Help identifiying active galactic nuclei

• by liometopum

  This big core reminded me to ask:
  Where are some sources here to help us identify active galactic nuclei?

  Posted January 20, 2015 4:42 AM

• by Budgieye moderator

  If there is no spectral chart, AGN are identified by colour. Nearby are green, then "pink" (magenta) , then blue. Look down the hot hydrogen chart in http://talk.galaxyzoo.org/#/boards/BGZ0000007/discussions/DGZ0000ulp?page=2. There are also examples of when the nucleus is masked by starforming.

  If there are spectral charts, AGN have Hα peaks. Slightly active AGN have small peaks, quasars have big, wide Hα peaks.

  I think the green here is an artifact. Other stars and galaxies nearby have green on one side. It is a distant galaxy, and the AGN would be magenta.

  Posted January 20, 2015 6:46 AM

• by JeanTate in response to liometopum's comment.

  In addition to what Budgieye wrote: if you have only an image (SkyServer or otherwise), perhaps the easiest way to tell if there's an AGN is that the nucleus looks 'star-like'. I.e. it looks as if there's a star at the location of the nucleus (the central part of the a galaxy). For ellipticals, this will mean the center looks abruptly bright; for spirals, that the bulge has a bright center.

  Posted January 20, 2015 2:34 PM

• by vrooje admin, scientist

  Yes, it's really hard to tell just by looking at the GZ image if a galaxy has an AGN in it. Sometimes you can guess pretty accurately, but the confirmation is in the spectrum or in other multi-wavelength data (like the X-ray, or a combination of X-ray and infrared).

  It's a shame -- AGN are my primary research topic and I would love to be able to spot them with high accuracy (and know I'd not missed many) just by examining the images!

  Posted January 21, 2015 10:31 AM

• by liometopum

  Is there a link to a page showing examples of AGN? Add to this maybe something we can look for in the spectra, on those rare occasions a spectra exists? Then we can at least offer up some possible objects for her to inspect more closely.
  Would that be of help?

  Posted January 26, 2015 3:37 PM

• by Capella05 moderator

  A few examples here AGN - it is just a glossary so I do not want to expand it futhur. The ones that are confirmed will have a spectra on SkyServer.

  More examples here along with a lot of information about spectra etc...

  AGN Thread on the old forum.
  .

  Posted January 26, 2015 5:38 PM