Honors Thesis Presentations: Riley Rosener, Rohan Gupta, Kyla Mullaney, Jonah Medoff, Laine Hirn, and Audrey Scott

1:30–4:30 pm ERC 401

1:30-2:00 pm

Riley Rosener "On the Detectability of Emission from Exoplanet Outflows"

Riley Rosener

Exoplanets close to their host stars experience high amounts of irradiation, causing drastic atmo2 spheric escape that can be measured as a gas outflow from the planet using certain chemical tracers. 3 To date, exoplanet atmospheric escape has thus far only been probed using transmission spectroscopy 4 to measure line absorption. While it is theoretically possible to measure outflows via emission spec5 troscopy, the observability of these signatures may limit the practical application of this method. In 6 this work, we investigate different strategies of observing atmospheric outflow emission, finding that Hα and He∗ 7 consistently give the highest signal-to-noise ratio (SNR) across all planets tested. We 8 consider a variety of exoplanets with confirmed detections of the 10833˚A metastable helium absorption 9 line and other outflow tracers. We use the updated and improved PyTPCI (The-PLUTO-CLOUDY 10 Interface) software and wrapper with enhanced stability and usability to run combined 1D photochem11 istry, spectrum synthesis, and hydrodynamics simulations of our chosen exoplanet systems. Using these 12 results and information about the observational facilities that are most sensitive to each diagnostic, 13 we calculate the resultant signal-to-noise ratio, eclipse depth, optical depth, bremsstrahlung flux, and 14 theoretical mass loss rates for our target systems. Ultimately, we find that these signals will not be 15 large enough to detect and distinguish during the secondary eclipse using existing facilities in less than 16 5 transits. We find a maximum predicted signal-to-noise ratio of 2.4 from the hot Jupiter HD 189733b at 10× solar metallicity in the He∗ 17 line. For future observational campaigns, our work suggests focus18 ing on bright, well-characterized systems like hot Jupiters HD 189733b and HD 209458b, so that any 19 potential emission signals are maximized. Although these emissions are not currently detectable with 20 Keck and HST, they may be within reach of the next generation of extremely large telescopes.

2:00-2:30 pm

Rohan Gupta "Wavelength Calibration of the Extreme Precision Radial Velocity Spectrograph MAROON-X using a Laser Frequency Comb and a Fabry-Perot etalon"

Rohan Gupta

The requirement of ever-increasing precision in radial velocity measurements places increasing demands on the wavelength calibration schemes. MAROON-X in the past has used a combined thorium argon and etalon wavelength calibration scheme that has been able to simultaneously leverage the global accuracy of the thorium argon lamp and the high local information content of a Fabry-Perot etalon. While this calibration scheme was able to meet the stringent precision requirements for radial velocity measurements of short period planets, it was unable to meet the long-term stability demands for MAROON-X. The installation of a laser frequency comb at MAROON-X allows for significant improvement in long-term stability, while simultaneously improving the accuracy of the calibration. This work details the calibrations sources and techniques to derive a wavelength solution and drift correction for MAROON-X and describes the first steps of implementing the laser frequency comb spectra into this scheme.

2:30-3:00 pm

Kyla Mullaney "Simulating the Evolution of Sub-Neptune Planets Including Both Photo-evaporation and Magma-Atmosphere Hydrogen Exchange"

Kyla Mullaney

The Kepler sample of exoplanet transit data revealed a bi-modality in the radius distribution of short-period sub-Neptune-size planets: the radius distribution peaks at 1.3 R⊕ and 2.4 R⊕, and shows a relative lack of planets with radius 1.5-2 R⊕. This underdensity is referred to as the sub-Neptune radius gap, and could be key for understanding the evolution of common sub-Neptune-size planets. The prevailing theory of its cause is that sub-Neptunes begin with large H/He atmospheres, but atmospheric escape removes the atmospheres of many sub-Neptunes and leaves smaller, more dense rocky cores. This process may be shaped by photo-evaporative mass loss, as a heating source for atmospheric escape. Additionally, magma core-atmosphere hydrogen exchange can, in some scenarios, provide additional hydrogen causing increased retention of the atmosphere. Numerical simulation routines for photo-evaporative mass loss and core-atmosphere hydrogen exchange exist separately within MESA, the Modules for Experiments in Stellar Astrophysics software. However, no study thus far has modeled both effects simultaneously. We present the first simulation of sub-Neptune planets with simultaneous photo-evaporative mass loss and dynamic magma core-atmosphere hydrogen exchange in MESA. We update MESA routines for photo-evaporative mass loss to current version compatibility and adaptively combine atmospheric escape and core-envelope exchange to run individually and simultaneously. We further provide a demonstration of initial case study planetary evolution tracks. This work will enable us to further explore the parameter spaces of host star type, planet orbital period, irradiation, and other planetary parameters. In future work, we can use this new routine to explore radius evolution at high irradiation regimes. These important planetary evolution mechanisms may play a key role in shaping the slope of the radius valley, and we present the first simultaneous modeling of both phenomena in MESA.

