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arXiv · 2504.02758

ALMA uncovers optically thin and multi-component CO gas in the outflowing circumnuclear disk of NGC1068

Yuze Zhang·Serena Viti·Santiago García-Burillo·Ko-Yun Huang
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Abstract

Active galactic nuclei (AGNs) influence their host galaxies through winds and jets that can drive molecular outflows, traceable with CO line emissions using the Atacama Large Millimeter Array (ALMA). Recent studies leveraging ALMA data have proposed a three-dimensional outflow geometry in the nearby Seyfert II galaxy NGC 1068, a key target for AGN unification theories. Using ALMA observations of CO(2-1), CO(3-2), and CO(6-5) transitions at roughly 0.1 arcseconds (approximately 7 parsecs) resolution, we analyzed the temperature, density, and kinematics of NGC 1068's circumnuclear disk (CND), focusing on the molecular outflow. Through local thermodynamic equilibrium (LTE) analysis, we derived column densities and rotational temperatures, indicating optically thin gas and CO-to-H2 (XCO) conversion factors between 4.8 and 9.6 times smaller than the Milky Way value. The inferred molecular mass outflow rate is mostly below 5.5 solar masses per year, with the dominant contribution northeast of the AGN. After subtracting the rotation curve of the CND, we modeled averaged line profiles in each region using single and multi-component Gaussian fits. Several profiles within or near the AGN wind bicone required multiple components with significant velocity shifts, suggesting multi-component complex outflow kinematics. We observe lateral variation in CO kinematics along the AGN wind bicone and a misalignment between the molecular and ionized outflow directions. These results imply that the dynamic impact of the ionized AGN wind on the molecular gas in the CND may be limited. However, the molecular outflow shows a complex, asymmetric structure.

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Yuze Zhang, Serena Viti, Santiago García-Burillo, Ko-Yun Huang. 2025-04-03. ALMA uncovers optically thin and multi-component CO gas in the outflowing circumnuclear disk of NGC1068. https://doi.org/10.1051/0004-6361%2F202553704

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