Author Topic: Zooite Guide to Strong Gravitational Lenses  (Read 30856 times)

Budgieye

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Zooite Guide to Strong Gravitational Lenses
« on: July 28, 2009, 06:46:00 am »
Zooite Guide to Gravitational Lenses

This guide has many examples from the SDSS database, used by Galaxy Zoo 2.
The images are in three colours: blue, green and red.

The new Hubble Zoo is using data from the Hubble Space Telescope, and those images have better resolution.
The images are in two colours: light blue and orange.
 
Part 1 Overview of gravitational lenses
Part 2 What to look for using confirmed strong lenses in SDSS
Part 3 Double quasars in SDSS,... and triple, and quadruple.
Part 4 These are not lenses
Part 5 Strong Gravitational lenses in Hubble Space Telescope photos
Part 6 Lenses from Hubble Zoo
Part 7 Index to the Possible Strong Gravitational Lenses forum posts

What is a lens?

credit: NASA

Here is model of a gravitational lens. We are looking at it from the side.

A gravitational lens consists of a massive lensing galaxy, and lensed galaxies that are behind it.
Here is a diagram of a gravitational lens system, looking at it from the side.

Earth...          a massive lensing galaxy with strong gravity....       a distant spiral galaxy behind it

Light starts to travel from distant spiral galaxy towards Earth (straight white lines).

We can't see the distant spiral galaxy directly because the massive lensing galaxy is in the way. The spiral galaxy would have been too dim to see anyway.

The light that passes near a massive galaxy, is pulled towards that galaxy by gravity (the bending path of the light is shown by the curving white lines). A great deal of light that should have been heading in other directions is now heading towards Earth.

The light reaches telescopes on Earth, and a picture is taken. (The photograph of the galaxies as seen from Earth is superimposed in middle of the diagram. ) We see the massive lensing galaxy in the middle of the photograph, with the light from the distant spiral lensed galaxy as arcs around it. (The apparent path of the light is shown by yellow lines.)

 
Here is what a lens looks like in a photograph taken by the SDSS telescope.
We are looking at it, of course, from the Earth.

If the distant source is directly behind the lensing galaxy, the lensed galaxy is a ring.
587742572151374147 The "Cosmic Horseshoe"
reference: http://arxiv.org/abs/0706.2326v3
The orange galaxy is the massive lensing galaxy.
The distant galaxy is directly behind the massive lensing galaxy, so we can't see it directly. 
Much light from the distant galaxy has been bent towards us by the massive lensing galaxy.
It is concentrated into a ring around the massive lensing galaxy. 
 

If the distant galaxy is not directly behind the massive lensing galaxy, arcs are formed instead.
588013382206357664
reference: http://arxiv.org/abs/0809.4475
The orange galaxy is the massive lensing galaxy.
The lensed galaxy is the white arc. It is much further away than the massive lensing galaxy.


 

photo: HubbleSite
Why look for lenses on SDSS when Hubble Space Telescope pictures can see more detail?

The (Sloan Digital Sky Survey) telescope covers a lot of sky quickly, while other telescopes can look at only a small piece of sky. Computers help set up the SDSS data base. Computers can sort galaxies by size, location and proximity to other galaxies, colours and redshift, if that is available. You can learn to use the SDSS search. But computers cannot recognize shapes.

Galaxy Zoo 2 gets its pictures from SDSS, and help sort galaxies by shape.

People can classify galaxies according to shape, recognize unusual shapes and interactions, and find new objects.
After classifying their galaxy, Zooites can post unusual discoveries on the Forum, and discuss the galaxy with other Zooites. For gravitational lenses, the thread is Possible strong gravitational lenses in Weird and Wonderful.
A scientist may look at the post and think that it is a possible lens, and then the galaxy can be put on the waiting list for analysis by other telescopes. The galaxy could be confirmed as a lens, and Galaxy Zoo could be credited with a find. 

Why are gravitational lenses important?

1. To refine the numbers that we need understand our universe, how and when it started, how it is growing, what will happen in the future. See wikipedia Gravitational lens : Geometry of the Universe.


photo: Chandra
2. To weigh the amount of dark matter around a galaxy.

The amount of bending of lensed light around a galaxy shows how much the galaxy weighs. If it seems the galaxy weighs more than the mass of stars and gas in it, the rest of the mass must be due to dark matter, and we can learn more about what our universe is made of.
This composite image shows the hot gas around the galaxy cluster 1E 0657-56, also known as the "bullet cluster."   Normal matter between the galaxies is shown in pink: dark matter is shown in blue.

photo: Hubble Space Telescope
3. To find galaxies that are normally too far away to be seen.

