Ragazzoni, R, DiPaola, A, Farinato, J, Smareglia, R, Testa, V, Bechtold, J, Hill, JM, Garnavich, PM & Green, RF 2007, 'The elongated structure of the Hercules dwarf spheroidal galaxy from deep Large Binocular Telescope imaging', Astrophysical Journal, vol. 668, no. 1 PART 2, pp. L43-L46. https://doi.org/10.1086/522672

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title = "The elongated structure of the Hercules dwarf spheroidal galaxy from deep Large Binocular Telescope imaging",

abstract = "We present a deep, wide-field photometric survey of the newly discovered Hercules dwarf spheroidal galaxy (dSph), based on data from the Large Binocular Telescope. Images in B, V, and r were obtained with the Large Binocular Camera covering a 23′ × 23′ field of view to a magnitude of ∼25.5 (5 σ;). This permitted the construction of color-magnitude diagrams that reach approximately 1.5 mag below the Hercules main-sequence turnoff. Three-filter photometry allowed us to preferentially select probable Hercules member stars and to examine the structure of this system at a previously unattained level. We find that the Hercules dwarf is highly elongated (3: 1) considerably more so than any other dSph satellite of the Milky Way, except the disrupting Sagittarius dwarf. Although we cannot rule out that the unusual structure is intrinsic to Hercules as an equilibrium system, our results suggest tidal disruption as a likely cause of this highly elliptical structure. Given the relatively large galactocentric distance of this system (± 12 kpc), signs of tidal disruption would require the Hercules dwarf to be on a highly eccentric orbit around the Milky Way.",

keywords = "Galaxies: Individual (Hercules dwarf spheroidal galaxy), Galaxies: Kinematics and dynamics",

author = "Coleman, {Matthew G.} and {De Jong}, {Jelte T.A.} and Martin, {Nicolas F.} and Rix, {Hans Walter} and Sand, {David J.} and Bell, {Eric F.} and Pogge, {Richard W.} and Thompson, {David J.} and H. Hippelein and E. Giallongo and R. Ragazzoni and Andrea DiPaola and Jacopo Farinato and Riccardo Smareglia and Vincenzo Testa and Jill Bechtold and Hill, {John M.} and Garnavich, {Peter M.} and Green, {Richard F.}",

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doi = "10.1086/522672",

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AU - Coleman, Matthew G.

AU - De Jong, Jelte T.A.

AU - Martin, Nicolas F.

AU - Rix, Hans Walter

AU - Sand, David J.

AU - Bell, Eric F.

AU - Pogge, Richard W.

AU - Thompson, David J.

AU - Hippelein, H.

AU - Giallongo, E.

AU - Ragazzoni, R.

AU - DiPaola, Andrea

AU - Farinato, Jacopo

AU - Smareglia, Riccardo

AU - Testa, Vincenzo

AU - Bechtold, Jill

AU - Hill, John M.

AU - Garnavich, Peter M.

AU - Green, Richard F.

PY - 2007

Y1 - 2007

N2 - We present a deep, wide-field photometric survey of the newly discovered Hercules dwarf spheroidal galaxy (dSph), based on data from the Large Binocular Telescope. Images in B, V, and r were obtained with the Large Binocular Camera covering a 23′ × 23′ field of view to a magnitude of ∼25.5 (5 σ;). This permitted the construction of color-magnitude diagrams that reach approximately 1.5 mag below the Hercules main-sequence turnoff. Three-filter photometry allowed us to preferentially select probable Hercules member stars and to examine the structure of this system at a previously unattained level. We find that the Hercules dwarf is highly elongated (3: 1) considerably more so than any other dSph satellite of the Milky Way, except the disrupting Sagittarius dwarf. Although we cannot rule out that the unusual structure is intrinsic to Hercules as an equilibrium system, our results suggest tidal disruption as a likely cause of this highly elliptical structure. Given the relatively large galactocentric distance of this system (± 12 kpc), signs of tidal disruption would require the Hercules dwarf to be on a highly eccentric orbit around the Milky Way.

AB - We present a deep, wide-field photometric survey of the newly discovered Hercules dwarf spheroidal galaxy (dSph), based on data from the Large Binocular Telescope. Images in B, V, and r were obtained with the Large Binocular Camera covering a 23′ × 23′ field of view to a magnitude of ∼25.5 (5 σ;). This permitted the construction of color-magnitude diagrams that reach approximately 1.5 mag below the Hercules main-sequence turnoff. Three-filter photometry allowed us to preferentially select probable Hercules member stars and to examine the structure of this system at a previously unattained level. We find that the Hercules dwarf is highly elongated (3: 1) considerably more so than any other dSph satellite of the Milky Way, except the disrupting Sagittarius dwarf. Although we cannot rule out that the unusual structure is intrinsic to Hercules as an equilibrium system, our results suggest tidal disruption as a likely cause of this highly elliptical structure. Given the relatively large galactocentric distance of this system (± 12 kpc), signs of tidal disruption would require the Hercules dwarf to be on a highly eccentric orbit around the Milky Way.

KW - Galaxies: Individual (Hercules dwarf spheroidal galaxy)

KW - Galaxies: Kinematics and dynamics

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JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 1 PART 2

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The elongated structure of the Hercules dwarf spheroidal galaxy from deep Large Binocular Telescope imaging

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