Astronomy 305/Frontiers in Astronomy

11/11/03 Prof. Lynn Cominsky 1

Class web site: Class web site: http://glast.sonoma.edu/~lynnc/courses/ahttp://glast.sonoma.edu/~lynnc/courses/a305305

Office: Darwin 329AOffice: Darwin 329A

(707) 664-2655(707) 664-2655

Best way to reach me: Best way to reach me: [email protected]@charmian.sonoma.edu

Astronomy 305/Frontiers in Astronomy 305/Frontiers in AstronomyAstronomy


Group 11Group 11


What does the Universe look What does the Universe look like?like?

What happens when galaxies What happens when galaxies collide?collide?

How do galaxies cluster?How do galaxies cluster? What are the largest structures in What are the largest structures in

the Universe?the Universe? What other types of background What other types of background

radiation exist?radiation exist? Summary of scales in the UniverseSummary of scales in the Universe


Cartwheel GalaxyCartwheel Galaxy Wheel shape was Wheel shape was

formed from formed from collision of two collision of two galaxiesgalaxies

Bright stars are Bright stars are forming at the forming at the edges of the wheel edges of the wheel (10(1055 light years in light years in diameter)diameter)

Intruder galaxy is Intruder galaxy is no longer visibleno longer visible This is from

HST


Collisions and Mergers Collisions and Mergers movie movie

Galaxy collisions contribute to large Galaxy collisions contribute to large scale structure formationscale structure formation

Note: galaxies do not make noise Note: galaxies do not make noise when they collide!when they collide!


More Galaxy Collision More Galaxy Collision moviesmovies


Galaxy HarassmentGalaxy Harassment Spirals merge to form ellipticalsSpirals merge to form ellipticals Biggest elliptical cannibalizes the Biggest elliptical cannibalizes the

others to form one giant elliptical others to form one giant elliptical in the center of the clusterin the center of the cluster

Dwarf ellipticals are formed by Dwarf ellipticals are formed by harassment (high velocity harassment (high velocity encounters) of low-mass spiralsencounters) of low-mass spirals

Detectable arcs of debris are left Detectable arcs of debris are left over – providing fuel for quasarsover – providing fuel for quasars


Galaxy Harassment movieGalaxy Harassment movie Gas is redGas is red Stars are yellow and Stars are yellow and

in a disk initiallyin a disk initially Dark matter is blue Dark matter is blue

and in a halo initiallyand in a halo initially Green are other Green are other

galaxies in the clustergalaxies in the cluster Initial spiral becomes Initial spiral becomes

warped, and warped, and eventually ellipticaleventually elliptical


Virgo cluster of Virgo cluster of galaxiesgalaxies

The Virgo cluster of galaxies is about 65 million light years away It contains about 2500 galaxies It is dominated by M87

M87


Virgo ClusterVirgo Cluster

It is the nearest rich cluster of galaxies It is the nearest rich cluster of galaxies Classification - irregular Classification - irregular Covers about 100Covers about 100oo of sky or at its distance it of sky or at its distance it

spreads out over tens of millions of light spreads out over tens of millions of light years years

Recessional velocity is about 0.3% of velocity Recessional velocity is about 0.3% of velocity of light of light

X-ray emission concentrated around X-ray emission concentrated around individual galaxies, particularly M84 and M86individual galaxies, particularly M84 and M86

The strong radio galaxy M87 in the Virgo The strong radio galaxy M87 in the Virgo cluster is also a strong source of X-rays cluster is also a strong source of X-rays


X-ray emission from X-ray emission from ClustersClusters

Gas in clusters of galaxies is held by mass where:

Mass of hot gas is more than 3 times the mass of the visible light galaxies in the Virgo cluster Strongest X-rays are around M87

Virgo/ROSATM = V2R

G


Distances to Galaxy ClustersDistances to Galaxy Clusters

Brightest Cluster Galaxies: Brightest Cluster Galaxies: The brightest The brightest galaxy in a cluster of galaxies has been galaxy in a cluster of galaxies has been used as a standard candle. used as a standard candle.

