Space Warps Talk

Quasar Questions

  • jtreisner by jtreisner

    I'm looking for some advice on how I can rule out possible look alikes (distant, well defined round galaxies, stars, etc) from possible lensed quasars. Is there a way, for example, that I can rule something ok by using a specific filter in tools (R/G/I/Z, etc)?

    Some specific objects I've stumbled across that I have thought were possibilities but don't know if there is some other more plausible explanation. If there are some easy tricks I could use to quickly rule out lensed quasars (where I can't see a lensing galaxy), it would be much appreciated!

    ASW0000u9f - two bright white/purple dots at ~6:30

    ASW0000u9f

    ASW0008323 - two bright red/white dots at ~3

    ASW0008323

    ASW0008185 - two right white/red dots at bottom right

    ASW0008185

    ASW0000bsp - two bright red dots (next to a third dissimilar dot) at ~12

    ASW0000bsp

    ASW00009ut - two bright white/green dots at ~3 - this one perhaps looks a little different than my previous examples

    ASW00009ut

    ASW0008rao - two fainter red dots at ~12 - this one also looks different than the first three examples (quite a bit dimmer, a little fuzzier)

    ASW0008rao

    Posted

  • ElisabethB by ElisabethB moderator

    Hi jtreisner,

    Welcome to Space Warps !

    All your examples seem to be two stars appearing close together, except for the last one, where I think it is a merger of two ellipticals.

    The best way to get to see the difference is looking at a lot of images I suppose.

    Happy hunting ! ๐Ÿ˜„

    Posted

  • jtreisner by jtreisner

    Thanks! I guess that leads me into some followup questions:

    1. Is there any rule of thumb that can be used for identifying quasars vs. stars (too big / too fuzzy / too red / too dim, doesn't show up in a certain spectrum, etc)?
    2. I take it that for two stars to be so similar in appearance (color, size, brightness), they would also be of roughly the same age, formed in the same part of our galaxy, etc, or could it just be coincidental (one is bigger than the other, but closer, etc)?

    Sorry, just curious!

    Thanks again.

    Posted

  • Budgieye by Budgieye moderator

    Actually, I wish I could get someone to give me some examples of quasars in CFH telescope. I looked through the CFH telescope website for some examples, but I wasn't smart enough to find many. Most scientific articles don't publish images, because quasars all look much the same, and anyway, I would have to pay to see the article.

    In the CFH telescopes we are not supposed to know which area of the sky we are looking at, so we can't consult the NED database to see which bright "stars" are quasars.

    enter image description here

    from http://www.spacedaily.com/reports/Space_Warps_Project_Needs_Your_Help_999.html

    enter image description here

    http://www.newscientist.com/article/dn12007-new-quasar-is-the-oldest-yet.html#.Ul-s4BCGgp8

    There are 100,000 quasars, and many of them have been posted in Galaxy Zoo, and that is where my experience is.

    So... I think quasars should be bright and round.

    Bright, even the distant ones at z=5 (the red ones)are still quite bright.

    Shape, round and not too fuzzy, the more distant ones are quite small but a good round shape.

    Most will be bright blue or red-blue, not a white-blue. See Colours of Galaxies in SDSS : Redshift chart http://www.galaxyzooforum.org/index.php?topic=277142.0. The colours are the same in CFHT. The nearest ones that can be lensed are at a distance of about z=0.6, so they are blue. Quasars have lots of blue and UV light, so when you press the bluer button in tools, it should stay blue. More distant quasars are progressively pink, blue, green, orange, yellow, red (the furthest that we can see).

    Here are some lensed quasars in images taken by the SDSS telescope.
    Re: Part 3 Double quasars in SDSS,... and triple, and quadruple.
    A green one was posted by 1000GGG, AlexandredOr correctly suggested that it might be a lens
    http://www.galaxyzooforum.org/index.php?topic=275811.msg355411#msg355411

    enter image description here

    http://skyserver.sdss3.org/dr9/en/tools/explore/obj.asp?id=1237667735586078852

    enter image description here

    Binary stars might be identical twins, and might look like a double quasar.
    The only was to tell for sure that a bright object is a quasar is to do a spectral analysis to look for the Lyman alpha peak, and that is expensive.

