Author Topic: Thursday 14th July 2011: a binary quasar  (Read 6352 times)

Alice

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Thursday 14th July 2011: a binary quasar
« on: July 14, 2011, 05:48:04 pm »
Today's Object of the Day looks like a sweet little pair of snowballs. It will not astonish you when I say that as far as I know it isn't, of course. :D

587732769986641971

Posted by c_cld, zutopian (as a reference), aaaand . . . JeanTate, on UniverseToday and here. I'll be saying some different things about it, though. :D

I did not come across this object on the forum, but in Boston on the conference. I was looking at a poster about quasars, and I actually found myself understanding enough of this one on a corner to go on reading. Next moment, a friendly chap came up behind me saying, "I'm here, what do you want to know?" We went through the bits I did and did not understand. The chap in question is Paul Green, and his office apparently is opposite that of Jonathan McDowell, whose artwork I showed you for my Arp Art Object of the Day (and who joined the forum specially to reply to paulrogers's question!).

So I learned that this binary quasar has the catchy name of SDSS J1254+0846, which meant it's going to be in the SDSS database. I went to NED to do a search. It didn't work. Annoyed, I Googled it and found Green et al's original paper. It's about the fact that this is not just any old galactic merger but two quasars merging - what a terrific storm will blow up when the supermassive black holes hit :o More usefully for my current purpose, it gave me the full name of the object, the even catchier SDSS J125455.09+084653.9.

NED gave me the ra and dec. I went along to a random SDSS page and punched them into the "search by ra,dec" box on the top left. SDSS did not like that.

This was annoying.

So I sought the suggestions of Miss Oxford Visitor, i.e. Stellar190. She reminded me about MAST. That gave me a table of results which refuses to reproduce itself if I link to it, but the top one offered an ra and dec SDSS did like (193.729703958073 and 8.78158992294324). Success! (Moral: if you give up on technology, get someone younger to explain it to you.) Incidentally we did a similar search a couple of months ago to find a binary white dwarf - see this old Object of the Day.

NED also showed me a FITS file and told me it didn't have any spectral data. SDSS has a spectrum; here it is, complete with delicious broad quasar-ish peaks.


Anyway, why you might ask am I rehashing an old subject?

Because Paul Green believes, and his poster stated, that this twin quasar is not as rare an object as you might think. Out of about a million known quasars, about 200 have been confirmed as binaries - and even in a younger, thus denser Universe, out of what's sampled, that's a higher population of binaries than should occur by randomness in that environment. His poster explores whether there is anything that triggers the growth of quasars - could one affect another, or could a single mechanism be responsible for binary quasars, for example - and as with a lot of science, there is no "smoking gun" anything yet. Chandra has looked at 7 binary quasars; this one got famous through its obvious tidal tails created by their galaxies merging.

The two AGNs are only about 70,000 light years apart; given that a spiral galaxy such as our own is 100,000 light years across, this is very close. Here is Chandra's picture of it. I wonder if Zooites could hunt for more? Yet another proposal to submit, perhaps? ;D



You'll find a small article about this object, and five other small articles, by me in August's Astronomy Now magazine.
« Last Edit: July 14, 2011, 05:50:25 pm by Alice »

paulrogers

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Re: Thursday 14th July 2011: a binary quasar
« Reply #1 on: July 14, 2011, 06:24:00 pm »
Wonderful post, Alice!  ;D ;D ;D ;D ;D

So I sought the suggestions of Miss Oxford Visitor, i.e. Stellar190. She reminded me about MAST. That gave me a table of results which refuses to reproduce itself if I link to it, but the top one offered an ra and dec SDSS did like (193.729703958073 and 8.78158992294324). Success! (Moral: if you give up on technology, get someone younger to explain it to you.)

