Astrophysics Introductory Course - o Nstaff.on.br/etelles/lectures/bender/chapter0.pdf · Another...

I?M?P?R?S on ASTROPHYSICS at LMU Munich

Astrophysics Introductory Course

Lecture given by

Ralf Bender

in collaboration with:

Chris Botzler, Andre Crusius-Watzel,Niv Drory, Georg Feulner, Armin Gabasch,

Ulrich Hopp, Claudia Maraston,Michael Matthias, Jan Snigula, Daniel Thomas

Fall 2001

Astrophysics Introductory Course Fall 2001

Outline of the IMPRS Introductory Course

Introduction and overview (telescopes, instruments, slide show...)

Matter and radiation

Stars: global properties and spectra

Stellar structure, evolution and final stages

Interstellar medium, star formation and exo-planets

Galaxies: phenomenology

Stellar dynamics

Stellar populations, chemical evolution and star formation

Dark Matter, Gravitational lensing

Groups and clusters of galaxies

Active galactic nuclei and massive black holes

Cosmological standard model

Formation of structure in the universe

Galaxy formation and evolution


Chapter 0

Introduction and Overview


0.1 The limiting factors

Half absorption altitude in the earth atmosphere

→ Dominant windows in the atmosphere are in the visible and radio frequency regions

→ X-Rays and UV are very strongly absorbed, γ rays and IR strongly absorbed


Brightness of the nightsky at high galactic and ecliptic latitude.


The brightness of the nightsky is the main limitation for the observability of very faint ob-jects. In the blue and optical, observations with satellites and ground-based telescopeshave similar backgrounds. In the infrared, observations in the orbit are orders of magnitudemore efficient, because of strong OH emission lines and the IR-radiation from the warmterrestrial atmosphere. In the radio, a main limitation on the ground is radio pollution byhuman technology (radio, tv etc). To overcome the extraterrestrial backgrounds like thezodiac light, faint stars and IR cirrus (from dust in the Milky Way) would require to bring asatellite observatory outside of the solar system or even the Galactic plane, respectively.


Absorption by gas and dust in the Milky Way

E(B-V) is a measure of redding and absorption. E.g., E(B-V) of 0.35 implies that any objectoutside the Milky Way is dimmed by about a factor 2.5 at 5500A. Burstein and Heilesderived these maps mostly from the column density of neutral hydrogen which is assumedto be related to the column density of dust as well.


0.2 Telescopes and Instruments

Ground based telescopes (examples)

→ Radio [cm to sub-mm]: Effelsberg 100m, VLA, VLBI, IRAM; ALMA ...→ Optical (350 nm to ∼ 10 µm): 8m-class: Keck, VLT, HET, LBT, Gemini ...

(and many small 2m to 4m–class telescopes are still active) ...→ γ-rays: HEGRA (≥ 0.1 TeV, Cerenkov-Telescopes) ...→ ν-telescopes: GALLEX, Kamiokande, Borexino, Amanda ...→ LISA, LIGO gravitational wave detectors under developement

Satellite observatories (examples)

→ radio: COBE, MAP, PLANK, [Boomerang] ...→ infrared: IRAS, ISO, [Sofia]; Herschel, NGST ...→ UV-optical: HST, IUE, HUT, Hipparcos ...→ X-rays: ROSAT, XMM-Newton, Chandra ...→ γ-rays: Compton-GRO, Integral ...

For more information check e.g. the ESA, NASA or MPE, ESO, MPA, USM homepages.


Planck CMB satellite (ESA), Herschel far infrared and submm satel-lite (ESA), Calar Alto 3.5m telescope (MPIA), Hubble Space Telescope(NASA), Very Large Array radio interferometer (NRAO), Very LargeTelescope (ESO), X-ray stellite ROSAT (MPE, DLR, NASA), AtacamaLarge Millimeter Array (2006, ESO, NRAO).


VLT instruments: imaging, spectroscopy and interferometry from the near UV to mid IR.


FORS and ISAAC at the VLT, imagers and spectrographs for the optical and infrared.


Left: The Charge Coupled Device in FORS. CCDs are the detectors in near UV-opticalastronomy with quantum efficiencies up to 90% and sizes up to 4000 by 4000 pixels.

Right: EGRET (Energetic Gamma Ray Experiment Telescope) is a spark chamber aboardthe Compton Gamma-Ray Observatory. It is designed to cover the energy range from 20MeV to about 30 GeV using a multilevel thin-plate spark-chamber system to detect gamma-rays by the electron-positron pair production process.


Another key tool of modern astrophysics: the computer. Shown is the Hitachi SR8000 of theLeibniz Rechenzentrum Munich, one of the 3 most powerful computers in the world (2002,memory: 1500 Gigabyte, 2.2 Teraflops/s). Besides extensive simulations, the storage ofhuge data volumes from ground based and satellite observatories is extremely demanding.In the near future, connected data centers will allow to construct a virtual astrophysicalobservatory.