The concentration of light of distant objects means that we can see galaxies that are very far away that are ordinarily too dim to see.  With the help of gravitational lenses we will be able to see galaxies 13 billion light years away. The edge of our visible universe is about about 13.7 billion years away. So it adds to our understanding of the early universe.

The long bright blue streaky things are the lensed galaxies.
SDSS can only see the biggest and brightest of these.
 
There are three types of gravitational lens
See Wikipedia Gravitational Lens

Strong lensing forms rings, arcs and multiple images. This is what we are looking for in the Forum.
Weak lensing shows only stretching of images.
Micro-lensing shows no change in the lensed object's shape, just in brightness.


I would like to thank Gumbosea for his inspiration and knowledge on the Possible Strong Gravitational Lens thread, and for looking over this guide.  Thanks also to and Pluk, blt and Aprajita for the use of their illustrations. Thanks also the the major contributors to the thread who are getting expert in analyzing pictures for lenses and sharing their knowledge with newbies like me.
« Last Edit: May 29, 2010, 08:49:51 am by Budgieye »

Budgieye

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Re: What to look for using confirmed strong lenses in SDSS
« Reply #1 on: July 28, 2009, 07:02:56 am »
Part 2  What to look for using confirmed strong lenses in SDSS


                     The lensing galaxy has to be a massive galaxy to have enough gravity to bend light.






















This is not a massive galaxy


Spiral galaxies are too little to bend light!
587735695913320507 The Pinwheel Galaxy, posted by Wosret




587728307491897590




This is a massive galaxy.
This elliptical galaxy is probably a thousand times more massive than a spiral galaxy.

Only elliptical galaxies (and preferably many in a cluster) can bend light!
Posted by ElisabethB


The massive galaxies don't actually bend light : they bend space.
The light still thinks that it is going in a straight line.


          Lensed galaxies are a different colour from the massive lensing galaxy

The lensing massive galaxy and the lensed galaxy are at different distances and the lensing galaxy is closer.

The colour of the lensing galaxy

The galaxy that acts as a lens is an massive elliptical galaxy, called LRG or Luminous Red Galaxy.
They are at least a billion years years away, with a redshift (z) over 0.15
This is far enough away so that the white colour of the galaxy is redshifted to yellow, orange or red.
 
The colours described below are the colours as shown on the SDSS pictures.


587733441053065699


yellow colour z=0.2
2 billion light years away

587742572151374147
 

orange colour z=0.4
4  billion light years away

588297863111180358


red colour z=0.6
6 billion light years away


SDSS cannot see normal galaxies further away than z~1.2. These galaxies have their light redshifted into the infrared and the infrared light does not penetrate Earth's atmosphere.


The colour of the lensed galaxy

The lensed galaxies are further away than the lensing galaxy.

Lensing does not change the redshift or quality of the light from the distant galaxy.
Lensing just concentrates the light.
For information on the colour and redshift of galaxies, see Zooite Guide to Spectra

SDSS cannot see ordinary galaxies when they are far away at z>1.2, because all their light gets reshifted into IR (infrared light), and SDSS cannot see IR. So most of the lensed galaxies that SDSS can see will be active galaxies.


Active galaxies produce UV light (ultraviolet light),which is redshifted into visible light that SDSS can see.
These galaxies either have
active star-forming regions that produce UV light or have an
active black hole with hot gas that produce UV light.
If an active galaxy is far away, and so the UV light is redshifted, that light becomes visible as bright blue, bright white (ie blue+green+red), bright green, or red light, depending on how far away it is.



587724650875453828
The "purple"  blob is a star forming galaxy which has been lensed.
It is far away (z=0.779), and should be red.
But it is a star-forming galaxy with UV light, which has been redshifted into blue light.
Most of the ordinary light is still present, though redshifted into red light.
Red + blue  = magenta (though people call it purple).
http://arxiv.org/abs/astro-ph/0112249
Hubble photo in: http://hubblesite.org/gallery/album/entire/pr2003001f/

The shape of the lenses galaxy
Gumosea provides information on shapes found in arcs
 see http://www.galaxyzooforum.org/index.php?topic=6927.msg66286#msg66286

Texture: the lensed galaxies will have a different texture to the lensing galaxy.
Lensing galaxies will have a rough fluffy texture.
Lensed galaxies will have a smoother texture.





