Special Talk

• Special Talks

  Speaker: Intae Jung (STScI)
  Title: Probing Conditions for Lyman-Continuum Escape in the Reionization Epoch with HST UV Observations            ​​​​​​​
  Abstract: Highlighting two key HST studies on Lyman-continuum (LyC) escape from local analogs of high-redshift galaxies, I first discuss HST imaging observations of eight gravitationally-lensed galaxies at z = 1.3 - 3.0 that revealed no significant LyC flux. These findings challenge the expectation of higher LyC escape fractions from UV faint sources and emphasize the need for larger sample sizes to account for anisotropic LyC escape. Additionally, I present an HST spectroscopic study of five local compact star-forming galaxies (CSFGs) with extreme [OIII]/[OII] ratios. These targets show strong CIV emission, indicative of hard ionizing radiation and substantial LyC leakage, resembling properties observed in reionization-era galaxies. Collectively, these studies demonstrate the value of HST observations in advancing our understanding of the physical conditions conducive to LyC escape, providing insights into reionization studies.

  Speaker: Beena Meena (STScI)
  Title: Investigating Properties of Young Massive Stars in Nearby Galaxies using High Resolution UV Survey with HST  ​​​​​​​
  Abstract: The Galaxy UV Legacy Project (GULP) is a large treasury program, which utilizes the unique spatial resolution and ultraviolet capabilities of the Hubble Space Telescope. We have acquired Far-UV (FUV) and Near-UV (NUV) imaging of 27 nearby star-forming galaxies. These observations enable us to trace the regions of most recent star formation, detailing the characteristics of resolved massive stars, OB associations, and young clusters. Simultaneously, these data allow for an examination of the effects of UV dust attenuation in various extragalactic environments. This presentation provides an overview of the GULP program, focusing on recent findings related to the star formation properties of young stellar groups that are only observable with UV observations using HST. Our investigation includes an analysis of the impact of UV radiation on dust in correlation with varying star-formation rates. This FUV+NUV study of the local Universe serves as a crucial reference for interpreting ongoing and future high redshift galaxy surveys with the James Webb Space Telescope and understanding their role in cosmic reionization. Additionally, combination of GULP UV + HST optical + JWST IR observations will provide a baseline observations for future missions such as Habitable Worlds Observatory.

  Speaker: Matilde Mingozzi (ESA/AURA @ STScI)
  Title: Tracking down the origin of UV photons in local high-z analogs with UV emission line imaging             ​​​​​​​
  Abstract: Far ultraviolet emission lines are fundamental to interpret the ionized interstellar medium (ISM) properties of the first generation of galaxies that James Webb Space Telescope (JWST) has been observing. The COS Legacy Archive Spectroscopic SurveY (CLASSY) HST/COS treasury program provided the first high- resolution spectral catalog of local high-z analogues to investigate their stellar and gas properties to improve the diagnostic power of UV lines. However, in order to fully understand the physical conditions that give rise to their excitation, we need to spatially tackle these diagnostics. In this talk, I will show the results of an HST imaging program aimed at spatially resolving for the first time CIV1548,1551, [CIII]1907,CIII]1909 and Lyalpha simultaneously in three nearby high-z analogs, using a combination of ACS, STIS and WFC3 filters. The powerful combination of available optical integral field spectroscopy data, HST observations and state-of-the-art models is crucial to investigate and interpret the morphology of the emission line diagnostics, track the ionization source(s) of the gas and the ionization structure in our targets. This study can help us understand the ISM conditions of the earliest galaxies and gives us precious insights for future UV observatories, such as UVEX and HWO.