Fig. 13.1 . The intensity of the cosmic microwave background radiation plotted as a function of wavelength. This thermal radiation was formed about 390,000 years after the big bang, which occurred about 13.7 billion years ago. The observed radiation has a nearly perfect blackbody spectrum. Pioneering measurements by Arno A. Penzias (1933? ) and Robert W. Wilson (1936? ) in 1965 and Peter G. Roll (1935? ) and David T. Wilkinson (1935?2002) in 1966, at 7.35 cm and 3.0 cm wavelength respectively, are compared to the expected spectrum of a three-degree blackbody and radiation from our Galaxy (bottom). The full spectrum at millimeter wavelengths (top) was obtained from instruments aboard the COsmic Background Explorer, abbreviated COBE, in late 1989. This data is so accurate that the error bars of the individual points all lie within the width of the plot curve. This solid line, which matches the shape and peak location of the observed data, corresponds to a thermal radiator, or blackbody, with a temperature of 2.725 K.
Fig. 13.2 . An all-sky view of the three-degree cosmic microwave background radiation emitted from the universe in its infancy, just 390,000 years after the big bang that occurred 13.7 billion years ago. The data, taken in 2003 from the Wilkinson Microwave Anisotropy Probe, or WMAP for short, are shown here after seven-years of data analysis. The temperature fluctuations range up to 0.0002 K above and below the average value. Darker regions are cooler and lighter ones are hotter. These temperature fluctuations provided the seeds from which galaxies subsequently grew. (Courtesy of the NASA/COBE and NASA/WMAP Science Teams.)
Fig. 13.3 . The angular fluctuation strength, or power, of the cosmic microwave background radiation in which temperature fluctuations, in units of square micro kelvin (10-6 K and designated mK), are displayed as a function of their angular extent in degrees, denoted o. This plot shows the relative brightness for the all-sky map observed from the Wilkinson Microwave Anisotropy Probe, abbreviated WMAP (see Fig. 13.2) at various sizes. The solid line is the model that best fits the observed data (solid dots), and the gray band represents uncertainties in the model. Anisotropy data obtained by previous experiments are denoted by dots with error bars. The observed power spectrum has been compared to other astronomical observations and different theoretical models, providing estimates for the amount of dark matter and dark energy in the universe. (Courtesy of the NASA/WMAP Science Team.)
Fig. 13.4 . Two spiral galaxies (left), each represented by M 81, can merge to form an elliptical galaxy. A pair of colliding galaxies (right), designated NGC 6240, illustrates such a merger just before becoming a single larger galaxy. The prolonged violent collision has drastically altered the shape of both galaxies and created large amounts of heat and infrared radiation. All of these images have been taken with the infrared camera aboard the Spitzer Space Telescope, with the inclusion of optically visible data for M81 taken from the Hubble Space Telescope. (Courtesy on NASA/JPL-Caltech/U. Az./CfA/NOAO/AURA/NSF (left) and NASA/JPL-Caltech/STScI-ESA (right).]
Fig. 13.5 . The star formation rate, in solar masses per year per cubic Megaparsec or Mť yr-1 Mpc-3, plotted as a function of redshift, z (bottom axis) and time since the beginning of the expanding universe (top axis), in units of 109 years, or a billion years and a Gyr. The rate of star formation peaked at a redshift of about 3, or roughly 2 billion years after the expansion began, and this rate has subsequently decreased as gravitation has pulled more material into stars.
Fig. 13.6 . A negative print of the optically visible hydrogen emission from the Seyfert galaxy NGC 1275. (Courtesy of KPNO.)
Fig. 13.7 . The radio galaxy Cygnus A, listed as 3C 405 in the third Cambridge catalogue of bright radio sources, which has a radio output a million times more powerful than the radio emission of a normal galaxy like the Milky Way. This radio image, taken with the Very Large Array at a wavelength of 6 cm with a field of view of 0.038 x 0.022 degrees, shows two narrow, straight radio-emitting jets of particles that protrude in opposite directions from a giant elliptical galaxy at the center. The redshift of the optically visible elliptical indicates a distance of about 780 million light-years, and a linear extent for the radio galaxy of about a million light-years from end to end. The radio jets have probably been ejected along the rotation axis of a super-massive black hole located within a central elliptical galaxy. It must have been active for tens of millions of years to produce the two radio lobes. (Courtesy of NRAO/AUI/NSF.)
