Low Frequency Carbon Radio Recombination Lines I: Calculations of Departure Coefficients

Abstract

In the first paper of this series, we study the level population problem of recombining carbon ions. We focus our study on high quantum numbers anticipating observations of Carbon Radio Recombination Lines to be carried out by the LOw Frequency ARray (LOFAR). We solve the level population equation including angular momentum levels with updated collision rates up to high principal quantum numbers. We derive departure coefficients by solving the level population equation in the hydrogenic approximation and including low temperature dielectronic recombination effects. Our results in the hydrogenic approximation agree well with those of previous works. When comparing our results including dielectronic recombination we find differences which we ascribe to updates in the atomic physics (e.g., collision rates) and to the approximate solution method of the statistical equilibrium equations adopted in previous studies. A comparison with observations is discussed in an accompanying article, as radiative transfer effects need to be considered.

Submitted to ApJ

References in corpus (9)

• Theory of Star Formation
• Radio Recombination Lines in Galactic HII Regions
• Radio recombination lines from the largest bound atoms in space
• Carbon and hydrogen radio recombination lines from the cold clouds towards Cassiopeia A
• Low Frequency Carbon Radio Recombination Lines I: Calculations of Departure Coefficients
• Discovery of Carbon Radio Recombination Lines in M82
• LOFAR detections of low-frequency radio recombination lines towards Cassiopeia A
• H, He-like recombination spectra II: $l$-changing collisions for He Rydberg states
• Exact Bound-Bound Gaunt Factor Values for Quantum Levels up to n=2000

Cited by in corpus (21)

• The First Large Absorption Survey in HI (FLASH): I. Science Goals and Survey Design
• Science with the Murchison Widefield Array: Phase I Results and Phase II Opportunities
• The initial gas-phase sulfur abundance in the Orion Molecular Cloud from sulfur radio recombination lines
• Low Frequency Carbon Radio Recombination Lines I: Calculations of Departure Coefficients
• Carbon radio recombination lines from gigahertz to megahertz frequencies towards Orion A
• Direct estimation of electron density in the Orion Bar PDR from mm-wave carbon recombination lines
• Low Frequency Carbon Radio Recombination Lines II: The Diffuse Interstellar Medium
• A Q-band line survey towards Orion KL using the Tianma radio telescope
• H-, He-like recombination spectra III: $n$-changing collisions in highly-excited Rydberg states and their impact on the radio, IR and optical recombination lines
• Inverted level populations of hydrogen atoms in ionized gas
• The ionization fraction in OMC-2 and OMC-3
• Multiline observations of hydrogen, helium, and carbon radio-recombination lines toward Orion A: A detailed dynamical study and direct determination of physical conditions
• Searching for the largest bound atoms in space
• A High Resolution Study of Carbon Radio Recombination Lines towards Cassiopeia A
• Discovery of Hydrogen Radio Recombination Lines at z=0.89 towards PKS 1830-211
• Spectroscopy with the Engineering Development Array: cold H${}^{+}$ at 63 MHz towards the Galactic Centre
• Low-Frequency Radio Recombination Lines Away From the Inner Galactic Plane
• Efficient computation of collisional $\ell$-mixing rate coefficients in astrophysical plasmas
• An nl-model with a full radiative transfer treatment for level populations of hydrogen atoms in a spherically symmetric H II region
• Constraints on the properties of warm ionized gas from low-frequency hydrogen radio recombination lines
• Observations of Carbon Radio Recombination Lines with the NenuFAR telescope. I. Cassiopeia A and Cygnus A