J/AJ/146/100ivo://CDS.VizieR/J/AJ/146/100doi:10.26093/cds/vizier.51460100CDSWu X.-B.Zuo W.Yang J.Yang Q.Wang F.2017-09-19T14:23:48Z2014-07-15T12:41:46ZCDS support team

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

cds-question@unistra.frvisible-astronomysloan-photometryredshiftedquasarsinfrared-photometryThe identification of quasars at intermediate redshifts (2.2<z<3.5) has been inefficient in most previous quasar surveys since the optical colors of quasars are similar to those of stars. The near-IR K-band excess technique has been suggested to overcome this difficulty. Our recent study also proposed to use optical/near-IR colors for selecting z<4 quasars. To verify the effectiveness of this method, we selected a list of 105 unidentified bright targets with i<=18.5 from the quasar candidates of SDSS DR6 with both SDSS ugriz optical and UKIDSS YJHK near-IR photometric data, which satisfy our proposed Y-K/g-z criterion and have photometric redshifts between 2.2 and 3.5 estimated from the nine-band SDSS-UKIDSS data. We observed 43 targets with the BFOSC instrument on the 2.16m optical telescope at Xinglong station of the National Astronomical Observatory of China in the spring of 2012. We spectroscopically identified 36 targets as quasars with redshifts between 2.1 and 3.4. The high success rate of discovering these quasars in the SDSS spectroscopic surveyed area further demonstrates the robustness of both the Y-K/g-z selection criterion and the photometric redshift estimation technique. We also used the above criterion to investigate the possible stellar contamination rate among the quasar candidates of SDSS DR6, and found that the rate is much higher when selecting 3<z<3.5 quasar candidates than when selecting lower redshift candidates (z<2.2). The significant improvement in the photometric redshift estimation when using the nine-band SDSS-UKIDSS data over the five-band SDSS data is demonstrated and a catalog of 7727 unidentified quasar candidates in SDSS DR6 selected with optical/near-IR colors and having photometric redshifts between 2.2 and 3.5 is provided. We also tested the Y-K/g-z selection criterion with the recently released SDSS-III/DR9 quasar catalog and found that 96.2% of 17999 DR9 quasars with UKIDSS Y- and K-band data satisfy our criterion. With some available samples of red quasars and type II quasars, we find that 88% and 96.5% of these objects can be selected by the Y-K/g-z criterion, respectively, which supports our claim that using the Y-K/g-z criterion efficiently selects both unobscured and obscured quasars. We discuss the implications of our results on the ongoing and upcoming large optical and near-IR sky surveys.2013AJ....146..100Whttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/146/100CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/269 : SDSS Quasar Catalog, DR9Q (Paris+, 2012)II/314 : UKIDSS-DR8 LAS, GCS and DXS Surveys (Lawrence+ 2012)VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)VII/241 : The 2dF QSO Redshift Survey (Croom+ 2004)J/ApJS/199/3 : The quasars MMT-BOSS pilot survey (Ross+, 2012J/AJ/144/49 : Quasars from SDSS-DR7, WISE and UKIDSS surveys (Wu+, 2012)J/MNRAS/424/2876 : Large area KX quasar catalogue (Maddox+, 2012)J/ApJ/753/125 : NIR spectroscopy follow-up of 60 SDSS-DR7 QSOs (Shen+, 2012)J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)J/AJ/141/105 : NIR-matched quasar catalog (Peth+, 2011)J/AJ/142/78 : New 2.2<z<3 quasars from SDSS and UKIDSS (Wu+, 2011)J/MNRAS/406/1583 : Quasar from SDSS and UKIDSS (Wu+, 2010)J/ApJ/692/758 : BAL QSOs in SDSS-DR5 (Gibson+, 2009)J/ApJS/180/67 : Photometric selection of SDSS quasars. II. (Richards+, 2009)J/MNRAS/386/1605 : Luminous K-band selected QSOs from UKIDSS (Maddox+, 2008)J/AJ/136/2373 : Type 2 quasars from SDSS (Reyes+, 2008)J/ApJS/165/1 : BAL QSOs from SDSS DR3 (Trump+, 2006)J/AJ/131/2788 : Redshifts in the SFQS survey (Jiang+, 2006)J/AJ/131/2766 : Quasar luminosity function from SDSS-DR3 (Richards+, 2006)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/146/100https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/146/100http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/146/100https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/146/100https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/146/100http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/146/100GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/146/100/table2 (Parameters and observation details of 43 quasar candidates)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/146/100/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/146/100/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/146/100/table2?GETtext/xml+votable180.050000true119.44223.34838890.005555555555555556Cone search capability for table J/AJ/146/100/table4 (A catalog of 7727 SDSS-UKIDSS quasar candidates at 2.2<=z_ph_<=3.5 selected from Richards et al. (2009, cat J/ApJS/180/67))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/146/100/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/146/100/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/146/100/table4?GETtext/xml+votable180.050000true0.024791714.88613890.0055555555555555564/258 259 262 299 303 512 514 515 521 522 544 582 584 1367 1647 1653 1654 1655 1657 1658 1659 1660 1694 1707 1709 1713 1722 1730 1732 1733 1963 5/136 1027 1028 1029 1031 1040 1042 1043 1044 1045 1056 1057 1061 1062 1064 1072 1088 1190 1191 1201 1202 1203 1206 1207 1209 1210 1211 1226 1227 1231 1239 1242 1243 1244 1245 1249 1250 1251 1256 1265 1410 1416 1540 1541 1548 1552 1553 1554 1556 1560 2053 2054 2055 2064 2065 2066 2068 2070 2073 2074 2075 2076 2081 2083 2092 2094 2095 2096 2098 2180 2184 2185 2265 2288 2289 2313 2314 2315 2316 2318 2319 2341 2342 4501 4517 4522 4596 4598 4601 4602 4917 4918 4921 4922 4933 4937 4938 4998 5461 5462 5463 5465 5467 5489 5492 5501 6485 6490 6491 6493 6494 6499 6502 6503 6504 6506 6512 6516 6517 6527 6543 6549 6550 6552 6554 6565 6566 6568 6569 6583 6585 6586 6587 6593 6607 6611 6627 6644 6645 6646 6648 6650 6719 6741 6742 6743 6745 6750 6751 6760 6761 6765 6766 6767 6768 6769 6771 6772 6773 6774 6780 6781 6783 6797 6799 6801 6802 6804 6805 6806 6808 6812 6814 6815 6822 6823 6825 6826 6827 6835 6841 6842 6843 6845 6846 6847 6850 6857 6858 6859 6860 6863 6864 6865 6867 6868 6869 6870 6873 6880 6881 6883 6884 6886 6887 6892 6895 6896 6914 6915 6917 6918 6919 6924 6925 6927 6936 6937 6939 6940 6942 6943 6945 6946 6947 6949 6950 6951 6952 6953 6954 6956 6960 6965 6977 6978 6979 6982 6984 6985 6986 7834 7845 7846 7847 7848 7849 7850 7856 7858 7859 7862 7865 7866 7867 7868 7870 7871 7914 6/0 1 2 523 524 526 548 552 553 554 4096 4098 4099 4100 4101 4103 4104 4106 4107 4120 4122 4123 4164 4165 4167 4184 4185 4187 4189 4190 4208 4209 4210 4212 4216 4233 4234 4235 4236 4238 4239 4240 4242 4243 4252 4253 4260 4261 4262 4264 4292 4360 4369 4370 4371 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17663 17727 17746 17747 17748 17751 17752 17754 17756 17758 17762 17763 17765 17766 17767 17769 17770 17771 17772 