Triggering radio galaxies at 0<z<1

1. Triggering radio galaxies at 0<z<1 Elaine M. Sadler • Luminosity functions and stellar populations • New spectroscopic samples at 0<z<1 • High frequency: the AT20G survey [with Russell Cannon, Scott Croom, Tom Mauch, Tara Murphy, Helen Johnston, Paul Hancock & the AT20G, 6dFGS, 2SLAQ, WiggleZ and GAMA survey teams]

2. Radio-source populations at z~0 Local radio-source populations now mapped out in detail from large-area radio + optical surveys Good-quality optical spectra available for >20,000 local radio-emitting galaxies! (2dFGRS/SDSS/6dFGS +NVSS/SUMSS/FIRST)

3. SF Local (z~0) radio LFs for AGN and star-forming galaxies now accurately measured over six orders of magnitude. Sample is large enough to split by MK AGN (Mauch & Sadler 2007) NVSS+6dFGS

4. Fraction of galaxies hosting radio-loud AGN increases with galaxy stellar mass (Auriemma+ 77, Sadler+ 89, Best+ 05) BH duty cycle high in local massive galaxies (Mauch & Sadler 2007)

5. “Post-starburst” radio galaxies 2dFGRS radio galaxy: Balmer abs. lines imply a massive (~1010 Msun) starburst occurred ~0.15 Gyr ago. Compact, steep-spectrum radio source has P1.4 ~ 1025 W/Hz, MK ~ -25. Extremely rare locally! (<0.01% of radio AGN)

6. Stellar populations of radio galaxies at 0.4<z<0.8 • Photometric selection from SDSS, sky area ~150 deg2 • Optical spectra and redshifts from AAT/2dF • 15,000 spectra of luminous red galaxies (LRGs) at 0.4<z<0.8 • 10,000+ faint QSO spectra Survey paper: Cannon et al. (2006) MNRAS 372, 425

7. z=0.5 z=0 First detection of cosmic evolution for low-power radio galaxies.P<1026 W/Hz radio AGN population well-fitted by luminosity evolution of the form (1+z)2. More rapid evolution for powerful sources (Sadler+ 07, Donoso+ 09)

8. SF z 2SLAQ radio galaxies redder (and more clustered: Wake+ 08) than the general LRG population, passively-evolving optical LF.

9. Composite LRG optical spectra 0.45<z<0.5 0.55<z<0.65 Analysed matched composite spectra to test for differences between the stellar populations of radio-loud and radio-quiet 2SLAQ galaxies (Johnston+ 08). 0.65<z<0.85

10. Binned in redshift Binned in radio power (Johnston+08)

11. Stellar populations at z~0.5 Fitted composite spectra with two single-age stellar populations, old (~7 Gyr) plus younger (10 Myr to 5 Gyr). • In general, no difference betweenstellar populations of radio-detected galaxies and full 2SLAQ LRG sample. • Around 30-40% of the light at 4000A comes from intermediate-age stars (~1 Gyr old, <1% by mass). • The most powerful radio galaxies (>1026 W/Hz) have strong emission lines, AND a younger (100 Myr) stellar population.

12. Recent mergers? Rapid evolution like ULIRGS, QSOs. Cold mode? Represent ~ 0.5% of 2SLAQ galaxies at z~0.6 “Optically-quiet” radio galaxies Evolution as (1+z)2, similar to cosmic SF density. Not yet observed beyond z~0.7. FRII FRI Hot mode L*

13. Blue radio galaxies at 0<z<1? • What about the effects of colour selection in LRG samples? • Are we missing a population of blue radio galaxies? • How are are radio galaxies and radio-loud QSOs related? Work in progress: New spectroscopic survey, piggy-backed on AAT large-area WiggleZ and GAMA surveys

14. Piggyback spectroscopy:Spare fibres from AAT WiggleZ survey. FIRST radio sources with i<20.5 mag, no colour selection. ~3000 spectra so far

15. Wigglez radio galaxies LRGs QSOs

16. Wigglez radio galaxies

17. Wigglez radio galaxies

18. Wigglez radio galaxies

19. Currently ~3000 radio-loud AGN spectra from WiggleZ/GAMA, redshift range 0<z<1. Goal is to map out hot/cold accretion systems vs redshift and clustering environment to z~1.

20. The Australia Telescope 20 GHz Survey 2004-2009: Wide-band correlator on ATCA, 2.4 arcmin FoV, fast scanning at 15 deg/minute, 54ms sampling AT20G team: PI Ron Ekers and 25 astronomers/engineers/students Image Credit: D.Smyth

21. WMAP VLSS PMN AT20G WENSS SUMSS NVSS Most work on radio galaxy populations/demographics has been at frequencies near 1.4 GHz - where the deepest radio surveys are. Can we learn something new at higher frequencies?

22. Full AT20G source catalogue just released (Murphy et al. 2009) Almost 6000 sources above 40 mJy limit, optical positions to ~1 arcsec. Also simultaneous 5 and 8 GHz meas, polarization www.atnf.csiro.au/research/AT20G/

23. AT20G, radio two-colour diagram: 65% QSOs & BL Lacs, 25% galaxies, 10% faint/blank.

24. AT20G `extreme GPS’ sources Paul Hancock (2009 PhD thesis): Complete sample of 688 GigaHertz Peaked Spectrum (GPS) sources with spectral peaks above 5GHz - the youngest nearby radio sources?

25. A nearby recently-retriggered radio galaxy? SUMSS 843 MHz AT20G AT20G J074618-570258: z=0.13, passive early-type galaxy. FRI Giant radio galaxy at 843 MHz (Saripalli+ 05), extreme GPS source with peak above 20 GHz (Hancock+ 09)

26. Local AT20G sources: the 6dFS sample Complete spectroscopic sample, 195 sources with K<12.6 mag, median z~0.05. ~25% extended at 20GHz Many `old friends’ from the 2Jy sample Work in progress! First measurement of the local (z<0.1) RLF at 20 GHz

27. Summary • Luminosity functions are important - they tell us what’s common and what’s rare. • High-frequency radio surveys are becoming easier, and can provide a new perspective on the demographics and triggering of young radio sources.