Random object / merger + bright object
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Curious if there is a sure way to identify the central blue object as a star, as it seems (to me) to be related to the merger. And also doesn't really look completely round, with a blue halo.
Can't find any mention in ADS, and unsure of all the mentiones in NED because they seem to pinpoint other objects or empty space.
http://legacysurvey.org/viewer?ra=320.2600&dec=3.8040&zoom=16&layer=decals-dr2
SDSS DR12
http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237678777923928070Posted
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by Budgieye moderator
Without a spectrum, we can't be sure. Either white dwarf star in our galaxy, or a blue pea in a nearby galaxy..
Looking at a galaxy redshift chart https://talk.galaxyzoo.org/#/boards/BGZ0000007/discussions/DGZ0000ulp?page=2
I see that there are no blue peas further than z=0.04 , since they get redshifted to green.
So the blue blob cannot be a blue pea. So it must be a white dwarf star or blue star in our galaxy.
SDSS
http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237678777923928070
neighbour is photoz 0.2 and is 0.107 arc min or 6 arc-sec away.
http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237678777923928073
1 arc minute = 60 arc seconds
0.1 arc minute = 6 arc seconds, or about a little finger's width on a screen.
The SDSS picture is about 30" wide. which is 0.5 arc minute, which NED uses.
The 5" bar is 5 arc-seconds or 0.08 arcmin.
The naming seems a bit confused since they are so close together.
NED (indicated by the triangle) has it listed as GALEXASC J212102.45+034814.7 21h21m02.4s +03d48m15s UvS which is 0.010 arcmin away, which is 0.6 arcsec away.
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by Ghost_Sheep_SWR in response to Budgieye's comment.
Thanks for the clear analysis, very helpfull.
which is 0.5 arc minute, which NED uses.
I didn't know that, explains a lot of past confusions. With your recent post of the gravitational lens / dark matter dwarf for instance, in NED / SDSS DR12 there are a lot of galaxies carrying the same name around, also one nearby that's called SPD 81 lens, which isn't the right galaxy
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by Budgieye moderator
You're welcome. 😃
Usually, if an object is 2" or 0.03 arc min or less away from a target, I usually decide that they are the same object. Your target area is a bit crowded though.
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Just for completeness, here are the objects i was referring to. Could cause some confusion I reckon 😃
Press 'Common name';
Real SDP 81
http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237648722285101574Fake SDP 81 objects
http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237648722285101258http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237648722285101570
http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237648722285101569
Object [NHD2010] SDP 81 lens
http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237648722285101663Posted
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by Budgieye moderator
I think the additional objects are probably mentioned in papers about the lensing system, either as part of the lensing system, or rejected as being part of the system. I can't access the paper I wanted, I would have to pay http://mnras.oxfordjournals.org/content/440/3/1999
but the objects looked at are here
The first link is easy.
Real SDP 81 http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237648722285101574
http://cdn4.sci-news.com/images/2016/04/image_3788-SDP-81-Dwarf-Galaxy.jpgpublished image, red arc is 3" high, and SDSS image at same scale
http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237648722285101574
center target galaxy SDSS J090311.57+003906.5 09h03m11.6s +00d39m07s G >30000 0.299640
red arc H-ATLAS J090311.6+003906 09h03m11.6s +00d39m06s G_Lens >30000 3.042000
Fake SDP 81 objects
http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237648722285101258
http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237648722285101570
This appears to be a galaxy in the purple triangle. I don't know why it has a common name same as the lensing system, maybe it was mentioned in a reference as being part of the system for modelling purposes? A guess...
Maybe the same with the others?
a star http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237648722285101569
another star http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237648722285101663
[NHD2010] SDP 81 lens 😕/skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237648722285101663
[NHD2010] appears to be a survey named after the authors (Negrello+Hopwood+De Zotti+, 2010)
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by Budgieye moderator
By the way, the blue "star" at the left is a quasar galaxy, and quite distant as the Lyman alpha peak is present.
http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237648722285101461
more info
SDSS website: Redshift Gallery: Quasars http://classic.sdss.org/gallery/gal_zqso.html Excellent selection of quasar spectra from z=0.1 to 5.0
Galaxy Redshift Chart http://talk.galaxyzoo.org/#/boards/BGZ0000007/discussions/DGZ0000ulp?page=2 has quasars from near to very far.
Spectra guide for SDSS images in Galaxy Zoo Talk http://talk.galaxyzoo.org/#/boards/BGZ0000001/discussions/DGZ0000ulp?page=3&comment_id=53fef2ee3d5a77490c0001b6 has some spectra of quasars
SDSS website: Quasar spectra http://www.sdss.org.uk/dr7/en/proj/challenges/quasars/
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by Ghost_Sheep_SWR in response to Budgieye's comment.
I think the additional objects are probably mentioned in papers about
the lensing system, either as part of the lensing system, or rejected
as being part of the system.That would make kind of sense to me I guess. Although SDSS DR12 showing this as their common name is rather silly then, some being far away from the actual galaxy. And seeing the video of the lensing all this is happening really close to SDP 81, no other galaxies are contributing to the lensing of the background galaxy.
I can't access the paper I wanted, I would have to pay
This one you mean?
http://arxiv.org/abs/1311.5898
http://classic.sdss.org/gallery/gal_zqso.html
This is really cool to see them sorted by redshift, all the spectral lines look like a wave moving to the right. Makes spectral redshift really visibly obvious here.And quasars seem only very slowly to loose brightness (eg photometric appearance) with highly increasing redshift nice! 😃
That last link is dead.
Thanks
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by Budgieye moderator
A lot of the indexing is done by computers.
Thank you for the paper link, I must have been quite dim.
new link for SDSS learn about quasar spectra http://cas.sdss.org/dr7/en/proj/advanced/quasars/
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