17777 17778 17805 17807 17812 17813 17815 17818 17819 17820 17828 17831 17832 17834 17836 17840 17842 17981 17998 18001 18003 18009 18010 18012 18020 18021 18022 18024 18066 18067 18073 18074 18075 18081 18082 18084 18096 18176 18177 18299 18300 18301 18302 18367 18381 18382 18383 18389 18390 18391 18396 18398 18403 18414 18416 18418 18686 18687 18751 18765 18766 18771 18772 18775 18778 18780 18781 18785 18789 18790 18795 18798 18800 18801 18831 18835 18836 18838 18839 18841 18842 18843 18844 18846 18852 18854 18855 18856 18857 18859 18860 18861 18864 18866 18882 19007 19022 19028 19029 19030 19032 19033 19034 19036 19038 19044 19047 19048 19049 19051 19052 19056 19058 19086 19087 19089 19090 19091 19092 19093 19095 19096 19100 19101 19106 19107 19108 19112 19115 19116 19117 19118 19200 19202 19457 19583 19645 19647 19663 19667 19676 19677 19678 19681 19682 19683 19692 19693 19696 19697 19698 19700 19726 19727 19731 19737 19739 19742 19747 19756 19757 19760 19761 19762 19764 19768 19776 19777 19778 19784 19840 19981 19982 19985 19986 19987 19988 19990 19991 19996 19997 20001 20004 20005 20016 20032 20033 20034 20036 21839 21843 21859 21864 21865 21867 21965 21972 21973 21974 21976 21977 21981 21982 21983 22001 22013 23138 23145 23147 23149 23181 23182 23183 23189 23190 23191 23192 23193 23194 23196 23197 23201 23202 23204 23208 23211 23212 23216 23218 23233 23234 25591 25595 25596 25597 25599 25847 25849 25853 25854 25855 25917 25918 25919 25927 25931 25932 25933 25935 25937 25938 25939 25944 25945 25947 25948 25949 25950 25952 25953 25954 25957 25958 25959 25968 25970 25971 25981 25982 25983 25991 25995 26001 26002 26003 26004 26006 26020 26021 26023 26028 26030 26032 26033 26034 26036 26037 26038 26040 26041 26042 26052 26053 26056 26057 26058 26073 26076 26077 26079 26101 26102 26103 26105 26106 26107 26167 26171 26189 26190 26191 26192 26193 26195 26205 26212 26213 26214 26224 26229 26230 26231 26233 26234 26235 26236 26237 26238 26246 26247 26252 26253 26254 26256 26257 26258 26268 26269 26270 26281 26282 26285 26286 26287 26288 26289 26290 26294 26296 26297 26298 26301 26302 26303 26304 26305 26306 26317 26318 26319 26321 26322 26323 26324 26327 26328 26329 26331 26337 26338 26339 26368 26369 26370 26376 26378 26379 26380 26381 26382 26384 26397 26398 26400 26401 26402 26404 26408 26417 26418 26419 26420 26423 26424 26427 26439 26503 26504 26506 26507 26588 26589 26590 26596 26598 26599 26604 26605 26606 26608 26610 26863 26871 26874 26875 26941 26942 26951 26955 26957 26958 26961 26962 26963 26976 26977 26984 26985 26987 26988 26989 26990 26992 26993 26995 26996 26997 26998 27019 27020 27022 27023 27025 27027 27028 27029 27030 27033 27034 27035 27036 27037 27039 27048 27050 27051 27052 27053 27055 27056 27057 27059 27081 27082 27083 27100 27101 27103 27128 27129 27131 27167 27193 27194 27195 27203 27212 27214 27215 27228 27230 27231 27236 27237 27238 27240 27242 27243 27244 27246 27252 27269 27270 27271 27273 27276 27278 27280 27282 27283 27284 27285 27286 27299 27330 27331 27332 27333 27335 27336 27337 27338 27360 27363 27376 27377 27378 27392 27394 27396 27397 27398 27404 27406 27407 27425 27426 27427 27444 27446 27447 27448 27450 27451 27464 27466 27467 27484 27488 27489 27491 27497 27498 27499 27502 27503 27504 27528 27529 27530 27540 27541 27543 27572 27573 27575 27576 27577 27588 27590 27592 27593 27618 27624 27648 27649 27651 27652 27654 27665 27667 27704 27705 27753 27754 27755 27766 27767 27776 27778 27779 27793 27794 27795 27820 27821 27822 27828 27830 27832 27844 