Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University...
-
date post
20-Dec-2015 -
Category
Documents
-
view
217 -
download
0
Transcript of Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University...
Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations
University of Cape Town 2008
Philip Lah
Collaborators:
Michael Pracy (ANU)
Frank Briggs (ANU)
Jayaram Chengalur (NCRA)
Matthew Colless (AAO)
Roberto De Propris (CTIO)
Talk OutlineIntroduction• Galaxies and Galaxy Evolution • HI 21cm emission & the HI coadding technique
Current Observations with the HI coadding technique• HI in star forming galaxies at z = 0.24 • HI in Abell 370, a galaxy cluster at z = 0.37
Future Observations with SKA pathfinders• using ASKAP and WiggleZ• using MeerKAT and zCOSMOS
What is HI?
The many lives of hydrogen
HI = neutral atomic hydrogen gas (one proton, one electron)
HII = ionised hydrogen gas (one proton) – chemistry H+
H2 = hydrogen molecular gas
What is HI?
The many lives of hydrogen
HI = neutral atomic hydrogen gas (one proton, one electron)
HII = ionised hydrogen gas (one proton) – chemistry H+
H2 = hydrogen molecular gas
The Significance of HI gas
HI Gas and Star Formation
Neutral atomic hydrogen gas
cloud (HI)
molecular gas cloud (H
2)
star formation
Galaxy Types
Late-Type GalaxiesSpiral Irregular
Usually blue in optical colour
Early-Type GalaxiesElliptical Lenticular (S0)
Usually red in optical colour
Late-Type Galaxy Spectrum
optical spectrum of a
late-type galaxy
Wavelength (Å)
Inte
nsi
ty
4000 5000 6000 7000
NGC 1832
[OII]Hβ
Hα
Hγ
Hδ [OIII][SII]
Early-Type Galaxy Spectrum
line from Doyle &
Drinkwater 2006
Wavelength (Å)
Inte
nsi
ty
4000 5000 6000 7000
NGC 1832
[OII]Hβ
Hα
Hγ
Hδ [OIII][SII] optical
spectrum of an
early-type galaxy
Wavelength (Å)
Inte
nsi
ty
4000 5000 6000 7000
NGC 1832
Mg
Ca H & K
G band
Na
Late-Type Galaxy HI 21-cm Spectrum
NGC 5701 nearly face-on spiral galaxy
Rad
io F
lux
Den
sity
(m
Jy)
Early-Type Galaxies
Little or no neutral atomic hydrogen gas
As a consequence little or no active star formation
Evolution in Galaxies
Galaxy Clusters
Galaxy Cluster: Coma
Butcher-Oemler Effect
The Cosmic Star Formation Rate
Density
SFRD vs z
Hopkins 2004
SFRD vs time
Hopkins 2004
The Cosmic
Neutral GasDensity
The Cosmic Gas Density vs. Redshift
Zwaan et al. 2005HIPASSHI 21cm
Rao et al.2006DLAs
from MgII absorption
Prochaskaet al. 2005
DLAs
The Cosmic Gas Density vs. Redshift
Zwaan et al. 2005HIPASSHI 21cm
Rao et al.2006DLAs
from MgII absorption
Prochaskaet al. 2005
DLAs
Lyman-α Absorption Systems
quasar
hydrogen gas clouds
Lyman-α emission
Lyman-α absorption by clouds
Wavelength
observer
Inte
nsi
ty
Damped Lyman-α
Lyman-α 1216 Å rest frame
Inte
nsi
ty
Wavelength (Å)4200 4400 4600 4800 5000 5200
Lyα emission
QSO 1425+6039 redshift z = 3.2 Keck HIRES optical spectrum
DLALyman-α forest
The Cosmic Gas Density vs. Redshift
Zwaan et al. 2005HIPASSHI 21cm
Rao et al.2006DLAs
from MgII absorption
Prochaskaet al. 2005
DLAs
HI 21-cm Emission
Neutral atomic hydrogen creates 21 cm radiation
proton electron
Neutral atomic hydrogen creates 21 cm radiation
Neutral atomic hydrogen creates 21 cm radiation
Neutral atomic hydrogen creates 21 cm radiation
Neutral atomic hydrogen creates 21 cm radiation
photon
Neutral atomic hydrogen creates 21 cm radiation
HI 21cm emission
