SDSS Fourteenth Data Release

This post was written by Anne-Marie Weijmans, the SDSS Data Release Coordinator.


It’s the last day in July, and that means that it’s time again for a Sloan Digital Sky Survey (SDSS) data release! This year, we are very happy to announce our fourteenth public data release, DR14.

Making data publicly available is an important aspect of SDSS, as it allows SDSS data to be used world-wide by anyone with an internet connection. For more than a decade, SDSS data has been used by astronomers for their science, by teachers in their classrooms[1], by students for their school projects, and by the general public to learn more about the Universe. In order to have this broad impact, we work hard to not only make our data available, but to also ensure that it is accessible. All our data is thoroughly documented, and we have various tools, tutorials and examples to assist anyone interested in using our data — from professional astronomers to high school students. Just go to the SDSS data access website to find out how you can work with the SDSS data!

All the SDSS data are stored at the servers of the Center for High Performance Computing (CHPC), at the University of Utah. This particular server holds all the SDSS data releases, including DR14. Just DR14 alone is already a whopping 156 TeraBytes (TB = 1000 Gigabyte = 1012 bytes): that is more than 33,800 DVDs worth of data! Image credit: Adam Bolton

So, what is available in DR14?

  • APOGEE-2, or the APO Galaxy Evolution Experiment-2 is very proud to announce its first public data release! APOGEE-2 studies the structure of the Milky Way by taking infra-red spectra of stars, to learn more about how the Milky Way formed and evolved over time. You can explore these spectra using our webapp and find stellar parameters and chemical properties in the APOGEE-2 data release.
  • eBOSS, short for extended Baryon Oscillation Spectroscopic Survey, is also celebrating its first public data release! eBOSS is mapping the structure of the Universe, by taking optical spectra of distant galaxies and quasars. These spectra provide distance measurements to galaxies, quasars, and intervening gas, all of which enable eBOSS to make a 3D map of the Universe, and learn more about how galaxies cluster in space. Ultimately, eBOSS aims to precisely measure the expansion rate of the Universe, and reveal more about the nature of the mysterious Dark Energy that accelerates this expansion. The eBOSS spectra are also available in our webapp.
  • MaNGA or Mapping Nearby Galaxies at Apache Point Observatory already released its first data last year, but they’re back with even more data cubes, 2,812 in total! MaNGA uses integral-field spectroscopy to map the properties of galaxies, and find out more about how different galaxies form and evolve. The MaNGA team has prepared a very handy set of tutorials to explain the data cube format, so that anyone can make use of the wealth of information hidden in these galaxy integral-field spectra.

Finally, we’re also very excited to share our new Image Policy with you! We have updated our image license to a Creative Commons Attribution license (CC-BY), which means that any image on our website may now be downloaded, linked to, or otherwise used for any purpose, provided that the image credits are given.

We hope you’ll have fun with all the spectra, catalogs, and tools included in our Fourteenth Data Release, and that they will help you with your science, outreach, teaching, school projects, and anything else!

Anne-Marie Weijmans

SDSS Data Release Coordinator

University of St Andrews

[1] If you are a teacher, we invite you to check out our latest educational guides and activities at SDSS Voyages! We are also developing a Spanish version, available here.

SDSS Summer Interns Apply SDSS Science to Small Telescopes

By Kate Meredith.  Kate is the Director of Education Outreach at the University of Chicago Yerkes Observatory.  Kate began working with SDSS data while still a high school science teacher and continued that work in her role with SDSS as lead educator for formal education.  She is the primary developer of the SDSS Voyages website.  In her first year as Education Director at Yerkes, Kate launched a summer intern program.  In this post, Kate describes one of the projects interns lead during the summer of 2016.  

Rebecca Chen and Lindsay Berkhout are sophomore physics majors at the University of Chicago. Both chose the astronomy specialization, and both spent the summer of 2016 as interns at Yerkes Observatory . They were two of the 12 undergraduates that helped launch the first ever Yerkes Education Outreach internship program.  Their goal was to take precise photometric measurements of targets (how bright objects are) with instruments including the 24-inch telescope at Yerkes, as well as Stone Edge Observatory’s 20-inch telescope, located in Sonoma, California.

Rebecca Chen positioning new SDSS filters for use with the 24 inch reflecting telescope at Yerkes Observatory.

“We both came in, and we didn’t know anything,” Berkhout laughs. But they soon got up to speed, and ended the summer with a tested methodology that allows not only them, but students following in their footsteps, to use the telescopes to measure the brightness of objects to within 5% the value obtained by the venerable Sloan Digital Sky Survey (SDSS).

The long-term goal on Yerkes’ side is to be able to extend SDSS catalog to bright stars. The survey, designed to measure many faint targets, has gaps when it comes to measuring the brightest stars. But the Yerkes and Stone Edge telescopes—large for small observatories, but tiny compared to SDSS’ 100-inch mirror—can tackle the bright stars with ease. The trick is being able to compare data using the very different instruments of SDSS and the observatory telescopes.Chen and Berkhout were interested in more dramatic events; they wanted to measure the lightcurves of recent supernovae. But both projects rely on being able to precisely measure the brightness of targets. And figuring out how to reliably attain such precision with the Stone Edge and Yerkes telescopes became the students’ summer objective.

Richard Kron, a professor at the University of Chicago and former director of Yerkes Observatory, worked closely with the students. But he says he was mostly there to answer their technical questions, and let them guide the direction of the work themselves—something Chen and Berkhout handled with aplomb, though he notes that other students might desire a more hands-on approach to mentoring.

He introduced the pair to software packages—Aperture Photometry Tool and Topcat—to help them in their work, and advised on details such as calculating uncertainty in their measurements. He admits that his first instinct is often to push through and rush to big results. And students likewise often want to do something novel and exciting—like observing supernovae.

Intern Lindsay Berkhout installs SDSS filters in CCD camera at Yerkes Observatory.

But Kron says it’s important to remember how much time new students take to assimilate the big concepts at play: operating the telescopes, learning new software routines, finding and measuring the targets, understanding uncertainty. “Make sure the student feels really in command,” he suggests. “It’s okay if you don’t cover quite as much as your original dreams had suggested.”

“There’s still a lot of work to do,” Berkhout acknowledges. Steep learning curves, but also telescope downtime, contributed to the sometimes slow pace. “The next step is actually taking data and using this methodology to get results,” she says, something they ran out of time for in the short summer.  “I think that if someone else takes the project they could go wherever they want with it, whether it’s bright stars or variable stars, or supernovae.”
Berkhout and Chen left behind a detailed guide of the work they did, summarizing the technical details of how to take observations, run them through the software, measure sources’ photometry, and compare it to SDSS values. They also left suggestions for ways future interns might improve from 5% down to within 2% of the SDSS values. And they took with them many more lessons in how to plan and tackle such a project.

“I felt like it was a really nice internship for summer after first year,” Berkhout says. “It was a good way to get involved in a research project that taught us a lot so now we can go to other people and be able to say that we’ve done something. That we learned a lot and we’re competent and can be involved in bigger research projects in the future.”

Chen reflects that, “While we were working it was frustrating, because at times it felt like we weren’t getting anywhere. But at the end of the summer, looking back on all the things we had done, I was like, ‘Oh that’s pretty cool. That’s a project. We did a real project.’”

 

Rebecca Chen and Yerkes Director of Education and SDSS EPO Specialist, Kate Meredith, celebrate the first successful night of observing with the new SDSS filters and several hundred mosquitos at Yerkes Observatory.