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Commissioning of the Dual-Beam Imaging Polarimeter for the University of Hawaii 88 inch Telescope
In this paper we present the design, calibration method, and initialresults of the Dual-Beam Imaging Polarimeter (DBIP). This new instrumentis designed to measure the optical polarization properties of pointsources, in particular, Main Belt asteroids. This instrument interfacesbetween the Tek 2048×2048 camera and the University of Hawaii's 88inch telescope and is available for facility use. Using DBIP we are ableto measure linear polarization with a 1 σ Poisson signal noise of0.03% per measurement and a systematic error of order 0.06%+/-0.02%. Inaddition, we discuss measurements of the polarization of the asteroid 16Psyche that were taken as part of the instrument commissioning. Weconfirm Psyche's negative polarization of -1.037%+/-0.006% but find nosignificant modulation of the signal with rotation above the 0.05%polarization level.
| Infrared polarimetry of the microquasars H1743-322, XTE J1550-564 and GRO J1655-40
Aims.The optical/IR emission from X-ray binaries can be intrinsicallypolarised because of light scattered within the system or because thereis significant synchrotron emission at high frequencies from a compactjet. We report on polarised light observations of three microquasars(X-ray binaries with radio jets). Methods: .Ks bandpolarimetric observations were obtained at the ESO NTT using SOFI. Thelinear polarisation of the three systems is derived relative to that ofother stars in the field-of-view, so as to distinguish intrinsicpolarisation from interstellar polarisation. Results: .H1743-322was observed in outburst in 2003 and 2004. We measure a linearpolarisation of 2.25 ± 0.75% comparable to that of other nearbystars. The polarisation is very likely interstellar, consistent with thelarge extinction (A_V≈ 11) along the line-of-sight. GRO J1655-40 wasobserved in quiescence and shows no evidence for intrinsic polarisation.XTE J1550-564 was observed during a weak X-ray outburst. It shows ahigher polarisation (at the 2.5σ level) than neighbouring starswithin 1'. Further studies are needed to establish the nature of thispossible intrinsic polarisation.
| The NICMOS Polarimetric Calibration
An accurate knowledge of the absolute calibration of the polarizingelements in the Near Infrared Camera and Multi-Object Spectrometer(NICMOS) becomes especially important when conducting studies thatrequire measuring degrees of polarization of close to 1% in thenear-infrared. We present a comprehensive study of all previouslyobserved polarimetric standards using the NIC2 camera on NICMOS.Considering both pre- and post-NICMOS Cooling System observations, wefind variations in the polarimetry consistent with the effects ofsubpixel misalignments and the point-spread function. We also measurenonzero results from unpolarized standards, indicating an instrumentalpolarization of p~1.2%, θ~88deg. The lack of polarizedand unpolarized standard stars with which to perform a comprehensivecalibration study means that we cannot be confident that the currentcalibration will be effective for a number of recent large NICMOS GOprograms. Further observations of polarimetric standards are needed inorder to fully characterize the behavior of NICMOS at around p=1%.Based on observations made with the NASA/ESA Hubble Space Telescopeobtained at the Space Telescope Science Institute, which is operated bythe Association of Universities for Research in Astronomy, Incorporated,under NASA contract NAS 5-26555.
| The infrared void in the Lupus dark clouds revisited: a polarimetric approach
The results of B-band CCD imaging linear polarimetry obtained for starsfrom the Hipparcos catalogue are used to re-examine the distribution ofthe local interstellar medium towards the IRAS 100-μm emission voidin the Lupus dark clouds. The analysis of the obtainedparallax-polarization diagram assigns to the dark cloud Lupus1 adistance between 130 and 150pc and assures the existence of a low columndensity region coincident with the observed infrared void. Moreover,there are clear indications of the existence of absorbing material atdistances closer than 60-100pc, which may be associated with theinterface boundary between the Local Bubble and its neighbourhood LoopIsuperbubble.