HI 21 cm emission decay half life ~10 million years (31014 s)
• 1 M 2.0 1033g 1.2 1057 atoms of hydrogen atoms
• total HI gas in galaxies ~ 107 to 1010 M
• HI 21 cm luminosity of ~2 1032 to 2 1035 ergs s-1
For comparison, in star forming galaxies:
• luminosity of H emission ~3 1039 to 3 1042 ergs s-1
HI 21 cm emission ~107 times less power than H emission
HI 21cm emission
HI 21 cm emission decay half life ~10 million years (31014 s)
• 1 M 2.0 1033g 1.2 1057 atoms of hydrogen atoms
• total HI gas in galaxies ~ 107 to 1010 M
• HI 21 cm luminosity of ~2 1032 to 2 1035 ergs s-1
For comparison, in star forming galaxies:
• luminosity of H emission ~3 1039 to 3 1042 ergs s-1
HI 21 cm emission ~107 times less power than H emission
HI 21cm emission
HI 21 cm emission decay half life ~10 million years (31014 s)
• 1 M 2.0 1033g 1.2 1057 atoms of hydrogen atoms
• total HI gas in galaxies ~ 107 to 1010 M
• HI 21 cm luminosity of ~2 1032 to 2 1035 ergs s-1
For comparison, in star forming galaxies:
• luminosity of H emission ~3 1039 to 3 1042 ergs s-1
HI 21 cm emission ~107 times less power than H emission
HI 21cm emission
HI 21 cm emission decay half life ~10 million years (31014 s)
• 1 M 2.0 1033g 1.2 1057 atoms of hydrogen atoms
• total HI gas in galaxies ~ 107 to 1010 M
• HI 21 cm luminosity of ~2 1032 to 2 1035 ergs s-1
For comparison, in star forming galaxies:
• luminosity of H emission ~3 1039 to 3 1042 ergs s-1
HI 21 cm emission ~107 times less power than H emission
HI 21cm emission
HI 21 cm emission decay half life ~10 million years (31014 s)
• 1 M 2.0 1033g 1.2 1057 atoms of hydrogen atoms
• total HI gas in galaxies ~ 107 to 1010 M
• HI 21 cm luminosity of ~2 1032 to 2 1035 ergs s-1
For comparison, in star forming galaxies:
• luminosity of H emission ~3 1039 to 3 1042 ergs s-1
HI 21 cm emission ~107 times less power than H emission
HI 21cm emission
HI 21 cm emission decay half life ~10 million years (31014 s)
• 1 M 2.0 1033g 1.2 1057 atoms of hydrogen atoms
• total HI gas in galaxies ~ 107 to 1010 M
• HI 21 cm luminosity of ~2 1032 to 2 1035 ergs s-1
For comparison, in star forming galaxies:
• luminosity of H emission ~3 1039 to 3 1042 ergs s-1
HI 21 cm emission ~107 times less power than H emission
HI 21cm Emission at
High Redshift
HI 21cm emission at z > 0.1
Telescope Redshift Obs Time
Number and HI Mass of galaxies
Who and When
WSRT z = 0.18 Abell 2218
200 hours 1 galaxy 4.8 109 M
Zwaan et al. 2001
VLA z = 0.19 Abell 2192
~80 hours 1 galaxy 7.0 109 M
Verheijen et al. 2004
WSRT two clusters at z = 0.19 &
z = 0.21420 hours
42 galaxies5109 to 41010 M
Verheijen et al. 2007
Arecibo z = 0.17 to 0.25
2 to 6 hours per
galaxy
26 galaxies(2 to 6) 1010 M
Catinella et al. 2007
Coadding HI signals
Coadding HI signals
RA
DEC
Radio Data Cube
Frequen
cy
HI red
shift
Coadding HI signals
RA
DEC
Radio Data Cube
Frequen
cy
HI red
shift
positions of optical galaxies
Coadding HI signals
frequency
flux
Coadding HI signals
frequency
flux
z2
z1
z3
Coadding HI signals
frequency
flux
z2
z1
z3 velocity
HI signal
Current Observations -HI coadding
Giant Metrewave Radio Telescope
Giant Metrewave Radio Telescope
Giant Metrewave Radio Telescope
Giant Metrewave Radio Telescope
Anglo-Australian Telescope
multi-object, fibre fedspectrograph
2dF/AAOmega instrument
The Fujita galaxies H emission galaxies at z = 0.24
