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The Evolution of Gas in
Galaxies
Philip Lah
End of Thesis
Colloquium
Chair of Supervisory Panel:
Frank Briggs (ANU)
Supervisory Panel:
Jayaram Chengalur (NCRA)
Matthew Colless (AAO)
Roberto De Propris (CTIO)
Erwin De Blok (UCT)
With Assistance From: Michael Pracy (ANU)
Talk Outline
Introduction
• HI 21-cm emission, galaxies and star formation
• the cosmic star formation rate density and the cosmic HI density
• high redshift HI 21-cm emssion observations and the coadding
technique
Current Observations with the HI coadding technique
• HI in star-forming galaxies at z = 0.24
• HI in galaxies around Abell 370, a galaxy cluster at z = 0.37
Future Observations with SKA pathfinders
• using ASKAP and WiggleZ
• using MeerKAT and zCOSMOS
• ideas on the evolution of gas in galaxies
Talk Outline
Introduction
• HI 21-cm emission, galaxies and star formation
• the cosmic star formation rate density and the cosmic HI density
• high redshift HI 21-cm emssion observations and the coadding
technique
Current Observations with the HI coadding technique
• HI in star-forming galaxies at z = 0.24
• HI in galaxies around Abell 370, a galaxy cluster at z = 0.37
Future Observations with SKA pathfinders
• using ASKAP and WiggleZ
• using MeerKAT and zCOSMOS
• ideas on the evolution of gas in galaxies
Talk Outline
Introduction
• HI 21-cm emission, galaxies and star formation
• the cosmic star formation rate density and the cosmic HI density
• high redshift HI 21-cm emssion observations and the coadding
technique
Current Observations with the HI coadding technique
• HI in star-forming galaxies at z = 0.24
• HI in galaxies around Abell 370, a galaxy cluster at z = 0.37
Future Observations with SKA pathfinders
• using ASKAP and WiggleZ
• using MeerKAT and zCOSMOS
• ideas on the evolution of gas in galaxies
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
decay half life ~10 million years (31014 s)
HI 21-cm Emission
From Galaxies
Galaxy M33: optical
Galaxy M33: HI 21-cm emission
Galaxy M33: optical and HI
Galaxy M33: optical
HI Gas and Star Formation
neutral atomic
hydrogen gas
cloud (HI)
molecular gas
cloud (H2)
star formation
Galaxy HI mass
vs
Star Formation Rate
Galaxy HI Mass vs Star Formation Rate
HIPASS
&
IRAS
data
z~0
Doyle &
Drinkwater
2006
The
Star Formation Rate
Density
of the Universe
Star Formation Rate Density Evolution
Compilation
by Hopkins
2004
The
HI Gas Density
of the Universe
HI Gas Density Evolution
Not a log
scale
HI Gas Density Evolution
Lah et al.
2007
coadded
HI 21cm
Prochaska
et al. 2005
& 2009
DLAs
Zwaan et
al. 2005
HIPASS
HI 21cm
Rao et al.
2006
DLAs
from MgII
absorption
HI 21cm
Emission at
High Redshift
HI 21cm emission at z > 0.1
Zwaan et al. 2001
WSRT 200 hours
HI 21cm emission at z > 0.1
Verheijen et al. 2004
VLA 80 hours
HI 21cm emission at z > 0.1
Verheijen et al. 2007
WSRT 180 & 240 hours
HI 21cm emission at z > 0.1
Catinella et al. 2007
Arecibo 2-6 hours per galaxy
HI 21cm emission at z > 0.1
Lah et al. 2007
coadded GMRT 81 hours
Lah et al. 2009
coadded GMRT 63 hours
Coadding HI signals
Coadding HI signals
Radio Data
Cube
DEC
RA
Coadding HI signals
Radio Data
Cube
DEC
positions of
optical galaxies
RA
flux
Coadding HI signals
frequency
Coadding HI signals
z1
flux
z2
z3
frequency
z1, z2 & z3
optical redshifts
of galaxies
Coadding HI signals
z1
flux
z2
z3
velocity
z1, z2 & z3
optical redshifts
of galaxies
Coadding HI signals
z1
flux
z2
Coadded
HI signal
z3
velocity
velocity
z1, z2 & z3
optical redshifts
of galaxies
Current Observations HI coadding
Giant Metrewave Radio Telescope
Giant Metrewave Radio Telescope
Giant Metrewave Radio Telescope
Giant Metrewave Radio Telescope
Anglo-Australian Telescope
2dF/AAOmega
instrument
multi-object, fibre fed
spectrograph
The Fujita galaxies
H emission galaxies at z = 0.24
The Fujita Galaxies
Subaru Field 24’ × 30’
narrow band imaging 
Hα emission at z = 0.24
look-back time ~3 billion years
(Fujita et al. 2003,
ApJL, 586, L115)
DEC
348 Fujita galaxies
121 redshifts using AAT
GMRT ~48 hours on field
RA
Star Formation Rate Density Evolution
Compilation
by Hopkins
2004
Star Formation Rate Density Evolution
Fujita
et al.
