| Name: Poojapriyatharsheni J |
| Affiliation: Lady Doak College affiliated to the Madurai Kamaraj University |
| Conference ID: ASI2026_39 |
| Title: Multi-Frequency Radio Recombination Line Analysis of 37 Galactic Plane Positions with Detected [N II] Far-Infrared Emission |
| Abstract Type: Poster |
| Abstract Category: Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Author(s) and Co-Author(s) with Affiliation: J. Poojapriyatharsheni(Department of Physics, Lady Doak College, Madurai, Tamil Nadu, 625002, India), D. Anish Roshi(Florida Space Institute, University of Central Florida, Orlando 32826, USA.), Mayumi Sato(Florida Space Institute, University of Central Florida, Orlando 32826, USA), R. Nimma Elizabeth(Department of Physics, Lady Doak College, Madurai, Tamil Nadu, 625002, India), Kimberly L. Emig(National Radio Astronomy Observatory, Charlottesville, VA 22903, USA), Pedro Salas(Green Bank Observatory, 155 Observatory Road, Green Bank, WV 24915, USA), Loren D. Anderson(Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506, USA) |
| Abstract: The physical state and structure of the fully ionized interstellar medium (ISM) in the inner Galaxy is governed by star formation, turbulence, and large-scale Galactic dynamics. Hydrogen radio recombination lines (RRLs), combined with radio continuum data, provide an extinction-free probe of the ISM, enabling measurements of electron temperature, emission measure, density, and kinematics. We conducted multi-frequency RRL surveys with the Green Bank Telescope (GBT) at 800 and 340 MHz across the Galactic plane (|b| ≤ 1°), covering −5° ≤ ℓ ≤ 32.6°, a region containing major spiral-arm crossings, prominent HII region complexes, and diffuse ionized gas. The new observations have angular resolutions of 21′ and 50′ at 800 and 340 MHz respectively and are complemented by an existing 5.8 GHz RRL survey with 2.8′ resolution, providing sensitivity to both compact and extended emission.
We analyze RRL emission at 37 positions along the Galactic plane (b = 0°), selected to overlap spatially with the Herschel [N II] far-infrared survey (Pineda et al. 2019) . As [N II] fine-structure lines trace ionized gas, a key goal is to relate RRL and [N II] emission.
A custom Python-based spectral analysis pipeline using the lmfit library was developed to perform simultaneous baseline subtraction and Gaussian fitting. Individual RRL components were separated based on velocity centroids and linewidths. Non–local thermodynamic equilibrium (non-LTE) modeling was performed with the RRLpy module, incorporating radio continuum data at 408 and 1420 MHz and constraints from the 5.8 GHz RRL observations to account for beam dilution.
The modeling constrains electron densities, emission measures, and non-thermal velocity dispersions. Monte Carlo simulations quantify uncertainties and validate the results. Cross-comparisons with previous RRL and [N II] studies place new constraints on the physical conditions and spatial distribution of ionized gas in the inner Galaxy.
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