Merger Resources - Links and articles helping us understand Mergers.

[Alice]

 

[echo-lily-mai]

Galaxy Crash Debris: Post-merger Spherodials paper now out! 29 November 2011 Blog posted by Kevin links to arXiv

[zutopian]

Here is a new paper:

"Evolution of magnetic field in interacting galaxies"

Not much is currently known about how galaxy interactions affect an evolution of galactic magnetic fields. Here, for the first time, we explore a global evolution of magnetic fields with the advance of interaction process.

Authors: Robert T. Drzazga, Krzysztof T. Chyzy, Wojciech Jurusik
(Submitted on 19 Jan 2012)
http://arxiv.org/abs/1201.4051

[echo-lily-mai]

Seeing mergers in a different light 2 January 2012 Blog by Alfredo Carpineti

[echo-lily-mai]

The infrared properties of mergers 27 January 2012 Blog by Alfredo Carpineti

"Following the previous post, we continue the analysis of galaxy mergers in the infrared."

[zutopian]

Here is a recent paper, whose authors are skeptical concerning Galaxy Zoo classifications:

2.1.2. Comparison with the Galaxy Zoo Catalog
We cross-correlate our sample of galaxy pairs with the galaxy zoo catalog (Lintott et al. 2011) to compare the two classification schemes. Galaxy Zoo comprises a morphological classification of nearly 900,000 galaxies drawn from the Sloan Digital Sky Survey, contributed by hundreds of thousands of volunteers in order to cover a wide coverage of the galaxy survey, however due to the large number of classifiers it becomes complex to maintain a unified criteria and a reliable classification. They define six categories (elliptical, spiral, spiral clockwise, spiral anticlockwise, merger or uncertain) and give the fraction of votes in each of the six categories. Objects classified as mergers are identified as galaxies with signs of collision. We find 1417 common pairs in the two catalogs, where 596 pairs are classified as disturbed (M or T), while only 128 objects were classified as “merger” by the galaxy zoo team (fraction of votes > 0.5).
We show in Fig. 4 some typical examples of pairs we classified as M and T, while galaxy zoo assigned an extremely low fraction of votes for a “merger” in these objects.

Title: Galaxy interactions I: Major and minor mergers
Authors: Diego G. Lambas, Sol Alonso, Valeria Mesa, Ana Laura O'Mill
(Submitted on 9 Nov 2011)
http://arxiv.org/abs/1111.2291

[zookeeperChris]

I should read this properly, but we pointed out in Darg's papers that a very low percentage of votes in the merger category is still good enough to mark something as a merger. More when I've read it!

Chris

[zutopian]

I should read this properly, but we pointed out in Darg's papers that a very low percentage of votes in the merger category is still good enough to mark something as a merger. More when I've read it!

Chris

Thank you for your reply!
I started a thread "How reliable are our classifications?" due to this paper: http://www.galaxyzooforum.org/index.php?topic=279913.0
So after examing the paper, you might want to post a comment in that thread.

[echo-lily-mai]

Thanks zutopian for all your hard work.    I feel these papers and projects should be included over here. So I am quoting you from another thread

Yes, they compared just merger classifications.
The Merger Checking Project is listed in the "Index of GZ Projects", which was started by you:
http://www.galaxyzooforum.org/index.php?topic=276706.msg397351#msg397351

This completed project can be found here
Galazy Zoo Merger Checking

Links for the completed project can be found here
Merger Hunters needed
Merger Checking Examples

OOTD by Waveney Saturday 6th September 2008 Merger Clues

Here are published GZ papers about mergers:
Darg D., et al., 2009, "Galaxy Zoo: the fraction of merging galaxies in the SDSS and their morphologies"
http://arxiv.org/abs/0903.4937
Darg D., et al., 2009, "Galaxy Zoo: The properties of merging galaxies in the nearby Universe - local environments, colours, masses, star-formation rates and AGN activity"
http://arxiv.org/abs/0903.5057
Darg D. W., et al., 2010, "Galaxy Zoo: Multi-Mergers and the Millennium Simulation"
http://arxiv.org/abs/1012.4214

Link  to Merger Simulations - Beta thread
Sneak Preview of Galaxy Zoo project

[echo-lily-mai]

"Star-formation, AGN and Ultra-luminous infrared galaxies" 17 February 2012 blog by Kevin

[echo-lily-mai]

Blog by Bill Keel
  Hubble results on Hanny’s Voorwerp – the whole story

3 – As we could sort of see from the SDSS images, IC 2497 is disturbed. Its spiral arms are twisted out of a flat plane, with dust lanes cutting in front of the central region. This fits with the idea that a tidal collision pulled out the massive tail of neutral hydrogen. On the other hand, we now see that the companion galaxy just to its east is a beautifully symmetric, undisturbed spiral (which we now know to have a precisely matching redshift, so they are almost certainly close together). One picture that would fit these data would be that IC 2497 is the product of a merger something like a billion years ago (more precisely, before the time when we see it), a merger which was either quite unequal in galaxy masses or unusual in leaving the disk of the galaxy in place although warped. There is a suggestion that the patch of star-forming areas just to the southwest of the center of IC 2497 might be all that remains of the other galaxy./quote]

[echo-lily-mai]

NEW SCIENTIST article Astrophile: Square galaxy is a rebel
"Another option is that the angular galaxy formed out of the collision of two spiral galaxies. The impact threw the pre-existing stars from these galaxies into large orbits, creating the rectangular outline, while the gas sank to the middle and condensed to form the central disc of new stars."

