Journal
ASTROPHYSICAL JOURNAL
Volume 792, Issue 1, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/792/1/34
Keywords
cosmology: observations; early universe; galaxies: evolution; galaxies: formation
Categories
Funding
- Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan
- Kavli Foundation
- ALMA Japan Research Grant of NAOJ Chile Observatory [NAOJ-ALMA-0017]
- Grants-in-Aid for Scientific Research [24103003, 23340050, 24540230] Funding Source: KAKEN
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We present ALMA observations of the [C II] line and far-infrared (FIR) continuum of a normally star-forming galaxy in the reionization epoch, the z = 6.96 Ly alpha emitter (LAE) IOK-1. Probing to sensitivities of sigma(line) = 240 mu Jy beam(-1) (40 km s(-1) channel) and sigma(cont) = 21 mu Jy beam(-1), we found the galaxy undetected in both [C II] and continuum. Comparison of ultraviolet (UV)-FIR spectral energy distribution (SED) of IOK-1, including our ALMA limit, with those of several types of local galaxies (including the effects of the cosmic microwave background, CMB, on the FIR continuum) suggests that IOK-1 is similar to local dwarf/irregular galaxies in SED shape rather than highly dusty/obscured galaxies. Moreover, our 3 sigma FIR continuum limit, corrected for CMB effects, implies intrinsic dust mass M-dust < 6.4 x 10(7) M-circle dot, FIR luminosity L-FIR < 3.7 x 10(10) L-circle dot (42.5-122.5 mu m), total IR luminosity L-IR < 5.7 x 10(10) L-circle dot (8-1000 mu m), and dust-obscured star formation rate (SFR) < 10 M-circle dot yr(-1), if we assume that IOK-1 has a dust temperature and emissivity index typical of local dwarf galaxies. This SFR is 2.4 times lower than one estimated from the UV continuum, suggesting that <29% of the star formation is obscured by dust. Meanwhile, our 3 sigma [C II] flux limit translates into [C II] luminosity, L-[C II] < 3.4 x 10(7) L-circle dot. Locations of IOK-1 and previously observed LAEs on the L-[C II] versus SFR and L-[C II]/L-FIR versus L-FIR diagrams imply that LAEs in the reionization epoch have significantly lower gas and dust enrichment than AGN-powered systems and starbursts at similar/lower redshifts, as well as local star-forming galaxies.
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