IFUs in the Webb Era

Workshop Report

Tracy Beck, tbeck@stsci.edu, and Linda Smith, lsmith@stsci.edu

Each image from the Hubble Space Telescope provides a wealth of knowledge about the spatial distribution of light in an astronomical scene. Now, imagine every distinct region in a Hubble image is accompanied by a spectrum that provides additional information on the motion, composition, or physical state of the source region. Such integral-field spectroscopy (IFS) is precisely what the 3D data from an integral-field unit (IFU) provides! Today, IFU-type instruments are common and in use at many ground-based observatories. The next generation of large telescopes—both on the ground and in space—will include IFUs in their instruments, including NIRSpec and MIRI on the James Webb Space Telescope, and first-generation instruments for the European Extremely Large Telescope and the Thirty Meter Telescope. IFUs have come of age.

In late October 2010, the Institute hosted a timely workshop entitled “IFUs in the Era of JWST.” It was the first major international conference on IFS in the U.S. in the last decade, and more than 60 astronomers from four continents attended. The workshop offered three days of presentations and discussions of IFS techniques, progress in instrument development, discussion of 3D data viewing and analysis—and new scientific results. The workshop consisted of more than 40 talks from experts in the IFS community. Highlights include:

  • Roger Davies (U. Oxford) presented a global overview of IFU capabilities, and showed how IFS observations are reshaping our thoughts about elliptical (E) and lenticular (S0) galaxies. Studies with 3D IFS have revealed that early-type galaxies exhibit distinct large-scale motion, whereas astronomers had expected velocity distributions dominated by random motion. Furthermore, many weakly rotating E/S0 galaxies exhibit kinematically decoupled cores—regions with unique, sharply differentiated motion—which imply past merger activity in the systems.
  • Natasha Forster-Schreiber (Max-Planck-Institut für Astrophysik) gave the regular Institute colloquium the week of the IFU workshop—a talk entitled “The Growth of Galaxies at z ~ 2: Insights from IFU Surveys.” She presented results from the Spectroscopic Imaging Survey in the Near-infrared with SINFONI (SINS) galaxy survey. SINFONI is an IFS instrument on the Very Large Telescope of the European Southern Observatory. Her research suggests that the majority of galaxies at z ~ 2 are large, rotating, and often gas-rich disks. Insights into these systems are improving our understanding of how massive galaxies gain mass over cosmic time.
  • Torsten Böker (ESA), who is NIRSpec deputy project scientist and a member of the MIRI instrument science team, presented the specifications for the NIRSpec and MIRI IFUs on Webb. MIRI will always acquire medium-resolution spectroscopy with  the IFU. The IFS capabilities with Webb should reveal the motions and physical conditions in galaxies with unprecedented sensitivity, and help us better understand how galaxies formed in the early universe.
  • James Larkin (UCLA) gave an overview of IFS capabilities planned for the next era of large ground-based telescopes, and highlighted the IFS instrument that his team plans to build for the Thirty Meter Telescope.

During group discussions on viewing and analyzing IFS data, participants expressed a variety of opinions. This diversity reflects the wide range of science applications for IFS, as well as the complexity of IFS data structures. Researchers are still experimenting with optimal methods, and hope that commonly used tools will emerge.

Archived versions of all the presentations at this workshop are available from the archive link for the week of Oct. 25, 2010.

Additional information about IFS is available at the community IFS wiki page.