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People involved:
Richard Hunstead Carole Jackson Sebastian Juraszek Michael Large Tom Mauch Tara Murphy Bruce McAdam Vincent McIntyre Barbara Piestrzynska Gordon Robertson Elaine Sadler
Tony Turtle George Warr
Molonglo: Duncan Campbell-Wilson Jeff Webb Michael White John Barry Adrian Blake Sydney: Anne Green Douglas Bock Edward Boyce Ben Chan Lawrence Cram David Crawford Ralph Davison
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Dedication
Prototype: SKAMP (10,000 m2) operating to 1 GHz by 2007
The Sydney University Molonglo Sky Survey is dedicated to our friend and colleague Dr Michael Large, whose expertise and vision made the project possible
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Wide-field images of the radio sky
‘Radio Schmidt’ telescope: 2.7o field of view, excellent surface-brightness sensitivity
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Images of the optical & radio sky
Optical Blue light: Mostly nearby galaxies (median z~0.1)
Radio 843 MHz: Mostly very distant radio galaxies (median z~1)
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SUMSS source populations
Jackson & Wall, 1999
Predicted radio-source population at 843MHz:
• Dominant population is radio galaxies (median z~1)
• 10% QSOs above ~100 mJy
• Increasing contribution from local starburst galaxies below ~10 mJy
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Radio galaxies & black holes
Radio synchrotron emission from collimated radio jets powered by an accretion disk around a supermassive black hole (Blandford & Rees 1978).
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Why the whole sky?
Radio telescopes are highly efficient machines for probing the distant universe and measuring the cosmic evolution of galaxies and their central black holes.
Developing a proper physical understanding of galaxy formation and evolution requires data sets much larger than those available in the past.
“The astronomy of the 21st century will be dominated by computer-based manipulation of huge homogeneous surveys of various types of astronomical objects.’’
Van den Bergh (2000), PASP 112, 4.
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Processing SUMSS data
Individual 2.7o diameter fields processed automatically in a data pipeline, then combined to produce final 4o x 4o mosaics with uniform sensitivity.
Mosaics are catalogued using ‘decision-tree’ artificial intelligence methods to remove telescope artefacts.
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Automated recognition and removal of telescope artefacts
Mauch, Murphy, Curran et al. (2003)
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SUMSS and NVSS
NVSS (1400 MHz) and SUMSS (843 MHz) surveys have similar sensitivity and resolution. Overlap at declination -30o to -40o
NRAO Very Large Array (VLA), New Mexico, USA
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SUMSS science goals
What does SUMSS do (particularly) well? Identify and study objects which are common:
Cross-match with optical redshift surveys to study global properties of AGN and star-forming galaxies at z~0, local benchmark for studies of cosmic evolution (Mauch, this meeting)
Identify and study objects which are rare: e.g. High-redshift radio galaxies (Klamer, this meeting)
Identify low surface-brightness radio sources: Complete samples of giant radio galaxies, relic sources, extended sources in the Galactic Plane
Identify and monitor transient sources: (Ball, this meeting)
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SUMSS and optical redshift surveys
Overlap with 2dF/6dF gives spectra of 10,000+ radio AGN and starburst galaxies.
Local radio luminosity functions and timescales; local benchmark for high-z studies.
