Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995aas...187.5012a&link_type=abstract
American Astronomical Society, 187th AAS Meeting, #50.12; Bulletin of the American Astronomical Society, Vol. 27, p.1359
Astronomy and Astrophysics
Astronomy
Scientific paper
We present evidence for the production of ionizing photons at the edges of the ionization bi-cone in the Seyfert 2 galaxy NGC 2992. This may be due to fast (250--500 km s(-1) ) radiative shocks where the powerful bipolar outflow interacts with the ISM. NGC 2992 has a prominent bi-cone or double-bowl shaped Extended Emission Line Region (EELR) in [OIII] lambda 5007 and Hα +[NII] narrow band images. Previously measured kinematics show each side expanding with velocities up to 200 km s(-1) . A grid of long-slit spectra covering most of the EELR was obtained with the DBS spectrograph on the MSSSO 2.3m Telescope at Siding Spring, Australia. The wavelength range includes lines from [OII]lambda 3727 to [SIII]lambda 9532 with 2.2--4.1 Angstroms/pix resolution. The grid of spectra allows the ionization parameter U and the electron density n_e to be measured independently at each grid point [regularly spaced at ~ 2'' ( 300 pc, H_0=75 km s(-1) Mpc(-1) )] from emission line ratios. The rate of ionizing photons Q required for a central source, inferred from U = Q/(4pi r(2) nec) , shows enhancement at the edges of the bi-cone, and is relatively constant elsewhere. This suggests that while most of the EELR is illuminated by a central source, there is extra production of ionizing photons at the edges of the bi-cone. This effect is also apparent in the narrow band image excitation map. We will discuss the likely production of these photons by fast radiative shocks generated by the interaction of the strong wind with the ISM.
Allen Mark G.
Dopita Mike A.
Tsvetanov Zlatan
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