812 research outputs found
First XMM-Newton study of two Narrow-Line Seyfert 1 galaxies discovered in the Sloan Digital Sky Survey
The Early Data Release of the Sloan Digital Sky Survey (SDSS) contains 150
Narrow-Line Seyfert 1 (NLS1) galaxies, most of them previously unknown. We
present here the study of the X-ray emission from two of these active galaxies
(SDSS J030639.57+000343.2 and SDSS J141519.50-003021.6), based upon XMM-Newton
observations. The spectral and timing characteristics of the two sources are
presented and compared against the typical properties of known NLS1 galaxies.
We found that these two NLS1 are within the dispersion range of the typical
values of this class of AGN, although with some interesting features that
deserve further studies.Comment: 5 pages, 8 figures. Accepted for publication on A&A Main Journa
NGC 2207/IC 2163: A Grazing Encounter with Large Scale Shocks
Radio continuum, Spitzer infrared, optical and XMM-Newton X-ray and UVM2
observations are used to study large-scale shock fronts, young star complexes,
and the galactic nuclei in the interacting galaxies NGC 2207/IC 2163. There are
two types of large-scale shock fronts in this galaxy pair. The shock front
along the rim of the ocular oval in IC 2163 has produced vigorous star
formation in a dusty environment. In the outer part of the companion side of
NGC 2207, a large-scale front attributed to disk or halo scraping is
particularly bright in the radio continuum but not in any tracers of recent
star formation or in X-rays. This radio continuum front may be mainly in the
halo on the back side of NGC 2207 between the two galaxies. Values of the flux
density ratio S(8 um)/S(6 cm) of kpc-sized, Spitzer IRAC star-forming clumps in
NGC 2207/IC 2163 are compared with those of giant H II regions in M81. We find
evidence that in 2001 a radio supernova was present in the core of feature i, a
mini-starburst on an outer arm of NGC 2207. X-ray emission is detected from the
NGC 2207 nucleus and from nine discrete sources, one of which corresponds to SN
1999ec, and another may be a radio supernova or a background quasar. The X-ray
luminosity and X-ray spectrum of the NGC 2207 nucleus suggests it is a highly
absorbed, low luminosity AGN.Comment: 30 pages, including 12 embedded eps figure
Ultraviolet and optical properties of Narrow-Line Seyfert 1 galaxies
Narrow Line Seyfert 1 (NLS1) galaxies are remarkable for their extreme
continuum and emission line properties which are not well understood. New
results bearing on the spectroscopic characteristics of these objects are
presented here, with the aim of establishing their typical ultraviolet and
optical spectral behavior. We employ HST observations of 22 NLS1s, which
represent a substantial improvement over previous work in terms of data quality
and sample size. High signal-to-noise NLS1 composite spectra are constructed,
allowing accurate measurements of the continuum shape and the strengths,
ratios, and widths for lines, including weak features which are barely
identifiable in other Active Galactic Nuclei (AGN) composites. We find that the
NLS1 sources have redder UV-blue continua than those typically measured in
other quasars and Seyferts. Objects with UV line absorption show redder
spectra, suggesting that dust is important in modifying the continuum shapes.
