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T.P.Krichbaum Max-Planck-Institut für Radioastronomie Bonn, Germany tkrichbaum@mpifr.de

Global Millimeter VLBI: Where do we stand ?. T.P.Krichbaum Max-Planck-Institut für Radioastronomie Bonn, Germany tkrichbaum@mpifr.de. people involved in Global Millimeter VLBI ( GMVA): MPIfR: W. Alef, U. Bach, A. Bertarini, T. Krichbaum, R. Porcas, J.A. Zensus, et al.

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T.P.Krichbaum Max-Planck-Institut für Radioastronomie Bonn, Germany tkrichbaum@mpifr.de

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  1. Global Millimeter VLBI: Where do we stand ? T.P.Krichbaum Max-Planck-Institut für Radioastronomie Bonn, Germany tkrichbaum@mpifr.de

  2. people involved in Global Millimeter VLBI (GMVA): MPIfR: W. Alef, U. Bach, A. Bertarini, T. Krichbaum, R. Porcas, J.A. Zensus, et al. IRAM: M. Bremer, A. Grosz, S. Sanchez, K. Schuster, et al. OSO: J. Conway, M. Lindqvist, I. Marti-Vidal, et al. OAN: P. Colomer, P. de Vicente, et al. INAF: S. Buttaccio, G. Tuccari, et al. NRAO: W. Brisken, C. Chandler, M. Claussen, V. Dhawan, C. Walker, et al. KVN: B.W. Sohn, T. Jung, S.S. Lee, et al. 1mm VLBI, EHT collaboration (in 2013) : APEX: R. Güsten, K. Menten, D. Muders, A. Roy, J. Wagner, et al. Haystack: S. Doeleman, V. Fish, R. Lu, M. Titus, R. Capallo, et al. CARMA: G. Bower, R. Plambeck, M. Wright, et al. JCMT: P. Friberg, R. Tilanus, et al. SMA: R. Blundell, J. Weintroub, K. Young, et al. SMTO: R. Freund, D. Marrone, P. Strittmatter, L. Ziurys et al. plus: A. Marscher's BU group since 2015: + BHC Team: C. Brinkerink, H. Falcke, R. Tilanus, et al.

  3. Image Credit: Astronomy/Roen Kelly The Origin of Jets: Understanding BH – Disk – Jet coupling - VLBI at mm- l overcomes opacity barrier - mm-VLBI and space-VLBI probe jet origin

  4. How are jets made – a sketch of present knowledge image: Rani@MPIfR, Marscher@BU this region can be probed by mm-VLBI and by variability studies (at high energies) • with mm-VLBI we can measure: • jet brightness temperature as function of BH separation for r < 1000RS • opacity and radial dependence of t=1 surface (core shift) • polarization / magnetic field vs. r • BH mass and spin, respectively set observational limits to these

  5. BP: BZ: Jet B-field Light cylinder BP versus BZ mechanism Blandford – Payne mechanism: centrifugal acceleration by magnetized accretion disk wind Blandford – Znajek mechanism: electromagnetic extraction of rotational energy from Kerr BH measure Jet speed f(r,z) Jet width f(z) TB f(z) → Shape of Nozzle Magnetic Field BH Spin etc. need to reach scale of a few RG

  6. M87 A 3mm VLBI survey of 127 AGN: Brightness temperature decreasing with increasing frequency ? Lee et al. 2008, 2015 86 GHz data Figure adopted from A. Marscher (1995) Brightness temperature increasing along jet; evidence for intrinsic acceleration ? mm-VLBI imaging of AGN can discriminate between fundamental models of jet formation VLBI with ALMA Lee et al. 2008 (AJ)

  7. 3C279 @ 230 GHz: 86 GHz (GMVA) APEX beam: 37 x 15 mas EHT @ 230 GHz SNR ~ 10-20 Apex-SMTO Apex-SMA SMA-SMTO compactness: 10-15 % !!

