the evolution of stars and gas in galaxies: phd midterm philip lah a journey with noise and...
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The Evolution of Stars and Gas in Galaxies:
PhD Midterm
Philip Lah
A journey with noise and astrometry
Supervisor: Frank Briggs
Supervisory Panel:
• Erwin de Blok (RSAA)
• Jayaram Chengalur (National Centre for Radio Astrophysics, India)
• Matthew Colless (Anglo-Australian Observatory)
• Roberto De Propris (Cerro Tololo Inter-American Observatory, Chile)
Those that deserve special mentions:
• Brian Schmidt
• Agris Kalnajs
• Michael Pracy
• Tony Martin-Jones
• Scott Croom (AAO) & Rob Sharp (AAO)
• Nissim Kanekar (NRAO)
Goal of PhD
• to relate the star formation rate, the stellar mass and the mass in neutral hydrogen gas in galaxies as they evolve
• to examine galaxy evolution over last 4 Gyr, (a third of the age of the universe, z~0.4)
• to study galaxies in a variety of different environments
• UNIQUE PART to study galaxy properties in the same systems – optically selected galaxies
HI emission• HI – single atom of hydrogen – radiation from an excited state were proton & electron have the same spin - 10 million year half life• Assuming an optically thin neutral hydrogen cloud
• MHI* = 6.3 ×109 M (HIPASS, Zwaan et al. 2005)
1
2
1
236
kms
V
Mpc
d
mJy
S
zM
M LHI
Previous highest redshift HI
Westerbork Synthesis Radio Telescope (WSRT)
Netherlands
Abell 2218 z = 0.18
integration time 36 days, Zwaan et al. 2001
Very Large Array (VLA)
Abell 2192 z = 0.1887
integration time ~80 hours, Veheijen et al. 2004
GMRT Collecting Area
30 dishes of 45 m diameter
GMRT Collecting Area
21 × ATCA
15 × Parkes
6.9 × WSRT
3.6 × VLA
Method of HI Detection
RA
DEC
Radio Data Cube
• pick out HI signal using optical redshifts
• coadd faint signals to make measurement
Table of Targets
Target Type zLook Back
TimeGMRT Obs
Time
Subaru Fieldfield galaxies
with H emission
0.24 2.8 Gyr 80.5 hours
Abell 370cluster and
surroundings0.37 4.0 Gyr 70 hours
Cl0024+1654cluster and
surroundings0.39 4.2 Gyr 18 + 45 hours
HI Abell 37033 literature
redshifts but σz ≥ ± 300 kms-1
Upper limit MHI = 1.3 MHI
*
with 95% confidence
Galaxy Cluster Abell 370
• need more redshifts for reasonable analysis
• the plan is to use WFI on SSO 40 inch for imaging – Mike Pracy took some data last year and hopefully take more this year
• hopefully use AAOmega for spectroscopic follow-up in October/November 2006
• also made improvements to my data reduction methods so redo reduction
Subaru Field
RA
DEC
24’ × 30’
Fujita et al. 2003 narrow band imaging - H emission
flux
We used 2dF to get redshifts
SDF positions
GMRT beam 10% level
GMRT beam 50% level
Blue Points Subaru galaxies
Red Points NVSS Radio Continuum
Sources
Sad cont sources
From AIPS auto detection routine -
SAD
Blue > 5 mJyRed > 1 mJy
Black > 0.32 mJyGrey > 80 Jy
RMS ~ 16 Jy
SubaruField
boundary
Astrometry
• need optical and radio positions to agree to a high level of precision
• shift in radio data – corrected by comparing with FIRST continuum source positions
• optical data – PROBLEM coordinates that I had been given for the Subaru galaxies rounded to the 5th decimal place before converting to degrees/hours, minutes, seconds format
eg. 10.56479302 10.56479 10h 33m 53.24s
Position change
Rounding error:
0.18’’ DEC2.7’’ RA
PROBLEMS2dF fibre
diameter is 2’’
many galaxies
smaller than 2’’
Sullivan et al. 2003
Sullivan et al. 2001
H Luminosity vs.
1.4 GHz Luminosity
&
UV Luminosity vs.
1.4 GHz Luminosity
Redshift histogram
Subaru Narrow Band Filter
FWHM (120 Å)
GMRT HI freq range
112 redshifts in GMRT data
Galaxy Sizes
Thumbnails 10’’ sq
Ordered by H
luminosity
Variety of sizes –
measured size at 25th
mag arcsec-2 isophote
Diameter HI
unsmoothed beam
FWHM ~3’ (10 kpc)
smoothed beam FWHM ~5.3’
(20 kpc)
smoothed beam FWHM ~8.0’
(30 kpc)
HI spectrum bright
Log H Luminosity
> 41 erg s-1
36 redshifts
Neutral Hydrogen
measurement
MHI = 0.57
0.26 MHI*
HI spectrum faint
Log H Luminosity
40.4 erg s-1
33 redshifts
Neutral Hydrogen
measurement
MHI = 0.31
0.19 MHI*
HI spectrum mid
40.4 < Log H Luminosity
41 erg s-1
43 redshifts
Neutral Hydrogen
measurement
MHI = 0.44 0.20 MHI
*
HI redshift mine all
taking into account
narrow band (H) filter
shape – brighter
galaxies will be seen over
a larger volume
Cl0024+1654 Data
• HST imaging 2181 galaxies with morphologies of which 195 spectroscopically confirmed cluster members (Treu et al. 2003)
• Hα narrow band imaging with Subaru star formation rates (Kodama et al. 2004)
• 296 literature redshifts within HI frequency limits of the GMRT observation (Cszoke et al. 2001)
• 18 + 45 hours GMRT observations
PhD Timetable of CompletionRest of 2006:
• finish analysis of the Subaru Field (to be completed by the end of August 2006)
• analysis of galaxy cluster Cl0024+1652 (analysis to be finished by January 2007)
• optical imaging of galaxy cluster Abell 370 using SSO 40 inch and AAOmega follow-up to get redshifts – Mike Pracy doing much of this but I will be involved
2007:
• complete analysis of galaxy cluster Abell 370 (to be finished no later than June 2007)
• write up my thesis throughout 2007 finish between September 2007 & March 2008 (3½ - 4 year mark)
Method of HI Detection
• individual galaxies HI 21cm emission below radio observational detection limits
• large sample of galaxies with known positions & precise redshifts (from optical observations)
• coadd weak HI signals isolated in position & redshift (velocity) space
• measure integrated HI signal – total HI mass of whole galaxy population – can calculate the average HI galaxy mass
Galaxy Cluster Abell 370
• originally started working on this data in 3 month project – worked on to learn radio astronomy
• 42 literature redshifts for Abell 370 cluster members 33 are usable – large error in σz ≥ ± 300 kms-1 (from Soucail et al. 1988 )