References of "Hutsemekers, Damien"
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See detailMicrolensing probes the AGN structure of the lensed quasar J1131-1231
Sluse, Dominique; Claeskens, Jean-François ULg; Hutsemekers, Damien ULg et al

in Benítez, E.; Cruz-González, I.; Krongold, Y. (Eds.) Revista Mexicana de Astronomia y Astrofisica (Serie de Conferencias) Vol. 32 (2008, April 01)

We present the analysis of single epoch long slit spectra of the three brightest images of the gravitationally lensed system J1131-1231. These spectra provide one of the clearest observational evidence ... [more ▼]

We present the analysis of single epoch long slit spectra of the three brightest images of the gravitationally lensed system J1131-1231. These spectra provide one of the clearest observational evidence for differential micro-lensing of broad emission lines (BELs) in a gravitationally lensed quasar. The micro-lensing effect enables us: (1) to confirm that the width of the emission lines is anti-correlated to the size of the emitting region; (2) to show that the bulk of Fe II is emitted in the outer parts of the Broad Line Region (BLR) while another fraction of Fe II is produced in a compact region; (3) to derive interesting informations on the origin of the narrow intrinsic Mg II absorption doublet observed in that system. [less ▲]

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See detailAxions and polarisation of quasars
Payez, Alexandre ULg; Cudell, Jean-René ULg; Hutsemekers, Damien ULg

in AIP Conference Proceedings (2008), 1038

We present results showing that, thanks to axion-photon mixing in external magnetic fields, it is actually possible to produce an effect similar to the one needed to explain the large-scale coherent ... [more ▼]

We present results showing that, thanks to axion-photon mixing in external magnetic fields, it is actually possible to produce an effect similar to the one needed to explain the large-scale coherent orientations of quasar polarisation vectors in visible light that have been observed in some regions of the sky. [less ▲]

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See detailNitrogen Isotope Ratios in Comets. ESO Astrophysics Symposia
Cochran, Anita L; Jehin, Emmanuel ULg; Manfroid, Jean ULg et al

in Precision Spectroscopy in Astrophysics (2008)

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See detailQuasar Host Orientation and Polarization: Insights into the Type 1/Type 2 Dichotomy
Borguet, Benoît ULg; Hutsemekers, Damien ULg; Letawe, Géraldine ULg et al

in Revista Mexicana de Astronomía y Astrofísica (2008), 32

We investigate correlations between the optical linear polarization position angle and the orientation of the host galaxy/extended emission of Type 1 and Type 2 Radio-Loud (RL) and Radio-Quiet (RQ ... [more ▼]

We investigate correlations between the optical linear polarization position angle and the orientation of the host galaxy/extended emission of Type 1 and Type 2 Radio-Loud (RL) and Radio-Quiet (RQ) quasars. We have used high resolution Hubble Space Telescope (HST) data and deconvolution process to obtain a good determination of the host galaxy orientation. With these new measurements and a compilation of data from the literature, we find a significant correlation between the polarization position angle and the position angle of the major axis of the host galaxy/extended emission. The correlation appears different for Type 1 and Type 2 objects and depends on the redshift of the source. Interpretations in the framework of the unification model are discussed. [less ▲]

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See detailMicrolensing to probe the quasar structure: spectrophotometry of Q2237+0305 and of J1131-1231
Sluse, Dominique; Eigenbrod, A.; Courbin, F. et al

in Kerins, E.; Mao, S.; Rattenbury, N. (Eds.) et al Proceedings of the Manchester Microlensing Conference: The 12th International Conference and ANGLES Microlensing Workshop. Proceedings of Science, PoS (GMC8)020 (2008)

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 ... [more ▼]

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. [less ▲]

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See detailEvidence of a type 1/type 2 dichotomy in the correlation between quasar optical polarization and host-galaxy/extended emission position angles
Borguet, Benoît ULg; Hutsemekers, Damien ULg; Letawe, Géraldine ULg et al

in Astronomy and Astrophysics (2008), 478

Aims.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 ... [more ▼]

Aims.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 quasars are remains a key question. The recent detection of type 2 radio-quiet quasars seems to support such an extension. We propose a further test of this scenario. Methods: 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. Results: 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 that 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. [less ▲]

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See detailStudy of the QSO HE0354-5500 with combined HST imaging and VLT spectroscopy . An example of a deconvolution-based method for probing the QSOs host galaxies characteristics
Letawe, Yannick ULg; Magain, Pierre ULg; Letawe, Géraldine ULg et al

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (2008), 79

The host galaxy of the QSO HE0354-5500 (M_B=-24.7, z=0.2674) is studied on the basis of high resolution HST optical images and spatially resolved VLT slit spectra. The morphology and dynamics of the host ... [more ▼]

