Author Topic: Rare galaxy types in Hubble Zoo - what to look for, where to post  (Read 27169 times)

NGC3314

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There are a few rare (and very interesting) kinds of galaxies that don't necessarily get captured properly by the classification questions, and we want to catch them via forum postings. I'l show some examples here, and describe how to pick them out.


Ring galaxies

In ring galaxies, the whole galaxy is the ring. There may or may not be a nucleus, and when one is present it is often off-center in the ring. There are some great examples from the Sloan images used in Zoo 1 and Zoo 2:



VV 788 = UGC 7683

II Hz 4

SDSS J113843.66+120802.1, also known as "The Scream"


These are different from ringed galaxies, where the outer parts of a spiral disk have been reshaped into a complete ring (or a pair of spiral arms so tightly wrapped as to nearly make a continuous ring). Here are some ringed galaxies from the SDSS:

IC 3075

NGC 2859

The ones just above - ringed systems -  should already be captured by the question tree in Hubble Zoo. Please post Hubble examples of ring galaxies on the forum here. They have special interest, resulting from collisions in which a dense galaxy falls through the disk of a spiral. The reaction to this massive, temporary change in the gravitational environment reshapes the disk of the spiral into an expanding ring, often lit up with regions of new star formation (so such rings are often distinctly blue). Comparing the SDSS and Hubble statistics of ring galaxies traces the cosmic history of this kind of galaxy collision.

There are similar-appearing ringed galaxies, where almost all we see is the central bulge and a ring of tightly wrapped spiral segments. The classic example is Hoag's object, shown just below (and in an excellent Hubble image). Go ahead and post these in the thread I just set up; they are also rare, and it may take additional data to distinguish these from collisional rings.


Polar-ring galaxies

Polar rings are large structures encircling a spiral or lenticular galaxy, often at right angles (over the poles of the galaxy, hence the name). They are easiest to recognize when the central galaxy is nearly edge-on and the ring is seen at a shallow angle. Here are some examples from Zoo 1:

UGC 9796

Mkn 803N

Mkn 1477

Like ring galaxies, polar rings can be signs of galaxy interactions. In this case, at least some of them are the remnants of smaller galaxies disrupted by the gravity of a larger one, remaining coherent for a long time only when their orbits take them nearly over the poles of the bigger galaxy's disk. And again as for ring galaxies, tracing their incidence over cosmic time can tell us about the history of galaxy collisions, a major factor in the evolution of galaxies.

You can post Hubble candidates for polar rings in this thread started by Tsering.

Overlapping Galaxies

These are a personal favorite of mine! When we see two galaxies whose images overlap, but which are not actually merging or interacting so as to distort their shapes, we can estimate the amount of absorption produced by dust in the foreground galaxy. People are still better than software at screening these out from the more numerous pairs which show distortion due to interaction (some programers have looked at some of our Zoo 1 sample to try to improve their algorithms). Once again, this ties in to the development of galaxies over cosmic time, as well as to our understanding of the content of the galaxy (once we know how to correct for the light lost to dust). The classic Zoo increased the available sample of these 100-fold, and comparison with Hubble results was an important long-term goal. Here are some examples of overlaps from the SDSS:

NGC 450/UGC 807

SDSS J013317.83-003924.0

SDSS J023345.46+210832.5

Please post more Hubble overlaps in this thread started by Lovethetropics. You could watch as well for possible lanes or disks of dust extending a long way from the visible galaxy, seen only where they cross another one. There are only a couple of examples known, but these are especially important (what makes them different?)



(This will probably be edited as we find more categories needing special attention!)
« Last Edit: April 26, 2010, 02:42:12 pm by NGC3314 »

Anaclaudia

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Re: Rare galaxy types in Hubble Zoo - what to look for, where to post
« Reply #1 on: April 27, 2010, 02:16:12 am »
great topic, thanks for the info!

billlaw

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Re: Rare galaxy types in Hubble Zoo - what to look for, where to post
« Reply #2 on: May 02, 2010, 04:04:20 pm »
Proto Barrd?

http://zoo-hst.s3.amazonaws.com/90003887.jpg

I have posted this one before!
-Bill
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Half65

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Re: Rare galaxy types in Hubble Zoo - what to look for, where to post
« Reply #3 on: May 05, 2010, 07:30:45 am »

Blackprojects

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Re: Rare galaxy types in Hubble Zoo - what to look for, where to post
« Reply #4 on: June 20, 2010, 12:48:36 pm »
Hi Bill

This Galaxy Looks like the Core is below the Arms that may be Rings Not Something I have Seen before is this something that has been encounterd before?