Here are some more published strong lenses with an arc visible in SDSS.

The redshift (z) of the lensed galaxies has been proven by spectroscopy

 
z=0.389 

large galaxy z=0.23
small blue arc z=0.389, strong OIII lines
"The Sloan Bright Arcs Survey : Six Strongly Lensed Galaxies at z=0.4-1.4"
2008   http://arxiv.org/abs/0812.3934
588297863115047025
SDSS J104943.14+442035.6
posted by gumbosea

 

~0.6

massive galaxy has z=0.44,
estimate of z for arc is ~0.6
"Hall’s Arc" , a serendipitous discovery of a giant arc in the SDSS data while doing a computer search for lenses.
"A Systematic Search for High Surface Brightness Giant Arcs in a Sloan Digital Sky Survey Cluster Sample"
2004   http://arxiv.org/abs/astro-ph/0701383
587727230523080836
SDSS J014656.00-092952.4



z=0.766

The lensing galaxy is the orange galaxy, with a redshift of z=0.388
The distant galaxy is the pink arc at z= 3.6.
Spectropscopy shows that it is a quasar.
"The SDSS Discovery of a Strongly Lensed Post-Starburst Galaxy at z=0.766"
2003 http://arxiv.org/abs/0804.1487
587739115775197598 
SDSS J082728.83+223253.9
posted by gumbosea



z=0.725

The massive lensing galaxy appears red, with a redshift of 0.274.
The lensed galaxy(s) forms a bluish pink arc with a radius of 4", and a z=0.725
"Two new large-separation gravitational lenses from SDSS"
2008 http://uk.arxiv.org/abs/0806.4188 CSWA 3
SDSS J124032.28+450902.8
588017605222793376
posted by Fluffyporcupine


z=0.776

one LRB and 2 smaller ones z=0.336
bright arc 12.6" long to the southeast z=0.776, faint extension to southwest
"The Sloan Bright Arcs Survey : Six Strongly Lensed Galaxies at z=0.4-1.4"
2008  http://arxiv.org/abs/0812.3934
587741829121638526
SDSS J111310.64+235639.5   


z=0.850

red galaxy at z=0.170, blue arc to west z=0.850
"The Sloan Bright Arcs Survey : Six Strongly Lensed Galaxies at z=0.4-1.4"
2008   http://arxiv.org/abs/0812.3934
587733441053065699
 SDSS J162954.56+352839.4



z=0.985

luminous red galaxy redshift z=0.4517
extended blue arc to south with 3 knots, length 10.1" z=0.985
The Sloan Bright Arcs Survey : Six Strongly Lensed Galaxies at z=0.4-1.4
2008   http://arxiv.org/abs/0812.3934
587733412060987606
SDSS J151118.73+471340.3
posted by Gumbosea



z=0.97

The two massive lensing galaxies at z=0.43
There are two lensed galaxies which form 2 white arcs with a radius of 11"
and have a redshift of z=0.97 and 0.14
"The Cheshire Cat" "Two New Large Separation Gravitational Lenses from SDSS"
2008   http://arxiv.org/abs/0806.4188 Cassowary catalog CSWA 2.1 and 2.2
"lensing two background sources, the first a star-forming galaxy at z = 0.97 and the second a high redshift
galaxy (z > 1.4)
"The Sloan Bright Arcs Survey : Six Strongly Lensed Galaxies at z=0.4-1.4"
http://arxiv.org/abs/0812.3934
588013382200131773 and
588013382200131774
SDSS J103843.59+484917.7 and SDSS J103842.69+484920.2
posted by reddevil013 as Galactic Smiley Face



z=1.018

"SDSS J120923.7+264047: a new massive galaxy cluster with a bright giant arc"
lensing galaxy z=0.55
long purple arc at radius of 10" has redshift of z=1.018 (I think this is the one they analyzed)
2008 http://arxiv.org/abs/0808.0721   CSWA 8
587741600957333763
posted by ElisabethB




588295841784725744
SDSS J113740.05+493635.5
z=1.4
two lensed galaxies at 1.38 and 1.411
lens is two merging galaxies z=0.4483
The Sloan Bright Arcs Survey : Six Strongly Lensed Galaxies at z=0.4-1.4
http://arxiv.org/abs/0812.3934



z=2.0

The lensing galaxy is red at z=0.422.
The lensed galaxy is a white arc with a radius of 5" (?) and z=2.0
"Discovery of A Very Bright, Strongly-Lensed z=2 Galaxy in the SDSS DR5"
2008 "The Clone" CSWA 6   http://arxiv.org/abs/0809.4475
588013382206357664
SDSS J120602.09+514229.5
posted by Chipper Q and gumbosea



