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ABSTRACT: Microlensing is a powerful technique which can be used to study the continuum
and the broad line emitting regions in distant AGNs. After a brief description
of the methods and required data, we present recent applications of this
technique. We show that microlensing allows one to measure the temperature
profile of the accretion disc, estimate the size and study the geometry of the
region emitting the broad emission lines.
02/2013;
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ABSTRACT: We present a study of the three forbidden oxygen lines [OI] located in the
optical region (i.e., 5577.339 \r{A} (the green line), 6300.304 \r{A} and
6363.776 \r{A} (the two red lines)) in order to better understand the
production of these atoms in cometary atmospheres. The analysis is based on 48
high-resolution and high signal-to-noise spectra collected with UVES at the ESO
VLT between 2003 and 2011 referring to 12 comets of different origins observed
at various heliocentric distances. The flux ratio of the green line to the sum
of the two red lines is evaluated to determine the parent species of the oxygen
atoms by comparison with theoretical models. This analysis confirms that, at
about 1 AU, H2O is the main parent molecule producing oxygen atoms. At
heliocentric distances > 2.5 AU, this ratio is changing rapidly, an indication
that other molecules are starting to contribute. CO and CO2, the most abundant
species after H2O in the coma, are good candidates and the ratio is used to
estimate their abundances. We found that the CO2 abundance relative to H2O in
comet C/2001 Q4 (NEAT) observed at 4 AU can be as high as ~70 %. The intrinsic
widths of the oxygen lines were also measured. The green line is on average
about 1 km/s broader than the red lines while the theory predicts the red lines
to be broader. This might be due to the nature of the excitation source and/or
a contribution of CO2 as parent molecule of the 5577.339 \r{A} line. At 4 AU,
we found that the width of the green and red lines in comet C/2001 Q4 are the
same which could be explained if CO2 becomes the main contributor for the three
[OI] lines at high heliocentric distances.
10/2012;
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ABSTRACT: When an image of a strongly lensed quasar is microlensed, the different
components of its spectrum are expected to be differentially magnified owing to
the different sizes of the corresponding emitting region. Chromatic changes are
expected to be observed in the continuum while the emission lines should be
deformed as a function of the size, geometry and kinematics of the regions from
which they originate. Microlensing of the emission lines has been reported only
in a handful of systems so far. In this paper we search for microlensing
deformations of the optical spectra of pairs of images in 17 lensed quasars.
This sample is composed of 13 pairs of previously unpublished spectra and four
pairs of spectra from literature. Our analysis is based on a spectral
decomposition technique which allows us to isolate the microlensed fraction of
the flux independently of a detailed modeling of the quasar emission lines.
Using this technique, we detect microlensing of the continuum in 85% of the
systems. Among them, 80% show microlensing of the broad emission lines.
Focusing on the most common lines in our spectra (CIII] and MgII) we detect
microlensing of either the blue or the red wing, or of both wings with the same
amplitude. This observation implies that the broad line region is not in
general spherically symmetric. In addition, the frequent detection of
microlensing of the blue and red wings independently but not simultaneously
with a different amplitude, does not support existing microlensing simulations
of a biconical outflow. Our analysis also provides the intrinsic flux ratio
between the lensed images and the magnitude of the microlensing affecting the
continuum. These two quantities are particularly relevant for the determination
of the fraction of matter in clumpy form in galaxies and for the detection of
dark matter substructures via the identification of flux ratio anomalies.
06/2012;
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ABSTRACT: Isotopic abundance ratios are excellently suited to probe the origin of solar system matter. We review the recent measurements
of the isotopic ratios of the light elements (D/H, 12C/13C, 16O/18O, 14N/15N, 32S/34S) in cometary dust and gas and discuss briefly their implications. Special emphasis will be put on the determinations and
progress performed in the field over the past years thanks to high resolution spectroscopy of cometary comae obtained with
the ESO Very Large Telescope. Future perspectives from space missions and ground-based observations with new large and extremely
large telescopes operating in the optical, infrared and submillimeter wavelengths will be presented.