6dFGS spectra
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NVSS/SUMSS radio sources in the 6dF Galaxy Survey
‘Main survey’ science:• Accurate radio luminosity functions for AGN, starbursts
• Clustering study via the 2-point Correlation function
• Accurate z=0 benchmarks for studies of cosmic evolution
‘Extra targets’ science: • Compact objects and some galaxies with blue colours (QSOs, starburst galaxies…)
A census of local radio sources:
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All-sky radio continuum surveys
NVSS
= 1.4 GHz
dec +90o to -40o
SUMSS = 843 MHz dec -30o to -90o
Both surveys have 45” beam, 3-6 mJy det. limit, position accuracy 1-2”<z> = 0.8 Only 1-2% of extragalactic radio sources in local universe (z < 0.1)
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The 6dF Galaxy Survey (6dFGS)
Primary Survey K-selected from 2MASS-XSC (2 Micron All Sky Survey eXtended Source Catalog)• K < 12.75• All southern sky except |b| < 10deg• 113,000 objects over 15,000deg2
Selection from CCD photometry• Accurate K-band magnitudes!• Measures old stellar population• Dust extinction less problematic in K-band than at shorter
wavelengths 1500 fields means 75 targets per field Spare fibres for “additional targets”
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Radio Source Detection
Primary Sample (K<12.75):• Preliminary list of all NVSS/SUMSS radio sources within 30”
of 2MASS-XSC (~18%).• Confirmed identifications by eye• 4506 out of ~29000 observed objects in first data release
accepted as genuine (~16% detection rate) Additional Targets:
• NVSS/SUMSS Radio sources within 10” of ‘extended’ objects and 5” of ‘stellar’ objects with B<18 in the SuperCOSMOS database
• 6997 NVSS (dec.>-40o) and 2614 SUMSS (dec.<-50o) additional targets
• 1191 NVSS (17%) and 6 SUMSS (0.2%) observed serendipitously in first data release
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Radio Sources in the Primary 2MASS-XSC Sample
4506 NVSS radio sources in 6dF-DR1• 16% Detection rate
109 SUMSS• 7.6% Detection rate
Spectral classification for NVSS:• 1268 Aa• 162 Ae• 187 Aae• 2644 SF• 8 Star• 235 Unclassifiable (Low S/N spectra)
40% AGN , 60% SF (2dFGRS: 60% AGN , 40% SF)Largest local (z<0.1) sample of radio source redshifts ever
obtained!
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Local radio luminosity functions
1569 AGNs-Dominate radio source population above P1.4=1023 W/Hz- AGN radio luminosity function has power-law form for 4 decades of radio power.- Unaffected by cosmic
evolution (<V/Vmax>=0.51±0.01)
2507 Star-forming galaxies - Dominate radio source population below P1.4=1023 W/Hz- All lie on radio-FIR correlation
(Mauch 2005)
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Local star-formation density
Zero point of Madau diagram
• P1.4 measures star-formation rate (Sullivan et al. 2001).• Star-formation rate derived from P1.4 is free from dust extinction.• Local SF density agrees with optical and IR values.
Local SF density=(0.021±0.001) Msun yr-1 Mpc-3
(Mauch 2005)
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Fractional radio luminosity function
AGNs
• Many galaxies contribute to AGN luminosity function so can separate into MK bins to compute fractional LF.• Use preliminary 6dFGS K-band luminosity function (Jones et al. in prep.)
• Gives probability that a galaxy of a given near-infrared magnitude is a radio source above a given radio power.• Fraction of galaxies hosting AGN increases with MK
corresponding to an increase with black hole mass via MBH-Mbulge relation.
(Mauch 2005)
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Real-space 2 point correlation function[Mauch & Rawlings]
All SF AGN
ro=7.9±0.6 Mpc0 Mpc<s<40 Mpc
ro=7.9±0.7 Mpc0 Mpc<s<40 Mpc
ro=12.6±0.9 Mpc0 Mpc<s<40 Mpc
Magliocchetti et al.(2004): ro=10.9±1.0 Mpc (AGN), ro=7.9±0.6 Mpc (ALL)
Norberg et al. (2002) (2dFGRS Galaxies): bright early types: ro=13.85±1.7 Mpcfaint late-type: ro=5.2±1.1 Mpcbright late-type: ro=9.0±1.4 Mpc
Radio sources cluster in a similar fashion to the optical host galaxy population.