2.379

The red galaxy, the lens, is at a redshift of 0.444 (4.6 billion light years)
The distant source is a star-forming galaxy with a redshift of 2.379 (10.9 billion light years)
and forms an almost complete Einstein ring of diameter 10"
"The Cosmic Horseshoe: Discovery of an Einstein Ring around a Giant Luminous Red Galaxy"
2007     http://arxiv.org/abs/0706.2326
587742572151374147
SDSS J114833.13+193003.1


z=2.73

massive galaxy z=0.38
lensed galaxy is z=2.73
There are three images of the distant galaxy in the arc.
Spectroscopy showed that it was determined to be a star forming galaxy.
"The 8 o'clock Arc: A Serendipitous Discovery of a Strongly Lensed Lyman Break Galaxy in the SDSS DR4 Imaging Data"
(named for the time of day when it was found, not the position of the arc)
2006 The 8 O'Clock Arc  http://xxx.lanl.gov/abs/astro-ph/0611138
588290880028999911
SDSS J002240.91+143110.4


« Last Edit: July 13, 2012, 04:16:18 am by Budgieye »

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Re: Part 3 Double quasars in SDSS,... and triple, and quadruple.
« Reply #2 on: July 28, 2009, 07:16:18 am »
Part 3 Double quasars in SDSS,... and triple, and quadruple.

A quasar is a galaxy with an extremely bright centre, or nucleus, where black hole in the nucleus is feeding on stars. We don't see the rest of the galaxy, just the small bright centre.   After its light has been through a lens, the arcs produced are still very small, and look like a tiny points of light.

Galaxy Zooites can't see any shape in these arcs, since the arcs look like stars. We need spectra to distinguish quasars from stars, and we often don't have spectra. Therefore, looking for lensed quasars is not something that we Zooites can easily do.

Also, computer searches of SDSS can easily look for 2 quasars within a certain distance, so obvious examples have already been found. What to look for is two or more stars of exactly the same colour though not necessarily the same size, in close proximity, possibly with a dim red galaxy in between them.

The colours of quasars are not affected by lensing.
There is an excellent display of quasar colour and spectra arranged in redshift order,
by SDSS at Redshift Gallery : Quasars
Object of the Day Saturday 29thAugust 2009  Gravitationally lensed QSO's

 
There are many published examples of double, triple and quadruple quasars. Many have been found using radio telescopes.
SQLS: Lens list
This is a selection of quasars that can be seen in visible light.

   
z=1.41
Those two “stars” are lensed light from one quasar.
This object is the first example of a gravitational lens
the massive lensing elliptical galaxy, seen between them,
lies at redshift  z = 0.355 (3.7 billion ly)
The distant quasar lies at redshift  z = 1.41   (8.7 billion ly)
1979 The Twin Quasar  http://adsabs.harvard.edu/cgi-bin/bib_query?1979Nat...279..381W
"Q0957+561 A, B: Twin Quasistellar Objects or Gravitational Lens?"
587729388218679312
587732583125352514



z=1.73

2003     http://arxiv.org/abs/astro-ph/0312427
"A gravitationally lensed quasar with quadruple images separated by 14.62arcseconds"
   
There have been many lensed quasars found, but this has a wide separation between lensed galaxies
The orange massive galaxy has    z= 0.67
It has two nearby companions at   z=0.67
The lensed quasar is in 4 arcs, at  z=1.73
588297863111180358  SDSS J100434.18+411243.5
588297863111180354
588297863111180355
588297863111180356
588297863111180357



z=2.024

The triple quasar Q1115+080A, B, C - A quintuple gravitational lens image
http://adsabs.harvard.edu/cgi-bin/bib_query?1979Nat...279..381W
PG 1115+080 A gravitational cloverleaf     Hazard, et al 1984, ApJ, 282
Astronomy Picture of the Day March 31, 1999
and Chandra
588017726004396138
588017726004396139



z=2.024

2009   SDSS J082016.11+081215.9    http://arxiv.org/abs/0906.2647
 "A new gravitational lens from the MUSCLES survey: ULAS J082016.1+081216"
The lens galaxy as a faint red object of redshift 0.803
The lensed quasar has a double image (not really visible in SDSS) and z= 2.024
587735349086257357



