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J/A+A/417/515 I Zw 1 unusual emission line spectrum (Veron-Cetty+, 2004)
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The unusual emission line spectrum of I Zw 1.
Veron-Cetty M.-P., Joly M., Veron P.
<Astron. Astrophys. 417, 515 (2004)>
=2004A&A...417..515V
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ADC_Keywords: Galaxies, spectra
Keywords: galaxies: active - galaxies: individual: I Zw 1
Abstract:
Most Seyfert 1s show strong FeII lines in their spectrum having the
velocity and width of the broad emission lines. To remove the FeII
contribution in these objects, an accurate template is necessary. We
used very high signal-to-noise, medium resolution archive optical
spectra of I Zw 1 to build such a template. I Zw 1 is a bright
narrow-line Seyfert 1 galaxy. As such it is well suited for a detailed
analysis of its emission line spectrum. Furthermore it is known to
have a very peculiar spectrum with, in addition to the usual broad and
narrow line regions, two emission regions emitting broad and blue
shifted [OIII] lines making it a peculiarly interesting object. While
analysing the spectra, we found that the narrow-line region is, unlike
the NLR of most Seyfert 1 galaxies, a very low excitation region
dominated by both permitted and forbidden FeII lines. It is very
similar to the emission spectrum of a blob in eta Carinae which is
a low temperature (T 6500K), relatively high density (N_e_=10^6^cm^-3)
cloud. The FeII lines in this cloud are mainly due to pumping via the
stellar continuum radiation field (Verner et al.,
2002ApJ...581.1154V). We did not succeed in modelling the spectrum of
the broad-line region, and we suggest that a non radiative heating
mechanism increases the temperature in the excited HI region, thus
providing the necessary additional excitation of the FeII lines. For
the low-excitation narrow-line region, we are able to settle
boundaries to the physical conditions accounting for the forbidden and
permitted FeII lines (10^6^<N_e_<10^7^cm^-3^; 10^-6^<U<10^-5^).
Description:
Fig. 8 represents the synthetic FeII spectrum, derived from I Zw 1,
corrected for internal extinction with a Galactic extinction law
(Savage & Mathis 1979) and E(B-V)=0.20. template_iwz1.fits is this
1D spectrum, fits format.
Objects:
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RA (2000) DE Designation(s) (File)
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00 53 35.1 +12 41 34 ZW I 1 (iwz1.fit)
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