Dissertation defense
Studant: Elis Cristina Silva Sales
Program: Astronomy
Title: "Interferometric study of the protostellar synchrotron jet in the W3(H2O) region"
Advisor: Prof. Dr. Ciriaco Goddi
Judging Committee
- Prof. Dr. Ciriaco Goddi - Presidente e Orientador - IAG/USP
- Profa. Dra. Elisabete Maria de Gouveia Dal Pino - IAG/USP
- Prof. Dr. Anderson Caproni – UNICID
- Dr. Pedro Paulo Bonetti Beaklini - NRAO/VLA (por videoconferência)
Abstract:
Astrophysical jets are observed across various scales, from young stellar objects to active galactic nuclei (AGN). While AGN jets are well-studied, those from young, massive protostars present unique challenges. This dissertation focuses on the TW object in the W3(H$_2$O) region, which displays synchrotron emission -- one of the few known cases in protostellar systems. Using multi-frequency Very Large Array (VLA) observations (3, 6, 10, 15, and 22.25 GHz), we created radio interferometric images with resolutions ranging from 0.11" to 0.86". Due to the complex nature of the source, we employed self-calibration techniques to enhance sensitivity and resolution. We produced total intensity maps across all bands to visualize the emission structures, though high-fidelity images of the jet were limited in some bands due to incomplete u-v coverage. Spectral index maps revealed that the TW jet has a negative spectral index at low frequencies (3 GHz; α = -1.64 +/- 0.82), indicating synchrotron radiation, and transitions to a positive index at higher frequencies (22.25 GHz; α = 1.06 +/- 0.40), suggesting thermal contributions. We also imaged the 22.25 GHz water maser emission, identifying hundreds of maser spots. These masers trace the spatial and velocity structure of the jet and are distributed along its axis, supporting the interpretation that they mark shock fronts where the outflow interacts with the surrounding medium. The observed maser velocities along the line-of-sight range from -90 to -20 km/s, assuming the central protostar moves at -55 km/s. The multi-band data were acquired in full polarization mode, and once calibrated, will help infer the magnetic field properties of the plasma. Future work will refine polarization studies and address current observational limitations, such as improving u-v coverage to enhance sensitivity.
Keywords: Astrophysical jets, protostars, synchrotron emission, spectral index, interferometry.