Radio Galaxy Zoo Talk

Host of DL in ARG0000xc2 has z 4.45 (per NED), a record in RGZ?

  • JeanTate by JeanTate

    #doublelobe in ARG0000xc2 seems to have STAR host SDSS J124215.94+440719.3, which NED gives a z PHOT of 4.445 (source Richards+(2009)).

    If confirmed by spectroscopy, would that be the record highest redshift for an identified host of an RGZ FIRST source?

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  • 42jkb by 42jkb scientist, admin

    Yes this is a pretty high redshift. However, photometirc redshifts are only reliable out to z=1.0 based on the current templates. This is a science goal of the EMU survey, a way to reliably obtain photometric redshifts for the vast majority of radio sources. There has been some discussion on statistical redshift because once you reach the high redshifts a precise value is not really require for the majority of science.

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  • JeanTate by JeanTate in response to 42jkb's comment.

    There are many sources of z_ph. Aside from SDSS' own*, the sources of z_ph which NED reports are many (some given to impossibly high precision). It would be interesting to understand where the unreliability comes from, for z > ~1.

    This is a science goal of the EMU survey, a way to reliably obtain photometric redshifts for the vast majority of radio sources.

    Cool! 😃 How do they plan to do that?

    *which is actually several, depending on which release you use

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  • 42jkb by 42jkb scientist, admin in response to JeanTate's comment.

    In order to accurately measure a photometric redshift out past z=1, my understanding is the radio AGN templates are required. Having multiple radio observations at different frequencies can provide the spectral energy distribution (SED) for the galaxy type at these higher redshifts. The current issue right now is that many sources aren't covered at enough wavelengths to have a well represented SED. This is where EMU will be beneficial along with MWA, LOFAR MeerKAT, etc.

    On statistical redshifts, both Ray and Minnie gave a talk about this and I'm not sure how far this has gotten yet. May be a good reference to start with.

    http://physics.mq.edu.au/astronomy/workshop_2012/Talks/Mao_TAIPAN.pdf

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