The host galaxy of the QSO HE0354-5500 (M_B=-24.7, z=0.2674) is studied on the basis of high resolution HST optical images and spatially resolved VLT slit spectra. The morphology and dynamics of the host are described. The gas ionization and velocity are mapped as a function of the distance to the central QSO. Reflection or scattering of the QSO Halpha line from remote regions of the galaxy is detected. The line shifts show that the matter responsible for the light reflection moves away from the QSO, likely accelerated by its radiation pressure. Moreover, different resolved emission regions are found in the central kpc, both in the images and the spectra. [less ▲]

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See detailOptical Observations of Comet McNaught from La Silla
Snodgrass, C.; Fitzsimmons, A.; Jehin, Emmanuel ULg et al

in LPI contribution 1405 (2008)

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See detailOptical Spectroscopy of the B and C Fragments of Comet 73P/Schwassmann-Wachmann 3 at the ESO VLT
Jehin, Emmanuel ULg; Manfroid, Jean ULg; Kawakita, H. et al

in LPI contribution 1405 (2008)

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See detailA Multi-Wavelength Simultaneous Study of the Composition of the Halley-Family Comet 8P/Tuttle at the VLT
Bockelée-Morvan, Dominique; Dello Russo, N.; Jehin, Emmanuel ULg et al

in LPI contribution 1405 (2008)

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See detailA Fluorescence Model for 12C13C in Comets
Rousselot, P.; Jehin, Emmanuel ULg; Manfroid, Jean ULg et al

in LPI contribution 1405 (2008)

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See detailCarbon and Nitrogen Isotopic Ratios in Comets
Jehin, Emmanuel ULg; Manfroid, Jean ULg; Hutsemekers, Damien ULg et al

in LPI contribution 1405 (2008)

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See detailUnderstanding the relations between QSOs and their host galaxies from combined HST imaging and VLT spectroscopy
Letawe, Yannick ULg; Magain, Pierre ULg; Letawe, Géraldine ULg et al

in Astrophysical Journal (2008), 679(2), 967-983

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 ... [more ▼]

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 H alpha 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). [less ▲]

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See detailQSO Type1/Type2 dichotomy (Borguet+, 2008)
Borguet, Benoît ULg; Hutsemekers, Damien ULg; Letawe, Géraldine ULg et al

Textual, factual or bibliographical database (2007)

This table contains the measurements/compilation of host galaxy/ extended emission position angle in the visible and near-IR domain, polarimetric data, and radio axis orientation for the 135 quasars of ... [more ▼]

This table contains the measurements/compilation of host galaxy/ extended emission position angle in the visible and near-IR domain, polarimetric data, and radio axis orientation for the 135 quasars of our sample. The angles are given in degrees east of north. The table gives the spectral and the radio-loud/radio-quiet classification of each object according to the references. (2 data files). [less ▲]

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See detailCircular Polarimetry Now Offered at EFOSC2
Saviane, Ivo; Piirola, Vilppu; Bagnulo, Stefano et al

in The Messenger (2007), 129

Starting from period P79, circular polarimetry measurements can be carried out with EFOSC2 at the ESO 3.6-m telescope. Here we describe the motivations behind the upgrade of the instrument, and a few ... [more ▼]

Starting from period P79, circular polarimetry measurements can be carried out with EFOSC2 at the ESO 3.6-m telescope. Here we describe the motivations behind the upgrade of the instrument, and a few results from the commissioning runs are used to show the excellent performance of the new polarimetry unit. [less ▲]

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See detailAcceleration and Substructure Constraints in a Quasar Outflow
Hall, Patrick B; Sadavoy, Sarah I; Hutsemekers, Damien ULg et al

in Astrophysical Journal (2007), 665

We present observations of probable line-of-sight acceleration of a broad absorption trough of C IV in the quasar SDSS J024221.87+004912.6. We also discuss how the velocity overlap of two other outflowing ... [more ▼]

We present observations of probable line-of-sight acceleration of a broad absorption trough of C IV in the quasar SDSS J024221.87+004912.6. We also discuss how the velocity overlap of two other outflowing systems in the same object constrains the properties of the outflows. The Si IV doublet in each system has one unblended transition and one transition that overlaps with absorption from the other system. The residual flux in the overlapping trough is well fit by the product of the residual fluxes in the unblended troughs. For these optically thick systems to yield such a result, at least one of them must consist of individual subunits, rather than being a single structure with velocity-dependent coverage of the source. If these subunits are identical, opaque, spherical clouds, we estimate the cloud radius to be r~=3.9×10[SUP]15[/SUP] cm. If they are identical, opaque, linear filaments, we estimate their width to be w~=6.5×10[SUP]14[/SUP] cm. These subunits are observed to cover the Mg II broad emission-line region of the quasar, at which distance from the black hole the above filament width is equal to the predicted scale height of the outer atmosphere of a thin accretion disk. Insofar as that scale height is a natural size scale for structures originating in an accretion disk, these observations are evidence that the accretion disk can be a source of quasar absorption systems. This paper is based on data from ESO program 075.B-0190(A). [less ▲]