| New optical polarization measurements of quasi-stellar objects. The data
New linear polarization measurements (mainly in the V band) arepresented for 203 quasi-stellar objects (QSOs). The sample is made up of94 QSOs located in the North Galactic Pole (NGP) region and of 109 QSOsin the South Galactic Pole (SGP) region. First time measurements havebeen obtained for 184 QSOs. Among them, 109 known radio-emitters, 42known Broad Absorption Line (BAL) QSOs, and 1 gravitationally lensedquasi-stellar object. We found high polarization levels (p > 3%) for12 QSOs, including the BAL QSO SDSS J1409+0048. For10 objects, measurements obtained at different epochs do exist. Two ofthem show evidence for variability: the highly polarized BL Laccandidate PKS 1216-010 and the radio sourcePKS 1222+037.Based on observations collected at the European Southern Observatory(ESO, La Silla and Paranal). Table 4 is only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/433/757
| VLT spectropolarimetry of two powerful radio galaxies at z ~ 1.4: ultraviolet continuum, emission-line properties and the nature of high-redshift dust
Deep spectropolarimetric observations, obtained with the Very LargeTelescope, are presented for two powerful radio galaxies, 0850-206 (z =1.3373) and 1303+091 (z = 1.4093). These observations cover therest-frame wavelength range ~1450-3750 Å. New radio observationsand continuum images of the same sources are also presented. Thesegalaxies are the first two observed from a complete sample of nine radiosources with redshifts in the range 1.3 <= z <= 1.5 (selected fromthe equatorial sample of powerful radio sources of Best, Röttgering& Lehnert), as part of a project aimed to investigate themulticomponent nature of the ultraviolet (UV) continuum in radiogalaxies and, in particular, any variations of the continuum propertieswith the radio source age.The larger radio source of the two, 0850-206, presents a high continuumfractional polarization, averaging 17 per cent across the observedwavelength range and reaching 24 per cent at rest-frame wavelengths of<~2000 Å. The smaller radio source, 1303+091, shows a lowercontinuum polarization, averaging 8 per cent and rising to 11 per centfor rest-frame wavelengths >~3000 Å. For both galaxies, theposition angle of the electric vector is generally constant withwavelength and within ~15° of perpendicular to the radio axis. Boththeir total flux spectra and polarized flux spectra reveal the2200-Ådust feature, and comparison with dust scattering modelssuggests that the composition of the dust in these galaxies is similarto that of Galactic dust. In 0850-206, scattered quasar radiationdominates the UV continuum emission, with the nebular continuumaccounting for no more than ~22 per cent and no requirement for anyadditional emission component such as emission from young stars. Incontrast, in 1303+091, unpolarized radiation could be a majorconstituent of the UV continuum emission, with starlight accounting forup to ~50 per cent and the nebular continuum accounting for ~11 percent.The emission-line properties of the galaxies are also studied from theirtotal intensity spectra. Comparison of the measured emission-line ratioswith both shock- and photoionization models shows that the nuclear andextended gas in these galaxies is mainly photoionized by the centralactive nucleus.
| Microvariability in the optical polarization of 3C 279
We present results of a microvariability polarization study in theviolently variable quasar 3C279. We have resolved the polarizationcurves in the V band for this object down to timescales of minutes. Wefound two main components in the evolution of the degree of linearpolarization, one consisting of a flicker with timescales of severaltens of minutes and other component with far more significant variationson timescales of a few days. The linear polarization descended from ~17% down to ~ 8% in three nights. The polarization angle underwent asudden change of more that 10 degrees in a few hours, perhaps indicatingthe injection of a new shock in the jet. The amplitude of the intranightflickering in the degree of polarization is at the level of ~ 1%. Theseare probably the best sampled polarization data ever obtained for thisobject. We also performed IR observations and we provide a follow-up ofthe evolution of this source at such energies after the mainpolarization outburst.Based on observations made at the Complejo Astronómico ElLeoncito, which is operated under agreement between CONICET and theNational Universities of La Plata, Córdoba, and San Juan, as wellas at the Laboratório Nacional de Astrofísica, LNA-CNPq,Brazil.}\fnmsep\thanks{Table 2 is only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via \http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/409/857
| Investigating the nature of the z =~ 2.8 submillimeter selected galaxy SMM J02399-0136 with VLT spectropolarimetry
We present deep optical spectropolarimetry of SMM J02399-0136 (z=2.8)done with the VLT Antu 8.2 m telescope equipped with FORS1. Moderatecontinuum and emission line polarization are measured (P ~ 5%). We donot detect broad lines in scattered flux as would be expected for atype-2 object but rather a polarization behaviour similar to BALquasars. This classification is confirmed by the detection of both highand low ionization broad absorption troughs and a very red continuum. Weargue that this object shares several properties with local ULIGs suchas Mrk 231 and other ultraluminous infrared Lo-BAL quasars. However, thefact that the ultraviolet spectrum is dominated by non-stellar radiationdoes not prove that the dust that is thermally radiating in the farinfrared is predominantly heated by the AGN. Since the energy that weget in the far-infrared is precisely that which is removed from theultraviolet spectrum, this could mean that the starburst is moredust-enshrouded than the AGN due to a peculiar dust distribution. Thelimits we place on the putative starburst contribution to the restframeultraviolet continuum together with constraints on the amount ofextinction provide an upper limit to the star formation rate of about2000 Msun yr-1, consistent with previously claimedhigh star formation rates level in this object. Based on observationscollected at the European Southern Observatory, Paranal, Chile (ESOProgramme 64.P-0072).
