Theses and Dissertations from DePaul University

Date of Award

Spring 2026

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Physics

College

College of Science and Health

First Advisor

Anuj Sarma

Abstract

Stars form in cores deep within cold (10 K) clouds of hydrogen gas. As material is accreted onto the central object inside these cores (the protostar), powerful outflows that channel mass away from the protostar are also launched. The launching mechanism for these outflows is still not fully understood. This thesis presents observations of the 22 GHz continuum emission from two star-forming regions, NGC 7129 FIRS2 and IC 1396-n. The immediate aim of these observations is to find where this continuum emission is coming from, particularly if it is free-free emission from a jet or outflow, and the long term goal is to investigate what such continuum observations reveal about jets and outflows and their launching process. The data were obtained with the Karl G. Jansky Very Large Array (VLA) in A-configuration and were calibrated and imaged using the Astronomical Image Processing System (AIPS). Compact continuum sources were detected toward each target. For NGC 7129 FIRS2 the full-band image yields an integrated flux density of 443 ± 28 µJy and a marginally resolved deconvolved size of 0.124′′ × 0.081′′, with a faint 3σ extension aligned with the known bipolar molecular outflow. For IC 1396-n the primary source has an integrated flux density of 556.5 ± 22.7 µJy and is accompanied by a second compact source 2.6′′ to the north-northwest (174 ± 18 µJy), along with a third source in between that is at the limit of detectability. A spectral index measured across the fifteen usable sub-bands gives α ≈ +2.41 ± 0.04 (Sν ∝ να) for the primary component of NGC 7129 FIRS2, too high to be from free-free emission alone, even in the optically thick limit. The brightness temperature derived in the Rayleigh-Jeans limit is TB ≈ 103 K for the strongest component in NGC 7129 FIRS2, suggesting optically thin emission. Therefore, there must be a significant contribution from dust emission in the case of NGC 7129 FIRS2. In contrast, the calculated value of α ≈ +0.36±0.04 for the strongest component in IC 1396-n. The brightness temperature was calculated to be 219 K and 310 K for the IC 1396-n primary and secondary peaks respectively. Therefore, in IC 1396-n, we are likely observing free-free emission from shock-ionized jets or outflows.

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