30 research outputs found
Spectral Statistics and Luminosity Function of a Hard X-ray Complete Sample of Brightest AGNs
We investigated the statistics of the X-ray spectral properties of a complete
flux-limited sample of bright AGNs from HEAO-1 all-sky catalogs to provide the
bright end constraint of the evolution of AGN hard X-ray luminosity function
(HXLF) and the AGN population synthesis model of the X-ray background. Spectral
studies have been made using ASCA and XMM-Newton observation data for almost
all AGNs in this sample.Comment: PTPTex v0.88, 2 pages with 4 figures, Proceedings of the
"Stellar-Mass, Intermediate -Masss, and Supermassive Black Holes" in Kyoto,
Japa
The Infocus Hard X-ray Telescope: Pixellated CZT Detector/Shield Performance and Flight Results
The CZT detector on the Infocus hard X-ray telescope is a pixellated
solid-state device capable of imaging spectroscopy by measuring the position
and energy of each incoming photon. The detector sits at the focal point of an
8m focal length multilayered grazing incidence X-ray mirror which has
significant effective area between 20--40 keV. The detector has an energy
resolution of 4.0keV at 32keV, and the Infocus telescope has an angular
resolution of 2.2 arcminute and a field of view of about 10 arcminutes. Infocus
flew on a balloon mission in July 2001 and observed Cygnus X-1. We present
results from laboratory testing of the detector to measure the uniformity of
response across the detector, to determine the spectral resolution, and to
perform a simple noise decomposition. We also present a hard X-ray spectrum and
image of Cygnus X-1, and measurements of the hard X-ray CZT background obtained
with the SWIN detector on Infocus.Comment: To appear in the proceedings of the SPIE conference "Astronomical
Telescopes and Instrumentation", #4851-116, Kona, Hawaii, Aug. 22-28, 2002.
12 pages, 9 figure
Spectral Statistics and Local Luminosity Function of a Hard X-ray Complete Sample of Brightest AGNs
We have measured the X-ray spectral properties of a complete flux-limited
sample of bright AGNs from HEAO-1 all-sky catalogs to investigate their
statistics and provide greater constraints on the bright-end of the hard X-ray
luminosity function (HXLF) of AGNs and the AGN population synthesis model of
the X-ray background. Spectral studies using data from ASCA, XMM-Newton and/or
Beppo-SAX observations have been made for almost all AGNs in this sample.
The spectral measurements enable us to construct the neutral absorbing column
density (Log nH) distribution and separate HXLFs for absorbed (Log nH[cm-2]>
21.5) and unabsorbed AGNs in the local universe. Our results show evidence for
a difference in the shapes of HXLFs of absorbed and unabsorbed AGNs in that
absorbed AGN HXLF drops more rapidly at higher luminosities than that of
unabsorbed AGNs, which is similar to that previously reported. In the Lx - nH
plot, we found no AGN in the high-luminosity high-intrinsic absorption regime
(Log Lx[erg/s]> 44.5, Log nH[cm-2]> 21.5) in our sample, where we expect about
5 AGNs if we assume that absorbed and unabsorbed having identical AGN HXLF
shapes. We also find that the observed flux with ASCA or XMM-Newton is smaller
than that with HEAO-1 by a factor of 0.29 on average, which is expected for
re-observation of sources with a factor 2.5 variability amplitude scale.Comment: 43 pages(one column), 10 figures(5 electronic only figures have been
included in the preprint source (tar.gz file)), accepted by The Astronomical
Journal, 9. Mar 200
Optical and X-ray Spectroscopy of 1E 0449.4-1823: Demise of the original type 2 QSO
New optical spectra of the original narrow-line quasar 1E 0449.4-1823 show
that it now has broad emission lines of considerable strength, eliminating it
as a "type 2 QSO" candidate. We suggest that the behavior of 1E 0449.4-1823 is
the same as that of some Seyfert 1.8 and 1.9 galaxies, in which Goodrich
attributed long-term variations of their broad Balmer lines to dynamical
motions of obscuring material located in or around the broad-line region. The
optical continuum and broad emission-line regions of 1E 0449.4-1823 may still
be partly covered in our line of sight, which would explain its large
forbidden-line equivalent widths and flat alpha_ox relative to other
low-redshift QSOs. Also present are apparent absorption features in the broad
Balmer lines and in Mg II, which may be related to the past obscuration and
current emergence of the broad-line region. However, it is difficult to
distinguish absorption from broad emission-line peaks that are displaced in
velocity; we consider the latter a plausible competing interpretation of these
peculiar line profiles. An ASCA X-ray spectrum of 1E 0449.4-1823 can be fitted
with a power-law of Gamma = 1.63, intrinsic N_H < 9 x 10^20 cm-2, and no Fe
Kalpha line emission. Its 2-10 keV luminosity is 6.7 x 10^44 ergs/s. With
regard to the still hypothetical type 2 QSOs, we argue that there is little
evidence for the existence of any among X-ray selected samples.Comment: to appear in ApJ July 1, 1998 (vol. 501). 23 pages including figures.