z=2.237

2009 SDSS J0819+5356
red lensing galaxy z=0.294
lensed quasar, blue 4" to north west, z=2.237,
listed as a star on NED
spectrum evidently a mix of the red galaxy and the quasar
“Five New High-Redshift Quasar Lenses from the Sloan Digital Sky Survey”
2009  http://arxiv.org/abs/0809.0912
587737826214674652
587737826214674651
587737826214674653
 



z=2.241

2009 SDSS J1339+1310
double quasar 
“Five New High-Redshift Quasar Lenses from the Sloan Digital Sky Survey”
2009  http://arxiv.org/abs/0809.0912
587738568175058991
587738568175058992



z=2.701

2009 SDSS J1258+1657
double quasar
“Five New High-Redshift Quasar Lenses from the Sloan Digital Sky Survey”
2009  http://arxiv.org/abs/0809.0912
587742774027878477



z=3.317

2009 SDSS J1400+3134
double quasar
“Five New High-Redshift Quasar Lenses from the Sloan Digital Sky Survey”
2009  http://arxiv.org/abs/0809.0912
587739406254538958
587739406254538957
posted by 1000GGG, AlexandredOr suggested that it might be a lens


z=3.626

2009 SDSS J1254+2235
double quasar
“Five New High-Redshift Quasar Lenses from the Sloan Digital Sky Survey”
2009  http://arxiv.org/abs/0809.0912
587742014361174098
587742014361174099

These quasars have been listed as examples. Since Galaxy Zooites cannot identify double lensed quasars by shape, it is better that we concentrate on arcs and rings.
« Last Edit: July 29, 2011, 06:45:05 am by Budgieye »

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Re: These are not lenses
« Reply #3 on: July 28, 2009, 07:34:08 am »
Part 4 These are not lenses

These examples are NOT gravitational lenses

Since SDSS does not have the resolution of Hubble and other telescopes, we have to use our best judgement, using colour, shape and texture to recognize less obvious lenses.

We can see the thicker star forming regions of spiral arms, but we can't see the thinner regions due to low surface brightness of the outer part. So it looks like objects arranged around a galaxy See low surface brightness galaxies and Phil Marshall's Blog
This is not a gravitational lens. Perhaps there is not enough colour difference.
But the next one might be. When in doubt- post.
587741490889753129  SDSS J081303.24+155216.9

the thick outer arms in galaxies by Phil Marshall's Blog
This is not a gravitational lens.
But the next one might be. When in doubt- post.
588010359598089071 SDSS J081303.24+155216.9


blue star forming areas on the edges of galaxies
This is not a gravitational lens.
But the next one might be.
587731679585566825




satellite galaxies, though it was hoped to be an Einstein Cross
Phil Marshall's Blog
This is not a gravitational lens.These satellite galaxies are the same colour and texture as the centre galaxy
But the next one might be.
587725073919377715SDSS J092622.10-003757.8




hot areas in colliding galaxies we got observing time
This is not a gravitational lens.
 
StephenT posted this in Where does it go?


         587743958884286603   


Ooops. A red star and a galaxy fragment. This is not a gravitational lens.
The beautiful spiral is 587742062136131600
The red star is 587742062136132080



Here are links to articles in Wikipedia.
Einstein ring

Gravitational lens

 

« Last Edit: August 06, 2013, 06:41:27 am by Budgieye »

Budgieye

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Re: Strong Gravitational Lenses in Hubble Space Telescope photos
« Reply #4 on: July 28, 2009, 07:39:01 am »
Part 5 Strong Gravitational lenses in Hubble Space Telescope photos

Some great posts taken from taken from the Possible Strong Gravitational Lenses thread

There are many pictures of strong gravitational lenses taken by Hubble Space Telescope.
See their website:
http://hubblesite.org/gallery/album/exotic/gravitational_lens/

This is "our" Phil Marshall's list of possible lenses from Hubble pictures.

OK everyone, I have made you a webpage:

http://www.slac.stanford.edu/~pjm/HAGGLeS/hlsp/EGS

From there you can download or view the catalog of outputs from our robotic search - you can read the paper at http://arxiv.org/abs/0805.1469

I found Bruno's object - it was picked up by the robot, but downweighted by our conservative human experts! Hmm - we said we wthought it was only "possibly a lens" - but on second thoughts I'm not so sure! Anyway, keep them coming - if you see something cool, and its not in the robot's catalog, game on!