The data also permit a detailed investigation of the previously proposed link
between NLS1s and z >~ 4 quasars. Direct comparison of their composite spectra,
as well as a Principal Component Analysis, suggest that high-z QSOs do not show
a strong preference toward NLS1 behavior.Comment: 23 pages (incl. 9 figures, 4 tables), to appear in The Publications
of the Astronomical Society of the Pacifi
Hazards of volcanic lakes: analysis of Lakes Quilotoa and Cuicocha, Ecuador
International audienceVolcanic lakes within calderas should be viewed as high-risk systems, and an intensive lake monitoring must be carried out to evaluate the hazard of potential limnic or phreatic-magmatic eruptions. In Ecuador, two caldera lakes ? Lakes Quilotoa and Cuicocha, located in the high Andean region >3000 a.s.l. ? have been the focus of these investigations. Both volcanoes are geologically young or historically active, and have formed large and deep calderas with lakes of 2 to 3 km in diameter, and 248 and 148 m in depth, respectively. In both lakes, visible gas emissions of CO2 occur, and an accumulation of CO2 in the deep water body must be taken into account. Investigations were carried out to evaluate the hazards of these volcanic lakes, and in Lake Cuicocha intensive monitoring was carried out for the evaluation of possible renewed volcanic activities. At Lake Quilotoa, a limnic eruption and diffuse CO2 degassing at the lake surface are to be expected, while at Lake Cuicocha, an increased risk of a phreatic-magmatic eruption exists
SDSS J143030.22-001115.1: A misclassified narrow-line Seyfert 1 galaxy with flat X-ray spectrum
We used multi-component profiles to model H and [O III]4959,5007 lines for SDSS J143030.22-001115.1, a narrow-line Seyfert 1
galaxy (NLS1) in a sample of 150 NLS1s candidates selected from the Sloan
Digital Sky Survey (SDSS) Early Data Release (EDR). After subtracting the
H contribution from narrow line regions (NLRs), we found that its full
width half maximum (FWHM) of broad H line is nearly 2900 \kms,
significantly larger than the customarily adopted criterion of 2000 \kms. With
its weak Fe II multiples, we think that SDSS J143030.22-001115.1 can't be
classified as a genuine NLS1. When we calculate the virial black hole masses of
NLS1s, we should use the H linewidth after subtracting the H
contribution from NLRs.Comment: 7 pages, 1 table, accepted by ChJA
The rise of an ionized wind in the Narrow Line Seyfert 1 Galaxy Mrk 335 observed by XMM-Newton and HST
We present the discovery of an outflowing ionized wind in the Seyfert 1
Galaxy Mrk 335. Despite having been extensively observed by most of the largest
X-ray observatories in the last decade, this bright source was not known to
host warm absorber gas until recent XMM-Newton observations in combination with
a long-term Swift monitoring program have shown extreme flux and spectral
variability. High resolution spectra obtained by the XMM-Newton RGS detector
reveal that the wind consists of three distinct ionization components, all
outflowing at a velocity of 5000 km/s. This wind is clearly revealed when the
source is observed at an intermediate flux state (2-5e-12 ergs cm^-2 s^-1). The
analysis of multi-epoch RGS spectra allowed us to compare the absorber
properties at three very different flux states of the source. No correlation
between the warm absorber variability and the X-ray flux has been determined.
The two higher ionization components of the gas may be consistent with
photoionization equilibrium, but we can exclude this for the only ionization
component that is consistently present in all flux states (log(xi)~1.8). We
have included archival, non-simultaneous UV data from HST (FOS, STIS, COS) with
the aim of searching for any signature of absorption in this source that so far
was known for being absorption-free in the UV band. In the COS spectra obtained
a few months after the X-ray observations we found broad absorption in CIV
lines intrinsic to the AGN and blueshifted by a velocity roughly comparable to
the X-ray outflow. The global behavior of the gas in both bands can be
explained by variation of the covering factor and/or column density, possibly
due to transverse motion of absorbing clouds moving out of the line of sight at
Broad Line Region scale.Comment: 24 pages, 12 figures, ApJ accepte
The quasar PG 0844+349 in an X-ray weak state
In March 2009 the well-studied quasar, PG 0844+349, was discovered with Swift
to be in an X-ray weak state. A follow-up XMM-Newton observation several weeks
later generated a good quality spectrum of the source, showing substantial
curvature and spectral hardening. In combination with archival data at two
previous epochs when the source was in a bright state, we examine the long-term
