J/AJ/157/99ivo://CDS.VizieR/J/AJ/157/99doi:10.26093/cds/vizier.51570099CDSLesser R.W.Moody J.W.Steele J.Bohman J.McNeff M.Joner M.D.,Barnes J.2020-11-04T07:41:05Z2019-06-07T07:18:06ZCDS support team

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

cds-question@unistra.frgalaxiesphotometryseyfert-galaxiesredshiftedline-intensitiesBroadband photometric redshifts are routinely obtained for galaxies to estimate their distances. While effective for many uses, the common resolution in z of 0.01-0.02 is too coarse for detailed large-scale structure mapping, particularly in low-density volumes where the galaxy distribution is least understood. To map galaxies in these low-density volumes, and noting that the percentage of galaxies having emission tends to rise as number density decreases, we have designed a filter system to photometrically measure the redshifts of galaxies with emission. The system consists of two "ramp" filters that cover a common wavelength range with transmission curves sloping from blue to red and from red to blue respectively. This causes the intensity of the image through either filter to be a function of the wavelength of the emission line. A third filter with a bandpass to the side is used to measure and remove the continuum. We have obtained a set of such filters that are tuned for isolating H{alpha} in the redshift range of 3000-9000 km/s. Simulated photometry, applied to spectra of 197 emission-line galaxies from the SDSS, shows the accuracy of the method to be between 250 and 620 km/s, depending on line strength. Actual photometry of a sample of 16 active galaxies measured their redshifts with an accuracy of 573 km/s. This is approximately an order of magnitude more accurate than broadband photometric redshifts. We discuss the errors inherent in this method and present ways to modify the filter set to further improve accuracy.2019AJ....157...99Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/157/99CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/250 : The 2dF Galaxy Redshift Survey (2dFGRS) (2dFGRS Team, 1998-2003)II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)J/ApJS/201/31 : Emission-line galaxies from SDSS. I. (Ge+, 2012)J/MNRAS/421/1043 : Emission-line galaxies from SDSS DR7 (Shirazi+, 2012)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/157/99https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/157/99http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/157/99https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/157/99https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/157/99http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/157/99GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/157/99/table1 (SDSS data used to estimate redshift accuracy)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/157/99/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/157/99/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/157/99/table1?GETtext/xml+votable180.050000true200.004091352.050893840.005555555555555556Cone search capability for table J/AJ/157/99/table2 (Imaged active galaxies)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/157/99/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/157/99/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/157/99/table2?GETtext/xml+votable180.050000true219.342258936.56785190.0055555555555555565/2608 2613 6/7947 8230 8922 9126 9127 9132 9133 9136 9146 9147 10207 10329 10332 10333 10334 10349 10351 10354 10361 10363 10365 10366 10367 10391 10397 10436 10438 10439 10440 10443 10444 10445 10447 10451 10456 10459 10460 10461 10465 10469 10471 10481 10483 10484 10485 10492 10493 10494 10499 10511 10513 10514 10515 10517 10518 10519 10520 10522 10523 10524 10527 10530 10531 10534 10535 10536 10539 10544 10545 10546 10548 10551 10552 10553 10555 10556 10557 10558 10560 10574 10575 10592 10593 10594 10596 10597 10598 10611 10627 10628 10629 10630 10632 10633 10642 10663 10666 10668 10694 10700 10701 10702 10709 10716 10717 10728 10730 10735 10739 10838 11009 11010 11029 11076 11082 11086 11091 11093 11098 11101 11104 11108 11111 11121 11122 11126 11306 11394 11400 11417 11424 11438 11440 11449 11450 11451 11455 11788 11793 11816 12306 13832 14960 16091 19130 26071 27803 31430https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/157/99?format=asciidefaultJ/AJ/157/99/table1SDSS data used to estimate redshift accuracySimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSSDSS identifier (JHHMMSS.ss+DDMMSS.s)meta.id;meta.maincharRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.mainz[0.01001/0.02962] SDSS redshift in zsrc.redshiftdoublecz[3004/8886] SDSS redshift in czkm/sphys.veloc;pos.heliocentricintBS/RS[0.082/1.405] Blue-sloping (BS) to red-sloping (RS) flux ratiophot.flux;arith.ratiodoubleEWHa[5/292] H{alpha} equivalent width ({AA})0.1nmspect.line.eqWidthintDcz[3098/8527] cz derived from BS/RS ratiokm/sphys.veloc;pos.heliocentricintDeltacz[-1744/1284] SDSS cz minus derived cz, {Delta}czkm/sphys.veloc;arith.diffintJ/AJ/157/99/table2Imaged active galaxiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGalaxyGalaxy identifiermeta.id;meta.maincharTypeSeyfert type (1)src.classcharBmag[13.1/15.6] B-band magnitudemagphot.mag;em.opt.Bfloatcz[3765/8564] Published cz from Simbadkm/sphys.veloc;pos.heliocentricintBS/RS[0.317/1.243] Blue-sloping (BS) to red-sloping (RS) flux ratiophot.flux;arith.ratiofloatDcz[4047/8297] cz derived from BS/RS ratiokm/sphys.veloc;pos.heliocentricintDeltacz[-951/754] Published cz minus derived cz, {Delta}czkm/sphys.veloc;arith.diffintSimbadSimbad column added by the CDSmeta.ref.urlchar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.main