Phil

Here are illustrations from a slide show by Ray Lucas, Space Telescope Science Institute (recommended by c_cld)
slide presentation


A picture by the upgraded Hubble telescope.
The lensed galaxies are the stretched red and blue streaks.
There is detail of the lensed galaxy detail  visible on the large red
A good explanation in Astronomy Picture of the Day 2009 September 21
This galaxy cluster is not in the SDSS footprint, so we can't see it in SkyServer.



Many of these lenses require a fine resolution and cannot be in the SDSS SkyServer pictures.
Here are some comparisions.


Here is a lovely comparison by Pluk,

Taken from http://en.wikipedia.org/wiki/Image:Einstein_Rings.jpg (thanks to gumbosea for the pointer)



I tried looking these up in SDSS, which I think I did correctly by taking (for instance) J073728.45+321618.5 from the image and turning that into ra and dec parameters as ra=07:37:28.45 and dec=32:16:18.5. I tried feeding each thusly acquired pair to the SDSS DR6 Navigate Tool and each resulted in an SDSS object neatly centered in view. Alas, none showed any sign of the rings we're seeing above.

I think I'm doing it correctly, still I don't see even a hint of a ring anywhere. ???

587728669337584268

J073728.44+321618.6
587731499183833286

J095629.77+510006.3
588295840712949880

J120540.40+491029.2
588010879838322829

J125028.26+052349.0
588007005792567441

J140228.20+632133.2
587722951697957575

J162746.44-005357.5
587729409150681281

J163028.15+452036.2
587727179519033515

J232120.93-093910.3


edit:

guess this explains it:

The article on rings contains a montage of rings image by the HST, the 'sharp and clear' rings mention earlier. When you look them up in SDSS DR6 using the 'navi' page, you can't see any arc; they are washed out by the central galaxy (not a big enough ring radius).




another from Aprajita

587728307491897590
 

Well spotted! This is a region that contains a known Massive Cluster (MACS J1115.8+0129) that has been selected in the X-ray (z~0.35). These massive clusters are known to be sites where strong gravitational lensing is likely. Indeed the reddish arc is very likely to be a lensed galaxy. I have attached a HST preview image (png file) of this region with much higher resolution than the SDSS images in which elongated arcs can be clearly seen in this region (but please note the orientation is different to that of the SDSS image - that has north up and east to the left - so don't forget to take that into consideration when you visually compare the two images). The red arc is SDSS 111551.89+012946.7 - marked with a "2" and the lensing galaxy SDSS J111551.90+012955.0 marked with a "1".

Aprajita.





from blt

Hubble has found a double Einstein ring in the SDSS data. I believe that this is the Galaxy:  http://cas.sdss.org/astro/en/tools/explore/obj.asp?id=587735344263856391



Read about it at http://hubblesite.org/newscenter/archive/releases/2008/04/fastfacts/

Here are the Hubble pics:




Quote
he massive foreground galaxy is almost perfectly aligned in the sky with two background galaxies at different distances. The foreground galaxy is 3 billion light-years away. The inner ring and outer ring are comprised of multiple images of two galaxies at a distance of 6 billion and approximately 11 billion light-years.

SLACS team member Adam Bolton of the University of Hawaii's Institute for Astronomy in Honolulu first identified the lens in the Sloan Digital Sky Survey (SDSS). “The original signature that led us to this discovery was a mere 500 photons (particles of light) hidden among 500,000 other photons in the SDSS spectrum of the foreground galaxy,” commented Bolton.

“The twin rings were clearly visible in the Hubble image”, added Tommaso. “When I first saw it I said ‘wow, this is insane!’ I could not believe it!”

The distribution of dark matter in the foreground galaxies that is warping space to create the gravitational lens can be precisely mapped. In addition, the geometry of the two Einstein rings allowed the team to measure the mass of the middle galaxy precisely to be a value of 1 billion solar masses. The team reports that this is the first measurement of the mass of a dwarf galaxy at cosmological distance (redshift of z=0.6).

From http://www.sciencedaily.com/releases/2008/01/080110102319.htm

Also posted to Google Sky with overlays http://bbs.keyhole.com/ubb/showflat.php/Cat/0/Number/1093420/an/0/page/0#1093420




Visible lenses in the Hubble picture of Abell 1689 seen in SDSS
 
 
587724650875453478



 

Here is Abell 1689 in SDSS.                                                            Here is part of Abell 1689 with the lensed galaxies pointed out.

