Shredded (smashed) galaxies: post and discuss them here!

• by JeanTate

  The idea for this thread comes from klmaster's post, and elizabeth's response:

  [klmasters] The issue is there isn't a 1-1 link between DR7 and DR8 - because many galaxies which were shredded in DR7 were not in DR8 (and for all the other reasons automated source finding fails sometimes).

  [elizabeth] Shredded?? why where they shredded? search has been a problem since the start. but shredded. I don't get it. sorry.

  [klmasters] Oh sorry - astronomy term. Shredded means that big galaxies in the initial source finding for SDSS were sometimes split up into 2 or more "sources" (which are actually the same thing). You can see this when sometimes big galaxies are not correctly centred in the images we show in GZ. The new source finding in DR8 didn't completely fix this, but did improve it.

  There's already one such shredded (or as I have called them, smashed) galaxy posted here, in the Objects that do not exist! thread: SDSS J161743.61+322146.1 is shredded into ~20 separate "sources" (photometric objects, each one is at the center of a blue circle)

  

  I have found shredded galaxies are fairly common near very bright stars, for example SDSS J155523.49+093636.6 (this also likely includes an object that does not exist):

  

  And Eos (edge-on spirals)/highly inclined ones seem to suffer more shredding than all other galaxy types, holding size approximately constant (except perhaps some irregulars); for example, SDSS J014630.08-003708.8

  

  One of my 'back burner' projects is to investigate the extent to which different degrees of smashing/shredding (by galaxy type, size, ...) introduces systematic bias into published galaxy class properties; another is to check out how such shredding affects the conclusions in Land+ 2008.

  What shredded galaxies have you found?

  Posted July 15, 2014 11:22 PM

• by JeanTate

  AGZ0001jx2 (SDSS J132436.07+013443.0, the bright blue star-forming region well away from the nucleus) is an Eos example commented on by Sakel just a short while ago (July 15 2014 5:01 PM)*:

  

  *all examples, so far, are from DR8 or later.

  Posted July 15, 2014 11:29 PM

• by JeanTate

  AGZ0005njx (SDSS J014704.23+024136.6, also a blue star-forming region well away from the nucleus) is another example from just a while ago (mgfvvc commented on it, timestamp July 15 2014 4:51 PM):

  

  While this has the appearance of an irregular, I suspect it's a pretty normal face-on late-type disk galaxy, with a modest bulge (Hubble type Sd?). Curiously, there no "source" associated with the (obvious) nucleus:

  

  Posted July 16, 2014 12:04 AM

• by JeanTate

  AGZ0002bgk (SDSS J140454.55+104807.1, again a blue star-forming region well away from the nucleus) was also commented on earlier today (TheEdGallagher, July 17 2014 11:01 AM). Two very shredded disk galaxies:

  

  Posted July 17, 2014 5:11 PM

• by JeanTate in response to JeanTate's comment.

  One of my 'back burner' projects is to investigate the extent to which different degrees of smashing/shredding (by galaxy type, size, ...) introduces systematic bias into published galaxy class properties

  Why might shredding create a systematic bias?

  Perhaps the easiest way to see at least one way how it might is to ask a simple question:

  Have you ever come across a shredded elliptical?

  Posted July 17, 2014 6:24 PM

• by JeanTate

  AGZ0001key (SDSS J215640.20-090447.7) not clear to me why it got shredded, star-forming region (looks like a supernova in the GZ image!)?

  

  

  Posted July 18, 2014 1:15 PM

• by elizabeth_s in response to JeanTate's comment.

  Oh well Jean sorry not scientific at all but (insert rolled eyes) \ http://casjobs.sdss.org/ImgCutoutDR7/getjpeg.aspx?ra=211.22326921&dec=10.80098034&scale=0.39612&width=512&height=512&opt=&query=

  
  http://www.galaxyzooforum.org/index.php?topic=275380.msg332195#msg332195

  Just draw me a sheep

  Posted July 18, 2014 1:53 PM

• by JeanTate

  AGZ0001r7y (SDSS J091747.26+531737.6 - star-forming region, not the nucleus), pretty badly shredded (it's also an #overlap)

  

  Posted July 18, 2014 4:51 PM

• by JeanTate in response to elizabeth's comment.

  Behold, Just draw me a sheep makes its debut, here in Galaxy Zoo Talk! 😄

  Thanks very much, elizabeth!

