High Redshift Radio Galaxies: The most massive galaxies up to z>5?

1. High Redshift Radio Galaxies:The most massive galaxies up to z>5? Carlos De Breuck (ESO) cdebreuc@eso.org • How massive are High-z Radio Galaxies (HzRGs)? • Does their AGN bother or help us? • The overdense environments of HzRGs. • What is their space density? • What is their relation with submm galaxies?

2. Are HzRGs Massive?Host galaxies are ellipticals. • At z<1, powerful radio sources are associated with gE and cD galaxies. • At z<2.5, HST/NICMOS host galaxy imaging show de Vaucouleurs profiles. Surface Brightness F622W F160W R1/4 Zirm et al 2003, Pentericci et al 2002

3. Are HzRGs Massive?Dynamical mass determinations. • 3C265 (z=0.8) mass measured from [OII] rotation curve: 8x1010 MSun within 15kpc. • CO measurements in four z>3 RGs yield dynamical masses of order 5x1011 MSun within 20 kpc. ΔV(km/s) offset Dey & Spinrad 1996, Papadopoulos et al 2000

4. Are HzRGs Massive?The K-z relation out to z=5.2 • HzRGs are most luminous galaxies in K-band. • Follow iso-mass lines for Mbar =1012 MSun. Caveats: • Radio power dependence. • Direct and/or scattered AGN contributions? • k-correction effects. Total K magnitude Redshift De Breuck et al 2001, Rocca-Volmerange et al 2004

5. K-z diagrams of submm and X-ray selected galaxies X-ray selected sources submm selected sources Total K magnitude Stern et al 2002 Serjeant et al 2003

6. Radio power dependence in the K-z diagram. • 3C, 6C and 7C samples show mean offsets of >0.5 in K. • More powerful radio sources contain more massive black holes → more massive host galaxies? • Provides natural explanation why HzRG are so massive. Eales et al 1996, Willott et al 2003

7. Does their AGN bother us? • Radio-loud AGN type II → natural coronograph. Contributions to observed K-band: • Old stellar population→ what we want to know. • Young stellar population→ estimate ages using photometry across 4000Å break. • AGN emission lines→ select line-free bands or do near-IR spectroscopy. • Scattered AGN continuum→ spectropolarimetry. • Transmitted AGN continuum→ mid-IR imaging with Spitzer and/or H spectroscopy.

8. The rest-frame K-z diagram. Spitzer program on 70 HzRGs: • 1<z<5.2 • Range of radio luminosity. • 4 IRAC bands, IRS 16 µm (z>2), 3 MIPS bands. • Sample with large amount of existing data. Goals: • Imaging at peak of old stellar population → Mass • UV to radio SED. Stern, De Breuck, Seymour, Lacy, Zirm, Rocca-Volmerange, Rettura, Vernet, Fosbury, Stanford, van Breugel, Miley, Dickinson, Dey, McCarthy, Eisenhardt, Teplitz.

9. Ly halos around HzRGs. 200 kpc 150 kpc PKS 1138-262 (z=2.16) Kurk et al. 2003 4C 41.17 (z=3.80) Reuland et al. 2003

10. Emission-line halos around HzRGs. • Narrow-band Ly  imaging of HzRGs often shows very extended halos (e.g. van Ojik et al 1996, Venemans et al 2002, Reuland et al 2003).

11. Chemically enriched emission line halos. Deep Keck spectroscopy shows NV1240, CIV1540, HeII 1640 emission extending beyond the radio lobes (Maxfield et al 2002, Villar-Martin et al 2003). 80 kpc 4C+23.56 z=2.48

12. Proto-clusters around HzRGs. • RG with 2.1<z<5.2 have an overdensity of Ly emitters (e.g. Venemans et al 2002, 2004).

13. Example: • TN J1338-1942 (z=4.1) contains: • 30 Ly emitters (Venemans et al 2002) • 56 g-band dropouts (HST/ACS; Miley et al 2004). • 6 (sub)mm galaxies (De Breuck et al 2004).

14. Proto-clusters around HzRGs. • Factor 3-5 overdensity compared to blank fields. • Velocity dispersion <half of filter bandwidth. • If just detached from Hubble flow, M~5x1014 MSun. • Ly emitters have SFR=1-10 MSun/yr, mm sources have SFR ~ 2000 MSun/yr. Consistent with HzRGs as massive galaxies tracing the densest regions out to z>5.