spectral and timing properties of PG 0844+349 spanning nearly ten years and a
factor of ten in brightness. Partial covering and blurred reflection models are
compared to the data at each flux state while attempting to maintain
consistency between the various epochs. In terms of the blurred reflection
model, PG 0844+349 is in a reflection dominated state during the 2009 X-ray
weak observations, which can be understood in terms of light bending. Moreover,
the light bending scenario can also account for the short-term (i.e. ~1000s)
spectral variability in the source. Other models cannot be decisively ruled
out, but we note distinguishing features of the models that can be explored for
in higher signal-to-noise data from current and future observatories.Comment: 11 pages. Accepted for publication in MNRA
X-ray Absorption and Optical Extinction in the Partially Obscured Seyfert Nucleus in Mrk 1393
We present a detailed study of the X-ray and optical spectra of the luminous
Seyfert galaxy Mrk 1393, which revealed variable partial obscuration of the
active nucleus. The X-ray spectra obtained by XMM-Newton and Swift show
moderate absorption with a column density around 3x10^21 cm^-2, consistent with
a dust-reddening interpretation of the steep Balmer decrement seen in recent
optical spectra. The X-ray flux in the 0.5 to 2 keV band during the XMM-Newton
observation in 2005 and Swift observation in 2006 was a factor 6 brighter than
that of the ROSAT All Sky Survey in 1991. In the past 4 years, the broad
H\alpha line brightened by a factor of 4 accompanied by a decrease in the
Balmer decrement. A comparison with literature spectra reveals variations in
the dust extinction on time scales of several years, suggesting that the
obscuring material is very close to the active nucleus. These observations
indicate that a dust-to-gas ratio as high as the Galactic value can be present
in moderately thick gas in the vicinity of the central engine within a few
parsecs. We suggest that the obscuring material may be debris disrupted from
the dusty torus.Comment: 25 pages, 5 figures, accepted to A
1H0419-577: a two-state Seyfert Galaxy?
The preliminary results of the BeppoSAX observation of the radio-quiet AGN
1H0419-577 are presented. Despite its broad line optical spectrum, the
intermediate X-ray spectrum (i.e. 2--10 keV) is flatter than typically observed
in Seyfert 1s and no iron line is significantly detected. Even more
intriguingly, a 1992 ROSAT pointed observation suggests a dramatic (~ 1) change
in the spectral shape for E < 2 keV. Such behavior is briefly discussed in the
framework of our current understanding of Comptonization scenarios in the
nuclear regions of radio-quiet AGN.Comment: 4 pages, Latex, 4 Postscript figures, `espcrc2.sty included, to
appear in the Proceedigns of the Workshop "The active X-ray sky: results from
Beppo-SAX and RXTE
The Unified Model of Active Galactic Nuclei: II. Evolutionary Connection
(Abbreviated) We assemble a sample composed of 243 nearby Seyfert galaxies
with redshifts to test the unification scheme. The sample contains
94 BLS1s, 44 NLS1s, 36 X-ray absorbed HBLR S2s, 42 X-ray absorbed non-HBLR S2s
and 27 X-ray unabsorbed Seyfert 2s (unabsorbed non-HBLR S2s and HBLR S2s). We
find that: 1) NLS1s have less massive black hole masses than BLS1s; 2) HBLRS2s
have the same mass distribution of the black holes with BLS1s; 3) the absorbed
non-HBLR S2s have less massive black holes than HBLR S2s; 4) unabsorbed
non-HBLR S2s have the most massive black holes. We thus have a queue of black
hole masses from small to large: narrow to broad line Seyfert galaxies,
providing new evidence for the evolutionary sequence of Seyfert galaxies. We
find that the opening angles of the torus in NLS1s and absorbed non-HBLR S2s
are significantly smaller than that in BLS1s and HBLR S2s. The growth of the
black holes and increases of the opening angles of the tori determine the
various appearances of Seyfert galaxies. We also find that the unabsorbed
Seyfert 2 galaxies could be caused by low gas-to-dust ratios in the present
sample. This indicates that the star formation histories could be different in
the unabsorbed from in absorbed Seyfert 2 galaxies, showing evidence for
suppressed star formation by black hole activities. We outline a new
unification scheme based on the orientation hypothesis: Seyfert galaxies can be
unified by including growth of black holes, Eddington ratios, changing opening
angles of tori and gas-to-dust ratios in the tori. Seyfert galaxies are tending
to finally evolve to unabsorbed non-HBLR Seyfert 2 galaxies, in which the black
holes are accreting with low accretion rates and both the broad line region and
dusty torus disappear.Comment: ApJ, vol 661 (2007), in pres
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