Bob Fosbury ST-ECF; Leiden Nov. 2002 UV/optical properties of z~2.5 RG Massive galaxy formation during the “Quasar Epoch” Bob Fosbury (ST-ECF) Joël Vernet, Sperello di Serego Alighieri (Arcetri) Marshall Cohen (Caltech), Laura Pentericci (MPIfA) Montse Villar-Martín, Andrew Humphrey (U Hertfordshire) Based on: Keck LRISp and VLT ISAAC observations
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Bob Fosbury ST-ECF; Leiden Nov. 2002 UV/optical properties of z~2.5 RG Massive galaxy formation during the “Quasar Epoch” Bob Fosbury (ST-ECF) Joël Vernet,
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Bob Fosbury ST-ECF; Leiden Nov. 2002
UV/optical properties of z~2.5 RG
Massive galaxy formation during the “Quasar Epoch”
Bob Fosbury (ST-ECF)Joël Vernet, Sperello di Serego Alighieri (Arcetri)
Marshall Cohen (Caltech), Laura Pentericci (MPIfA)Montse Villar-Martín, Andrew Humphrey (U
Hertfordshire)
Based on: Keck LRISp and VLT ISAAC observations
Bob Fosbury ST-ECF; Leiden Nov. 2002
Radio quasars and radio galaxies
have different
orientations
The galaxies exhibit a ‘natural
coronograph’
QuickTime™ and aGIF decompressor
are needed to see this picture.
Why radio galaxies?
Bob Fosbury ST-ECF; Leiden Nov. 2002
Why redshift ~ 2.5?High star
formation ratePeak of quasar
activityEpoch of elliptical
assemblyRapid chemical
evolutionGroundbased
access to UV and optical restframe
spectrumCourtesy Blain, Cambridge
Bob Fosbury ST-ECF; Leiden Nov. 2002
Earth
fo
rms
3C
rad
io
gala
xie
s
z2p5 radio
galaxies
Most d
ista
nt
QS
Ore
ion
izatio
n
The Quasar epoch
Now
Bob Fosbury ST-ECF; Leiden Nov. 2002
Main results
The interstellar medium of the galaxy, ionized by the quasar, tells the story of early chemical evolution in massive galaxies
Dust absorption, scattering and re-radiation processes are very important for the overall SED — from the restframe UV through the FIR/sub-mm
Bob Fosbury ST-ECF; Leiden Nov. 2002
StrategyHi-res images in optical and NIR with HST
(WFPC2 & NICMOS)Optical spectropolarimetry of the restframe
UV from Ly 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 H -> K
(constrains z-range)-> forbidden lines and evolved stellar
ctm.Understand the K Hubble diagram (K–z)
Bob Fosbury ST-ECF; Leiden Nov. 2002
A note on sample selectionOptical 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.
3,900–9,000Å, R~400 dual beam polarimeterOne cycle -> 4 x 30min at standard HWP
anglesReduced to I, Q and U Stokes spectra
-> unbiassed estimates of P and Error estimates from Monte-Carlo
simulationsSlit aligned with radio axisFluxes scaled to HST magnitudesCorrected for Galactic extinction
Bob Fosbury ST-ECF; Leiden Nov. 2002
Bob Fosbury ST-ECF; Leiden Nov. 2002
4C+48.48
This is the RG with SCUBA sub-mm measurements — used later for scaling the dust scattering/emission model
Bob Fosbury ST-ECF; Leiden Nov. 2002
Scattering modelA simple dust scattering model is borne
out by analytical and Monte-Carlo simulations of transfer through a dusty, clumpy medium (eg, Varosi & Dwek, 1999; Witt & Gordon 1999)
The scattering is approximately grey (from Ly to H) but with dust signatures
A ‘luminosity weighting’ process ensures that most of the light we see comes from ~ 1Frg ~ Fqso scat exp(–ext)
Bob Fosbury ST-ECF; Leiden Nov. 2002
QuickTime™ and aGIF decompressorare needed to see this picture.
Bob Fosbury ST-ECF; Leiden Nov. 2002
ISAAC K-band spectra
Bob Fosbury ST-ECF; Leiden Nov. 2002
TXS0211-122 z = 2.340
Bob Fosbury ST-ECF; Leiden Nov. 2002
Bob Fosbury ST-ECF; Leiden Nov. 2002
Results: the UV-optical continuumDominated in the UV by scattered light
from the hidden quasar. The evidence is:The polarization
The continuum shape and intensityThe presence of (polarized) broad lines with ~the
expected EWThe nebular continuum (computed from
the recombination lines) is a minor contributor
In low P objects there is some evidence for starburst light — population is 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; Leiden Nov. 2002
Results: The FIR continuum
The dust scattering model can be used to calculate the FIR emission from the quasar-heated dust within the ionization cones
This does not include the AGN torus emission (from hot dust in the MIR), nor does it include any contribution from dusty star-formation
Figure based on 4C+48.48
Bob Fosbury ST-ECF; Leiden Nov. 2002
Bob Fosbury ST-ECF; Leiden Nov. 2002
Ly/CIV & NV/CIV vs P(%) correlations
blue: sources with similar data from literature
Bob Fosbury ST-ECF; Leiden Nov. 2002
Comparison of the kpc-scale ISM data from the RG with the BLR data discussed by Hamann & Ferland
Quasar BLR
Bob Fosbury ST-ECF; Leiden Nov. 2002
Illustrative enrichment model from Hamann & Ferland (1999). The gE exhausts its gas after ~ 1Gyr followed by passive evolution.
O/H
Bob Fosbury ST-ECF; Leiden Nov. 2002
Spectral sequence
From low-polarization, metal-poor radio galaxies
to
High-polarization, metal-rich ULIRG
Bob Fosbury ST-ECF; Leiden Nov. 2002
Comparison with Ly-break galaxyPettini et al. 2000Note dramatic difference in interstellar
absorption line spectra
…there are interesting correlations between the behaviour of the low ionization interstellar lines and the continuum polarization…
Bob Fosbury ST-ECF; Leiden Nov. 2002
SiII SiII+OI
CII
0
Bob Fosbury ST-ECF; Leiden Nov. 2002
SummaryRadio sources mark the sites of massive galaxy
and cluster formationRadio galaxies have a built-in coronographUV spectra are dominated by AGN-related
processes: dust scattering and line fluorescence
Re-radiaton in the FIR accounts for only a small fraction of the observed sub-mm flux (=> dusty SF?)
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; Leiden Nov. 2002
Conclusions
Quasar-ionized ISM reveals a phase of rapid chemical evolution during the assembly of massive galaxies
Can construct a consistent model for the transfer of quasar radiation in a dusty galaxy which accounts for both the UV/optical and a fraction of the FIR continuum