Earth Moon and Planets 04/2012; 105(2):167-180. · 0.67 Impact Factor
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E. Jehin,
D. Bockelée-Morvan,
N. Dello Russo,
J. Manfroid, D. Hutsemékers,
H. Kawakita,
H. Kobayashi,
R. Schulz,
A. Smette,
J. Stüwe, [......],
C. Arpigny,
N. Biver,
A. Cochran,
J. Crovisier,
P. Magain,
H. Rauer,
H. Sana,
R. J. Vervack,
H. Weaver,
J.-M. Zucconi
[show abstract]
[hide abstract]
ABSTRACT: We report on simultaneous optical and infrared observations of the Halley Family comet 8P/Tuttle performed with the ESO Very
Large Telescope. Such multi-wavelength and coordinated observations are a good example of what can be done to support space
missions. From high resolution optical spectroscopy of the CN (0,0) 388nm and NH2 (0,9,0) 610nm bands using UVES at UT2 we determined 12C/13C=90±10 and 14N/15N=150±20 in CN and we derived a nuclear spin temperature of NH3 of 29±1K. These values are similar to those found in Oort-Cloud and Jupiter Family comets. From low resolution long slit
spectroscopy with FORS1 at UT2 we determined the CN, C3 and C2 production rates and the parent and daughter scale lengths up to 5.2 105km tailward. From high resolution IR spectroscopy with CRIRES at UT1 we measured simultaneously the production rates and
mixing ratios of H2O, HCN, C2H2, CH4, C2H6, and CH3OH.
Earth Moon and Planets 04/2012; 105(2):343-349. · 0.67 Impact Factor
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M. A. T. Groenewegen,
C. Waelkens,
M. J. Barlow,
F. Kerschbaum,
P. Garcia-Lario,
J. Cernicharo,
J. A. D. L. Blommaert,
J. Bouwman,
M. Cohen,
N. Cox, [......],
C. Vamvatira-Nakou,
B. Vandenbussche,
G. C. van de Steene,
S. van Eck,
P. A. M. van Hoof,
H. van Winckel,
E. Verdugo,
R. Wesson,
T. Lebzelter,
R. F. Wing
[show abstract]
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ABSTRACT: MESS (Mass loss of Evolved StarS) is a Herschel Guaranteed Time Key Program that will image about 100, and do spectroscopy of about 50, post-main-sequence objects of all flavours: AGB stars, post-AGB stars, planetary nebulae, luminous blue variables, Wolf-Rayet stars, and supernova remnants. In this review the implementation and current status of MESS is outlined, and first results are presented.
Why Galaxies Care about AGB Stars II: Shining Examples and Common InhabitantsWhy Galaxies Care about AGB Stars II: Shining Examples and Common Inhabitants; 01/2011
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M. A. T. Groenewegen,
C. Waelkens,
M. J. Barlow,
F. Kerschbaum,
P. Garcia-Lario,
J. Cernicharo,
J. A. D. L. Blommaert,
J. Bouwman,
M Cohen,
N Cox, [......],
B. M. Swinyard,
T. Ueta,
C. Vamvatira-Nakou,
B. Vandenbussche,
G. C. Van de Steene,
S. Van Eck,
P. A. M. van Hoof,
H. Van Winckel,
E. Verdugo,
R. Wesson
[show abstract]
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ABSTRACT: MESS (Mass-loss of Evolved StarS) is a Guaranteed Time Key Program that uses the PACS and SPIRE instruments on board the Herschel Space Observatory to observe a representative sample of evolved stars, that include asymptotic giant branch (AGB) and post-AGB stars, planetary nebulae and red supergiants, as well as luminous blue variables, Wolf-Rayet stars and supernova remnants. In total, of order 150 objects are observed in imaging and about 50 objects in spectroscopy. This paper describes the target selection and target list, and the observing strategy. Key science projects are described, and illustrated using results obtained during Herschel's science demonstration phase. Aperture photometry is given for the 70 AGB and post-AGB stars observed up to October 17, 2010, which constitutes the largest single uniform database of far-IR and sub-mm fluxes for late-type stars. Comment: A&A accepted
12/2010;
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[show abstract]
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ABSTRACT: We aim to use microlensing taking place in the lensed quasar Q2237+0305 to
study the structure of the broad line region and measure the size of the region
emitting the CIV and CIII] lines.