But: But: rich clusters with many galaxies rich clusters with many galaxies will probably have the most luminous will probably have the most luminous galaxies even though these galaxies are galaxies even though these galaxies are very rare, while the brightest galaxy in very rare, while the brightest galaxy in less rich clusters are probably not as less rich clusters are probably not as brightbright


Standard CandlesStandard Candles

FFobsobs = L = Ltruetrue/(4/(4dd22) where ) where FFobs obs = flux observed at = flux observed at

EarthEarth LLtrue true = true brightness at = true brightness at

sourcesource d = distance from Earth d = distance from Earth

to sourceto source

Objects with known luminosities that Objects with known luminosities that can be used to calculate distancecan be used to calculate distance

movie


Types of Galaxy ClustersTypes of Galaxy Clusters Regular clustersRegular clusters

concentrated central core concentrated central core well-defined spherical structurewell-defined spherical structure often dominated by a giant often dominated by a giant

galaxy galaxy usually quite rich, M~10usually quite rich, M~101515 M Moo

most galaxies are elliptical or most galaxies are elliptical or lenticular lenticular

Irregular clustersIrregular clusters no well-defined centerno well-defined center ~half the galaxies are spirals~half the galaxies are spirals Often contain subclustersOften contain subclusters Probably not steady stateProbably not steady state


Hydra ClusterHydra Cluster Distance of 840 million light years Several hundred galaxies in the cluster 35 million degree gas in center rising to 40 million in the outside Several million light years across the gas cloud Optical/La Palma


Hydra ClusterHydra Cluster

Radio/NRAO X-ray/Chandra


Cluster FormationCluster Formation

Formation and Formation and evolution of a evolution of a galaxy cluster galaxy cluster (from T6 group (from T6 group at Los Alamos)at Los Alamos)

Evolution of a Cd galaxy cluster (from John Dubinski at CITA)

movies


How clusters affect galaxy evolutionHow clusters affect galaxy evolution

Ram pressure and Ram pressure and turbulent stripping of turbulent stripping of gas from a spiral gas from a spiral galaxy as it falls galaxy as it falls through the hot ICM of through the hot ICM of a rich galaxy cluster a rich galaxy cluster (by Vicent Quilis with (by Vicent Quilis with Ben Moore) Ben Moore)

The galaxy model is 3d The galaxy model is 3d with a stellar disk, with a stellar disk, bulge + dark matter bulge + dark matter halo. The colours show halo. The colours show the gas density in a the gas density in a thin slice centered on thin slice centered on the diskthe disk

movie


Small ClusterSmall Cluster

X-rays from this smaller cluster were discovered by ROSAT Hot gas engulfs the two bright elliptical galaxies It is about 500 million light years away


Very Distant ClusterVery Distant Cluster

This is a very red cluster, located at Z~1 It is the most distant cluster discovered by HST It may be too far away to have formed in a dense universe


Very Distant ClusterVery Distant Cluster

This cluster is 8 billion light years away, so it formed when the universe was half its present age It is also very red It should not exist if the Universe is dense


Merging ClustersMerging Clusters

A2256 cluster has about 500 galaxies It is about 10 million light years across It is about 1 billion light years away The 80 million degree gas is brightest in the center where two clusters are merging


Merging ClustersMerging Clusters

A2142 cluster The 50 million degree gas is coolest in the center where two clusters have finished merging The gas outside the center is 100 million degrees – heated by the collision Chandra image


Cannibal ClusterCannibal Cluster

A3827 is about 1.5 billion light years away The central dominant galaxy is eating five smaller galaxies

ESO/Optical


Coma ClusterComa Cluster

Coma cluster has about 1000 galaxies It is located near the north galactic pole It is about 250 million light years away (80 Mpc) Large bright central cluster is merging with smaller galaxy group at the lower right

3 Mpc


Perseus ClusterPerseus Cluster

One of the closest galaxy clusters at a distance of 300 million light years Part of the Perseus Pisces supercluster which is 15 degrees across and has over 1000 galaxies


Local SuperclusterLocal Supercluster The Local supercluster contains the Virgo cluster of galaxies as well as about 50 galaxy groups


SuperclustersSuperclusters

Superclusters usually Superclusters usually have 3-10 clusters of have 3-10 clusters of galaxiesgalaxies

They are not They are not gravitationally boundgravitationally bound

Our local Our local supercluster contains supercluster contains the Virgo cluster (at the Virgo cluster (at 16 Mpc) and extends 16 Mpc) and extends about 40- 50 Mpcabout 40- 50 Mpc

