Physical conditions in the narrow-line region of Markarian 3
Abstract
We used the photoionization model code CLOUDY and Hubble Space Telescope Space Telescope Imaging Spectrograph ( HST /STIS) spectroscopy to study the physical conditions in the Markarian 3 narrow-line region (NLR) gas and to infer the nature of the ionizing continuum. The position angle of the low-resolution long-slit aperture was 71° east of north, coincident with the elongated reverse-"S" shaped feature of the NLR. We modeled 11 emission line sources in 7 contiguous regions spanning the central 2" of the NLR. Most of the calculated line ratios match the reddening corrected observed ratios within the a factor of two. The NLR gas is modeled by an absorbed broken power-law continuum. The absorbers have properties similar to those directly observed in Seyfert 1 galaxies. A heterogeneous distribution of dusty and dust-free gas at a range of three different ionization states comprises the modeled NLR gas. This distribution is required to match the emission lines from electronic transitions with a wide range in critical density and from ionic species with a wide range in ionization potential. We find that the NLR gas component with the lowest ionization state lies outside the nominal, kinematically defined bi- cone. We also find that the lowest ionization state component on a given line- of-sight is illuminated by a more highly absorbed continuum than the remaining components. Furthermore, the amount of continuum absorption to the low ionization state components varies from one region to another along the slit. We conclude that the beam of the ionizing radiation does not have sharp cutoff. Instead of collimation by an opaque molecular torus the ionizing radiation might be collimated by an accretion disk wind. In such a model the ionization state of the gas decreases with increasing distance and polar angle from the symmetry axis.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 2006
- Bibcode:
- 2006PhDT........16C
- Keywords:
-
- Narrow-line;
- Markarian 3;
- Active galaxies;
- Photoionization;
- Astronomy, Astrophysics