The next Student Seminar on Monday, August 10, in Seminar Room 1 of PH1 at 3pm will feature the following talks, in this order:

1. "Under the Hood of miniCHAI Submillimeter Receiver" by Kateryna Vynokurova

Observations of the interstellar medium at different stages of the baryonic cycle give scientists insight into the physics of star formation and galaxy evolution. In the submillimeter range, this information is extracted through high-resolution spectroscopy, capable of recovering the gas kinematics and cloud dynamics encoded in spectral line profiles. But how do we actually get this information? How does incoming radiation become a spectrum, and what kind of receiver is needed to make that happen? This talk offers a behind-the-scenes look at miniCHAI, a single-pixel, dual-frequency receiver and one of the first-light instruments for the Fred Young Submillimeter Telescope (FYST). I will follow the incoming wave through a chain of quasioptical mirrors, into a cryostat cooled to 4 Kelvin, and onto two superconducting mixers that, using a phase stable local oscillator signal, downconvert it to a frequency low enough for ordinary electronics to record—all while preserving the phase and amplitude information that ultimately becomes the spectrum you would recognise from a data-reduction pipeline. Along the way, I will highlight some of the mechanical and thermal design decisions that make this chain work, and why an instrument like miniCHAI has to exist before its 64-pixel successor can begin mapping molecular clouds across the sky.

2. "Facilitating the search for 1-amino-2-propanol in space by studying its rotational spectrum" by Prachi Misra

In astrophysics, rotational spectroscopy is an indispensable tool for studying astrophysically relevant molecules. Molecules are crucial in various astrophysical processes, such as planet and star formation as well as interstellar chemistry. The unique rotational spectra or fingerprints of each molecule enable us to identify them in observations with radio telescopes. By analysing these fingerprints, we can determine molecular abundances and learn about the chemistry of the interstellar medium.
Ethanolamine (NH2CH2CH2OH), recently identified in the molecular cloud G+0.693−0.0272, is one such complex organic molecule. The addition of a methyl (CH3) group to ethanolamine forms 1-amino-2-propanol (1-a-2-p, NH2CH2CH2(OH)CH3), a promising candidate for future astronomical detection.
The rotational spectra of 1-a-2-p were recorded using chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy in the frequency ranges of 12-26.5 GHz and 75-110 GHz using home-built spectrometers. This approach provides broadband, high-resolution rotational spectra with high sensitivity. Measurements were performed at ∼10 K in the lower-frequency range using a supersonic jet expansion and at ∼300 K in the higher-frequency range. In addition to the lowest-energy conformer of 1-a-2-p, a second conformer, predicted to be 4.9 kJ/mol higher than the previously reported conformer, has been observed for the first time in this study. The rotational constants for both the ground and vibrationally excited states of both conformers were determined and will be presented. Additionally, nuclear quadrupole hyperfine splitting arising from the 14N nucleus was resolved in the lower-frequency range measurements. These high-resolution spectra of 1-a-2-p will help in searching for it in astrophysical environments.

3. "Dense Gas Tracers as Temporal and Structural Evolution Markers of Molecular Clouds" by Oerd Xhemollari

The chemistry of star-forming clouds reveals how gas evolves from diffuse to dense phases, but chemical reactions cannot always keep up with the rapid dynamics of turbulence and gravitational collapse. As a result, molecular abundances often fall out of equilibrium, making it unclear which species reliably trace certain regions within the cloud.
To address this, we present non-equilibrium molecular abundances for chemical species not yet explored in 3D-MHD simulations of forming molecular clouds. We chemically post-process tracer particles from the SILCC-Zoom simulations with the astrochemistry pipeline of Panessa et al. (2023), using the latest public KIDA network with >8,000 reactions and 557 species.
By analyzing the temporal and structural evolution of molecular abundances, we identify in detail the formation regions of major dense-gas tracers such as CS, SO, HCN, HNC, and N₂H⁺. This enables us to assess their reliability as tracers of dense gas under highly dynamic conditions, only possible by the non-equilibrium chemical modeling we implemented here. Consistent with recent observational studies, our column-density maps reveal that N₂H⁺ acts as a more selective tracer of dense gas compared to the other species.
We also compare abundance evolution across cloud environments and find systematic differences between hydrodynamic and MHD clouds: magnetic fields delay chemical evolution and reduce formation efficiency at fixed dynamical time, highlighting their impact. We demonstrate that part of this timing offset can be mitigated when tracer abundances are interpreted as indicators of evolutionary stage rather than as functions of density alone.
Moreover, we discuss which ranges of volume density and column density are preferentially traced by each molecule and how these ranges increase by orders of magnitude as clouds evolve. This provides a physical interpretation for the observational presence of "dense-gas tracers" in diffuse regions.
Overall, our results connect the evolving chemistry of dense gas with its observable line emission, refining how molecular tracers are used to infer cloud evolution.


4. "Revealing Magnetospheric Properties with Effelsberg Ultra Broad Band" Lucia Gebauer (myself)

Reconstructing the pulsar magnetosphere is essential for understanding the origin of pulsar radio emission, which remains a long-standing open question. Polarisation analysis offers key insight by constraining the underlying magnetic field geometry. However, propagation effects within the magnetosphere introduce disturbances that complicate efforts to recover this structure.
The Effelsberg Radio Telescope's Ultra-Broad-Band (UBB) receiver offers a unique opportunity to probe pulsar emission across a wide, high-frequency range (1.3–6 GHz). In this talk, I present an analysis of single pulses from bright pulsars observed with UBB. While emission is expected to be highly linearly polarised at the source, it becomes progressively depolarised during propagation. By isolating the most highly polarised single pulses and exploiting UBB's broad frequency coverage, we can trace how emission properties evolve across both frequency and time.
Among the bright pulsars selected, I will focus on B0329+54, chosen for its brightness and proximity, which make it especially well suited to single-pulse analysis. In addition, I briefly show how this framework extends to pulsars within pulsar wind nebulae, using B1929+10 as a case study.