The DART Imaging And CaT Survey of the Fornax Dwarf Spheroidal Galaxy

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As part of the DART project we have used the ESO/2.2m Wide Field Imager in conjunction with the VLT/FLAMES* GIRAFFE spectrograph to study the detailed properties of the resolved stellar population of the Fornax dwarf spheroidal galaxy out to and beyond its tidal radius. Fornax dSph has had a complicated evolution and contains significant numbers of young, intermediate age and old stars. We investigate the relation between these different components by studying their photometric, kinematic and abundance distributions. We re-derived the structural parameters of the Fornax dwarf spheroidal using our wide field imaging covering the galaxy out to its tidal ... continued below

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32 pages

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Battaglia, Giuseppina; Tolstoy, E.; Helmi, A.; Irwin, M. J.; Letarte, B.; Jablonka, P. et al. August 28, 2006.

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Description

As part of the DART project we have used the ESO/2.2m Wide Field Imager in conjunction with the VLT/FLAMES* GIRAFFE spectrograph to study the detailed properties of the resolved stellar population of the Fornax dwarf spheroidal galaxy out to and beyond its tidal radius. Fornax dSph has had a complicated evolution and contains significant numbers of young, intermediate age and old stars. We investigate the relation between these different components by studying their photometric, kinematic and abundance distributions. We re-derived the structural parameters of the Fornax dwarf spheroidal using our wide field imaging covering the galaxy out to its tidal radius, and analyzed the spatial distribution of the Fornax stars of different ages as selected from Colour-Magnitude Diagram analysis. We have obtained accurate velocities and metallicities from spectra in the Ca II triplet wavelength region for 562 Red Giant Branch stars which have velocities consistent with membership in Fornax dwarf spheroidal. We have found evidence for the presence of at least three distinct stellar components: a young population (few 100 Myr old) concentrated in the center of the galaxy, visible as a Main Sequence in the Colour-Magnitude Diagram; an intermediate age population (2-8 Gyr old); and an ancient population (> 10Gyr), which are distinguishable from each other kinematically, from the metallicity distribution and in the spatial distribution of stars found in the Colour-Magnitude Diagram. From our spectroscopic analysis we find that the ''metal rich'' stars ([Fe/H] > -1.3) show a less extended and more concentrated spatial distribution, and display a colder kinematics than the ''metal poor'' stars ([Fe/H] < -1.3). There is tentative evidence that the ancient stellar population in the center of Fornax does not exhibit equilibrium kinematics. This could be a sign of a relatively recent accretion of external material, such as the merger of another galaxy or other means of gas accretion at some point in the fairly recent past, consistent with other recent evidence of substructure (Coleman et al. 2004, 2005).

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32 pages

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  • Journal Name: Submitted to Astron.Astrophys.

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  • Report No.: SLAC-PUB-12082
  • Grant Number: AC02-76SF00515
  • Office of Scientific & Technical Information Report Number: 890777
  • Archival Resource Key: ark:/67531/metadc882735

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  • August 28, 2006

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  • Sept. 21, 2016, 2:29 a.m.

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  • Aug. 1, 2017, 1:29 p.m.

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Battaglia, Giuseppina; Tolstoy, E.; Helmi, A.; Irwin, M. J.; Letarte, B.; Jablonka, P. et al. The DART Imaging And CaT Survey of the Fornax Dwarf Spheroidal Galaxy, article, August 28, 2006; [Menlo Park, California]. (digital.library.unt.edu/ark:/67531/metadc882735/: accessed August 17, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.