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<!DOCTYPE html>
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<title>Ryan Chown - Research Website</title>
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<body>
<header>
<nav>
<ul>
<li><a href="#home">Home</a></li>
<li><a href="#research">Research</a></li>
<li><a href="#cv">CV & Publications</a></li>
<li><a href="#teaching">Teaching</a></li>
<li><a href="#contact">Contact</a></li>
</ul>
</nav>
</header>
<main>
<section id="home" class="hero">
<div class="profile-container">
<img src="figs/logo.jpg" alt="Ryan Chown" class="profile-photo">
<h1>Dr. Ryan Chown</h1>
<p class="subtitle">
Astrophysicist with a passion for teaching<br>
<i>As of September 2025:</i> Assistant Professor (Tenure-Track) at <a href="https://www.algomau.ca" target="_blank">Algoma University</a><br>
<a href="https://sites.google.com/view/phangs/home" target="_blank">PHANGS-JWST</a> Technical Working Group Lead<br>
<i>Previously:</i> Postdoc in Astronomy at <a href="https://www.osu.edu" target="_blank">The Ohio State University</a> and <a href="https://www.uwo.ca" target="_blank">University of Western Ontario</a><br>
</p>
</div>
</section>
<section id="research" class="research-section">
<h2>About Me</h2>
<div class="research-summary">
<p>I'm an astronomer studying the interstellar medium and galaxy evolution, using cutting edge infrared and radio telescopes, with a strong interest in teaching. I completed my BSc and MSc in Physics at <a href="https://www.mcgill.ca" target="_blank">McGill University</a>, and my PhD in Astrophysics at <a href="https://www.mcmaster.ca" target="_blank">McMaster University</a> in 2021. From 2021-2023 I was a postdoc in the Department of Physics and Astronomy at the <a href="https://www.uwo.ca" target="_blank">University of Western Ontario</a>, and from 2023-2025 I was a postdoc in the Department of Astronomy at <a href="https://www.osu.edu" target="_blank">The Ohio State University</a>. In September 2025 I started as an Assistant Professor in the Department of Computer Science and Technology at <a href="https://www.algomau.ca" target="_blank">Algoma University</a> in Sault Ste. Marie, Ontario.</p>
</div>
<div class="telescope-gallery">
<div class="telescope-item">
<img src="figs/jwst.jpg" alt="James Webb Space Telescope" class="telescope-image">
<p class="telescope-caption"><a href="https://webb.nasa.gov/" target="_blank">JWST</a></p>
</div>
<div class="telescope-item">
<img src="figs/alma.jpg" alt="Atacama Large Millimeter/submillimeter Array" class="telescope-image">
<p class="telescope-caption"><a href="https://almascience.nrao.edu/" target="_blank">ALMA</a></p>
</div>
<div class="telescope-item">
<img src="figs/vla.jpg" alt="Very Large Array" class="telescope-image">
<p class="telescope-caption"><a href="https://public.nrao.edu/telescopes/vla/" target="_blank">VLA</a></p>
</div>
<div class="telescope-item">
<img src="figs/jcmt.jpg" alt="The James Clerk Maxwell Telescope" class="telescope-image">
<p class="telescope-caption"><a href="https://www.eaobservatory.org/jcmt/" target="_blank">JCMT</a></p>
</div>
</div>
<h2>My Work</h2>
<div class="research-summary">
<p>The question at the heart of my research is: how do the fundamental ingredients of the matter cycle in galaxies -- gas, dust, and stars -- interact to shape the structure and evolution of galaxies? My work spans from high-resolution studies of the Milky Way to spatially-resolved analysis of nearby galaxies, with a focus on understanding the physical processes that shape the interstellar medium across different environments and metallicities.<br><br>
