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GeorgeMiley LOFAR May06

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Information about GeorgeMiley LOFAR May06
Science-Technology

Published on August 29, 2007

Author: CoolDude26

Source: authorstream.com

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HIGH-REDSHIFT RADIO GALAXIESGeorge Miley :  HIGH-REDSHIFT RADIO GALAXIES George Miley WHY ARE THEY INTERESTING? short RELEVANCE OF RADIO SPECTRA IMPORTANCE OF LONG BASELINES Surveys Spatial distributions Spatial correlations and statistics of USS sources WHY STUDY DISTANT LUMINOUS RADIO GALAXIES - 1?> 350 known with 2 < z < 5.2:  WHY STUDY DISTANT LUMINOUS RADIO GALAXIES - 1? andgt; 350 known with 2 andlt; z andlt; 5.2 Nuclei Formation of massive black holes Timeline of massive black holes relevant to galaxies Hosts Formation of massive galaxies Most luminous galaxies in early Universe Clumpy: Test beds of hierarchical galaxy formation Environments Formation of rich clusters Generally surrounded by protoclusters 1138-262 AT z = 2.3ACS ON HST – 19 ORBITSHierarchical Galaxy Formation at Centre of Protocluster:  1138-262 AT z = 2.3 ACS ON HST – 19 ORBITS Hierarchical Galaxy Formation at Centre of Protocluster Blue: VLT Lyα Red: VLA Radio Miley et al. 2006 WHY STUDY DISTANT LUMINOUS RADIO GALAXIES - 2?:  WHY STUDY DISTANT LUMINOUS RADIO GALAXIES - 2? Probable probes of EoR for z andgt; 5 via redshifted HI Radio source physics Most luminous synchrotron sources Laboratories for high-energy physics Statistical Probes of Large-Scale Structure Luminosity functions Spatial clustering LOFAR will allow application of USS filter A SCIENCE DRIVER FOR LOFAR SURVEYSDetect z >5 radio galaxies :  A SCIENCE DRIVER FOR LOFAR SURVEYS Detect z andgt;5 radio galaxies Larger redshifts = steeper spectra LOFAR WILL DETECT STEEPEST SPECTRA (MOST DISTANT SOURCES) e.g. Blumenthal andamp; Miley 1988 WHY α ~ z CORRELATIONCONVENTIONAL EXPLANATION :  WHY α ~ z CORRELATION CONVENTIONAL EXPLANATION e.g. Radio spectrum Cygnus A Concave spectra + k-correction Larger redshifts andgt; steeper spectra e.g. Blumenthal andamp; Miley 1988 DOES THIS EXPLANATION WORK? OBSERVED RADIO SPECTRAARE NOT CONCAVE !!:  OBSERVED RADIO SPECTRA ARE NOT CONCAVE !! Spectrum of 4C 41.17 straight between andlt; 40 MHz! and 4.7 GHz (Chambers, Miley van Breugel, ApJ 363, 21, 1990) Not concave k-correction not explanation for USS spectrum of 4C41.17 SUMSS-NVSS SAMPLE (Klamer et al. 2006) 33/37 sources have flat spectra 0.8 – 18 GHz Not concave k-correction not (complete) explanation for USS spectrum 4C41.17, z = 3.8 WHY α ~ z CORRELATION: EXPLANATION 2 LUMINOSITY VS Z WITH MALMQUIST BIAS? Take 4C41.17, z = 3.8 Chambers, Miley van Breugel, ApJ 363, 21 (1990) :  WHY α ~ z CORRELATION: EXPLANATION 2 LUMINOSITY VS Z WITH MALMQUIST BIAS? Take 4C41.17, z = 3.8 Chambers, Miley van Breugel, ApJ 363, 21 (1990) Spectrum interpreted classic Kardashev 1962 Continuous particle injection for t inj Region 1 – no synch. losses Region 2 - t rad andgt; t inj - radiation losses = injection of new particles Region 3 – synchrotron and IC losses Low-frequency Break ν 1,2 ~ B-3trad-2 But B ~ (Luminosity) 2/7 α0 α1 = α0 – 1/2 α2 = 4/3 α0 - 1 Low Freq. cutoff ν 1,2 ~ 1/Luminosity MECHANISMS FOR SPECTRAL INDEX- z CORRELATIONS:  MECHANISMS FOR SPECTRAL INDEX- z CORRELATIONS Luminosity vs Magnetic field + Malmquist bias Chambers et al. 1988; Blundell andamp; Rawlings 1999, Nature, 399, 330 But Athreya and Kapahi Astrophys. Astron. 19, 63 (1998) showed α vs z corellation in sample at similar luminosities Spectral Index steepens with higher ambient density Athreya andamp; Kapahi: Upstream fluid velocity decreases in dense environment Steeper spectrum in 1st order Fermi acceleration process Klamer., PhD thesis, 2006, Univ. Sydney, 2006 Higher density steepens spectra AND increases luminosity Link with USS radio sources at centres of local rich clusters But ambient density highly non-uniform with large gradients Acceleration in nuclear regions – injected USS spectrum Internal spatial dispersion of spectral index relatively small Carilli et al. ApJ Suppl. 109, 1 (1997) How does left USS lobe know that right lobe is also USS? LOFAR AND PHYSICS OF DISTANT USS RADIO SOURCES:  LOFAR AND PHYSICS OF DISTANT USS RADIO SOURCES PHYSICS OF DISTANT USS SOURCES STILL UNKNOWN Accurate spectral studies needed to probe acceleration processes ACCURATE INTEGRATED FLUX DENSITIES AT 30 AND 15 MHz Accurate low-frequency spectra SPATIAL DISTRIBUTION OF LOW-FREQUENCY SPECTRAL INDICES Resolution andlt; ~ 4' needed 120 MHz - 100 km 60 MHz – 300 km 30 and 15 MHz – 1000 km LONG BASELINES ESSENTIAL LESSONS FOR FINDING DISTANT RADIO GALAXIES WITH LOFAR :  LESSONS FOR FINDING DISTANT RADIO GALAXIES WITH LOFAR 30 MHz may not be low enough frequency to separate z andgt; 5 radio galaxies from z andlt; 5 radio galaxies Deep 15 MHz survey highly desirable Strive to reduce confusion at ν andlt; 30 MHz Long baselines with good UV coverage essential 100 km ~ 50' PSR Confusion 4.7 mJy 400 km ~ 12' PSR Deeper by ~ 9 (0.6 mJy) 750 km ~ 7' PSR Deeper by ~ 20 (0.24 mJy) But effect of scattering, ionosphere, RFI Repeat several times Predictions difficult/impossible without plausible PHYSICAL modell 26 MHz ~ 28 Jy 4C 41.17 spectrum straight to andlt; 40MHz Rest frame ~ 200 MHz z = 6 corresponds to andlt; ~ 28 MHz observed frame LSS STUDIES FROM STATISTICS OF LOFAR USS SOURCES :  LSS STUDIES FROM STATISTICS OF LOFAR USS SOURCES 30, 15 MHz: New Parameter Space – USS Sources Spatial clustering and luminosity functions Filter USS sources Phase 1 (100 km): Confusion 1 mJy at 30 MHz, 5 mJy at 15 MHz Higher resolution highly desirable

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