0.3 Astronomy, Physics & Technology

astronomy physics & technologyKepler’s laws gravity law, Newtonian physicsspectral analysis of stars and hot gas Helium discovery, quantum mechanics of

forbidden lines in low densitiesperihel motion of mercury, light deflection bysun, binary pulsar

general relativety, gravitational waves

energy production in stars and supernovae nuclear physics, element synthesisneutron stars & white dwarfs equation of state for degenerate matter

up to nuclear densitiestelescope development optics, new polishing techniques, glas

and technical ceramics (Zerodur/Ceran)detection of faintest sources new substrates for highly efficient detec-

tors, e.g. CCDsdark matter, early universe, solar neutrinos particle physics, unknown particle

speciesdark energy, cosmological constant,quintessence

particle physics, new physics

γ-ray bursts new physics (probably not: hypernovae)image processing medical applications


Astronomy’s contribution to physics and our concept of matter in the last 20 years:


The slide show: a tour through the universe


The Sun: L� = 3.9 1033 erg s−1, M� = 2.0 1033 g, R� = 7 105 km, T�,photosphere = 5800 K


The Solar Corona, T = 106K, plasma physics at its best


Solar neighbourhood stars observed by the Hipparcos satellite


a familiar view of the dark sky...


again ...


The infrared sky in the direction of Orion. The bright emission comes from dust grainsheated by starlight. The blue dots indicate the positions of the bright stars, with Betelgeuseat the upper center. The Orion Nebula is the bright yellow blob at the lower right. The greenbox indicates the field of view of the next image.


Radio emission from cold carbonmonoxide gas in thedirection of Orion. Red and blue indicate Doppler shifts.


Near-infraredimage (2MASS)of the OrionNebula M42,the neareastlarger H II re-gion, whereyoung stars areformed in largernumber


The Orion Nebula in optical light, from the Hubble Space Telescope. The bar at the lowerleft is a wall of gas viewed edge-on. This gas glows because it is ionized by the four hot”Trapezium stars” just to the left of center.


The Orion Nebula in infrared light. The bar at the lower left is less prominent, but we seea bright nebula in the upper right that is not seen in the visible image before. The orangerepresents infrared line emission from hydrogen molecules being blown away by a powerfulembedded star (see below).


Left: a closer view of the Orion Nebula in optical light from HST. The trapezium stars areclearly visible. The blue outline shows the field of view of the infrared image. Right: Infraredimage by the NICMOS camera on the HST. We see a cluster of newborn stars buried withinthe dust cloud beneath the optical nebula.


Close-up of the Trapezium stars, showing ”cometary globules” of gas, evidently newly form-ing planetary systems being illuminated by the bright star at the lower right.


The insets show close-up views of ”proplyds” - protoplanetary disks in the Orion Nebula.The dark disks of dust are seen in silhouette against the bright glow of the Nebula.Upper left: a face-on disk with a central star like the Sun.Upper right: the central star is obscured by a thick edge-on disk.Lower left: another face-on system; the scale of our Solar System is indicated below.


Artist’s view of the formation of a planetary system.


Planets around other stars found by velocity variations of the star


A diagram of the orbits of the 3 planets around Upsilon Andromedae (red dots). The dashedcircles show the orbits of Mercury, Venus, Earth and Mars to give the scale of the orbits.


Eta Carinae, a massive star at old age.


The Crab nebula, a remnant of a supernova which exploded in 1054.


Planetary nebulae, solar-type stars at old age.


The globular cluster M79, one of the oldest objects known (about 14 Gyr).


Milkyway, Sbc galaxy (all-sky projection in optical by Mellinger)


Milkyway, Sbc galaxy, distribution of neutral hydrogen (HI, 21cm) and CO (2.6mm).


Milkyway, Sbc-galaxy (70% sky projection in near IR (2µm), COBE satellite)


The Small and Large Magellanic Clouds (NOAO)


30 Doradus in the LMC (VLT image): birth of a globular cluster (?)


30 Doradus in the LMC: birth of a globular cluster (?)X-rays: red, Hα: green, UV: blue


The spiral galaxyM 31 and itssatellites galaxiesM 32 (compactsmall elliptical)and NGC 205(dwarf elliptical)

plus an objectthat doesn’t be-long there butshows the scale.