I work in collaboration with an amazing group of colleagues around the world. As a member of the <a href="https://sites.google.com/view/phangs/home" target="_blank">Physics at High Angular Resolution in Nearby Galaxies Survey (PHANGS)</a> collaboration, I lead the technical working group focused on the reduction and analysis of <a href="https://webb.nasa.gov/" target="_blank">JWST</a> data, and I lead scientific analyses of the PHANGS-JWST data, with particular focus on the relationships between tracers of cold gas (CO) from <a href="https://almascience.nrao.edu" target="_blank">ALMA</a>, and PAH emission across nearby galaxies at high resolution with JWST. I also lead JWST-focused science work in the <a href="https://www.lglbs.org" target="_blank">Local Group L-Band Survey (LGBS)</a> collaboration, which is studying the nearest low-metallicity dwarf galaxies with best-in-class 21 cm HI mapping from the <a href="https://www.nrao.edu/telescopes/vla/" target="_blank">VLA</a>. I am also a member of the <a href="https://www.pdrs4all.org" target="_blank">PDRs4All</a> team (I previously led the data reduction working group), which obtained some of the very first JWST observations ever taken. These data provide an unprecedented view of the <a href="https://en.wikipedia.org/wiki/Orion_Nebula" target="_blank">Orion Nebula</a>, a prototypical star-forming region in the Milky Way. <br><br>
<!--
My research leverages multi-wavelength observations from near-infrared to radio, using facilities such as <a href="https://webb.nasa.gov/" target="_blank">JWST</a>, <a href="https://www.spitzer.caltech.edu/" target="_blank">Spitzer</a>, <a href="https://almascience.nrao.edu" target="_blank">ALMA</a>, and the <a href="https://public.nrao.edu/telescopes/vla/" target="_blank">VLA</a> to study the gas and dust in galaxies, often in combination with shorter wavelength observations like optical integral field spectroscopy. My work spans from high-resolution studies of the Milky Way to spatially-resolved analysis of nearby galaxies, with a focus on understanding the physical processes that shape the interstellar medium across different environments and metallicities.</p> -->
</div>
<div class="research-grid">
<div class="research-item">
<img src="figs/potm2411a.jpg" alt="galaxy research" class="research-image">
<h3>The life cycle of fundamental ingredients of the ISM in nearby galaxies</h3>
<p>Cold molecular gas (H₂) is the fuel for star formation, but it is not directly observable. Instead, astronomers use radio wavelength emission from the second-most abundant molecule, carbon monoxide (CO), to trace this gas. Much of my recent work has focused on a) understanding an apparently ubiquitous relationship between CO emission and mid-infrared emission from another important class of molecules called polycyclic aromatic hydrocarbons (<a href="https://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbon" target="_blank">PAHs</a>), and b) understanding the life cycle of PAHs in the ISM. With JWST, we are now able to study the CO versus PAH relationship at unprecedented spatial resolution and sensitivity, allowing us to probe the structure of cold gas at a level of detail that is not possible with CO.</p>
<p>Image: JWST (NIRCam + MIRI) composite image of NGC 2090 showing dust and PAH emission (red) and starlight (blue). <br>
Credit: ESA/Webb, NASA & CSA, A. Leroy. <a href="https://esawebb.org/images/potm2411a" target="_blank">Link to original image.</a></p>
<button class="read-more" onclick="toggleDetails('research1')">Read More</button>
<div id="research1" class="research-details">
<h4>Overview</h4>
<p>As a postdoc at <a href="https://www.osu.edu" target="_blank">The Ohio State University</a>, I'm conducting a comprehensive study of the relationship between cold gas (H₂ and HI) and polycyclic aromatic hydrocarbons (PAHs) across different galaxy environments. This work is done in collaboration with the Physics at High Angular Resolution in Nearby Galaxies Survey collaboration (<a href="https://sites.google.com/view/phangs/home" target="_blank">PHANGS</a>). My work spans from analyzing PHANGS-JWST images of nearly 75 massive spiral galaxies at ~50-150 pc resolution (one such image is shown above) to studying the nearest low-metallicity dwarf galaxies (NGC 6822 and the Wolf-Lundmark-Melotte galaxy, or WLM) at the unprecedented resolution of ~2 pc, where the structure of individual molecular clouds can be seen in great detail. The latter work is done in collaboration with the Local Group L-Band Survey team (<a href="https://www.lglbs.org" target="_blank">LGBS</a>). This multi-scale approach allows me to investigate how the CO-PAH relationship varies with metallicity and galactic environment. Characterizing this relationship across environments helps us establish PAH emission as a sensitive, high-resolution tracer of cold gas.</p>