15. Space density of HzRGs. • Space density reasonably well known out to z~3. • Very uncertain beyond z=3 because only ~30 z>3 radio galaxies are known to date. 0 1 2 3 4 5 6 7 Redshift 2 3 4 Jarvis et al 2001, Willott et al 2001 Redshift

16. Filtered HzRG surveys. • Unfiltered radio surveys (3C, 6C, 7C, MRC, …) have <z>~1. • Most succesful high-z selection is based on Ultra Steep Radio spectra (USS), <z>~2.5. • Uses concave shape of radio spectrum. • k-correction shifts steeper part to observed wavelengths. • >90% of z>3 galaxies discovered via USS. Radio Spectral Index 0 1 2 3 4 5 6 Redshift De Breuck etal 2000-2004

17. TN J0924-2201 at z=5.2 • Extreme USS source with K=21.3 host galaxy. • Surrounded by 6 confirmed Ly emitters. K-band + radio Flux Fλ Wavelength Venemans et al 2004 van Breugel etal 1999

18. USS sources without redshifts. • ~30% of USS sources fail to yield a redshift after 1h+ of Keck/VLT spectroscopy. • Either no emission at all or featureless continuum. • Very obscured galaxies or at z>7? • Compact (→ young?) radio morphologies. Flux Fν Wavelength De Breuck et al 2001

19. Example: WN J0305+3525. • Bright (sub)mm source. • Not detected in 12.6 ks with Chandra → heavily obscured source with nH~few 1023 cm-2. • Radio-optical SED consistent with z~3. K-band + radio + SCUBA 850µm ν Fν Log observed frequency Reuland et al 2003

20. Sub-mm observations of HzRGs. Detection fraction z<2.5 ~15 % Detection fraction z>2.5 ~50 % S850 rises with z Number S850 Redshift Redshift Archibald et al 2001, Reuland et al 2004

21. Sub-mm emission: AGN or starburst? • HzRGs contain strong AGN that could heat the dust. • No correlation between radio power and S850. • Anti-correlation between S850 and UV polarization. • All submm-loud HzRGs also show CO emission tracing the gas reservoir feeding starbursts. → HzRGs may be radio-loud counterparts of SMGs? Dominated by young stars Dominated by scattered quasar S850 UV polarization

22. Star Formation History of HzRGs. • LFIR ~ 1013 LSun. • SFR ~ 1500 MSun/yr. • SFR increases with redhsift at least until z~4. → More luminous than ULIRGs. → Forming the bulk of their stellar populations. What is the role of mergers? <L850> 0 2 4 6 Redshift

23. CO emission in HzRGs • CO traces H2→ M(H2) ~ 1 to 5x1010 MSun. • CO velocity widths up to 1000 km/s → Mdyn » 1011 MSun • CO redshift often offset from AGN redshift → real systemic redshift of AGN host galaxy. • In at least 2/5 cases CO is distributed in 2 components.

24. CO emission in 4C41.17 • CO is in 2 components with M(H2)≈3x1010 MSun. • Each component coincident with a dark lane in Ly De Breuck et al, in prep.

25. Mergers seen in CO? • In 4C60.07 and 4C41.17, the CO(4-3) is in two components, separated by ~500 km/s and ~15 kpc. • Suggest merger of two gas-rich galaxies cfr. local ULIRGs. • But no galaxies seen in optical/near-IR imaging → high obscuration? De Breuck et al, in prep. Offset Velocity

26. Conclusions • The Hubble K-z diagram shows that HzRGs are amongst the most massive galaxies known to z>5. • At z<2.5, their host galaxies are ellipticals. • Many (most?) HzRGs are in giant Ly haloes and proto-clusters. • Space density is ill constrained at z>3, where they are only found in USS samples. • At z>3, RGs are strong submm sources powered by starbursts. Their enormous LFIR suggests they are forming the bulk of their stellar population. • CO emission in z>3 RGs is often in 2 components, suggesting gas-rich mergers.

27. Future Work • Rest-frame K-z diagram using Spitzer → mass. • Larger samples of z>3 RG to constrain their space density (e.g. Texas Oxford One Thousand). • Very wide-field (1000+ sq. degrees) near-IR surveys to determine HzRG space density. • Expand coverage around existing HzRG proto-clusters to determine their full size (»2 Mpc). • Deep CO observations with wide frequency coverage to study where most of the mass is located → possible with eVLA and ALMA.

28. Coming in 2007!