Special Talk

• Special Talks

  Speaker: Farhan Hasan (STScI)
  Title: Shaping Cosmic Ecosystems Through Baryon Cycling: Simulations, Observations, and the promise of the Roman Era
  Abstract: Galaxy evolution is governed by the exchange of baryons across cosmic ecosystems, from the interstellar medium to the cosmic web, yet how these flows shape galaxy gas content, star formation, and morphology remains unclear. I will address this question across the majority of cosmic time by combining observations with state-of-the-art simulations. First, I will present how galaxy cold gas content and star formation depend on the cosmic web environment at z<0.5 using ground-based HI and HST-based galaxy surveys. Tensions with cosmological simulations reveal questions about the competition between cold gas accretion and shock-heating/gas stripping due to cosmic filaments. At z>1, simulations predict a dramatic transition in how large-scale environments affect the star formation activity and morphological characteristics of galaxies. I will introduce a powerful "slime mold"-inspired method to characterize large-scale structures: applications to deep wide-field galaxy surveys from Roman will enable robust, novel mapping of the z>1 cosmic web. Finally, I will show how a JWST slitless spectroscopic survey is charting the mass-metallicity relation (MZR) - a fundamental tracer of the baryon cycle - at z~1.7-3.5. We constrain the MZR down to unprecedentedly low masses and show its statistical dependence on morphology at this epoch for the first time. These results highlight the role that accretion and outflows play in shaping galaxies. I will conclude with how Roman will enable a dramatic improvement in these statistics and revolutionize our understanding of the cosmic baryon cycle at the peak epoch of galaxy formation.

  Speaker: Lakeisha M. Ramos Rosado (JHU)
  Title: Revealing the Atmosphere of the Inflated Hot Jupiter NGTS-2b Through Findings from JWST and HST
  Abstract: Current challenges in the field of exoplanet atmospheres revolve around understanding how atmospheric dynamics, formation mechanisms, and the properties of host stars interact to influence planetary evolution. With high sensitivity and resolution, observations from JWST and HST can reveal variations in atmospheric properties, such as temperature and chemical composition, providing insights into how different environments influence planetary evolution. We present the first observations of NGTS-2b, an inflated hot Jupiter transiting a bright F5V star. With a notably low density of 0.226 g cm⁻³ and an orbital period of 4.51 days, NGTS-2b stands out as an exceptional target for atmospheric study. Its significant transit depth of 1.0%, combined with the brightness of its host star (V = 10.96), uniquely positions it for in-depth exploration of atmospheric composition through transmission spectroscopy. By examining key molecular species across a wide range of wavelengths, including water vapor, carbon dioxide, and methane, our observations uncover insights into the atmospheric chemistry and thermal structure of NGTS-2b. Our efforts aim to enhance our understanding of this specific planet, while also contributing to the Grand Tour program, which seeks to provide insights into a broader population study of gas giants. This research promises to yield valuable insights into the atmospheric properties of one of the least dense exoplanets currently known, contributing to our understanding of exoplanetary atmospheres.

  Speaker: Nimisha Kumari (STScI)
  Title: JWST View of Pox 186: The Best Local Analog of Reionization Era Galaxies
  Abstract: One of the frontier goals of observational cosmology is to understand the epoch of reionization and its connection to the early star-forming galaxies, which show several high-ionization lines (e.g., CIV). While these distant sources are too faint to put tight constraints on stellar population models, local metal-poor dwarf galaxies are also found to have similar spectral features in the UV and IR as the high-z galaxies and can be used as reliable analogues. A local, metal-poor dwarf galaxy, Pox 186, exhibits the brightest CIII] 1908 A emission (equivalent width, EW ~36 A) observed in the local Universe, along with an extreme [OIII] 88 micron/[CII] 158 micron (~ 10) and a bright optical [OIII]+Hbeta emission. Such extreme EWs and line ratios are comparable to those observed in galaxies at redshifts of z ~ 6-7, when the reionization process is thought to be completed. Using JWST/MIRI data of Pox 186, we probe the shape of the ionizing spectrum via high-ionization fine-structure lines such as [OIV], molecular gas content via the H2 rotational lines, and dust content via the PAH features especially prominent in the mid-infrared spectrum. This comprehensive characterization of Pox 186 provides an essential benchmark for interpreting JWST observations of high-redshift galaxies and advancing our understanding of the physical processes that shaped the reionization era.