1. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Astronomy Location of Virgo A (M87) Nature of M87 Expected signal strength & spectrum Measurement Choice of observing frequency Antenna type Receiver system Interferometer Transit scans Results Conclusions & comments

2. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Nearest star is 4.3 ly away 4.5 x 10 9 km = 0.0005 ly Give some idea of scale In astronomical terms the solar system is very small ASTRONOMY

3. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk SUN Local Spur Solar system located toward edge of Milky Way In a local spur of a spiral arm Plan View of Milky Way

4. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Table 6.1: Local Group of Galaxies Milky Way 432,000 ly Fornax Milky Way is in a small group of galaxies Approximately 400,000 ly in size (1 parsec = 3.2 ly)

5. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk 5m Ly Members of the Local Group of galaxies 10M ly diameter To Virgo Cluster

6. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Local Group Virgo Cluster M66 Group Leo 1 Ursa Major Group M101 Group M81 Group Draco Group 40M ly 53M ly 35M ly 38M ly 11M ly 55M ly 24M ly M51 Group 31M ly The bigger picture – Virgo A (M87) is 53M ly away

7. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk 3D map of Super Cluster 160M ly The bigger picture in 3D

8. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk 13hr 12:45hr 12:30hr 12:15hr 12hr Right Ascension +20 0 +15 0 +10 0 +5 0 Declination 1010 M87 Transit scan of Virgo Cluster 15 0 Interferometer main beam 3dB BW ~1 0 x 30 0

9. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk VCC0763, (M87), Virgo A signal strength Other galaxies in the group M87 dominates the radio emission from the Virgo cluster of galaxies

10. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk 110,00Ly 100,000ly Diameter of Milky Way 100,000 ly 330,000 ly M87 is >3x diameter of Milky Way Giant Elliptical Galaxy Barred Spiral Galaxy M87 is more than 3x the size of the Milky Way Virgo A is one of the most remarkable objects in the sky It has an active galactic nucleus (AGN) and a strange jet RA = 12 : 30.8 (h:m) DEC = +12 : 24 (deg:m) Distance ~ 53M ly Visual Brightness = 8.6 (mag) Visual extent of core = 8 arc minutes

11. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk 5,000 ly Neptune is 0.0005 ly away M87 The galaxy is one of the most massive in the local Universe 200x mass of Milky Way The jet produces the bulk of the radio emission Consists of relativistic plasma ejected from the AGN Jet on the other side of the galaxy is obscured The AGN is probably a super massive black hole

12. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk At the core of this galaxy is a super massive Black Hole (SMBH) with an estimated mass of (6.6 ± 0.4)×10 9 Solar masses and a diameter larger than the orbit of Pluto Accretion disc rotating at velocities of up to 1,000 km/s (0.2 ly radius) Black hole in M87 may be displaced from the galaxy centre by a distance of about 82 ly. Physics of jet formation is not fully understood Rotation of black hole magnetic field produces particle accelerating E fields Radio emission is by Synchrotron process

13. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Synchrotron emission Relativistic particles confined by magnetic field lines High intensity highly beamed polarized emission magnetic field charged particle v r circular polarization linear polarization Radio beam Signal strength falls with frequency – 100MHz – 1GHz best But antenna gains low at low frequencies (small antennas) Best frequency for detection is complex issue Spectral index x  0.79 S = k f - x EMMISION MECHANISM

14. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Signal strength plotted against wavelength shows increase with longer wavelength Virgo A is a weak source compared with Cassiopeia and Cygnus A Expected signal strength at 408MHz is 560Jy 1Jy = 10 -26 W/m 2 /Hz Hercules Virgo Cygnus Cassiopeia 1cm 10cm 1m 10m Wavelength 10 10 2 10 3 10 4 Power flux density (10 -26 W m -2 Hz -1 ) P x ( =wavelength, x=spectral index)

15. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Virgo A is one of the weakest sources It is 53M ly away It emits ~ 10 33 Watts (<1GHz) Note – big gap to pulsars 1 10 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9 Power Density Jy (10 -26 W m -2 Hz -1 ) Solar storms & plages Quiet sun Solar bursts Sun Taurus A Virgo A Pulsars Jupiter Cassiopeia A Cygnus A Radio Source Orion Nebula Signal strength (log scale) Signal strengths of astronomical radio sources

16. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Choice of frequency & antenna type On balance observation at <1GHz is best for (x)=0.79 For interferometer we need two antennas Could use two dishes at around 1420 MHz but away from H line Did not have two suitable (3m) dishes Opted for easy to build low cost Yagis at 408MHz Chose SARA 408MHz Quagi design (Hal Braschwitz and Jim Carroll ) Predicted beam pattern Z =45.51 +j 3.36 ohms. EQUIPMENT Single 3m dish

17. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Single SARA Quagi Beam Pattern -3dB BW = 33 0, SL @ -19dB Twin SARA Quagis stacked 1.2m apart Compromise on BW & SL Levels -3dBW = 17 0, SL at -14dB Stacked Quagis at 408MHz

18. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Antenna head amplifier Antenna Preamps RAS 408MHz ( WD5AGO 0.33dB NF) Mini circuits ZX60-33LN (50-3000MHz,1dB NF) 44dB combined Gain 406.2MHz 411.8MHz

19. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Receiving system and Temp control Preamps and receiver were temperature controlled ICOM IC-R7000 Receiver Temperature control Unit Today, I would use an SDR like the FunCUBE dongle

20. Weak Signal Detection of Virgo A EME Conference 2012 Transit scan across Galactic Plane using ‘FunCube Dongle’ SDR Signal Level dB (0.1dB/div) ~ 2 hours Centre of galactic plane 1.2dB Signal Level dB (0.1dB/div) FCD 1420.4MHz Signal strength recording Time Start End Signal Level dB (0.1dB/div) ~ 2 hours Centre of galactic plane 1.2dB An SDR Radio Telescope www. britastro/org/radio 18/8/2012

21. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Simple Interferometer configuration Interferometer can distinguish between diffuse background and ‘point sources’ Total power receiver gives ‘smeared’ response due to larger beamwidth INTERFEROMETER

22. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk The two twin Quagi antennas were mounted >2 above the ground on towers separated by 30m Fringe period = 5.6 minutes 30m West arm East arm

23. Weak Signal Detection of Virgo A EME Conference 2012 Crab Nebula used as point source to examine beam pattern Taurus A is ~ 3 x power of Virgo A (~1200Jy at 408MHz) Half power beam width of Main Lobe ~ 0.6 0

24. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012 www.dmradas.co.uk 13hr 12:45hr 12:30hr 12:15hr 12hr Right Ascension +20 0 +15 0 +10 0 +5 0 Declination 1010 M87 15 0 Interferometer beam Signal Strength Beam profile calibrated from Taurus A measurement

25. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012 Navigating the sky (setting up transit observations) Use ‘Radio Eyes’ software All sky radio map @ 408MHz Find location of Virgo A and set beam position for transit Ensure high beam elevation (avoid ground noise) Measure signal level for 5 hours either side of transit Virgo A Main beam Declination 0 Right Ascension hrs Radio Eyes 408MHZ All Sky map 50 0 Elevation Horizon Virgo A www.dmradas.co.uk Beam moves this way

26. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Measurement results Transit scans performed on 11 th /12th & 12 th /13 th Feb. 2008 Stable results from both days added to improve S/N 30m baseline interferometer at 406.5MHz (0.6 0 HP BW) Plot shows signal scan across source Virgo A Diffuse galactic background emission is ‘resolved’ so shows no fringes Virgo a ‘point source’ (~10’ dia) - is not resolved and produces fringes Can separate out ‘total power’ plot and fringes Resultant plot is the Virgo A fringe pattern MEASUREMENTS

27. Weak Signal Detection of Virgo A EME Conference 2012 One day Transit Scan through Taurus A and Virgo A Signal Amplitude (lin) Declination Right Ascension (hrs) 20 0 10 0 30 0 0 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 Taurus A Outer Galactic Plane Inner Galactic Plane Virgo A Continuous Signal record over 17 hours Virgo A Taurus A Beam track 18/8/2012

28. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Raw data shows both ‘total power’ and fringes from Virgo A Remove total power to leave fringe pattern Full data record (blue) Average signal (yellow) Increase in signal due to Virgo A Expected transit Represents a signal level of ~560Jy, 5.6x10 -24 W/m 2 /Hz

29. Weak Signal Detection of Virgo A EME Conference 2012 18/8/2012www.dmradas.co.uk Summary & Conclusions A low cost, simple interferometer can be used to detect the extragalactic radio source Virgo A (M87) Stacked SARA Quagi antennas have sufficient gain at 408MHz With modest temperature control of amplifiers & receiver, records from different days can be added to improve S/N Virgo A signal strength of ~560Jy is near limit for detection by simple system Improvements can be made by: Stacking more Quagis Using a stable SDR receiver Phase Switched interferometer I need time to do it ! MAPS-010143 part

30. Weak Signal Detection of Virgo A EME Conference 2012 The EME Community & Radio Astronomy Has excellent receivers & antennas Could work around 408MHz and 1400MHz Probably enough sensitivity May need gain & noise stabilization Could easily undertake some Radio Astronomy Think about it ? Why not try ? DL7APV WD5AGO DL3OH

31. Weak Signal Detection of Virgo A EME Conference 2012 M87 Virgo A RA = 12 : 30.8 (h:m) DEC = +12 : 24 (deg:m) Distance ~ 53M ly