Probing the Reionization Epoch with multi-wavelength surveys
Matt Jarvis
University of Hertfordshire/University of the Western Cape
Finding galaxies in the EoR with narrowband imaging
We can focus on
specific redshifts and
try and detect
emission lines.
But only get narrow
redshift slice, and
doing many redshift
slices is time
consuming
Smith & Jarvis 2007; Smith & Jarvis 2008a,b
SuprimeCam
VISTA
Survey speed >3x faster than WFCAM and better sensitivity
in the Z,Y,J wavebands
Lyman-Alpha Survey in the Epoch of
Reionization (LASER)
M.Jarvis + Oxford, Edinburgh, LivJM
Herts, Oxford, Edinburgh, LivJM
 Find the first large sample of galaxies within
the epoch of reionisation (expect 50-200 in GT)
 Determine their luminosity function and
clustering properties
 Also measure the properties of [OII] and H
emitting galaxies at lower redshifts.
 Pointed observations of high-redshift clusters
to measure the star-formation within dense
environments
Some candidates from ~30hours of
VISTA NB imaging
Preliminary results
from LASER
compared to Subaru
results
Preliminary results
from LASER
compared to Subaru
results
Deeper and
wider
observations
proposed in
SSA22, XMMLSS,
COSMOS, ECDFS
and Bootes
(accessible to
LOFAR)
Preliminary results
from LASER
compared to Subaru
results
In the future
HyperSuprime
Cam will make
bigger strides
(1.5sq.deg FoV
on 8m
telescope)
Other thoughts:
near-IR version
of HETDEX and
NB filters on
LSST
AGN at high redshift
For many decades the best way of probing the high-redshift Universe came from finding
AGN, predominantly QSOs (from UVX selection) and radio sources from large radio
surveys.
van Breugel et al. (1999)
Vanden Berk et al. 2001
Becker et al. 2002
QSOs in the EoR
The detection of the Gunn-Peterson
trough in the spectra of highredshift QSOs provided some of the
best evidence that we were
approaching the EoR
observationally.
However, it does not require much
neutral hydrogen to full absorb the
Ly-alpha photons. Thus, z~6.3 is
probably marking the end of the
EoR
Becker et al. 2002
Near-IR selection with UKIDSS
Venemans et al. 2008
How will current and future surveys
do?
Adapted from Willott et al. 2009
VIDEO+SERVs+DES++
Spitzer Representative Volume Survey (SERVS) approved to
cover VIDEO survey regions + LH and Elais-N1
Elais-S1
XMM-LSS
1400 hours allocated – PI Mark Lacy
Will provide 3.6 and 4.5um data to slightly deeper levels than
the VIDEO depths (L* at z>5)
VIDEO entering data sharing agreement with the Dark Energy
Survey. DES will have grizy photometry over VIDEO regions to
depths of AB~27 (5sigma)
Concentrating on SNe science initially.
Will be covered by Herschel-HerMES survey (100-500um)
Partly covered by SCUBA2
CDF-S
VIDEO+SERVs – towards the complete AGN luminosity function at z>6
L- and T-dwarfs
z=6 z=6.5
z=7
Depending on the
QSO LF slope
expect 10-30
z>6.5 QSOs in
VIDEO
Z-Y vs Y-J very efficient at selection z>6.5 QSOs. VIDEO+SERVs crucially allows us to
find the reddened high-z QSOs
The EoR via the 21cm forest
•
•
Using powerful radio sources within the EoR, the properties of the EoR can be
studied in absorption, via the 21 cm forest.
Surveys KSP will find these.
Left: a simulated 1500-hr (1-beam) LOFAR observation of a 50mJy radio
source at z=7.5. EoR absorption features are visible at f > 167MHz.
Middle: the S/N obtained for sources of different S,z in a 1500-hr spectrum.
Right: the predicted number of such sources in the LOFAR surveys.
Issues with Spectral Index
But steep spectrum
sources fall out of
flux-limited surveys
more quicky than flatspectrum sources.
Jarvis & Rawlings
2000
Means that if HzRGs have steep spectra then you need to
observe them at low frequency
Can turn around the way we use radio surveys
Optical
SDSS1-2 Pan-STARRS SDSS-3 DES
 2010  2011
Now  Now
Near-IR
UKIDSSVISTAJWSTELT
Now  Now  2013  2020
Mid/Far-IR
Spitzer HerschelWISE ALMA
Now  2012
Now  Now 
Radio
eMerlinLOFAR eVLAKAT/ASKAPSKA
2011  2011  2011  2020
Going back to the K-z relation…
Jarvis et al. 2001; Willottet al. 2003
Going back to the K-z relation…
Jarvis et al. 2001; Willottet al. 2003
Going back to the K-z relation…
Jarvis et al. 2001; Willottet al. 2003
A demonstration of combining radio surveys with
multi-wavelength data…
A typical HzRG at z=4.88
Jarvis et al. 2009
Log(L(1.4))=26.5W/Hz/sr
=0.75
Summary
• The EoR is fundamental to our understanding of the Universe, how
galaxies form and the impact of AGN activity in the early Universe
• Optical searches cannot do this to z>6.5
• (Hyper)SuprimeCam and VISTA should help change this and enable us
to determine the LF and clustering of galaxies at z> 7
• Further in the future Euclid, LSST and possible HIREX will take such
studies to higher redshift and wider areas
• Novel searches for AGN may also allow us to find highly the most
massive dark matter haloes z>7
• However, proper understanding of the speed with which reionization
takes place will come from combining these different probes of the EoR
with data from the new radio telescopes