INTRINSIC SHAPE OF STAR-FORMING BzK GALAXIES AT z {approx} 2 IN GOODS-N

Journal Article · Mon Aug 01 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/736/2/92· OSTI ID:21578274

Yuma, Suraphong; Ohta, Kouji; Yabe, Kiyoto ^[1]; Kajisawa, Masaru ^[2]; Ichikawa, Takashi ^[3]

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1. Department of Astronomy, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan)
2. Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho, Matsuyama, 790-8577 (Japan)
3. Astronomical Institute, Tohoku University, Aoba, Sendai 980-8578 (Japan)

We study the structure of star-forming galaxies at z {approx} 2 in a Great Observatories Origins Deep Survey North field selected as star-forming BzK (sBzK) galaxies down to K{sub AB} < 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 Sersic profile using the ACS/F850LP image and find that a majority of them (64%) show a Sersic 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 {approx} 1 disk galaxies are distributed in the stellar-mass-size diagram, suggesting comparable surface stellar-mass density between the sBzK and z {approx} 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{sup +0.05}{sub -0.08} and disk thickness C/A is 0.28{sup +0.03}{sub -0.04}. This indicates that the single-component sBzK galaxies at z {approx} 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.

• OSTI ID: 21578274
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 736; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
EVOLUTION
GALACTIC EVOLUTION
GALAXIES
SHAPE
STARS