Additional Event Information

• Special Talks

  Speaker: Bethan James (STScI)
  Title: Deciphering the True Properties of Galaxies Across Cosmic Time
  Abstract: Rest-frame UV spectra play a key role in the understanding of massive stellar populations, chemical evolution, feedback processes, and reionization. In the current JWST era, the UV spectroscopic frontier has been pushed to higher redshifts than ever before, to finally reveal the first galaxies in the distant Universe. It is thus fundamental to understand the diagnostic power of UV spectral features. To this end, HST UV spectra of local high-z analogues can present a powerful laboratory, thanks to the level of data quality and spatial resolution the local Universe can offer. In this talk I will describe how, over the past two years, we have harnessed UV spectra of high-z analogues to decipher the `true’ properties of galaxies across cosmic time. Firstly, using the COS Legacy Archive Spectroscopic SurveY (CLASSY), we have tailored a complete UV diagnostic toolkit to explore multi-phase properties of the interstellar medium (i.e., density, temperature, gas-phase metallicity, ionization parameter, source of ionization, star formation rate). Secondly, by comparing abundances in the neutral vs ionized gas we have provided essential insight into enrichment scenarios and mixing timescales in high-z systems. Overall, this talk demonstrates how powerful UV-spectra of local analogues can be in understanding the ISM conditions of the earliest galaxies, and how significant a future UV-IFU would be in making ground-breaking progress.

  Speaker: Larry Bradley (STScI)
  Title: Unveiling Bound Star Clusters in the Cosmic Gems Arc at z ~ 10
  Abstract: JWST was designed to study distant galaxies in the very early universe. While it has discovered many such galaxies, most of them are unresolved. To understand early galaxies and their contribution to reionization, we must directly study the sources producing the ionizing radiation within these galaxies. I will present JWST observations of SPT0615-JD, a bright, strongly lensed galaxy at z~10 that is magnified and stretched into a 5-arcsec-long arc. The magnification reveals bound star clusters within the galaxy, with radii of only a few parsecs. These are the most distant yet observed, at just 500 Myr after the Big Bang. I will summarize our results to date and present upcoming JWST Cycle 3 NIRSpec IFU and MIRI MRS spectroscopic observations of this unique galaxy.

  Speaker: Dan Coe (STScI)
  Title: JWST: One Giant Leap Towards Observing the First Stars
  Abstract: Only when it is dark enough can you see the stars. In our darkest hours, we see what we are made of. We are made of stars. We can be the light shining through the dark. And when we work together, we can accomplish great things. 20,000 people, including many of you, worked for decades to create JWST and launch it deep into the darkness of space to see the first stars. Now thousands of astronomers have written a thousand papers about distant galaxies and stars. We're all working towards the same goal, and I've led my science team with that collaborative spirit. My incredible teammates include Abdurro'uf, Tiger Hsiao, Brian Welch, and Rebecca Larson, all on the job market now. They have used gravitational lensing to reveal and study Earendel, two individual stars observed a billion years after the Big Bang (z = 6). And at earlier times 500 Myr after the Big Bang (z = 10), we've studied individual star clusters as small as 1 pc in radius in the Cosmic Gems Arc and in MACS0647-JD where we've measured ~13% solar metallicity and excess carbon. These results contribute to astronomers' measurements of the buildup of heavy elements in galaxies over 13 billion years. Our ultimate goal is to study the composition of individual stars in the early universe by staring deeply into the dark. We can now see what we are made of thanks to so many people working together to build and operate something extraordinary.

  Speaker: Elena Manjavacas (STScI)
  Title: The Brownie Worlds Team at STScI: Bridging the Gap Between Exoplanets and Brown Dwarfs
  Abstract: In this talk I will present the achievements of a new born Research Group at STScI: the Brownie Worlds. The research of my group focuses in the study of the atmospheres of Brown Dwarfs and Giant Exoplanets to bridge the gap between those two different, but yet very similar worlds. Brown dwarfs (with L, T and Y spectral types) are substellar objects that fill the gap in masses between low-mass stars and planets. The lowest mass brown dwarfs can have masses below the deuterium burning limit, being analogs to directly-imaged exoplanets. Brown dwarfs show also photometric or spectroscopic variability, commonly believed to be due to the presence of heterogeneous clouds in their atmospheres. During this very productive year, we made two very important discoveries for the brown dwarf field: the first one is the discovery that the transition between L and T dwarfs could be delayed in spectral type for young Brown Dwarfs (Manjavacas et al. 2024), as suggested with the JWST/NIRSpec spectrum of 2M1207b. The second one is the discovery that the spectral variability found in brown dwarfs is not only due to clouds, but also disequilibrium chemistry plays an important role (Oliveros-Gomez et al. 2025, in prep.). I will also show what other exciting projects my group is working on, and how they will potentially change the brown dwarf field.

  Speaker: Van Dixon (STScI)
  Title: Evidence of Third Dredge-Up in Post-AGB Stars in Galactic Globular Clusters
  Abstract: As stars ascend the asymptotic giant branch (AGB), third dredge-up (3DU) can enrich their atmospheres in carbon and s-process elements. Indeed, some AGB stars in the Magellanic Clouds are so carbon-rich that soot condenses out of their winds. But AGB stars in Milky Way globular clusters were thought not to be massive enough to support significant enrichment via 3DU. To find out, I gathered from the literature the abundances of CNO and heavy elements in post-AGB stars in Galactic globular clusters. Of the 17 stars in my sample, CNO abundances are available for 11. Of these, four are enhanced in CNO relative to the red-giant stars from which they descended, which I take as evidence of 3DU on the AGB. The enhancement is mainly in the form of carbon. Of the six stars for which only heavy-element abundances are available, one shows s-process enhancements that previous authors have interpreted as evidence of 3DU. In this talk, I will briefly review the theory of low-mass stellar evolution, present the results of my analysis, and consider their implications for future research.

  Speaker: Janice Lee (STScI)
  Title: Lessons From the Spectacular New Views of Nearby Galaxies with JWST
  Abstract: Our PHANGS surveys with HST and JWST have provided most extensive inventories to-date of both optically visible and dust-embedded star clusters in nearby galaxies. A consistent picture has emerged of the early phases of star cluster evolution, using complementary observational tracers and methods of analysis, confirming the short dust clearing timescales (<~3 Myr) reported by optical studies. These findings underscore the significant role of early feedback—pre-supernova mechanisms—in the star formation cycle. I will highlight new results, in particular, from our PHANGS group in Baltimore, and also share other unexpected lessons the public has taught us about these extraordinary data.