OIII spectra lines

• by bernoullilemniscate

  Why do some galaxies have strong OIII emission line(s) but some have much weaker or even OIII absorption lines?

  Posted June 4, 2015 8:44 PM

• by Budgieye moderator

  Every galaxy is different.

  After two galaxies collide to form one galaxy, there is much hydrogen gas colliding,, there is star formation, the hydrogen fuses into carbon and oxygen, the stars are short-lived, the stars explode and release hot carbon and oxygen into space, oxygen emits visible light, and we see Oiii peaks.

  If an oxygen cloud cools down, then it creates a dust cloud which can absorb light from an object behind it, thus making absorption lines.

  See

  Spectra Guide for Galaxy Zoo Talk
  http://talk.galaxyzoo.org/#/boards/BGZ0000001/discussions/DGZ0000ulp?page=3

  and

  3.8 Green peas, compact starburst, Blue compact starburst , OIII objects http://talk.galaxyzoo.org/#/boards/BGZ0000001/discussions/DGZ0000wrb?page=3&comment_id=53d8b93a0d43f77bb6000f98

  7.1 Spectral Charts http://talk.galaxyzoo.org/#/boards/BGZ0000001/discussions/DGZ0000wrb?page=7&comment_id=53d8bb480d43f77b9e000fb7

  Posted June 4, 2015 10:50 PM

• by JeanTate in response to bernoullilemniscate's comment.

  One thing, bernoullilemniscate: if you see a spectrum with [OIII] in absorption, that will be an artifact, or noise. Because the transitions which produce the two green [OIII] lines are 'forbidden' (this simply means that the quantum mechanism which 'permits' it takes a long time to work), absorption is not possible.

  Could you please comment on any such [OIII] absorption spectrum the next time you come across one? It would be interesting to look at ... 😃

  Posted June 6, 2015 4:30 AM

• by bernoullilemniscate

  Be happy to

  Posted June 6, 2015 8:31 PM

• by mlpeck

  Jean,

  Below is a zoomed in portion of a spectrum I created by stacking a bunch of spectra of galaxies from the vicinity of the Coma supercluster that lack detectable emission lines. The fairly deep absorption line on the left is Hβ and the one on the right at ~5175Å is a neutral Mg triplet. There's no absorption line at exactly the wavelength of [O III] 5007 but there are lots of weak ones in the general vicinity.

  There's a Lick index defined in Worthey+ (1994) with a central bandpass that includes 5007Å: it's named "Fe5015" and according to the paper includes lines of Fe I, Ni I, and Ti I.

  It's a shame EigenState doesn't participate in GZ Talk. He might be able to give definitive ID's of the absorption line features. Some of the indexes in the Lick system are apparently sensitive to different elements than what was originally assumed.

  

  Posted June 8, 2015 4:02 PM

• by bernoullilemniscate in response to mlpeck's comment.

  This is similar to the one I saw but can't remember which one. It was shallow and somewhat broad I don't recall on the one I saw that I saw I believe that the hydrogen lines were emission lines. I will stay on the look out though

  Posted June 11, 2015 7:51 PM

• by bernoullilemniscate in response to JeanTate's comment.

  AGZ0007WEL Has an odd [OIII] feature at about 5150-5200 angstroms in an overall dip in intensity in that area. Sorry I'm not well versed in spectral analysis so I don't know the correct terminology

  Posted June 11, 2015 9:14 PM

• by Budgieye moderator in response to bernoullilemniscate's comment.

  Can you check that the link is correct for http://talk.galaxyzoo.org/#/subjects/AGZ0007WEL

  It doesn't lead anywhere for me.

  Posted June 12, 2015 3:35 AM

• by ElisabethB moderator in response to Budgieye's comment.

  The last three characters should be lower case. Try this link : http://talk.galaxyzoo.org/#/subjects/AGZ0007wel

  Posted June 12, 2015 8:10 AM

• by Budgieye moderator

  I looked at the spectrum in DR12. If I click on sky flux, I see that our atmosphere has airglow, like faint northern lights, so that would be subtracted from the galaxy's spectrum, making a slight dip there.

  http://dr12.sdss3.org/spectrumDetail?plateid=1328&mjd=52786&fiber=574

  

  http://skyserver.sdss.org/dr8/en/tools/explore/obj.asp?id=1237661418752245956

  Posted June 13, 2015 4:01 AM

• by Budgieye moderator

  Nice image of airglow at 5577Å (and space shuttle putting on the brakes) in Station Crew Views Shuttle Landing. See the green glow above the Earth's horizon.

  http://www.nasa.gov/multimedia/imagegallery/image_feature_2014.html

  

  Some complex explanations for airglow

  http://www.galaxyzooforum.org/index.php?topic=276308.msg541329;topicseen#msg541329

  http://www.galaxyzooforum.org/index.php?topic=276308.msg541308#msg541308 electric quadrupole (E2) transition

  http://www.galaxyzooforum.org/index.php?topic=276308.msg541337#msg541337 OH forest

  Posted June 13, 2015 4:25 AM