Methods: Based on 39 spectrophotometric monitoring data points obtained
between Oct. 2004 and Dec. 2007, we derived lightcurves for the CIV and CIII]
emission lines. We used three different techniques to analyse the microlensing
signal. Different components of the lines (narrow, broad and very broad) are
identified and studied. We built a library of simulated microlensing
lightcurves that reproduce the signal observed in the continuum and in the
lines provided only the source size is changed. A Bayesian analysis scheme is
then developed to derive the size of the various components of the BLR.
Results: 1. The half-light radius of the region emitting the CIV line is
found to be R_CIV ~ 66^{+110}_{-46} lt-days = 0.06$^{+0.09}_{-0.04}$ pc =
1.7$^{+2.8}_{-1.1}$\,10$^{17}$ cm (at 68.3% CI). Similar values are obtained
for CIII]. Relative sizes of the carbon-line and V-band continuum
emitting-regions are also derived with median values of R(line)/R(cont) in the
range 4 to 29, depending of the FWHM of the line component.
2. The size of the CIV emitting region agrees with the Radius-Luminosity
relationship derived from reverberation mapping. Using the virial theorem we
derive the mass of the black hole in Q2237+0305 to be M_BH ~ 10^{8.3+/-0.3}
M_sun.
3. We find that the CIV and CIII] lines are produced in at least 2 spatially
distinct regions, the most compact one giving rise to the broadest component of
the line. The broad and narrow line profiles are slightly different for CIV and
CIII].
4. Our analysis suggests a different structure for the CIV and FeII+III
emitting regions, with the latter produced in the inner part of the BLR or in a
less extended emitting region than CIV.
12/2010;
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Dominique Bockelee-Morvan,
N. Biver,
J. Crovisier,
M. de Val-Borro,
T. Fulton,
P. Hartogh, D. Hutsemékers,
C. Jarchow,
E. Jehin,
M. Kidger,
M. Kueppers,
E. Lellouch,
D. Lis,
J. Manfroid,
R. Moreno,
M. Rengel,
B. C. Swinyard,
S. Szutowicz,
B. Vandenbussche,
HssO Team
[show abstract]
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ABSTRACT: The distant comet 29P/Schwassmann-Wachmann was observed with the HIFI,
PACS and SPIRE instruments aboard the Herschel Space Observatory, as
part of the guaranteed time key programme "Water and related chemistry
in the Solar System" (KP-GT HssO). Supporting observations of the 230
GHz CO line were carried out with the IRAM 30-m telescope. The HIFI
observations of the 557 GHz H2O line were performed on 19.05 April 2010,
about 2 days after a major outburst, and on 11.02 May 2010, when 29P was
in a more quiescent phase. H2O was detected on both dates with a
production rate corresponding to about 1/10th the CO production,
assuming near-nucleus production. The H2O line shape is consistent with
release of water vapour from icy grains. PACS and SPIRE imaging data
from 70 to 500 micrometers were acquired mid-June 2010 when the comet
was in a quiescent phase. The continuum emission detected in the
70-μm and 160-μm PACS images is weakly extended with respect to
the PSF, suggesting a major contribution from the nucleus or from slowly
moving large grains.
09/2010; 42:946.
