Special Talk

• Special Talks

  Speaker: Amrita Singh (STScI)
  Title: SDSS-V Local Volume Mapper's Lagoon nebula: Addressing the abundance discrepancy problem  
  Abstract: The Sloan Digital Sky Survey V (SDSS-V) Local Volume Mapper (LVM) is an ultra-wide integral-field spectroscopic survey of the Milky Way and the local volume galaxies. The LVM's spatially resolved spectroscopy covers the full optical range (3600-9800 Å) at medium spectral resolution (R ∼ 4000) and maps the disks of the galaxy at extremely high physical spatial resolution (e.g., < 1 pc in the MW and ∼ 10 pc in the Magellanic Clouds). The LVM covers the entire Lagoon Nebula (M8) in 10 pointings, each with an exposure time of 2*900 secs, at a spatial resolution of ∼ 0.22 pc/spaxel. We have detected good signal-to-noise ratio measurements of (a) more than half a dozen metal Recombination Lines (RLs) of oxygen and carbon, (b) HI and HeI RLs, (c) and nebular and auroral Collisional Excited Lines (CELs). These lines enable us to thoroughly examine the physical conditions, including Te, ne, ionic and elemental abundances of the ionized gas, as well as delve into the intricate internal physics of the gas. We focus on the chemical abundance measurements from metal RL diagnostics and direct method chemical abundance measurements through CEL diagnostics. As a result, the differences in abundances computed from metal RLs and CELs within the internal structures of the nebula can be measured, allowing us to measure the magnitude of the ADF in different parts of the nebula and study whether the ADF depends on location and other properties of the ionized gas, like the electron temperature.

  Speaker: Kalina Nedkova (STScI)
  Title: UVCANDELS: What drives the differences between UV and optical sizes of disk galaxies?
  Abstract: Using high-resolution imaging from UVCANDELS, we show that massive disk galaxies (>10^10 Msun) are typically much larger in the rest-frame UV than optical. To understand if this difference is driven by dust or inside-out growth, we use the VELA simulations. When dust is included, these simulations reproduce observations; however, when the effects of dust are removed, the difference between the rest-frame UV and optical sizes of disk galaxies is consistent with zero. Since dust alone can account for differences between the rest-frame UV and optical sizes of star-forming galaxies, we find that variations in galaxy size with wavelength do not constitute evidence for specific galaxy growth scenarios. With JWST, sizes are now being obtained for large samples of high-redshift galaxies. Understanding the effects of dust will allow us to constrain how the earliest galaxies build up their stellar mass.

  Speaker: Daniel Maschmann (STScI)
  Title: Star Clusters in Nearby Galaxies with PHANGS-HST and -JWST
  Abstract: With the PHANGS-HST treasury program, the statistical power in star cluster research was significantly elevated. We now start to discover the possibilities with new JWST observations what we can learn about the different evolutionary stages across cosmic time.

  Speaker: Qiushi (Chris) Tian (JHU)
  Title: Nebular Properties of Stellar Associations in Nearby Galaxies with PHANGS-HST and JWST
  Abstract: The PHANGS-HST multi-scale stellar association catalogs trace young star-forming regions across size scales from 8 pc to 64 pc. Leveraging newly obtained narrowband data in H-α from HST and Paschen-α from JWST, we aim to provide more accurate information on dust extinction and star formation. Specifically, it is traditionally challenging to determine the age of young star formation regions, where H-α and Paschen-α emission data can prove most helpful. We demonstrate the potential of these narrowband data on NGC 4826, measuring its stellar association regions’ luminosities and equivalent widths. We compare the calculated dust extinction and SFR from narrowband data to SED fitting results from broadband data, linking them to spatial structures and distributions within the galaxy.