Arecibo as a redshift machineArecibo as a redshift machine

Perseus-Pisces SuperclusterPerseus-Pisces Supercluster

~11,000 galaxy redshifts:

[Giovanelli, Haynes et al. 1980s]

Perseus-Pisces SuperclusterPerseus-Pisces Supercluster

Two SloanDigital Sky Survey (SDSS)Wedges nearThe equator.

67676 galaxiesWithin 5deg ogEquator[Tegmark et al 2003]

Morphological ClassificationMorphological Classification

Elliptical vs SpiralElliptical vs SpiralGalaxies can be classified based on appearance

EllipticalsEllipticals SpiralsSpirals

Smooth falloff of lightSmooth falloff of light Bulge+disk+armsBulge+disk+arms

Not forming stars nowNot forming stars now Lots of star formationLots of star formation

Dominant motion: Dominant motion: random orbitsrandom orbits

Dominant motion: Dominant motion: circular orbits in diskcircular orbits in disk

Prefer cluster coresPrefer cluster cores Avoid cluster coresAvoid cluster cores

Quantitative MorphologyQuantitative MorphologyPhotometric surface

brightness profile

“de Vaucouleurs’ profile”:I(r)= I(re) exp[-(r/re)¼]

where re is the “effective radius” and L(<re)=½ Ltotal

“exponential profile”:I(r)= I(0) exp[-r/rd]

where rd is the “exponential scale length”.Works for spiral disks

Works for ellipticals and for bulges

Integrated Galaxy SpectraIntegrated Galaxy Spectra

MgI MgI

HH

Ellipticals show absorption line spectra characteristic of older stellar population; spirals show emission lines, characteristic of star-formation

regions.

Galaxy ExoticaGalaxy Exotica

The AntennaeThe Antennae

Toomre & Toomre 1972Toomre & Toomre 1972Restricted 3-body

problem

Haynes, Giovanelli & Roberts 1979 Arecibo data

NGC 3628

NGC 3623NGC 3627

Leo TripletLeo Triplet

Morphological Distortions Resulting from Gravitational Interaction: Example # 1

A ComputerSimulation of theMerger of twoSpiral galaxies

Morphology-Density Morphology-Density RelationRelation

The fraction of the population that is spiral decreases from the field to

high density regions. [Dressler 1980]

High Low

Ellipticals

S0Spirals/Irr

Virgo ClusterVirgo Cluster

HI DeficiencyHI Deficiency

HI Disk DiameterHI Disk Diameter

[Giovanelli & Haynes 1983]

Arecibo dataArecibo data

Morphological Alteration Morphological Alteration MechanismsMechanisms

I. Environment-independenta. Galactic windsb. Star formation without replenishment

II. Environment dependent a. Galaxy-galaxy interactions

i. Direct collisionsii. Tidal encountersiii. Mergers

b. Galaxy-cluster medium i. Ram pressure stripping ii. Thermal evaporationiii. Turbulent viscous stripping

Disk Formation: a primerDisk Formation: a primer

The spin parameter l quantifies theThe spin parameter l quantifies thedegree of rotational support of a system :degree of rotational support of a system :

For E galaxies, l ~ 0.05For E galaxies, l ~ 0.05 For S galaxies, l ~ 0.5For S galaxies, l ~ 0.5

Angular momentumMass

Total Energy

• Protogalaxies acquire angular momentum through tidal torques Protogalaxies acquire angular momentum through tidal torques with nearest neighbors during the linear regime with nearest neighbors during the linear regime [Stromberg 1934; Hoyle 1949]

• As self-gravity decouples the protogalaxy from the Hubble flow, As self-gravity decouples the protogalaxy from the Hubble flow, [l/(d l/d t)] becomes v.large and the growth of l ceases[l/(d l/d t)] becomes v.large and the growth of l ceases

