Very Long Baseline Interferometry For Astronomy

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1 Very Long Baseline Interferometry For Astronomy Michael Bietenholz With slides from Adam Deller (Astron) and Shep Doeleman (Haystack) Ylva Pihlström (UNM) Craig Walker (NRAO) and Bob Cambpell (JIVE)

2 What is VLBI? Supernova Very Long Baseline Interferometry Correlate

3 Optical Sky

4 Radio Sky 408 MHz Jodrell, MPIfR, Parkes

5 What Sources can be observed with VLBI? Any sufficiently compact radio source can be studied with VLBI AGN Masers Supernova and (distant) supernova remnants Stars (some) Pulsars...

HartRAO 26m at 13cm, resolution of 20 arcmin VLA radio continuum observations of the inner lobes a field of

6 Resolution: Centaurus A Galaxy in the optical with radio (VLA overlay) The full radio emission covers nearly 10 degrees on the sky. HartRAO 26m at 13cm, resolution of 20 arcmin VLA radio continuum observations of the inner lobes a field of view 11 arcmin, resolution ~20 arcsec VLBI (LBA + HartRAO) image show fine details of jet near the black hole (centre). Field of view is jet ~0.08 arcsec, resolution is ~0.003 arcsec (milliarcsec)

7 2' ~ 10 kpc M87 structure on a very wide range of scales! Powered by relativistic jets from supermassive black hole (10 6 to 10 9 M ʘ ) in the centers of galaxies 0.01 pc Image: F. Owen, J. Biretta et al

8 What kinds of science use VLBI? Black Hole / Jet Model Inner 2 pc of M87 AGN jet (C. Walker et al.)

9 Measurening the Magnetic Field Around a Suppermassive Black Hole Baczko et al 2016 Galaxy NGC 1052 mm-wavelength VLBI. 86 GHz observations, 15 stations observations in 2016 best identification yet of black hole position outside our own galaxy compactness and brightness of central region magnetic field is 0.02 to 8.3 Tesla (Earth: Tesla)

10 What kinds of science use VLBI? NGC 4258 Direct distance : 7.5±0.3 Mpc and Mass of black hole 39 x 10 6 M ʘ Herrnstein, Greenhill et al

11 The Big Bird Neutrino A neutrino with energy of 2 peta-electron Volts detected by the Ice Cube Neutrino observatory =3200 erg (1 gm at 80 cm s -1!! where is it from?? Image: Jakob van Santen/IceCube

12 The Source of High-Energy Neutrinos? Gamma-ray Burest Fermi LAT images showing the gamma-ray sky around the blazar PKS B B NASA/DOE/LAT-collaboration.

VLBI Images of the Blazar PKS B1424-418 VLBI radio images from the TANAMI project reveal the 2012-2013 eruption of PKS B1424-418 at a wavelength of 8.4 GHz.

13 VLBI Images of the Blazar PKS B VLBI radio images from the TANAMI project reveal the eruption of PKS B at a wavelength of 8.4 GHz. The core of the blazar s jet brightened by four times, producing the most dramatic blazar outburst PKS B seems a likely source for Big Bird (although there is a 5% chance its a coincidence) Image & Caption Credit: TANAMI

14 Radio Supernovae in M82 Over 50 compact sources discovered in M82, most are supernovae/supernova remnants Garrett, Pedlar, Beswick et al

15 Image rms ~ 6 μjy/beam! VLBI images of supernovae in the nuclei of the galaxy Arp 220 (Lonsdale et al. 2007)

16 What kinds of science use VLBI? TX Cam (pulsating star) SiO maser ring showing outflow from star's surface. The first-ever time-lapse "movie" showing details of gas motions around a star other than our Sun. The study, the largest observational project yet undertaken using Very Long Baseline Interferometry, P. Diamond et al.

17 Velocity (km/s) Motion (and velocity) of water maser spots in protostellar object Cepheus A HW 2 (Gallimore et al. 2014). Expanding rings of masers driven by outflow from the from the star.

18 What kinds of science use VLBI? A. Mioduszewksi et al. Micro-quasar: Galactic object, black-hole mass of a few solar masses, behaves similarly to AGN, but much shorter timescales. SS433 is the first one discovered

19 Gamma-Ray Bursts Bursts of Gamma-rays, ~1 per day duration <1 seconds to hours! Cosmological distances very high luminosity Afterglows discovered Long Duration GRB s are associated with Type Ibc supernovae Collapse of massive star into a black hole powers highly relativistic jet GRB s are jets oriented near the line of sight The jets not near the line of sight may be visible in radio Image: Saxton

Relativistic Expansion: GRB 030329 (SN 2003dh) 22 Apr 2003 Size ~1 pc = 3 light years VLBI expansion measurements: by Taylor et al.

20 Relativistic Expansion: GRB (SN 2003dh) 22 Apr 2003 Size ~1 pc = 3 light years VLBI expansion measurements: by Taylor et al. & Pihlstrom et al. show clear deceleration, with transition to non-relativistic regime at t ~ 1 yr Taylor et al, 2004, 2005; Pihlstrom et al. 2007

Relativistic Expansion: GRB 030329 (SN 2003dh) 22 Apr 2003 Size ~1 pc = 3 light years Speed of light VLBI Expansion Measurements: by Taylor et al.

