Galaxy Zoo Starburst Talk

Spectrum, which doesn't look like post-starburst! QS galaxy

  • zutopian by zutopian

    I am not familiar with spectra, but I think, that the spectrum of following QS galaxy doesn't look like "post-starburst".: AGS0000021
    It looks to me like a normal starburst spectrum. Was it wrongly selected?
    If not, what did qualify it for being selected? What does it make a post-starburst spectrum?

    Posted

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

    It's in the "SFR" (star-forming region) part of the BPT diagram, and all the H Balmer lines are emission (at least to H-epsilon1). However, the model spectrum differs considerably from the 'observed' one, especially in that the model is waaay lower (in peak flux) than the observed emission lines; it is even ~zero for some quite prominent (observed) emission lines (e.g. the [OIII] line red-ward of H-gamma).

    1 strangely, this is at a significantly different redshift than the other H-Balmer lines

    Posted

  • mlpeck by mlpeck

    30% of the quench sample objects are, spectroscopically, starforming. I examined the statistics of the starforming subset in some detail here. The percentage of starforming objects is virtually the same in the quench and control 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

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

    Thanks for your reply. I guess, that it means, that the spectrum however doesn't fit?
    I wonder, if your comment also applies to the spectra of the other 30% QS starforming galaxies?
    I am going to mention your comment in the Sample Selection topic.:
    http://quenchtalk.galaxyzoo.org/#/boards/BGS0000001/discussions/DGS00001xy?page=3&comment_id=525c7d7f72c10941fb0007e1

    Posted

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

    I guess, that it means, that the spectrum however doesn't fit?

    I don't know, and I wish I did. I do not yet understand what - exactly - the model spectrum (red line) is (well, I've read the Redshifts, Classifications and Velocity Dispersions page, but I don't understand how the H-Balmer line fitting is done, nor how the flux estimates are derived).

    I wonder, if your comment also applies to the spectra of the other 30% QS starforming galaxies?

    I'm sure it does to at least some. In my experience, a single object, selected at random from a set defined in some fairly consistent way, is rarely unique.

    Posted

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

    Thanks for you reply. I copied it to the Sample Selection topic.

    Posted

  • zutopian by zutopian

    What is the starformation rate of this galaxy? Where can find this information? In Tools or in SDSS?

    Posted

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

    If you're still referring to AGS0000021, the star-formation rate is 0.0509801. I do not know what the units are, perhaps sols per year (1 sol = the mass of the Sun). The information is in the field "sfr" in the QS v4 catalog, and can be found using Tools. This field was introduced by ltrouille in a GZ blog post, Quench Boost: A How-To-Guide, Part 3 ("luminosity distances" is also a link, but I didn't copy that):

    We’ve uploaded a few additional properties for all the galaxies (e.g., luminosity distances and star formation rates).

    The link, in the quote, takes you to an MPA (Max Planck Institute for Astrophysics) webpage, with an explanation of how the SFRs were determined.

    Posted

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

    Thanks for your reply. When clicking "Open in Tools" in Talk, there is no sfr value given. I wonder, why it is missing? Could they please add.

    Posted

  • zutopian by zutopian

    I found something new in DR10: In the left/blue toolbar there is given following.:

    Fit Parameters
    sppParams
    StarformingPort
    PassivePort
    emissionLinesPort
    PCAWiscBC03
    PCAWiscM11
    FSPSGranEarlyDust
    FSPSGranEarlyNoDust
    FSPSGranWideDust
    FSPSGranWideNoDust

    I clicked StarformingPort : Curiously, there is given SFR=0 for that galaxy.:
    http://skyserver.sdss3.org/dr10/en/tools/explore/summary.aspx?id=0x112d02f422420075&spec=0x04a403467f006800&apid=

    Posted

  • zutopian by zutopian

    Below paper is from 2003 and was cited in 191 papers. One of the authors is Goto.:

    Star formation rate indicators in the Sloan Digital Sky Survey
    A. M. Hopkins (1), C. J. Miller (2), R. C. Nichol (2), A. J. Connolly (1), M. Bernardi (1,2), P. L. Gomez (2), T. Goto (3), C. A. Tremonti (4), J. Brinkmann (5), Z. Ivezic (6), D. Q. Lamb (7) ((1) U.Pittsburgh, (2) CMU, (3) U.Tokyo, (4) JHU, (5) Apache Point Observatory, (6) U.Princeton, (7) U.Chicago)
    (Submitted on 30 Jun 2003 (v1), last revised 5 Sep 2003 (this version, v2))
    http://arxiv.org/abs/astro-ph/0306621

    Posted