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Comparison of NIRS0S Ks-band and S4G 3.6 micron data: Fourier amplitudes, force profiles and color maps

Published online by Cambridge University Press:  05 March 2015

Heikki Salo
Affiliation:
Univ. Oulu, Finland, email: heikki.salo@oulu.fi
Eija Laurikainen
Affiliation:
FINCA, Univ. Turku, Finland
the S4G Collaboration
Affiliation:
Various institutions
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Abstract

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Near-IR observations are considered to give an extinction-free view of the old stellar population in galaxies, thus ideal for the analysis of gravitational torques associated with bar and spiral structures. In the past, H or Ks band data have often been employed (Buta et al. 2010, Salo et al. 2010). S4G (Spitzer Survey of Stellar Structure in Galaxies, Sheth et al. 2010) provides new deep homogenious 3.6 and 4.5 micron data for over 2000 nearby galaxies, allowing to probe the bar and spiral properties over a wide range of morphological types and environments. Here we compare the Fourier-amplitude profiles derived from S4G data for about 50 early-type disk galaxies (SO and S0/a), with those from NIRSOS Ks data (Near-IR S0 Survey, Laurikainen et al. 2011). We also make detailed Ks-3.6 micron color maps. Interestingly, nuclear ring features stand up very clearly in these maps, indicating significantly different contributions of recent star formation in the Ks and 3.6 micron bands. However, the effect of these detailed differences on the overall force profiles is fairly small: this confirms that the S4G data can be confidently used for estimation of bar torques.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2015