Galaxy Zoo Starburst Talk

QS galaxies with AGN spectrum!

  • zutopian by zutopian

    Here are QS galaxies with #AGN spectrum.: AGS0000019 and AGS000000l

    Are these special cases or were they wrongly selected for the QS sample?

    I cite from the paper by Ivy Wong et al. .:

    "However, apart from two PSGs which exhibit spectral properties of LINERs, we do not observe any spectral signatures of AGN within our PSG sample."

    http://arxiv.org/abs/1111.1785

    Posted

  • JeanTate by JeanTate in response to zutopian's comment.

    In BPT Diagram Results jules presents some BPT diagrams she developed using Tools. There are ~2700 QS objects in the two plots combined, and many clearly fall in the AGN region of the BPT diagram.

    My own QS BPT diagram - developed using the v3 catalog (which contains the various flux_err fields) - has 2196 objects; my 'quality cut' was S/N > 3. Using log([OIII]/Hb) > 0.61/(log([NII]/Ha)-0.47) + 1.191 to select AGN-dominated objects, I found 546 QS galaxies to have AGN-dominated spectra. I have yet to remove any known outliers that survived the various cuts. It may well be possible to repeat this analysis using Tools; however, I've found it to be very cumbersome.

    The two AGN QS objects you found are both broadline AGNs; many of the objects in the 'AGN-dominated' region of the BPT diagram are narrowline AGN, e.g. AGS00001q3. I'm sure many of the AGN-dominated QS objects are broadline AGNs; I found one very quickly: AGS00000li

    The number of AGN in various subsets of the QS objects is, I think, one of the key things we can try to find, in the Quench project; comparing this with the number in corresponding subsets in the QC catalog is - will be - good scientific results. But I think we first need to get a clean QS and a clean QC, and have confidence in the selection process.

    1 And manually processing objects with log([NII]/Ha) > 0.47. I don't recall which curve this is, but it's one of the standard ones used for this purpose (in the local universe)

    Posted

  • zutopian by zutopian

    Thanks for your reply! So there are post-starburst type AGNs.
    I found a related paper.:

    Post-starburst--AGN Connection: Spatially Resolved Spectroscopy of Hdelta-Strong AGNs

    Tomotsugu Goto (JAXA)

    (Submitted on 8 May 2006)

    http://arxiv.org/abs/astro-ph/0605202

    Posted

  • mlpeck by mlpeck

    Wong et al.'s selection criteria effectively excluded AGNs, since they required weak Hα emission (S/N < 4).

    I found one object in common between the Wong et al. sample of 80 and the quench sample: AGS000022s. That was also the only object in QS that met their stated selection criteria. I found no objects in the control sample.

    Here's the DR10 explore page. Notice in the spectrum that Hα was masked but there are other strong emission lines, so it's questionable whether it really belonged in their sample.

    Posted

  • zutopian by zutopian in response to mlpeck's comment.

    Thanks for your reply. I cite your interesting comment and also another comment by you in following topic.:
    http://quenchtalk.galaxyzoo.org/#/boards/BGS0000001/discussions/DGS00001xy?page=1&comment_id=52579da274983225cd00014a

    Posted

  • mlpeck by mlpeck

    I missed one in the quench sample -- AGS00000y2 is also in the Wong catalog.

    And in the control sample AGS0000495 is in Wong's catalog.

    Both of these have rather strong emission lines in their spectra.

    Posted