2003
value
Compilation
by Hopkins
2004
Coadded
HI Spectrum
Fujita galaxies
coadded HI
spectrum
raw
HI spectrum allusing 121 redshifts
- weighted average
Fujita galaxies
coadded HI
spectrum
raw
HI spectrum allusing 121 redshifts
- weighted average
binned
MHI =
(2.26 ± 0.90)
×109 M
The
HI Gas Density
of the Universe
HI Gas Density Evolution
Lah et al.
2007
coadded
HI 21cm
Galaxy HI mass
vs
Star Formation Rate
Galaxy HI Mass vs Star Formation Rate
HIPASS
&
IRAS
data
z~0
Doyle &
Drinkwater
2006
HI Mass vs Star Formation Rate at z = 0.24
all 121
galaxies
line from
Doyle &
Drinkwater
2006
HI Mass vs Star Formation Rate at z = 0.24
42 bright
L(Hα)
galaxies
42 medium
L(Hα)
galaxies
line from
Doyle &
Drinkwater
2006
37 faint
L(Hα)
galaxies
Abell 370
a galaxy cluster at z = 0.37
Galaxy Clusters
and HI gas
Galaxy Cluster: Coma
Nearby Galaxy Clusters
Are Deficient
in HI Gas
HI Deficiency in Clusters
DefHI =
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 the galaxies
Gavazzi et al. 2006
Why target moderate
redshift clusters
for HI gas?
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
pointing
• the Butcher-Oemler effect
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
pointing
• the Butcher-Oemler effect
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
pointing
• the (Harvey) Butcher-Oemler effect
Blue Fraction, fB
The Butcher-Oemler Effect
Redshift, z
Blue Fraction, fB
The Butcher-Oemler Effect
Abell 370
Redshift, z
Abell 370
a galaxy cluster at z = 0.37
Abell 370, a galaxy cluster at z = 0.37
large galaxy cluster of order
same size as Coma
 similar cluster velocity
dispersion and X-ray gas
temperature
optical imaging
ANU 40 inch telescope
spectroscopic follow-up with
the AAT
Abell 370 cluster core, ESO VLT image
GMRT ~34 hours on cluster
HI z = 0.35 to 0.39
look-back time ~4 billion years
Abell
370
galaxy
Abell 370
galaxy
cluster cluster
324 galaxies
105 blue
(B-V  0.57)
219 red
(B-V > 0.57)
Abell
370
galaxy
Abell 370
galaxy
cluster cluster
3σ extent of
X-ray gas
R200  radius
at which cluster
200 times
denser than the
general field
Coadded
HI Mass
Measurements
HI mass
324 galaxies
219 galaxies
105 galaxies
Inner Regions
Outer Regions
94 galaxies
156 galaxies
The galaxies around Abell 370 are
168a galaxies
mixture of early and late types
in a variety of environments. 110 galaxies
214 galaxies
HI mass
324 galaxies
219 galaxies
105 galaxies
94 galaxies
156 galaxies
168 galaxies
110 galaxies
214 galaxies
HI mass
324 galaxies
219 galaxies
105 galaxies
94 galaxies
156 galaxies
HI deficient 11 blue galaxies within X-ray gas
168 galaxies
110 galaxies
214 galaxies
HI mass
324 galaxies
219 galaxies
105 galaxies
94 galaxies
156 galaxies
168 galaxies
110 galaxies
214 galaxies
HI mass
324 galaxies
219 galaxies
105 galaxies
94 galaxies
156 galaxies
168 galaxies
110 galaxies
214 galaxies
HI Density
Comparisons
HI density
Whole
Redshift
Region
z = 0.35 to
0.39
Outer
Cluster
Region
Inner
Cluster
Region
Distribution of galaxies around Abell 370
cluster
redshift
HI density
Whole
Redshift
Region
z = 0.35 to
0.39
Outer
Cluster
Region
Inner
Cluster
Region
Distribution of galaxies around Abell 370
cluster
redshift
within
R200
region
HI density
Whole
Redshift
Region
z = 0.35 to
0.39
Outer
Cluster
Region
Inner
Cluster
Region
Galaxy HI mass
vs
Star Formation Rate
