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High redshift radio galaxies and SMBH evolution
Mark Lacy


Outline - what did we learn in the last 10 years?
· Radio galaxies contain really big black holes. · There is no obvious "redshift cutoff" in the number densities of steep spectrum radio sources. · Some high-z radio galaxies are forming a lot of stars. · Radio jets can both drive strong shocks into the ISM (negative feedback for star formation?) and form stars (positive feedback for star formation?). · High-z radio galaxies are not alone - radio quiet and radio intermediate type-2 quasars are common at high redshifts. · Radio astronomers were right about massive galaxies forming at high-z!


Black hole mass and radioloudness
· Laor et al., Lacy et al., McClure & Jarvis: quasars · Best et al 2005: SDSS galaxies


Stellar masses/populations and the K-z relation
· Rest-frame near-IR luminosity of high-z radio galaxies are high (e.g. Seymour et al 2007). · Similar to submm galaxies (red crosses)


Fraction of radio-loud quasars
· Jiang et al (2007) found that, at fixed optical luminosity, RL quasar fraction in SDSS is a strong function of redshift. · Consistent with the idea that radio galaxies/quasars are the end points of massive galaxy evolution. · But also could be explained by radioloud hosts being relatively dustier at high-z


Number density evolution of high-redshift radio galaxies

· Jarvis et al. (2001) found no evidence for a decline in the space density of radio galaxies at z>3.


Star formation in HzRGs Submm continuum
· Many HzRGs are detected in the submm, with ULIRG-like luminosities (closed symbols). · But many lack such extreme SFRs


IRS spectra of HzRGs

Seymour et al. 2008


CO detections of HzRGs
· Seven HzRGs galaxies have been detected in CO, including the z=5.2 object TN J0924-2201 (Klamer et al. 2005). · Inferred H2 masses (from intensities) are ~1010-11Msun. · Dynamical masses with e.g. ALMA.

4C41.17 in CO 4-3 PdB; de Breuck et al. 2005.


Feedback - and whatever happened to the "alignment effect"?
· Radio jets of FRIIs propagate strong bow shocks into the ISM and ICM. · Lateral shocks are weaker, but cover 4. · High-z radio galaxies fall into the "blast wave" class of feedback models, with powerful shocks being driven into the IGM. · Radio-optical alignments in high-z radio galaxies were a major topic of study in the 1990s. Relevant to feedback: ­ Aligned emission line regions probably due to shocks ­ Aligned continuum a mixture of scattered quasar light and possibly jet-induced star formation, enhanced by selection effects.


Negative feedback
MRC1138-262, Nevsadba et al. 2006


Positive feedback
· Jet-induced star formation really seems to happen (e.g. Minkowski's object; Croft et al 2006) · Other low-z candidates being found (e.g. Sajina et al. in prep.) · All in lower-luminosity radio galaxies - 4C41.17 is only really good candidate at high-z/high luminosity.


IR-selected high-z radiogalaxies
· ~40% of z~2 IRselected galaxies with strong silicate absorption are radio-loud (Sajina et al. 2007). · Strong silicate absorption is not seen in any low-z radio galaxies.


What high-z radio galaxies do and don't tell us about feedback
· No doubt that the kinetic power in the jets o luminous high-z galaxy jets can provide negative feedback for star formation if they can:
­ Couple effectively to the ISM ­ Have lateral shocks powerful enough to heat the ISM away from the jet axis

· But such objects are very rare (~10-9Mpc-3). Even if AGN duty cycle is only ~1% not enough of them to account for all massive ellipticals today (~10-4Mpc-3) (though could be enough to affect rich clusters).


HzRGs and feedback-2
· What about lower-luminosity sources (~FRI/FRII divide)? · Much more common, most gEs could have been one of these at some point. · But these often seem to be forming stars through JISF. At high-z, many still seem to have dense, dusty ISMs. · Could jets inhibit accretion of gas onto the host by forming stars in the IGM, perhaps enhanced by less violent "radio mode" feedback at later epochs??


High-z radio galaxies are not alone
· Radio-intermediate IRbright obscured quasars exist (Martinez-Sansigre et al. 2005; Donley et al. 2005) · Radio-quiet obscured quasars also common at high-z (Lacy et al. 2007).


IR-selected obscured quasars
· Some objects very similar to HzRGs with opticallybright host galaxies, and only narrow lines in the rest-frame optical. · Others more like dustreddened type-1 quasars, some with BAL-like outflows. · Typical radio luminosities of high-z/high luminosity objects are around FRI/ FRII divide.


Summary
· HzRGs, along with z~6 quasars, show that at least some ~109 solar mass SMBHs in place at z>3. · Stellar luminosities consistent with massive host galaxies surrounding the black holes. · Number densities of HzRGs do not show an obvious cutoff at z>2.5, same may be true for radio-quiet obscured quasars.
­ But radio-loud quasar fraction is a strong function of redshift.

· The jets of HzRGs could either suppress or enhance star formation in their hosts.
­ AGN feedback processes may be more complicated and subtle than "blast wave" models. ­ Unclear if jets or winds dominate in the majority of quasars.


Mid-infrared selection of AGN
· Rely on hot mid-IR continuum to pick out bright AGN and quasars. · Finds both obscured and unobscured objects.


Spectroscopy
· Follow up with optical/IR spectroscopy. · Classify as:
­ type-1 (normal quasar) ­ type-2 (highionization narrow lines only) ­ red type-1 (1R) ­ starburst/LINER


Statistics (obscured:unobscured)


Radio properties
· Spitzer FLS has deep (0.1mJy) surveys at 1420MHz with the VLA (Condon et al. 2003) and 610MHz with the GMRT (Garn et al. 2007). · Most luminous/highest-z radio sources are close to the radio-loud/radio quiet divide in luminosity at 1024.5


Radio-IR
· Dashed line is starburst correlation, many objects (especially type-1s) radioweaker (cf. de Vries et al. 2007).


Obscured quasars
· Radio data are consistent with Spitzer and HST, showing that z~0.5 type-2 quasars have a wide range of star formation rates. Edge-on galaxies particularly highlyobscured - implies obscuration by host rather than AGN torus in these cases.

·


Spectral indices
· Most objects have steep spectra. · Some type-2s have flat spectra (GPSs?; cf Martinez-Sansigre et al. 2006). · Some starbursts also fairly flat (absorption?). · No obvious tendency for high-z objects to have steeper spectra.


Positive feedback
· Jet-induced star formation really seems to happen (e.g. Minkowski's object; Croft et al 2006) · Other low-z candidates being found (e.g. Sajina et al. in prep.) · All in lower-luminosity radio galaxies - 4C41.17 is only really good candidate at high-z.


4C41.17 (Dey et al. 1997)
· z=3.8; very radioluminous; also powerful far-IR source. · Dey et al. claim SV and SiIV wings are from stellar photospheres. · Also other interstellar lines typical of starbursts.


New JISF candidate from Spitzer FLS (Sajina et al. in prep.)
· Radio galaxy
is at z=0.22 · Composite star-forming /AGN galaxy also at z=0.22 (cf. 3C356??) · Getting redshifts for other 24mu sources...