Local Supercluster


““Stickman”Stickman” ““Slice” –style Redshift survey pioneered by Slice” –style Redshift survey pioneered by

Margaret Geller, Marc Davis and John HuchraMargaret Geller, Marc Davis and John Huchra

Distance is plotted vertically as given by redshifts

The body of the stickman is due to the Coma cluster

His arms form “walls”


Las Campanas SurveyLas Campanas Survey Done by Shectman et al. Largest redshift survey Clearly shows walls and voids

75-80% of space is devoid of bright galaxies Typical distance between 2 galaxies is around 7.5 Mpc

Typical distance between 2 clusters is around 20 Mpc


Flyby universe movieFlyby universe movie Las Campanas data – notice the Las Campanas data – notice the

walls and voids as you fly bywalls and voids as you fly by


Walls and VoidsWalls and Voids Universe looks like soap bubbles in 3DUniverse looks like soap bubbles in 3D Galaxies occur on the bubble surfacesGalaxies occur on the bubble surfaces Superclusters are formed where bubbles Superclusters are formed where bubbles

mergemerge Walls are made of elongated superclusters – Walls are made of elongated superclusters –

the largest is the “Great Wall” - about 100 the largest is the “Great Wall” - about 100 Mpc in length at a distance of 100 MpcMpc in length at a distance of 100 Mpc

Voids are about 100 Mpc in diameter – are Voids are about 100 Mpc in diameter – are 90% of space90% of space

Clusters of galaxies are bright spots on the Clusters of galaxies are bright spots on the wallswalls


Large Scale Structure formationLarge Scale Structure formation

Comparison of the 2df galaxy redshift survey to mock Comparison of the 2df galaxy redshift survey to mock catalogue constructed from a Lambda CDM simulation catalogue constructed from a Lambda CDM simulation (from Ben Moore)(from Ben Moore)

movie


XMM-Newton LSS SurveyXMM-Newton LSS Survey

X-ray emitting clusters of galaxies X-ray emitting clusters of galaxies About 15 per square degreeAbout 15 per square degree


Lyman-alpha forest Lyman-alpha forest studiesstudies

Lyman alpha is the name of the electron Lyman alpha is the name of the electron transition from n=1 to n=2 in Hydrogentransition from n=1 to n=2 in Hydrogen

When the H atom is hit by a photon, the electron When the H atom is hit by a photon, the electron can get enough energy to make this transition, can get enough energy to make this transition, and the photon is removed from the initial beam and the photon is removed from the initial beam from the sourcefrom the source


The observer sees light from the distant quasar The observer sees light from the distant quasar that is absorbed due to intervening H-cloudsthat is absorbed due to intervening H-clouds

However, because the Universe is expanding, However, because the Universe is expanding, the Ly-the Ly- absorption lines occur at different absorption lines occur at different wavelengths, which tell you the distance to each wavelengths, which tell you the distance to each cloudcloud

Lyman-alpha forest Lyman-alpha forest studiesstudies

quasar

clouds


Quasar clustering studiesQuasar clustering studies

Measurements of Measurements of positions of QSOs positions of QSOs can be used to can be used to trace large scale trace large scale structurestructure

This shows the This shows the spectra of 10 spectra of 10 QSOs as a QSOs as a function of function of redshiftredshift


Quasar clustering studiesQuasar clustering studies

2dF survey measured redshifts from 2dF survey measured redshifts from 250,000 galaxies and 23,000 QSOs 250,000 galaxies and 23,000 QSOs

Used camera with two-degree wide field on AAT to measure up to 400 redshifts simultaneously


2dF results2dF results

Walls and Walls and voids also voids also seen in seen in southern southern hemispherhemispheree


Formation of Large Scale Formation of Large Scale StructureStructure

Simulation by Simulation by Martin White Martin White shows the shows the evolution of evolution of structure structure starting with starting with fluctuations in fluctuations in the Cosmic the Cosmic Microwave Microwave BackgroundBackground

movie


The End of GreatnessThe End of Greatness

Most recent Most recent surveys are so surveys are so large that the large that the largest structures largest structures (about 100 Mpc) (about 100 Mpc) are smaller than are smaller than the survey sizethe survey size

This is a 200 Mpc This is a 200 Mpc simulation from simulation from Ben Moore (using Ben Moore (using CDM)CDM)

movie


Where are we going?Where are we going? The Milky Way Galaxy is falling towards the Virgo cluster at ~300 km/s The Virgo cluster is falling towards the Hydra-Centaurus supercluster also at ~300 km/s

But the Hydra-Centaurus cluster is also falling towards something…..