The Subaru Telescope
The Surprime-cam filters
H atz = 0.24
Late-Type Galaxy Spectrum
optical spectrum of a
late-type galaxy
Wavelength (Å)
Inte
nsi
ty
4000 5000 6000 7000
NGC 1832
[OII]Hβ
Hα
Hγ
Hδ [OIII][SII]
Intensity
Narrowband Filter: Hα detection
at z=0.24AAOmega Spectrum
optical red wavelengths
The Fujita Galaxies
Subaru Field 24’ × 30’
narrow band imaging Hα emission at z = 0.24
(Fujita et al. 2003, ApJL, 586, L115)
348 Fujita galaxies
121 redshifts using AAT
GMRT ~48 hours on field
DEC
RA
SFRD vs z - Fujita
Hopkins 2004
Fujita et al. 2003
Fujita galaxies - B filter
Thumbnails 10’’ sq
Ordered by H
luminosity
Fujita galaxies - B filter
Thumbnails 10’’ sq
Ordered by H
luminosity
Coadded HI
Spectrum
HI spectrum all
Fujita galaxies neutral hydrogen gas measurement
using 121 redshifts - weighted average
MHI = (2.26 ± 0.90) ×109 M
raw
binned
The Cosmic
Neutral GasDensity
my new point
The Cosmic Gas Density vs. Redshift
my new point
Cosmic Neutral Gas Density vs. Time
Galaxy HI mass vs
Star Formation Rate
Galaxy HI Mass vs Star Formation Rate
HIPASS&
IRASdataz ~ 0
Doyle & Drinkwater
2006
HI Mass vs Star Formation Rate at z = 0.24
line from Doyle &
Drinkwater 2006
all 121 galaxies
HI Mass vs Star Formation Rate at z = 0.24
line from Doyle &
Drinkwater 2006
42 bright L(Hα)
galaxies
42 medium L(Hα)
galaxies
37 faint L(Hα)
galaxies
Abell 370 a galaxy cluster at z = 0.37
Nearby Galaxy Clusters are Deficient in HI Gas
HI Deficiency in ClustersDefHI =
log(MHI exp. / MHI obs)
DefHI = 1 is 10% of expected HI gas
expected gas estimate based on optical diameter
and Hubble type
interactions between galaxies and interactions
with the inter-cluster medium removes the gas
from galaxies
Gavazzi et al. 2006
Why target moderate redshift clusters?
• at moderate redshifts the whole of the galaxy cluster core and its outskirts are within the field of view of a radio telescope (nearby this not the case – one has to target individual galaxies in clusters one by one)
• around a cluster there are many more galaxies that lie within a single telescope pointing than for a typical field
• the Butcher-Oemler effect – the increase in the blue fraction of galaxies in cluster cores with redshift – Is there an increase in the gas content as well?
Why target moderate redshift clusters?
• at moderate redshifts the whole of the galaxy cluster core and its outskirts are within the field of view of a radio telescope (nearby this not the case – one has to target individual galaxies in clusters one by one)
• around a cluster there are many more galaxies that lie within a single telescope pointing than for a typical field
• the Butcher-Oemler effect – the increase in the blue fraction of galaxies in cluster cores with redshift – Is there an increase in the gas content as well?
Why target moderate redshift clusters?
• at moderate redshifts the whole of the galaxy cluster core and its outskirts are within the field of view of a radio telescope (nearby this not the case – one has to target individual galaxies in clusters one by one)
• around a cluster there are many more galaxies that lie within a single telescope pointing than for a typical field
• the Butcher-Oemler effect – the increase in the blue fraction of galaxies in cluster cores with redshift – Is there an increase in the gas content as well?
