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Compact Steep-Spectrum and Gigahertz Peaked-Spectrum Radio Sources

Compact Steep-Spectrum and Gigahertz Peaked-Spectrum Radio Sources. Reviews: O’Dea 1998 PASP 110:493 Third Workshop on CSS/GPS Radio Sources 2003 PASA Vol. 20, No. 1. Background. c.f. Rybicki & Lightman’s Radiative Processes.

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Compact Steep-Spectrum and Gigahertz Peaked-Spectrum Radio Sources

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

  2. Background c.f. Rybicki & Lightman’s Radiative Processes Synchrotron Radiation: relativistic electrons in B-field If the electrons have a power law spectra index in energy, p Then the spectrum is a power law with spectral index α Perpendicular to B-field Polarization:

  3. Synchrotron Self-Absorption Photon interacts with an electron in a B-field and is absorbed, giving up its energy to the electron Free-free also 5/2 Rybicki&Lightman

  4. 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

  5. FR II

  6. FR I Cen A Outer radio lobes Inner radio:

  7. 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

  8. O’Dea 1998

  9. Spectral shape and Lifetimes Radio sources “age”  spectrum steepens Energy loss from radiation, adiabatic expansion Electron lifetime Break freq. Equivalent magnetic field of the microwave background 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

  10. Snapshot of evolutionary sequence? O’Dea 1998

  11. 21-cm absorption Pihlstrom+ 2003 A&A 404, 871 Vermeulen+ 2003 A&A 404, 861

  12. ~50% of GPS+CSS sources show 21-cm absorption Compared to < 10% for ellipticals Smaller sources (<0.5 kpc) have larger H I columns than Larger (>0.5 kpc) sources Model absorbing gas  10^8 solar masses, not enough to “smother” jets GPS/CSS sources: gas-rich ellipticals from mergers

  13. Host Galaxies deVries+ 1997 ApJS 110, 191 Labiano+ astro-ph/0701619 Ellipticals; evidence for mergers

  14. Sub-luminal expansion on VLBI scales Polatidis & Conway 2003 PASA 20, 69-74 Blobs expanding With v ~ 0.2 c Kinematic ages: very young

  15. 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 Color: X-ray Contour: radio • Bechtold + 2001 ApJ 562, 133 • Siemiginowska+ 2002 ApJ 570, 543 • Blazejowski+ 2004, ApJ 600 L27

  16. 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

  17. Dentist Drill model Bicknell+1997 ApJ, 485, 112 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.

  18. 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?

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