Author Topic: Ringed and Pseudoringed Galaxies  (Read 89792 times)

EricFDiaz

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Ringed and Pseudoringed Galaxies
« on: April 02, 2008, 02:34:56 pm »
The Kinematics and Dynamics of Galactic Rings

The Physics of Resonance

The physics involved in resonance entails the differential rotation of a galaxy's bar with respect to particles in the the disk of the galaxy. Put simply, it is the value of the bar pattern angular velocity in relation to the angular frequency of circular rotation and the radial epicyclic frequency of every star and dust cloud in the disk of the galaxy. The epicycles are actually closed elliptical orbits of material in the disk of the galaxy that are precessing around the central region of the galaxy. How fast a bar pattern rotates determines what kind of resonance you end up with in a galaxy. If the bar pattern speed is fast enough then it is believed that it can push a spiral out to the Outer Lindblad Resonance (OLR). If OLR is in the visible disk then it may lead to ring and pseudoring formation. The three major resonances relevant to ring formation are:

Outer Lindblad Resonance (OLR)
Inner Lindblad Resonance (ILR)
Inner 4:1 Ultraharmonic Resonance (UHR)



Figure 1. The OLR subclass of outer pseudorings

Figure. 2. Schematic showing the relative shapes, sizes, and major-axis orientations of all of the bar and ring features of NGC 3081, including the "dimples" in the outer R1 ring feature. Here "nr" refers to the nuclear ring, and "nb" to the nuclear (secondary) bar. Axes are labeled in arcsecond offsets relative to the nucleus. North is at the top, and east is to the left.

Image and description source: A HUBBLE SPACE TELESCOPE STUDY OF STAR FORMATION IN THE INNER RESONANCE RING OF NGC 3081 by R. Buta et al.


Other important types of resonance are corotation (CR) and the outer 4:1 resonance. In corotation (CR) the periodic rate of rotation of the bar is equal to the angular frequency of circular rotation of the disk. In the outer 4:1 resonance the periodic rate of rotation of the bar is equal to the angular frequency of circular rotation plus 1/4 of the radial epicyclic frequency.

Figure 3. Corotation resonace (CR)

If you read nothing else on this subject, at the very least, read Galactic Rings by R. Buta and F. Combes. I consider this a must-read. (very highly recommended)

Another paper worth reading is the following:

Title: The Morphology of Barred Galaxies
Authors: Buta, R.
Journal: Barred galaxies. Astronomical Society of the Pacific Conference Series, Volume 91; Proceedings of a conference held at the University of Alabama; Tuscaloosa; Alabama; 30 May - 3 June 1995; San Francisco: Astronomical Society of the Pacific (ASP #91); |c1996; edited by R. Buta, D. A. Crocker and B. G. Elmegreen, p.11
Bibliographic Code: 1996ASPC...91...11B

TABLE I. Summary of notation for ring and lens phenomena (below) from the paper (above), Galactic Rings by R. Buta and F. Combes.

TABLE I. Summary of notation for ring and lens phenomena
Feature symbol
nrnuclear ring
nr'nuclear pseudoring
rinner ring
rsinner pseudoring
Router ring
R'outer pseudoring
R1Type 1 OLR subclass outer ring
R1'Type 1 OLR subclass outer pseudoring
R2'Type 2 OLR subclass outer pseudoring
nlnuclear lens
linner lens
rlinner ring/lens
Louter lens
RLouter ring/lens

Here's a wonderful paper written by Dr. Ronald Buta et al on a study done with the Hubble Space Telescope of the inner resonance ring of NGC 3081. Even though the paper's focus is on this one galaxy, it gives the reader a much more in-depth understanding of the kinematics and dynamics of inner rings in general. Admittedly, it's a little technical, but well worth reading. A HUBBLE SPACE TELESCOPE STUDY OF STAR FORMATION IN THE INNER RESONANCE RING OF NGC 3081.

The Origins of Spiral Arms

Hydrodynamic Modeling

How Two, Three and Four Arms Are Created
by a Single Galactic Bar

The Origins of Spiral Arms - translated by Charles Danforth, University of Colorado

Figure 1. By aligning a series of concentric elliptical (2/1) orbits, a bar can be produced (a). If each ellipse is given an azimuthal offset proportional to r½, the effect is a two armed spiral of orbits (b). A set of (3/2) orbits produces a three armed spiral (c) and (4/1) produces a four armed pattern (d).

The above illustration is from The Origins of Spiral Arms by Charles Danforth, University of Colorado.

