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Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations
University of Cape Town 2008
Philip Lah
![Page 2: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/2.jpg)
Collaborators:
Michael Pracy (ANU)
Frank Briggs (ANU)
Jayaram Chengalur (NCRA)
Matthew Colless (AAO)
Roberto De Propris (CTIO)
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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
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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
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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
![Page 6: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/6.jpg)
The Significance of HI gas
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HI Gas and Star Formation
Neutral atomic hydrogen gas
cloud (HI)
molecular gas cloud (H
2)
star formation
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Galaxy Types
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Late-Type GalaxiesSpiral Irregular
Usually blue in optical colour
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Early-Type GalaxiesElliptical Lenticular (S0)
Usually red in optical colour
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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]
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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
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Late-Type Galaxy HI 21-cm Spectrum
NGC 5701 nearly face-on spiral galaxy
Rad
io F
lux
Den
sity
(m
Jy)
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Early-Type Galaxies
Little or no neutral atomic hydrogen gas
As a consequence little or no active star formation
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Evolution in Galaxies
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Galaxy Clusters
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Galaxy Cluster: Coma
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Butcher-Oemler Effect
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The Cosmic Star Formation Rate
Density
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SFRD vs z
Hopkins 2004
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SFRD vs time
Hopkins 2004
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The Cosmic
Neutral GasDensity
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The Cosmic Gas Density vs. Redshift
Zwaan et al. 2005HIPASSHI 21cm
Rao et al.2006DLAs
from MgII absorption
Prochaskaet al. 2005
DLAs
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The Cosmic Gas Density vs. Redshift
Zwaan et al. 2005HIPASSHI 21cm
Rao et al.2006DLAs
from MgII absorption
Prochaskaet al. 2005
DLAs
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Lyman-α Absorption Systems
quasar
hydrogen gas clouds
Lyman-α emission
Lyman-α absorption by clouds
Wavelength
observer
Inte
nsi
ty
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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
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The Cosmic Gas Density vs. Redshift
Zwaan et al. 2005HIPASSHI 21cm
Rao et al.2006DLAs
from MgII absorption
Prochaskaet al. 2005
DLAs
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HI 21-cm Emission
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Neutral atomic hydrogen creates 21 cm radiation
proton electron
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Neutral atomic hydrogen creates 21 cm radiation
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Neutral atomic hydrogen creates 21 cm radiation
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Neutral atomic hydrogen creates 21 cm radiation
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Neutral atomic hydrogen creates 21 cm radiation
photon
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Neutral atomic hydrogen creates 21 cm radiation
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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
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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
![Page 37: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/37.jpg)
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
![Page 38: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/38.jpg)
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
![Page 39: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/39.jpg)
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
![Page 40: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/40.jpg)
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
![Page 41: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/41.jpg)
HI 21cm Emission at
High Redshift
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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
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Coadding HI signals
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Coadding HI signals
RA
DEC
Radio Data Cube
Frequen
cy
HI red
shift
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Coadding HI signals
RA
DEC
Radio Data Cube
Frequen
cy
HI red
shift
positions of optical galaxies
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Coadding HI signals
frequency
flux
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Coadding HI signals
frequency
flux
z2
z1
z3
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Coadding HI signals
frequency
flux
z2
z1
z3 velocity
HI signal
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Current Observations -HI coadding
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Giant Metrewave Radio Telescope
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Giant Metrewave Radio Telescope
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Giant Metrewave Radio Telescope
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Giant Metrewave Radio Telescope
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Anglo-Australian Telescope
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multi-object, fibre fedspectrograph
2dF/AAOmega instrument
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The Fujita galaxies H emission galaxies at z = 0.24
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The Subaru Telescope
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The Surprime-cam filters
H atz = 0.24
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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]
![Page 60: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/60.jpg)
Intensity
Narrowband Filter: Hα detection
at z=0.24AAOmega Spectrum
optical red wavelengths
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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
![Page 62: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/62.jpg)
SFRD vs z - Fujita
Hopkins 2004
Fujita et al. 2003
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Fujita galaxies - B filter
Thumbnails 10’’ sq
Ordered by H
luminosity
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Fujita galaxies - B filter
Thumbnails 10’’ sq
Ordered by H
luminosity
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Coadded HI
Spectrum
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HI spectrum all
