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

Shep Doeleman

MIT Haystack Observatory

The Event Horizon Telescope

• 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.

Technical Elements of EHT• 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

Event Horizon Telescope

Phase 1: 7 Telescopes Phase 2: 10 TelescopesPhase 3: 13 Telescopes

Progression to an Image

GR Model 7 Stations 13 Stations

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

Phasing ALMA for VLBI

230GHz Rx with ALMA Mixers• 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.

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.

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

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.

Status of Collaboration and WB• 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

Summary• 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.