Special Talk

• Special Talks

  Speaker: Jayashree Behera (STScI)
  Title: Joint Multiband Photometry with Crowdsource
  Abstract: Modern astronomical surveys routinely observe the sky in multiple wavelength bands, providing complementary views of the same astrophysical sources. However, crowded-field photometry is often performed independently in each band, even though the underlying sources occupy the same positions on the sky. This can lead to inconsistencies in source detection, photometric measurements, and astrometric solutions, particularly in dense stellar fields where blending is severe. Jointly analyzing imaging data across multiple bands offers an opportunity to improve both source recovery and measurement precision by leveraging all available information simultaneously. In this talk, I will present a new multiband extension to the crowdsource photometric pipeline that performs source detection and fitting across multiple images while enforcing a common source-position model and allowing fluxes to vary between bands. Using WISE W1 and W2 imaging as a case study, I will discuss the impact of multiband fitting on source detection, photometric consistency, and astrometric stability in both sparse and crowded regions. These results illustrate the advantages of multiband crowded-field photometry and its potential for future large-scale survey catalogs.

  Speaker: Jack Neustadt (JHU)
  Title: Kinematic Stratification in Extremely Red Quasars Revealed by JWST
  Abstract: We analyze the spectra of the central nuclei of extremely red quasars (ERQs) observed as part of the JWST ERS Q3D program. We focus on the complex kinematic structures of the prominent rest-frame optical emission lines. Our modeling allows us to deblend the lines and separate the emission into distinct kinematic components that imply velocity- and density-stratified gas structures on a range of physical scales within the ERQs. Supplementing the JWST data with archival data, we analyze the spectral energy distributions (SEDs) of the ERQs and find they are consistent with a significantly dust-obscured central source with a small amount of relatively-unobscured UV/optical flux that is scattered into our line-of-sight. While the kinematics of the UV and optical emission lines largely agree, the UV lines are dominated by scattered light. In contrast, the optical emission-line ratios indicate a combination of scattered and obscured emission. Our analysis focuses on one ERQ, J0834, because its distinct spectroscopic features allow the emission to be easily decomposed into separate kinematic components.

  Speaker: Sanjib Sharma (STScI)
  Title: Age, Chemistry, Structure and Kinematics of the Inner Galaxy: Results from MUSE and Possibilities with Roman
  Abstract: Understanding the inner Galaxy is important for multiple reasons. It is the oldest component of the Milky Way disc, it has a complex structure and formation history and contains a significant fraction of the Milky Way’s stellar mass. However, the inner Galaxy is also one of the most poorly understood regions of the Milky Way. This is because stars in the Inner Galaxy are faint, crowded, and have high extinction, which makes it difficult to observe them. Using the integral-field spectrograph MUSE with adaptive-optics on the Very Large Telescope, we overcome some of the observational limitations and measure accurate ages, chemical abundances, and line-of-sight velocities for a sample of 98 main-sequence turn-off and subgiant branch stars. We discuss the science implications of these results and compare and contrast them with previous measurements and with theoretical models of the Milky Way. We briefly discuss prospects of studying the inner Galaxy with Roman.