Galaxy HI Mass vs Star Formation Rate
HIPASS
&
IRAS
data
z~0
Doyle &
Drinkwater
2006
HI Mass vs Star Formation Rate in Abell 370
all 168
[OII]
emission
galaxies
Average
line from
Doyle &
Drinkwater
2006
HI Mass vs Star Formation Rate in Abell 370
81 blue [OII]
emission
galaxies
Average
87 red [OII]
emission
galaxies
line from
Doyle &
Drinkwater
2006
Future Observations HI coadding with SKA Pathfinders
SKA – Square Kilometer Array
• SKA promises both high sensitivity with a wide field of view
• possible SKA sites – South Africa and Australia
• both South Africa and
Australia are currently
building SKA pathfinder
telescopes to strengthen
their case for site selection
• the SKA pathfinder
telescopes will also do
interesting science
SKA – Square Kilometer Array
• SKA promises both high sensitivity with a wide field of view
• possible SKA sites – South Africa and Australia (RFI quiet areas)
• both South Africa and
Australia are currently
building SKA pathfinder
telescopes to strengthen
their case for site selection
• the SKA pathfinder
telescopes will also do
interesting science
SKA – Square Kilometer Array
• SKA promises both high sensitivity with a wide field of view
• possible SKA sites – South Africa and Australia (RFI quiet areas)
• both South Africa and
Australia are currently
building SKA pathfinder
telescopes to strengthen
their case for site selection
• the SKA pathfinder
telescopes will also do
interesting science
The SKA pathfinders
ASKAP
MeerKAT
South African
SKA pathfinder
ASKAP and MeerKAT
ASKAP parameters
MeerKAT
30 (36)
80
12 m
12 m
0.8
0.8
50 K
30 K
700 – 1800 MHz
500 – 2500 MHz
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
2 (6) km
10 km
Number of Dishes
Dish Diameter
Aperture Efficiency
System Temp.
Frequency range
Instantaneous bandwidth
ASKAP and MeerKAT
ASKAP parameters
MeerKAT
30 (36)
80
12 m
12 m
0.8
0.8
35 K
30 K
700 – 1800 MHz
500 – 2500 MHz
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
2 (8) km
10 km
Number of Dishes
Dish Diameter
Aperture Efficiency
System Temp.
Frequency range
Instantaneous bandwidth
ASKAP and MeerKAT
ASKAP parameters
MeerKAT
Number of Dishes
Dish Diameter
Aperture Efficiency
System Temp.
Frequency range
Instantaneous bandwidth
Field of View:
at 1420 MHz (z = 0)
at 700 MHz (z = 1)
Maximum Baseline Length
30 (36)
80
12 m
12 m
0.8
0.8
35 K
30 K
700 – 1800 MHz
500 – 2500 MHz
300 MHz
512 MHz
z = 0.4 to 1.0 in a
z = 0.2 to 1.0 in a
single30
observation
single1.2
observation
deg2
deg2
30 deg2
4.8 deg2
2 (8) km
10 km
Simulated ASKAP HI detections
(Johnston et al. 2007)
z = 0.45 to 1.0
one year observations
(8760 hours)
single telescope
pointing, assumes no
evolution in the
HI mass function
Light grey
30 dishes Tsys = 50 K
Dark grey
45 dishes Tsys = 35 K
MeerKAT ~4 times
more sensitive but
smaller field of view
Coadding HI
with the SKA Pathfinders
Optical Redshift Surveys
WiggleZ and
zCOSMOS
WiggleZ
zCOSMOS
Instrument/Telescope
AAOmega on the AAT
VIMOS on the VLT
Target Selection
ultraviolet using the
GALEX satellite
optical I band
IAB < 22.5
Survey Area
1000 deg2 total
7 fields minimum size of
~100 deg2
COSMOS field
single 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
200,000
20,000
WiggleZ and
zCOSMOS
WiggleZ
zCOSMOS
Instrument/Telescope
AAOmega on the AAT
VIMOS on the VLT
Target Selection
