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Regrowth of stellar disks in mature galaxies: The two component nature of NGC 7217 revisited with VIRUS-W

Published online by Cambridge University Press:  09 February 2015

Maximilian H. Fabricius
Affiliation:
Max Planck Institute for Extraterrestrial Physics, Giessenbachstraße, 85748 Garching, Germany University Observatory Munich, Scheinerstraße 1, 81679 Munich, Germany
Lodovico Coccato
Affiliation:
European Southern Observatory, Karl-Schwarzschild-Straße 2, D-85748 Garching bei Muenchen, Germany
Ralf Bender
Affiliation:
Max Planck Institute for Extraterrestrial Physics, Giessenbachstraße, 85748 Garching, Germany University Observatory Munich, Scheinerstraße 1, 81679 Munich, Germany
Niv Drory
Affiliation:
McDonald Observatory, The University of Texas at Austin, 2515 Speedway, Stop C1402, Austin, Texas 78712-1206, USA
Claus Gössl
Affiliation:
University Observatory Munich, Scheinerstraße 1, 81679 Munich, Germany
Martin Landriau
Affiliation:
McDonald Observatory, The University of Texas at Austin, 2515 Speedway, Stop C1402, Austin, Texas 78712-1206, USA
Roberto P. Saglia
Affiliation:
Max Planck Institute for Extraterrestrial Physics, Giessenbachstraße, 85748 Garching, Germany
Jens Thomas
Affiliation:
Max Planck Institute for Extraterrestrial Physics, Giessenbachstraße, 85748 Garching, Germany
Michael J. Williams
Affiliation:
Max Planck Institute for Extraterrestrial Physics, Giessenbachstraße, 85748 Garching, Germany Department of Astronomy, Columbia University, New York 10027, USA
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Abstract

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We have obtained high spectral resolution (R ≈ 9000), integral field observations of the three spiral galaxies NGC 3521, NGC 7217 and NGC 7331 using the new fiber-based Integral Field Unit instrument VIRUS-W at the 2.7 m telescope of the McDonald Observatory in Texas. Our data allow us to revisit previous claims of counter rotation in these objects. A detailed kinematic decomposition of NGC 7217 shows that no counter rotating stellar component is present. We find that NGC 7217 hosts a low dispersion, rotating disk that is embedded in a high velocity dispersion stellar halo or bulge that is co-rotating with the disk. Due to the very different velocity dispersions (≈ 20 km s−1 vs. 150 km s−1) , we are further able to perform a Lick index analysis on both components separately which indicates that the two stellar populations are clearly separated in (Mgb,〈Fe〉) space. The velocities and dispersions of the faster component are very similar to those of the interstellar gas as measured from the [O iii] emission. Morphological evidence of active star formation in this component further suggests that NGC 7217 may be in the process of (re)growing a disk inside a more massive and higher dispersion stellar halo.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2015 

Footnotes

This paper includes data taken at The McDonald Observatory of The University of Texas at Austin.

This paper contains data obtained at the Wendelstein Observatory of the Ludwig-Maximilians University Munich.

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