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Collaborators:
Jayaram Chengalur (NCRA)
Michael Pracy (ANU)
Frank Briggs (ANU)
Matthew Colless (AAO)
Roberto De Propris (CTIO)
Talk OutlineIntroduction• evolution in clusters & star formation rate density vs redshift• HI 21-cm emission & the HI coadding technique• review of current HI measurements at z > 0.1
Abell 370, a Galaxy Cluster at z = 0.37• HI in Abell 370• star formation in Abell 370• two unusual radio continuum objects around Abell 370
Future Observations with SKA pathfinders• using ASKAP and WiggleZ• using MeerKAT and zCOSMOS
Butcher-Oemler EffectButcher-OemlerEffect
increasing fraction of blue
galaxies in clusters with
redshift
nearby clusters neutral hydrogen
gas deficient
HI Gas and Star Formation
Neutral atomic hydrogen gas
cloud (HI)
molecular gas cloud (H
2)
star formation
HI 21cm emission at z > 0.1• single galaxy at z = 0.176 WSRT 200 hours (Zwaan
et al. 2001, Science, 293, 1800)
• single galaxy at z = 0.1887 VLA ~80 hours
(Verheijen et al. 2004,in IAU Symposium Vol 195, p. 394)
• two galaxy clusters at z = 0.188 and z = 0.206 WSRT 420 hours
42 galaxies detected HI gas masses 5109 to 41010 M
(Verheijen et al. 2007, ApJL, 668, L9)
• galaxies with redshifts z = 0.17 to 0.25 observed with Arecibo
detected 26 from 33 observed HI gas masses (2 to 6) 1010 M
(Catinella et al. 2007, in IAU Symposium Vol 235, p. 39)
HI 21cm emission at z > 0.1• single galaxy at z = 0.176 WSRT 200 hours (Zwaan
et al. 2001, Science, 293, 1800)
• single galaxy at z = 0.1887 VLA ~80 hours
(Verheijen et al. 2004,in IAU Symposium Vol 195, p. 394)
• two galaxy clusters at z = 0.188 and z = 0.206 WSRT 420 hours
42 galaxies detected HI gas masses 5109 to 41010 M
(Verheijen et al. 2007, ApJL, 668, L9)
• galaxies with redshifts z = 0.17 to 0.25 observed with Arecibo
detected 26 from 33 observed HI gas masses (2 to 6) 1010 M
(Catinella et al. 2007, in IAU Symposium Vol 235, p. 39)
HI 21cm emission at z > 0.1• single galaxy at z = 0.176 WSRT 200 hours (Zwaan
et al. 2001, Science, 293, 1800)
• single galaxy at z = 0.1887 VLA ~80 hours
(Verheijen et al. 2004,in IAU Symposium Vol 195, p. 394)
• two galaxy clusters at z = 0.188 and z = 0.206 WSRT 420 hours
42 galaxies detected HI gas masses 5109 to 41010 M
(Verheijen et al. 2007, ApJL, 668, L9)
• galaxies with redshifts z = 0.17 to 0.25 observed with Arecibo
detected 26 from 33 observed HI gas masses (2 to 6) 1010 M
(Catinella et al. 2007, in IAU Symposium Vol 235, p. 39)
HI 21cm emission at z > 0.1• single galaxy at z = 0.176 WSRT 200 hours (Zwaan
et al. 2001, Science, 293, 1800)
• single galaxy at z = 0.1887 VLA ~80 hours
(Verheijen et al. 2004,in IAU Symposium Vol 195, p. 394)
• two galaxy clusters at z = 0.188 and z = 0.206 WSRT 420 hours
42 galaxies detected HI gas masses 5109 to 41010 M
(Verheijen et al. 2007, ApJL, 668, L9)
• galaxies with redshifts z = 0.17 to 0.25 observed with Arecibo
detected 26 from 33 observed HI gas masses (2 to 6) 1010 M
(Catinella et al. 2007, in IAU Symposium Vol 235, p. 39)
HI 21cm emission at z > 0.1
• our group using the GMRT measured the coadded HI
signal from 121 star forming galaxies at z = 0.24 (look-
back time ~3.8 Gyr)
GMRT ~48 hours on field
weighted average MHI = (2.26 ± 0.90) ×109 M
(Lah et al. 2007, MNRAS, 376, 1357)
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 – R band imagesThumbnails
10’’ sq
324 galaxies with useful
redshifts (z~0.37)
ordered by observed
R band magnitudes
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
Galaxy Sizes
I want galaxies to be unresolved. For the galaxies at
z = 0.24 I used an estimate of the HI size from the optical
properties of spiral and irregular field galaxies and the
smoothed radio data.
Major Complication!!The Abell 370 galaxies are a mixture of early and late types
in a variety of environments.
Galaxy Sizes
I want galaxies to be unresolved. For the galaxies at
z = 0.24 I used an estimate of the HI size from the optical
properties of spiral and irregular field galaxies and the
smoothed radio data.
Major Complication!!The Abell 370 galaxies are a mixture of early and late types
in a variety of environments.
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
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)
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
• radio continuum emission produced from relativistic electrons moving in
magnetic field of the galaxy - synchrotron radiation
• relativistic electrons produced by supernova remnants, what remains after
the death of massive, short-lived stars
• in theory - number of supernova remnants related to star formation rate in
galaxy
• in practice - empirical relationship - agrees with other star formation rate
indicators
Radio Continuum – Star Formation Connection
Radio Continuum vs. [OII] Star Formation Rate
all 168 [OII]
emission galaxies
line fromBell 2003
Average
Radio Continuum vs. [OII] Star Formation Rate
line fromBell 2003
81 blue [OII]
emission galaxies
87 red [OII] emission galaxies
Average
The De Propris StructureGMRT image
resolution ~3.3 arcsec
at 1040 MHz
Peak flux = 1.29 mJy/Beam
Total flux density
~ 23.3 mJy
~167 Mpc differencebetween cluster
Abell 370 and De Propris group in comoving distance
NOT related objects
group well outside GMRT HI redshift
range
The De Propris Group
Abell 370
De Propris Group
The De Propris Group10 arcmin square box ~2800 kpc at z = 0.326
galaxy group/small cluster
galaxies moving through intra-group medium of
hot ionised gas
ionised gas pushes radio jet bending it back on
itself to create the strange shape
Radio ArcV 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 Arcoptical 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
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 – also do science
• SKA promises both high sensitivity with wide field of view
• possible SKA sites – South Africa and Australia
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 700 – 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 700 – 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 700 – 2500MHz
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 = 0.45 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)
MeerKAT - will detect galaxies easier - more sensitive - but in a single pointing will
end up with fewer total detections due to smaller field of view
z = 0.45 to 1.0
980 MHz to 700 MHz
one year observations (8760 hours)
Simulated ASKAP HI detections
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 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 field
data as of March 2008 z = 0.45 to 1.0
ASKAP beam size
Diameter 6.2 degreesArea 30 deg2
~10 degrees across
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
• Abell 370 a galaxy cluster at z = 0.37 has significantly more gas than
similar clusters at z ~ 0
• despite this fact, galaxies in regions of higher density within Abell 370
have less gas than galaxies located in regions of lower density, the same
trend seen in nearby clusters
• there are two unusual radio continuum structures in the field of
Abell 370 – a twisted radio jet and a possible radio gravitational arc
• the SKA pathfinders ASKAP and MeerKAT can measure significant
amounts of HI 21 cm emission out to z = 1.0 using the coadding
technique with existing redshift surveys
Conclusion