Great AttractorGreat Attractor

~1016 solar masses concentrated 65 Mpc away in the direction of Centaurus

Abell 3627 near the Great Attractor

The “Great Attractor” seems to be pulling in the Hydra-Centaurus super-cluster

But only 10% that amount of visible matter can be seen!


Wedge Plot ActivityWedge Plot Activity

These data are from CLEA’s LSS labThese data are from CLEA’s LSS lab Each group should plot 20 of the Each group should plot 20 of the

galaxies on the wedge plot galaxies on the wedge plot transparencytransparency

Then we will put all the plots Then we will put all the plots togethertogether

How many clusters do you see?How many clusters do you see? Why is the wedge plot a better Why is the wedge plot a better

representation of the measurements representation of the measurements than the linear plot?than the linear plot?


Scales in the UniverseScales in the Universe Solar systemSolar system

http://http://www.csupomona.edu/~ajm/materials/scales.htmlwww.csupomona.edu/~ajm/materials/scales.html 12 billion km in diameter 12 billion km in diameter

Milky Way Galaxy Milky Way Galaxy 40,000 pc 40,000 pc (~120,000 light years) (~120,000 light years)

Local Group Local Group few Mpc few Mpc Larger Cluster Larger Cluster several Mpc several Mpc Great Wall Great Wall 100 Mpc 100 Mpc Observable Universe Observable Universe 3,000-6,000 3,000-6,000

Mpc (10-20 billion light years) Mpc (10-20 billion light years)


Infrared BackgroundInfrared Background The Cosmic InfraRed Background The Cosmic InfraRed Background

(CIRB) is the radiation from stars in (CIRB) is the radiation from stars in many faint galaxies. many faint galaxies.

It is what is left over after emission It is what is left over after emission from our Solar System and our from our Solar System and our Galaxy has been subtracted away Galaxy has been subtracted away

Near IR is redshifted starlight from Near IR is redshifted starlight from distant galaxiesdistant galaxies

Far IR is starlight absorbed by dust Far IR is starlight absorbed by dust and reemittedand reemitted


Infrared BackgroundInfrared Background

Red shifted starlight

Reemitted by dust

CMB


Zodiacal LightZodiacal Light Diffuse visible Diffuse visible

light reflected light reflected from from interplanetary interplanetary dustdust

Orbits in same Orbits in same plane as planetsplane as planets

Brightest (in Brightest (in North) in fall North) in fall and springand spring


Ultraviolet Background Ultraviolet Background The last spectral region to be The last spectral region to be

explored in detailexplored in detail Narrow bands have been searchedNarrow bands have been searched Many mechanisms exist across the UV Many mechanisms exist across the UV

bandband Fluorescent emission from molecular HFluorescent emission from molecular H22

Emission lines from highly ionized atomsEmission lines from highly ionized atoms Hot intergalactic medium?Hot intergalactic medium? Shock heating from cosmic structure Shock heating from cosmic structure

formation?formation?


X-ray BackgroundX-ray Background

ROSAT 0.75 keV map

Shows smooth blue background plus bright superbubble ring at D=150 pc with R= ~100 pc


X-ray BackgroundX-ray Background

Discovered over 35 years ago in rocket flights Early theories explained the X-ray background as a diffuse, hot gas which filled the Universe Data from Einstein Observatory showed about 50% of the background could be due to quasars ROSAT data explained about 60% of the 1-2 keV X-ray background with quasars However flux and energy spectra did not add up correctly if the background was all quasars


Chandra dataChandra data

At least 80% of X-ray background is made of discrete sources including two new types:

Very distant galaxies with faint black holes Bright black holes without visible galaxies

Results were from comparing Chandra data to deep optical surveys from Keck


CGRO/EGRET dataCGRO/EGRET data

30-40% of gamma-ray background is unresolved and extragalactic in origin


Gamma-ray Gamma-ray Background Background

Simulated sky as seen by GLAST after 1 year of observation Key goal to determine if extra-galactic gamma-radiation is from discrete sources


