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Signatures of long-lived spiral patterns: The color gradient trend

Published online by Cambridge University Press:  05 March 2015

Eric E. Martínez-García
Affiliation:
Instituto de Astronomía, Universidad Nacional Autónoma de México, AP 70-264, Distrito Federal 04510, México; e-mail: [email protected].
Rosa Amelia González-Lópezlira
Affiliation:
Centro de Radioastronomía y Astrofísica, UNAM, Campus Morelia, Michoacán, México; e-mail: [email protected]
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Abstract

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Based both on observations and simulations, recent works propose that the speed of the spiral pattern in disk galaxies may decrease with increasing radius; the implications are that patterns are actually short-lived, and that the azimuthal color/age gradients across spiral arms predicted by density wave theory could not be produced. We, however, have consistently found such gradients, and measured spiral pattern speeds by comparing the observations with stellar population synthesis models (González & Graham 1996; Martínez-García et al. 2009a, b; Martínez-García & González-Lópezlira 2011). Here, we summarize our previous results in non-barred and weakly barred spirals, together with six new, as yet unpublished, objects. On the other hand, we have indeed found a trend whereby pattern speeds at smaller radii are larger than expected from a model that assumes purely circular orbits (cf. Figure 1), likely due to the effect of spiral shocks on the orbits of newborn stars. The results suggest that spirals may behave as steady long-lived patterns.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2015 

References

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