Tracing the Cosmic Web in the Far-Infrared Lines as it Builds Massive Galaxies

Cornell University, Ithaca NY

Investigators

Abstract

The Cornell team uses the far-infrared spectral lines of ionized carbon, nitrogen, and oxygen to trace star formation and galaxy assembly over cosmic time with emphasis on the redshift 1 to 4 epoch of peak star formation activity in the Universe, 7.7 to 12 billion years ago. These lines cool the gas and trace its physical conditions and reveal the surface temperatures and spatial distributions of the stars. With previous NSF awards graduate and undergraduate students designed and built the ZEUS and ZEUS-2 spectrometers used on large submillimeter telescopes. They discovered that at early times many of the most luminous dusty star forming galaxies formed up to 1000 stars per year in extended, multiple kiloparsec (kpc) sized "disks." They speculate that these enormous star forming disks are created and nourished by gas that is infalling from the Cosmic Web which contains much of the gas reservoir of the Universe. They plan to test this hypothesis by searching with their ZEUS-2 spectrometer for the inflowing gas in its C+ and N+ line emission at near million light-year scales. To discover this infalling gas is to confirm the major mode of galaxy and star formation during the epoch when most of the stars in today's Universe formed and to investigate the formation of the largest galaxies in today's Universe. Science will be publicly disseminated through teaching and outreach efforts including the K-12 programs like Focus for Teens and GRASSHOPR. Measurement of C+ and N+ line emission from large scale flows will be supplemented by O++ observations of the central galaxy. The three lines reveal the most massive stars on the main sequence and the ionizing flux and spatial extent of the stars. The project aims to reveal how galaxies build up their gas content which is converted into stars that evolve and die in supernovae that seed the intergalactic medium with metals. The ZEUS-2/APEX system is optimal for this work because of its surface brightness sensitivity and large field of view.