The small spiralgalaxy M 33, acompanion ofM 31, has nobulge


Leo 1 (MV = −12), dwarf elliptical (dwarf spheroidal) companion of Milky Way


NGC 205 (MV = −16.3), dwarf elliptical companion of M31 (NOAO)


Blue Compact Dwarf (BCD) NGC 1705, blue: bluecontinuum, green: red continuum, red: Hα (G. Meurer)


Dwarf irregular NGC 2915 yellow: optical blue: HI


The edge-on spiralgalaxy NGC 5907 - theMilky Way would looklike this galaxy if seenfrom outside and edgeon. However the bulgeof the Milky Way is moreprominent. (Wendelsteinthree-color-image)


The face-on spiral galaxy M 101 (Wendelstein three-color-image).


NGC 613: SBc-galaxy


Spirals in ultraviolett (dominated by massive stars) and visual (average population),Ultraviolet Imaging Telescope, Astro mission.


The M 81 group at 3.5 Mpc distance in the optical and in HI


The NGC 2300 group of galaxies in X-ray (blue) and optical (b/w)


The ellipticals M 84 (right) and M 86 (middle) in the Virgo cluster (NOAO).


central part of Coma cluster with two cDs.


X-Ray Gas in Galaxy Clusters

Coma cluster (left: optical image, right: X-ray image)


Galaxy Cluster Cl0024+1645, strong lensing reconstruction (left, courtesy S. Seitz) of HST image (right, Colless et al.); light blue = caustic structure, bold

green = critical lines of ’infinite’ amplification, squares = observed positions of multiple imaged source (A,B,C,D,E in color image), yellow crosses = predicted

position of the lensmodel, yellow circle = position of source in source plane, red crosses = mass centers used for the lens model. The caustics are obtained

by mapping the critical lines into the source plane.


Active galaxies

NGC 7742, a Seyfert galaxy


NGC 383 (= 3C31), a radio galaxy, blue: optical, red: radio (A. Bridle)


Merging of two radio galaxies (and two black holes!), (A. Bridle)


One of the currently most distant objects known,a quasar at redshift 5.8 (Sloan Digitial Sky Survey)


The inner 10 pc of M31 (real color HST image. A 30 million solar mass black hole sits inthe blue cluster. The red blob of stars corresponds to the apocentre of an elliptic stellardisk around the black hole. The black hole is probably not at the center of the galaxy.

(Kormendy and Bender 1999).


Interacting, merging and starbursting galaxies

Interacting galaxy pair. Note that spiral disks are not optically thick!


Cartwheel galaxy


Antenna galaxies


M 82, a starburst galaxy, white/brown: stellar light and dust,red: hot expanding gas in Hα (Subaru telescope)


Various evolutionarysteps of spiral-spiralmergers


Las Campanas Redshift Survey(LCRS)


2dF Galaxy Redshift Survey


The Hubble DeepField (North), thedeepest availableoptical image,demonstratesthe evolutionof galaxies andshows objectsup to redshifts ofabout 5 (or 10%of the age of theuniverse)


Cosmic Microwave Background variations as observed by WMAP satellite (2003)


Cosmic Hierarchies

Object ρ np δρ/ρ Radius D/R Vrel. Nsmallobj.

[g cm−3] [cm−3] [km s−1]Universe 10−30 10−6 0 6 Gpc - - 109

groups/clusters 10−28 10−4 102 1 Mpc 10 500 102

galaxies 10−24 100 106 10 kpc 20 700 1011

stars 10+1 1024 1030 106 km 108 300 -neutron-stars 1014 1038 1044 101 km - - -

ρ: mass densitynp: proton number densityδρ/ρ: over density relative to mean density of the universeR: average radius of objectsD/R: average distance between objects relative to their sizeVrel.: typical relative velocity between objectsNsmaller: number of next smaller objects contained in structure


Object length[m]

Elektron 2.8 10−15

Bohr-Radius 5.3 10−11

ISM dust 3 10−7

Blue whale 3 10+1

Comet (core) 5.5 10+3

Neutron star 1 10+4

Sun 7 10+8

Astron. Unit 1.5 1011

Lightyear 9.46 1015

1 Parsec 3.08 1016

next star 4 1016

globular cluster 4 1018

Milky Way Galaxy 8 1020

Distance M 31 2 1022

Diameter Virgo 1 1023

Distance Virgo 7 1023

Universe 1 1027

Object Mass[kg]

Elektron 9.11 10−31

Proton 1.67 10−27

Z0 1.60 10−25

Planck mass 1.67 10−27

Tyrannosaurus Rex 105

Comet 1 1013

Mountain 3 1014

Planetoid 3 1019

Earth moon 7.3 1022

Earth 6.0 1024

Jupiter 1.9 1027

Sun 2.0 1030

Globular Cluster 1 1036

Milky Way galaxy 2 1042

Coma gal.-cluster 2 1045

Universe 4 1051


from Shapiro, Teukolsky:Black Holes,White Dwarfsand Neutron Stars


The Big Questions (a personal selection)

Formation of stars and planets

Extrasolar planets, search and characterization

Population III

Supernovae

The cosmic recycling process (stars-gas-chemical elements)

Formation and evolution of galaxies

Cosmic star formation history

Supermassive blackholes and active nuclei

Nature of the γ-ray bursts

Nature and density of the dark matter

Formation of structure in the universe

Dark Energy and cosmological constant

Inflation and phase transitions in the early universe

...........