  8. VLB-Arrays observing at mm-wavelength • 43 GHz: VLBA(10), EVN (5), KaVa (7), HSA (12+) • 86 GHz: GMVA(15), VLBA(8), HSA(10) KVN(3) • 129 GHz: KVN(3), PV, PdB, SMTO, .... no joined activity yet • 230 GHz: PV, APEX, SMTO, SMA/JCMT, LMT, planned: ALMA, SPT, NOEMA, GLT, .... future: • 350 GHz: PV, PdB, SMTO, SMA/JCMT, APEX, ALMA, SPT, KP12m

  9. The Global Millimeter VLBI Array (GMVA) Imaging with ~45 mas resolution at 86 GHz GBT100m Yebes (OAN) Baseline Sensitivities in Europe: 30 – 250 mJy in US with GBT: 50 – 250 mJy best transatlantic: 30 – 100 mJy Array: 0.5 – 1 mJy / hr (assume 7s, 100 sec, 2 Gbps) http://www.mpifr-bonn.mpg.de/div/vlbi/globalmm • Europe: Effelsberg (100m), Pico Veleta (30m), Plateau de Bure (35m), Onsala (20m), Metsähovi (14m), Yebes (40m), KVN (3 x 21m), planned: SRT, NOEMA, ... • America: 8 x VLBA (25m), GBT (100m), planned: LMT, ALMA, ... Proposal deadlines: February 1st, August 1st

  10. 3mm VLBI sensitivity enhanced by inclusion of large European mm-telescopes: Effelsberg 100 m (MPIfR) Plateau de Bure, 6 x 15 m (IRAM, France) Yebes 40 m (OAN, Spain) Pico Veleta 30 m (IRAM, Spain) Baseline lengths (km): participating since 2011 fringe spacing: 0.4 – 1.8 mas, sensitivity > 15 - 50 mJy (7s, 2Gbps)

  11. Green Bank 100m telescope participates in GMVA 3mm VLBI observations 1st test observations in Feb. 2013 2 Gbps, 1 RDBE, PFB mode SEFD ~ 164 K app. eff ~ 0.26 (for s = 173 mm) RR LL POSSM plot after FRING: (solint 2min)

  12. 43 GHz VLBA 86 GHz GMVA Polarized sub-structure in jet of BLLac on 0.1 mas scales Jan. 15 Feb. 18 polarized jet emission on scales down to 50 mas

  13. 3mm VLBI Array Sensitivities assuming: 512 MHz bandwidth (2 Gbit/s), t=20 sec, 7sigma fringe detection, 2 bit sampling • Combining European mm-telescopes with the VLBA improves the angular resolution by factor ~ 2 and imaging sensitivity by a factor of ~2 - 3. • The addition of telescopes with large collecting area (GBT, LMT,SRT, ...) will give another factor of 2 - 3. • Participation of ALMA leads to mJy sensitivities and will improves the overall sensitivity by a factor of 5 over present day values. • Another factor of sqrt(rate/2Gbps) in sensitivity can be obtained via a further increase of the observing bandwidth.

  14. First Fringes between KVN and GMVA (86 GHz, May 2012) 3 x 21 m, baselines 305 – 478 km 0716+714 KVN – PdBI: SNR ~ 11 on 1 Jy source PB-KU 256 Mbps KY-KU RR LL

  15. 86 GHz VLBI Fringes VLBA to KVN GMVA Session May 2015 (PFB, now 1 Gbps) LCP 90 mas RCP KVN Yonsei – VLBA Brewster: B= 7860 km SNR ~ 22 on 0716+714 (Stot ~ 2 Jy) tint = 388 sec, 1 Gbps

  16. S. Koyama+ S. Koyama+ 2015

  17. Dec +20 Dec +50 KVN KVN VLBA VLBA Europe Europe KVN stations improve uv-coverage and resolution of GMVA long baselines with Europe at start long baselines with VLBA at end baseline sensitivities: KVN – GBT ~ 0.07 Jy KVN – IRAM ~ 0.15 Jy KVN – VLBA ~ 0.35 Jy (7 s, t=10 sec, 1024 Mbps)

  18. GMVA VLBA 15 GHz VLBA 43 GHz GMVA 86 GHz OJ 287: Spectral decomposition of core using GMVA beam: 0.22 x 0.043 mas Rcore < 0.04 mas (180 Rs9) TB ~ 2.4 E11 K The core is South! modelfit: 0.21 x 0.043 mas beam total spectrum from FGAMMA monitoring program VLBI component spectra from VLBI at 15 + 43 + 86 GHz, need to add 230 GHz

  19. GLT PdBure CARMA Pico Veleta SMTO LMT JCMT+SMA APEX/ALMA SPT The next step towards truly global 1.3 mm VLBI array (EHT) Status March 2013 with APEX added existing planned fringes established

  20. May 2009 beam (290 x 50) mas = (37 x 6) RS M87 at 86 and 230 GHz GMVA @ 86 GHz (11 stations) EHT @ 230 GHz: (4 stations) Modelfit + Clean Map uvtaper 0.3@6Gl Mar. 2013 Core jet structure traced down to ~25 mas scale small core size indicates BH spin a > 0 beam 59 x 24 mas = (7.4 x 3.9 RS)

  21. VLBI core size at 86 GHz, new VLBI core size at 230 GHz, new I M87's core size is smaller than previously thought new data point core size: 23 mas or 2.9 Rs This is smaller than the photon ring for an a=1 BH ! APEX baselines are more N-S oriented, than the E-W orientation of the US-array: the above numbers may measure the N-S jet width or sheath rather than the core !

