Wrangler Supercomputer Speeds through Big Data

Data-intensive supercomputer brings new users to high performance computing for science

Published on March 10, 2016 by Jorge Salazar

Dark Energy of a Million Galaxies

UT Austin astronomer Steven Finkelstein eyes Wrangler supercomputer for HETDEX extragalactic survey

A million galaxies far, far away are predicted to be discovered before the year 2020 thanks to a monumental mapping of the night sky in search of a mysterious force. That's according to scientists working on HETDEX, the Hobby-Eberly Telescope Dark Energy Experiment. They're going to transform the big data from galaxy spectra billions of light-years away into meaningful discoveries with the help of the Wrangler data-intensive supercomputer.

"You can imagine that would require an immense amount of computing storage and computing power. It was a natural match for us and TACC to be able to make use of these resources," Steven Finkelstein said. Finkelstein is an assistant professor in the Department of Astronomy at The University of Texas at Austin (UT Austin). He's one of the lead scientists working on HETDEX.

Steven Finkelstein

Steven Finkelstein, Department of Astronomy, UT Austin.

"HETDEX is one of the largest galaxy surveys that has ever been done," Finkelstein said.

Starting in late 2016, thousands of new galaxies will be detected each night by the Hobby-Eberly Telescope at the McDonald Observatory in West Texas. It will study them using an instrument called VIRUS, the Visible Integral Field Replicable Unit Spectrograph. VIRUS takes starlight from distant galaxies and splits the light into its component colors like a prism does.

"With that, we can scan a very large region of the sky and do spectroscopy to discover thousands of galaxies at once," Finkelstein said. "Not only will we find them, but because we're splitting the light up we'll be able to measure the distance to them instantaneously."

That's because light from objects that move away from us appears red-shifted, and the amount of redshift tells astronomers how fast they're moving away. The faster they move away, the farther away they are. That relationship between speed and distance, called Hubble's Law, will pin down a galaxy's location and let astronomers create a 3D map of a million galaxies with HETDEX.

"The main goal with this map is to study dark energy," Finkelstein said.

Dark energy remains a mystery to science, its presence today undetectable except for its effect on entire galaxies. Basically, galaxies are being pushed apart from each other faster than predicted by science. So astronomers have labeled that mysterious push 'dark energy.' Dark energy's push is so strong that scientists estimate 70 percent of all the energy in the universe is dark energy.

"What we're trying to do is measure how strong dark energy is at some point in the distant past," explained Finkelstein. HETDEX scientists will do this by mapping Lyman-Alpha emitting galaxies, which Finkelstein explained means they're forming stars in the universe at a time 10 billion years in the past.

Hobby-Eberly Telescope

The Hobby-Eberly Telescope will collect 200 gigabytes of galaxy spectra data each night for three years, which will be preserved and analyzed on the Wrangler data-intensive supercomputer. Credit: Ethan Tweedie Photography.

Hobby-Eberly Telescope

The Hobby-Eberly Telescope Dark Energy Experiment will discover and map a million galaxies by 2020 in an effort to understand the mysterious force scientists call dark energy. Credit: Ethan Tweedie Photography.

"By doing this observation, we can rule out many, many models that say either the strength of dark energy stays the same or it evolves, simply by doing this measurement and seeing whether it evolves," Finkelstein said. They'll do this by measuring the positions of a million galaxies and comparing them to to a model for how strong dark energy is.

"Data is really the biggest challenge with our project," Finkelstein said.

Over the course of three years, he and colleagues will collect about 200 gigabytes of telescope data each night, the spectra of 34,000 points of starlight snapped every six minutes. "Our primary goal is that every time an image is taken, these 34,000 spectra, while the next image is being taken, that previous image is being transferred of to the Texas Advanced Computing Center onto Wrangler. By the time the next image is done, it's ready to start transferring that image while it's taking the next one," Finkelstein said.

Wrangler will also handle the processing of the spectral data from HETDEX to transform the night sky snapshots into galaxy positions and distances. Part of that processing will be calibration of the focal plane of the telescope's camera. And Finkelstein said they'll use a software package aptly named Cure to take all the raw telescope data and yield a list of galaxies.

"Every morning, we should wake up and come into the office and have an email that says, 'here are the 3,000-4,000 galaxies we discovered last night. Here's where they are in the sky. Here's their distances. Now go study dark energy if you want to,'" Finkelstein said.

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