27845 27846 27849 27852 27856 27857 27859 27865 27867 27868 27870 27875 27876 27877 27878 27880 27881 27882 27904 27905 27906 27922 27924 27925 27927 27932 27933 27934 27948 27949 27950 27952 27953 27954 27956 27968 27969 27970 27976 28032 28033 28034 28160 30036 30037 31291 31293 31294 31295 31330 31365 31366 31367 31369 31370 31371 31372 31374 31375 31376 31377 31379 31405 31406 31407 31430 31431 31442 31454 31455 31456 31457 31459 31477 31479 31626 31650 31651 36862 36863 40959 45044 45045 45046 45051 45052 45053 45055 49149 491518.305533028865447e-20 6.090060298487514e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/146/100?format=asciiOpticalInfrareddefaultJ/AJ/146/100/table2Parameters and observation details of 43 quasar candidatesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSSDSS quasar candidate name (JHHMMSS.ss+DDMMSS.s)meta.id;meta.maincharn_SDSSSimbad column added by the CDSmeta.ref.urlintnullableDateDate of observationtime.epochnullableExpExposure timestime.duration;obs.exposureintumagSDSS u-band AB magnitudemagphot.mag;em.opt.UfloatgmagSDSS g-band AB magnitudemagphot.mag;em.opt.BfloatrmagSDSS r-band AB magnitudemagphot.mag;em.opt.RfloatimagSDSS i-band AB magnitudemagphot.mag;em.opt.IfloatzmagSDSS z-band AB magnitudemagphot.mag;em.opt.IfloatYmagUKIDSS Y band Vega magnitudemagphot.mag;em.IR.JfloatJmagUKIDSS J band Vega magnitudemagphot.mag;em.IR.JfloatHmagUKIDSS H band Vega magnitudemagphot.mag;em.IR.HfloatKmagUKIDSS K band Vega magnitudemagphot.mag;em.IR.Kfloatzph1Richards et al. (2009, cat J/ApJS/180/67) photometric redshift (G1)src.redshift.photfloatzph2[2.225/3.55] This work photometric redshift (G2)src.redshift.photfloatObjectIdentification result (1)src.classcharzsp? Spectral redshift from our observationssrc.redshiftfloatnullableULASDisplay the UKIDSS/LAS DR8 catalog (cat. II/314) within 1.5"meta.ref.urlcharSDSS9Display the SDSS-DR9 photometric data (cat. V/139) within 1.5"meta.ref.urlcharSloanDisplay the SDSS data for this quasarmeta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlchar_RAPositions from SDSS names (right ascension part)degpos.eq.ra;meta.main_DEPositions from SDSS names (declination part)degpos.eq.dec;meta.mainJ/AJ/146/100/table4A catalog of 7727 SDSS-UKIDSS quasar candidates at 2.2<=z_ph_<=3.5 selected from Richards et al. (2009, cat J/ApJS/180/67)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSSDSS quasar candidate name (JHHMMSS.ss+DDMMSS.s)meta.id;meta.maincharn_SDSSSimbad column added by the CDSmeta.ref.urlintnullablezph1Richards et al. (2009, cat J/ApJS/180/67) photometric redshift (G1)src.redshift.photfloatzph2[2.225/3.45] This work photometric redshift (G2)src.redshift.photfloatumagSDSS u-band AB magnitudemagphot.mag;em.opt.UfloatgmagSDSS g-band AB magnitudemagphot.mag;em.opt.BfloatrmagSDSS r-band AB magnitudemagphot.mag;em.opt.RfloatimagSDSS i-band AB magnitudemagphot.mag;em.opt.IfloatzmagSDSS z-band AB magnitudemagphot.mag;em.opt.IfloatYmagUKIDSS Y band Vega magnitudemagphot.mag;em.IR.JfloatJmagUKIDSS J band Vega magnitudemagphot.mag;em.IR.JfloatHmagUKIDSS H band Vega magnitudemagphot.mag;em.IR.HfloatKmagUKIDSS K band Vega magnitudemagphot.mag;em.IR.KfloatULASDisplay the UKIDSS/LAS DR8 catalog (cat. II/314) within 1.5"meta.ref.urlcharSDSS9Display the SDSS-DR9 photometric data (cat. V/139) within 1.5"meta.ref.urlcharSloanDisplay the SDSS data for this quasarmeta.ref.urlchar_RAPositions from SDSS names (right ascension part)degpos.eq.ra;meta.main_DEPositions from SDSS names (declination part)degpos.eq.dec;meta.main