FLASH Talks: Commissioning JWST: From Launch to Functional Observatory & Discovery of Anomalous Flux in the Cosmic Optical Background

Friday, 18 February 2022 noon — 1 p.m. MST

Marcia Rieke (UofA) & Tod Lauer (NOIRLab)
Marcia Rieke, Steward Observatory
Commissioning JWST:  From Launch to Functional Observatory
We are a quarter of the way through the six-month commissioning period for Webb with a number of key milestones already successfully passed. I will review the work so far, and outline what will be happening from now until the end of Commissioning in June.  So far, everything is pointing towards meeting performance goals so observing can proceed as planned, but several of the instruments have yet to be completely turned on.
Tod Lauer, NOIRLab
Discovery of Anomalous Flux in the Cosmic Optical Background
We used New Horizons LORRI images to measure the optical-band sky-brightness within a high galactic-latitude field selected to have minimal foreground emission. This allows direct measurement of the cosmic optical background (COB), and provides much smaller errors than our earlier work based on New Horizons archival observations. The images were obtained when New Horizons was 51.3 AU from the Sun, and are completely free of the zodiacal light foreground, which strongly interferes with COB measurements done from the inner solar system. Isolating the COB contribution to the raw total sky still required subtracting scattered light from bright stars and galaxies, faint stars below the photometric detection-limit within the field, Milky Way starlight scattered by IR-cirrus, and the hydrogen plus ionized-helium two-photon continuum. This yielded a highly significant detection of the COB at 16.37 ±1.47 nW m−2 sr−1 at the LORRI pivot wavelength of 0.608 μm. This result is in strong tension with the hypothesis that the COB only comprises the integrated light of external galaxies (IGL) presently known from deep HST counts. Subtraction of the estimated IGL flux from the total COB level leaves a flux component of unknown origin at 8.06 ±1.92 nW m−2 sr−1. Its amplitude is equal to the IGL.
FLASH Talks are scientific talks for the staff at NOIRLab and the University of Arizona's Steward Observatory. 
If you or a collaborator are interested in presenting at FLASH please get in touch. All FLASH talks are virtual for the foreseeable future, so feel free to suggest speakers from outside of Tucson!