Christina W. Lindberg

I am a sixth-year astronomy Ph.D. candidate at Johns Hopkins University working with Dr. Claire Murray and other researchers in the ISM* group at STScI. I am broadly interested in the interstellar medium (ISM), stellar populations, and galaxy dynamics in the nearby Universe, as well as how we can use modern data science techniques to extract more information from existing data.

Research Projects

My thesis research focuses on using photometric surveys to characterize resolved stars and their line-of-sight extinction in nearby galaxies like the Magellanic Clouds and M31. Through multi-phase tracers like dust extinction, I study the structure of the interstellar medium (ISM). I am primarily interested in understanding how the multi-scale structure of the ISM changes as a function of metallicity and galactic environment, and how these changes influence star formation and the impact of stellar feedback.

I am involved in several photometric surveys of nearby galaxies. Some of my recent work and ongoing projects from these collaborations are described below.

Small-Scale ISM Structure around Massive Stars

Massive stars are significant contributors of ionizing radiation and momentum, which can destroy surrounding gas in just a few Myrs. While most massive stars are observed in spiral structures associated with giant molecular clouds, we observe that massive stars also exist in the interarm regions of galaxies like M31, where relatively little star-forming material is observed at length scales greater than 10 pc.

By comparing the SED-fit line of sight extinction of massive stars (probing the sub-pc ISM structure) with other general ISM tracers (25-pc extinction maps, CO, HI), we find massive stars have on average the same amount of extinction at small scales, regardless of their location within a galaxy, indicating that even at 25-pc, we are still not capable of resolving star-forming ISM structures.

Relevant paper: Lindberg, Murray, Dalcanton, et al. 2024, ApJ

The entire catalog of 40,000 massive star candidates from the PHAT footprint can be downloaded from MAST.

Mapping the Interstellar Medium via Dust Extinction

Dust extinction is a valuable tool for tracing the multi-phase distribution and content of the ISM, constraining dust-to-gas ratios in different environments, constraining dust emissivity properties at low metallicities, etc. For nearby galaxies with resolved stellar populations, we can leverage multi-band photometry to measure the amount of extinction along the line of sight.

With extinction measurements towards nearly a million stars across the Magellanic Cloud from the Scylla survey, we can use these measurements to construct high-resultion extinction maps at parsec-scales, giving us an unpresedented view the mulit-phase structure of the ISM.

Relevant Paper: Lindberg + Scylla Team; “Scylla V: Sub-Parsec Extinction Maps in the Magellanic Clouds”, In Prep (2024).

Past Research

Over the years, I have worked on a variety of astronomy projects, ranging from asteroids to the circumgalactic medium. Check out my publications on ADS or my project code on Github.

AsteroGaP: Modeling Sparse Asteroid Lightcurves with Gaussian Processes

Lindberg, Huppenkothen, et al. 2022, AJ

At the University of Washington, I worked with Dr. Daniela Huppenkothen at the DIRAC Institute, leading the development of a new statistical method for inferring the rotational period of asteroids called AsteroGaP (Asteroid Gaussian Processes). Through a combination of Bayesian statistics, MCMC, and Gaussian Processes, we were able to develop a new method to accurately characterize asteroid light curve profiles from sparse photometric measurements.

Werk SQuAD

Wilde et al. 2021, ApJ

During my undergraduate at the University of Washington, I was a member of Prof. Jessica Werk's Student Quasar Absorption Diagnosticians (SQuAD), researching the CGM2 survey, which seeks to constrain the cosmic baryon cycle of nearby galaxies. As a Werk SQuAD member, I classified thousands of absorption features from dozens of quasars observed with the Hubble Space Telescope (HST) Cosmic Origin Spectrograph.

Selected Observing Programs

Software

Selected Presentations

Below is a selection of the talks and posters I have presented at conferences, workshops, and seminars. The full PDF for each presentation can be accessed by clicking on the corresponding image.

