Central concentration of warm and dense molecular gas in a strongly lensed submillimeter galaxy at z=6

Abstract

We report the detection of the CO(12-11) line emission toward G09-83808 (or H-ATLAS J090045.4+004125), a strongly-lensed submillimeter galaxy at $z=6.02$, with Atacama Large Millimeter/submillimeter Array observations. Combining previously detected [O III]$88\mu \mathrm{m}$, [N II]$205\mu \mathrm{m}$, and dust continuum at 0.6mm and 1.5mm, we investigate the physical properties of the multi-phase interstellar medium in G09-83808. A source-plane reconstruction reveals that the region of the CO(12-11) emission is compact ($R_{\mathrm{e},\mathrm{CO}}=0.49_{-0.19}^{+0.29}\mathrm{kpc}$) and roughly coincides with that of the dust continuum. Non-local thermodynamic equilibrium radiative transfer modeling of CO spectral-line energy distribution reveals that most of the CO(12-11) emission comes from a warm (kinetic temperature of $T_{\mathrm{kin}}=320\pm 170$K) and dense ($\log (n_{H2}/\mathrm{c}{\mathrm{m}}^{-3})=5.4\pm 0.6$) gas, indicating that the warm and dense molecular gas is concentrated in the central 0.5-kpc region. The luminosity ratio in G09-83808 is estimated to be $L_{\mathrm{CO}(12-11)}/L_{\mathrm{CO}(6-5)}=1.1\pm 0.2$. The high ratio is consistent with those in local active galactic nuclei (AGNs) and $6<z<7$ quasars, the fact of which implies that G09-83808 would be a good target to explore dust-obscured AGNs in the epoch of reionization. In the reconstructed [O III]$88\mu \mathrm{m}$ and [N II]$205\mu \mathrm{m}$ cubes, we also find that a monotonic velocity gradient is extending over the central starburst region by a factor of two and that star-forming sub-components exist. High-resolution observations of bright [C II]$158\mu \mathrm{m}$ line emissions will enable us to characterize the kinematics of a possible rotating disk and the nature of the sub-components.

13 pages, 11 figures, accepted for publication in PASJ

References in corpus (23)

• Cold streams in early massive hot haloes as the main mode of galaxy formation
• Formation of Massive Galaxies at High Redshift: Cold Streams, Clumpy Disks and Compact Spheroids
• A Dust-Obscured Massive Maximum-Starburst Galaxy at a Redshift of 6.34
• Galaxy growth in a massive halo in the first billion years of cosmic history
• The Herschel Dwarf Galaxy Survey: I. Properties of the low-metallicity ISM from PACS spectroscopy
• The Herschel Comprehensive (U)LIRG Emission Survey (HerCULES): CO Ladders, fine structure lines, and neutral gas cooling
• Bulge-forming galaxies with an extended rotating disk at z~2
• Molecular gas in the Herschel-selected strongly lensed submillimeter galaxies at z~2-4 as probed by multi-J CO lines
• A spatially resolved study of cold dust, molecular gas, HII regions, and stars in the $z=2.12$ submillimeter galaxy ALESS67.1
• High-J CO SLEDs in nearby infrared bright galaxies observed by Herschel-PACS
• Spatially Resolved Interstellar Medium and Highly-Excited Dense Molecular Gas in the Most Luminous Quasar at z=6.327
• Distinguishing Mergers and Disks in High Redshift Observations of Galaxy Kinematics
• First CO(17-16) emission line detected in a z > 6 quasar
• The most distant, luminous, dusty star-forming galaxies: redshifts from NOEMA and ALMA spectral scans
• Dynamical characterization of galaxies up to $z\sim 7$
• Probing the full CO spectral line energy distribution (SLED) in the nuclear region of a quasar-starburst system at $z=6.003$
• CO, H2O, H2O+ line and dust emission in a z = 3.63 strongly lensed starburst merger at sub-kiloparsec scales
• Molecular Line Observations in Two Dusty Star-Forming Galaxies at z = 6.9
• Merger induced clump formation in distant infrared luminous starburst galaxies
• Spatially resolved CO SLED of the Luminous Merger Remnant NGC 1614 with ALMA
• A non-corotating gas component in an extreme starburst at z=4.3
• Detection of nitrogen and oxygen in a galaxy at the end of reionization
• Source structure and molecular gas properties from high-resolution CO imaging of SPT-selected dusty star-forming galaxies

Cited by in corpus (2)

• Warm Gas in the Vicinity of a Supermassive Black hole 13 Billion Years Ago
• Bright beacons? ALMA non-detection of a supposedly bright [OI] 63-um line in a redshift-6 dusty galaxy