Star-Forming Nuclear Rings in Spiral Galaxies

Here's a paper entitled Star-Forming Nuclear Rings in Spiral Galaxies.pdf

Examples of the Application of the Notation for Ring
and Lens Types to Actual Images of Galaxies


I realize that this is a lot to swallow all at once. So, I have provided a couple of examples of objects, each with a very sophisticated classification using feature symbols from Table I. There is a summary of notation for ring and lens phenomena below. But, I have also included "alternative" classifications from both NED and SIMBAD, which are considerably simpler, to give you a better idea of what you may come across in Galaxy Analysis. Thank you for reading. :)

Eric

NGC 3081
RA=9:59.5, Dec=-22:50

Classifications: (R1R2')SAB(r,nr)0/a   

Alternative Classifications

SIMBAD
Basic data: Seyfert 1 Galaxy*
Morphological type   S0:r

NED
Classifications: (R_1)SAB(r)0/a Sy2*

*SIMBAD and NED seem to be in disagreement on whether this is a Seyfert 1 or a Seyfert 2 galaxy.




NGC 2273
RA = 6:50.1, Dec. = +60:51

Classifications: (RR)SB(rs)a  Sy2

Alternative Classifications

SIMBAD
Basic data: Seyfert 2 Galaxy
Morphological type  SBa

NED
Classifications: SB(r)a:        Sy2


The thumbnails (below) are more examples of ring and pseudoring classifications.
« Last Edit: July 23, 2008, 04:05:28 pm by EricFDiaz »

Half65

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Re: Barred Outer "Ringed" Galaxies and Pseudoring
« Reply #1 on: April 02, 2008, 07:52:48 pm »
Thanks for link. I need time to read and many many (infinity many) to understand.  :D

EricFDiaz

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Re: The Outer, Inner and Nuclear Ring and Pseudoring Phenomena
« Reply #2 on: April 03, 2008, 01:05:10 am »
I thought some examples might help better than words to illustrate the morphology of pseudorings. This first example is of a Type 1 OLR subclass outer pseudoring. This image was posted in the "ring galaxy" thread by christopherk on March 21, 2008. I am combing through the ring galaxy thread looking for more examples of outer ring pseudorings. I will post them here as I come across them, both Type 1 and Type 2 OLR subclass outer pseudorings.

Classifications: (R1')SA(r)ab
« Last Edit: July 09, 2008, 05:21:34 am by EricFDiaz »

EricFDiaz

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Re: The Outer, Inner and Nuclear Ring and Pseudoring Phenomena
« Reply #3 on: April 03, 2008, 01:25:47 am »
This one was posted in Ring Galaxy thread by rem1 on March 24, 2008. Rem1 refers to it in the post as an "Eight-like ring galaxy". The figure-eight is a characteristic feature of Type 1 OLR subclass outer pseudorings.

Classifications: (R1')SA(r)ab
« Last Edit: July 09, 2008, 05:26:04 am by EricFDiaz »

Half65

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Re: Outer Ring (Pseudoring) in Spiral Galaxies
« Reply #4 on: April 03, 2008, 08:22:14 am »
This is NGC 4725 that is cited in the Early Observation paragraph.


http://cas.sdss.org/astro/en/tools/explore/obj.asp?ra=192.61083&dec=25.50083

EricFDiaz

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Re: The Outer, Inner and Nuclear Ring and Pseudoring Phenomena
« Reply #5 on: April 03, 2008, 03:52:30 pm »
This is NGC 4725 that is cited in the Early Observation paragraph.
http://cas.sdss.org/astro/en/tools/explore/obj.asp?ra=192.61083&dec=25.50083

Thanks for posting this, Half65!. I remember reading about NGC 4725 on page 11 of the paper. I suspect that it may be, in fact, a one-armed galaxy. But, I'm not really certain of that.

Classifications: SAB(r)ab pec   Sy2
« Last Edit: July 09, 2008, 05:39:38 am by EricFDiaz »

EricFDiaz

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Re: The Outer, Inner and Nuclear Ring and Pseudoring Phenomena
« Reply #6 on: April 03, 2008, 04:23:37 pm »
Posted by Gruntfutuck in the Ring Galaxy thread on July 26, 2007. Gruntfutuck wrote in the post, "Probably *just* a spiral, but so nearly a ring...". This is what is known as a leading arm ringed galaxy.
« Last Edit: July 08, 2008, 04:35:08 am by EricFDiaz »

EricFDiaz

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Re: The Outer, Inner and Nuclear Ring and Pseudoring Phenomena
« Reply #7 on: April 03, 2008, 05:35:40 pm »
This is a Type 1 OLR subclass outer pseudoring.

Classification: (R1')SB(r)ab
« Last Edit: July 09, 2008, 05:13:03 am by EricFDiaz »

EricFDiaz

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Re: The Outer, Inner and Nuclear Ring and Pseudoring Phenomena
« Reply #8 on: April 04, 2008, 03:24:22 am »
Note: Going through some of my postings, I noticed that I had made a few errors in classifications of the galaxies. I have since corrected all of the errors.

Originally, I only intended to post a few examples as visual aids to help GZ members better understand the articles that I had posted. I never intended this thread to develop into what it is becoming. Therefore, since I am posting SDSS images, from now on I will be including the reference numbers of each galaxy. Even though the images were posted before by other people, I don't feel it's duplication simply because all of the objects were classified incorrectly and consequently put in the wrong thread. I hope this is OK with the zookeepers. If not, then please let me know. Thank you. :)

Eric

P.S.

