neutral hydrogen gas in abell 370, a g alaxy c luster at z = 0.37

Neutral Hydrogen Gas in Abell 370, a Galaxy Cluster at z = 0.37

NCRA 17th July 2008

Philip Lah

Collaborators:

Jayaram Chengalur (NCRA)

Michael Pracy (ANU)

Frank Briggs (ANU)

Matthew Colless (AAO)

Roberto De Propris (CTIO)

Giant Metrewave Radio Telescope

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

Evolution in Galaxy Clusters

Galaxy Cluster: Coma

Butcher-Oemler EffectButcher-OemlerEffect

increasing fraction of blue

galaxies in clusters with

redshift

nearby clusters neutral hydrogen

gas deficient

The Cosmic Star Formation Rate

Density

SFRD vs z

Hopkins 2004

HI Gas and Star Formation

Neutral atomic hydrogen gas

cloud (HI)

molecular gas cloud (H

2)

star formation

Neutral Atomic Hydrogen (HI)

21-cm Emission

Neutral atomic hydrogen creates 21 cm radiation

proton electron


photon

HI 21cm Emission at

High Redshift

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

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

redshift histogram

324 useful redshifts

redshift histogram

324 useful redshifts

GMRT sideband frequency

limits

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 all spectrumall 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 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 Flux – Blue Galaxies Outside X-ray Gas

Comparisons with the

Literature

Average HI Mass Comparisons with

Coma

Abell 370 and Coma Comparison

214 galaxies

324 galaxies

110 galaxies

HI Density Comparisons

HI density field

HI density - inner regions of clusters

within 2.5 Mpc of cluster centers

HI Mass to Light Ratios

HI Mass to Light Ratios

HI mass to optical B band luminosity for

Abell 370 galaxies

Uppsala General Catalog

Local Super Cluster

(Roberts & Haynes 1994)

Galaxy HI mass vs

Star Formation Rate

Galaxy HI Mass vs Star Formation Rate

HIPASS&

IRASdataz ~ 0

Doyle & Drinkwater

2006

HI Mass vs Star Formation Rate in Abell 370

all 168 [OII]

emission galaxies

line from Doyle &

Drinkwater 2006

Average

HI Mass vs Star Formation Rate in Abell 370

81 blue [OII]

emission galaxies

line from Doyle &

Drinkwater 200687 red [OII]

emission galaxies

Average

Star Formation Rate from [OII] and

radio continuum emission

• 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

Two Unusual Radio Continuum Objects

in the field of Abell 370

1. The De Propris Structure

Example Radio Continuum Jet

The De Propris StructureFIRST image

60 arcsec across

VLA at 1.4 GHz

Resolution ~5 arcsec

The De Propris StructureGMRT image

resolution ~3.3 arcsec

at 1040 MHz

Peak flux = 1.29 mJy/Beam

Total flux density

~ 23.3 mJy

The De Propris Structure

V band optical image

from ANU 40 inch WFI


Radio contoursat

150, 300, 450, 600, 750, 900 & 1150 Jy/beam

RMS ~ 20 Jy


Optical as Contours


Galaxies all at similar

redshifts z ~ 0.3264

The De Propris Group

~167 Mpc differencebetween cluster

Abell 370 and De Propris group in comoving distance

NOT related objects

group well outside GMRT HI redshift

range


Abell 370

De Propris Group

De Propris Structure

Galaxy 4 – source of De Propris Structure


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

2. A Radio Gravitational Arc?

Radio ArcV band optical

image from ANU 40 inch

Abell 370 cluster

8 arcmin square

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

Radio Arc

Radio contoursat

80, 100, 120, 140, 180, 220, 260,

320, 380 & 460 Jy/beam

RMS ~ 20 Jy

Radio Arc

Optical as Contours

Future Observations -HI coadding with SKA Pathfinders

SKA – Square Kilometer Array

• final site decision by 2012?? – money will be the deciding factor

• both South Africa and Australia are building SKA pathfinder telescopes to strengthen their case for site selection – also do science

• SKA promises both high sensitivity with wide field of view

• possible SKA sites – South Africa and Australia

Why South Africa

and Australia?

Population Density – India

Population Density – South Africa

Population Density – Australia

Radio Interference

108 109

Frequency (Hz)

The SKA Pathfinders

MeerKAT

South African SKA pathfinder

ASKAP and MeerKAT parametersASKAP MeerKAT

Number of Dishes 45 80

Dish Diameter 12 m 12 m

Aperture Efficiency 0.8 0.8

System Temp. 35 K 30 K

Frequency range 700 – 1800 MHz 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

What I could do with

the SKA pathfinders

using optical coadding of HI

if you gave them to me

TODAY.

WiggleZ and zCOSMOSWiggleZ zCOSMOS

Instrument/Telescope AAOmega on the AAT VIMOS on the VLT

Target Selectionultraviolet using the

GALEX satelliteoptical I band

IAB < 22.5

Survey Area1000 deg2 total

7 fields minimum size of ~100 deg2

COSMOS fieldsingle field

~2 deg2

Primary Redshift Range

0.5 < z < 1.0 0.1 < z < 1.2

Survey Timeline 2006 to 2010 2005 to 2008

nz by survey end 176,000 20,000

nz in March 2008 ~62,000 ~10,000

WiggleZ and

ASKAP

WiggleZ field

data as of March 2008 z = 0.45 to 1.0

ASKAP beam size

Diameter 6.2 degreesArea 30 deg2

~10 degrees across

ASKAP & WiggleZ 100hrs

nz = 3887

ASKAP & WiggleZ 1000hrs

nz = 3887

zCOSMOS and

MeerKAT

zCOSMOS field

data as of March 2008 z = 0.2 to 1.0

7118 galaxies

MeerKAT beam size at

1420 MHz z = 0

MeerKAT beam size at

1000 MHz z = 0.4

square ~1.3 degrees across

MeerKAT & zCOSMOS 100hrs

nz = 3559

MeerKAT & zCOSMOS 1000hrs

nz = 3559

Conclusion

• 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

Additional Slides

• RFI – 950 MHz mobile phones

• Field of view small – 45 m dishes

• bandpass small 32 MHz – upgrade coming but will not

soon work for all dishes simultaneously

• longer baselines resolve HI in galaxies

Why not GMRT?

neutral hydrogen gas in abell 370, a g alaxy c luster at z = 0.37

Documents

redshifts z

single galaxy

hours verheijen

observed hi gas masses

hours zwaan

iau symposium vol

galaxy clustersgalaxy

l9 galaxies