12028287


paulrogers

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Re: Rare galaxy types in Hubble Zoo - what to look for, where to post
« Reply #5 on: June 21, 2010, 05:57:56 am »
Hi Bill

This Galaxy Looks like the Core is below the Arms that may be Rings Not Something I have Seen before is this something that has been encounterd before?

12028287



Looks to me like we're looking at the bottom side of a tilted but not quite edge-on spiral galaxy with a rather large round, rather bright, core volume and a "dustlane".  ::)  I'd say this one screams AGN to me.
« Last Edit: June 21, 2010, 06:01:46 am by paulrogers »

smj

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Re: Rare galaxy types in Hubble Zoo - what to look for, where to post
« Reply #6 on: July 07, 2010, 03:43:52 am »

ID: AHZ10002wh
Magnitude: 16.8707 ± 0.0002
Redshift: 0.142600

Any idea where to post this beautiful and exceptional galaxy?  Is this a spiral embedded in stellar or dust cloud?  Is what looks like a golden edge to a spiral galaxy really a dust lane and is it in the surrounding larger object or is it closer to us than that object?

smj

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Re: Rare galaxy types in Hubble Zoo - what to look for, where to post
« Reply #7 on: July 07, 2010, 03:52:48 am »
Re: Reply #7

It is even more spectacular in reverse image:


Looks like a ring galaxy with a massive globular center all surrounded by or merging with an even larger irregular galaxy or dense dust cloud.  So where does it really belong?

paulrogers

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Re: Rare galaxy types in Hubble Zoo - what to look for, where to post
« Reply #8 on: July 07, 2010, 04:56:20 pm »
Wow! :o :o :o  Gorgeous!  :D  Very cool. 8)

I'd say that's a quite late-stage merger.  It's not quite "settled" yet.  "Globular cluster" is a name usually associated with associations of hundreds or thousands of stars here in our Milky Way, remnants of "former meals".  I think the "eater" in this case was a large elliptical galaxy.  There is a dust lane visible, but the fuzzy bright arms are not dust, but stars!  They're still getting flung about.  Gravity will pull most of them in, eventually.

smj

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Re: Rare galaxy types in Hubble Zoo - what to look for, where to post
« Reply #9 on: July 07, 2010, 07:46:28 pm »
so where is the right forum topic to post this one?

paulrogers

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Re: Rare galaxy types in Hubble Zoo - what to look for, where to post
« Reply #10 on: July 08, 2010, 03:59:45 pm »
so where is the right forum topic to post this one?
It might be debatable whether it's the result of a merger, as I'm guessing, But I think you'd get no quibbles at all with posting it as a spiral, or a thread for favorites or spectacular sights.  It's really, really nice. ;D

Blackprojects

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Re: Rare galaxy types in Hubble Zoo - what to look for, where to post
« Reply #11 on: July 15, 2010, 02:29:25 am »
OK Hubble ZOO has given me a real Weirdo to Play with.

ID: AHZ40001b6
Survey: GEMS and GOODS-S
Survey reference: 90008171
Right ascension: 53.3584° as h:m:s
Right ascension: 3:33:26.02 as decimal
Declination: -27.9006° as d:m:s
Declination: -27:54:2.26 as decimal
Magnitude: 23.2077 ± 0.0059
Magnitude: 23.4997 ± 0.0178
Kron radius: 3.5000
Kron radius: 4.6200
Redshift: 2.629000
Universe age at redshift:
2.528 Billion years

« Last Edit: July 15, 2010, 01:51:29 pm by Blackprojects »

paulrogers

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Re: Rare galaxy types in Hubble Zoo - what to look for, where to post
« Reply #12 on: July 15, 2010, 06:39:19 am »
OK Hubble ZOO has given me a real Weido to Play with.
ID: AHZ40001b6
Redshift: 2.629000
Universe age at redshift:
2.528 Billion years
Dang!  :o :o  Can that redshift be believed?  If that's true, it's so primitive it's probably not classifiable.

Bruno

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Re: Rare galaxy types in Hubble Zoo - what to look for, where to post
« Reply #13 on: July 15, 2010, 07:33:02 pm »

ID: AHZ10002wh
Magnitude: 16.8707 ± 0.0002
Redshift: 0.142600

Any idea where to post this beautiful and exceptional galaxy?  Is this a spiral embedded in stellar or dust cloud?  Is what looks like a golden edge to a spiral galaxy really a dust lane and is it in the surrounding larger object or is it closer to us than that object?
Aegis says it's a post merger see here;)
« Last Edit: July 15, 2010, 07:36:42 pm by Bruno »
Ciao
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SowaZiom

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Re: Rare galaxy types in Hubble Zoo - what to look for, where to post
« Reply #14 on: August 16, 2010, 12:22:18 pm »


http://www.galaxyzoo.org/examine/AHZ10000f7

Any1 know why galaxy have convex nucleus ?