Galaxy Zoo Talk

Weirdest spectra (continued from GZ , enhanced by DR12 boss spectra)

  • c_cld by c_cld

    1237654654177968134

    1237654654177968134

    broad Hα and Hβ offset from narrow 8457848449709832192

    Posted

  • c_cld by c_cld

    1237665430243704865

    1237665430243704865

    interactive spectrum 2390407336775673856

    Supermassive Black Hole Binary candidate: see http://arxiv.org/abs/1306.4987

    Posted

  • c_cld by c_cld

    1237657242437288154

    1237657242437288154

    boss spectrum 8199050073725399040

    lots of peaks of emission lines unlabeled? or bad mapping lines (Mg instead of OIII )?

    Posted

  • zutopian by zutopian

    New paper:

    The weirdest SDSS galaxies: results from an outlier detection algorithm
    Dalya Baron, Dovi Poznanski

    How can we discover objects we did not know existed within the large datasets that now abound in astronomy? We present an outlier detection algorithm that we developed, based on an unsupervised Random Forest. We test the algorithm on more than two million galaxy spectra from the Sloan Digital Sky Survey and examine the 400 galaxies with the highest outlier score. We find objects which have extreme emission line ratios and abnormally strong absorption lines, objects with unusual continua, including extremely reddened galaxies. We find galaxy-galaxy gravitational lenses, double-peaked emission line galaxies, and close galaxy pairs. We find galaxies with high ionisation lines, galaxies which host supernovae, and galaxies with unusual gas kinematics. Only a fraction of the outliers we find were reported by previous studies that used specific and tailored algorithms to find a single class of unusual objects. Our algorithm is general and detects all of these classes, and many more, regardless of what makes them peculiar. It can be executed on imaging, time-series, and other spectroscopic data, operates well with thousands of features, is not sensitive to missing values, and is easily parallelisable.

    Comments: MNRAS accepted. Weirdness score for all SDSS galaxies at this http URL and code available at at this https URL

    (Submitted on 22 Nov 2016)

    https://arxiv.org/abs/1611.07526

    Posted