  22. Competing Jet Models synchrotron self-absorbed conical jet plus relativistic shocks (Blandford-Königl jet) stratified (MHD) jet with moving hot spots/shocks or filamentary patterns 2 R0≥ 10 RS (a=0) Figure from Hada et al. 2011, Nat. last stable orbit radius: 1 → 6 Rs for BH spin a = 1 → 0 still unclear of what is seen at 1mm, need complementary imaging with GMVA

  23. EHT 230 GHz May 7, 2012 GMVA 86 GHz May 17, 2012 beam: 274 x 73 mas beam: 37 x 15 mas 230 GHz structure may trace edge-brightening in 3C279 Krichbaum+2013, Wagner+ 2015 0.6 pc core < ~1300 RS base of jet is transversely resolved and has a width of ~1 pc (~104 RS) size of individual components (emission regions) < 0.1 pc (1000 RS)

  24. 1 mas = 1.1pc Cygnus A: stacked VLBI image at 86 GHz (3 epochs, 2009 – 2010, 512 Mbps) 0.1 mas ↔ 0.11 pc ↔ 440 Rs9 core size: ≤ 46 mas or 200 Rs9 • jet transversely resolved on pc-scales • evidence for conical jet opening on jet side (at r < 1pc) • c-jet opening angle more narrow by factor 2 Boccardi et al. 2015

  25. Ridgeline at 86 GHz, Oct. 2009 (work in progress) Cyg A core ridgeline separation : ~ 0.1 mas (~ 400 Rs9) for jet & cjet evidence for conical opening both in jet and c-jet Boccardi et al., in prep

  26. Astrometry at mm-wavelength • Because of phase self-calibration in VLBI, the absolute position information is lost. • Due to rapid atmospheric phase-variations classical phase-referencing VLBI via position switch is limited to close source pairs. • With the phase-transfer method applied to 2 or more frequencies observed simultaneously, VLBI maps at different frequencies could be aligned. The positional accuracy of the alignment will be of order of a fraction of the beam (< 50 micro-arcseconds at 86 GHz). • An accurate image alignement is required for: • spectral index measurements of cores and jets • source kinematics at different frequencies (stratification) • measurement of opacity shifts in RA and DEC • determination of rotation measure

  27. Phase-referencing at 86 GHz is possible for close source pairs Phase vs. time 1308+326, 709 mJy hybrid map of calibrator 1308+328, 85 mJy phase-reference map of target distance: 14'.3 cycle: 10 – 20 s rate: 256 Mbps Porcas & Rioja, 2002 VLBA supports rapid enough switching

  28. VLBI frequency agility between 22-129 GHz (preliminary) note: consider hybrid phase transfer: some stations observe only at one frequency need to develop strategies how to tie in phases for these stations

  29. Summary and Outlook • the Origin of Jets in AGN can be studied at 7mm, 3mm and now also at 1mm • 3mm and 7mm VLBI is almost standard (< 2 Gbps), VLBI @ 1mm is non- standard (16 Gbps in 2015, aim at 32 Gbps) • participation of large collecting area dishes now provide much higher sensitivity (IRAM, GBT, Effelsberg, Yebes, soon: LMT, ALMA, ...) • VLBA provides important uv-coverage and frequency agility (43/86 GHz) • calibration limitations due to weather are over-come with an increased antenna number, which facilitates the use of closure amplitudes (N > 12) • advanced methods in global-fringe fitting could be implemented to further optimize the array sensitivity (incoherent averaging, etc.) • a further increase of the observing bandwidth beyond 2 Gbps at 3mm/7mm is highly desirable (ALMA: 32 Gbps) • dual/multi frequency phase transfer capabilities are not yet in place • a denser time sampling is necessary to better trace rapidly evolving sources • 1.3 mm-VLBI (EHT) is limited and requires complementary global 7 & 3 mm VLBI (better uv-coverage, sensitivity, beam size within a factor of 2)

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