Molecular gas in a young radio galaxy: 4C 31.04 - A NOEMA study

Aizpún, Julia (2025) Molecular gas in a young radio galaxy: 4C 31.04 - A NOEMA study. Bachelor's Thesis, Astronomy.

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Abstract

We present a multi-line molecular gas analysis of the young radio galaxy (≤ 5000 years old) 4C 31.04, focusing on the impact of radio jet–ISM interactions. Using NOEMA observations of CO(1–0), CN(1–0), and CS(2–1), together with previously published HCO+(1–0) and CO(2–1) data, we study both emission and absorption features in the central kiloparsec. The CO(1–0) emission traces a rotating molecular disc extending ∼10.4 kpc, while the absorption lines, unresolved at a beam size of 2.4′′ × 1.6′′, reveal dense, turbulent gas with line widths up to ∼170 km s−1. This is consistent with strong jet interaction, closely matching the kinematics of previously observed H i absorption. The absorbing gas shows column densities with lower limits of N(CO) ≈ 5.4×1017 cm−2 and N(CN) ≈ 6×1016 cm−2. Elevated line intensity ratios are observed, including CN/CO ≈ 1.5 and HCO+/CO ≈ 1.2 in absorption, indicating strong chemical enrichment. The CO(2–1)/CO(1–0) ratio of 1.5, further confirms the presence of highly excited, turbulent gas. These line enhancements, in the absence of strong UV or X-ray fields as in the case of 4C 31.04, are best explained by shock-driven chemistry and cosmic ray ionization caused by the expanding jets.

Item Type:	Thesis (Bachelor's Thesis)
Supervisor name:	Morganti, R. and Murthy, S.N.
Degree programme:	Astronomy
Thesis type:	Bachelor's Thesis
Language:	English
Date Deposited:	22 Jul 2025 06:52
Last Modified:	22 Jul 2025 06:52
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/36240

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