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<!DOCTYPE html>
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<title>Research | Hayden Foote</title>
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<div class="header">
<h1>Hayden R. Foote <span class="pronouns">He/Him</span></h1>
<p>Astronomy Graduate Student</p>
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<div class="navbar">
<a href="/index.html">Home</a>
<a href="/about.html">About Me</a>
<a class="active" href="/research.html">Research</a>
<a href="/values.html">Values</a>
<a href="/outreach.html">Outreach</a>
<a href="/cv.html">My CV</a>
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<h3>Click <a href="https://ui.adsabs.harvard.edu/search/q=orcid%3A0000-0003-1183-701X&sort=date%20desc%2C%20bibcode%20desc&p_=0">here</a> for a full list of my publications on ADS.</h3>
<h2 class="pagetitle">Selected Research Projects</h2>
<h3>Discovery of a Collision Between a Stellar Stream and A Milky Way Satellite </h3>
<img class="pageimage" src="/images/CPS-Seg2.png" alt="CPS-Segue2" style="height:auto;max-width:760px;">
<p class="caption" style="max-width: 760px;">Closest approach between stars in the Cetus-Palca stellar stream and Segue 2, an ultra-faint satellite galaxy of the Milky Way. This plot shows member stars of Cetus-Palca and the position of Segue 2 as seen on-sky from Earth, in a coordinate system that is aligned with the stream's direction on the sky. Stream stars for which we have measured 3-D velocities (and therefore determined orbits) are colored by their closest approach distance to Segue 2.</p>
<p>Stellar streams are the destroyed remnants of globular clusters and dwarf galaxies that have been accreted by the Milky Way. One of the most promisiing avenues for constraining the amount of dark matter substructure in our Galaxy is to search for signatures of collisions between dark matter substructures and stellar streams. Modeling shows that by studying kinks, gaps, and other perturbations in stellar streams, we can characterize how clumpy the Milky Way's dark matter distribution is.</p>
<p>In this project, I modeled the orbits of Milky Way satellite galaxies and stellar streams, searching for evidence that a Milky Way satellite had recently collided with a stream, which would provide an important test-case for modeling interactions between streams and dark matter substructure. During the project, I discovered the first known interaction between a low-mass Milky Way satellite galaxy (Segue 2), and a stellar stream (Cetus-Palca). By assembling a member catalog of Cetus-Palca using data from Gaia, H3, and SEGUE, I conducted an orbit analysis of Cetus-Palca's stars, demonstrating that Segue 2 passed through the stream roughly 77 million years ago. <a href="https://ui.adsabs.harvard.edu/abs/2025ApJ...979..171F">Read more here.</a></p>
<h3>Mapping the Dark Matter Wake Induced by the LMC</h3>
<img class="pageimage" src="/images/int_dm_density.png" alt="Wake map" style="height:auto;max-width:760px;">
<p class="caption" style="max-width: 760px;">The density of the LMC's dark matter wake assuming three different models for dark matter physics. We compare cold dark matter without and with self-gravity to fuzzy dark matter with a particle mass of 1e-23 eV. The color shows the density contrast of the background "wind" dark matter particles as they move in the +y-direction past the LMC potential at the center of the box.</p>
<p>My Master's project was centered on the interaction between the Large Magellanic Cloud (LMC) and our own Milky Way (MW) galaxy. The LMC is the MW's largest satellite galaxy, and it has recently (cosmologically speaking) reached its first pericenter passage about 60 million years ago. As the LMC falls through the MW's dark matter halo, its gravity attracts the MW's dark matter to it, forming an overdense region in the MW's halo which traces the path of the LMC's orbit. This gravitational "wake" pulls back on the LMC and slows it down in a process called dynamical friction. </p>
<p>The nature of dark matter remains one of the most pressing mysteries in astronomy. The LMC's wake is a promising observable for distinguishing between competing dark matter models, as the strength and morphology of the wake depends on the microphysics of the dark matter particle. In the project, I created a suite of windtunnel-style simulations studying the formation of the wake in cold (CDM) vs. fuzzy (FDM) dark matter. While the CDM and FDM wakes are similar in size, the fuzzy dark matter wake is dynamically colder than the cold dark matter wake. Furthermore, we found that the dark matter wake's gravity strenghtens the formation of a wake in the Milky Way's stellar halo, providing an observable signature of the dark matter wake. The stellar wake is also slightly hotter in an FDM universe compared to a CDM universe, offering a plausible avenue for distinguishing CDM from FDM. <a href="https://ui.adsabs.harvard.edu/abs/2023ApJ...954..163F/abstract">Read more here.</a></p>
<!-- <h3>The Structure of Eccentric Nuclear Disks</h3>
<img class="pageimage" src="/images/aBySim.png" alt="Mass segregation plot" style="height:auto;max-width:760px;">
<p class="caption" style="max-width: 760px;">The mean semimajor axis of both stellar populations (heavy/light stars) as a function of time in my simulations. Each color line represents a different simulation with a different number of heavy stars. Mass segregation is apparent as the heavy population having lower semimajor axes than the light population. The number of heavy stars also affects the strength of the mass segregation.</p>
<p>As an undergraduate at CU Boulder, my honors thesis explored the internal structure of eccentric nuclear disks (ENDs), a type of star cluster found in galaxy nuclei where the stellar orbits about the supermassive black hole are highly eccentric and spatially aligned. I wrote a suite of <i>N</i>-body simulations that for the first time studied mass segregation in ENDs, a dynamical process found in more common types of star clusters by which the heaviest members sink to the center of the cluster. My simulations confirmed that mass segregation operates in ENDs as it does in spherical clusters and axisymmetric disks. </p>
<p>ENDs are also known for producing an elevated number of tidal disruption events (TDEs), where a star wanders too close to the supermassive black hole and is ripped apart by tidal forces. I also showed that mass segregation causes the most massive objects in an END to be more susceptible to tidal disruption when compared to less massive objects. <a href="https://ui.adsabs.harvard.edu/abs/2020ApJ...890..175F/abstract">Read more here.</a></p> -->
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<p>Email: <span><a href = "mailto: haydenfoote@arizona.edu">haydenfoote@arizona.edu</a></span><br>
GitHub: <span><a href = "https://github.com/hfoote">https://github.com/hfoote</a></span><br>
OrcID: <span><a href="https://orcid.org/0000-0003-1183-701X">0000-0003-1183-701X</a></span></p>
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<p>Office: Room D317, Steward Observatory<br>
933 N Cherry Ave.<br>
Tucson, AZ 85719</p>
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<p>© 2025 Hayden Foote | All Rights Reserved</p>
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