Overview of (sub)mm-VLBI

Shep Doeleman

MIT Haystack Observatory

A (sub)mm-VLBI Workshop• Important: Broad interest in key science drivers.• Timely:

– Technical Advances: sensitivity and baseline coverage has reached ‘tipping point’.

– New submm facilities coming online will significantly improve current array.

– Window for (sub)mm-VLBI may not be open indefinitely.

• Planning Required:– Complex observations must become more turn-key (calibration protocols, permanent VLBI inst., test protocols, …)

– Development and deployment of new instrumentation.

– Array-wide scheduling (and pan-chromatic).

– Development of new sites (still hard, requires collective effort).

Workshop Anatomy• Presentations

– new instrumentation to be deployed at most sites.– development of next-generation instrumentation.– sites under development and new sites.– techniques and protocols for observations.

• Discussion– address issues necessary for outline of coherent technical roadmap.– address scheduling issues (frequency, dates, no-jeopardy proposing?)– Assess individual site needs for near-term observations.

A Brief History of (sub)mm-VLBI

• 20th anniversary of 1st 1.3mm VLBI fringes! (112Mb/s)

Happy Anniversary

A Brief History of (sub)mm-VLBI• 20th anniversary of 1st 1.3mm VLBI fringes! (112Mb/s)

• 1994/5 - 215GHz VLBI between IRAM30m - PdeBure(1)

• 1999 - failed attempt at 230GHz on ARO/SMT-KittPeak

• 2001 - 147GHz VLBI on IRAM30m - Metsahovi

• 2002 - 129/147GHz VLBI on IRAM30m, ARO/SMT, KittPeak, Metsahovi (224Mb/s on TAPE).

• 2003 - 230GHz VLBI on IRAM30m, PdeBure, ARO/SMT, KittPeak (512/1024Mb/s on DISK)

• 2006 - failed attempt at 230GHz on CSO-ARO/SMT

• 2007 - 230GHz VLBI on CARMA(1), ARO/SMT, JCMT/SMA, IRAM30m (4Gb/s)

• 2009 - 230GHz VLBI on CARMA(2), ARO/SMT, JCMT/SMA (4Gb/s)

SgrA*: Best Case for a SMBH• Stellar orbits approaching within 45 AU. • Proper motions < 1km/s: M>10^5 Msol

(Backer & Sramek 1999, Reid & Brunthaler 2004)

• Short time scale X-ray flares (300 sec rise).• IF flares with

modulation (a>0).

VLT: Genzel et al 2003Baganoff et al 2001

Ghez et al 2005

1.3mm Observations of SgrA*

4630km

4030km

908km

Builds on long history of SgrA* VLBI and mmVLBI.

Resolving Rsch-scale structures

Gammie et al

14 R

sch

(

as)

ARO/SMT-CARMA

ARO/SMT-JCMT

JCMT-CARMA

The minimum apparent size.Broderick & Loeb

Noble & Gammie

Event Horizon

Ra =3 3 Rsch 2( ) R≤.5Rsch

R / −Rsch / R R>.5Rsch

⎧⎨⎪

⎩⎪

Alternatives to a MBH

Most condensations of smaller mass objects evaporate on short timescales.Current obs imply Tevap~500 yrs.

Boson Star is a remaining ‘exotic’ possibility where R=Rsch + epsilon.Depends on Boson mass.

A Surface or Event Horizon• Does SgrA* have a surface?

• A quiescent surface would radiate.

• The radius R and dM/dt set the expected NIR flux.

• NIR limits set dM/dt limits.

• These are too low to power SgrA*.

• If no surface then Event Horizon.

Broderick & Narayan 2006

Model Correlated Flux DensityQuiescent disk Models: Radiatively InefficientAccretion Flow (RIAF)

Courtesy Gammie et aland Broderick&Loeb

April 2009 SgrA* Observations

CARMA - Hawaii

Time Variable Structures

• Variabilty in NIR, x-ray, submm, radio.

• Probe of metrics near BH, and of BH spin.

• Violates Earth Rotation aperture synthesis.

• Use ‘good’ closure observables to probe structure as function of time.

Hot Spot Model for SgrA* Flares

QuickTime™ and aFLIC Animation decompressorare needed to see this picture.

Observing Black Hole Orbits with Closure Phase

Doeleman et al 2009

Polarization Signatures at the Event Horizon

Fish et al 2009

Beam: 0.43x0.21 mas 0.2mas = 0.016pc = 60Rs 1mas/yr = 0.25c

VLBA Movie of M87 @ 43 GHz (7 mm)Craig Walker et al. 2008

More luminous class of AGN with 2000x more massive central BH, and core detected in TeV with FERMI.