    Posted

  • c_cld by c_cld

    Hi Budgie,
    Please see http://talk.spacewarps.org/#/boards/BSW0000004/discussions/DSW00007l0

    I'd also cross-match QSO catalog with CFHTLS giving ~1000 spectroscopic objects. I'll post a sample of them in different bins of redshift from CADC/CCDA.

    Cheers

    Posted

  • c_cld by c_cld

    see also http://talk.spacewarps.org/#/boards/BSW0000004/discussions/DSW00007j7

    1237679341103874245 object in QSO color space

    1237679341103874245 1237679341103874245

    Posted

  • c_cld by c_cld

    CFHTLS image cutout service
    image size: 60 arcsec on the side for all sample
    centered on QSO

    1237673701279531827 z spec=5.421

    1237673701279531827 1237673701279531827

    1237661385994928507 z spec=3.386

    1237661385994928507 1237661385994928507

    1237670955181211840 z spec=3.0

    1237670955181211840 1237670955181211840

    1237663479259660624 z spec=2.497

    1237663479259660624 1237663479259660624

    1237655368759050276 z spec=2.107

    1237655368759050276 1237655368759050276

    1237653502043685001 z spec=1.517

    1237653502043685001 1237653502043685001

    1237659324406038647 z spec=1.074 deblended in SDSS

    1237659324406038647 1237659324406038647

    1237652900227579955 z spec=0.989

    1237652900227579955 1237652900227579955

    1237663478722265334 z spec=0.881

    1237663478722265334 1237663478722265334

    1237661417675948100 z spec=0.720

    1237661417675948100 1237661417675948100

    1237659150458028243 z spec=0.527

    1237659150458028243 1237659150458028243

    1237663543147298845 z spec=0.400

    1237663543147298845 1237663543147298845

    1237659326016585782 z spec=0.326

    1237659326016585782 1237659326016585782

    Posted

  • Budgieye by Budgieye moderator

    Thank you for the quasar tour, c_cld. You are a star!

    I should have remembered the Thick blue ring, it's just too perfect post.

    The quasars are much whiter than in SDSS. What happened to the blue colour?

    The image texture of the CFHT cutouts look different from the SpaceWarps images that we are presented with.

    But the quasars are big, round and bright.

    Posted

  • jtreisner by jtreisner

    Thanks guys - I think that's about as clear as mud ๐Ÿ˜› It does definitely help reading your post Budgieeye and seeing all the examples and reading the other threads that c_cld linked though. Since it seems like stars and quasars can be look alikes even to the pros I guess I'll just keeping on marking potential candidates when I see them.

    Also, the galaxy zoo thread you linked - all the pictures just are black and say failed to initialize or something like that on them. Not sure if that's a problem on my end though.

    Posted

  • Budgieye by Budgieye moderator

    The quasar points, double and quads posted are too dim to be quasars.

    After looking at C_CLD's images, I think the way to tell them apart (maybe) is that they are bright for their size, and have a tidy round disc. The only way to be sure is to take a spectral analysis.

    I might be confused by white dwarf stars, which are small hot and blue.

    QSO โ€“ (celestial object) Quasi-Stellar Object
    Quasar โ€“ (celestial object) QUASi-stellAR radio source

    (RE: initialize, I should update the links. It seems that SDSS is not supporting some of its older image cut-out system.)

    Posted

  • c_cld by c_cld

    I agree that quasar points posted in talk are "points" but of no resemblance with spectroscopic QSO imaged by CFHTLS megacam even at high redshifts.

    Posted

  • c_cld by c_cld

    Using the python tool Human Viewable (color composite) Image creation (authors Phil & all)

    I processed object 1237659324406038647 (see previous post) and got

    gri

    1237659324406038647 gri

    ugr

    1237659324406038647 ugr

    Posted

  • c_cld by c_cld

    Other kind of QSO: Blazar

    QSO B1418+54 -- BL Lac - type object

    1237661388142018563

    1237661388142018563 1237661388142018563

    Color composite (Phil's tool)

    enter image description here

    Posted

  • c_cld by c_cld

    Please remind also your Science Board / The Objects/discussion http://talk.spacewarps.org/#/boards/BSW0000004/discussions/DSW00007m5 called

    "The splitting of light from a quasar though a lens."

    some objects appeared previously there.

