J/A+A/456/953 Narrow-band imaging of 6 Seyfert-2 galaxies (Bennert+, 2006)
Size and properties of the narrow-line region in Seyfert-2 galaxies
from spatially-resolved optical spectroscopy
Bennert N., Jungwiert B., Komossa S., Haas M., Chini R.
<Astron. Astrophys. 456, 953 (2006)>
=2006A&A...456..953B 2006A&A...456..953B (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, Seyfert ; Active gal. nuclei ; Photometry, narrow-band
Keywords: galaxies: active - galaxies: nuclei - galaxies: Seyfert
Abstract:
While [OIII] narrow-band imaging is commonly used to measure the size
of the narrow-line regions (NLRs) in active galactic nuclei (AGNs), it
can be contaminated by emission from surrounding starbursts. Recently,
we have shown that long-slit spectroscopy provides a valuable
alternative approach to probe the size in terms of AGN
photoionisation. Moreover, several parameters of the NLR can be
directly accessed. We here apply the same methods developed and
described for the Seyfert-2 galaxy NGC1386 to study the NLR of five
other Seyfert-2 galaxies by using high-sensitivity spatially-resolved
optical spectroscopy obtained at the VLT and the NTT. We probe the
AGN-photoionisation of the NLR and thus, its "real" size using
diagnostic line-ratio diagrams. We derive physical properties of the
NLR such as reddening, ionisation parameter, electron density, and
velocity as a function of distance from the nucleus. For NGC5643, the
diagnostic diagrams unveil a similar transition between line ratios
falling in the AGN regime and those typical for HII regions as found
for NGC1386, thus determining the size of the NLR. For the other four
objects, all measured line ratios fall in the AGN regime. In almost
all cases, both electron density and ionisation parameter decrease
with radius. Deviations from this general behaviour (such as a
secondary peak) seen in both the ionisation parameter and electron
density can be interpreted as signs of shocks from the interaction of
a radio jet and the NLR gas. In several objects, the gaseous velocity
distribution is characteristic for rotational motion in an (inclined)
emission-line disk in the centre. We compare our results to those of
NGC1386 and show that the latter can be considered as prototypical
also for this larger sample. We discuss our findings in detail for
each object.
Description:
Observed and reddening-corrected emission-line ratios relative to
Hbeta are presented as a function of distance from the nucleus. The
uncertainties are in the range of ∼1-15%.
Objects:
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RA (2000) DE Designation(s)
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20 52 02.0 -57 04 09 IC 5063 = ESO 187- 23
22 07 02.1 +10 14 00 NGC 7212 = UGC 11910
05 11 09.0 -34 23 36 ESO 362-8 = IRAS 05093-3427
10 31 52.1 -34 51 13 NGC 3281 = ESO 375- 55
14 32 40.7 -44 10 28 NGC 5643 = ESO 272- 16
03 36 46.4 -36 00 02 NGC 1386 = ESO 358- 35
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 91 99 Observed and reddening-corrected emission-line
ratios relative to Hbeta for 6 galaxies
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See also:
J/A+A/459/55 : Narrow-band imaging of 5 Seyfert-1 galaxies (Bennert+, 2006)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Galaxy Name
11- 16 F6.2 arcsec r Distance from center (1)
18- 22 F5.2 --- OIIobs ?=- Observed line-ratio [OII] 3727 to Hbeta
24- 28 F5.2 --- OIIcor ?=- Reddening-corrected line-ratio
[OIII] 3727 to Hbeta
30- 34 F5.2 --- OIIIobs Observed line-ratio [OIII] 5007 to Hbeta
36- 40 F5.2 --- OIIIcor Reddening-corrected line-ratio
[OIII] 5007 to Hbeta
42- 45 F4.2 --- OIobs ?=- Observed line-ratio [OI] 6300 to Hbeta
47- 50 F4.2 --- OIcor ?=- Reddening-corrected line-ratio
[OI] 6300 to Hbeta
52- 55 F4.2 --- HAobs Observed line-ratio Halpha to Hbeta
57- 60 F4.2 --- HAcor Reddening-corrected line-ratio
Halpha to Hbeta
62- 66 F5.2 --- NIIobs Observed line-ratio [NII] 6583 to Hbeta
68- 71 F4.2 --- NIIcor Reddening-corrected line-ratio
[NII] 6583 to Hbeta
73- 76 F4.2 --- SII1obs ?=- Observed line-ratio [SII] 6716 to Hbeta
78- 81 F4.2 --- SII1cor ?=- Reddening-corrected line-ratio
[SII] 6716 to Hbeta
83- 86 F4.2 --- SII2obs ?=- Observed line-ratio [SII] 6731 to Hbeta
88- 91 F4.2 --- SII2cor ?=- Reddening-corrected line-ratio
[SII] 6731 to Hbeta
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Note (1): Negative values correspond to spectra to the northwest of the
center, positive values correspond to spectra to the southeast.
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Acknowledgements: Nicola Benner, nicola.bennert(at)ucr.edu
References:
Bennert et al., NGC 1386, 2006A&A...446..919B 2006A&A...446..919B
(End) Patricia Vannier [CDS] 30-May-2006