3:00-3:30 pm

Jonah Medoff "Searching for Dwarf Galaxy Satellites of NGC 55 with the DELVE-DEEP Survey"

Jonah Medoff

We report the results of a search for satellite dwarf galaxies around the isolated, low-mass host, NGC 55, with the DEEP component of the DECam Local Volume Exploration (DELVE-DEEP) survey. NGC 55 is the first of four isolated, Magellanic analogs in the Local Volume around which DELVE-DEEP aims to search for satellite galaxies. Unlike previous satellite searches around isolated, low-mass hosts, we implement two distinct detection methods: one that targets over-densities of resolved, red-giant-branch sources, and one that targets over-densities of unresolved, low-surface-brightness sources. Additionally, we perform artificial star and dwarf galaxy simulations to measure our photometric completeness and detection sensitivity. With our two detection methods combined, we measure a high detection sensitivity for both large, bright dwarf galaxies containing primarily resolved sources as well as fainter, more compact dwarf galaxies with mostly unresolved sources. Our satellite search yielded 7 potential dwarf galaxy candidates, however none appear to have a high likelihood of being real. Therefore, we construct a satellite luminosity function for NGC 55 using only its two previously known satellites, ESO 294-010 and NGC55-dw1.

3:30-4:00 pm

Laine Hirn "Characterizing the Turbulent Circumgalactic Gas Using Integral Field Spectroscopy"

Laine Hirn

The giant intragroup nebula discovered in the sight-line of PKS 1127-145 serves as a window into the formation and evolution of galaxies and the energy transfer in galactic halos. By analyzing the kinematics of the central nebula through velocity structure functions and the ionization through emission line ratios, properties of this diffuse gas were explored, and information regarding ionization parameters, density, excitation sources, and more is revealed. Using the KUBEVIZ software, I performed component line fitting on data collected from the Multi-Unit Spectroscopic Explorer (MUSE). This allowed for the production of a velocity map of the nebula, from which a velocity structure function was constructed in order to characterize the turbulence of the diffuse contents. Data from the Hubble Space Telescope (HST) also reveals the locations of stellar regions, and an additional velocity structure function was produced with these regions excluded from the data. Initial results indicate a potentially steeper slope than that proposed by Kolmogorov (1941) for isotropic, homogeneous, incompressible turbulent flows, but additional research is necessary to account for the nebula’s large scale velocity gradient and projection effects. In addition to exploring the kinematics of the nebula, the electron density and ionization state of the gas were investigated by analyzing the ratios of nebular emission lines. In particular, the [O III]/Hb and [N II]/Ha ratios were computed for constructing the “Baldwin, Phillips, & Terlevich” (BPT) diagram, which allows for discriminating between different ionizing sources such as starburst galaxies and active galactic nuclei (AGN). This revealed a spatial variation in the ionization state of the gas, potentially explained by sources such as shocks and turbulent mixing.

4:00-4:30 pm

Audrey Scott "Characterization of Optical Coupling for polarization-sensitive mm-Wave Line Intensity Mapping Spectrometers"

Audrey Scott

Millimeter wave line intensity mapping has the potential to unlock cosmic history at redshifts between the Cosmic Microwave Background and contemporary galaxy surveys, helping fill in critical gaps that may lead to an increased understanding of large-scale structure and the mechanisms of inflation. However, despite advancements stemming from mm-wave on-chip spectrometers, technological challenges remain, including in optical components that facilitate vertical integration to pack more detectors in a limited focal plane. In this thesis, I demonstrate a method of characterizing the optical coupling of additively manufactured metal dual-polarization sensitive orthomode transducers utilizing tests run on a Vector Network Analyzer, high-fidelity CT scans, and data from HFSS.

Event Type


May 24