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Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

Gas Disks and Supermassive Black Holes in Nearby Radio Galaxies

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3.5.2 Flux ratios <strong>and</strong> ionization<br />

In Figure 3.26 we show the [N II] flux as a function of Hα narrow l<strong>in</strong>e flux for each<br />

central spectrum. The values are compatible with values typically found for photo-<br />

ionization <strong>and</strong> shock models (see, for example, Doptia et al., 1997). The unusually<br />

low ratios shown <strong>in</strong> two nuclei (NGC 383 <strong>and</strong> M84) are likely a consequence of the<br />

high degree of blend<strong>in</strong>g of the l<strong>in</strong>es <strong>in</strong> these observations (see panel (d) of Figures 3.4<br />

<strong>and</strong> 3.15), rather than any underly<strong>in</strong>g physics.<br />

While we are satisfied that our data have not produced any results that are <strong>in</strong>-<br />

compatible with reasonable parameters, detailed model<strong>in</strong>g is required to underst<strong>and</strong><br />

the various ionization mechanisms at work <strong>in</strong> each <strong>in</strong>dividual case. We <strong>in</strong>tend to<br />

undertake this type of model<strong>in</strong>g <strong>and</strong> present the outcomes <strong>in</strong> future work.<br />

3.5.3 Are we observ<strong>in</strong>g broad l<strong>in</strong>es?<br />

The fit to the central spectrum is improved <strong>in</strong> 62% of the galaxies by the <strong>in</strong>clusion<br />

of an additional free Gaussian component (see §4.2). Each of these fits resulted <strong>in</strong><br />

the supplementary component be<strong>in</strong>g centered redwards of the Hα l<strong>in</strong>e with a velocity<br />

dispersion between about two <strong>and</strong> ten times that of the narrow l<strong>in</strong>es; thus we describe<br />

this feature as a broad fit component. We identify these broad components <strong>in</strong> 73%<br />

83

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