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See detailMulti-wavelength study of the gravitational lens system RXS J1131-1231 - III. Long slit spectroscopy: micro-lensing probes the QSO structure
Sluse, Dominique; Claeskens, Jean-François ULg; Hutsemekers, Damien ULg et al

in Astronomy and Astrophysics (2007), 468(3), 885-901

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 ... [more ▼]

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. We also perform a spectroscopic study of two field galaxies located within 1.6 arcmin radius from the lens. 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 Mg II 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 Fe II emission arises in the outer parts of the BLR. We also find a very compact emitting region in the ranges 3080-3540 angstrom and 4630-4800 angstrom that is likely associated with Fe II. 4. The [O III] narrow emission line regions are partly spatially resolved. This enables us to put a lower limit of similar to 110h(-1) pc on their intrinsic size. 5. Analysis of Mg II 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. [less ▲]

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See detailNuclear spin temperature of ammonia in Comet 9P/Tempel 1 before and after the Deep Impact event
Kawakita, Hideyo; Jehin, Emmanuel ULg; Manfroid, Jean ULg et al

in Icarus (2007), 187

The Deep Impact mission succeeded in excavating inner materials from the nucleus of Comet 9P/Tempel 1 on 2005 July 04 (at 05:52 UT). Comet 9P/Tempel 1 is one of Jupiter family short period comets, which ... [more ▼]

The Deep Impact mission succeeded in excavating inner materials from the nucleus of Comet 9P/Tempel 1 on 2005 July 04 (at 05:52 UT). Comet 9P/Tempel 1 is one of Jupiter family short period comets, which might originate in the Kuiper belt region in the solar nebula. In order to characterize the comet and to support the mission from the ground-based observatory, optical high-dispersion spectroscopic observations were carried out with the echelle spectrograph (UVES) mounted on the 8-m telescope VLT (UT2) before and after the Deep Impact event. Ortho-to-para abundance ratios (OPRs) of cometary ammonia were determined from the NH[SUB]2[/SUB] emission spectra. The OPRs of ammonia on July 3.996 UT and 4.997 UT were derived to be 1.28±0.07 (nuclear spin temperature: T[SUB][/SUB]=24±2 K) and 1.26±0.08 (T[SUB][/SUB]=25±2 K), respectively. There is no significant change between before and after the impact. Actually, most materials ejected from the impact site could have moved away from the nucleus on July 4.997 UT, about 17 h after the impact. However, a small fraction of the ejected materials might remain in the slit of UVES instrument at that time because an excess of about 20% in the NH[SUB]2[/SUB] emission flux is observed above the normal activity level was found [Manfroid, J., Hutsemékers, D., Jehin, E., Cochran, A.L., Arpigny, C., Jackson, W.M., Meech, K.J., Schulz, R., Zucconi, J.-M., 2007. Icarus. This issue]. If the excess of NH[SUB]2[/SUB] on July 04.997 UT was produced from icy materials excavated by the Deep Impact, then an upper-limit of the ammonia OPR would be 1.75 (T[SUB][/SUB]>17 K) for those materials. On the other hand, the OPR of ammonia produced from the quiescent sources was similar to that of the Oort cloud comets observed so far. This fact may imply that physical conditions where cometary ices formed were similar between Comet 9P/Tempel 1 and the Oort cloud comets. [less ▲]

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See detailThe impact and rotational light curves of Comet 9P/Tempel 1
Manfroid, Jean ULg; Hutsemekers, Damien ULg; Jehin, Emmanuel ULg et al

in Icarus: International Journal of Solar System Studies (2007), 187

UVES and HIRES high-resolution spectra of Comet 9P/Tempel 1 are used to investigate the impact and rotational light curves of various species with a view toward building a simple model of the distribution ... [more ▼]

UVES and HIRES high-resolution spectra of Comet 9P/Tempel 1 are used to investigate the impact and rotational light curves of various species with a view toward building a simple model of the distribution and activity of the sources. The emission by OH, NH, CN, C[SUB]3[/SUB], CH, C[SUB]2[/SUB], NH[SUB]2[/SUB], and OI, are analyzed, as well as the light scattered by the dust. It is found that a simple model reproduces fairly well the impact light curves of all species combining the production of the observed molecules and the expansion of the material throughout the slit. The impact light curves are consistent with velocities of 400 600 m/s. Their modeling requires a three-step dissociation sequence ``Grand-Parent --> Parent --> Daughter'' to produce the observed molecules. The rotational light curve for each species is explained in terms of a single model with three sources. The dust component can however not easily be explained that way. [less ▲]

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See detailComet C/2006 P1 (McNaught)
Jehin, Emmanuel ULg; Manfroid, Jean ULg; Snodgrass, C. et al

in Central Bureau Electronic Telegrams (CBETs) (2007), 832

CBET 832 available at Central Bureau for Astronomical Telegrams.

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