• N-body simulations show that at turnaround time N-body simulations show that at turnaround time values of l range between 0.01 and 0.1, for halos of values of l range between 0.01 and 0.1, for halos of all massesall masses• The average for halos isThe average for halos is l = 0.05l = 0.05 • Only 10% of halos haveOnly 10% of halos have l < 0.025l < 0.025 or or l > 0.10l > 0.10• halos achieve very halos achieve very modest rotational supportmodest rotational support• Baryons collapse dissipatively within the Baryons collapse dissipatively within the potential well of their halo. They lose energy potential well of their halo. They lose energy through radiative losses, largely conserving through radiative losses, largely conserving mass and angular momentummass and angular momentum• Thus Thus l of disksl of disks increases, as they shrink to increases, as they shrink to the inner part of the halothe inner part of the halo.

[Fall & Efstathiou 1980][Fall & Efstathiou 1980](mass of disk) /(total mass)

•If the galaxy retains all baryons If the galaxy retains all baryons m_d~1/10 , and l_disk grows to ~ 0.5, m_d~1/10 , and l_disk grows to ~ 0.5, • R_disk ~ 1/10 R_hR_disk ~ 1/10 R_h

Some galaxies formthrough multiple (andoften major) mergers

The orbits of theirconstituent stars arerandomly oriented

Kinetic energy of randommotions largely exceedsthat of orderly, large-scale motions such asrotation.

These galaxies have low “spin parameter”

Elliptical galaxiesElliptical galaxies

Other galaxies formin less crowdedenvironments

They accrete materialat a slower pace andare unaffected by major mergers for long intervals of time

Baryonic matter (“gas”)collapses slowly (anddissipatively – losingenergy) within thepotential well of Darkmatter, forming a disk

Baryonic matter hashigh spin parameter:large-scale rotationis important

Spiral GalaxySpiral Galaxy

Scaling Laws for Disks Scaling Laws for Disks * For a disk mass fraction

* If the disk mass assumes an exponential distribution

* and if the disk angular momentum fraction is

then

[see Mo et al 1998; ; Dalcanton et al. 1997; Firmani & Avila-Reese 2000]

Scaling Laws for Scaling Laws for Disks Disks

When a more realistic density profile is adopted (e.g. NFW), the scaling relations When a more realistic density profile is adopted (e.g. NFW), the scaling relations of disks become:of disks become:

Where are dimensionless parameters of order 1, that take intoWhere are dimensionless parameters of order 1, that take intoaccount respectively the degree of concentration of the halo, the shape of account respectively the degree of concentration of the halo, the shape of the rotation curve and the radius at which it is measuredthe rotation curve and the radius at which it is measured.

Scale-length—Velocity WidthScale-length—Velocity Width

SFI and SFI+ samples:-I band CCD photometry-Sbc-Sc spirals-cz < 10000 km/s-HI and H spectroscopySFI : Giovanelli, Haynes, da Costa, Freudling, Salzer, Wegner 1600 galaxies

SFI++ : Haynes & Giovanelli 4500 galaxies

Central Disk Surface Brightness—Velocity WidthCentral Disk Surface Brightness—Velocity Width

“Visibility” function

Expected slope fromScaling law

TF Relation: DataTF Relation: Data

SCI : cluster Sc sampleI band, 24 clusters, 782 galaxies

[Giovanelli et al. 1997]

“Direct” slope is –7.6“Inverse” slope is –7.8

…which is similar to the explicittheory-derived dependence = 3

[Where L L (rot. vel.) (rot. vel.) ]

The MW galaxyThe MW galaxy

The Milky Way as a naked eye object

The Near Infrared Sky

408 MHz

2.7GHz

HI (21 cm)

CO

FIR (IRAS)

MIR (6-10m)

NIR (1.2-3.5 m)

Optical

X-ray(0.25-1.5KeV)

Gamma (300 MeV)

Multiwavelength Milky Way

Galactic ComponentsGalactic Components

Spiral Structure in the Milky WaySpiral Structure in the Milky WayThe Sun is locatedon the inner side ofa spiral arm, at theperiphery of theGalaxy

Spiral arms are traced by “young” objects: recently formed stars,gas and dust

Spiral structure is a wave-like phenomenon: the wave travels through the material contentsof the galaxy, as a wave travelsacross the surface of the ocean.

