448 research outputs found
Evidence for two spatially separated UV continuum emitting regions in the Cloverleaf broad absorption line quasar
Testing the standard Shakura-Sunyaev model of accretion is a challenging task
because the central region of quasars where accretion takes place is unresolved
with telescopes. The analysis of microlensing in gravitationally lensed quasars
is one of the few techniques that can test this model, yielding to the
measurement of the size and of temperature profile of the accretion disc. We
present spectroscopic observations of the gravitationally lensed broad
absorption line quasar H1413+117, which reveal partial microlensing of the
continuum emission that appears to originate from two separated regions: a
microlensed region, corresponding to the compact accretion disc; and a
non-microlensed region, more extended and contributing to at least 30\% of the
total UV-continuum flux. Because this extended continuum is occulted by the
broad absorption line clouds, it is not associated with the host galaxy, but
rather with light scattered in the neighbourhood of the central engine. We
measure the amplitude of microlensing of the compact continuum over the
rest-frame wavelength range 1000-7000 \AA. Following a Bayesian scheme, we
confront our measurements to microlensing simulations of an accretion disc with
a temperature varying as . We find a most likely source
half-light radius of cm (i.e., 0.002\,pc) at
0.18\,m, and a most-likely index of . The standard disc
() model is not ruled out by our data, and is found within the 95\%
confidence interval associated with our measurements. We demonstrate that, for
H1413+117, the existence of an extended continuum in addition to the disc
emission only has a small impact on the inferred disc parameters, and is
unlikely to solve the tension between the microlensing source size and standard
disc sizes, as previously reported in the literature.Comment: Accepted for publication in Astronomy and Astrophysics. 12 pages.
Minor changes w.r.t. v1 (language editing, Fig. 5-6
Mid-infrared microlensing of accretion disc and dusty torus in quasars: effects on flux ratio anomalies
Multiply-imaged quasars and AGNs observed in the mid-infrared (MIR) range are
commonly assumed to be unaffected by the microlensing produced by the stars in
their lensing galaxy. In this paper, we investigate the validity domain of this
assumption. Indeed, that premise disregards microlensing of the accretion disc
in the MIR range, and does not account for recent progress in our knowledge of
the dusty torus. To simulate microlensing, we first built a simplified image of
the quasar composed of an accretion disc, and of a larger ring-like torus. The
mock quasars are then microlensed using an inverse ray-shooting code. We
simulated the wavelength and size dependence of microlensing for different
lensed image types and fraction of compact objects projected in the lens. This
allows us to derive magnification probabilities as a function of wavelength, as
well as to calculate the microlensing-induced deformation of the spectral
energy distribution of the lensed images. We find that microlensing variations
as large as 0.1 mag are very common at 11 microns (observer-frame). The main
signal comes from microlensing of the accretion disc, which may be significant
even when the fraction of flux from the disc is as small as 5 % of the total
flux. We also show that the torus of sources with Lbol <~ 10^45 erg/s is
expected to be noticeably microlensed. Microlensing may thus be used to get
insight into the rest near-infrared inner structure of AGNs. Finally, we
investigate whether microlensing in the mid-infrared can alter the so-called
Rcusp relation that links the fluxes of the lensed images triplet produced when
the source lies close to a cusp macro-caustic. This relation is commonly used
to identify massive (dark-matter) substructures in lensing galaxies. We find
that significant deviations from Rcusp may be expected, which means that
microlensing can explain part of the flux ratio problem.Comment: Updated to match the version published in Astronomy and Astrophysics.
