ABSTRACT

We have studied the luminosity function (LF) of H II regions in the disk of the Seyfert 1 galaxy NGC 6814. We find that the LF is very similar to LFs of other late-type, not necessarily active, spiral galaxies. Although the Seyfert nucleus shows its character by emitting strongly in Hα, the disk H II regions seem not to be influenced by the active nucleus.

NGC 6814 is an Sbc galaxy with well-defined spiral arms, of type Seyfert 1. Because of the strong X-ray emission, it is considered a key object for understanding nuclear activity.

We have obtained new Hα observations with the 4.2m William Herschel Telescope (WHT) on La Palma, using the TAURUS instrument in imaging mode. The final continuum subtracted Hα image has high sensitivity (H II region detection limit is L = 1036.9 erg s-1) and resolution (0.8 arcsec, or about 100 pc at the distance of NGC 6814). From the image, we have measured positions, diameters and fluxes of a total number of 735 H II regions (Knapen et al. 1993). We found that the nucleus is a strong Hα emitter, of luminosity L = 1039.9 erg s-1.

From our catalog of H II regions we constructed a luminosity function (LF), for all the H II regions in the disk of the galaxy, and for arm and interarm H II regions separately. Figure 1 shows the total LF. The slope of the LF is a = –2.37 ± 0.09, well within the range of slopes measured in the literature for galaxies of similar morphological type. The arm and interarm LF slopes are equal within the fitting uncertainties.