期刊
ASTROPHYSICAL JOURNAL
卷 652, 期 2, 页码 1112-1121出版社
IOP PUBLISHING LTD
DOI: 10.1086/505382
关键词
dust, extinction; galaxies : individual (NGC 628, NGC 3351, NGC 3521, NGC 3627, NGC 4321, NGC 4736, NGC 4826, NGC 5055, NGC 5194, NGC 6946, NGC 7331); galaxies : ISM; galaxies : structure; infrared : galaxies
One possible way for spiral galaxies to internally evolve would be for gas to flow to the center and form stars in a central disk (pseudo-bulge). 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 mu m 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. In general, we find that the two-dimensional CO and PAH emission morphologies are similar, and that they exhibit similar radial profiles. We find that in 6 of the 11 galaxies there is a central excess in the 8 mu m and CO emission above the inward extrapolation of an exponential disk. In particular, all four barred galaxies in the sample have strong central excesses in both 8 mu m and CO emission. These correlations suggest that the excess seen in the CO profiles is, in general, not simply due to a radial increase in the CO emissivity. In the inner disk, the ratio of the stellar to the 8 mu m radial surface brightness is similar for 9 of the 11 galaxies, suggesting a physical connection between the average stellar surface brightness and the average gas surface brightness at a given radius. We also find that the ratio of the CO to 8 mu m PAH surface brightness is consistent over the sample, implying that the 8 mu m PAH surface brightness can be used as an approximate tracer of the interstellar medium.
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