Arecibo as a redshift machine Perseus-Pisces Supercluster ~11,000 galaxy redshifts: [Giovanelli, Haynes et al. 1980s]

Perseus-Pisces Supercluster

Two Sloan Digital Sky Survey (SDSS) Wedges near The equator galaxies Within 5deg og Equator [Tegmark et al 2003]

Morphological Classification

Elliptical vs Spiral Galaxies can be classified based on appearance EllipticalsSpirals Smooth falloff of light Bulge+disk+arms Not forming stars now Lots of star formation Dominant motion: random orbits Dominant motion: circular orbits in disk Prefer cluster cores Avoid cluster cores

Quantitative Morphology Photometric surface brightness profile “de Vaucouleurs’ profile”: I(r)= I(r e ) exp[-(r/r e ) ¼ ] where r e is the “effective radius” and L(<r e )=½ L total “exponential profile”: I(r)= I(0) exp[-r/r d ] where r d is the “exponential scale length”. Works for spiral disks Works for ellipticals and for bulges

Integrated Galaxy Spectra MgI HH HH Ellipticals show absorption line spectra characteristic of older stellar population; spirals show emission lines, characteristic of star-formation regions.

Galaxy Exotica

The Antennae

Toomre & Toomre 1972 Restricted 3-body problem

Haynes, Giovanelli & Roberts 1979 Arecibo data NGC 3628 NGC 3623 NGC 3627 Leo Triplet

Morphological Distortions Resulting from Gravitational Interaction: Example # 1

A Computer Simulation of the Merger of two Spiral galaxies

Morphology-Density Relation The fraction of the population that is spiral decreases from the field to high density regions. [Dressler 1980] High  Low  Ellipticals S0 Spirals/Irr

Virgo Cluster HI Deficiency HI Disk Diameter [Giovanelli & Haynes 1983] Arecibo data

Morphological Alteration Mechanisms I. Environment-independent a. Galactic winds b. Star formation without replenishment II. Environment dependent a. Galaxy-galaxy interactions i.Direct collisions ii.Tidal encounters iii.Mergers b. Galaxy-cluster medium i. Ram pressure stripping ii. Thermal evaporation iii. Turbulent viscous stripping

Disk Formation: a primer The spin parameter l quantifies the degree of rotational support of a system : For E galaxies, l ~ 0.05 For E galaxies, l ~ 0.05 For S galaxies, l ~ 0.5 For S galaxies, l ~ 0.5 Angular momentum Mass Total Energy Protogalaxies acquire angular momentum through tidal torques with nearest neighbors during the linear regime Protogalaxies acquire angular momentum through tidal torques with nearest neighbors during the linear regime [Stromberg 1934; Hoyle 1949] As self-gravity decouples the protogalaxy from the Hubble flow, [l/(d l/d t)] becomes v.large and the growth of l ceases As self-gravity decouples the protogalaxy from the Hubble flow, [l/(d l/d t)] becomes v.large and the growth of l ceases N-body simulations show that at turnaround time values of l range between 0.01 and 0.1, for halos of all masses N-body simulations show that at turnaround time values of l range between 0.01 and 0.1, for halos of all masses The average for halos is l = 0.05 The average for halos is l = 0.05 Only 10% of halos have l 0.10 Only 10% of halos have l 0.10 halos achieve very halos achieve very modest rotational support modest rotational support Baryons collapse dissipatively within the potential well of their halo. They lose energy through radiative losses, largely conserving mass and angular momentum Baryons collapse dissipatively within the potential well of their halo. They lose energy through radiative losses, largely conserving mass and angular momentum Thus l of disks increases, as they shrink to the inner part of the halo Thus l of disks increases, as they shrink to the inner part of the halo. [Fall & Efstathiou 1980] [Fall & Efstathiou 1980] (mass of disk) /(total mass) If the galaxy retains all baryons  m_d~1/10, and l_disk grows to ~ 0.5,If the galaxy retains all baryons  m_d~1/10, and l_disk grows to ~ 0.5, R_disk ~ 1/10 R_h R_disk ~ 1/10 R_h

Some galaxies form through multiple (and often major) mergers The orbits of their constituent stars are randomly oriented Kinetic energy of random motions largely exceeds that of orderly, large- scale motions such as rotation. These galaxies have low “spin parameter” Elliptical galaxies

Other galaxies form in less crowded environments They accrete material at a slower pace and are unaffected by major mergers for long intervals of time Baryonic matter (“gas”) collapses slowly (and dissipatively – losing energy) within the potential well of Dark matter, forming a disk Baryonic matter has high spin parameter: large-scale rotation is important Spiral Galaxy

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 Disks When a more realistic density profile is adopted (e.g. NFW), the scaling relations of disks become: Where are dimensionless parameters of order 1, that take into account respectively the degree of concentration of the halo, the shape of the rotation curve and the radius at which it is measured the rotation curve and the radius at which it is measured.

