A Strongly Lensed Dusty Starburst of an Intrinsic Disk Morphology at Photometric Redshift of 7.7
arxiv(2024)
摘要
We present COSBO-7, a strong millimeter (mm) source known for more than
sixteen years but was just revealed its near-to-mid-IR counterpart by the James
Webb Space Telescope (JWST). The precise pin-pointing by the Atacama Large
Millimeter Array (ALMA) on the exquisite NIRCam and MIRI images show that it is
a background source gravitationally lensed by a single foreground galaxy, and
the analysis of its spectral energy distribution by different tools
consistently derives its photometric redshift at ∼7.7. Strikingly, our
lens modeling based on the JWST data shows that it has a regular, disk
morphology in the source plane. The dusty region giving rise to the
far-IR-to-mm emission seems to be confined to a limited region to one side of
the disk and has a high dust temperature of >90 K. The galaxy is experiencing
starburst both within and outside of this dusty region. After taking the
lensing magnification of μ≈ 2.53.6 into account, the
intrinsic star formation rate is several hundred M_⊙ yr^-1 both
within the dusty region and across the more extended stellar disk, and the
latter already has >10^10M_⊙ of stars in place. If all this is true,
COSBO-7 presents an extraordinary case that is against the common wisdom about
galaxy formation in the early universe; simply put, its existence poses a
critical question to be answered: how could a massive disk galaxy come into
being so early in the universe and sustain its regular morphology in the middle
of an enormous starburst?
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