 :D :D

[soapbox mode=on]
It seemed HR departments seemed to believe something similar to this when I was in my late 40's and 50's, trying to get a job in IT. :P  Nobody knew anymore how to evaluate IBM mainframe experience, thought I was an old dinosaur.  Need I remind anyone of "Jurrasic Park"? ;)  So when I turned 60 I started building the Linux systems I (safely) use now for anything to do with the insecure, dangerous world of the Internet--from scratch. ;D  Old dinosaur, indeed! >:(  Hrumph! >:(

It doesn't matter the age, sometimes knowledge and experience come with increasing age.  Find someone with the knowledge you need--grey-haired or pimpled!  Stellar seems to be exceptional. ;)
[soapbox mode=off]

Alice

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Re: Thursday 14th July 2011: a binary quasar
« Reply #2 on: July 14, 2011, 06:28:17 pm »
A completely fair point, Paul! And a great many other people older than me know more about computers, too. It just often seems to work in my case. It was an invariable humiliation for me and other teachers in teaching. Government guidelines state that as much technology as possible must be used in the classroom (I was once deemed to have taught an unacceptable lesson because I had drawn a picture of a boat on the board rather than prepare a powerpoint slide of a picture of a boat) - none of which most teachers knew how to use. Projectors sticking out of the ceiling, interactive whiteboards, you name it. The kids on the other hand could work them all perfectly and that was how most lessons began ::)

waveney

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Re: Thursday 14th July 2011: a binary quasar
« Reply #3 on: July 14, 2011, 06:35:42 pm »
Searching for binaries depends on a means of telling that the second object is also a Quasar - the other one in this case 587732769986641972 is not flagged as such by SDSS.   So what would one search for?  Perhaps an object close to a quasar, with a similar difference in magnitude in each of the filters In this case about  2.05 +/- 0.15.   Sounds like a task for CasJobs...

(I also know about computers)
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Alice

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Re: Thursday 14th July 2011: a binary quasar
« Reply #4 on: July 14, 2011, 06:38:05 pm »
(I also know about computers)

Really? I'd never noticed :o ::) :D

paulrogers

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Re: Thursday 14th July 2011: a binary quasar
« Reply #5 on: July 14, 2011, 06:40:13 pm »
Let's not "get started", eh? ;) ;D ::) :P :-*  (But, Oh, I'd sure like to!  Comes with being an old curmudgeon.)  Suffice to say technological skill does not equate with either knowledge nor wisdom, no matter how it impresses others of the rule-imposing generation. ;)  That Stellar was a good person to ask has far, far less to do with her age than Stellar being stellar. ;D

AlexandredOr

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Re: Thursday 14th July 2011: a binary quasar
« Reply #6 on: July 14, 2011, 07:10:46 pm »
Great and fascinating OotD !

Baby star opening its eyes on the Universe.

RandyC

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Re: Thursday 14th July 2011: a binary quasar
« Reply #7 on: July 14, 2011, 08:12:34 pm »
I would almost guarantee that those are background quasars and the spiral galaxy is in the foreground. They may or may not be binaries depending on the individual redshifts of the background quasars. I call this phenomenon "Excitation Volume Galaxies" and is similar to how car headlights work.
Randy

c_cld

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Re: Thursday 14th July 2011: a binary quasar
« Reply #8 on: July 14, 2011, 08:19:07 pm »
I wonder if Zooites could hunt for more?


Thanks Alice for talking of binaries which show up of two kinds: visual and spectroscopic;
When I posted this 587732769986641971 I first cited the Paul J. Green & al paper, that says
Quote
The pair was targeted as part of a complete sample of binary quasar candidates with small transverse separations drawn from SDSS DR6 photometry
.

So I think the CAS jobs has been already done.  ;D

What you forget about a new hunt is to begin with some bibliography: Paul Green was not the first nor the last to publish as you could see by searching on catalogs:
J/AJ/131/1            Binary quasars in the SDSS                (Hennawi+, 2006)
Quote
Abstract:
    We present a sample of 221 new quasar pairs with proper transverse
    separations Rprop<1h1Mpc over the redshift range 0.5<z<3.0,
    discovered from an extensive follow-up campaign to find companions
    around the Sloan Digital Sky Survey (Cat. VII/243) and 2dF QSO
    Redshift Survey (Cat. VII/241) quasars. This sample includes 26 new
    binary quasars with separations Rprop<50h-1kpc ({thetas}<10"),
    more than doubling the number of such systems known.

