diskcol2.gif (389412 bytes)As galaxies assemble through collisions and mergers, they grow bulges and activate supermassive black holes in their nuclei, creating active galaxy nuclei. MIRI can probe obscured active galactic nuclei to determine the evolution of supermassive black holes in the heyday of quasars at redshifts of z ~ 2 - 2.5. (galaxy merger simulation by C. Mihos)

 

 

Perhaps 90% of the high redshift AGNs are heavily obscured (e.g. Gilli et al. 2000) Understanding AGN evolution requires understanding this dominant population, which can be identified from deep X-ray images with Chandra and XMM-Newton:

wpe6.jpg (76067 bytes)

The Ne VI line at 7.65 microns allows measure of power of obscured AGNs. This line requires ultraviolet photons of very high energy to be excited, too high an energy to be produced by stars. The extinction at this line is less than 2% of the extinction in the visible. The line is in the MIRI spectral range to z ~ 2.5. 

The following spectrum obtained with the short wavelength spectrometer on ISO shows this strong line because the Circinus galaxy is the site of an obscured active nucleus.

wpe8.jpg (27358 bytes)

Even at a redshift of 2.5, the line is readily measurable to a luminosity of only twice that of the nearby obscured moderately luminous active nucleus in NGC 1068.

In addition, MIRI H alpha measurements can measure star formation rates in very young galaxies. A rate of 10 solar masses per year can be readily detected at a redshift of z ~ 10.