Fujita galaxies neutral hydrogen gas measurement
using 121 redshifts - weighted average
MHI = (2.26 ± 0.90) ×109 M
raw
binned
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The Cosmic
Neutral GasDensity
![Page 68: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/68.jpg)
my new point
The Cosmic Gas Density vs. Redshift
![Page 69: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/69.jpg)
my new point
Cosmic Neutral Gas Density vs. Time
![Page 70: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/70.jpg)
Galaxy HI mass vs
Star Formation Rate
![Page 71: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/71.jpg)
Galaxy HI Mass vs Star Formation Rate
HIPASS&
IRASdataz ~ 0
Doyle & Drinkwater
2006
![Page 72: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/72.jpg)
HI Mass vs Star Formation Rate at z = 0.24
line from Doyle &
Drinkwater 2006
all 121 galaxies
![Page 73: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/73.jpg)
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
![Page 74: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/74.jpg)
Abell 370 a galaxy cluster at z = 0.37
![Page 75: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/75.jpg)
Nearby Galaxy Clusters are Deficient in HI Gas
![Page 76: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/76.jpg)
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
![Page 77: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/77.jpg)
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?
![Page 78: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/78.jpg)
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?
![Page 79: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/79.jpg)
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?
![Page 80: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/80.jpg)
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
![Page 81: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/81.jpg)
Abell 370 galaxy cluster
324 galaxies
105 blue (B-V 0.57)
219 red (B-V > 0.57)
Abell 370 galaxy cluster
![Page 82: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/82.jpg)
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
![Page 83: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/83.jpg)
The Problem of Galaxy Sizes and the GMRT
![Page 84: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/84.jpg)
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
![Page 85: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/85.jpg)
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
![Page 86: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/86.jpg)
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
![Page 87: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/87.jpg)
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
![Page 88: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/88.jpg)
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
![Page 89: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/89.jpg)
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
![Page 90: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/90.jpg)
HI mass324 galaxies
219 galaxies
105 galaxies
94 galaxies
168 galaxies
156 galaxies
110 galaxies
214 galaxies
![Page 91: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/91.jpg)
HI mass324 galaxies
219 galaxies
105 galaxies
94 galaxies
168 galaxies
156 galaxies
110 galaxies
214 galaxies
![Page 92: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/92.jpg)
HI mass324 galaxies
219 galaxies
105 galaxies
94 galaxies
168 galaxies
156 galaxies
110 galaxies
214 galaxies
![Page 93: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/93.jpg)
HI mass324 galaxies
219 galaxies
105 galaxies
94 galaxies
168 galaxies
156 galaxies
110 galaxies
214 galaxies
![Page 94: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/94.jpg)
HI mass324 galaxies
219 galaxies
105 galaxies
94 galaxies
168 galaxies
156 galaxies
110 galaxies
214 galaxies
![Page 95: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/95.jpg)
HI all spectrumall Abell 370 galaxies
neutral hydrogen gas measurement
using 324 redshifts – large smoothing
MHI = (6.6 ± 3.5) ×109 M
![Page 96: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/96.jpg)
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
![Page 97: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/97.jpg)
Comparisons with the
Literature
![Page 98: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/98.jpg)
Average HI Mass Comparisons with
Coma
![Page 99: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/99.jpg)
Abell 370 and Coma Comparison
214 galaxies
324 galaxies
110 galaxies
![Page 100: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/100.jpg)
Abell 370 and Coma Comparison
214 galaxies
324 galaxies
110 galaxies
![Page 101: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/101.jpg)
Abell 370 and Coma Comparison
214 galaxies
324 galaxies
110 galaxies
![Page 102: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/102.jpg)
HI Density Comparisons
![Page 103: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/103.jpg)
HI density field
![Page 104: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/104.jpg)
HI density field
![Page 105: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/105.jpg)
HI density field
![Page 106: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/106.jpg)
HI density field
![Page 107: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/107.jpg)
HI density - inner regions of clusters
within 2.5 Mpc of cluster centers
![Page 108: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/108.jpg)
HI Mass to Light Ratios
![Page 109: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/109.jpg)
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)
![Page 110: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/110.jpg)
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)
![Page 111: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/111.jpg)
Galaxy HI mass vs
Star Formation Rate
![Page 112: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/112.jpg)
Galaxy HI Mass vs Star Formation Rate
HIPASS&
IRASdataz ~ 0
Doyle & Drinkwater
2006
![Page 113: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/113.jpg)
HI Mass vs Star Formation Rate in Abell 370
all 168 [OII]
emission galaxies
line from Doyle &
Drinkwater 2006
Average
![Page 114: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/114.jpg)
HI Mass vs Star Formation Rate in Abell 370
81 blue [OII]
emission galaxies
line from Doyle &
Drinkwater 200687 red [OII]
emission galaxies
Average
![Page 115: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/115.jpg)
Future Observations -HI coadding with SKA Pathfinders
![Page 116: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/116.jpg)
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
![Page 117: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/117.jpg)
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
![Page 118: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/118.jpg)
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
![Page 119: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/119.jpg)
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
![Page 120: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/120.jpg)
Why South Africa
and Australia?