Abell 370, a galaxy cluster at z = 0.37
large galaxy cluster of
order same size as
Coma
optical imaging ANU
40 inch telescope
spectroscopic follow-
up with the AAT
GMRT ~34 hours on
cluster
Abell 370 galaxy cluster
324 galaxies
105 blue (B-V 0.57)
219 red (B-V > 0.57)
Abell 370 galaxy cluster
Abell 370 galaxy clusterAbell 370 galaxy cluster
3σ extent of X-ray gas
R200 radius at which cluster
200 times denser than the
general field
The Problem of Galaxy Sizes and the GMRT
Galaxy Sizes
• GMRT has long baselines between dishes (up to 26 km)
• provides high resolution (~3 arcsec) so that the galaxies are
resolved – i.e. they are not point sources
• for coadding the HI signal I want the galaxies to be
unresolved as I can not see the size of individual galaxies
• for the Fujita galaxies I used an estimate of the HI size from
the optical properties of spiral and irregular field galaxies and
then smoothed radio data – i.e. make the galaxies unresolved
Galaxy Sizes
• GMRT has long baselines between dishes (up to 26 km)
• provides high resolution (~3 arcsec) so that the galaxies are
resolved – i.e. they are not point sources
• for coadding the HI signal I want the galaxies to be
unresolved as I can not see the size of individual galaxies
• for the Fujita galaxies I used an estimate of the HI size from
the optical properties of spiral and irregular field galaxies and
then smoothed radio data – i.e. make the galaxies unresolved
Galaxy Sizes
• GMRT has long baselines between dishes (up to 26 km)
• provides high resolution (~3 arcsec) so that the galaxies are
resolved – i.e. they are not point sources
• for coadding the HI signal I want the galaxies to be
unresolved as I can not see the size of individual galaxies
• for the Fujita galaxies I used an estimate of the HI size from
the optical properties of spiral and irregular field galaxies and
then smoothed radio data – i.e. make the galaxies unresolved
Galaxy Sizes
• GMRT has long baselines between dishes (up to 26 km)
• provides high resolution (~3 arcsec) so that the galaxies are
resolved – i.e. they are not point sources
• for coadding the HI signal I want the galaxies to be
unresolved as I can not see the size of individual galaxies
• for the Fujita galaxies I used an estimate of the HI size from
the optical properties of spiral and irregular field galaxies and
then smoothed radio data – i.e. make the galaxies unresolved
Complication
The Abell 370 galaxies are a mixture of early and late types
in a variety of environments.
My solution make multiple measurements of the HI gas
content of the coadded galaxies using a variety of
resolutions
Complication
The Abell 370 galaxies are a mixture of early and late types
in a variety of environments.
My solution is to make multiple measurements of the HI gas
content of the coadded galaxies using a
variety of resolutions
HI mass324 galaxies
219 galaxies
105 galaxies
94 galaxies
168 galaxies
156 galaxies
110 galaxies
214 galaxies
HI mass324 galaxies
219 galaxies
105 galaxies
94 galaxies
168 galaxies
156 galaxies
110 galaxies
214 galaxies
HI mass324 galaxies
219 galaxies
105 galaxies
94 galaxies
168 galaxies
156 galaxies
110 galaxies
214 galaxies
HI mass324 galaxies
219 galaxies
105 galaxies
94 galaxies
168 galaxies
156 galaxies
110 galaxies
214 galaxies
HI mass324 galaxies
219 galaxies
105 galaxies
94 galaxies
168 galaxies
156 galaxies
110 galaxies
214 galaxies
HI all spectrumall Abell 370 galaxies
neutral hydrogen gas measurement
using 324 redshifts – large smoothing
