J/ApJ/811/67ivo://CDS.VizieR/J/ApJ/811/67doi:10.26093/cds/vizier.18110067CDSHedman M.M.Stark C.C.2017-01-23T22:00:00Z2016-01-20T12:34:34ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frsolar-systemThe appearance of debris disks around distant stars depends upon the scattering/phase function (SPF) of the material in the disk. However, characterizing the SPFs of these extrasolar debris disks is challenging because only a limited range of scattering angles are visible to Earth-based observers. By contrast, Saturn's tenuous rings can be observed over a much broader range of geometries, so their SPFs can be much better constrained. Since these rings are composed of small particles released from the surfaces of larger bodies, they are reasonable analogs to debris disks and so their SPFs can provide insights into the plausible scattering properties of debris disks. This work examines two of Saturn's dusty rings: the G ring (at 167500km from Saturn's center) and the D68 ringlet (at 67600km). Using data from the cameras on board the Cassini spacecraft, we are able to estimate the rings' brightnesses at scattering angles ranging from 170{deg} to 0.5{deg}. We find that both of the rings exhibit extremely strong forward-scattering peaks, but for scattering angles above 60{deg} their brightnesses are nearly constant. These SPFs can be well approximated by a linear combination of three Henyey-Greenstein functions, and are roughly consistent with the SPFs of irregular particles from laboratory measurements. Comparing these data to Fraunhofer and Mie models highlights several challenges involved in extracting information about particle compositions and size distributions from SPFs alone. The SPFs of these rings also indicate that the degree of forward scattering in debris disks may be greatly underestimated.2015ApJ...811...67Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/811/67CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/AJ/149/27 : Cassini ISS astrometry of Saturnian satellites (Cooper+, 2015)J/A+A/575/A73 : Saturnian satellites astrometry (2004-12) (Tajeddine+, 2015)J/AJ/146/12 : Occultations through Starun's C ring (Hedman+, 2013)J/A+A/493/1183 : Saturn major satellites obs. (1874-2007) (Desmars+, 2009)J/AJ/103/983 : Stellar occultation candidates of Saturn (Bosh+, 1992)http://pds-rings.seti.org/cassini/ : Rings node's Cassini home pagehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/811/67https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/811/67http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/811/67https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/811/67https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/811/67http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/811/67GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/ApJ/811/67/table4Normal I/F contrast across the G-ring's inner edge derived from observations at scattering angles below 15 degrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeqObservation Sequenceobs.param;obscharQuad[1/4] Quadrantmeta.codeinttheta[0.8/13] Scattering angle at the ring ({theta})degpos.posAngfloatBCont[4.6/2047] Brightness (I/F) contrast across the G-ring's relatively sharp inner edgephot.flux;arith.ratiofloate_BCont[0.1/47] Uncertainty on Contrast estimated from the errors from two linear fitsstat.errorfloatJ/ApJ/811/67/table1Normal equivalent width estimates for D68 derived from entire images, almost all of which were obtained at scattering angles above 15 degrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintImageImage Nameobs.imagecharETEphemeris Time; seconds past J2000 epochstime.epochdoublethetaScattering angle at the ring ({theta})degpos.posAngfloatB[-43/67] Opening angle of the ring to the spacecraftdegpos.posAngfloatNEW-INT[-0.4/6.6] Normal equivalent width; Integrated Methodmspect.line.eqWidthfloatNEW-FIT[0.1/5.5] Normal equivalent width; Fit Methodmspect.line.eqWidthfloatJ/ApJ/811/67/table2Normal equivalent width estimates for D68 ringlet derived from observations at scattering angles below 15 degrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintImageImage Nameobs.imagecharETEphemeris Time; seconds past J2000 epochstime.epochdoublethetaScattering angle at the ring ({theta})degpos.posAngfloatB[-20/21] Opening angle of the ring to the spacecraftdegpos.posAngfloatMinLon[-50/314] Minimum of Longitude Rangedegpos.framefloatMaxLon[-45/318] Maximum of Longitude Rangedegpos.framefloatNEW-INT[5/10049] Normal equivalent width; Integrated Methodmspect.line.eqWidthdoubleNEW-FIT[5.4/15363] Normal equivalent width; Fit Methodmspect.line.eqWidthdoubleJ/ApJ/811/67/table3Normal I/F contrast across the G-ring's inner edge derived from observations at scattering angles above 15 degrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintImageImage Nameobs.imagecharETEphemeris Time; seconds past J2000 epochstime.epochdoubletheta[17.7/167] Scattering angle at the ring ({theta})degpos.posAngfloatB[-5.1/10] Opening angle of the ring to the spacecraftdegpos.posAngfloatBCont[0.1/3] Brightness (I/F) contrast across the G-ring's relatively sharp inner edgephot.flux;arith.ratiodoublee_BCont[0.003/0.2] Uncertainty on Contrast estimated from the errors from two linear fitsstat.errordouble