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Neutral Hydrogen Gas in Star Forming
Galaxies at z=0.24
HI Survival Through Cosmic Times
Conference
Philip Lah
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Collaborators:Frank Briggs (ANU)
Jayaram Chengalur (NCRA) Matthew Colless (AAO)
Roberto De Propris (CTIO)Michael Pracy (ANU)Erwin de Blok (ANU)
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Talk Outline
Star Forming Galaxies at z = 0.24
• ‘Fujita sample’ of star-forming galaxies
• HI mass content by ‘coadding’
• HI mass vs. star formation rate
• radio continuum at z = 0.24
HI in Abell 370, a galaxy cluster at z=0.37
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The Fujita galaxies - H emission galaxies
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The Subaru Telescope
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H atz = 0.24
The Surprime-cam filters
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The Suprime-Cam Field
RA
DEC
24’ × 30’
Fujita et al. 2003 narrow
band imaging - H emission at
z=0.24
348 galaxies
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Cosmic Star Formation Rate
DensityHopkins
2004
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Cosmic Star Formation Rate
Density
Fujita et al. 2003
Hopkins 2004
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HI in the Fujita Galaxies
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Giant Metrewave Radio Telescope
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Giant Metrewave Radio Telescope
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GMRT data for the field
Time on Field
~44 hours
Observing Frequency
HIRedshift
1150 MHz 0.24
RMS per channel
~0.13 mJy
Primary Beam Size
Synthesis Beam Size
~29’ ~2.9’’
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Why HI detection is hard
z=0.05
z = 0.24
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Coadding of HI Signals
• pick out the HI signal using optical redshifts
• coadd faint signals to make the measurement
RA
DEC
Radio Data Cube
Frequen
cy
HI red
shift
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Anglo-Australian Telescope
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multi-object, fibre fedspectrograph
2dF instrument
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Fujita galaxies - B filter
thumbnails 10 arcsec
10 arcsec
ordered by increasing
H luminosity
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Fujita galaxies – 2dF redshifts
thumbnails 10 arcsec
10 arcsec
ordered by increasing
H luminosity
154 redshifts
121 useful
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Galaxy Sizes
To coadd the signal I need the galaxies to be unresolved. This allows me take the value in the radio data cube at the position and redshift
of galaxy as the total HI flux.
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Galaxy Sizes
To coadd the signal I need the galaxies to be unresolved. This allows me take the value in the radio data cube at the position and redshift
of galaxy as the total HI flux.
Complication!!Many of the galaxies are larger than GMRT
2.9’’ synthesis beam.
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Beam Smoothings
Estimate of Galaxy HI Diameter
Used relationship
between optical size and HI size
from Broeils & Rhee 1997
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Coadded HI
Spectrum
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HI spectrum all
neutral hydrogen gas measurement
using 121 redshifts - weighted average
MHI = (2.26
± 0.90) ×109 M
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The Cosmic Neutral Gas Density
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Zwaan et al. 2005HIPASSHI 21cm
Rao et al.2006DLAs
from MgII absorption Prochaska
et al. 2005DLAs
Cosmic Neutral Gas Density vs. Redshift
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my new point
Cosmic Neutral Gas Density vs. Redshift
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Cosmic Neutral Gas Density vs. Time
my new point
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Star Formation Rate &
HI mass
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HIPASS&
IRASdataz ~ 0
Doyle & Drinkwater
2006
Galaxy HI Mass vs Star Formation Rate
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HI Mass vs Star Formation Rate at z = 0.24
line from Doyle &
Drinkwater 2006
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Problem at High Redshift• at z > 1 factor ~10 increase in cosmic star formation rate
density
• if the SFR-HI mass relation holds true would lead to factor of ~4 increase in cosmic neutral gas density
• from damped Lyα systems see only a factor ~2 increase at high redshift (Prochaska et al. 2005)
• change in star formation mechanism – efficiency increased by a factor ~2
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Radio Continuum from
Star Forming Galaxies
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Sullivan et al. 2003Sullivan et al. 2001
Comparison of Star Formation Indicators at z 0
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Comparison at z = 0.24
line from Sullivan et al. 2001
45 gals
55 gals
236 gals
using all 348 gals
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HI in Abell 370, a galaxy cluster
at z = 0.37
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Galaxy Clusters
Butcher-Oemler effect (1978) • with increasing redshift galaxy clusters show a
higher fraction of optically blue galaxies (mostly
bright spirals & irregulars)
• effect noticeable from
z0.1
• strong effect by z=0.4
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Abell 370 Observations• radio observations with the GMRT of the
galaxy cluster totalling ~34 hours at 1040 MHz (HI 21 cm at z = 0.37)
• V, R & I band optical imaging using the SSO 40 inch telescope
• spectroscopic follow-up using AAOmega on the Anglo-Australian Telescope for 4 nights for optical redshifts
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Abell 370: RA & DEC
Blue V-I colour 0.9
Red V-I colour > 0.9
the galaxies are large -
luminosities L* or greater
GMRT Beam
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Abell 370: radius & z
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Abell 370: all
HI gas
measurement
278 redshifts
MHI =
(7.4 ± 2.6)
×109 M
Signal to Noise = 2.8
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Abell 370: blue and red
Blue Galaxies128 redshifts
MHI = (10.1 ± 4.1)×109 M
Signal to Noise = 2.5
Red Galaxies150 redshifts
MHI = (5.5 ± 3.4)×109 M
Signal to Noise = 1.6
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Conclusions
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Conclusions• HI 21cm emission is observable at moderate
redshifts using the coadding technique
• the measured cosmic neutral gas density at z=0.24 is consistent with that from damped Ly
• the radio continuum-H & SFR-HI mass correlations both hold at z=0.24 suggests that the process of star formation in field galaxies is not significantly different ~3 Gyr ago
• there is large amounts of HI gas at z=0.37 in galaxies within clusters and the gas is concentrated in the blue galaxies
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Additional Slides
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HI mass function
HIPASS out to
z~0.042Zwaan et al.
2005
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Redshift histogram
Histogram of Redshifts
Subaru Narrow Band Filter
GMRT HI freq range
154 redshifts
121 useful
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Smoothings - RMS
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Why use GMRT?
• GMRT collecting area
21 × ATCA 6.9 × WSRT 3.6 × VLA
• frequency coverage & bandwidth
• angular resolution
• position at low latitude
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GMRT data for the fieldGMRT
Observation Time
Time on Field
80.5 hours ~44 hours
Primary Beam Size
Synthesis Beam Size
~29’ ~2.9’’
Instantaneous Bandwidth
Number of Channels
Channel Bandwidth
Channel Width
32 MHz 2 × 128 125 kHz 32.6 kms-1
Observing Frequency
HIRedshift
1150 MHz 0.24
RMS per channel
Continuum RMS
~130 Jy 15 Jy
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GMRT Beam
Fujita galaxies
The Galaxy Positions
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GMRT Beam
Fujita galaxies
The Galaxy Positions
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Narrowband Filter: Hα detection
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Hα Luminosity Function
Fujita et al. 2003
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Merging/Interacting System
Contours - radio continuumGreyscale - H emission• 5 times brighter in H
Contours- radio continuumGreyscale - optical continuum• 0.6 times as bright in z' filter
108±24 Jy
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The End