MHI = (6.6 ± 3.5) ×109 M
HI blue outside x-ray gasblue galaxies
outside of x-ray gas measurement of neutral hydrogen
gas content
using 94 redshifts – large smoothing
MHI = (23.0 ± 7.7) ×109 M
Comparisons with the
Literature
Average HI Mass Comparisons with
Coma
Abell 370 and Coma Comparison
214 galaxies
324 galaxies
110 galaxies
Abell 370 and Coma Comparison
214 galaxies
324 galaxies
110 galaxies
Abell 370 and Coma Comparison
214 galaxies
324 galaxies
110 galaxies
HI Density Comparisons
HI density field
HI density field
HI density field
HI density field
HI density - inner regions of clusters
within 2.5 Mpc of cluster centers
HI Mass to Light Ratios
HI Mass to Light Ratios
HI mass to optical B band luminosity for
Abell 370 galaxies
Uppsala General Catalog
Local Super Cluster
(Roberts & Haynes 1994)
HI Mass to Light Ratios
HI mass to optical B band luminosity for
Abell 370 galaxies
Uppsala General Catalog
Local Super Cluster
(Roberts & Haynes 1994)
Galaxy HI mass vs
Star Formation Rate
Galaxy HI Mass vs Star Formation Rate
HIPASS&
IRASdataz ~ 0
Doyle & Drinkwater
2006
HI Mass vs Star Formation Rate in Abell 370
all 168 [OII]
emission galaxies
line from Doyle &
Drinkwater 2006
Average
HI Mass vs Star Formation Rate in Abell 370
81 blue [OII]
emission galaxies
line from Doyle &
Drinkwater 200687 red [OII]
emission galaxies
Average
Future Observations -HI coadding with SKA Pathfinders
SKA – Square Kilometer Array
• final site decision by 2012?? – money will be the deciding factor
• both South Africa and Australia are building SKA pathfinder telescopes to strengthen their case for site selection – telescopes also do interesting science
• SKA promises both high sensitivity with wide field of view
• possible SKA sites – South Africa and Australia
SKA – Square Kilometer Array
• final site decision by 2012?? – money will be the deciding factor
• both South Africa and Australia are building SKA pathfinder telescopes to strengthen their case for site selection – telescopes also do interesting science
• SKA promises both high sensitivity with wide field of view
• possible SKA sites – South Africa and Australia
SKA – Square Kilometer Array
• final site decision by 2012?? – money will be the deciding factor
• both South Africa and Australia are building SKA pathfinder telescopes to strengthen their case for site selection – telescopes also do interesting science
• SKA promises both high sensitivity with wide field of view
• possible SKA sites – South Africa and Australia
SKA – Square Kilometer Array
• final site decision by 2012?? – money will be the deciding factor
• both South Africa and Australia are building SKA pathfinder telescopes to strengthen their case for site selection – telescopes also do interesting science
• SKA promises both high sensitivity with wide field of view
• possible SKA sites – South Africa and Australia
Why South Africa
and Australia?
Global Population Density
Population Density – South Africa
Population Density – Australia
Radio Interference
108 109
Frequency (Hz)
Log
Sca
les
Radio Interference
108 109
Frequency (Hz)
HI at z = 0.4
HI at z = 1.0
Log
Sca
les
The SKA pathfinders
ASKAP
MeerKAT
South African SKA pathfinder
ASKAP and MeerKAT parametersASKAP MeerKAT
Number of Dishes 45 80
Dish Diameter 12 m 12 m
Aperture Efficiency 0.8 0.8
System Temp. 35 K 30 K
Frequency range 700 – 1800 MHz 500 – 2500 MHz
Instantaneous bandwidth 300 MHz 512 MHz
Field of View:
at 1420 MHz (z = 0)
at 700 MHz (z = 1)
30 deg2
30 deg2
1.2 deg2
4.8 deg2
Maximum Baseline Length 8 km 10 km