The magenta galaxies are:
587724650875454355 and 587724650875453828
http://skyserver.sdss3.org/dr8/en/tools/explore/obj.asp?id=1237655500272500870 in dr9

 
http://hubblesite.org/gallery/album/entire_collection/pr2003001f/
Here is a link to the picture of Abell 1689 that Hubble took. It is nearly the same scale, but you have to put your head sideways to your right to put north at the top and make it look the same as SDSS.The arc is white, and there is see the some structure of a galaxy in the arc.
http://hubblesite.org/gallery/album/exotic_collection/pr2008008b/large_web

 
In the SDSS image, the magenta galaxies are near the bottom.
In Hubble, the corresponding arcs are are the larger stretched galaxies in the top left corner.
 
magenta galaxy at 5:30 in SDSS Skyserver, and the same galaxy in Hubble
Remember in Hubble, north is on the right, so the picture has a quarter turn.
http://hubblesite.org/gallery/album/entire/pr2003001f/
587724650875453828
  

magenta galaxy at 6:30.
In the Hubble image of the whole cluster, the arc is white and looks like a galaxy.
NED says it has a red shift of z=0.69
587724650875454355


Lovely astronomy picture of the day 2009 Aug 23


Unfortunately, it is outside of the SDSS sky


Apologies if this has already been posted - I did search honest! Just found it and was amazed:

Hubble Captures a "Lucky" Galaxy



« Last Edit: August 06, 2013, 06:42:38 am by Budgieye »

Budgieye

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Part 6 Hubble Zoo lenses
« Reply #5 on: July 28, 2009, 07:42:44 am »
part 6 Lenses from Hubble Zoo

see   69 Lenses from Hubble by c_cld

http://aegis.ucolick.org/images/strong_lenses.jpg



                                                             12016031 spectrum
http://zoo-hst.s3.amazonaws.com/12016031.jpg
587735694840758754
THE DEWDROP                                                         
posted by ElisabethB
12004138 spectrum
http://zoo-hst.s3.amazonaws.com/12004138.jpg
an Einstein's cross
posted by c_cld
 


EGSD2 J141753.4+523540
SDSS J141753.34+523539.3  DEEP2 12016405
:o, very nice possibility !  :D

Yeah, I like this one too! Do you think that's a faint counter-image at 10 o clock? I think it might be. I'll check my robot's reject list to see if this is there... :-)

Phil


OK everyone, I have made you a webpage:

http://www.slac.stanford.edu/~pjm/HAGGLeS/hlsp/EGS

From there you can download or view the catalog of outputs from our robotic search - you can read the paper at http://arxiv.org/abs/0805.1469

I found Bruno's object - it was picked up by the robot, but downweighted by our conservative human experts! Hmm - we said we wthought it was only "possibly a lens" - but on second thoughts I'm not so sure! Anyway, keep them coming - if you see something cool, and its not in the robot's catalog, game on!

Phil

Hi Phil, thanks for the help
Afraid I cannot open the catalog: are there any tools I need to see it on a Vista machine?
Thanks again

Hi Bruno, hi C_cld,

Sorry about this - plain text tends to be easily viewed from linux systems... I put a little more effort in and made a quick html table to help you guys out a bit, its linked from the same webpage but the url is http://www.slac.stanford.edu/~pjm/HAGGLeS/hlsp/EGS/lenstable_optimistic+humanclassification.html

Notice that we only pre-selected about 1000 objects, for being bright red galaxies - massive ellipticals are what we expect most lenses to be. You'll also notice that a simple brightness and colour selection leads to a few interloping stars and so on, but the robot seems able to cope with that. It would have been better to do a morphological selection - but we did not have you guys to help at the time!

If you find objects you think are lenses, please do post them before checking the robot results: as your recent candidate shows, robots and experts can easily miss things... And keep an eye out for lensing by galaxies that are neither bright nor red! :-)

Good luck!

Phil

First I thought it was a SDSS image but no, it is a Hubble one


http://zoo-hst.s3.amazonaws.com/13025503.jpg
Hi H.kohler
according to NED/ Simbad you hit the jackpot 
SL2S J142031+525822 -- Gravitational Lens
SDSS J142031.80+525822.0  http://cas.sdss.org/dr6/en/tools/explore/obj.asp?id=587735665306763476
DEEP2 13025503
  8)

 
    AEGIS / Hubble
DEEP2 12024284 HST J141833+524352 G Lens

*SDSS J141833.10+524352.3       14h18m33.1s +52d43m52s G_Lens >30000  0.462536

Thursday, 8 November 2012: A New Einstein Cross Gravitational Lens by Jean Tate
http://www.galaxyzooforum.org/index.php?topic=280490.msg619783#msg619783



