(sub)mm-VLBI: Creating an Event Horizon Telescope

1. (sub)mm-VLBI:Creating an Event Horizon Telescope Shep Doeleman MIT Haystack Observatory

2. An international collaborative project assemble a global submm-VLBI array for observing and resolving Event Horizons. • Key observations have removed scientific uncertainty (i.e. will we see anything?). • Technical Elements: low risk extensions of ongoing efforts and leverage investments from ALMA and other development projects. • Collaboration: necessarily a international project but with well defined boundaries. • Strong element of training at intersection of submm science and interferometry. The Event Horizon Telescope

3. Adding Telescopes: uv coverage, flare coverage, closure quantities for real-time modeling. • ALMA quality, dual pol rx and LO for all sites. • Testing hardware for in-situ verification. • Central correlation facility. • VLBI backends/recorders at rates up to 64Gb/s • Phased Array processors (ALMA, PdeBure, CARMA, Hawaii) • Low noise freq. references. • Logistics/Observations/Project Management Technical Elements of EHT

4. Event Horizon Telescope Phase 1: 7 Telescopes Phase 2: 10 Telescopes Phase 3: 13 Telescopes

5. Progression to an Image GR Model 7 Stations 13 Stations

6. Hawaii Phased Array Success(CSO+JCMT+SMA)-CARMA

7. Phasing ALMA for VLBI

8. Proposal submitted to NSF ATI program for 230GHz Rx development using ALMA band 6 mixer/preamps. • To be installed at JCMT (Fall 2011): • Tsys improves by x2.5 • BW improves by x4 • Dual pol • UMass to build dewar, Haystack VLBI testing, JCMT assistance with install and commissioning. 230GHz Rx with ALMA Mixers

9. Other Development Burst Mode: Not possible using Mark5c architecture. Now examining COTS solution. Sapphire Oscillator: Will work on slaving excellent crystal to CSO and to GPS (on long time scales). Hopefully will have CSO at Haystack by Spring 2010. Modified Masers: Discussions with Symmetricom on installing excellent crystal (oscilloquartz 8607) in their maser. Difficulty: increasing hydrogen flux to boost stability.

10. EHT Phases: Phase I: 7 station 8Gb/s array ALMA phasing, preliminary Rx/LO work, new frequency standards, new site studies, operations. 2010 -- 2014 Phase II: 10 station 32Gb/s dual-pol array Activate SEST, equip S.Pole, new frequency standards, install new 0.8/1.3mm dual-pol Rx, increase bandwidth of VLBI backends/recorders, relocate ATF dishes, operations. 2015 -- 2018 Phase III: 12 station array up to 64Gb/s install ATF dishes, array operations for 5 years. 2019 -- 2024

11. EHT: A Phased Approach • No ‘first-light’: we are ‘lit’ from the very beginning, so no waiting/uncertainty. • Each year, new capability will expand science results. • Impact of technical work on science can be assessed each year: transparency of progress. • Allows project to flexibly adapt to new science results: crystal ball very clear for Phase I (and will be for Phase II with results from Phase I). • Leverages existing facilities - no need for initial build up.

12. Haystack: • Recorder and Digital Backend • Frequency Standards • ALMA Phasing • Organization of observations • Harvard-CfA: • Phased Array development • SMA support • ALMA Phasing • U. Arizona/ARO: • SMTO support • Test observations • CARMA: • Phased Array work • Site support • ASIAA: H-maser cost-share • JCMT/CSO: Telescope support. • NAOJ: ASTE support • MPIfR-Bonn • Plateau de Bure/IRAM 30m • APEX support • IRAM: • IRAM site support • Plateau de Bure phasing • NRAO: • ALMA Phasing • RDBE + Mark5c • UC Berkeley: Digital Backend Status of Collaboration and WB

13. 1.3mm VLBI confirms Event Horizon scale structure SgrA* • Imaging the Event Horizon and observing BH orbits are within reach in ~10 years. • Science/Technical advances: rapid change. • SgrA* detection, tech. validation, team, sites. • Assembling strong international collaboration. • Competitive with (and complementary to) much larger space-based mission (e.g., IXO). • All the ingredients for the EHT exist. Summary