    Posted

  • c_cld by c_cld in response to Budgieye's comment.

    ASW0009ao8 A blue QSO posted by jtreisner ๐Ÿ˜ƒ

    1237679322862452954 z spec= 2.473

    ASW0009ao8 enter image description here

    enter image description here CFHTLS cutout

    enter image description here

    Posted

  • Budgieye by Budgieye moderator

    Well, that one looks just like a blue star in the SpaceWarps images. It looks better in CFHT cut-out.

    Nice blazar , where's my sunglasses 8)

    Posted

  • Budgieye by Budgieye moderator

    Most of the SDSS dr7 images posted in the Galaxy Zoo Forum link are now back on line, except maybe the double green quasar.

    Posted

  • c_cld by c_cld

    Example of color variation in composite ugr, gri or riz filters to RGB channels for a remote QSO of strong Ly_alpha emission at 6029[ร…] :
    1237673709329711312 z spec=3.96

    see optical spectrum

    SDSSgri

    terapix ugr(Ly/orange), gri(Ly/green), riz(Ly/blue)

    ugr gri riz

    Posted

  • c_cld by c_cld

    CFHQS J142952+544717 14:29:52.17 +54:47:17.7 http://arxiv.org/pdf/0912.0281v1.pdf

    "This quasar was discovered in the CFHTLS Wide W3 region. However, it is much brighter than our Wide magnitude limit of z0 = 23 and has the second brightest absolute magnitude in this paper. The spectrum shows a strong continuum with only a weak Ly emission line at z = 6.21. This is consistent with the relatively red color of z0 - J = 0.81."

    terapix riz composite

    CFHQS J142952+544717 Red dot at top edge

    CFHTLS cutout gri composite

    CFHQS J142952+544717 red pinhead centred target

    Could be very difficult to identify in a Spacewarps ASWxxxx image! ๐Ÿ˜ƒ

    Posted

  • Tom_Collett by Tom_Collett scientist

    You can't tell the difference between a star and a quasar from the spacewarps imaging alone. Both are point sources, and only look like a circle because the image is blurred by the atmosphere and the telescope. Quasars are typically very blue, in colour but they have a sharp break in their spectrum that can make high redshift quasars look red (or green).

    As a rule of thumb, if you can tell that there are two stars/quasars near each other, you'll be able to see the lens between them (if it's a lensed quasar).

    Posted

  • Budgieye by Budgieye moderator

    Actually, we are trying to tell the difference between a star and a quasar (without a spectrum), although we have a huge failure rate! We are looking for stars that are bright for their "size" with sharp circular edges. It probably depends too on type of quasar it is.

    Since quasars have strong emission lines, it can affect the colours of the diffraction circles, I noticed that in the SDSS.

    Anyway, small fuzzy stars are not likely to be "quasar points".

    Posted

  • c_cld by c_cld

    One amazing spectral QSO among the nearest, with very large spiral arm:

    1237655369295724599 z 0.174

    1237655369295724599

    CFHTLS 60 arcsec on the side

    enter image description here

    Posted

  • Budgieye by Budgieye moderator

    Wow, so much detail, but I miss the magenta colour of the nucleus. Is there no blue in the images?

    Posted

  • c_cld by c_cld

    ASW0008nul

    ASW0008nul

    #QSO 1237656567583670573 z spec 2.856

    QSO

    Posted

  • c_cld by c_cld

    ASW00097c7

    ASW00097c7 QSO with spikes in bottom left corner

    QSO 1237678595932094536

    SDSS J222024.58+010931.3 z spec= 0.213

    1237678595932094536
    UKIDSS-K: UKIRT Infrared Deep Survey K-band with color table

    [edit Jan 23, 2016] imaged DECALS DR2

    Brick: 3351p012, Objid: 1022 Brick: 3351p012, Objid: 1022

    Posted

  • c_cld by c_cld

    http://talk.spacewarps.org/#/subjects/ASW00074fk #no_lens (false positive)

