Compact Steep-Spectrumand

Gigahertz Peaked-SpectrumRadio Sources

Reviews: O’Dea 1998 PASP 110:493 Third Workshop on CSS/GPS Radio Sources 2003 PASA Vol. 20, No. 1

Background

2

1

p

F

Synchrotron Radiation: relativistic electrons in B-field

If the electrons have a power law spectra index in energy, pThen the spectrum is a power law with spectral index α

37

1

p

p

c.f. Rybicki & Lightman’s Radiative Processes

Polarization: Perpendicular to B-field

Synchrotron Self-Absorption

2/5

jS

Photon interacts with an electron in a B-field and is absorbed, giving up its energy to the electron

Rybicki&Lightman

Free-free also 5/2

FR I vs. FR II

On large scales (>15 kpc)

radio sources divide into

Fanaroff-Riley Class I, II

(Fanaroff & Riley 1974 MNRAS 167 31P)

FRI: Low luminosity

edge dark

Ex.:Cen-A

FRII: High luminosity

hot spots on outer edge

Ex. Cygnus A

FR II

FR I Cen A

Inner radio:

Outer radio lobes

On small scales (< 15 kpc): 3 types of sources

Compact, Flat Spectrum (CFS) usually < 1”, physically small < 10 pc fν~ν-α, α~0 – 0.3 variable, polarized, superluminal on VLBI scales

Compact, steep spectrum (CSS) alpha = 0.7 – 1.2 sizes 1-20 kpc (within host galaxy) peak at < 500 MHz (limited by Ionospheric cutoff is at 10 MHz) 30% of cm-selected radio sources GigaHertz Peaked Spectrum (GPS) radio spectrum peaks at 500 MHz to 10 GHz sizes < 1 kpc (within NLR) not very polarized alpha ~0.77 for E>E(peak) 10% of cm-selected radio sources

Bicknell + 1997 ApJ 485, 112

O’Dea 1998

Spectral shape and Lifetimes Radio sources “age” spectrum steepens Energy loss from radiation, adiabatic expansion

yrzBB

Bt b

R

2/1

22

2/14 )1(106.2

Electron lifetime

Break freq.

Equivalent magnetic field of the microwavebackground

Van der Laan & Perola 1969

GPS: B=10-3 G, nu_b=100 GHz t=2000 years 100 Mhz t=70,000 years

CSS: B=10-4 G, nu_b=100 GHz t=70,000 years 100 MHz t=2 million years

O’Dea 1998

Snapshot ofevolutionarysequence?

21-cm absorption

Pihlstrom+ 2003 A&A 404, 871Vermeulen+ 2003 A&A 404, 861

~50% of GPS+CSS sources show 21-cm absorptionCompared to < 10% for ellipticalsSmaller sources (<0.5 kpc) have larger H I columns thanLarger (>0.5 kpc) sources

Model absorbing gas 10^8 solar masses, not enough to “smother” jets

GPS/CSS sources: gas-rich ellipticals from mergers

Host Galaxies deVries+ 1997 ApJS 110, 191Labiano+ astro-ph/0701619

Ellipticals; evidence for mergers

Sub-luminal expansion on VLBI scales

Polatidis & Conway 2003 PASA 20, 69-74

Blobs expandingWith v ~ 0.2 c

Kinematic ages: very young

X-rays

Chandra Cycle 1: Observations of GPS z=1 qso PKS 1127-11 discovered X-ray jet, 300 kpc long (projected) + deep VLA

lifetime > 3 Myrs

Bechtold + 2001 ApJ 562, 133Siemiginowska+ 2002 ApJ 570, 543Blazejowski+ 2004, ApJ 600 L27

Color: X-rayContour: radio

Survey of GPS quasars with Chandra X-ray Observatory Siemiginowska+ 2007, ApJ submitted

No other jets

One quasar has detected X-ray cluster of galaxies

Not Compton thick

Two with X-ray absorption have very high column, intervening DLYAs

Dentist Drill model

FIG. 1.—Illustration of the interaction of a jet-fed radio lobe with the dense interstellar medium. The radiative bow shock (dashed line) surrounding the radio lobe collisionally excites the ISM which is shown here as a two-phase medium permeated by dense clouds shown in light gray. The radiation from the shock also photoionizes clouds (medium gray) in the ISM in advance of the bow shock. The shocked clouds are shown as dark gray. When the ionized gas enveloping the radio lobe is sufficiently dense it can free-free absorb the radio emission at GHz frequencies. The ionized medium also forms a Faraday screen which depolarizes the radio emission.

Bicknell+1997 ApJ, 485, 112

Summary: GPS & CSS Radio Sources

•Very luminous cores

•Young or smothered (“frustrated”)? ….both?

•Kinematic, spectral age estimates sources ~3000 years old

•Evidence for neutral gas, but is there enough to effect the evolution of the jet?

•Will GPS & CSS sources eventually become low luminosity FR I’s?