MotionsMotions

Spheroidal components (bulge, halo): random motions around the Galactic Center

Disk rotates differentially• circular motion in the disk• V(R) ~ 220 km/s

Milky Way Rotation CurveMilky Way Rotation Curve Dark Matteris needed toexplain theMilky Waydynamics

The fractionalcontribution of the Dark Matter to the total mass contained within a given radius increasesoutwards

The total massof the Galaxyis dominated byDark Matter

The Local Group of GalaxiesThe Local Group of Galaxies

• Includes ~35 galaxies• MW & M31 are dominant• Mostly dwarfs which

cluster around giants

http://www.anzwers.org/free/universe/virgo.html

The Magellanic CloudsThe Magellanic Clouds

LMC SMC

• The Magellanic Clouds are contained within a common HI envelope.

• The Magellanic Stream traces their interaction with the MW.

Substructure in the Local GroupSubstructure in the Local Group

Diagram from Sarah Maddison

Giant spiralsdSph (+dEll)dIrrdIrr/dSph

High Velocity CloudsHigh Velocity Clouds

Credit: B. Wakker

?

The Magellanic StreamThe Magellanic Stream

Discovered in 1974 byMathewson, Cleary & Murray Putman et al. 2003

The Galactic CenterThe Galactic Center

The Centerof theMilky Way

The Inner Halfkpc (4x3 deg) of the MWat = 90 cm(330 MHz)

The Galactic Center: Radio The Galactic Center: Radio FilamentsFilaments

Filaments disk are produced by nonthermal emission. Structure is regulated by ordered magnetic fields

20 cm map of inner 30 pc

Core is thermal, fed by young stars.

Infrared ObservationsInfrared Observations

• At 2.2 m: direct stellar emission from cooler stars (types K & M) that coexist in clusters with the hotter ones that heat the HII regions.

• At 10 m: emission from dust which is heated by higher energy (optical) photons emitted by stars and then re-emits in the IR.

• At 100 m, emission due to cooler dust, more extended, heated by energetic photons from hot stars over 10’s of parsecs distant.

At optical wavelengths, the view is obscured.

Galactic Center: NIR Galactic Center: NIR imageimage

The stellar density in the Galactic Center is 300,000 X that of the solar neighborhood.

http://www.gemini.edu/gallery/observing/density.html

The Galactic Center: NIR mosaicThe Galactic Center: NIR mosaic

• Mosaic of J,H,K (1.2 to 3.5 ) images of the GC region. blue= “hot” red= “cool”

The two yellow arrows mark the position of SgrA*

Young stellar clusters in the GCYoung stellar clusters in the GC

• The young stellar clusters in the GC are truly remarkable for their population of high mass stars

• Central cluster: located within the central pc. Contains over 30 massive stars; age ~ 3 to 5 Myr;

Moves with SgrA* to within 70 km/s

• Arches cluster: within 30 pc, contains > 150 O stars within 0.6 pc radius; very high density;

Age ~2.5 ±0.5 Myr (younger).

• Quintuplet cluster: also within 30 pc of center. > 30 massive stars; age ~ 3 to 5 Myr.

Young, massive, high density

Extreme EnvironmentExtreme Environment

•High density ~ 3 x 105 M pc-3

•Strong tidal forces•Clusters disrupted in < 10 to 50 Myr

The Galactic Center: Radio The Galactic Center: Radio FilamentsFilaments

Filaments disk are produced by nonthermal emission. Structure is regulated by ordered magnetic fields

20 cm map of inner 30 pc

Core is thermal, fed by young stars.

The Sgr A ComplexThe Sgr A Complex

Baganoff et al 2003 ApJ 591, 91

•Schematic diagram of the main components of the SgrA radio complex.

•Note the radio mini-spiral.