<h4>Image Gallery</h4>
<div class="gallery">
<figure>
<img src="figs/fig1_scatter_co_vs_f770w_pah_all_20250116.png" alt="PHANGS-JWST image">
<figcaption>ALMA CO(2-1) vs. 7.7 μm PAH emission across 70 galaxies at ~100 pc resolution. We find a strong correlation between CO and PAH emission across all galaxies. The relationship is well-fit by a power law with a slope of 0.98, similar to that found in previous work (Leroy et al. 2023) even though we considered over 10x more data. Figure from <a href="https://ui.adsabs.harvard.edu/abs/2024arXiv241005397C/abstract" target="_blank">Chown et al. (2025)</a>. </figcaption>
</figure>
<figure>
<img src="figs/fig2_co_at_f770w_pah_scatter_vs_log_ssfr.png" alt="Dwarf galaxy JWST image">
<figcaption>We found that individual galaxies show tight correlations between CO and PAH emission, and that the y-intercept of the relationship for a given galaxy is related to the star formation rate of that galaxy. This means that the CO-to-PAH ratio is higher in galaxies with higher star formation rates. It also means that one can obtain a better estimate of CO intensity from PAH intensity in a galaxy by estimating the y-intercept using the fit in this plot. Figure from <a href="https://ui.adsabs.harvard.edu/abs/2024arXiv241005397C/abstract" target="_blank">Chown et al. (2025)</a>.</figcaption>
</figure>
<figure>
<img src="figs/ngc2903_alma_co21_contour_and_predicted_from_f7770w.pdf" alt="ALMA image of molecular gas">
<figcaption><b>Hey it works pretty well!</b> Proof of concept showing ALMA CO(2-1) intensity (left) and predicted CO intensity from PAH intensity (right) for NGC 2903. The predicted CO intensity is obtained by estimating the y-intercept of the relationship in the previous plot. One can see that the prediction is very good overall. Importantly, the predicted CO map is more sensitive -- work is ongoing to understand what this faint emission is actually tracing. One likely candidate is the low-density neutral hydrogen that pervades galaxies. Figure from <a href="https://ui.adsabs.harvard.edu/abs/2024arXiv241005397C/abstract" target="_blank">Chown et al. (2025)</a>.</figcaption>
</figure>
</div>
<h4>Recent Publications: </h4>
<p>1. R. Chown et al., "Polycyclic Aromatic Hydrocarbon and CO(2-1) Emission at 50-150 pc Scales in 70 Nearby Galaxies", <em>accepted for publication in ApJ (2025). <a href="https://ui.adsabs.harvard.edu/abs/2024arXiv241005397C/abstract" target="_blank">arXiv link.</a></em></p>
<p>2. A. Leroy et al., "PHANGS-JWST First Results: Mid-infrared Emission Traces Both Gas Column Density and Heating at 100 pc Scales", <em>ApJL Volume 944, Issue 2 (2023). <a href="https://ui.adsabs.harvard.edu/abs/2023ApJ...944L...9L/abstract" target="_blank">arXiv link.</a></em></p>
<p>3. R. Chown et al., "A new estimator of resolved molecular gas in nearby galaxies", <em>MNRAS Volume 500, Issue 2 (2021). <a href="https://ui.adsabs.harvard.edu/abs/2021MNRAS.500.1261C/abstract" target="_blank">arXiv link.</a></em></p>
<p>Images above from <a href="https://ui.adsabs.harvard.edu/abs/2024arXiv241005397C/abstract" target="_blank">Chown et al. (2025)</a> </p>
</div>
</div>
<div class="research-item">
<img src="figs/orion_bar.png" alt="pdrs4all" class="research-image">
<h3>The Impact of Stars on Interstellar Dust in Our Own Backyard</h3>
<p>During my postdoc at the <a href="https://www.uwo.ca" target="_blank">University of Western Ontario</a>, I led the first analysis on polycyclic aromatic hydrocarbon (PAH) emission from the <a href="https://www.stsci.edu/jwst/science-execution/approved-ers-programs" target="_blank">JWST Early Release Science (ERS)</a> program #1288 <a href="https://www.pdrs4all.org" target="_blank">PDRs4All</a>, which mapped the Orion Bar, a prototypical star forming region in the Milky Way. PDRs4All was one of 13 ERS programs, whose data were taken in the first days of the mission after the launch on Christmas Day, 2021. A major science goal of the program was to understand the origins and evolution of <a href="https://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbon" target="_blank"> polycyclic aromatic hydrocarbons (PAHs)</a> in the interstellar medium. On Earth, PAHs are a common component of car exhaust and barbecue smoke. In space, they are a vital component of the interstellar medium, where they glow brightly in the near- to mid-infrared (their emission is particularly bright between about 3-15 μm). PAHs are thought to be formed when stars shed their outer layers, and are then swept up into the ISM to lead busy and important lives (we would not exist without them). However, their formation and destruction processes are not well understood. </p>
