Overview of Astronomy 322 Craig Heinke Winter 2009 The Visible Galaxy Galaxy in other colors Electromagnetic spectrum • Produced by moving charges • Frequency ∝ energy, Frequency ∝ 1/wavelength • Energy ∝ temperature4, and νmax ∝ temperature, for thermal emission • Neutron stars (106 K) • Hot stars (~104 K) • Cool stars (3*103 K) • Dust (20 K) • Cool gas (HI lines) • Cold gas (CO lines) Observations: Earth & Space Emission mechanisms • Blackbody--like a hot stove • Line emission--atoms absorbing or emitting radiation • Synchrotron--electrons spiraling in a magnetic field • Bremsstrahlung--fast electrons colliding Tour of our Galaxy • Illustration, based on recent observations Nearby stars • Distances by parallax • Accurate picture of stars in our galaxy National Geographic Stellar clusters • Stellar formation • Studying stellar evolution • Distances The Pleiades Globular clusters • Stellar evolution • Stellar dynamics • Structure and evolution of galaxy Color-magnitude diagrams • Study stellar evolution • Effects of composition Cold gas and dust • Dust absorbs optical, X-ray light • Emits light in infrared • Dust occurs in coldest gas Galactic rotation +280 Scutum Tangent k ) 1 260 − +100 s P e + Sagittarius r M s s e i u Tangent s m W51 o D k A a r i ( l C n a W50 W44 r A r 240 + Cyg e a r m y F m t OB7 c Vela i S147 Lindblad Ring & Local Arm 3 S147 c u Aquila Rift k o Cyg X CMa l p l 0 Maddalena’s e c a 220 OB1 Mon + v Cloud Gem r +30° l Carina OB1 Beam +30° S235 W3 Cas A m OB1 a E R i Tangent r x i d r P p n a a a 200 m A + r g e n r r r e d Centaurus R A s l e s e i u t n Tangent S O u −100 c g L A u Norma r +180 m Tangent +20° N +20° 180° 120° 60° 0° 300° 240° 180° +160 Galactic Longitude +140 +140 +1+2100° Resolution +10° +120 e +1d 00 +100 u t i t +a 80 +80 L 0° 0° c i t 60 60 +c + ) a 1 l − a s +G 40 +40 m k ( −10° −10° 20 y +20 + t i c o l 0 0 e v l a i −20 −20 d −20° −20° a r 40 40 R − − S L −60 −60 −30° −30° −80 −80 −100 180° 170° 160° 150° 140° 130° 120° 110° 100° 90° 80° 70° 60° 50° 40° 30° 20° 10° 0° 350° 340° 330° 320° 310° 300° 290° 280° 270° 260° 250° 240° 230° 220° 210° 200° 190° 180° −100 −120 Galactic Longitude −120 Ursa Major −140 Polaris −140 Flare Ophiuchus 180° 170° 160° 150° Cepheus140° 130° 120° 110° 100° 90° 80° 70° 60° 50° 40° 320° 310° 300° 290° 280° 270° 260° 250° 240° 230° 220° 210° 200° 190° 180° +20° Cam Maddalena’s Flare Cloud e 160 d − CTA-1 AquiGlaalactic LongiLtupduse GFaIlGa.c t2i.c– VLeoloncgitiyt-uindtegrated CO map of the Milky Way. The angular resolution is 9´ over most u Hercules t S147 G t Rift i S212 Coal Mon Gem S147 t f S235 r e i Vela CMa OB1 of the map, including the entire Galactic plane, but is lower (15´ or 30´) in some regions out a a t R Sack OB1 L OB1 180 0° − of the plane (see Fig. 1 & Table 1). The sensitivity varies somewhat from region to region, c i W3 Cas A Cyg W51 Rosette t Carina W44 Galactic O r since each component survey was integrated individually using moment masking or clipping c NGC7538 OB7 Cyg X Center G317−4 Nebula λ i FIG. 3.—Longitude-velocity map of CO emission integrated over a strip ~4° wide in latitude a Mon R2 l Gum 0.0 0.5 1.0 1.5 2.0 in order to display all statistically significant emission but little noise (see §2.2). A dotted line a S. Ori −200 centered on the Galactic plane (see §2.2)—a latitude range adequate to include essentially all Lacerta Nebula G Filament R g marks the sampling boundaries, given in more detail in Fig. 1. 