Two Talks

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Stars, Planets, and ISM Seminar

Two Talks

Wednesday, November 06, 2024, 12:00pm - 01:00pm

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Harriet Dinerstein, The University of Texas at Austin
JWST and IGRINS Observations of the Butterfly Nebula NGC 6302

Abstract

NGC 6302, also known as "The Butterfly Nebula," is the dramatic creation of an intermediate-mass star (about 5 solar masses) in the throes of expelling its outer layers and producing a remarkable bi-lobe, narrow-waisted planetary nebula (PN). It is unique among PNe in displaying a dark lane cutting through its center, as discovered by UT's own David Evans. It possesses an extremely hot central star (T > 200,000 K), absorption in the H I 21 cm line, a luminous infrared torus, and an obscured central star. Currently, it is copiously spewing both (O-rich) crystalline silicate dust and (C-rich) PAHs. I will show a few images from work in progress based on data from program JWST-GO-01742, as well as excerpts from a recent IGRINS-2 spectrum obtained during Science Verification on Gemini North that reveal the excitation and kinematics of H2 in the central regions.

Neal Evans, The University of Texas at Austin
The Outer Milky Way is a Laboratory for the Effects of Metallicity

Abstract

The Milky Way has a significant gradient in the abundance of metals, making the outer Galaxy an excellent laboratory to study the effects of lower metallicity. Values of Z (normalized to unity for the solar neighborhood) as low as 0.3 are known in HII regions in the outer Galaxy. Metallicity in the Galactic Center may be twice the local value. We are using this variation to study the effects of metallicity on disk fraction in clusters and on factors used to convert observations into mass. While gas to dust ratios and conversion factors from CO to mass and HCN to dense gas mass are usually taken to be constant, we find evidence for strong variations with Z and thus galactocentric radius. These variations affect estimates of masses of molecular and dense gas and predictions of star formation rates across the Galaxy. Studies in the Milky Way can inform analysis of other galaxies.

Location: PMA 15.216B and online