ASKAP and MeerKAT parametersASKAP MeerKAT
Number of Dishes 45 80
Dish Diameter 12 m 12 m
Aperture Efficiency 0.8 0.8
System Temp. 35 K 30 K
Frequency range 700 – 1800 MHz 500 – 2500 MHz
Instantaneous bandwidth 300 MHz 512 MHz
Field of View:
at 1420 MHz (z = 0)
at 700 MHz (z = 1)
30 deg2
30 deg2
1.2 deg2
4.8 deg2
Maximum Baseline Length 8 km 10 km
ASKAP and MeerKAT parametersASKAP MeerKAT
Number of Dishes 45 80
Dish Diameter 12 m 12 m
Aperture Efficiency 0.8 0.8
System Temp. 35 K 30 K
Frequency range 700 – 1800 MHz 500 – 2500 MHz
Instantaneous bandwidth 300 MHz 512 MHz
Field of View:
at 1420 MHz (z = 0)
at 700 MHz (z = 1)
30 deg2
30 deg2
1.2 deg2
4.8 deg2
Maximum Baseline Length 8 km 10 km
z = 0.4 to 1.0 in a single observation
z = 0.2 to 1.0 in a single observation
single pointing assumes no evolution
in the HI mass function
(Johnston et al. 2007)
z = 0.45 to 1.0
980 MHz to 700 MHz
one year observations (8760 hours)
Simulated ASKAP HI detections
MeerKAT HI direct detections
• MeerKAT will detect galaxies in less time than ASKAP – due to its
higher sensitivity by ~2 times – it will still take a long time to detect
galaxies at z = 1.0 - perhaps in around a quarter of a year
• however at a particular redshift in a single pointing, MeerKAT will
end up with fewer total detections – due to MeerKAT`s smaller field of
view
• MeerKAT has a larger instantaneous bandwidth of 512 MHz – observe
from z = 0.2 to z = 1.0 in single observation (1200 MHz to 700 MHz)
• MeerKAT’s field of view is better matched to many current optical and
other wavelength surveys
MeerKAT HI direct detections
• MeerKAT will detect galaxies in less time than ASKAP – due to its
higher sensitivity by ~2 times – it will still take a long time to detect
galaxies at z = 1.0 - perhaps in around a quarter of a year
• however at a particular redshift in a single pointing, MeerKAT will
end up with fewer total detections – due to MeerKAT`s smaller field of
view
• MeerKAT has a larger instantaneous bandwidth of 512 MHz – observe
from z = 0.2 to z = 1.0 in single observation (1200 MHz to 700 MHz)
• MeerKAT’s field of view is better matched to many current optical and
other wavelength surveys
MeerKAT HI direct detections
• MeerKAT will detect galaxies in less time than ASKAP – due to its
higher sensitivity by ~2 times – it will still take a long time to detect
galaxies at z = 1.0 - perhaps in around a quarter of a year
• however at a particular redshift in a single pointing, MeerKAT will
end up with fewer total detections – due to MeerKAT`s smaller field of
view
• MeerKAT has a larger instantaneous bandwidth of 512 MHz – observe
from z = 0.2 to z = 1.0 in single observation (1200 MHz to 700 MHz)
• MeerKAT’s field of view is better matched to many current optical and
other wavelength surveys
MeerKAT HI direct detections
• MeerKAT will detect galaxies in less time than ASKAP – due to its
higher sensitivity by ~2 times – it will still take a long time to detect
galaxies at z = 1.0 - perhaps in around a quarter of a year
• however at a particular redshift in a single pointing, MeerKAT will
end up with fewer total detections – due to MeerKAT`s smaller field of
view
• MeerKAT has a larger instantaneous bandwidth of 512 MHz – observe
from z = 0.2 to z = 1.0 in single observation (1200 MHz to 700 MHz)
• MeerKAT’s field of view is better matched to many current optical and
other wavelength surveys
What I could do with
the SKA pathfinders
using optical coadding of HI
if you gave them to me
TODAY.