J/ApJ/678/635 369   Spectroscopy of quasar binary candidates (Myers+, 2008)  54 candidates
Quote
Abstract:
    We present spectroscopy of binary quasar candidates, with component separations of 3"<=Δθ<6", selected from SDSS DR4 using
    kernel density estimation (KDE). Of our 27 new quasar pair observations, 10 are binary quasars, which doubles the number of known
    g<21 binaries with 3"<=Δθ<6" separations. Several of our observed binaries are wide-separation lens candidates that merit
    additional higher resolution spectroscopy, as well as deep imaging to search for lensing galaxies.

arXiv:0908.1998 Gregory Shields & all:  A Search for Binary Active Galactic Nuclei: Double-Peaked [OIII] AGN in the Sloan Digital Sky Survey
Quote from: Gregory Shields
These objects were identified by means of a visual examination of 21,592 quasars at z < 0.7 in SDSS Data Release 7 (DR7). ... Only two give the appearance of possibly being optically resolved double AGN in the SDSS images, but many show close companions or signs of recent interaction. ... Previous studies indicate that 0.1% of SDSS quasars are spatially resolved binaries, with typical spacings of ~10 to 100 kpc. If a substantial fraction of the double-peaked objects are indeed binaries, then our results imply that binaries occur more frequently at smaller separations (< 10 kpc).

In conclusion I think that such a hunt is unworkable by only visual inspection of SDSS images where the resolution is too low: HST and Chandra deep resolution are needed!  :-[

Lightbulb500

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Re: Thursday 14th July 2011: a binary quasar
« Reply #9 on: July 14, 2011, 08:24:30 pm »
8)
A lovely OOTD Alice, and to think all this wonder was hidden from view.
The whole thing could easily have been overlooked, thank goodness it hasn't been ;D

Alice

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Re: Thursday 14th July 2011: a binary quasar
« Reply #10 on: July 14, 2011, 08:56:00 pm »
Yeah. Paul told me it's not easy to get Chandra time. What he really wants to look for is more tidal tails - which shows whether or not it's just a couple of quasars that seem near to each other, or whether there's actually interaction. The good thing is Hubble can also find things like that :)

Love your post c_cld ;D

waveney

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Re: Thursday 14th July 2011: a binary quasar
« Reply #11 on: July 14, 2011, 09:21:32 pm »
Quote
The pair was targeted as part of a complete sample of binary quasar candidates with small transverse separations drawn from SDSS DR6 photometry
.

So I think the CAS jobs has been already done.  ;D

That was on DR6 - we now have DR8 which covers quite a lot more objects - Cas Jobs search being written (probably for first run tomorow)
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Budgieye

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Re: Thursday 14th July 2011: a binary quasar
« Reply #12 on: July 14, 2011, 10:11:42 pm »
125455.09+084653.9

I went into SDSS dr7  navigator and entered
ra  12:54:55.1         dec    08:46:53.9

and got it first time.   :)
You may have had wrong format, or too many decimal places at the end


paulrogers

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Re: Thursday 14th July 2011: a binary quasar
« Reply #13 on: July 14, 2011, 10:59:11 pm »
In conclusion I think that such a hunt is unworkable by only visual inspection of SDSS images where the resolution is too low: HST and Chandra deep resolution are needed!  :-[

Don't we all wish Apache Peak Telescope could be boosted to orbit and we could have SkyServer with HST resolution!  ;D ;D ;D

No?  :'( :'( :'(

Alice

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Re: Thursday 14th July 2011: a binary quasar
« Reply #14 on: July 14, 2011, 11:08:29 pm »
125455.09+084653.9

I went into SDSS dr7  navigator and entered
ra  12:54:55.1         dec    08:46:53.9

and got it first time.   :)
You may have had wrong format, or too many decimal places at the end

Now I know who to ask next time :D