227 research outputs found
The Spectral Energy Distributions of Red 2MASS AGN
We present infrared (IR) to X-ray spectral energy distributions (SEDs) for 44
red AGN selected from the 2MASS survey on the basis of their red J-K color
(>2 mag) and later observed by Chandra. In comparison with optically-, radio-,
and X-ray selected AGN, their median SEDs are red in the optical and near-IR
with little/no blue bump. It thus seems that near-IR color selection isolates
the reddest subset of AGN that can be classified optically. The shape of the
SEDs is generally consistent with modest absorption by gas (in the X-ray) and
dust (in the optical-IR). The levels of obscuration, estimated from X-rays,
far-IR and our detailed optical/near-IR color modeling are all consistent
implying N_H < few*10^{22} cm^{-2}. We present SED models that show how the AGN
optical/near-IR colors change due to differing amounts of reddening, AGN to
host galaxy ratio, redshift and scattered light emission and apply them to the
sources in the sample. We find that the 2MASS AGN optical color, B-R, and to a
lesser extent the near-IR color, J-K, are strongly affected by reddening,
host galaxy emission, redshift, and in few, highly polarized objects, also by
scattered AGN light. The obscuration/inclination of the AGN allows us to see
weaker emission components which are generally swamped by the AGN.Comment: 52 pages, 17 figures, accepted for publication in Ap
PCA of the spectral energy distribution and emission line properties of red 2MASS AGN
We analyze the spectral energy distributions (SEDs) and emission line
properties of the red (J-K > 2) 2MASS AGN observed by Chandra using
principle component analysis. The sample includes 44 low redshift AGN with low
or moderate obscuration (N_H < 10^{23} cm^{-2}) as indicated by X-rays and SED
modeling. The obscuration of the AGN allows us to see weaker emission
components (host galaxy emission, AGN scattered light) which are usually
outshone by the AGN. The first four eigenvectors explain 70% of the variance in
the sample. The dominant cause of variance in the sample (eigenvector 1) is the
L/Ledd ratio strengthened by intrinsic absorption. Eigenvector 2 is related to
host galaxy (relative to the observed AGN) emission and eigenvectors 3 and 4
distinguish between two sources of obscuration: host galaxy absorption and
circumnuclear absorption. Although our analysis is consistent with unification
schemes where inclination dependent obscuration is important in determining the
AGN SEDs, the L/Ledd ratio is the most important factor, followed by host
galaxy emission.Comment: 16 pages, 9 figures, accepted for publication in Ap
Black hole masses from power density spectra: determinations and consequences
We analyze the scaling of the X-ray power density spectra with the mass of
the black hole on the example of Cyg X-1 and Seyfert 1 galaxy NGC 5548. We show
that the high frequency tail of the power density spectrum can be successfully
used for determination of the black hole mass. We determine the masses of the
black holes in 6 Broad Line Seyfert 1 galaxies, 5 Narrow Line Seyfert 1
galaxies and two QSOs using available power density spectra. The proposed
scaling is clearly appropriate for other Seyfert galaxies and QSOs. In all but
1 normal Seyferts the resulting luminosity to the Eddington luminosity ratio is
smaller than 0.15, with a source MCG -6-15-30 being an exception. The
applicability of the same scaling to Narrow Line Seyfert 1 is less clear and
there may be a systematic shift between the power spectra of NLS1 and S1
galaxies of the same mass, leading to underestimation of the black hole mass.
However, both the method based on variability and the method based on spectral
fitting show that those galaxies have relatively low masses and high luminosity
to the Eddington luminosity ratio, supporting the view of those objects as
analogs of galactic sources in their high/soft or very high state based on the
overall spectral shape. Bulge masses of their host galaxies are similar to
normal Seyfert galaxies so they do not follow the black hole mass-bulge mass
relation for Seyfert galaxies, being evolutionary less advanced, as suggested
by Mathur (2000). The bulge mass-black hole mass relation in our sample is
consistent with being linear, with black hole to bulge ratio 0.03 %,
similar to Wandel (1999) and Laor (1998, 2001) for low mass objects but
significantly shifted from the relation of Magorrian et al. (1998) and McLure &
Dunlop (2000).Comment: 11 pages, 7 figures, 1 table, accepted for publication in MNRA
The UV spectra of NLS1s - Implications for their broad line regions
We study the UV spectra of NLS1 galaxies and compare them with typical
Seyfert 1 galaxies and quasars. The NLS1 spectra show narrower UV lines as well
as weaker CIV lambda 1549 and CIII] lambda 1909 emission. We show that these
line properties are due to a lower ionization parameter and somewhat higher BLR
cloud densities. These modified conditions can be explained by the hotter big
blue bumps observed in NLS1s, which are in turn due to higher L/L_Edd ratios,
as shown by our accretion disk and corona modeling of the NLS1 continua. We
also present evidence that the Boroson & Green eigenvector 1, which is
correlated with the optical and UV emission-line properties, is not driven by
orientation and hence NLS1s, which have extreme eigenvector 1 values, are not
viewed from an extreme viewing angle.Comment: Contributed talk presented at the Joint MPE,AIP,ESO workshop on
NLS1s, Bad Honnef, Dec. 1999, to appear in New Astronomy Reviews; also
available at http://wave.xray.mpe.mpg.de/conferences/nls1-worksho
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