<p>Image credit: ESA/Webb, NASA, CSA, Mahdi Zamani, PDRs4All</p>
<button class="read-more" onclick="toggleDetails('research2')">Read More</button>
<div id="research2" class="research-details">
<h4>Overview</h4>
<p>As part of the PDRs4All team, I led a paper where we discovered the first evidence of photo-processing of PAHs as a function of distance from ionizing stars within a single PDR. This research examined how radiation from massive stars affects the surrounding interstellar medium in the Milky Way. Thanks to the incredibly high quality of the data from JWST, I produced what now represents a major reference for mid-infrared spectra of PDRs for years to come, and a catalog of PAH features, many of which were new discoveries. Along with this, I led another paper comparing the uniquely high-quality imaging and integral field spectroscopy data, to produce empirical prescriptions for measuring spectral features (e.g. line intensities) from imaging data alone. These prescriptions can be used in other galaxies to estimate the intensity of spectral features from imaging data alone. </p>
<h4>Image Gallery</h4>
<div class="gallery">
<figure>
<img src="figs/bar.png" alt="Orion Bar PDR">
<figcaption>JWST near- to mid-infrared image of the Orion Bar (the diagonal ridge of emission). Young stars from the Trapezium star cluster (to the upper right, outside of the image) ionize the surrounding gas (blue) and the Orion Bar is the "skin" of the molecular cloud, where the transition from ionized gas to atomic gas occurs. The material in the lower left is mostly molecular hydrogen. We obtained JWST integral field spectroscopy of a sub-region extending across the Bar (shown in the zoom in), allowing us to probe variations in PAH properties with varying physical conditions. Figure from <a href="https://ui.adsabs.harvard.edu/abs/2024A%26A...685A..75C/abstract" target="_blank">Chown et al. (2024)</a>. </figcaption>
</figure>
<figure>
<img src="figs/spec.png" alt="Spectral analysis of PAH features">
<figcaption>JWST spectrum of the Orion Bar, taken from the Atomic PDR aperture labelled above. PAH emission features are shown in red. Figure from <a href="https://ui.adsabs.harvard.edu/abs/2024A%26A...685A..75C/abstract" target="_blank">Chown et al. (2024)</a>.</figcaption>
</figure>
</div>
<h4>Recent Publications</h4>
<p>1. R. Chown et al., "PDRs4All. IV. An embarrassment of riches: Aromatic infrared bands in the Orion Bar", <em>A&A, 685 (2024). <a href="https://ui.adsabs.harvard.edu/abs/2024A%26A...685A..75C/abstract" target="_blank">arXiv link.</a></em></p>
<p>2. R. Chown et al., "PDRs4All XI. Empirical prescriptions for the interpretation of JWST imaging observations of star-forming regions", <em>Submitted to A&A (2025). <a href="https://ui.adsabs.harvard.edu/abs/2024arXiv241106061C/abstract" target="_blank">arXiv link.</a></em></p>
<p></p>
</div>
</div>
</div>
</section>
<section id="cv" class="cv-section">
<h2>Curriculum Vitae</h2>
<p>Download my CV <a href="figs/cv.pdf">here</a>.</p>
<p> A list of my publications can be found <a href="https://ui.adsabs.harvard.edu/public-libraries/9vFPtKP7SZGBig0wC28SBA" target="_blank">here</a>.</p>
</section>
<section id="teaching" class="teaching-section">
<h2>Teaching</h2>
<p> PHYS 1006: Introductory Physics I (Fall 2025) </p>
<p> <a href="phys1007.html">PHYS 1007: Introductory Physics II (Winter 2026)</a> </p>
<p> MATH 2056: Discrete Mathematics II (Winter 2026) </p>
</section>
<section id="contact" class="contact-section">
<h2>Contact</h2>
<div class="contact-info">
<p>Email: <a href="mailto:ryan.chown@algomau.ca">ryan.chown@algomau.ca</a></p>
<p>Faculty of Computer Science and Technology <br> Algoma University <br> Sault Ste. Marie, ON </p>
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