ultraviolet using the
GALEX satellite
optical I band
IAB < 22.5
Survey Area
1000 deg2 total
7 fields minimum size of
~100 deg2
COSMOS field
single 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
200,000
20,000
WiggleZ and
zCOSMOS
WiggleZ
zCOSMOS
Instrument/Telescope
AAOmega on the AAT
VIMOS on the VLT
Target Selection
ultraviolet using the
GALEX satellite
optical I band
IAB < 22.5
Survey Area
1000 deg2 total
7 fields minimum size
of ~100 deg2
COSMOS field
single 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
200,000
20,000
WiggleZ
and
ASKAP
WiggleZ field
square ~10
degrees
across
data as of
May 2009
z = 0.45 to 1.0
ASKAP
Field of View
Area 30 deg2
ASKAP & WiggleZ 100hrs
nz = 7009
ASKAP & WiggleZ 100hrs
nz = 7009
ASKAP & WiggleZ 100hrs
nz = 7009
ASKAP & WiggleZ 1000hrs
Can
break up
observations
among
multiple
WiggleZ
fields
nz = 7009
zCOSMOS
and
MeerKAT
zCOSMOS field
MeerKAT
beam size at
1420 MHz z = 0
MeerKAT
beam size at
1000 MHz z = 0.4
square ~1.3
degrees across
data as of
March 2008
z = 0.2 to 1.0
7118 galaxies
MeerKAT & zCOSMOS 100hrs
~65 per cent of
zCOSMOS galaies are
star-forming, blue, diskdominate galaxies
(Mignoli et al. 2008)
nz = 4627
MeerKAT & zCOSMOS 100hrs
nz = 4627
MeerKAT & zCOSMOS 100hrs
nz = 4627
MeerKAT & zCOSMOS 1000hrs
nz = 4627
HI Science
with SKA Pathfinders
at High Redshift
Why is there a
dramatic evolution in the
Cosmic Star Formation Rate Density
and only minimal evolution in the
Cosmic HI Gas Density?
SFRD & HI density Evolution
Star Formation Rate
Density Evolution
HI Density
Evolution
Evolution of HI Gas in Galaxies
log(SFR)  log(MHI)
SFR = a (MHI)m
HI =  MHI
SFRD =  SFR
Vol
Vol
SFRD = a ×  (MHI)m
Vol
m ~ 1.7 at z = 0 (Doyle & Drinkwater 2006)
Evolution of HI Gas in Galaxies
log(SFR)  log(MHI)
SFR = a (MHI)m
HI =  MHI
SFRD =  SFR
Vol
Vol
SFRD = a ×  (MHI)m
Vol
m ~ 1.7 at z = 0 (Doyle & Drinkwater 2006)
Evolution of HI Gas in Galaxies
log(SFR)  log(MHI)
SFR = a (MHI)m
HI =  MHI
SFRD =  SFR
Vol
Vol
SFRD = a ×  (MHI)m
Vol
m ~ 1.7 at z = 0 (Doyle & Drinkwater 2006)
Evolution of HI Gas in Galaxies
log(SFR)  log(MHI)
SFR = a (MHI)m
HI =  MHI
SFRD =  SFR
Vol
Vol
SFRD = a ×  (MHI)m
Vol
m ~ 1.7 at z = 0 (Doyle & Drinkwater 2006)
Evolution of HI Gas in Galaxies
log(SFR)  log(MHI)
SFR = a (MHI)m
HI =  MHI
SFRD =  SFR
Vol
Vol
SFRD = a ×  (MHI)m
Vol
m ~ 1.7 at z = 0 (Doyle & Drinkwater 2006)
Testing Ideas on
HI Gas
Evolution
Generated HI Mass Functions
Integrated HI density
= current value
(~5×107 M Mpc-3)
Integrated SFRD
= maximum value
observed
(~0.3 M yr-1 Mpc-3)
Generated HI Mass Functions
Integrated HI density
= twice current value
(~108 M Mpc-3)
Integrated SFRD
= maximum value
observed
(~0.3 M yr-1 Mpc-3)
Varying Galaxy SFR-HI Gas Relationship
SFR = a (MHI)m
Integrated HI density
= current value
(~5×107 M Mpc-3)
Integrated SFRD
= maximum value
observed
(~0.3 M yr-1 Mpc-3)
current values
Observational Evidence
Downsizing
• the bulk of the stellar populations of the most massive
galaxies formed at early times (Heavens et al. 2004, Thomas
et al. 2005 & others)
• the sites of active star formation shift from the high-mass
galaxies at earliest times to the lower-mass galaxies at later
periods (Cowie et al. 1996, Gunzman et al. 1997 & others)
• high mass galaxies with active star formation  highest
HI gas content?