    #QSO SDSS J142010.24+524029.6

    ASW00074fk enter image description here 1237661385994862858

    1237661385994862858

    Posted

  • c_cld by c_cld

    http://talk.spacewarps.org/#/subjects/ASW00067j2 #no_lens (false positive)

    #QSO #AGN SDSS J140049.60+554503.3

    1237661418748510377 1237661418748510377

    enter image description here

    Posted

  • c_cld by c_cld

    http://talk.spacewarps.org/#/subjects/ASW0001rcc

    #QSO

    1237679341103874245

    1237679341103874245

    8149372763992944640

    Posted

  • c_cld by c_cld

    http://talk.spacewarps.org/#/subjects/ASW0007qoo

    #QSO z_spec 2.763

    1237655463238893943

    1237655463238893943 #SA107 on edge

    ASW0007qoo QSO West of arc

    Posted

  • c_cld by c_cld

    Dark Energy Survey (#DES)

    DECam Legacy Survey Dark Energy Camera on the Blanco Telescope

    Data Release 1

    April 2015

    #QSO #lensed SDSS J095122.57+263513.9 1237667112262107167

    1237667112262107167

    http://legacysurvey.org/viewer/?layer=decals-dr1j-edr&ra=147.84410&dec=+26.58716&zoom=16

    DECam QSO from DECam viewer

    [edit Jan 23, 2016] DR2 release

    1237667112262107167 in Decals DR2

    Posted

  • c_cld by c_cld

    http://talk.spacewarps.org/#/subjects/ASW0004k7v QSO at 8 o'clock

    enter image description here 1237673701278810143

    SDSS J022637.09-083118.1 z_spec 0.184

    1237673701278810143

    Posted

  • c_cld by c_cld

    Discovery of two gravitationally lensed quasars in the Dark Energy Survey arXiv:1508.01203 Wed, 5 Aug 2015

    DES J2146๏ฟฝ0047 is in the area of overlap between DES and the Sloan Digital Sky Survey (SDSS). Two blue components are visible in the DES and SDSS images. The SDSS ber spectrum shows a quasar component at zs = 2.38 and absorption compatible with Mg II and Fe II at zl = 0.799, which we tentatively associate with the foreground lens galaxy. The long-slit Magellan spectra show that the blue components are resolved images of the same quasar. The Einstein Radius is 0.68" corresponding to an enclosed mass of 1:6  10^11M :

    #QSO #lensed SDSS J214646.04-004744.2 1237656567581377069 ra,dec 326.69185, -0.79563; 21:46:46.04, -00:47:44.28

    1237656567581377069

    DES DECaLS DR1 images

    Posted

  • c_cld by c_cld in response to c_cld's comment.

    DECaLS DR2 release

    1237656567581377069 DR2 1237656567581377069

    Posted

  • c_cld by c_cld

    SDSS J092455.87+021924.9: A gravitationally lensed quasar in quad configuration (z source spec=1.523, z lens= 0.394)

    1237673708259508232

    enter image description here SDSS

    DECaLS decals-dr2

    Keck II Keck NIRC2 instrument, Kp filter central 2.124ยตm, colormap: logarithmic thermal

    HST my composite image from HST WFC3 UVIS2-C1K1C-SUB, filters F410M, F547M, F621M, F845M