•The SMBH candidate SgrA* is located at the center of the cavity within the molecular disk. The ionized gas and hot massive stars also lie within this disk.

•SgrA West = HII region SgrA East = SNR?

Radio continuum “Mini-spiral”Radio continuum “Mini-spiral”Core source: inner 3 pc Sgr A

Thermal emission from young stars

Sgr A*:compact nonthermal

radio sourceUnusual time-variable

511 keV e- - e+ annihilation radiation

Molecular diskMolecular disk

• HCN traces high density gas. This ring appears to be the inner edge of a thin molecular structure extending out to about 5 to 7 pc from the center.Within this ring, we find the “mini-spiral”.

• HCN synthesis data reveal a highly inclined clumpy ring of molecular gas surrounding the

ionized central 2 pc.

HCN map made with BIMA array. Blue contours show the radio mini spiral.

Sgr A*: the compact radio Sgr A*: the compact radio sourcesource

• SgrA* is a compact radio source projected toward the Galactic center. Its motion can be measured with respect to background extragalactic radio sources. Motion < 20 km/s.

• High resolution observations of the compact radio source show that is 1 A.U. in size.

• While SgrA* is a bright radio continuum source, it is a very dim infrared source.

• Position determined by Reid et al (2003) using VLA/VLBA observations of SiO maser stars with accuracy of 10 mas coincides with center of acceleration of stars to w/in 1310 mas.

The Supermassive Black HoleThe Supermassive Black HoleAt the Galactic Center of theAt the Galactic Center of the Milky WayMilky Way

7 years ofobservationsof stars nearSag A*

Orbits of stars near the Galactic Orbits of stars near the Galactic CenterCenter

Data: UCLA (Ghez et al) and MPE (Genzel et al) groups

Orbit of S0-2 (Schoedel et al 2002)

Star transited through“perinigricon” at 5000 km/s,to within 17 light hoursof central object

The M(r) at the center of the Galaxy is best fitted by the combination of - point source of 2.6+/-0.2 x 106 M_sun - and a cluster of visible stars with a core radius of 0.34 pc and o=3.9x106 M_sun/pc3

Schoedel et al (2002)

SO-2: too young?SO-2: too young?Ghez et al. (2003) ApJL 586, L127

• O8-B0 star, ~15 M, < 10 Myr old, vr = 510 ± 40 km/s• Exists in region of strong tides• Star is behind BH at periastron• Counterrotates with respect to galactic rotation• How can it have formed in such an environment?

Motions of stars near SgrA*Motions of stars near SgrA*Ghez et al. 2000, Nature 407, 349.Ghez et al. 2003, astro/ph-0306130

• Observations now on-going for almost a decade

• Now include 22 stars with proper motions within 0.4” (1.6 pc) of SgrA*

• 8 have orbital solutions (not just observed motions)

• Accelerations pinpoint the location of the responsible mass to within 1.5 mas

• Central “dark” mass of 4.0(±0.03)x106 M within a volume of < 90 A.U. 1000 RSch

The radius of a Black HoleThe radius of a Black Hole Begelman, 2003, Science 300, 1898 Kormendy, 2003, astro-ph/0306353

•The Schwarzschild radius is the radius at which the escape

velocity equals the speed of light.•The surface of the sphere of

radius equal to the Schwarzschild radius is called the “event

horizon”. We on the outside of the black hole cannot learn

anything about any event taking place within the event horizon,

and thus we can think of it as the "surface" of the black hole. ~5 to 20 M = stellar BH

~1000 M(?) = IMBH106 to 108 M= SMBH

The Schwarzschild radius is RSS = 2 G M / c = 2 G M / c22

i.e. 3 km times the mass expressed in solar units

The radius of a SMBH at the center of ourGalaxy, with mass near 3 million solar masses,has a radius of ~ 10 million km, or 1/15 A.U.