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ABSTRACT: We present new optical circular polarization measurements with typical uncertainties < 0.1% for a sample of 21 quasars. All but two objects have null circular polarization. We use this result to constrain the polarization due to photon-pseudoscalar mixing along the line of sight. We detect significant (> 3 sigma) circular polarization in two blazars with high linear polarization and discuss the implications of this result for quasar physics. In particular, the recorded polarization degrees may be indicative of magnetic fields as strong as 1 kG or a significant contribution of inverse Compton scattering to the optical continuum. Comment: Accepted for publication in Astronomy and Astrophysics Letters
09/2010;
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M. de Val-Borro,
P. Hartogh,
J. Crovisier,
D. Bockelée-Morvan,
N. Biver,
D. C. Lis,
R. Moreno,
C. Jarchow,
M. Rengel,
S. Szutowicz, [......],
N Thomas,
C. Waelkens,
R. Szczerba,
P. Saraceno,
A. M. di Giorgio,
S. Philipp,
T Klein,
V. Ossenkopf,
P. Zaal,
R. Shipman
[show abstract]
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ABSTRACT: The high spectral resolution and sensitivity of Herschel/HIFI allows for the detection of multiple rotational water lines and accurate determinations of water production rates in comets. In this letter we present HIFI observations of the fundamental 110-101 (557 GHz) ortho and 111-000 (1113 GHz) para rotational transitions of water in comet 81P/Wild 2 acquired in February 2010. We mapped the extent of the water line emission with five point scans. Line profiles are computed using excitation models which include excitation by collisions with electrons and neutrals and solar infrared radiation. We derive a mean water production rate of $1.0 \times 10^{28}$ molecules s$^{-1}$ at a heliocentric distance of 1.61 AU about 20 days before perihelion, in agreement with production rates measured from the ground using observations of the 18-cm OH lines. Furthermore, we constrain the electron density profile and gas kinetic temperature, and estimate the coma expansion velocity by fitting the water line shapes. Comment: Accepted for publication in A&A (special issue on HIFI first results)
07/2010;
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D. Bockelée-Morvan,
P. Hartogh,
J. Crovisier,
B. Vandenbussche,
B. M. Swinyard,
N. Biver,
D. C. Lis,
C. Jarchow,
R. Moreno, D. Hutsemékers, [......],
J. A. D. L. Blommaert,
J. Cernicharo,
L. Decin,
P. Encrenaz,
T. de Graauw,
S. Leeks,
A. S. Medvedev,
D. Naylor,
R. Schieder,
N Thomas
[show abstract]
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ABSTRACT: Comet C/2006 W3 (Christensen) was observed in November 2009 at 3.3 AU from the Sun with Herschel. The PACS instrument acquired images of the dust coma in 70- and 160-micrometers filters, and spectra covering several H2O rotational lines. Spectra in the range 450-1550 GHz were acquired with SPIRE. The comet emission continuum from 70 to 672 micrometers was measured, but no lines were detected. The spectral energy distribution indicates thermal emission from large particles and provides a measure of the size distribution index and dust production rate. The upper limit to the water production rate is compared to the production rates of other species (CO, CH3OH, HCN, H2S, OH) measured with the IRAM 30-m and Nancay telescopes. The coma is found to be strongly enriched in species more volatile than water, in comparison to comets observed closer to the Sun. The CO to H2O production rate ratio exceeds 220%. The dust to gas production rate ratio is on the order of 1. Comment: Accepted for publication in Astronomy & Astrophysics (special issue on Herschel first results)
05/2010;
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ABSTRACT: Our aim is to determine the isotopic ratios {$^{12}$C/$^{13}$C}{} and {$^{14}$N/$^{15}$N}{} in a variety of comets and link these measurements to the formation and evolution of the solar system. The {$^{12}$C/$^{13}$C}{} and {$^{14}$N/$^{15}$N}{} isotopic ratios are measured {for} the CN radical by means of high-resolution optical spectra of the R branch of the B-X (0,0) violet band. {23 comets from different dynamical classes} have been observed, sometimes at various heliocentric {and nucleocentric} distances, in order to estimate possible variations of the isotopic ratios in parent molecules. The {$^{12}$C/$^{13}$C}{} and {$^{14}$N/$^{15}$N}{} isotopic ratios in CN are remarkably constant (average values of, respectively, $91.0\pm3.6$ and $147.8\pm5.7$) within our measurement errors, for all comets whatever their origin or heliocentric distance. While the carbon isotopic ratio does agree with the terrestrial value (89), the nitrogen ratio is a factor of two lower than the terrestrial value (272), indicating a fractionation in the early solar system, or in the protosolar nebula, common to all the comets of our sample. This points towards a common origin of the comets independently of their birthplaces, and a relationship between HCN and CN. Comment: 54 pages
07/2009;
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ABSTRACT: High-resolution (R ~ 60,000) spectra of the CN B 2Σ+-X 2Σ+ (0, 0) band (near 3880 Å) in the Halley-type comet 122P/1995 S1 de Vico (with a period of 74 yr) and the "intermediate-period" comet 153P/2002 C1 Ikeya-Zhang (P ~ 370 yr) were obtained with the 2dcoudé spectrograph at the 2.7 m Harlan J. Smith telescope of the McDonald Observatory. The comets were within 1 AU from the Sun (0.66 and 0.92 AU, respectively) at the time of the observations. While the measured 12C/13C isotope ratios of both comets (90 ± 10 and 90 ± 25, respectively) are in very good agreement with the solar system value, the 14N/15N ratios (140 ± 20 and 170 ± 50, respectively) are approximately half the value in Earth's atmosphere. The similarity is striking between these ratios and those obtained recently for two other long-period Oort Cloud comets, C/1995 O1 (Hale-Bopp) and C/2000 WM1 (LINEAR). While these optical determinations of 14N/15N are consistent with each other, they disagree with those obtained in comet Hale-Bopp from submillimeter measurements of HCN, generally believed to be the main parent of CN. This puzzling difference points toward the existence of (an)other unknown parent(s) of CN, with an even higher 15N excess. Organic compounds like those found in interplanetary dust particles are good candidates.
