A Multi-Headed Attack on Dust Evolution and Star Formation in the Magellanic Clouds
The LMC and SMC are nearby dwarf galaxies whose close proximity, and low enrichment (20-50%) provide opportune laboratories for studying the effects of low metallicity on small-scale physics.
I am one of the core builders for Scylla (HST 15891), a 500-orbit Hubble Space Telescope (HST) parallel imaging program (Cycles 27-29) to complement the HST Ultraviolet (UV) Legacy library of Young Stars as Essential Standards (ULLYSES) survey. With high-resolution multi-band photometry of nearly a million stars (Murray et al., 2024), we can (1) map the extinction curve and dust grain properties at high resolution in a diverse range of interstellar conditions; (2) constrain the multi-dimensional structure of gas in the Large and Small Magellanic Clouds; and (3) measure the comprehensive star formation and chemical enrichment histories of nearby dwarf galaxies (Cohen et al., 2024; Cohen et al., 2024).
All data and data products are publicly released on MAST.
I used the BEAST to measure individual masses, ages, metallicities, distances, and line-of-sight extinction for over 1.5 million stars from their multi-band SEDs. With deep, high-resolution photometry, we resolve stars down to sub-solar masses (as low as 0.6 solar-masses), giving us unprecedented insight into the stellar content and formation history of these fields (Lindberg et al., 2024). We also probe extinction across a wide range of ISM environments which will be used in future works to investigate variations in dust composition and constrain the fraction of CO-dark molecular gas at low metallicities. %we can gain a better understanding of the dust content in these galaxies.
Currently, I am pioneering a new method for turning stellar extinctions into 2D extinction maps. These maps will allow us to trace the parsec-scale structure of the ISM across gas phases, providing some of the highest resolution maps of the ISM ever in external galaxies, independent of systematics associated with standard dust emission tracers.
A Scylla field near 30 Doradus in the LMC. The dust extinction map (left) is constructed using BEAST fits of individual stars from the six-band photometry. We compare this dust map with ancillary ISM emission tracers overlapping the same region: far-IR dust emission from Herschel (middle), and molecular gas (CO) from ALMA (right).
References
2024
Scylla. I. A Pure-parallel, Multiwavelength Imaging Survey of the ULLYSES Fields in the LMC and SMC
Claire E. Murray, Christina W. Lindberg, Petia Yanchulova Merica-Jones, and 17 more authors
Scylla. III. The Outside-in Radial Age Gradient in the Small Magellanic Cloud and the Star Formation Histories of the Main Body, Wing, and Outer Regions
Roger E. Cohen, Kristen B. W. McQuinn, Claire E. Murray, and 13 more authors
By analyzing the spectral energy distributions (SEDs) of resolved stars in nearby galaxies, we can constrain their stellar properties and line-of-sight dust extinction. From the Scylla survey, we obtain ultraviolet to near-infrared photometry from Wide Field Camera 3 onboard the Hubble Space Telescope for more than 1.5 million stars in the SMC and LMC. We use the Bayesian Extinction and Stellar Tool (BEAST) to analyze the multi-band SEDs of these sources and characterize their initial masses, ages, metallicities, distances, and line-of-sight extinction properties (e.g. Av, Rv). We apply quality cuts and perform validation simulations to construct a catalog of over 550,000 stars with high-reliability SED fits, which we use to analyze the stellar content and extinction properties of the SMC and LMC. We detect stars with masses as low as 0.6 M ⊙. BEAST stellar age distributions show a jump in observed stars around 6 Gyrs ago, which agrees with star-formation histories. Extinctions (A_V) in both galaxies follow a log-normal distribution. We compare Av with ancillary gas and dust tracers like HI, H_α, and far infrared (FIR) dust emission and find positive correlations on a field-by-field basis. We convert observed A_V to predicted dust surface densities using the Draine et. al. (2014) model and find A_V-based dust surface densities are a factor of 2.5 lower than observed FIR-based dust surface densities, a correction factor similar to other studies.
@article{lindberg2025a,author={{Lindberg}, Christina W. and {Murray}, Claire E. and {Yanchulova Merica-Jones}, Petia and {Bot}, Caroline and {Burhenne}, Clare and {Choi}, Yumi and {Clark}, Christopher J.~R. and {Cohen}, Roger E. and {Gilbert}, Karoline M. and {Goldman}, Steven R. and {Gordon}, Karl D. and {Hirschauer}, Alec S. and {McQuinn}, Kristen B.~W. and {Roman-Duval}, Julia C. and {Sandstrom}, Karin M. and {Tarantino}, Elizabeth and {Williams}, Benjamin F.},title={{Scylla IV: Intrinsic Stellar Properties and Line-of-Sight Dust Extinction Measurements Towards 1.5 Million Stars in the SMC and LMC}},journal={arXiv e-prints},keywords={Astrophysics - Astrophysics of Galaxies},year={2024},month=oct,eid={arXiv:2410.19910},pages={arXiv:2410.19910},doi={10.48550/arXiv.2410.19910},archiveprefix={arXiv},eprint={2410.19910},primaryclass={astro-ph.GA},adsurl={https://ui.adsabs.harvard.edu/abs/2024arXiv241019910L},adsnote={Provided by the SAO/NASA Astrophysics Data System}}