| High resolution near-infrared polarimetry of eta Carinae and the Homunculus Nebula
High resolution near-infrared adaptive optics imaging and polarimetryhave been obtained of the Homunculus Nebula and its central illuminatingstar eta Carinae (HD 93308). Images and maps of the linear polarizationat a resolution of <0.2'' have been made in the J, H and K bands andin a narrow 2.15 mu m continuum band (K_c). The overall appearance ofthe nebula in the near-IR is similar in all bands and to that at V, withspecific features less sharp to longer wavelengths. A comparison betweenthe published HST WFPC2 1.042 mu m map and the AO J band imagedemonstrates that ground-based AO resolution can approach that of HST.The large-scale pattern of polarization vectors is centro-symmetricdemonstrating that single scattering dominates everywhere except perhapsin the central bright core. The only difference between the near-IR andoptical appearance is a narrow linear feature at position angle320o extending across the NW lobe of the Homunculus.Polarization maps at K_c in the near vicinity of eta Carinae wererestored using a PSF derived from blind deconvolution. There is adefinitely detected extension in the direction of the optically visiblespeckle knots and an estimate of 18% for the polarization of one of theknots was made. This level of polarization suggests that the knots arisein dust+gas clouds in the near environment of eta Carinae, perhaps in anequatorial disc. The most remarkable result of the linear polarizationmapping is the level of similarity in the spatial structure, and also inthe degree of linear polarization, between the near-IR and optical data.Comparison of the polarization along the projected major axis of theHomunculus shows values in the SE lobe to within a few percent from Vband to 2.2 mu m. In the NW lobe the near-IR linear polarization valuesagree to within a few percent over the 1.2-2.2 mu m range, but are upto10% lower than at V. Such a polarization pattern cannot arise in Miescattering from a single power law distribution of grain sizes unlessthe particles are very small compared with the wavelength, indisagreement with mid-IR observations. In addition the colour dependenceof the extinction was found to be shallower than the typical ISM,indicating the presence of large grains. Several possibilities areexplored to try to explain these contradictory results. Optical deptheffects and a broad distribution in grain sizes are favoured, perhapswith a dependence of the grain size with depth into the small obscuringclouds in the lobes of the Homunculus. However the presence of alignedgrains, previously inferred from mid-IR polarization, may also affectthe scattered radiation from the dust.
| Acquisition and analysis of adaptive optics imaging polarimetry data
The process of data taking, reduction and calibration of near-infraredimaging polarimetry data taken with the ESO Adaptive Optics SystemADONIS is described. The ADONIS polarimetric facility is provided by arotating wire grid polarizer. Images were taken at increments of22.5(deg) of polarizer rotation from 0 to 180(deg) , over-sampling thepolarization curve but allowing the effects of photometric variations tobe assessed. Several strategies to remove the detector signature aredescribed. The instrumental polarization was determined, by observationsof stars of negligible polarization, to be 1.7% at J, H and K bands. Thelack of availability of unpolarized standard stars in the IR, inparticular which are not too bright as to saturate current IR detectors,is highlighted. The process of making polarization maps is described.Experiments at restoring polarimetry data, in order to reach diffractionlimited polarization, are outlined, with particular reference to data onthe Homunculus reflection nebula around eta Carinae.
| Examples of high-resolution imaging and polarimetry of R Monocerotis and NGC 2261.
Not Available
| A catalog of far-ultraviolet point sources detected with the fast FAUST Telescope on ATLAS-1
We list the photometric measurements of point sources made by the FarUltraviolet Space Telescope (FAUST) when it flew on the ATLAS-1 spaceshuttle mission. The list contains 4698 Galactic and extragalacticobjects detected in 22 wide-field images of the sky. At the locationssurveyed, this catalog reaches a limiting magnitude approximately afactor of 10 fainter than the previous UV all-sky survey, TDl. Thecatalog limit is approximately 1 x 10-14 ergs A sq cm/s,although it is not complete to this level. We list for each object theposition, FUV flux, the error in flux, and where possible anidentification from catalogs of nearby stars and galaxies. Thesecatalogs include the Michigan HD (MHD) and HD, SAO, the HIPPARCOS InputCatalog, the Position and Proper Motion Catalog, the TD1 Catalog, theMcCook and Sion Catalog of white dwarfs, and the RC3 Catalog ofGalaxies. We identify 2239 FAUST sources with objects in the stellarcatalogs and 172 with galaxies in the RC3 catalog. We estimate thenumber of sources with incorrect identifications to be less than 2%.
| An atlas of Hubble Space Telescope photometric, spectrophotometric, and polarimetric calibration objects
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990AJ.....99.1243T&db_key=AST
| Polarization measurements of 313 nearby stars
The linear polarization of 313 low galactic latitude stars has beenmeasured. With few exceptions all program stars have a spectral typelater than B9 and are within 600 parsec of the sun. 181 stars aresituated at the southern sky and 132 at the northern sky.
| UBV photoelectric photometry in four southern Milky Way fields
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970AJ.....75..324W&db_key=AST
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