[c_cld]

I read today the blog "The Finale of Merger Zoo; 27 March 2012 by John" and I've taken a look at the 54 thumbnails.
I don't understand if it is only a "zooites" sample or the base of more detailed study by the team.

I have some doubts on few pairs which can't be interacting at hundreds of megaparsecs apart, and i suggest to carefully estimate the distance between the two (or three) nuclei of the pair in interaction.
example
Pair
objid_in_pair                ra          dec                  z            neighbor_in _pair          n_ra              n_dec     n_z      sep (arcmin)  dist Mpc
588017604696408195 221.32866 38.805889 0.059753 588017604696408114 221.34691 38.781006 0.032244 1.72 203.2 


IMHO More suitable and convenient pairs with redshift data from spectra:
objid_in_pair                   ra               dec               z              neighbor_in _pair          n_ra           n_dec           n_z         sep (arcmin)  comovdist Mpc
587735043609329845  122.8062  25.206872  0.013642  587735043609329848  122.81634  25.179368  0.013866  1.740  -1.74
587738569249390718  206.21242  13.927611  0.081822  587738569249390719  206.20992  13.921739  0.082454  0.381  -4.44
587739707420967061  241.38801  17.601432  0.034178  587739707420967062  241.39105  17.593703  0.034001  0.495  1.33
587724234257137777  30.957469  14.739165  0.012120  587724234257137746  30.935845  14.709317  0.012180  2.187  -0.46
587727178988388365  4.7095721  -10.361805  0.026916  587727178988388359  4.7119958  -10.376863  0.027139  0.915  -1.70
587728676861051075  203.04336  62.767772  0.009662  587728676861050946  203.02879  62.700674  0.009803  4.046  -1.10
587739721900163101  191.54212  30.731914  0.022177  587739721900163099  191.54685  30.722743  0.021776  0.602  3.06
587739810496708646  236.72219  17.872677  0.011338  587739828210958448  236.74535  17.884185  0.010971  1.492  2.85
587741532784361479  167.80421  28.711897  0.029366  587741532784361477  167.80497  28.696415  0.028480  0.930  6.71
587741534400217110  181.43954  31.0588  0.023144  587741534400217109  181.43986  31.079166  0.023365  1.222  -1.69
587741722819493915  183.89938  28.177643  0.021930  587741722819493916  183.90551  28.169634  0.022311  0.580  -2.91
588013383816904792  181.16478  52.957307  0.080801  588013383816904793  181.15823  52.954774  0.081546  0.281  -5.24
588017978901528612  209.65826  37.424476  0.011636  588017978901528618  209.64213  37.452737  0.011547  1.862  0.69
588018055130710322  255.02867  23.131512  0.056831  588018055130710321  255.02923  23.12753  0.056812  0.241  0.14

 

[zutopian]

I read today the blog "The Finale of Merger Zoo; 27 March 2012 by John" and I've taken a look at the 54 thumbnails.
I don't understand if it is only a "zooites" sample or the base of more detailed study by the team.

I have some doubts on few pairs which can't be interacting at hundreds of megaparsecs apart, and i suggest to carefully estimate the distance between the two (or three) nuclei of the pair in interaction.
example
Pair
objid_in_pair                ra          dec                  z            neighbor_in _pair          n_ra              n_dec     n_z      sep (arcmin)  dist Mpc
588017604696408195 221.32866 38.805889 0.059753 588017604696408114 221.34691 38.781006 0.032244 1.72 203.2 

(...)

588017604696408195 is NGC 5753 (and the other one is NGC 5755)!
You missed, that in NED there is given a different redshift than in SDSS and an essential note: "SDSS has z = 0.059750 +- 0.000167" !
NED cites z=0.032099.  (It has nearly same redshift as the other galaxy and thus they might interact.)
So the redshift or spectrum in SDSS (DR7/DR8) seems to be wrong! (I have no clue, why the redshift in SDSS is different than in NED!) 
On the other hand, I wonder, if the disturbance of NGC 5755 is really caused by NGC 5753 or if NGC 5755 is actually itsself a GPair (at the spectrum target in SDSS there seems to be another galaxy: 588017604696408114).
Simbad says:
NGC 5753 -- Galaxy in Pair of Galaxies
NGC 5755 -- Interacting Galaxies

 

[echo-lily-mai]

I'm sure anyone who liked the Mergers Project will like this!! Mini mergers. Simulation: A Disk Galaxy Forms APOD video.

"Explanation: How do galaxies like our Milky Way form? Since our universe moves too slowly to watch, faster-moving computer simulations are created to help find out. Green depicts (mostly) hydrogen gas in the above movie, while time is shown in billions of years since the Big Bang on the lower right. Pervasive dark matter is present but not shown. As the simulation begins, ambient gas falls into and accumulates in regions of relatively high gravity. Soon numerous proto-galaxies form, spin, and begin to merge. After about four billion years, a well-defined center materializes that dominates a region about 100,000 light-years across and starts looking like a modern disk galaxy. After a few billion more years, however, this early galaxy collides with another, all while streams of gas from other mergers rain down on this strange and fascinating cosmic dance. As the simulation reaches half the current age of the universe, a single larger disk develops. Even so, gas blobs -- some representing small satellite galaxies -- fall into and become absorbed by the rotating galaxy as the present epoch is reached and the movie ends. For our Milky Way Galaxy, however, big mergers may not be over -- recent evidence indicates that our large spiral disk Galaxy will collide and coalesce with the slightly larger Andromeda spiral disk galaxy in the next few billion years."