Poster Presentation
ALMA 370-pc Resolution Imaging of z~3.2 Submillimeter Galaxy
Presenter: Sao Koyama (Niigata University)
Submillimeter Galaxies (SMGs) are extremely active star-forming galaxies that are predominantly found in the early universe. The star formation rate (SFR) of the brightest SMGs can exceed 1000 M_sun/yr, and it is an order of magnitude larger than the SFR of star-forming galaxies in the nearby universe. Understanding the nature of SMGs is important for revealing the formation and evolution of galaxies (e.g., mass acquisitions by galaxy collisions or accretion along large-scale structure). The detailed star formation process and spatial distribution within SMGs are beginning to be resolved by ALMA in recent years. As a pilot study using ALMA, we have been observing three of the brightest unlensed SMGs at high-resolution to investigate in detail where and how the stars form in the galaxy.
In this talk, we report recent 0.05 arcsec (370 pc) dust continuum observation of AzTEC-8 at z~3.2 obtained using the ALMA/Band6 (211-275 GHz) and Band7 (275-370 GHz). Our analysis reveals that AzTEC-8 has a strong central concentration with an average SFR surface density of ΣSFR = 2643 M_sun/yr/kpc^2. We also identify an isolated clump (size~0.05 kpc^2) located at about 1 kpc from the center in AzTEC-8 which shows a very high value of ΣSFR = 316 M_sun/yr/kpc^2. In addition, we compare the effective radius (1284 pc) obtained from modeling by GALFIT and other bright star-forming galaxies, and we find that AzTEC-8 is significantly more compact than other luminous galaxies at z~3. The absence of an obvious major companion around AzTEC-8 suggest large-scale gas accretion, as opposed to a major merger, is the fuel to maintain the observed high SFR.
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