    Posted

  • c_cld by c_cld

    sample of quasars in pair with similar looking object

    123766509845335264912376650984533526491237665098453352649SDSS J080009.98+165509.4

    123765763004615896412376576300461589641237657630046158964SDSS J082155.94+340412.8

    123765127242520994612376512724252099461237651272425209946SDSS J084512.74+543421.4

    123765510890068396112376551089006839611237655108900683961SDSS J085122.37+472249.0

    123766725453493066712376672545349306671237667254534930667SDSS J092050.81+224113.8

    123765366579435949912376536657943594991237653665794359499SDSS J094713.15+024743.7

    123765079622057987412376507962205798741237650796220579874SDSS J094943.34+000536.2

    123766106818150401212376610681815040121237661068181504012SDSS J110456.56+130711.1

    123767116616794113512376711661679411351237671166167941135 SDSS J110633.38-182123.6

    123766754927365336212376675492736533621237667549273653362SDSS J112235.03+232634.9

    123765403140338500112376540314033850011237654031403385001SDSS J113613.37+033840.9

    123764872123357601012376487212335760101237648721233576010SDSS J122608.02-000602.2

    123766827082481673912376682708248167391237668270824816739SDSS J133018.64+181032.1

    123766512801382406312376651280138240631237665128013824063SDSS J133401.39+331534.3

    123766219881218049412376621988121804941237662198812180494SDSS J135404.14+110725.8

    123765175294971097712376517529497109771237651752949710977SDSS J135944.21+012809.8

    123767460428978594012376746042897859401237674604289785940SDSS J141235.37+004104.1

    123766791006892872812376679100689287281237667910068928728SDSS J142341.94+204001.5

    123766219827897986312376621982789798631237662198278979863SDSS J142815.63+095443.5

    123766535024522042312376653502452204231237665350245220423SDSS J144208.77+260903.7

    123764872125133640412376487212513364041237648721251336404SDSS J150824.22-000603.8

    123766230673129480712376623067312948071237662306731294807SDSS J151109.85+335701.7

    123765546592613192212376554659261319221237655465926131922SDSS J151236.94+553901.0

    123764870406012964812376487040601296481237648704060129648SDSS J151538.95-001240.7

    123766266267539869312376626626753986931237662662675398693SDSS J151623.87+310336.3

    123766542756721473712376654275672147371237665427567214737SDSS J152024.49+211155.4

    123765546913719946712376554691371994671237655469137199467SDSS J152631.31+015103.1

    123766261918721657812376626191872165781237662619187216578SDSS J155225.62+300902.0

    123766833257349154412376683325734915441237668332573491544SDSS J160014.58+102852.4

    123766269757554701712376626975755470171237662697575547017SDSS J160614.69+230518.1

    123766553547014165112376655354701416511237665535470141651SDSS J161848.15+171459.4

    123766354206497252812376635420649725281237663542064972528SDSS J205333.01-010058.3

    123766327846214054412376632784621405441237663278462140544SDSS J233713.66+005610.8

    Posted

  • c_cld by c_cld

    possible other candidates with QSO spectrum

    123767947694171807012376794769417180701237679476941718070SDSS J012142.20+211407.2

    123766487941224892312376648794122489231237664879412248923SDSS J092115.47+285444.3

    123766828800789779012376682880078977901237668288007897790SDSS J100251.86+154718.2

    123767900502222441412376790050222244141237679005022224414SDSS J231757.54+043220.7

    Posted

  • c_cld by c_cld

    https://talk.galaxyzoo.org/#/boards/BGZ0000001/discussions/DGZ000167u?page=3&comment_id=58b012617d25c7748d0005f3

    Thumbnails sample recap of new lensed quasars candidates from SDSS survey, not yet listed in catalogs and to be confirmed or deprecated as binary or as impostors.

