High redshift radio galaxies Massive galaxy formation during

High redshift radio galaxies Massive galaxy formation during the “Epoch of the Quasars” Bob Fosbury (ST-ECF) Marshall Cohen (Caltech), Bob Goodrich (Keck) Joël Vernet, Ilse van Bemmel (ESO) Montse Villar-Martín (U Hertfordshire) Sperello di Serego Alighieri, Andrea Cimatti (Arcetri) Pat Mc. Carthy (OCIW) Bob Fosbury ST-ECF

Why radio sources? The distant extragalactic radio sources signpost the mass concentrations where clusters and massive galaxies are forming Courtesy: mswarren@lanl. gov Bob Fosbury ST-ECF

Why radio galaxies? Radio quasars and radio galaxies have different orientations The galaxies exhibit a ‘natural coronograph’ Bob Fosbury ST-ECF

Why redshift ~ 2. 5? High star formation rate Peak of quasar activity Epoch of elliptical assembly? Groundbased access to UV and optical restframe spectrum Courtesy Blain, Cambridge) Bob Fosbury ST-ECF

Main result The interstellar medium of the galaxy, ionized by the quasar, tells the story of early chemical evolution in massive galaxies One of the few ways to study detailed properties of the gas phase at high redshift: cf. quasar absorption lines amplified (lensed) background sources Bob Fosbury ST-ECF

Strategy Hi-res images in optical and NIR with HST (WFPC 2 & NICMOS) Optical spectropolarimetry of the restframe UV from Lya to ~2500Å -> resonance emission and absorption lines, dust signatures, continua from young stars and from the scattered (hidden) AGN -> separate the stellar from the AGN-related processes IR spectroscopy of the restframe optical: [OII] -> J [OIII] -> H Ha -> K (constrains z-range) -> forbidden lines and evolved stellar ctm. Understand the K Hubble diagram (K–z) Bob Fosbury ST-ECF

What is unique to this study? 3 to 8 hrs of Keck LRISp integration for each of 12 objects => P(continuum) to ± 1 or 2 % and high s/n spectrophotometry Use of the first publicly available 8 m IR spectrograph (ISAAC) to see the restframe optical continuum The Keck and VLT samples partially overlap which gives us ~continuous spectral coverage from Lya to Ha Bob Fosbury ST-ECF

The complete spectral range Bob Fosbury ST-ECF

H-band spectrum of source with weak continuum Bob Fosbury ST-ECF

A note on sample selection Optical sample: Radio galaxies from the ultra-steep spectrum selected sample (Röttgering et al. 1995) with z>2 accessible to Keck IR sample: Overlapping sample but with 2. 2 < z < 2. 6 to ensure the major emission lines fall in the J, H and K windows. Bob Fosbury ST-ECF Object z 4 C+03. 24 MRC 0943 -242 MRC 2025 -218 MRC 0529 -549 USS 0828+193 4 C-00. 62 4 C+23. 56 MRC 0406 -244 B 30731+438 4 C-00. 54 4 C+48. 48 TXS 0211 -122 2. 340 MRC 0349 -211 4 C+40. 36 MRC 1138 -262 3. 570 2. 922 2. 63 2. 575 2. 572 2. 527 2. 479 2. 44 2. 429 2. 360 2. 343 2. 329 2. 265 2. 156

Example of 2 D spectra HST F 439 W Lya NV CIV <- M star Bob Fosbury ST-ECF

Bob Fosbury ST-ECF

Results: the continuum Dominated in the UV by scattered light from the hidden quasar. The evidence is: The polarization The continuum shape and intensity The presence of (polarized) broad lines with ~the expected EW The nebular continuum (computed from the recombination lines) is a minor contributor In low P objects there is some evidence for starburst light, constrained by the continuum colour In the optical, the continuum can comprise 3 components: evolved stars, scattered quasar, direct (reddened) quasar Bob Fosbury ST-ECF

Bob Fosbury ST-ECF

Bob Fosbury ST-ECF

Results: the emission lines Two main contributors to the emission lines Scattered light from the quasar — characterised by polarization; both broad and (weak) narrow components Fluorescent emission from the ISM which is ionized predominantly by the AGN — seen directly and thus unpolarized BOTH of these components are spatially extended In some objects, we do see direct (reddened) quasar light at longer wavelengths (Ha) as well Bob Fosbury ST-ECF

Lya/CIV & NV/CIV vs P correlations Red: sources with similar data from literature Bob Fosbury ST-ECF

What does NV/CIV vs. P imply? Using the modelling, we can rule out ionization, density or depletion explanations The simplest explanation is a variation of metallicity with nitrogen changing quadratically wrt C/H or O/H => secondary nitrogen production As the enrichment proceeds, dust is produced and dispersed — leading to increasing obscuration and scattering. AGN-powered ULIRG are the end-point of this process Bob Fosbury ST-ECF

Quasar BLR Comparison of the kpcscale ISM data from the RG with the BLR data discussed by Hamann & Ferland Bob Fosbury ST-ECF

Illustrative enrichment model from Hamann & Ferland (1999). The g. E exhausts its gas after ~ 1 Gyr followed by passive evolution. O/H Bob Fosbury ST-ECF

Spectral sequence Top: transparent/metal poor Bottom: obscured/metal rich Bob Fosbury ST-ECF

Comparison with Ly-break galaxy Pettini et al. 2000 Note dramatic difference in interstellar absorption line spectra Bob Fosbury ST-ECF

0 Si. II +OI Bob Fosbury ST-ECF CI I

Summary Radio sources mark the sites of massive galaxy and cluster formation Radio galaxies have a built-in coronograph UV spectra are dominated by AGN-related processes: dust scattering and line fluorescence Emission lines measure the physical and chemical and kinematic properties of the ISM Evidence for chemical evolution in the host galaxies during the “epoch of the quasars” Optical spectra -> stellar population and more detailed picture of chemical composition Bob Fosbury ST-ECF