Sings observations of spiral galaxies evidence for secular evolution

Michael Regan, Michele D. Thornley, Stuart N. Vogel, Kartik Sheth, Bruce T. Draine, David J. Hollenbach, Martin Meyer, Daniel A. Dale, Charles W. Engelbracht, Robert C. Kennicutt, Lee Armus, Daniela Calzetti, Karl D. Gordon, George Helou, Claus Leitherer, Sangeeta Malhotra, George H. Rieke, Marcia J Rieke

Research output: Contribution to journalArticlepeer-review


One process in the secular evolution of galaxies is the formation of pseudo-bulges. The formation of these pseudo-bulges requires the inflow of gas to smaller radii. If the inflow rate is faster than the rate of star formation, a central concentration of gas will form. In this paper we present radial profiles of stellar and 8 micron emission from Polycyclic Aromatic Hydrocarbons (PAHs) for 11 spiral galaxies to investigate whether the interstellar medium in these galaxies contains a central concentration above that expected from the exponential disk. We find that in five of the 11 galaxies there is a central excess in the 8 micron and CO emission above the inner extrapolation of an exponential disk. In particular, all four barred galaxies in the sample have strong central excesses in both 8 micron and CO emission. This correlation suggests that the excess seen in the CO profiles is, in general, not simply due to a radial increase in the CO emissivity.

Original languageEnglish (US)
Pages (from-to)341-346
Number of pages6
JournalAstrophysics and Space Science Proceedings
Issue number202409
StatePublished - 2007


  • Dust
  • Extinction
  • Galaxies: ISM
  • Galaxies: Structure
  • Infrared: Galaxies

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Computer Science Applications
  • Spectroscopy
  • Space and Planetary Science
  • Nuclear and High Energy Physics


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