Oral Presentation

Another tail of Big Three Dragons: A [N II] 122 μm constraint and a new dust-continuum detection of a z = 7.15 bright Lyman Break Galaxy with ALMA

Author(s): Yuma Sugahara (NAOJ/Waseda), Akio K. Inoue (Waseda), Takuya Hashimoto (Tsukuba), Satoshi Yamanaka (Ehime), Seiji Fujimoto (Dawn), Yoichi Tamura (Nagoya), Hiroshi Matsuo (NAOJ), Christian Binggeli (Uppsala), Erik Zackrisson (Uppsala)

Presenter: Yuma Sugahara (NAOJ/Waseda U.)

We present new ALMA Band 7 observations of the [NII] 122 μm emission line and underlying 120 μm dust continuum in a Lyman break galaxy at z = 7.15, B14-65666 (“Big Three Dragons”), which is the first object detected in all [OIII] 88 μm, [CII] 158 μm, and dust continuum emission at z > 6. The dust continuum is detected at a ∼19σ significance level. By performing FIR SED fitting, we obtain the best-fit infrared luminosity of log10(LIR/Lsun) = 11.6–12.0, depending on the emissivity index. The [NII] line is not detected. The 3σ upper limit of the [NII] luminosity is 8.1*10^7 Lsun. From the [NII], [OIII], and [CII] line luminosities, we estimate the nebular parameters as functions of the metallicity using the Cloudy. If the metallicity is high (Z > 0.4 Zsun), the nebular parameters are comparable to those measured in low-redshift galaxies and the N/O abundance ratio is constrained to be sub-solar. At Z < 0.4 Zsun, in contrast, the nebular parameters drastically change with the metallicity. The constraints on N/O become too weak due to high ionization parameters. Finally, we discuss the location of B14-65666 on the BPT diagram.