The Astrophysical Journal 12/2008; 613(2):L161. · 6.02 Impact Factor
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D. Bockelée-Morvan,
N. Biver,
E. Jehin,
A. L. Cochran,
H. Wiesemeyer,
J. Manfroid, D. Hutsemékers,
C. Arpigny,
J. Boissier,
W. Cochran,
P. Colom,
J. Crovisier,
N. Milutinovic,
R. Moreno,
J. X. Prochaska,
I. Ramirez,
R. Schulz,
and J.-M. Zucconi
[show abstract]
[hide abstract]
ABSTRACT: From millimeter and optical observations of the Jupiter-family comet 17P/Holmes performed soon after its huge outburst of 2007 October 24, we derive 14N/15N = 139 ± 26 in HCN and 14N/15N = 165 ± 40 in CN, establishing that HCN has the same nonterrestrial isotopic composition as CN. The same conclusion is obtained for the long-period comet C/1995 O1 (Hale-Bopp) after a reanalysis of previously published measurements. These results are compatible with HCN being the prime parent of CN in cometary atmospheres. The15N excess relative to the Earth's atmospheric value indicates that N-bearing volatiles in the solar nebula underwent important N isotopic fractionation at some stage of solar system formation. HCN molecules never isotopically equilibrated with the main nitrogen reservoir in the solar nebula before being incorporated in Oort Cloud and Kuiper Belt comets. The 12C/13C ratios in HCN and CN are measured to be consistent with the terrestrial value.
The Astrophysical Journal 12/2008; 679(1):L49. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We investigate correlations between the direction of the optical linear polarization and the orientation of the host galaxy/extended emission for type1 and type2 radio-loud and radio-quiet quasars. We have used high resolution Hubble Space Telescope data and a deconvolution process to obtain a good determination of the host galaxy/extended emission (EE) position angle. With these new measurements and a compilation of data from the literature, we find a significant correlation, different for type1 and type2 objects, between the linear polarization position angle and the orientation of the EE, suggesting scattering by an extended UV/blue region in both types of objects. Our observations support the extension of the Unification Model to the higher luminosity AGNs like the quasars, assuming a two component scattering model.
10/2008;
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[hide abstract]
ABSTRACT: We present the main results of the first long-term spectrophotometric monitoring of the ``Einstein cross'' Q2237+0305 and of the single-epoch spectra of the lensed quasar J1131-1231. From October 2004 to December 2006, we find that two prominent microlensing events affect images A & B in Q2237+0305 while images C & D remain grossly unaffected by microlensing on a time scale of a few months. Microlensing in A & B goes with chromatic variations of the quasar continuum. We observe stronger micro-amplification in the blue than in the red part of the spectrum, as expected for continuum emission arising from a standard accretion disk. Microlensing induced variations of the CIII] emission are observed both in the integrated line intensity and profile. Finally, we also find that images C & D are about 0.1-0.3 mag redder than images A & B. The spectra of images A-B-C in J1131-1231 reveal that, in April 2003, microlensing was at work in images A and C. We find that microlensing de-amplifies the continuum emission and the Broad Line Region (BLR) in these images. Contrary to the case of Q2237+0305, we do not find evidence for chromatic microlensing of the continuum emission. On the other hand, we observe that the Balmer and MgII broad line profiles are deformed by microlensing. These deformations imply an anti-correlation between the width of the emission line and the size of the corresponding emitting region. Finally, the differential microlensing of the FeII emission suggests that the bulk of FeII is emitted in the outer parts of the BLR while another fraction of FeII is produced in a compact region.