• SKA pathfinders observations test hypotheses
Downsizing
• the bulk of the stellar populations of the most massive
galaxies formed at early times (Heavens et al. 2004, Thomas
et al. 2005 & others)
• the sites of active star formation shift from the high-mass
galaxies at earliest times to the lower-mass galaxies at later
periods (Cowie et al. 1996, Gunzman et al. 1997 & others)
• high mass galaxies with active star formation  highest
HI gas content?
• SKA pathfinders observations test hypotheses
Downsizing
• the bulk of the stellar populations of the most massive
galaxies formed at early times (Heavens et al. 2004, Thomas
et al. 2005 & others)
• the sites of active star formation shift from the high-mass
galaxies at earliest times to the lower-mass galaxies at later
periods (Cowie et al. 1996, Gunzman et al. 1997 & others)
• high mass galaxies with active star formation  highest
HI gas content?
• SKA pathfinders observations test hypotheses
Downsizing
• the bulk of the stellar populations of the most massive
galaxies formed at early times (Heavens et al. 2004, Thomas
et al. 2005 & others)
• the sites of active star formation shift from the high-mass
galaxies at earliest times to the lower-mass galaxies at later
periods (Cowie et al. 1996, Gunzman et al. 1997 & others)
• high mass galaxies with active star formation  highest
HI gas content?
• use SKA pathfinders observations to test hypotheses
Bonus
Material
Two Unusual
Radio Continuum Objects
in the Field of
Abell 370
1. The DP
Structure
Single RC
Single Radio
Contiuum
Source
Double RC
Double Radio
Contiuum
Source
The DP Structure
GMRT image
resolution
~3.3 arcsec
at 1040 MHz
Peak flux =
1.29 mJy/Beam
Total flux
density
~ 23.3 mJy
60 arcsec across
The DP Structure
V band
optical
image
from ANU
40 inch WFI
60 arcsec
across
The DP Structure
Radio contours
at
150, 300, 450,
600, 750, 900 &
1150 Jy/beam
RMS ~ 20 Jy
The DP Structure
Optical as
Contours
The DP Structure
Galaxies all at
similar
redshifts
z ~ 0.3264
The DP Group
The DP Group
Abell 370
~167 Mpc difference
between cluster
Abell 370 and
DP group in
commoving distance
NOT related objects
DP Group
group well outside
GMRT HI redshift
range
DP Structure
Galaxy 4 – source of DP Structure
The DP Group
The DP Group
10 arcmin square box
~2800 kpc at z = 0.326
galaxy group/small
cluster
Explaining the
Structure
DP 1
a galaxy
DP 2
pair of radio jets
DP 3
DP 4
DP 5
galaxy moving
through intercluster
medium
DP 6
DP 7
DP 8
currently I have the
radio jets orientated
along page with
respect to the
observer
DP 9
changing orientation
of the radio jets with
respect to the
observer
DP 10
DP 11
2. A Radio Gravitational
Arc?
Radio Arc
V band optical
image from
ANU 40 inch
Abell 370
cluster
8 arcmin square
Radio Arc
V band optical
image from
ANU 40 inch
Abell 370
cluster
8 arcmin square
Radio Arc
V band optical
image from
ANU 40 inch
image centred
on one of the
two cD galaxies
near the centre
of the Abell 370
cluster
50 arcsec square
Radio Arc
optical image
from Hubble
Space Telescope
optical arc in
Abell 370 was
the first detected
gravitational
lensing event by
a galaxy cluster
(Soucail et al.
1987)
Radio Arc
GMRT image
resolution
~3.3 arcsec
at 1040 MHz
Peak flux =
490 Jy/Beam
cD galaxy
Peak flux =
148 Jy/Beam
Noise ~20 Jy
noise
Radio Arc
Radio contours
at
80, 100, 120, 140,
180, 220, 260,
320, 380 & 460
Jy/beam
RMS ~ 20 Jy
Radio Arc
Optical as
Contours
Conclusion
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 the cosmic neutral gas density at z = 0.24 (look-back
time of ~3 billion years) has been measured and the value is consistent
with that from damped Lyα measurements
• galaxy cluster Abell 370 at z = 0.37 (look-back time of ~4 billion
years) has significantly more gas than similar clusters at z ~ 0
• the SKA pathfinders ASKAP and MeerKAT can measure the HI 21-cm
emission from galaxies out to z = 1.0 (look-back time of ~8 billion
years) using the coadding technique with existing optical redshift
surveys