WiggleZ and zCOSMOSWiggleZ zCOSMOS
Instrument/Telescope AAOmega on the AAT VIMOS on the VLT
Target Selectionultraviolet using the
GALEX satelliteoptical I band
IAB < 22.5
Survey Area1000 deg2 total
7 fields minimum size of ~100 deg2
COSMOS fieldsingle field
~2 deg2
Primary Redshift Range
0.5 < z < 1.0 0.1 < z < 1.2
Survey Timeline 2006 to 2009 2005 to 2008
nz by survey end 176,000 20,000
nz in March 2008 ~62,000 ~10,000
WiggleZ and zCOSMOSWiggleZ zCOSMOS
Instrument/Telescope AAOmega on the AAT VIMOS on the VLT
Target Selectionultraviolet using the
GALEX satelliteoptical I band
IAB < 22.5
Survey Area1000 deg2 total
7 fields minimum size of ~100 deg2
COSMOS fieldsingle field
~2 deg2
Primary Redshift Range
0.5 < z < 1.0 0.1 < z < 1.2
Survey Timeline 2006 to 2010 2005 to 2008
nz by survey end 176,000 20,000
nz in March 2008 ~62,000 ~10,000
WiggleZ and zCOSMOSWiggleZ zCOSMOS
Instrument/Telescope AAOmega on the AAT VIMOS on the VLT
Target Selectionultraviolet using the
GALEX satelliteoptical I band
IAB < 22.5
Survey Area1000 deg2 total
7 fields minimum size of ~100 deg2
COSMOS fieldsingle field
~2 deg2
Primary Redshift Range
0.5 < z < 1.0 0.1 < z < 1.2
Survey Timeline 2006 to 2010 2005 to 2008
nz by survey end 176,000 20,000
nz in March 2008 ~62,000 ~10,000
WiggleZ and
ASKAP
WiggleZ field
data as of July 2008 z = 0.45 to 1.0
ASKAP beam size
Diameter 6.2 degreesArea 30 deg2
square ~10 degrees across
ASKAP & WiggleZ 100hrs
nz = 5072
ASKAP & WiggleZ 100hrs
nz = 5072
ASKAP & WiggleZ 100hrs
nz = 5072
ASKAP & WiggleZ 1000hrs
nz = 5072
zCOSMOS and
MeerKAT
zCOSMOS field
data as of March 2008 z = 0.2 to 1.0
7118 galaxies
MeerKAT beam size at
1420 MHz z = 0
MeerKAT beam size at
1000 MHz z = 0.4
square ~1.3 degrees across
MeerKAT & zCOSMOS 100hrs
nz = 3559
half the number of
redshift
MeerKAT & zCOSMOS 100hrs
nz = 3559
MeerKAT & zCOSMOS 100hrs
nz = 3559
MeerKAT & zCOSMOS 1000hrs
nz = 3559
HI Science with SKA Pathfinders
at High z
HI Science with SKA Pathfinders at High z
• provide constraints on the HI mass function with redshift (the
distribution of galaxies with HI mass) – won’t get information
on smaller HI systems – need SKA for that
• begin to trace how gas content varies in different
environments with redshift
• test star formation rate – HI correlation in the period of
extreme star formation activity in the universe
• won’t get galaxy velocity field information – again need SKA
HI Science with SKA Pathfinders at High z
• provide constraints on the HI mass function with redshift (the
distribution of galaxies with HI mass) – won’t get information
on smaller HI systems – need SKA for that
• begin to trace how gas content varies in different
environments with redshift
• test star formation rate – HI correlation in the period of
extreme star formation activity in the universe
• won’t get galaxy velocity field information – again need SKA
HI Science with SKA Pathfinders at High z
• provide constraints on the HI mass function with redshift (the
distribution of galaxies with HI mass) – won’t get information
on smaller HI systems – need SKA for that
• begin to trace how gas content varies in different
environments with redshift
• test star formation rate – HI correlation in the period of
extreme star formation activity in the universe
• won’t get galaxy velocity field information – again need SKA
HI Science with SKA Pathfinders at High z
• provide constraints on the HI mass function with redshift (the
distribution of galaxies with HI mass) – won’t get information
on smaller HI systems – need SKA for that
• begin to trace how gas content varies in different
environments with redshift
• test star formation rate – HI correlation in the period of
extreme star formation activity in the universe
• won’t get galaxy velocity field information – again need SKA
Conclusion
• one can use coadding with optical redshifts to make measurement of
the HI 21 cm emission from galaxies at redshifts z > 0.1
• using this method we have measured the cosmic neutral gas density at
z = 0.24 and have shown that the value is consistent with that from
damped Lyα measurements
• galaxy cluster Abell 370 at z = 0.37 has significantly more gas than
similar clusters at z ~ 0
• the SKA pathfinders ASKAP and MeerKAT can measure HI 21 cm
emission from galaxies out to z = 1.0 using the coadding technique with
existing optical redshift surveys
Conclusion