10/2008;
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[hide abstract]
ABSTRACT: The host galaxies of six nearby QSOs are studied on the basis of high resolution HST optical images and spatially resolved VLT slit spectra. The gas ionization and velocity are mapped as a function of the distance to the central QSO. In the majority of the cases, the QSO significantly contributes to the gas ionization in its whole host galaxy, and sometimes even outside. Reflection or scattering of the QSO \ha line from remote regions of the galaxy is detected in several instances. The line shifts show that, in all cases, the matter responsible for the light reflection moves away from the QSO, likely accelerated by its radiation pressure. The two faintest QSOs reside in spirals, with some signs of a past gravitational perturbation. One of the intermediate luminosity QSOs resides in a massive elliptical containing gas ionized (and probably pushed away) by the QSO radiation. The other medium-power object is found in a spiral galaxy displaying complex velocity structure, with the central QSO moving with respect to the bulge, probably as a result of a galactic collision. The two most powerful objects are involved in violent gravitational interactions and one of them has no detected host. These results suggest that (1) large-scale phenomena, such as galactic collisions, are closely related to the triggering and the feeding of the QSO and (2) once ignited, the QSO has significant influence on its large-scale neighborhood (often the whole host and sometimes further away). Comment: Accepted for publication in ApJ. 31 pages, 17 figures, 3 tables
02/2008;
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[hide abstract]
ABSTRACT: For Seyfert galaxies, the AGN unification model provides a simple and well established explanation of the Type 1/Type 2 dichotomy through orientation based effects. The generalization of this unification model to the higher luminosity AGNs that are the quasars remains a key question. The recent detection of Type 2 Radio-Quiet quasars seems to support such an extension. We propose to further test this scenario. On the basis of a compilation of quasar host galaxy position angles consisting of previously published data and of new measurements performed using HST Archive images, we investigate the possible existence of a correlation between the linear polarization position angle and the host galaxy/extended emission position angle of quasars. We find that the orientation of the rest-frame UV/blue extended emission is correlated to the direction of the quasar polarization. For Type 1 quasars, the polarization is aligned with the extended UV/blue emission while these two quantities are perpendicular in Type 2 objects. This result is independent of the quasar radio-loudness. We interpret this (anti-)alignment effect in terms of scattering in a two-component polar+equatorial model which applies to both Type 1 and Type 2 objects. Moreover the orientation of the polarization -and then of the UV/blue scattered light- does not appear correlated to the major axis of the stellar component of the host galaxy measured from near-IR images. Comment: 14 pages, 6 figures, accepted for publication in A&A
10/2007;
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[show abstract]
[hide abstract]
ABSTRACT: (ABRIDGED) Aims: We discuss and characterize micro-lensing among the 3 brightest lensed images (A-B-C) of the gravitational lens system RXS J1131-1231 (a quadruply imaged AGN) by means of long slit optical and NIR spectroscopy. Qualitative constraints on the size of different emission regions are derived. Methods: We decompose the spectra into their individual emission components using a multi-component fitting approach. A complementary decomposition of the spectra enables us to isolate the macro-lensed fraction of the spectra independently of any spectral modelling. Results: -1. The data support micro-lensing de-amplification of images A and C. Not only is the continuum emission microlensed in those images but also a fraction of the Broad Line emitting Region (BLR).-2. Micro-lensing of a very broad component of MgII emission line suggests that the corresponding emission occurs in a region more compact than the other components of the emission line. -3. We find evidence that a large fraction of the FeII emission arises in the outer parts of the BLR. We also find very compact emitting region in the ranges 3080-3540 A and 4630-4800 A that is likely associated with FeII. -4. The OIII narrow emission line regions are partly spatially resolved. This enables us to put a lower limit of 110h^{-1} pc on their intrinsic size. -5. Analysis of MgII absorption found in the spectra indicates that the absorbing medium is intrinsic to the quasar, has a covering factor of 20%, and is constituted of small clouds homogeneously distributed in front of the continuum and BLRs. -6. Two neighbour galaxies are detected at redshifts z=0.10 and z=0.289. These galaxies are possible members of galaxy groups reported at those redshifts. Comment: Accepted by Astronomy and Astrophysics. Small modifications to match the final version
03/2007;