12 pages. Abridged version of the abstract. Microlensing maps and source
profiles used in the simulations are available via CDS -
http://vizier.cfa.harvard.edu/viz-bin/VizieR?-source=J/A+A/553/A5
Microlensing of the broad-line region in the quadruply imaged quasar HE0435-1223
Using infrared spectra of the z = 1.693 quadruply lensed quasar HE0435-1223
acquired in 2009 with the spectrograph SINFONI at the ESO Very Large Telescope,
we have detected a clear microlensing effect in images A and D. While
microlensing affects the blue and red wings of the H{\alpha} line profile in
image D very differently, it de-magnifies the line core in image A. The
combination of these different effects sets constraints on the line-emitting
region; these constraints suggest that a rotating ring is at the origin of the
H{\alpha} line. Visible spectra obtained in 2004 and 2012 indicate that the
MgII line profile is microlensed in the same way as the H{\alpha} line. Our
results therefore favour flattened geometries for the low-ionization
line-emitting region, for example, a Keplerian disk. Biconical models cannot be
ruled out but require more fine-tuning. Flux ratios between the different
images are also derived and confirm flux anomalies with respect to estimates
from lens models with smooth mass distributions.Comment: 6 pages, 4 figures, 3 tables, accepted by A&A on 10 April 201
Preliminary Evaluation of Tick Protein Extracts and Recombinant Ferritin 2 as Anti-tick Vaccines Targeting Ixodes ricinus in Cattle
Anti-tick vaccines have the potential to be an environmentally friendly and cost-effective option for tick control. In vaccine development, the identification of efficacious antigens forms the major bottleneck. In this study, the efficacy of immunization with recombinant ferritin 2 and native tick protein extracts (TPEs) against Ixodes ricinus infestations in calves was assessed in two immunization experiments. In the first experiment, each calf (n = 3) was immunized twice with recombinant ferritin 2 from I. ricinus (IrFER2), TPE consisting of soluble proteins from the internal organs of partially fed I. ricinus females, or adjuvant, respectively. In the second experiment, each calf (n = 4) was immunized with protein extracts from the midgut (ME) of partially fed females, the salivary glands (SGE) of partially fed females, a combination of ME and SGE, or adjuvant, respectively. Two weeks after the booster immunization, calves were challenged with 100 females and 200 nymphs. Blood was collected from the calves before the first and after the second immunization and fed to I. ricinus females and nymphs using an in vitro artificial tick feeding system. The two calves vaccinated with whole TPE and midgut extract (ME) showed hyperemia on tick bite sites 2 days post tick infestation and exudative blisters were observed in the ME-vaccinated animal, signs that were suggestive of a delayed type hypersensitivity (DTH) reaction. Significantly fewer ticks successfully fed on the three animals vaccinated with TPE, SGE, or ME. Adults fed on the TPE and ME vaccinated animals weighed significantly less. Tick feeding on the IrFER2 vaccinated calf was not impaired. The in vitro feeding of serum or fresh whole blood collected from the vaccinated animals did not significantly affect tick feeding success. Immunization with native I. ricinus TPEs thus conferred a strong immune response in calves and significantly reduced the feeding success of both nymphs and adults. In vitro feeding of serum or blood collected from vaccinated animals to ticks did not affect tick feeding, indicating that antibodies alone were not responsible for the observed vaccine immunity
Microlensing in H1413+117 : disentangling line profile emission and absorption in a broad absorption line quasar
On the basis of 16 years of spectroscopic observations of the four components
of the gravitationally lensed broad absorption line (BAL) quasar H1413+117,
covering the ultraviolet to visible rest-frame spectral range, we analyze the
spectral differences observed in the P Cygni-type line profiles and have used
the microlensing effect to derive new clues to the BAL profile formation. We
confirm that the spectral differences observed in component D can be attributed
to a microlensing effect lasting at least a decade. We show that microlensing
magnifies the continuum source in image D, leaving the emission line region
essentially unaffected. We interpret the differences seen in the absorption
profiles of component D as the result of an emission line superimposed onto a
nearly black absorption profile. We also find that the continuum source and a
part of the broad emission line region are likely de-magnified in component C,
while components A and B are not affected by microlensing. We show that
microlensing of the continuum source in component D has a chromatic dependence
compatible with the thermal continuum emission of a standard Shakura-Sunyaev
accretion disk. Using a simple decomposition method to separate the part of the
line profiles affected by microlensing and coming from a compact region from
the part unaffected by this effect and coming from a larger region, we
disentangle the true absorption line profiles from the true emission line
profiles. The extracted emission line profiles appear double-peaked, suggesting
that the emission is occulted by a strong absorber, narrower in velocity than
the full absorption profile, and emitting little by itself. We propose that the
outflow around H1413+117 is constituted by a high-velocity polar flow and a
denser, lower velocity disk seen nearly edge-on.Comment: Accepted for publication in Astronomy and Astrophysic
A gravitationally lensed quasar discovered in OGLE
Indexación: Scopus; Web of Science.We report the discovery of a new gravitationally lensed quasar (double) from the Optical Gravitational Lensing Experiment (OGLE) identified inside the ~670deg2 area encompassing the Magellanic Clouds. The source was selected as one of ~60 'red W1-W2' mid-infrared objects from WISE and having a significant amount of variability in OGLE for both two (or more) nearby sources. This is the first detection of a gravitational lens, where the discovery is made 'the other way around', meaning we first measured the time delay between the two lensed quasar images of -132 < tAB < -76 d (90 per cent CL), with the median tAB ~-102 d (in the observer frame), and where the fainter image B lags image A. The system consists of the two quasar images separated by 1.5 arcsec on the sky, with I ~20.0mag and I ~19.6mag, respectively, and a lensing galaxy that becomes detectable as I ~21.5 mag source, 1.0 arcsec from image A, after subtracting the two lensed images. Both quasar images show clear AGN broad emission lines at z=2.16 in the New Technology Telescope spectra. The spectral energy distribution (SED) fitting with the fixed source redshift provided the estimate of the lensing galaxy redshift of z ~0.9 ± 0.2 (90 per cent CL), while its type is more likely to be elliptical (the SED-inferred and lens-model stellar mass is more likely present in ellipticals) than spiral (preferred redshift by the lens model). © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.https://academic.oup.com/mnras/article/476/1/663/483368
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