The circumnuclear gas and dust environment of the ringed Seyfert 2 galaxy MKN 620
Abstract
We present here new flux-calibrated narrow-band images of the circumnuclear region of the Seyfert 2 galaxy Mkn 620 = NGC 2273 in the light of \Oiii Angstroms, \OoneFten Angstromsprotect Angstroms and \Nzwei Angstroms emission lines and two continuum images at lambda 6300 Angstroms and lambda 4260 Angstroms, and in a broad band Gunn r continuum. The color map F_lambda (6300 Angstroms) /F_lambda (4260 Angstroms) reveals a dusty ring-like structure around the nucleus of Mkn 620. This ring-like structure has a diameter of about 14 arcsec corresponding to ~ 1700 pc. Its mean projected thickness is about 500 pc and it is much more prominent in the north-west direction from the nucleus. The dusty ring-like structure surrounds a zone of high ionization which is represented by the \Oiii Angstroms,contour map. The \Nzwei Angstroms,and \Oxein Angstroms,emissions are visible both in the inner high ionized zone and in the outer partially ionized zone (PIZ), which coincides with the dusty ring. Based on the color map F_lambda (6300 Angstroms) /F_lambda (4260 Angstroms) we have estimated an extinction of A_V = 1 (m ) . 04 which yields 10(5x) \Msun for the mass of the dust in the ring. This dust mass would be able to produce the observed 12 and 25 mu m emission if the equilibrium dust temperature T_d is larger than 110 K. This value is determined by the equilibrium between the absorbed and emitted energy, assuming thermal dust reemission of the nonthermal AGN continuum. Both larger nonthermal ionizing flux and star formation events in the innermost circumnuclear region could result in higher equilibrium dust temperature T_d . A second dusty ring is clearly seen on the color map. Its radius is ~ 20 arcsec (2.4 kpc) and is approximately placed on the inward side of an ovally distorted disk.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- April 1999
- Bibcode:
- 1999A&A...344...36Y
- Keywords:
-
- GALAXIES: INDIVIDUAL: MKN 620 = NGC 2273;
- GALAXIES: ISM;
- GALAXIES: SEYFERT;
- GALAXIES: STRUCTURE