21 Relativistic Expansion: GRB (SN 2003dh) 22 Apr 2003 Size ~1 pc = 3 light years Speed of light VLBI Expansion Measurements: by Taylor et al. & Pihlstrom et al. show clear deceleration, with transition to non-relativistic regime at t ~ 1 yr Taylor et al, 2004, 2005; Pihlstrom et al. 2007

22 VLBI Movie of SN 1993J Global Array VLBI at 8.4 GHz and 5 GHz for last few epochs 33 Epochs of VLBI from 1993 to present (and continuing!)

23 Astrometry: Parallax to reference, e.g. QSO target object Can measure direct, geometrical distances out to ~few kpc

Proper Motion of pulsar B0950+08 Pluto on same angular scale (Hubble Space Telescope) NASA, ESA, and M.

24 Proper Motion of pulsar B Pluto on same angular scale (Hubble Space Telescope) NASA, ESA, and M. Buie (Southwest Research Institute) milli-arcsec level pulsar parallax measurement (W. Brisken et al.)

25 Distance Measurements to Pleiades Hipparcos satellite to measure parallaxes got a somewhat discrepant distance to Pleiades. Carl Melis (UC, San Diego) undertook a campaign of precise radio astrometry on several Pleiades stars to determine parallax Measured parallax wit respect to a background quasar over 18 months Stars are weak radio sources so a sensitive network was needed, wich included the VLBA, GBT, Arecibo and Effelsberg. Settled distance controversy

26 Astrometry highlights >100 parallax distances to masers around high-mass star forming regions: Spiral arm structure Distance to Galactic Center Galactic rotation curve Wu et al 2014

27 Motions OF Sagittarius A* (SgrA*) Measures rotation of the Milky Way Galaxy / yr Reid et al. 1999, Ap. J. 524, 816 Sgr A* is the massive black (~4 million solar masses) hole in the center of our own galaxy (the Milky Way)

28 The Shadow of the Black Hole in SGR A* People are working to try and resolve the black hole in our own Galaxy with sub-mm-wave observations. These are simulations of what we might see by Moscibrodzka et al: emission in an accretion flow around a rapidly spinning black hole in Sgr A* blurred according to the expected interstellar scattering. This is compared to a reconstructed image from simulated submm-vlbi for face-on and edge-on orientations of the accretion flow

29 Tests of General Relativity I Jupiter passed very near (3.7' on the sky) to quasar J in 2002) General Relativity predicted a deflection of ~1.2 mas Fomalont & Kopeikin: measured a deflection that predicted by General Relativity speed of gravity = speed of light (maybe) θ deflection 1.2 mas Edward Fomalont & Sergei Kopeikin

thermonuclear reaction happens VLBIA images made with European VLBI Network (EVN) images at age 91 days (contour

30 VLBI observations of a Nova in Outburst VLBI image of Nova V959 Mon. Nova is a binary system, where a companion star dumps matter onto the surface of a white dwarf untill a runaway thermonuclear reaction happens VLBIA images made with European VLBI Network (EVN) images at age 91 days (contour lines) and 113 days (in colour) after the γ-ray which signaled the nova explosion. These images show the compact radio knots expanding diagonally. Chomiuk et al, 2014

31 A Movie Star Star Movie 35 sessions 8.4 GHz VLBI observations of the radio-emitting star IM Pegasi over 8 years (made in support of Gravity-Probe B) circle indicates the position of the disk of the star (radius ~13 R sun ) See Bietenholz et al, 2012,, Astrophys. Journal. Supp., v 201, p 7.

32 VLBI Astrometry The International Celestial Reference Frame (ICRF) Currently ICRF-2, based on coordinates of 3414 extragalactic sources (AGN s), including 295 defining sources. ICRF-3 currently being built by a working group of the IAU.

33 Geodesy and Astrometry Fundamental reference frames International Celestial Reference Frame (ICRF) International Terrestrial Reference Frame (ITRF) Earth rotation and orientation relative to inertial reference frame of distant quasars Tectonic plate motions measured directly Earth orientation data used in studies of Earth s core and Earth/atmosphere interaction Germany to Massachusetts 10 cm Baseline Length Baseline transverse GSFC Jan cm

34 Image: Roskosmos Space VLBI: RadioAstron

35 Space VLBI: RadioAstron Radio-Astron: space VLBI satellite resolutions of ~10 of micro-arcsec at 22 GHz Worldwide network of ground stations including HartRAO

36 RadioAstron Results Yuri Kovalev

37 RadioAstron Compact Jets Ground-based VLBI image of M87 Jet (Walker et al) A. Lobanov

38 Mapping Structure on mas scales A. Lobanov

39 Thirteenth Synthesis Imaging Workshop 40

Radio Interferometry and VLBI. Aletha de Witt AVN Training 2016

Radio Interferometry and VLBI. Aletha de Witt AVN Training 2016 Radio Interferometry and VLBI Aletha de Witt AVN Training 2016 Radio Interferometry Single element radio telescopes have limited spatial resolution θ = 1.22 λ/d ~ λ/d Resolution of the GBT 100m telescope