![Page 121: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/121.jpg)
Global Population Density
![Page 122: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/122.jpg)
Population Density – South Africa
![Page 123: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/123.jpg)
Population Density – Australia
![Page 124: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/124.jpg)
Radio Interference
108 109
Frequency (Hz)
Log
Sca
les
![Page 125: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/125.jpg)
Radio Interference
108 109
Frequency (Hz)
HI at z = 0.4
HI at z = 1.0
Log
Sca
les
![Page 126: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/126.jpg)
The SKA pathfinders
![Page 127: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/127.jpg)
ASKAP
![Page 128: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/128.jpg)
MeerKAT
South African SKA pathfinder
![Page 129: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/129.jpg)
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
![Page 130: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/130.jpg)
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
![Page 131: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/131.jpg)
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
![Page 132: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/132.jpg)
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
![Page 133: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/133.jpg)
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
![Page 134: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/134.jpg)
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
![Page 135: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/135.jpg)
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
![Page 136: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/136.jpg)
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
![Page 137: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/137.jpg)
What I could do with
the SKA pathfinders
using optical coadding of HI
if you gave them to me
TODAY.
![Page 138: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/138.jpg)
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
![Page 139: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/139.jpg)
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
![Page 140: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/140.jpg)
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
![Page 141: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/141.jpg)
WiggleZ and
ASKAP
![Page 142: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/142.jpg)
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
![Page 143: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/143.jpg)
ASKAP & WiggleZ 100hrs
nz = 5072
![Page 144: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/144.jpg)
ASKAP & WiggleZ 100hrs
nz = 5072
![Page 145: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/145.jpg)
ASKAP & WiggleZ 100hrs
nz = 5072
![Page 146: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/146.jpg)
ASKAP & WiggleZ 1000hrs
nz = 5072
![Page 147: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/147.jpg)
zCOSMOS and
MeerKAT
![Page 148: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/148.jpg)
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
![Page 149: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/149.jpg)
MeerKAT & zCOSMOS 100hrs
nz = 3559
half the number of
redshift
![Page 150: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/150.jpg)
MeerKAT & zCOSMOS 100hrs
nz = 3559
![Page 151: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/151.jpg)
MeerKAT & zCOSMOS 100hrs
nz = 3559
![Page 152: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/152.jpg)
MeerKAT & zCOSMOS 1000hrs
nz = 3559
![Page 153: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/153.jpg)
HI Science with SKA Pathfinders
at High z
![Page 154: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/154.jpg)
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
![Page 155: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/155.jpg)
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
![Page 156: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/156.jpg)
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
![Page 157: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/157.jpg)
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
![Page 158: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/158.jpg)
Conclusion
![Page 159: Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University of Cape Town 2008 Philip Lah](https://reader035.vdocuments.mx/reader035/viewer/2022062516/56649d415503460f94a1c97b/html5/thumbnails/159.jpg)
• 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