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SUMSS science goals
What does SUMSS do (particularly) well? Identify and study objects which are common:
Cross-match with optical redshift surveys to study global properties of AGN and star-forming galaxies at z~0, local benchmark for studies of cosmic evolution (Mauch, this meeting)
Identify and study objects which are rare: e.g. High-redshift radio galaxies (Klamer, this meeting)
Identify low surface-brightness radio sources: Complete samples of giant radio galaxies, relic sources, extended sources in the Galactic Plane
Identify and monitor transient sources: (Ball, this meeting)
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Searching for the earliest massive galaxies in the universe
1) Radio filter 1.3, NVSS-SUMSS)
2) IR (K-band) imaging to estimate z
3) Optical/IR spectra (8m telescopes)
(Chambers et al. 1996; De Breuck et al. 2000)(Mauch et al. 2003)
Radio spectral index,
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SUMSS science goals
What does SUMSS do (particularly) well? Identify and study objects which are common:
Cross-match with optical redshift surveys to study global properties of AGN and star-forming galaxies at z~0, local benchmark for studies of cosmic evolution (Mauch, this meeting)
Identify and study objects which are rare: e.g. High-redshift radio galaxies (Klamer, this meeting)
Identify low surface-brightness radio sources: Complete samples of giant radio galaxies, relic sources, extended sources in the Galactic Plane
Identify and monitor transient sources: (Ball, this meeting)
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Effective u-v weighting of the MOST
synthesized beam
Excellent uv coverage allows detection and imaging of extended, low-surface brightness radio emission
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A complete sample of Mpc-sized double radio galaxies from SUMSS
Saripalli et al. 2005, AJ 130, 896
SGRS J0331-7710: Largest-known SUMSS radio galaxy, z=0.146, projected linear size = 2.67 Mpc
Giant radio galaxies (sizes > 0.7 Mpc) are believed to represent the final stages of radio galaxy evolution.
SUMSS complete sample south of dec -50o, volume density is roughly one per (215 Mpc)3
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Giant radio galaxies: J0515-8100
Subrahmanyan et al. 2005, ApJ in press
• Projected linear size = 1.0 Mpc
• Lowest-known surface brightness for a double radio galaxy
• Host galaxy interacting with fainter companion; perturbations in jet axis produce the ‘fat’ radio lobes
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X-ray transient XTE 1550-564
Hannikainen et al. 2001
The fixed format of the Molonglo telescope makes it ideal for finding and monitoring transient and variable radio
sources.
Radio emission from a Galactic soft X-ray transient source
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SUMSS data release policy
www.astrop.physics.usyd.edu.au/SUMSS
Imaging survey of the entire southern sky now >95% complete.
FITS images and catalogue are released on the web, and incorporated into international databases (NASA Skyview, NED)
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What next?
• SUMSS now >95% complete, will be finished by early 2006.
• The data products (images and catalogue) are available online, have already been used in a wide range of analyses (Galactic plane, nearby galaxies, distant galaxies, large-scale structure), and will continue to be used in the future.
• From 2006 the Molonglo telescope will undergo a further upgrade as a technology prototype for the Square Kilometre Array (SKAMP), allowing it to survey polarized sources and measure the redshifted 21cm line of neutral hydrogen in distant galaxies.
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Energy output from a black hole
Energy output is set by the accretion rate onto the black hole. The Eddington limit is the maximum rate at which gas can be accreted. Above this, the luminosity is so high that radiation pressure prevents further inflow. Eddington limit is higher for more massive black holes.
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The AT 20GHz survey
• First all-sky radio survey at mm wavelengths
• Catalogue foreground discrete-source population for future CMB missions (variability, polarization particularly important).
• Set up new calibration network for ATCA, ALMA at 20-100 GHz
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SUMSS and the AT20GHz survey
AT20G detects only a small subset of low-frequency (NVSS/ SUMSS) radio sources, but almost all AT20G sources are in the SUMSS and/or NVSS
catalogues -
Most optical IDs are stellar (QSO candidates), many are 6dFGS ‘additional targets’
SUMSS
AT20G
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