245 research outputs found
Observations of multiple nucleus galaxies
Disturbed galaxies with two nuclei display the final state of the interaction process of two galaxies (Kollatschny et al., 1986; Fricke and Kollatschny, 1989). A few of these double nucleus galaxies contain Seyfert nuclei. Making the assumption that the Seyfert galaxies Mkn 231 and Mkn 273 are galaxies in the final state of merging, having strong tidal arms but unresolved nuclei, one can estimate that 4 percent of all Seyfert galaxies are in the merging process. The luminosities of multiple nucleus Seyfert galaxies are extremely high in comparison to morphologically undisturbed Seyfert galaxies. In a table, mean values of the visual and blue luminosities and of the far-infrared and radio (6 cm) luminosities as well as the H alpha fluxes are listed for both classes are shown. In addition, the authors have separated Seyfert 1 and Seyfert 2 galaxies. In all cases the luminosities of double nucleus Seyfert galaxies are higher by a factor of more than two with respect to undisturbed Seyfert galaxies. This result might be explained by higher luminosities in the early phases of a Seyfert's life-under the assumption that the nonthermal activity is triggered by tidal interaction-and/or additional strong starburst phenomena. Due to strong nuclear absorption, the UV spectra of these Seyfert nuclei are unusually weak. Corresponding to the Seyfert survey, the authors obtained the H alpha and far infrared radiation (FIR) luminosities as well as the (0III)5007/H beta line ratios of a small sample of non-Seyfert nuclei in double nucleus galaxies. The direct image and the velocity field of the double starburst galaxy Mkn 788 (Kollatschny et al., 1986) are shown. The authors compared their measurements with those of normal interacting galaxies of Keel et al. (1985) and Bushouse (1987). The mean FIR luminosity per nucleus in multiple systems is the same as that of interacting galaxies. But the mean H alpha luminosities as well as the (OIII)/H beta line ratios are higher by a factor of 1.5-2 than those of normal interacting galaxies
Accretion disk wind as explanation for the broad-line region structure in NGC 5548
Supermassive black holes in the centers of active galactic nuclei (AGN) are
surrounded by broad-line regions (BLRs). The broad emission lines seen in the
AGN spectra are emitted in this spatially unresolved region. We intend to
obtain information on the structure and geometry of this BLR based on observed
line profiles. We modeled the rotational and turbulent velocities in the
line-emitting region on the basis of the line-width FWHM and line dispersion
sigma_line of the variable broad emission lines in NGC5548. Based on these
velocities we estimated the height of the line-emitting regions above the
midplane in the context of their distances from the center. The broad emission
lines originate at distances of 2 to 27 light days from the center. Higher
ionized lines originate in the inner region (lesser equal 13 light days) in
specific filamentary structures 1 to 14 light days above the midplane. In
contrast, the Hbeta line is emitted in an outer (6 - 26 light days), more
flattened configuration at heights of 0.7 to 4 light days only above the
midplane. The derived geometry of the line-emitting region in NGC5548 is
consistent with an outflowing wind launched from an accretion disk.Comment: 4 pages, 5 figures, Astron. & Astrophys. Letter, in pres
Accretion disk wind in the AGN broad-line region: Spectroscopically resolved line profile variations in Mrk110
Detailed line profile variability studies of the narrow line Seyfert 1 galaxy
Mrk110 are presented. We obtained the spectra in a variability campaign carried
out with the 9.2m Hobby-Eberly Telescope at McDonald Observatory. The
integrated Balmer and Helium (HeI,II) emission lines are delayed by 3 to 33
light days to the optical continuum variations respectively. The outer wings of
the line profiles respond much faster to continuum variations than the central
regions. The comparison of the observed profile variations with model
calculations of different velocity fields indicates an accretion disk structure
of the broad line emitting region in Mrk110. Comparing the velocity-delay maps
of the different emission lines among each other a clear radial stratification
in the BLR can be recognized. Furthermore, delays of the red line wings are
slightly shorter than those of the blue wings. This indicates an accretion disk
wind in the BLR of Mrk110. We determine a central black hole mass of M =
. Because of the poorly known inclination angle of
the accretion disk this is a lower limit only.Comment: 12 pages, 11 figures, Astron & Astrophys, in pres
Vertical broad-line region structure in nearby active galactic nuclei
Broad emission lines are emitted in the surroundings of supermassive black
holes in the centers of active galactic nuclei (AGN). This region is spatially
not resolved. We intend to get information on the structure and geometry of
this broad emitting line region (BLR) based on line profile observations. We
model the rotational and turbulent velocities in the line-emitting regions
based on observed full-width at half maximum line values (FWHM) and
{\sigma}_{line} of the variable broad emission lines in four nearby AGN: NGC
3783, NGC 7469, NGC 5548, and 3C 390.3. On the basis of these velocities, we
estimate the height of the line-emitting regions above the midplane in context
with their distances from the center. The H{\beta} lines are emitted in a more
flattened configuration above the midplane in comparison to the highly ionized
