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The Stellar Structures around Disk Galaxies

Published online by Cambridge University Press:  01 December 2006

Igor Drozdovsky
Affiliation:
Instituto de Astrofísica de Canarias, Tenerife, Spain (dio@iac.es; http://www.iac.es/galeria/dio) Astronomical Institute of St.Petersburg State University, Russia
Nikolay Tikhonov
Affiliation:
Special Astrophysical Observatory, Russia
Antonio Aparicio
Affiliation:
Instituto de Astrofísica de Canarias, Tenerife, Spain (dio@iac.es; http://www.iac.es/galeria/dio) Department of Astrophysics, University of La Laguna, Tenerife, Spain
Carme Gallart
Affiliation:
Instituto de Astrofísica de Canarias, Tenerife, Spain (dio@iac.es; http://www.iac.es/galeria/dio)
Matteo Monelli
Affiliation:
Instituto de Astrofísica de Canarias, Tenerife, Spain (dio@iac.es; http://www.iac.es/galeria/dio)
Sebastian Hidalgo
Affiliation:
Instituto de Astrofísica de Canarias, Tenerife, Spain (dio@iac.es; http://www.iac.es/galeria/dio)
Edouard J. Bernard
Affiliation:
Instituto de Astrofísica de Canarias, Tenerife, Spain (dio@iac.es; http://www.iac.es/galeria/dio)
Olga Galazutdinova
Affiliation:
Special Astrophysical Observatory, Russia
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Abstract

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We present a brief summary of our current results on the stellar distribution and population gradients of the resolved stars in the surroundings of ∼50 nearby disk galaxies, observed with space- (Hubble & Spitzer) and ground-based telescopes (Subaru, VLT, BTA, Palomar, CFHT, & INT). We examine the radial (in-plane) and vertical (extraplanar) distributions of resolved stars as a function of stellar age and metallicity by tracking changes in the color-magnitude diagram of face-on and edge-on galaxies. Our data show, that the scale length and height of a stellar population increases with age, with the oldest detected stellar populations identified at a large galactocentric radius or extraplanar height, out to typically a few kpc. In the most massive of the studied galaxies there is evidence for a break in number density and color gradients of evolved stars, which plausibly correspond to the thick disk and halo components of the galaxies. The ratio of intermediate-age to old stars in the outermost fields correlate with the gas fraction, while relative sizes of the thick-to-thin disks anticorrelate with galactic circular velocity.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2007

References

Abadi, M. G., Navarro, J. F., & Steinmetz, M. 2006, MNRAS, 365, 747CrossRefGoogle Scholar
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Tikhonov, N., Galazutdinova, O., & Drozdovsky, I., 2005, A&A, 431, 127.Google Scholar
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