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The HI gas content of galaxies around Abell 370, a galaxy cluster at z = 0.37
Philip Lah
International SKA Forum 2010 A New Golden Age for Radio Astronomy


Collaborators:
Frank Briggs (ANU) Michael Pracy (Swinburne) Jayaram Chengalur (NCRA) Matthew Colless (AAO) Roberto De Propris (CTIO)


Method:
Coadding the HI signals from distant galaxies using the galaxies' known optical positions and redshifts


Giant Metrewave Anglo-Australian Radio Telescope Telescope

India

Australia


Nearby Galaxy Clusters Are Deficient in HI Gas

The Coma Cluster


So why target moderate redshift clusters for HI gas?


The Butcher-Oemler Effect

Blue Fraction, fB

Redshift, z


The Butcher-Oemler Effect

Blue Fraction, fB

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

GMRT ~34 hours on cluster optical imaging ANU 40 inch telescope spectroscopic follow-up with the AAT
Abell 370 cluster core, ESO VLT image


redshift histogram
324 useful redshifts from AAT observations


redshift histogram
324 useful redshifts from AAT observations

GMRT sideband frequency limits


Abelll370 galagy claxy cluster Abel 370 x al uster

324 galaxies 105 blue (B-V 0.57)
219 red (B-V > 0.57)


Abelll370 galagy claxy cluster Abel 370 x al uster
3 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 galaxies 94

156 galaxies

The galaxies around Abell 370 ar168 galaxies ea 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

11 blue galaxies within intra-cluster hot x-ray156sgalppear ga a axies HI deficient 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


Distribution of galaxies around Abell 370
complete GMRT redshift range

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


Distribution of galaxies around Abell 370
8 Mpc radius region

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


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


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 & 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
Average 81 blue [OII] emission galaxies

87 red [OII] emission galaxies

line from Doyle & Drinkwater 2006


Star Formation Rate from [OII] Emission and Radio Continuum Emission


Radio Continuum vs. [OII] Star Formation Rate
Average all 168 [OII] emission galaxies

line from Bell 2003


Radio Continuum vs. [OII] Star Formation Rate
Average

87 red [OII] emission galaxies 81 blue [OII] emission galaxies line from Bell 2003


Conclusion


Conclusion
· Abell 370, a galaxy cluster at redshift z = 0.37 (~4 billion years ago) contains significantly more HI gas than observed in similar nearby clusters
· however the 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 galaxy clusters
· despite their high HI mass the galaxies around Abell 370 appear normal; they have HI Mass to Light Ratio and a Star Formation Rate to HI Gas correlation similar to that seen in nearby galaxies

Paper: Lah et al. 2009 MNRAS.399.1447L


Conclusion
· Abell 370, a galaxy cluster at redshift z = 0.37 (~4 billion years ago) contains significantly more HI gas than observed in similar nearby clusters
· however the 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 galaxy clusters
· despite their high HI mass the galaxies around Abell 370 appear normal; they have HI Mass to Light Ratio and a Star Formation Rate to HI Gas correlation similar to that seen in nearby galaxies

Paper: Lah et al. 2009 MNRAS.399.1447L


Conclusion
· Abell 370, a galaxy cluster at redshift z = 0.37 (~4 billion years ago) contains significantly more HI gas than observed in similar nearby clusters
· however the 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 galaxy clusters
· despite their high HI mass the galaxies around Abell 370 appear normal; they have HI Mass to Light Ratio and a Star Formation Rate to HI Gas correlation similar to that seen in nearby galaxies

Paper: Lah et al. 2009 MNRAS.399.1447L



Additional Slides


SKA tpathfutders For he Fin ure
The SKA pathfinders ASKAP and MeerKAT can measure the HI 21-cm emission from galaxies out to redshift z = 1.0 using the coadding technique with existing optical redshift surveys.


Colour ­ Mag Diagrams -all


Colour ­ Mag Diagrams -inner


WFI selection


Abell 370 ­ R band images
Thumbnails 10'' sq

324 galaxies with useful redshifts (z~0.37)

Ordered by observed R band magnitudes


HI all spectrum
all Abell 370 galaxies neutral hydrogen gas measurement

using 324 redshifts ­ large smoothing

MHI = (6.6 3.5) 109 M


HI Flux ­ All Galaxies


HI blue outside x-ray gaue s bl

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 Flux ­ Blue Galaxies Outside X-ray Gas


HI 21cm emission at z > 0.1
Telescope
WSRT VLA

Redshift
z = 0.18 Abell 2218 z = 0.19 Abell 2192

Obs Time
200 hours ~80 hours

Number and HI Mass of galaxies
1 galaxy 4.8 109 M 1 galaxy 7.0 109 M


Who and When
Zwaan et al. 2001 Verheijen et al. 2004



WSRT

two clusters 42 galaxies at z = 0.19 & 420 hours 5 109 to 4 1010 M z = 0.21
z = 0.17 to 0.25 2 to 6 hours per galaxy 26 galaxies (2 to 6) 1010 M



Verheijen et al. 2007
Catinella et al. 2007

Arecibo




Average HI Mass Comparisons with Coma


Abell 370 and Coma Comparison

110 galaxies

324 galaxies

214 galaxies


Abell 370 and Coma Comparison

110 galaxies

324 galaxies

214 galaxies


Abell 370 and Coma Comparison

110 galaxies

324 galaxies

214 galaxies


Why target moderate redshift clusters?
· the cluster core to the cluster outskirts are within the field of view of a radio telescope at moderate redshifts · the number density of galaxies around a cluster is significantly higher than a typical field pointing · the Butcher-Oemler effect


Why target moderate redshift clusters?
· the cluster core to the cluster outskirts are within the field of view of a radio telescope at moderate redshifts · the number density of galaxies around a cluster is significantly higher than a typical field pointing · the Butcher-Oemler effect


Why target moderate redshift clusters?
· the cluster core to the cluster outskirts are within the field of view of a radio telescope at moderate redshifts · the number density of galaxies around a cluster is significantly higher than a typical field pointing · the Butcher-Oemler effect