At the distance of 8.5 kpc, the radius of theSMBH subtends an angle of 8 as

Examples of SMBHs in other Galaxies

M31 and M32:M31 and M32:

M32

M31 - Andromeda

In both cases, evidence for a SMBH

The SMBH in M32The SMBH in M32

M87 in the Virgo ClusterM87 in the Virgo Cluster

M87: the radio jetM87: the radio jet

M87 – a jet on all M87 – a jet on all scalesscales

The jet connects the SMBH to the outer parts of the source, supplying the radio source and the surrounding region with energy and relativistic plasma.

Extent of 2 cm map ~2 kpc 18 cm VLBI ~ 17pc 1.3cm VLBI ~ 2.5pcCore source ~ 0.1pc ~ 100RS

The nearby spiral galaxy NGC 4258exhibits the best evidence for thepresence of a SMBH at the core ofan external galaxy.

The evidence is based on VLBIobservations of H2O (water) masersources, the proper motions andaccelerations of which have beendetected and used to infer themass and the geometry of thegalaxy’s nucleus.

The nucleus of NGC 4258(a.k.a. M106) is also knownto be an X-ray source,and optical spectroscopyindicate that the galaxynucleus is a Seyfert 2.

The AGN characteristics(X-ray and optical nuclear activity ) of NGC 4258,As in other AGNs, arethought to arise from gasin the vicinity of a central,SMBH, forming anaccretion disk which givesrise to the high energyPhenomena.

Artist’s rendition of a moleculargas disk, 0.5 l.y. in radius, near thecenter of NGC 4258.

The inner parts of the disk arehotter and correspond to thesource of high energy emissionby the AGN. Perpendicular tothe axis of the disk, a jet ofrelativistic particles is ejected.

Water maser sources in themolecular disk have been detectedand their motions tracked overseveral years via VLBI observationsat = 1 cm

Their motions (at speeds of orderof 1000 km/s, proper motions ofabout 35 asec per yr) indicatean enclosed mass for the SMBHof MBH = 3.5x107 M_sun

placed at the black spot in the fig.

The lower image representssynchrotron radiation at a wavelength of 20 cm, showingextended “anomalous spiral arms”(which do not coincide with thespiral arms seen in the opticalimage of the galaxy).Those features are thought tobe the extension of the jetproduced at the center of theaccretion disk in the AGN.

Jets are commonly observed at radiowavelengths: evidence of AGN

3C31 VLA

3C296 VLA

3C288 VLA

3C120 VLA (C. Walker)

More Jets...

… sometimes one-sided

Quasars, Seyferts and other AGNs

• “Quasars” were first discovered in the early 1960s, when it was realized that some bright radio sources coincided in position with optically star-like objects (Hazard, MacKey & Shimmins 1963; Matthews & Sandage 1963) : QUASAR = QUASi stAR • In 1963, M. Schmidt noticed that the spectrum of 3C273, a Quasar, indicated a redshit displacement of spectral lines of z=0.158

• Since then, quasars have been discovered at progressively larger z; as of mid-2003, the highest z quasar are at z ~ 6.5

• In 1943, C. Seyfert identified a class of galaxies with strong, high excitation optical, often very broad emission lines. In the 1950s, strong radio emission was detected from these objects.

• Quasars, Seyferts and other objects with analogous properties are now commonly referred with the term “ACTIVE GALACTIC NUCLEI”: AGNs The nuclear activity is thought to be associated with the presence of a Supermassive Black Hole at the nucleus of a galaxy

Quasar/AGN variabilityQuasar/AGN variabilityBrightest AGNs: L ~ 1012 - 1015 L

AGNs are sometimes observed to vary on timescales of a few days to months

A SMBH’s variability is an indication of its size.

t1 t2 Time

inte

nsity

d 2r

Flux begins to increase when the light from the near side reaches the observer, at t1=d/c.Flux returns to quiescent level when the light

from the far side arrives, at t2=(d+2r)/c

So, the size of the emission region is

2r = (t2- t1)/c

The brightest AGNs produce many times the emission of a whole galaxy from regionssmaller than the Solar System