Special Talk

• Special Talks

  Speaker: Swetha Sankar (JHU)
  Title: When Jets Don’t Quench: H_2 in Star Forming Low-Excitation Radio Galaxies
  Abstract: We present new Gemini/GNIRS near-infrared spectroscopic observations of eight low-redshift ($z<0.1$) blue low-excitation radio galaxies (BLERGs)---a rare subset ($\sim2.5\%$ of low-excitation radio galaxies; LERGs) that complicate the classical jet-mode AGN picture by combining radio activity with star-forming, gas-rich hosts. These star-forming BLERGs exhibit significant warm H$_2$ emission traced via ro-vibrational transitions at $T \sim 2,000$--$4,000$~K. We find that BLERGs span a broad range of mass-normalized warm H$_2$ luminosities ($L_{\rm H_2}/M_\star$), comparable to radio-emitting early-type galaxies, yet without a clear positive dependence on radio power. Instead, the strongest H$_2$ emission preferentially occurs in morphologically disturbed and advanced-merger systems, while compact radio sources ($\lesssim 20$~kpc) remain plausible sites of localized jet--ISM interaction. Together, these results suggest that merger-driven processes---including tidal shocks, gas inflows, and disturbed interstellar medium conditions---are the dominant drivers of warm molecular gas excitation in BLERGs, although localized jet-driven heating may contribute in individual systems. The compact radio morphologies, gas-rich hosts, and rarity of BLERGs are consistent with a short-lived evolutionary phase in which radio AGN activity coexists with an interaction-driven, molecular-rich interstellar medium prior to the onset of large-scale maintenance-mode feedback. Spatially resolved spectroscopy and higher-resolution radio imaging will be essential to disentangle the relative roles of mergers and jets in regulating the molecular gas of jet-mode AGN.

  Speaker: Timothy Brandt (STScI)
  Title: Moving Objects in JWST and Roman Data
  Abstract: A moving object breaks the fundamental property of constant per-pixel count rates in an astronomical image read out up-the-ramp. I will show how to fit a moving object's path across a detector as that detector is read out nondestructively. This will use the full likelihood function for every pixel subject to a constant count rate plus a time-dependent count rate due to a moving source. This approach extracts maximal information on a moving source's position and speed and enables the source to be accurately removed from the image. It also clearly distinguishes between cosmic rays and moving sources: both produce similar tracks, but a moving source deposits its signal steadily through the exposure. This method can be used for space-based images with minor Solar system bodies in the foreground, or for ground-based observations with satellites in the foreground assuming that detectors can be read out at sufficient speed. For wide Roman fields observed only once, this approach provides a reliable way to find and fit near-Earth asteroids and other fast-moving Solar system bodies, measuring both their brightness and trajectories.

  Speaker: Andreea Petric (STScI)
  Title: MIR Slitless Spectroscopy of Obscured AGN
  Abstract: We will present the first large-scale calibration and analysis of serendipitous James Webb Space Telescope MIRI Wide Field Slitless Spectroscopy (WFSS) observations obtained from publicly available archival MIRI LRS FULL-frame data. WFSS offers a powerful connection between imaging surveys and traditional spectroscopy, enabling efficient, multiplexed spectroscopic studies of statistically significant galaxy samples while reducing selection biases. Although dedicated MIRI WFSS observations are only starting in JWST Cycle 5, WFSS-like data have already been collected serendipitously since Cycle 1 in every MIRI LRS FULL-array observation, creating a rich yet largely unexplored archival resource. Using new JWST calibration pipeline capabilities and customized 1D spectral extraction, we present spectra from approximately 140 unique MIRI FULL pointings, with a particular focus on testing the current WFSS calibration. We then use these data to explore critical questions in Active Galactic Nuclei (AGN) science, including the surface density of nearby AGN detected serendipitously in MIRI WFSS observations, the census of warm molecular gas traced by the H2 S(5) and S(6) rotational transitions, and the relationship between mid-infrared slope, host galaxy properties, merger stage, and AGN contribution to the bolometric luminosity.