Just a reminder but for those interested in this topic and who have been following this thread....I would just like to let you know that I have posted more information and links in the second post at the beginning of this thread. I will continue to post more information and/or links in the second post as I find it.
« Last Edit: April 04, 2008, 05:58:10 am by EricFDiaz »

Half65

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Re: The Outer, Inner and Nuclear Ring and Pseudoring Phenomena
« Reply #9 on: April 04, 2008, 05:27:52 am »
Thanks Eric.
I'm reading the paper and the examples that you submitted are very useful.

elizabeth

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Re: The Outer, Inner and Nuclear Ring and Pseudoring Phenomena
« Reply #10 on: April 04, 2008, 07:11:45 pm »
 :) very interesting I have read it through about 4 x's now it may be sinking in. Thanks for posting the info. ;D

EricFDiaz

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Re: The Outer, Inner and Nuclear Ring and Pseudoring Phenomena
« Reply #11 on: April 04, 2008, 07:21:18 pm »
:) very interesting I have read it through about 4 x's now it may be sinking in. Thanks for posting the info. ;D

Great, Liz!!! :) Yeah, it's taking me a little while to get a handle on it too. ;D ;D :D ;)

waveney

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Re: The Outer, Inner and Nuclear Ring and Pseudoring Phenomena
« Reply #12 on: April 04, 2008, 08:58:11 pm »
I had been noticing a few galaxies that have these properties and was just going to post about them when you started this thread. 

What strikes me about many of the R'1 galaxies is that they are in effect two symmetrical circles with the bar filling the intersection between them, further in several of them the centers of the circles often seem to be at the edge of the central bar. 

Anyway here is one that I found earlier:



http://cas.sdss.org/astro/en/tools/explore/obj.asp?id=587742062152056888
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EricFDiaz

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Re: The Outer, Inner and Nuclear Ring and Pseudoring Phenomena
« Reply #13 on: April 04, 2008, 10:24:24 pm »
I had been noticing a few galaxies that have these properties and was just going to post about them when you started this thread. 

What strikes me about many of the R'1 galaxies is that they are in effect two symmetrical circles with the bar filling the intersection between them, further in several of them the centers of the circles often seem to be at the edge of the central bar.   

http://cas.sdss.org/astro/en/tools/explore/obj.asp?id=587742062152056888

That typically is the case, waveney. There are some galaxy evolution researchers who believe that all spirals start out as barred and that the initial spiral arms that form, start forming at the ends of the bar. They contend that over time as more material accumulates, the original bar sometimes gets lost or hidden in an ever growing central bulge, thus creating regular (i.e. unbarred) spirals. Whether or not this is true, remains to be seen.

It seems that with the R'1 galaxies, whether they be barred, weakly barred (i.e. more oval) or regular spirals, the density waves which create the spirals arms of these galaxies coincide with a resonance radius in such a way that they produce these two symmetrical outer ring pseudorings on either side of the bar or central region, thus forming the figure-eight pattern characteristic of R'1 galaxies.

Anyway, thanks for uploading the great image of what to me looks like an (R'1)SABa galaxy. ;)
« Last Edit: April 04, 2008, 11:04:49 pm by EricFDiaz »

diaswa

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Re: The Outer, Inner and Nuclear Ring and Pseudoring Phenomena
« Reply #14 on: April 04, 2008, 11:14:49 pm »
Note: Going through some of my postings, I noticed that I had made a few errors in classifications of the galaxies. I have since corrected all of the errors.

Originally, I only intended to post a few examples as visual aids to help GZ members better understand the articles that I had posted. I never intended this thread to develop into what it is becoming. Therefore, since I am posting SDSS images, from now on I will be including the reference numbers of each galaxy. Even though the images were posted before by other people, I don't feel it's duplication simply because all of the objects were classified incorrectly and consequently put in the wrong thread. I hope this is OK with the zookeepers. If not, then please let me know. Thank you. :)

Eric

P.S.

Just a reminder but for those interested in this topic and who have been following this thread....I would just like to let you know that I have posted more information and links in the second post at the beginning of this thread. I will continue to post more information and/or links in the second post as I find it.

Hmmm !  This is very interesting turn of a thread.

So, if this topic is the place to put all "ringed" galaxy posts instead of putting them in "The Ring Galaxy" thread, how to we cleanse that thread of the "ringed" posts ?

I could move my "ringed" galaxy posts, since I have been keeping track of them in my off-line log sheets, but for other posts ?

Also, should the "Ring Galaxy" thread, this new thread, and possibly the "Possible Polar Ring Galaxy" thread be moved to one location in the Zoo, just for ease of finding things about rings ?

regards,  diaswa
« Last Edit: April 04, 2008, 11:18:18 pm by diaswa »