JWST OPENS A NEW ERA IN ASTROCHEMISTRY

Oka, Takeshi

Permalink

https://hdl.handle.net/2142/122423 Copy

Description

Title

JWST OPENS A NEW ERA IN ASTROCHEMISTRY

Author(s)

Oka, Takeshi

Issue Date

2023-06-20

Keyword(s)

Mini-symposium: Infrared Spectroscopy in the JWST Era

Abstract

Historical sketch: Charlie Townes and I are the only two astronomical spectroscopists who switched to infrared after a few years of radio astronomy. Townes did atomic spectroscopy and discovered the black hole at the center of the Galaxy.ᵃ I switched because H⁺, central in astrochemistry, has a spectrum only in the infrared region. Dense and diffuse clouds: It took us 16 years to observe the spectrum of H⁺ in dense cloudsᵇ as theoretically predicted by Herbst and Klemperer and Watson, but had we tried diffuse clouds in the Galactic center we would have found it within a few years. Radio (ALMA) astronomy is for emission spectroscopy in dense clouds while infrared (JWST) spectroscopy is for absorption spectroscopy in diffuse clouds. Molecules of interest: So far astrochemistry has been mostly the science of dense clouds, but JWST will bring in rich chemistry in diffuse clouds. Dense clouds are localized. Diffuse clouds give a bigger picture. Patrick Thaddeus said, “One should not look at an elephant with a magnifying glass”. Spectra of the following molecules will be observed: HD, CH, NH, OH, HD⁺, CH⁺, NH⁺, OH⁺, H⁺, H₂D⁺, CH₂, NH₂, H₂O, CH⁺, NH⁺, H₂O⁺. These are the kind of molecules observed by the Herschel Observatory. Many of them were analyzed as in dense clouds, but they are all in diffuse clouds. Apart from H⁺ they are all polar molecules with high rotational constants therefore the spectrum is composed of 1 line apart from fine and hyperfine structure. For H⁺ three rotational levels (J,K) = (1,1), (1,0), and (3,3) levels are populated. Stars of interest: Absorption spectroscopy needs bright and young stars with a smooth continuum for the radiation source. Ben McCall found 27 stars that are usable to conduct absorption spectroscopy toward the Galactic disk. We found 18 stars toward the Galactic center. These stars will be useful for the JWST observation.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

Text

Language

eng

Handle URL

https://hdl.handle.net/2142/122423

DOI

https://doi.org/10.15278/isms.2023.6714

Owning Collections