The size distribution of galaxies in the Sloan Digital Sky Survey

Shiyin Shen, H. J. Mo, Simon D.M. White, Michael R. Blanton, Guinevere Kauffmann, Wolfgang Voges, J. Brinkmann, Istvan Csabai

    Research output: Contribution to journalArticlepeer-review


    We use a complete sample of about 140000 galaxies from the Sloan Digital Sky Survey (SDSS) to study the size distribution of galaxies and its dependence on their luminosity, stellar mass and morphological type. The large SDSS data base provides statistics of unprecedented accuracy. For each type of galaxy, the size distribution at given luminosity (or stellar mass) is well described by a log-normal function, characterized by its median R̄ and dispersion σln R. For late-type galaxies, there is a characteristic luminosity at Mr,0 ∼ -20.5 (assuming h = 0.7) corresponding to a stellar mass M0 ∼ 1010.6 M⊙. Galaxies more massive than M0 have R̄ M0.4 and σln R ∼ 0.3, while less massive galaxies have R̄ M0.15 and σln R ∼ 0.5. For early-type galaxies, the R̄-M relation is significantly steeper, R̄ M0.55, but the σln R- M relation is similar to that of bright late-type galaxies. Faint red galaxies have sizes quite independent of their luminosities. We use simple theoretical models to interpret these results. The observed R̄-M relation for late-type galaxies can be explained if the fraction of baryons that form stars is as predicted by the standard feedback model. Fitting the observed σln R-M relation requires in addition that the bulge/disc mass ratio be larger in haloes of lower angular momentum and that the bulge material transfers part of its angular momentum to the disc. This can be achieved if bulge formation occurs so as to maintain a marginally stable disc. For early-type galaxies, the observed σln R-M relation is inconsistent with formation through single major mergers of present-day discs. It is consistent with formation through repeated mergers, if the progenitors have properties similar to those of faint ellipticals or Lyman break galaxies and merge from relatively strongly bound orbits.

    Original languageEnglish (US)
    Pages (from-to)978-994
    Number of pages17
    JournalMonthly Notices of the Royal Astronomical Society
    Issue number3
    StatePublished - Aug 11 2003


    • Galaxies: formation
    • Galaxies: fundamental parameters
    • Galaxies: statistics
    • Galaxies: structure

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science


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