Scale-length—Velocity Width SFI and SFI+ samples: -I band CCD photometry -Sbc-Sc spirals -cz < km/s -HI and H  spectroscopy SFI : Giovanelli, Haynes, da Costa, Freudling, Salzer, Wegner 1600 galaxies SFI++ : Haynes & Giovanelli 4500 galaxies

Central Disk Surface Brightness—Velocity Width “Visibility” function Expected slope from Scaling law

TF Relation: Data SCI : cluster Sc sample I band, 24 clusters, 782 galaxies [Giovanelli et al. 1997] “Direct” slope is –7.6 “Inverse” slope is –7.8 …which is similar to the explicit theory-derived dependence  = 3 L  (rot. vel.) [Where L  (rot. vel.) ] 

The 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 ( m) Optical X-ray( KeV) Gamma (300 MeV) Multiwavelength Milky Way

Galactic Components

Spiral Structure in the Milky Way The Sun is located on the inner side of a spiral arm, at the periphery of the Galaxy 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 contents of the galaxy, as a wave travels across the surface of the ocean.

Motions 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 Curve  Dark Matter is needed to explain the Milky Way dynamics  The fractional contribution of the Dark Matter to the total mass contained within a given radius increases outwards  The total mass of the Galaxy is dominated by Dark Matter

The Local Group of Galaxies Includes ~35 galaxies MW & M31 are dominant Mostly dwarfs which cluster around giants

The 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 Group Diagram from Sarah Maddison Giant spirals dSph (+dEll) dIrr dIrr/dSph

High Velocity Clouds Credit: B. Wakker ?

The Magellanic Stream Discovered in 1974 by Mathewson, Cleary & Murray Putman et al. 2003

The Galactic Center

The Center of the Milky Way

The Inner Half kpc (4x3 deg) of the MW at = 90 cm (330 MHz)

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

The 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 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 Environment High density ~ 3 x 10 5 M  pc -3 Strong tidal forces Clusters disrupted in < 10 to 50 Myr

The Galactic Center: Radio Filaments 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 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” Core source: inner 3 pc Sgr A Thermal emission from young stars Sgr A*: compact nonthermal radio source Unusual time-variable 511 keV e - - e + annihilation radiation

Molecular 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 source 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 13  10 mas.

The Supermassive Black Hole At the Galactic Center of the Milky Way Milky Way

7 years of observations of stars near Sag A*

Orbits of stars near the Galactic Center 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 hours of 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 10 6 M_sun - and a cluster of visible stars with a core radius of 0.34 pc and  o =3.9x10 6 M_sun/pc 3 Schoedel et al (2002)

SO-2: too young? Ghez et al. (2003) ApJL 586, L127 O8-B0 star, ~15 M , < 10 Myr old, v r = 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* Ghez et al. 2000, Nature 407, 349. Ghez et al. 2003, astro/ph 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)x10 6 M  within a volume of < 90 A.U.  1000 R Sch

The radius of a Black Hole Begelman, 2003, Science 300, 1898 Kormendy, 2003, astro-ph/ 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  (?) = IMBH 10 6 to 10 8 M  = SMBH

S = 2 G M / c 2 The Schwarzschild radius is R S = 2 G M / c 2 i.e. 3 km times the mass expressed in solar units The radius of a SMBH at the center of our Galaxy, 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 the SMBH subtends an angle of 8  as

Examples of SMBHs in other Galaxies

M31 and M32: M32 M31 - Andromeda In both cases, evidence for a SMBH

The SMBH in M32

M87 in the Virgo Cluster

M87: the radio jet

M87 – a jet on all scales 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 ~ 2.5pc Core source ~ 0.1pc ~ 100R S

The nearby spiral galaxy NGC 4258 exhibits the best evidence for the presence of a SMBH at the core of an external galaxy. The evidence is based on VLBI observations of H 2 O (water) maser sources, the proper motions and accelerations of which have been detected and used to infer the mass and the geometry of the galaxy’s nucleus.

The nucleus of NGC 4258 (a.k.a. M106) is also known to be an X-ray source, and optical spectroscopy indicate that the galaxy nucleus is a Seyfert 2. The AGN characteristics (X-ray and optical nuclear activity ) of NGC 4258, As in other AGNs, are thought to arise from gas in the vicinity of a central, SMBH, forming an accretion disk which gives rise to the high energy Phenomena.

Artist’s rendition of a molecular gas disk, 0.5 l.y. in radius, near the center of NGC The inner parts of the disk are hotter and correspond to the source of high energy emission by the AGN. Perpendicular to the axis of the disk, a jet of relativistic particles is ejected. Water maser sources in the molecular disk have been detected and their motions tracked over several years via VLBI observations at  = 1 cm Their motions (at speeds of order of 1000 km/s, proper motions of about 35  asec per yr) indicate an enclosed mass for the SMBH of M BH = 3.5x10 7 M_sun placed at the black spot in the fig.

The lower image represents synchrotron radiation at a wavelength of 20 cm, showing extended “anomalous spiral arms” (which do not coincide with the spiral arms seen in the optical image of the galaxy). Those features are thought to be the extension of the jet produced at the center of the accretion disk in the AGN.

Jets are commonly observed at radio wavelengths: evidence of AGN 3C31 VLA

3C296VLA 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 variability Brightest AGNs: L ~ 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. t1t1 t2t2 Time  intensity d2r Flux begins to increase when the light from the near side reaches the observer, at t 1 =d/c. Flux returns to quiescent level when the light from the far side arrives, at t 2 =(d+2r)/c So, the size of the emission region is 2r = (t 2 - t 1 )/c The brightest AGNs produce many times the emission of a whole galaxy from regions smaller than the Solar System 