20° Per OB2 R CrA i n log T dv (K km s−1) emission beyond the Local spiral arm (i.e., at |v| > 20 km s–1). The map has been smoothed − Aquila Chamaeleon Ori A & B mb South ∫ in velocity to a resolution of 2 km s–1 and in longitude to a resolution of 12´. The sensitivity Tau-Per-Aur Pegasus Orion Complex −220 Complex −1.5 −1.0 −0.5 0.0 0.5 1.0 varies somewhat over the map, since each component survey was integrated individually log T db (K arcdeg) using moment masking at the 3-σ level (see §2.2). 180° 120° 60° 0° 300° 240° 180° −240 mb Galactic Longitude ∫ 30° 20° 10° 0° 350° 340° 330° −260 Warm gas • Atomic hydrogen • Fills most of Galaxy • Disturbances to warm gas include infalling material, supernovae Hottest gas • For T > 106 K, fully ionized • Emits X-rays • Heated by supernovae Supernova remnant in X-rays Energetic particles Lowest-energy radio Highest-energy gamma rays • Particles accelerated by supernovae to high energies • Electrons emit both radio waves, gamma rays • Known as “cosmic rays” when hit Earth Optical vs. Near-IR • Dust absorbs bluer light • Infrared light better tracer of (old) stars Star formation • Collapse of clouds • Ionized regions • Feedback Orion Nebula, HST To the Galactic Centre in IR Optical 2MASS near-IR Galactic Center in other wavelengths Radio: NRAO X-ray: Chandra Other galaxies HST GOODS deep field Local Group of galaxies • Range of galaxy sizes, shapes • Continuing formation, evolution of galaxies Satellites of Milky Way: R. Powell Standard Candles • Measure distances • Cepheid variables • Type 1a Supernovae SN 1994D, Hi-Z Search Team Expanding universe • Doppler shifts of spectral lines • Hubble’s Law: redshift ∝ distance • Evolution of universe Spiral galaxies • Spiral arms, star formation waves • Galactic bulges M81, optical: R. Gendler Optical vs. ultraviolet Dust and gas • Cool gas forming stars • Hot gas near core Irregular galaxies • No clear order • Small, star-forming galaxies Large Magellanic Cloud: KAO Starbursts • Extreme star formation • Often triggered by interactions • Galactic winds from supernovae M82: HST optical, NASA/ESA Galactic interactions • Mergers, growth of galaxies • Evolution of galaxies Antennae Galaxies, Whitmore/NASA Elliptical galaxies • Ellipsoidal shapes • Little gas, dust; older stars • Result of mergers ESO 325-G004, HST Groups of galaxies • Gravitationally bound • Will interact, merge HCG 87, optical Gemini GMOS-S Clusters of galaxies • Largest bound structures • Mostly ellipticals • Star formation terminated Coma Cluster, HST/Carter Hot gas in clusters • Majority of normal matter is hot gas • Study in X-rays • History of cluster mergers Coma Cluster, X-rays (XMM) Gravitational lensing • Lensing as bending of light by gravity • Measure mass of clusters • Probe of dark matter Abell 1689, HST Dark matter • Evidence for dark matter: • Speed of rotation of galaxies (including our own) • Speed of galaxies within galaxy clusters • Extra mass revealed by gravitational lensing • Constraints on nature Active galactic nuclei (AGN) • Accretion onto massive black hole • At centers of most galaxies • Observable across universe as quasars Spiral galaxy with AGN AGN Jets • Matter ejected by AGN • Near light speed Effects of AGN • On star formation in galaxies • On galaxy clusters • On intergalactic space Perseus cluster of galaxies, X-ray Large-scale structure • Larger than clusters • Bubble-like; voids, filaments • Cosmological simulations CfA Survey; Geller, Huchra History of the universe • Formation of structures • Cosmic microwave background radiation • Acceleration of universal expansion: dark energy WMAP: Radiation from early universe Figures (Jan. 7) Fig. 1.9, SG Fig. 1.17, Carroll & Ostlie Fig. 2.2, SG Fig. 2.3, SG Fig. 2.4 Pleiades mass function (blue) vs. Salpeter mass function (red) .