271 research outputs found
Anatomy of the AGN in NGC 5548: V. A clear view of the X-ray narrow emission lines
Context. Our consortium performed an extensive multi-wavelength campaign of
the nearby Seyfert 1 galaxy NGC 5548 in 2013-14. The source appeared unusually
heavily absorbed in the soft X-rays, and signatures of outflowing absorption
were also present in the UV. He-like triplets of neon, oxygen and nitrogen, and
radiative recombination continuum (RRC) features were found to dominate the
soft X-ray spectrum due to the low continuum flux.
Aims. Here we focus on characterising these narrow emission features using
data obtained from the XMM-Newton RGS (770 ks stacked spectrum).
Methods. We use SPEX for our initial analysis of these features.
Self-consistent photoionisation models from Cloudy are then compared with the
data to characterise the physical conditions of the emitting region.
Results. Outflow velocity discrepancies within the O VII triplet lines can be
explained if the X-ray narrow-line region (NLR) in NGC 5548 is absorbed by at
least one of the six warm absorber components found by previous analyses. The
RRCs allow us to directly calculate a temperature of the emitting gas of a few
eV ( K), favouring photoionised conditions. We fit the data with a
Cloudy model of log erg cm s, log cm and log v km s for the emitting
gas; this is the first time the X-ray NLR gas in this source has been modelled
so comprehensively. This allows us to estimate the distance from the central
source to the illuminated face of the emitting clouds as pc,
consistent with previous work.Comment: Accepted by A&A, 15 pages, 6 figure
Endothelial cells support osteogenesis in an in vitro vascularized bone model developed by 3D bioprinting
Bone is a highly vascularized tissue, in which vascularization and mineralization are concurrent processes during skeletal development. Indeed, both components should be included in any reliable and adherent in vitro model platform for the study of bone physiology and pathogenesis of skeletal disorders. To this end, we developed an in vitro vascularized bone model, using a gelatin-nanohydroxyapatite (gel-nHA) 3D bioprinted scaffold. First, we seeded human mesenchymal stem cells (hMSCs) on the scaffold which underwent osteogenic differentiation for two weeks. Then, we included lentiviral-GFP transfected human umbilical vein endothelial cells (HUVECs) within the 3D bioprinted scaffold macropores to form a capillary-like network during two more weeks of culture. We tested three experimental conditions: Condition 1, bone constructs with HUVECs cultured in 1:1 osteogenic medium (OM):endothelial medium (EM); Condition 2, bone constructs without HUVECs cultured in 1:1 OM:EM; Condition 3: bone construct with HUVECs cultured in 1:1 growth medium:EM. All samples resulted in engineered bone matrix. In Conditions 1 and 3, HUVECs formed tubular structures within the bone constructs, with the assembly of a complex capillary-like network visible by fluorescence microscopy in the live tissue and histology. CD31 immunostaining confirmed significant vascular lumen formation. Quantitative real-time PCR was used to quantify osteogenic differentiation and endothelial response. Alkaline phosphatase and runt-related transcription factor 2 upregulation confirmed early osteogenic commitment of hMSCs. Even when OM was removed under Condition 3, we observed clear osteogenesis, which was notably accompanied by upregulation of osteopontin, vascular endothelial growth factor, and collagen type I. These findings indicate that we have successfully realized a bone model with robust vascularization in just four weeks of culture and we highlighted how the inclusion of endothelial cells more realistically supports osteogenesis. The approach reported here resulted in a biologically inspired in vitro model of bone vascularization, simulating de novo morphogenesis of capillary vessels occurring during tissue development
Anatomy of the AGN in NGC 5548: I. A global model for the broadband spectral energy distribution
An extensive multi-satellite campaign on NGC 5548 has revealed this
archetypal Seyfert-1 galaxy to be in an exceptional state of persistent heavy
absorption. Our observations taken in 2013-2014 with XMM-Newton, Swift, NuSTAR,
INTEGRAL, Chandra, HST and two ground-based observatories have together enabled
us to establish that this unexpected phenomenon is caused by an outflowing
stream of weakly ionised gas (called the obscurer), extending from the vicinity
of the accretion disk to the broad-line region. In this work we present the
details of our campaign and the data obtained by all the observatories. We
determine the spectral energy distribution of NGC 5548 from near-infrared to
hard X-rays by establishing the contribution of various emission and absorption
processes taking place along our line of sight towards the central engine. We
thus uncover the intrinsic emission and produce a broadband continuum model for
both obscured (average summer 2013 data) and unobscured ( 2011) epochs of
NGC 5548. Our results suggest that the intrinsic NIR/optical/UV continuum is a
single Comptonised component with its higher energy tail creating the 'soft
X-ray excess'. This component is compatible with emission from a warm,
optically-thick corona as part of the inner accretion disk. We then investigate
the effects of the continuum on the ionisation balance and thermal stability of
photoionised gas for unobscured and obscured epochs.Comment: Accepted for publication in A&A, 19 pages, 13 figure
Directorium in exercitia spiritualia
Sign.: A-I8En port.: grab. xil. con el anagrama de los jesuitasEn el lomo: Exercitia - S.J. - 1615Exercitia spiritualiaDigitalización. Vitoria-Gasteiz : Fundación Sancho el Sabio, 2008EXPOSICIÓN "Casa Común-Danon Etxea"hLeopoldo Zugaza,zATV 35335$5Ayuntamiento de Durango, Museo de Arte e Historia de Durang
A fast and long-lived outflow from the supermassive black hole in NGC 5548
Supermassive black holes in the nuclei of active galaxies expel large amounts
of matter through powerful winds of ionized gas. The archetypal active galaxy
NGC 5548 has been studied for decades, and high-resolution X-ray and UV
observations have previously shown a persistent ionized outflow. An observing
