Mapping the Universe With radio galaxies and quasars

Question for the day: What is the physical significance of the Hubble Constant? V = Hd

The further out we look (higher redshift), the further back in time we look

Observations of quasars and radio galaxies allow us to look out billions of light years into space NVSS survey of the sky at radio wavelengths found 1.8 million sources, almost all of which are radio galaxies and quasars The Sloan Digital Sky Survey (SDSS) measured positions, brightness, and spectra (therefore distances) of 675,000 galaxies and 90,000 quasars What do we see? What is the shape of the universe as a whole?

Giant telescopes can see out to redshifts of 5 and beyond

Humanity’s deepest view into space: the Hubble Deep Field Faintest objects are apparently “galaxy bits”

Galactic filaments and voids Figure 25.29 from book

Why are there filaments and voids in the distribution of galaxies?

Back to galaxies: the rotation curves of spiral galaxies show that most of the mass is in an unknown form of matter The further we go out in the universe, the more compelling the evidence for Dark Matter

Clusters of galaxies: galaxies + superhot gas + ? Galaxies are moving around, subject to a gravitational force far greater than the galaxies can produce

Dark Matter manifests itself by trapping hot gas and causing gravitational lensing

Nature even “separates out” Dark Matter when clusters of galaxies collide

Dark Matter and galaxies Dark matter dominates the stars in galaxies Galaxies move according to a gravitational force determined by the dark matter We believe the filaments of galaxies occur because galaxies “trace out” the distribution of dark matter