Fig. 13.8 . The bright radio source Virgo A, also designated 3C 274, coincides with M 87, a giant elliptical galaxy located at a distance of about 56.8 million light-years. M 87 is the largest and brightest galaxy within the Virgo cluster of galaxies. The core of M 87 contains a super-massive black hole of about 3 billion solar masses, which is a thousand times more massive than the black hole at the center of our Milky Way Galaxy. This radio map, made with the Very Large Array, shows two elongated lobes, one on either side of the center of M 87, apparently fed by the super-massive black hole. The most intense radio emission comes from a jet that emerges from the core of the galaxy and extends about 5,000 light-years into one of the two lobes. The observed high-speed motion of bright knots in the jet implies that its radio-emitting electrons are traveling at nearly the speed of light. (Courtesy of NRAO/AUI/NSF.)
Fig. 13.9 . Composite image of the optically visible galaxy NGC 5128 and the bright radio galaxy Centaurus A. X-ray jets and radio lobes emanate from the active galaxy’s central, super-massive black hole. Microwave observations (orange), at a wavelength of 0.0087 m with the APEX array, show the radio lobes; the jets are seen in an x-ray image (blue) from the Chandra X-ray Observatory, and the visible light image is from a 2.2–m (87-inch) telescope of the European Southern Observatory. The central black hole, thought to have a mass of about 55 million solar masses, apparently ejects in falling matter in opposing particle jets at about half the speed of light. The jets inflate the two radio-emitting lobes of Centaurus A, one of the biggest and brightest objects in the radio sky and nearly 20 times the angular extent of the full Moon. The galaxy NGC 5128 has unusual dust lanes and is about 12 million light-years from Earth. The radio lobes are about a million light-years in extent. [Courtesy of ESO/WFI (visible light), MPIfR/ESO/APEX/A. Weiss et al. (microwave), NASA/CXC/CFA/R. Kraft et al. (x-ray).]
Fig. 13.10 . This barred spiral galaxy, designated NGC 1097, is located about 44 million light-years from Earth. It is a Seyfert galaxy and a moderate example of an Active Galactic Nucleus, or AGN for short, with jets shooting out of its core. A super-massive black hole, with about 100 million times the mass of the Sun is located at the center of the galaxy. As shown in this infrared view of NGC 1097, taken from the Spitzer Space Telescope, a star-forming ring surrounds its center. As gas and dust spiral into oblivion in the central black hole, they cause the ring to light up with hundreds of new stars. The galaxy’s spiral arms and the swirling spokes between them show dust heated by other newborn stars, as well as older stars. (Courtesy of NASA/JPL-Caltech.)
Fig. 13.11 . The Hubble diagram plot of the apparent magnitude of Type Ia supernovae plotted as a function of their redshift (top). At a redshift below about z = 0.1, there is a linear fit to the data, but at larger redshifts the observations begin to diverge from a straight line. The curved departures for distant supernovae at high redshift indicate an accelerating universe in which the speed of expansion is increasing. The observed data can be compared to cosmological models with different values of the omega parameter, W. It is the ratio of the inferred density to the critical mass density needed to stop the expansion of the universe in the future. The subscript L denotes the cosmological constant, a possible form of dark energy, while the subscript m denotes matter. (Adapted from Saul Perlmutter, Physics Today April 2003.)
Fig. 13.12 . The distance modulus m = m - M, or the difference between apparent magnitude m and absolute magnitude M, for Type Ia supernovae is plotted against their redshift, z. The omega parameter, W, is the ratio of the inferred density to the critical mass density needed to stop the expansion of the universe in the future. A comparison between the observations and models suggests a mass density of at most Wm = 0.3, significant dark energy with WL = 0.7, and an inflationary universe without spatial curvature with Wm + WL = 1.0. (Courtesy of Adam G. Reiss.]