Backgrounds in the Backgrounds in the UniverseUniverse Cosmic Microwave Background – Cosmic Microwave Background –

cooling relic of the Big Bangcooling relic of the Big Bang Infrared – faint stars in distant Infrared – faint stars in distant

galaxies and nearby dusty stars galaxies and nearby dusty stars Visible – local zodiacal lightVisible – local zodiacal light Ultraviolet – still to be measuredUltraviolet – still to be measured X-ray – unresolved distant black X-ray – unresolved distant black

holes in galaxy coresholes in galaxy cores Gamma-ray – probably similar to X-Gamma-ray – probably similar to X-

rayray


Modeling the UniverseModeling the Universe Spend about 30 minutes building a Spend about 30 minutes building a

model of the Universe with a partnermodel of the Universe with a partner You may also do just a part of the You may also do just a part of the

Universe, such as the solar system or a Universe, such as the solar system or a galaxygalaxy

What features of the Universe does What features of the Universe does your model represent? Misrepresent?your model represent? Misrepresent?

What things have you left out entirely?What things have you left out entirely? What questions came up as you built What questions came up as you built

this model in your group?this model in your group?


Web ResourcesWeb Resources Astronomy picture of the DayAstronomy picture of the Day

http://antwrp.gsfc.nasa.gov/apod/astropix.htmlhttp://antwrp.gsfc.nasa.gov/apod/astropix.html Imagine the UniverseImagine the Universe

http://imagine.gsfc.nasa.govhttp://imagine.gsfc.nasa.gov On-line Journey through Astronomy On-line Journey through Astronomy

http://csep10.phys.utk.edu/astr162/lect/gclusters/attracthttp://csep10.phys.utk.edu/astr162/lect/gclusters/attractor.htmlor.html

Space Telescope Science InstituteSpace Telescope Science Institute http://stsci.eduhttp://stsci.edu

GLAST project outreach web site http://glast.sonoma.edu

Chandra X-ray Background Results http://chandra.harvard.edu/press/00_releases/press_011400bg.html


Web ResourcesWeb Resources On-line Journey through AstronomyOn-line Journey through Astronomy

http://csep10.phys.utk.edu/astr162/lect/gclusters/attractor.htmlhttp://csep10.phys.utk.edu/astr162/lect/gclusters/attractor.html

J. C. Evans Astronomy 103 CourseJ. C. Evans Astronomy 103 Course http://www.physics.gmu.edu/classinfo/astr103/Courshttp://www.physics.gmu.edu/classinfo/astr103/CourseNotes/Html/Lec08/Lec08_pt1_universeClusters.htmeNotes/Html/Lec08/Lec08_pt1_universeClusters.htm

Martin White’s Large Scale StructureMartin White’s Large Scale Structure http://astron.berkeley.edu/~mwhite/probes-lss.htmlhttp://astron.berkeley.edu/~mwhite/probes-lss.html

XMM-Newton Large Scale Structure SurveyXMM-Newton Large Scale Structure Survey http://vela.astro.ulg.ac.be/themes/spatial/xmm/LSS/First/FMos/index_e.htmlhttp://vela.astro.ulg.ac.be/themes/spatial/xmm/LSS/First/FMos/index_e.html

J. Cohn’s Lyman alpha Forest pages http://astron.berkeley.edu/~jcohn/lya.html


Web ResourcesWeb Resources

T-6 Group at LANL animations and picture http://qso.lanl.gov/pictures/Pictures.html

John Dubinski’s Big cluster simulations http://www.cita.utoronto.ca/~dubinski/bigcluster.html

2DF redshift survey project http://www.2dfquasar.org/

Ben Moore’s N-body simulations

http://star-www.dur.ac.uk/~moore/movies.html


Web ResourcesWeb Resources Ned Wright’s ABCs of Distance and CMIRB http://www.astro.ucla.edu/~wright/distance.htm http://www.astro.ucla.edu/~wright/CIBR/

Ray White’s Cluster of Galaxies Mug Shots http://www.astr.ua.edu/white/mug/cluster/clusters.html

Cambridge Cosmology Pages http://www.damtp.cam.ac.uk/user/gr/public/gal_lss.html

Jimmy Imamura Lecture: http://zebu.uoregon.edu/~imamura/123/lecture-1/size.html

Greg Bothun’s Cosmology Book http://nedwww.ipac.caltech.edu/level5/Bothun2/Bothun_contents.html

Documents

Astronomy 305/Frontiers in Astronomy