campaign in 2013 with six space observatories shows the nucleus to be obscured
by a long-lasting, clumpy stream of ionized gas never seen before. It blocks
90% of the soft X-ray emission and causes simultaneous deep, broad UV
absorption troughs. The outflow velocities of this gas are up to five times
faster than those in the persistent outflow, and at a distance of only a few
light days from the nucleus, it may likely originate from the accretion disk.Comment: 25 pages, 8 figures. This is the author's version of the work. It is
posted here by permission of the AAAS for personal use, not for
redistribution. The definitive version was published in Science,
electronically available at Science Express (June 19, 2014). For a brief
video explaining the key results of this paper, please visit
http://www.issibern.ch/teams/ngc5548/?page_id=2
[Ejercicios espirituales. LatÃn]
Sign.: []2, A-I8, K6En port. grab. xil. con el anagrama de los jesuitasEn el lomo: Exercitia - S.J. - 1615Directorium in exercitia spiritualiaDigitalización. Vitoria-Gasteiz : Fundación Sancho el Sabio, 2008HolandesaEXPOSICIÓN "Casa Común-Danon Etxea
Detection of an unidentified soft X-ray emission feature in NGC 5548
Context. NGC 5548 is an X-ray bright Seyfert 1 active galaxy. It exhibits a variety of spectroscopic features in the soft X-ray band, in particular including the absorption by the active galactic nucleus (AGN) outflows of a broad range of ionization states, with column densities up to 1027 m-2, and having speeds up to several thousand kilometers per second. The known emission features are in broad agreement with photoionized X-ray narrow and broad emission line models.
Aims. We report on an X-ray spectroscopic study using 1.1 Ms XMM-Newton and 0.9 Ms Chandra grating observations of NGC 5548 spanning two decades. The aim is to search and characterize any potential spectroscopic features in addition to the known primary spectral components that are already modeled in high precision.
Methods. For each observation, we modeled the data using a global fit including an intrinsic spectral energy distribution of the AGNs and the known distant X-ray absorbers and emitters. We utilized as much knowledge from previous studies as possible. The fit residuals were stacked and scanned for possible secondary features.
Results. We detect a weak unidentified excess emission feature at ~18.4 Ã… (18.1 Ã… in the restframe). The feature is seen at > 5s statistical significance taking the look-elsewhere effect into account. No known instrumental issues, atomic transitions, or astrophysical effects can explain this excess. The observed intensity of the possible feature seems to anticorrelate in time with the hardness ratio of the source. However, even though the variability might not be intrinsic, it might be caused by the time-variable obscuration by the outflows. An intriguing possibility is the line emission from charge exchange between a partially ionized outflow and a neutral layer in the same outflow, or in the close environment. Other possibilities, such as emission from a highly ionized component with high outflowing speed, cannot be fully ruled out.Peer ReviewedPostprint (published version
Anatomy of the AGN in NGC 5548. III. The high-energy view with NuSTAR and INTEGRAL
We describe the analysis of the seven broad-band X-ray continuum observations of the archetypal Seyfert 1 galaxy NGC 5548 that were obtained with XMM-Newton or Chandra, simultaneously with high-energy (>10 keV) observations with NuSTAR and INTEGRAL. These data were obtained as part of a multiwavelength campaign undertaken from the summer of 2013 till early 2014. We find evidence of a high-energy cut-off in at least one observation, which we attribute to thermal Comptonization, and a constant reflected component that is likely due to neutral material at least a few light months away from the continuum source. We confirm the presence of strong, partial covering X-ray absorption as the explanation for the sharp decrease in flux through the soft X-ray band. The obscurers appear to be variable in column density and covering fraction on time scales as short as weeks. A fit of the average spectrum over the range 0.3–400 keV with a realistic Comptonization model indicates the presence of a hot corona with a temperature of 40^(+40)_(-10) keV and an optical depth of 2.7^(+0.7)_(-1.2) if a spherical geometry is assumed
Detection of an Unidentified Soft X-ray Emission Feature in NGC 5548
NGC~5548 is an X-ray bright Seyfert 1 active galaxy. It exhibits a variety of
spectroscopic features in the soft X-ray band, including in particular the
absorption by the AGN outflows of a broad range of ionization states, with
column densities up to 1E27 /m^2, and having speeds up to several thousand
kilometers per second. The known emission features are in broad agreement with
photoionized X-ray narrow and broad emission line models. We report on an X-ray
spectroscopic study using 1.1 Ms XMM-Newton and 0.9 Ms Chandra grating
observations of NGC 5548 spanning two decades. The aim is to search and
characterize any potential spectroscopic features in addition to the known
primary spectral components that are already modeled in high precision. We
detect a weak unidentified excess emission feature at 18.4 Angstrom (18.1
Angstrom in the restframe). The feature is seen at >5 sigma statistical
significance taking into account the look elsewhere effect. No known
instrumental issues, atomic transitions, and astrophysical effects can explain
this excess. The observed intensity of the possible feature seems to
anti-correlate in time with the hardness ratio of the source. However, the
variability might not be intrinsic, it might be caused by the time-variable
obscuration by the outflows. An intriguing possibility is the line emission
from charge exchange between a partially ionized outflow and a neutral layer in
the same outflow, or in the close environment. Other possibilities, such as
emission from a highly-ionized component with high outflowing speed, cannot be
fully ruled out.Comment: 14 pages, 8 figures, accepted for publication in Astronomy &
Astrophysic
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