lines. The H{\beta} lines originate at heights of 0.7 to 1.6 light-days and at
distances of 1.4 to 24 light-days with height/distance (H/R) ratios of only
0.07 to 0.5. The highly ionized lines originate at smaller radii than the
H{\beta} lines and/or at greater distances above the midplane with H/R values
of 0.2 to 1.7. In total, the emission lines do not originate in a thin
atmosphere of an accretion disk but rather at very extended regions above an
accretion disk. The observed geometries of the line-emitting regions resemble
the geometries of accretion disk wind models. Furthermore, the angle of the
central opening cone (generated by the emitting regions of the highly ionized
lines) is small for those galaxies with slow rotational velocities and
increases with the rotation velocity of the central region. The derived
geometries of the line-emitting regions of all four AGN are consistent with the
geometries that are predicted in outflowing disk wind models.Comment: 12 pages, 18 figures, Astronomy & Astrophysics in pres
The shape of broad-line profiles in AGN
We present a study of the broad optical/UV emission line profiles in AGN
(active galactic nuclei) to get information on the dominant velocity components
(turbulence, rotation, etc.) in the central broad-line region (BLR). We
introduce line broadening simulations of emission line profiles and compare
these results with the largest homogeneous data set of reverberation-mapped
AGN. The underlying broad-line profiles in AGN are Lorentzian profiles caused
by turbulence in the line emitting region. The turbulent velocities are
different for the different line emitting regions of Ha, Hg, Lya, CIII] 1909,
He II 1640, and Si IV 1400. The turbulent velocities go from 400 km/s for Hb up
to 3,800 km/s for Lya+Nv 1240. The dominating broadening mechanism of these
profiles is broadening due to rotation. The rotation velocities causing the
line profile broadening go from 500 km/s up to 6,500 km/s. Here we present
interrelations between observed emission line widths (FWHM) and their related
rotational velocities to correct for the contribution of the turbulence to the
broad-line profiles.Comment: 10 pages, 19 figures, to be published in A&
Variability of Fe II Emission Features in the Seyfert 1 Galaxy NGC 5548
We study the low-contrast Fe II emission blends in the ultraviolet
(1250--2200A) and optical (4000--6000A) spectra of the Seyfert 1 galaxy NGC
5548 and show that these features vary in flux and that these variations are
correlated with those of the optical continuum. The amplitude of variability of
the optical Fe II emission is 50% - 75% that of Hbeta and the ultraviolet Fe II
emission varies with an even larger amplitude than Hbeta. However, accurate
measurement of the flux in these blends proves to be very difficult even using
excellent Fe II templates to fit the spectra. We are able to constrain only
weakly the optical Fe II emission-line response timescale to a value less than
several weeks; this upper limit exceeds all the reliably measured emission-line
lags in this source so it is not particularly meaningful. Nevertheless, the
fact that the optical Fe II and continuum flux variations are correlated
indicates that line fluorescence in a photoionized plasma, rather than
collisional excitation, is responsible for the Fe II emission. The iron
emission templates are available upon request.Comment: 34 pages including 12 figures and 2 tables. Accepted for publication
by ApJ (tentatively in vol. 626 June 10, 2005
Geometry and Kinematics in the Central Broad-Line Region of a Seyfert 1 Galaxy
We recorded spectra of the highly variable Seyfert 1 galaxy Mrk110 in a
variability campaign with the 9.2m Hobby-Eberly Telescope at McDonald
Observatory in order to study the detailed line profile variations of the broad
emission lines. Here we show that only an AGN model predicting the formation of
the broad Hb line emission in the wind of an accretion disk matches the
observed 2-D variability pattern. Furthermore, we derive an improved mass of
the central supermassive black hole of M = 1.0(+1.0,-0.5)E7 M_sun from the Hb
velocity-delay map.Comment: 4 pages, 10 figures. A&A Letters, in pres
The environment of AGNs and the activity degree of their surrounding galaxies
Aims. We present results of a comprehensive spectral study on the large-scale
environment of AGNs based on Sloan Spectroscopic Survey data. Methods. We
analyzed the spectra of galaxies in the environment of AGN and other activity
classes up to distances of 1 Mpc. Results. The mean H{\alpha} and [OIII]
{\lambda}5007 line luminosities in the environmental galaxies within a
projected radius of 1 Mpc are highest around Seyfert 1 galaxies, with
decreasing luminosities for Seyfert 2 and HII galaxies, and lowest for
absorption line galaxies. Furthermore, there is a trend toward H{\alpha} and
[OIII] luminosities in the environmental galaxies increasing as a function of
proximity to the central emission line galaxies. There is another clear trend
toward a neighborhood effect within a radius of 1000 kpc for the AGN and
non-AGN types: Seyfert galaxies tend to have the highest probability of having
another Seyfert galaxy in the neighborhood. HII galaxies tend to have the
highest probability of having another HII galaxy in the neighborhood, etc. The
number of companions within 1000 kpc is inversely correlated with the
H{\alpha}, [OIII] {\lambda}5007, as well as with the continuum luminosities of
the central galaxies, regardless of whether they are of Seyfert, HII, or
absorption line types.Comment: 9 pages, 6 figures, to be published in A&
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