Galaxy Zoo Talk

Emission line help

  • Ariaiyc_goingawayn0w by Ariaiyc_goingawayn0w

    What's going on here? Also in SDSS it has large H-a and O-III emission lines. So AGN?

    Posted

  • Capella05 by Capella05 moderator

    Not necessarily - Hydrogen Alpha is more likely to do with star formation, than an active nuclei.

    Edit: Looking at this galaxy on SkyServer, I will go with star formation. No AGN.

    Posted

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

    As Capella05 said, there is no hint of an AGN in the SDSS spectrum; in fact, the automated pipeline classed the spectrum as "starburst".

    enter image description here

    From only eyeballing the spectrum, many of the features of AGNs are missing; there's no 'rising continuum' towards the blue end (an 'ultraviolet hump' is common in AGNs), the non-forbidden emission lines are narrow (AGN spectra often show H-alpha and H-beta with a broad base), and there are no highly ionized emission lines (these are often found in AGN spectra, due to the intensity of 'hard' radiation, which is not found in star-forming regions).

    Happy hunting! 😄

    Posted

  • Ariaiyc_goingawayn0w by Ariaiyc_goingawayn0w in response to JeanTate's comment.

    Thanks, I'm slowly learning how to read spectrums. I'm not an expert though so I'll just be giving my best guess if I'm really sure. Comments like yours help me learn more. 😄

    Posted

  • KWillett by KWillett scientist, admin, translator

    No worries - these are really good questions. Thanks for asking them (and to Jean for responding).

    Posted