April 2009 M87 1.3mm VLBI Detections

CARMA1-CARMA2

CARMA-ARO/SMT

JCMT-CARMA

JCMT-ARO/SMT

Resolved componentis > 300as

Compact componentis 35as FWHM, or~ 4.5 Rsch.

Apparent size of ISCOis 7.35 Rsch and

Apparent size of EH is 5.2 Rsch.

Jet genesis, TeV emission.

Comparison with Jet Models

a=0.998, =25deg

Broderick & Loeb (2009)

Making Progress• Big Questions

• Is there an Event Horizon?• Does GR hold near BH?• How are jets launched?• How does matter accrete/outflow near a BH?

• Essential Requirements

• Baseline coverage: Develop new sites• Sensitivity:

• new receivers (dual pol)• phased arrays• wideband recording

Event Horizon Telescope

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

Adding ALMA

Adding Telescopes

Adding LMTHawaii, CARMA, SMT

Progression to an Image

GR Model 7 Stations 13 Stations

New Site Timeline to 2011• ASTE + APEX tests at 230GHz in Spring 2010 (4Gb/s).

• Full array observations in 2011 (8Gb/s + 16Gb/s Burst): • ARO/SMT• Phased Mauna Kea (CSO + JCMT + SMA)• Phased CARMA• IRAM 30m• APEX/ASTE• LMT

• 2011 VLBI contemporaneous with XMM observations.

• 345GHz tests in 2011.

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

Phasing ALMA for VLBI

230/345GHz Rx with ALMA Mixers• Use ALMA development to build sideband separating, dual pol, high sensitivity receivers (ALMA bands 6,7).

• Developing project with UMass to replace 230GHz Rx at JCMT using ALMA mixer/preamps:

• Tsys improves by x2.5• BW improves by x4• Dual pol• Target installation date: Winter 2011

Wide(er)band VLBI Systems• Currently at 4Gb/s• Continuous 8Gb/s by mid-2010• Burst Mode: using parallel DBE’s and data buffering

in RAM to reach 16Gb/s for 60 sec bursts. • Correlation on software platforms.

New Frequency Standards

• Sapphire Oscillator:

– Factor of 10-100 times more stable than Hmaser (T~1-100sec).

– Plan to have CSO at Haystack by Spring 2010 in collaboration with UWA.

• Modified Masers:

– Use of best Quartz crystals in H masers to reduce phase noise.

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 new dishes, array operations for 5 years.

• 2019 -- 2024

Status of Collaboration• 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: DBE + CARMA phasing

More Science• Masers:

• SiO (J=2-1, J=3-2, J=4-5)• HCN (177GHz)• Water• Methanol

• Jet Physics• Sensitivity: ALMA(50) - ARO/SMT at 4GHz (16Gb/s)

• 35mJy at 230GHz = 7sigma in 10 seconds.• Many more sources

Summary• 1.3mm VLBI confirms Event Horizon scale

structure in SgrA* and M87• Imaging the Event Horizon and observing BH

orbits are within reach in <5 years.• Higher sensitivity enabling broader science case.• Science/Technical advances: rapid change.

• detections, tech. validation, team, sites.• Assembling strong international collaboration.• Competitive with (and complementary to) much

larger space-based mission (e.g., IXO).• Touches on almost all aspects of

radio/mm/submm communities. • All the ingredients for the EHT exist.

mm/submm VLBI CollaborationMIT Haystack: Alan Rogers, Vincent Fish, entire staff.U. Arizona Steward Obs: Lucy Ziurys, Robert Freund CARMA: Dick Plambeck, David Woody, Geoff BowerHarvard Smithsonian CfA: Jonathan Weintroub, Jim MoranJames Clerk Maxwell Telescope: Remo Tilanus, Per FribergUC Berkeley SSL: Dan WerthimerCaltech Submillimeter Observatory: Richard ChamberlinMPIfR: Thomas Krichbaum, Alan RoyASIAA: Paul Ho, Makoto InoueNAOJ: Mareki HonmaIRAM: Michael BremerNRAO: John Webber, Ray Escoffier, Rich LacasseUMass: Neal Erickson, Gopal Narayanan

History: Backer, Lo, Rogers, Krichbaum, Jauncy, Marcaide, Shen, Bower.