    lensed_quasars

    discovered by that kind of viewing among so many pairs ๐Ÿ˜ƒ

    | IAUname                  | bestobjid           | ra        | dec      | specobjid           | plate | mjd   | fiberid | z     | NeighborObjID       | separation " |
|--------------------------|---------------------|-----------|----------|---------------------|-------|-------|---------|-------|---------------------|--------------|
| SDSS J073223.90+360044.6 | 1237651252550697462 | 113.09961 | 36.01239 | 2334132131552323584 | 2073  | 53728 | 515     | 2.734 | 1237651252550697463 | 5.62         |
| SDSS J073534.58+203634.2 | 1237660563502137970 | 113.89411 | 20.60950 | 5044158120294486016 | 4480  | 55591 | 460     | 2.188 | 1237660563502137971 | 3.54         |
| SDSS J083228.49+563234.2 | 1237663530797957374 | 128.11871 | 56.54285 | 2007637370626664448 | 1783  | 53386 | 574     | 0.683 | 1237663530797957375 | 3.09         |
| SDSS J083649.55+484154.0 | 1237654383585656941 | 129.20647 | 48.69836 | 619362079618394112  | 550   | 51959 | 426     | 1.711 | 1237654383585656942 | 4.07         |
| SDSS J092659.57+062326.7 | 1237658300600484013 | 141.74822 | 6.39077  | 1116985110923601920 | 992   | 52644 | 336     | 0.667 | 1237658300600484014 | 4.58         |
| SDSS J094122.50+051823.8 | 1237658423010525423 | 145.34379 | 5.30664  | 5485441070710788096 | 4872  | 55944 | 206     | 0.343 | 1237658423010525422 | 3.86         |
| SDSS J094122.50+051823.8 | 1237658423010525423 | 145.34379 | 5.30664  | 5485441070710788096 | 4872  | 55944 | 206     | 0.343 | 1237658423010525424 | 1.74         |
| SDSS J094122.71+051821.6 | 1237658423010525422 | 145.34466 | 5.30601  | 1118056036356352000 | 993   | 52710 | 136     | 1.546 | 1237658423010525424 | 5.50         |
| SDSS J125952.05+623022.1 | 1237655370363830429 | 194.96689 | 62.50614 | 7847529605631971328 | 6970  | 56444 | 26      | 2.306 | 1237655370363830428 | 9.06         |
| SDSS J142758.88-012130.3 | 1237655499744018693 | 216.99537 | -1.35844 | 4535147459056111616 | 4028  | 55621 | 82      | 2.269 | 1237655499744018694 | 6.24         |
| SDSS J143836.26+174538.1 | 1237667733986345165 | 219.65111 | 17.76061 | 6157735532929355776 | 5469  | 56037 | 687     | 0.584 | 1237667733986345166 | 8.41         |
| SDSS J154107.46-003716.0 | 1237655693556580446 | 235.28109 | -0.62113 | 354698630730377216  | 315   | 51663 | 146     | 0.754 | 1237655693556580447 | 5.68         |
| SDSS J155752.31+342140.0 | 1237662473692315813 | 239.46799 | 34.36111 | 1595414514344421376 | 1417  | 53141 | 52      | 1.265 | 1237662473692315815 | 7.08         |
| SDSS J164045.57+193255.3 | 1237662225166959350 | 250.18989 | 19.54870 | 4709728187273056256 | 4183  | 55447 | 323     | 0.778 | 1237662225166959351 | 4.81         |
| SDSS J164045.66+193257.2 | 1237662225166959349 | 250.19028 | 19.54922 | 4573611120581808128 | 4062  | 55383 | 748     | 0.195 | 1237662225166959351 | 2.66         |
| SDSS J092524.61+435022.8 | 1237657630053040401 | 141.35257 | 43.83968 | 979640984977565696  | 870   | 52325 | 393     | 0.352 | 1237657630053040400 | 4.34       |
| SDSS J092524.61+435022.8 | 1237657630053040401 | 141.35257 | 43.83968 | 979640984977565696  | 870   | 52325 | 393     | 0.352 | 1237657630053040546 | 10.85      |
| SDSS J092523.72+435027.8 | 1237657630053040546 | 141.34887 | 43.84106 | 5287341517857230848 | 4696  | 56354 | 420     | 1.003 | 1237657630053040400 | 15.13      |
| SDSS J092523.72+435027.8 | 1237657630053040546 | 141.34887 | 43.84106 | 5287341517857230848 | 4696  | 56354 | 420     | 1.003 | 1237657630053040401 | 10.85      |

    bestobjid: QSO with spectrum, or lens galaxy if redshift z less than 0.4

    NeighborObjid: twin QSO without spectrum, or lens galaxy if separation less than 2

    Posted

  • c_cld by c_cld

    QSO pair candidate or gravitationally lensed QSO by group galaxies?

    SDSS J120426.66+015534.8 1237651735757455416 z_spec 1.376

    1237651735757455416 SpecObjID = 582151583567996928

    SDSS J120426.14+015527.8 1237651735757455413 ra 181.108937365, dec 1.924388905 separation 0.175' = ~10.5"

    "star" in QSO color space

    Panstarrs 1237651735757455413 PanStarrs z/i/r

    Posted