Intrinsic shape of star-forming BzK galaxies at z ∼ 2 in goods-N

Suraphong Yuma, Kouji Ohta, Kiyoto Yabe, Masaru Kajisawa, Takashi Ichikawa

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


We study the structure of star-forming galaxies at z ∼ 2 in a Great Observatories Origins Deep Survey North field selected as star-forming BzK (sBzK) galaxies down to KAB < 24.0 mag. Among 1029 sBzK galaxies, 551 galaxies (54%) show a single component in the Advanced Camera for Survey (ACS)/F850LP image obtained with the Hubble Space Telescope; the rest show multiple components. We fit the single-component sBzK galaxies with the single Sérsic profile using the ACS/F850LP image and find that a majority of them (64%) show a Sérsic index of n = 0.5-2.5, indicating that they have a disk-like structure. The resulting effective radii typically range from 1.0 to 3.0 kpc in the rest-frame UV wavelength. After correcting the effective radii to those in the rest-frame optical wavelength, we find that the single-component sBzK galaxies are located in the region where the local and z 1 disk galaxies are distributed in the stellar-mass-size diagram, suggesting comparable surface stellar-mass density between the sBzK and z 0-1 disk galaxies. All these properties suggest that the single-component sBzK galaxies are progenitors of the present-day disk galaxies. However, by studying their intrinsic shape through comparison between the observed distribution of apparent axial ratios and the distribution for triaxial models with axes A > B > C, we find that the mean B/A ratio is 0.61+0.05-0.08 and disk thickness C/A is 0.28+0.03-0.04. This indicates that the single-component sBzK galaxies at z ∼ 2 have a bar-like or oval shape rather than a round disk shape. The shape seems to resemble a bar/oval structure that forms through bar instability; if this is the case, the intrinsic shape may give us a clue to understand dynamical evolution of baryonic matter in a dark matter halo.

Original languageEnglish
Article number92
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 2011 Aug 1


  • galaxies: evolution
  • galaxies: formation
  • galaxies: high-redshift
  • galaxies: structure

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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