Kelly Lepo
And wrapping up my #AAS245 posts - Day 4
We started off the morning with Stella Offner's plenary Lecture: The Star Formation Engine.
Offner is part of the STARFORGE collaboration, which simulates the star formation process.
Star formation involves a lot of physics at a lot of scales — from gravity, magnetic fields, and turbulence that influence how gas collapses into stars, and stellar feedback processes that destroy the surrounding nebula.
Kelly Lepo
And the final talk of #AAS245 was the Berkeley Prize Lecture by Erik Tollerud, Clara Brasseur, and Kelle Cruz on Astropy.
In 2011, Tollerud was a grad student who wanted to write a unified library of astronomy packages. There were many astronomy packages, leading to duplicated work and incomparableness.
This somewhat naive desire started a discussion that eventually became the Astropy project.
Kelly Lepo
New telescopes coming online in the near future, including the Simons Observatory.
SPT and BICEP continue working together at the South Pole to look for fluctuations from the Big Bang.
Kelly Lepo
Plank covered the entire sky, but due to its smaller mirror, it has lower resolution.
Since they get 24 hours of darkness in the winter, SPT can take very deep images, but they only have access to the circumpolar sky.
In Chile, you can’t image as deeply, but you get access to more of the sky. So South Pole and Chilean telescopes complement each other.
Polarization measurements from SPT-3G are an independent way to determine the Hubble constant. It agrees with Plank measurements and disagrees with the local Universe measurements. The Hubble tension remains.
Kelly Lepo
Looking at the SPT data, we see point sources. This is washed out in the lower-resolution space-based Plank data.
Most of these points are quasars and are in known catalogs. However, there were some bright, dusty sources found with SPT that were not in any catalogs.
Follow-up observations with ALMA show these to be distant galaxies lens by a foreground galaxy into ring shapes. Spectra of the galaxies gives you a redshift from the CO line.
Kelly Lepo
The current generation of ground-based CMB telescopes operate from high, dry locations like the Atacama desert in Chile and the South Pole.
The South Pole telescope completed an upgrade to SPT-3G in 2017.
Kelly Lepo
Degree Angular Scale Interferometer at the South Pole made observations of the CMB power spectrum in 1999-2000, a measurement of the size of the fluctuations in the cosmic microwave background in the sky.
These results agreed with the Lambda CDM model of the universe and required the presence of dark matter. The next season they returned and got polarization measurements.
Kelly Lepo
One early project was to look for the Sunyaev-Zeldovich (SZ) effect, caused when background light from the Cosmic Microwave background scatters off of the hot gas in galaxy clusters.
Kelly Lepo
Next up the Heineman Prize Lecture at #AAS245 by John Carlstrom: Past, Present, and Future Cosmic Microwave Background Surveys.
I took an intro astronomy course from Carlstrom as an undergrad, so it was cool to see him up on the stage!
Kelly Lepo
Future work includes more work on galactic environments and trying to incorporate very tricky microphysics like astrochemistry into the simulations.
Kelly Lepo
By combining FIRE + STARFORGE codes, you can simulate star formation on galaxy scales, and then zoom all the way in to individual stars. It's super cool.
This way you can do things like check if the IMF changes with galactic distance. It seems like very close to the central black hole (within 0.5 pc), you might preferentially form massive stars.
Kelly Lepo
It can also create the correct distribution of binary stars with just turbulent fragmentation of the clouds of gas — meaning the stars have always formed a binary pair, they were not captured later.
STARFORGE also tells us that very small clouds will not form high-mass stars.
Kelly Lepo
The story of a star's life from its birth, to how long it lives, to how it eventually dies, is determined by its mass. Star-forming nebulas tend to make stars with a distribution of masses known as the Initial Mass Function (IMF).
STARFORGE can reproduce the observed IMF down to about 0.1 times the mass of the Sun.
Kelly Lepo
STARFORGE has my favorite videos of simulations of star-forming nebulas. The videos don't work well as screenshots, but you should really check them out.
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