  Posted July 18, 2014 5:02 PM

• by JeanTate

  AGZ0003yav (SDSS J231923.46+173854.8 - nucleus, for once); it's also an #overlap:

  
  

  Posted July 19, 2014 3:27 AM

• by JeanTate

  AGZ00016lb (SDSS J161139.28+005235.5, centered on the nucleus, for once) is smashed in a curious way: the other object is a faint STAR (SDSS J161139.22+005235.3), slightly offset from the nucleus:

  
  

  Posted July 19, 2014 11:26 PM

• by JeanTate

  AGZ00023r4 (SDSS J004703.14+413019.3) is on the line of sight towards a distant, rich cluster (all those faint red blobs!), so it's an #overlap of a kind no one seems much interested in. It's only mildly smashed:

  

  Posted July 19, 2014 11:34 PM

• by JeanTate

  AGZ0003k5h (SDSS J013106.68+482603.3), the second GALAXY is centered on a bright part of the bar/arm):

  

  Posted July 22, 2014 8:27 AM

• by JeanTate

  AGZ0003s7l (SDSS J150653.99+581324.8), a shredded Eos:

  

  Posted July 22, 2014 8:32 AM

• by JeanTate

  AGZ0004blv (SDSS J044719.23-041204.8):

  
  

  Posted July 26, 2014 8:45 PM

• by JeanTate

  AGZ00050sl (SDSS J012932.09-024100.7):

  

  Posted July 26, 2014 8:48 PM

• by JeanTate

  AGZ0005vrz (SDSS J233800.62+205722.0), only mildly shredded:

  

  Posted July 27, 2014 2:00 AM

• by JeanTate

  AGZ0001jsp (SDSS J141838.12+020246.7) is not centered on the nucleus of this highly inclined spiral, nor is SDSS J141837.48+020244.1. Both have spectra; the former is a STARBURST, the latter STARFORMING.

  

  Posted July 27, 2014 8:59 AM

• by JeanTate

  AGZ0002blt (SDSS J111631.53+071821.3, the nucleus/photocenter), a seriously shredded irregular and #overlap

  

  Posted July 27, 2014 9:03 AM

• by JeanTate

  AGZ0003rtw (SDSS J164608.70+632255.5), nicely illustrating that blue galaxies are more likely to be shredded than red ones.

  

  Posted July 27, 2014 11:31 PM

• by JeanTate

  AGZ00032hz, SDSS J040326.54-110054.3, a shredded Eos with a prominent dustlane.

  

  Posted July 28, 2014 2:54 PM

• by JeanTate

  AGZ0004ad8, SDSS J150751.15-092211.0 is a very beautiful face-on barred sprial with rings. It is also shredded; the outer parts are particularly affected.

  

  Posted July 28, 2014 4:55 PM

• by ChrisMolloy

  Hi Jean,

  Here's AGZ0003f9t. Disturbed, irregular and difinitely looks shredded. NED lists it as VV 730. Also looks to have starforming regions.

  

  

  Posted July 29, 2014 12:26 PM

• by JeanTate in response to ChrisMolloy's comment.

  Hi Chris.

  Yes, that's a good example.

  Once you start looking for shredded SDSS galaxies, you quickly find lots! After a while it's almost that you can tell, at a glance, how likely it is a galaxy will turn out to be shredded ... irregulars with lots of star-forming regions? very likely boring blobby ellipticals? almost never.

  Posted July 30, 2014 2:29 AM

• by JeanTate

  AGZ0002b20, SDSS J170919.60+255631.8, a highly inclined spiral, probably barred:

  

  Posted July 30, 2014 2:35 AM

• by ChrisMolloy

  AGZ00039U0

  Slightly inclined spiral. Very red.

  
  

  Posted August 20, 2014 1:07 PM

• by ChrisMolloy

  AGZ0002883

  #ring, #overlap, #NGC 4377, #UGC 07501, #III Zw 065, #PGC 040477, #MCG +03-32-025,

  
  

  Posted August 20, 2014 1:30 PM

• by ChrisMolloy

  AGZ0002K06

  Shredded. #NGC 5303, #UGC 08725, #ARK 428, #KUG 1345+385A, #CGCG 218-047, #MCG +07-28-067, #PGC 048917, #UZC J134745.0+381817, #FIRST J134745.1+381821, #NVSS J134745+381819, #SN 2003ed.

  
  

  Posted September 14, 2014 10:45 AM