Bibliography

General Astronomy

* Caroll, B.W., Ostlie, D.A.: Modern Astrophysics, Addison-Wesley 1996

Shu, F.: The Physical Universe, University Science, Mill Valley

Padmanabhan, T: Theoretical Astrophysics I, II, III, Cambridge University Press 2000ff

Kuyper, G., Middlehurst, B. (eds): Stars and Stellar Systems, I, II, III, University of ChicagoPress 1963ff

Audouze, J., Israel, G.: Cambridge Atlas of Astronomy, Cambridge University Press, 1985

Hoskin, M.: Illustrated History of Astronomy, Cambridge Univ. Press 1997

Telescopes and Instruments

Walker: Astronomical Observations, Cambridge Uni. Press

Kitchin: Astronomical Techniques, Adam Hilger


* Lena: Observational Astrophysics, Spinger Verlag, Berlin

Longair, M.: High Energy Astrophysics, Cambridge University Press 1992

Stars

* Bohm-Vitense, E.: Stellar Astrophysics I, II, III, Cambridge University Press 1997

Kippenhahn, R., Weigert, A.: Stellar Structure and Evolution, A&A Library, Springer Verlag,Berlin 1990

Schwarzschild, M: Structure and Evolution of the Stars, Dover Publications, New York, 1958

Mihalas, D.: Stellar Atmospheres, Freeman, San Francisco 1970

Bowers, R., Deeming, T.: Astrophysics I, Jones&Bartlett, Boston, 1984

A.C. Phillips: The Physics of Stars, Wiley, Chichester 1994

* Prialnik, D.: Stellar Structure and Evolution, Cambridge 2000

Arnett, D.: Supernovae and Nucleosynthesis, Princeton University Press, 1996

Shapiro, S., Teukolsky, S.: Black Holes, White Dwarfs and Neutron Stars, Wiley, New York


1983

Interstellar Medium and Plasmas

* Spitzer, L.: Physical Processes in the Interstellar Medium, Wiley, New York, 1987

Bowers, R., Deeming, T.: Astrophysics II, Jones&Bartlett, Boston, 1984

Scheffler, H., Elsasser, H.: Physics of the Galaxy and Interstellar Matter, Springer, Berlin,1988

Dyson, J.E., Williams, D.A.: The Physics of te Interstellar Medium, Institute of Physics Pub-lishing, Bristol, 1997

Osterbrock, D.: Astrophysics of Gaseous Nebulae and Active Galactic Nuclei, UniversityScience Books, Mill Valley, California, 1989

* Rybicki, G., Lightman, A.: Radiation Processes in Astrophysics, Wiley, New York, 1979

Burton, W., Elmegreen, B., Genzel, R: The Galactic Interstellar Medium, Saas Fee Course1991. Springer Verlag, Berlin

Galaxies


* Binney, J., Merrifield, M.: Galactic Astronomy, Princeton University Press, 1998

Sparke, L., Gallagher, J.: Galaxies in the Universe, Cambridge University Press, 2000

Binney, J., Tremaine, S.: Galactic Dynamics, Princeton Univ. Press, 1987

Tinsley, B.M., in: Fund. of Cosm. Physics, Vol.5, p.287, 1980

* Pagel, B.: Nucleosynthesis and Chemical Evolution of Galaxies, Cambridge UniversityPress 1997

Peterson, B.: Active Galactic Nuclei, Cambridge University Press, 1997

Longair, M.: High Energy Astrophysics, Cambridge University Press 1992

Large Scale Structure and Cosmology

Sandage, A., Kron, R., Longair, M.: The Deep Universe, Springer Verlag 1995

* Peebles, P.J.E.: The Physical Universe, Princeton Univ. Press, 1993

Padmanabhan, T.: Structure Formation in the Universe, Cambridge Univ. Press, 1993

Dekel, A., Ostriker, J.: Formation of structure in the universe, Cambridge University Press,


1999

Longair, M.: Galaxy Formation, Springer Verlag 1998

and:

Symposia of the International Astronomical UnionSymposia of the Astronomical Society of the PacificA&A (= Astronomy and Astrophysics)ApJ (= Astrophysical Journal)AJ (= Astronomical Journal)MNRAS (= Monthly Notices of the Royal Astronomical Society)PASP (= Publications of the Astronomical Society of the Pacific)Nature...


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