 
« Last Edit: August 24, 2013, 07:17:06 am by Budgieye »

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Part 7 Index to the Possible Strong Gravitational Lens thread
« Reply #6 on: July 28, 2009, 07:43:30 am »
 Part 6 Index to Gravitational Lenses in the Forum

the 8 o’clock arc, where it all started after the posting on OOTD[Object of the Day] p2
The Cosmic Horseshoe: a visible ring p5
published weak Einstein lenses that SDSS can’t see p6
how to use the SDSS database p10-12
using the Petrosian radiuswhen doing an SDSS databasesearch p12
An overview of lenses which explains arcs, dots and symmetry p20
Hall’s Arc and symmetry p41
bending of light around galaxies p78
Double Einstein ring barely seen in SDSS picture p97
Hubble and SDSS comparison picture p104
A strong SDSS lens is published p115
suggestions from an astronomer p122
Does this help? p156
Use of the photometric z (as opposed to the usual spectroscopic red-shift z) to estimate distance of arcs and smokedots p157
Abell 1689: Links to published Hubble/Chandra X-ray picture and the SDSS picture p182
visible arcs in Abell 1689 p205
these ones are not lenses p205
The Cassowary catalog p205
The Twin Quasar p208
reddish arc in a massive cluster p214
69 Lenses from Hubble by c_cld p404

Dr Phil Marshall's list http://www.slac.stanford.edu/~pjm/HAGGLeS/hlsp/EGS p321 and http://arxiv.org/abs/0805.1469]paper
 
Here are links to articles in Wikipedia.
Einstein ring
Gravitational lens

Evidence of lenses will be found around elliptical galaxies, because they can be a thousand times bigger than spiral galaxies, and so have more gravity to bend the light. So look for unusual colours or shapes around yellow or orange "blobs".

A perfectly aligned lensed galaxy should form a circle around the lensing galaxy. The alignment is rarely perfect so the circle is broken up into arcs. The telescope of SDSS is not powerful enough to see these arcs as galaxies, we see them as fuzzy dots, arranged in a concentric and balanced pattern. They are not the same colour as the lensing galaxy, and have a blue, purple, green or white colour, though extremely distant ones can be red. Paired items should be the same colour.

Request from astronomer : wants arcs on both sides of the galaxy to help with calculations of mass of galaxy. But if we can find an arc on one side, a bigger telescope might find an arc on the other.
Hubble space telescope finds evidence of Population III stars in a red arc, a lensed galaxy.

Here is an animation of lensing, showing the arcs formed
Object of the day 30th August 2008
The SDSS Discovery of a Strongly Lensed Post-Starburst Galaxy at z=0.766[/url]

OOTD Tuesday 26th Febraruy, 2009. 67 gravitational lenses from the Cosmos survey by pluk
OOTD Saturday 12th April 2008 a gravitational cloverleaf
OOTD Friday 11th April, 2008 a strongly lensed, post-starburst galaxy
Object Of The Day Sat 7th Feb 2009
Wednesday, 8th February, 2012: More Strong Lenses in SDSS

Quote from zooKeeper Kevin on galaxies with rings:  Good point... rings and lenses may look alike. My first suggestion to distinguish them is that a gravitational lens should be "thin", whereas a ring would be more extended. Compare the ring to the horeshoe, the lens is much thinner. rings around galaxiesAnother good indicator is that most strong lenses (while circular) don't go all the way around. However, these are just general ideas, not hard rules, so if in doubt, post it here

Checklist for items which can have fooled me and the list will surely grow:
blue stars (round, with an even colour throughout) 588017571384394232 (Caution:Blue "stars" could also be quasars, which could form part of a lens pattern. Without a spectrum, it is guesswork)
bits of torn off galaxies fragment
the thicker star forming regions of spiral arms, and we can't see the thinner regions due to low surface brightness spiral arm?
the thick ends of bars in galaxies
paired relativistic jets coming out of black holes
satellite galaxies 587731679585566825
hot areas in colliding galaxies we got observing time
coincidence http://www.galaxyzooblog.org/2009/01/16/egzelens-update-hst-pre-imaging/
« Last Edit: February 08, 2012, 08:20:27 am by Budgieye »

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Re: Zooite Guide to Gravitational Lenses
« Reply #7 on: July 28, 2009, 07:44:10 am »

  The massive galaxies don't actually bend light : they bend space. The light still thinks that it is going in a straight line.
« Last Edit: July 13, 2012, 04:09:54 am by Budgieye »