Resolving the Multi-Scale Interstellar Medium of Local Group Galaxies

Observational constraints on the small-scale structure of the interstellar medium (ISM) are critical for understanding how star formation and feedback processes drive galaxy evolution across cosmic time. The last decade has seen an explosion of panchromatic HST imaging of nearby galaxies (e.g. PHAT/PHAST, HTTP, PHATTER, LUVIT, Scylla, etc.). With stellar SED fitting techniques like the Bayesian Extinction And Stellar Tool (BEAST), we can harness these rich data to simultaneously characterize individual resolved stars and extract information about the ISM. I present new parsec-scale dust extinction maps in the Magellanic Clouds (Scylla), and discuss future BEAST science to investigate how small-scale processes shape galaxy evolution.

A recording of my presentation can be viewed here.

Constraining the 3D Structure of the ISM in 30 Doradus with Scylla

Despite the close proximity of the Magellanic Clouds (XMC), we still do not have a comprehensive understanding of the 3D distribution of their ISM. With new, deep multi-wavelength observations from HST, the Scylla survey will enable us to constrain distances to dusty gas structures along nearly 100 lines of sight, allowing us to probe the overall distribution of the ISM within the XMC. As a test case, we present preliminary findings on the distances toward individual molecular clouds within the 30 Doradus region of the LMC. We find that, although these molecular clouds are close in projection, they are in fact separated by several kpc in distance. Coupled with observations from ALMA, these results indicate outflowing, CO-rich gas in the region.

Slides from talk presented at the XMC Workshop: Milky Clouds Over Manhattan at the Flatiron Institute (2024). A recording of my presentation can be viewed here.

Dust around massive stars is agnostic to galactic environment: New insights from PHAT & BEAST

Resolving the environments of massive stars is crucial for understanding their formation mechanisms as well as their impact on galaxy evolution. An important open question is whether massive stars found in diffuse regions outside of spiral arms formed in-situ or migrated there after forming in denser environments. To address this question, we use multi-resolution measurements of extinction in the Andromeda Galaxy (M31) to probe the interstellar medium (ISM) surrounding massive stars across a variety of galactic environments. We construct a catalog of 42,107 massive star candidates using resolved stellar photometry from the Panchromatic Hubble Andromeda Treasury (PHAT) program plus stellar and dust model estimates by the Bayesian Extinction and Stellar Tool (BEAST). We quantify galactic environments by computing surrounding stellar densities using kernel density estimation. We then compare high-resolution line-of-sight extinction estimates from the BEAST with 25-pc resolution dust maps from PHAT which measure the total column density distribution of dust. Our key finding is that, although the average total column density of dust increases with the density of stars, the average line-of-sight extinction towards massive stars remains constant across all environments. This suggests that massive stars have a uniform amount of dust in their immediate environment, regardless of their location in the galaxy. One possible explanation for these findings is that small molecular clouds are still capable of forming massive stars, even if they are not resolvable at 25-pc. These results indicate that massive stars are forming in the sparse regions of M31, as opposed to migrating there.

Slides from plenary talk given at the Resolving Galaxy Ecosystems Across All Scales conference in Hong Kong (2023).

Leadership and DEI

Through graduate school, I have been involved in various student leadership positions. From 2022-2023, I served as the president of the JHU Physics and Astronomy Graduate Students (PAGS) where I organized department initiatives regarding teaching, pay raises, and officing, representing over 100 graduate students in the program. I am committed to helping improve diversity, equity, and inclusion in academia. Following my term as PAGS President, I spear-heading efforts to investigate instances of examination bias and improve equity in department examinations through discussions with department and university leadership.

I currently serve as one of the JHU representative for the Astronomy Graduate Congress, which provides a common platform for graduate students to discuss issues regarding graduate education in astronomy. I am also on the local organizing committee of the recently-formed Gender Minorities and Women in Physics (G-WiP) chapter at JHU (est. 2022).

About Me

I'm originally from Denmark, but grew up in Germany and the United States. In my free time, I like to pursue more artistic (aka less computer-screen depedent) hobbies. I’ve recently started learning cello and, for the past few years, I've been singing soprano in the JHU ECCO and Choral Society. In the meantime, I’m probably taking lots of pictues of my cat, Oliver.