Uses LaTeX macro aasms4.st
Detection of X-ray Emission from Gravitationally Lensed Submillimeter Sources in the Field of Abell 370
We report the detection by Chandra of SMM J02399-0134 and SMM J02399-0136,
two distant (z=1.06 and z=2.81, respectively) submillimeter sources
gravitationally magnified by the galaxy cluster Abell 370. These are
high-significance (> 7-sigma) X-ray detections of the high-redshift
submillimeter source population. The X-ray positions are coincident with the
optical positions to within one arcsecond. The X-ray spectra, while of low
signal-to-noise ratio, are quite hard. Absorbed power law models with fixed
photon indices of imply local absorbing columns cm and unabsorbed luminosities erg s in both
sources. These results imply that nuclear activity is responsible for the bulk
of the luminosity in SMM J02399-0134, and for at least 20% of the luminosity of
SMM J02399-0136, consistent with previous optical observations. We also place
an upper limit on the X-ray flux of a third submillimeter source, SMM
J02400-0134. Considered together with previously published Chandra upper limits
on X-ray flux from submillimeter sources, our results imply that
% of submillimeter sources exhibit X-ray emission from AGN
(90% confidence), consistent with expectations of their contribution to the
diffuse X-ray background.Comment: Corrected typos in Figure 1 labels; Accepted for publication in ApJ
Letters, 6 pages, 2 figures, latex requires emulateapj5.st
Hard X-ray Luminosities of Multinuclei Infrared Luminous Galaxies Showing a Radio/Far-Infrared Excess
We report the results of hard X-ray observations of four multinuclei merging
infrared luminous galaxies (IRLGs). We selected these four sources for their
excess of radio to far-infrared luminosity ratio compared with starburst
galaxies. This excess suggests that activity associated with a supermassive
black hole (SMBH) contributes strongly to the IRLGs' bolometric luminosities.
Although we expect strong hard X-ray emission from the SMBH-driven activity,
the radio-excess multinuclei merging IRLGs show considerably smaller hard X-ray
luminosities relative to far-infrared (40500 m) and infrared (81000
m) luminosities than active galactic nuclei (AGNs) showing a similar
radio-excess. This result may demonstrate that emission in the hard X-ray
region from SMBH-driven activity in the multinuclei merging IRLGs is severely
suppressed compared to a typical spectral energy distribution of SMBH-driven
activity in AGNs. If this is a common property of merging IRLGs, without its
correction, hard X-ray observations underestimate the contribution of
SMBH-driven activity to the bolometric luminosities of merging IRLGs.Comment: 25 pages of text, 4 figures, aaspp4.sty, Astrophysical Journal, in
press (1999, Volume 527
Spectropolarimetry of the Luminous Narrow-Line Seyfert Galaxies IRAS 20181-2244 and IRAS 13224-3809
We observed the narrow-line Seyfert 1 galaxies IRAS 20181-2244 and IRAS
13324-3809 with a new spectropolarimeter on the RC spectrograph at the CTIO 4m
telescope. Previously it had been suggested that IRAS 20181-2244 was a Type 2
QSO and thus might contain an obscured broad-line region which could be
detected by the presence of broad Balmer lines in the polarized flux. We found
the object to be polarized at about 2%, and constant with wavelength, (unlike
most narrow-line Seyfert 1s), but with no evidence of broad Balmer lines in
polarized flux. The spectropolarimetry indicates that the scattering material
is inside the BLR. IRAS 13224-3809, notable for its high variability in X-ray
and UV wavelengths, has a low polarization consistent with a Galactic
interstellar origin.Comment: 19 pages using (AASTEX) aaspp4.sty and 5 postscript figures To be
published in the Astrophysical Journa
Log N - Log S Relations and Spectral Properties of Sources from the ASCA Large Sky Survey --- their Implications for the Origin of the Cosmic X-ray Background (CXB)
We carried out the first wide-area unbiased survey with the ASCA satellite in
the 0.7-10 keV band around a north Galactic-pole region covering a continuous
area of 7 square degrees (Large Sky Survey; LSS). To make the best use of ASCA
capability, we developed a new source-detection method where the complicated
detector responses are fully taken into account. Applying this method to the
entire LSS data independently in the total (0.7-7 keV), hard (2-10 keV), and
soft (0.7-2 keV) band, we detected 107 sources altogether with sensitivity
limits of 6 x 10E-14 (0.7-7 keV), 1 x 10E-13 (2-10 keV), and 2 x 10E-14 erg
sE-1 cmE-2 (0.7-2 keV), respectively. A complete list of the detected sources
is presented. Based on detailed studies by Monte Carlo simulations, we
evaluated effects of the source confusion and accurately derived Log N - Log S
relation in each survey band. The Log N - Log S relation in the hard band is
located on the extrapolation from the GINGA and HEAO1 results with the
Euclidean slope of -3/2, while that in the soft band is consistent with the
results by ROSAT. At these flux limits, 30 (+/- 3) percent of the CXB in the
0.7-7 keV band and 23 (+/- 3) percent in the 2-10 keV band have been resolved
into discrete sources. The average spectrum of faint sources detected in the
total band shows a photon index of 1.63 +/- 0.07 in the 0.7-10 keV range,
consistent with the comparison of source counts between the hard and the soft
energy band. Those detected in the hard band show a photon index of 1.49 +/-
0.10 in the 2-10 keV range. These spectral properties suggest that contribution
of sources with hard energy spectra become significant at a flux of 10E-13 erg
sE-1 cmE-2 (2-10 keV). The most plausible candidates are type-II AGNs, as
indicated by on-going optical identifications.Comment: 28 pages, 11 figures, to appear in ApJ 518, 1999; figure 1 replaced,
minor errors in text correcte