1. Finding the Most Luminous Galaxy Developed by the WISE team 0 Topic: Galaxies Concepts: Galaxies, black holes, early universe, infrared studies Mission: WISE Coordinated by: the NASA Astrophysics Forum An Instructor’s Guide for using the slide sets is available at the ASP website https://www.astrosociety.org/e ducation/resources-for-the- higher-education-audience/ https://www.astrosociety.org/e ducation/resources-for-the- higher-education-audience/

2. The Discovery 1 Artist’s conception of the current record holder for most luminous galaxy in the universe: WISE 2246-0526. Credit: NASA/JPL-Caltech. Inset image: A combined mutiwavelength image of the galaxy and two faint companions (NW and SE). Blue is HST ultraviolet emission, red is ALMA radio emission of ionized carbon, green is ALMA radio emission from dust. In data from the Wide-field Infrared Survey Explorer (WISE) scientists have discovered the current record-holder for most luminous galaxy in the universe, designated WISE 2246-0526. It shines with a power equivalent to more than 300 trillion suns, the brightest of a newly-identified class of extremely luminous galaxies shining early in the history of the cosmos.

3. How was the Discovery Made? 2 The ELIRGs also have high redshifts. This indicates these galaxies are very far away and are observed as they were very early in the history of the universe. The light from WISE 2246-0526 has traveled 12.5 billion light years from a time when the universe was only about 10% of its present age. Artist’s conception of WISE in space. Credit: NASA/JPL-Caltech. The WISE spacecraft surveyed the sky in infrared light, creating an extensive catalog of infrared- emitting sources. Scientists studying these sources identified a group of 20 “extremely luminous infrared galaxies” (ELIRGs) shining in infrared light with brightness equivalent to more than 100 trillion suns--including WISE 2246-0526.

4. The Big Picture 3 Galaxies with high luminosity are usually powered by supermassive black holes in their cores. These black holes accrete matter into disks that become superheated as the matter spirals into the black holes, releasing vast amounts of energy. ELIRGs may be the result of galaxy mergers in which the central black holes combine, clouds of dust and gas collide and fall into the new black hole, and great energy is released. Artist’s conception of a supermassive black hole and its hot accretion disk at the center of a galaxy. Credit: NASA/JPL- Caltech. The cores of these galaxies are obscured by dust. The tremendous energy from the central black hole heats the dust, and the hot dust emits the infrared light that WISE recorded.

5. What are the Implications? 4 The discovery provides insight into a major growth stage for the supermassive black holes at the centers of these young galaxies. These ELIRGs appear to be producing so much energy that their black holes must already be very massive. They appear to be accreting matter faster than normally thought possible--because the very high energy should start to drive away the matter falling in. Scientists think that chaotic environments in these galaxies may produce slowly spinning black holes. Slow spinners generate less energy per unit mass accreted, allowing them to grow much more quickly than fast spinners. These massive black holes might thus produce the incredibly powerful emissions. The Hubble Ultra Deep Field shows 10,000 galaxies, including many whose light comes from the early days of the universe and helps scientists understand those earlier eras. Credit: NASA/ESA/S. Beckwith and the HUDF Team.

6. Resources 5 Paper: http://adsabs.harvard.edu/abs/2015ApJ...805…90T ( Chao-Wei Tsai et al.) http://arxiv.org/abs/1410.1751http://arxiv.org/abs/1410.1751 ( Chao-Wei Tsai et al.) Related Papers: http://adsabs.harvard.edu/abs/2015ApJ...804...27Ahttp://adsabs.harvard.edu/abs/2015ApJ...804...27A (Roberto Assef et al.) http://arxiv.org/abs/1408.1092 http://iopscience.iop.org/article/10.3847/2041-8205/816/1/L6/pdfhttp://iopscience.iop.org/article/10.3847/2041-8205/816/1/L6/pdf (T. Diaz- Santos et al.) http://arxiv.org/abs/1511.04079 Press Releases: http://www.nasa.gov/press-release/nasas-wise-spacecraft-discovers-most- luminous-galaxy-in-universe http://www.nasa.gov/feature/jpl/wise/most-luminous-galaxy-is-ripping-itself- apart

7. Finding the Most Luminous Galaxy BONUS CONTENT 6

8. ALMA Update The finding indicates that so much energy is being produced in the accretion disk surrounding the central supermassive black hole that it is disturbing the entire galaxy. Normally, gas will flow away in specific directions; this is the first time such a turbulent outflow has been seen across an entire galaxy. If this energetic galaxy eventually blows away all of its gas and dust, we could see the bright accretion disk surrounding its black hole core—what scientists call a quasar. 7 New artist’s conception of galaxy WISE 2246-0526 expelling turbulent gas. Credit: NRAO/AUI/NSF; Dana Berry / SkyWorks; ALMA (ESO/NAOJ/NRAO). Other instruments have subsequently studied this “most luminous” galaxy. Scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile have recently discovered that it is expelling turbulent gas in all directions.

9. WISE to NEOWISE The WISE spacecraft made a complete survey of the sky at four infrared wavelengths in 2010, taking almost 1.5 million sets of images in the four bands and creating a catalog of over 560 million objects. Its instrument was cryogenically cooled to to prevent the spacecraft from picking up its own infrared (heat) signature. When the cryogen was depleted, the mission continued to search for asteroids for four months, completing a second full survey of the sky in two of its infrared bands before the spacecraft was put into hibernation. 8 Asteroid 872 Hilda tracked by NEOWISE, seen as a series of orange dots revealing its motion over time. Credit: NASA/JPL-Caltech. In 2013, the spacecraft was switched back on specifically to search for and track “Near-Earth Objects” or NEOs– asteroids whose orbits bring them close to the orbit of Earth and which may one day pose a risk of collision. The new NEOWISE mission helps to increase understanding of the asteroids and comets it studies and tracks, and helps to refine concepts for future NEO cataloging missions.