Arecibo’s Existing VLBI CapabilityArecibo’s Existing VLBI Capability

DAR - VLBA4

MK5A

Max 1-GHz IF

The Big Dish(Gain~10k/Jy,SEFD~3-5 Jy)

Correlator

Internet

FedEx

Receivers Max. IF bandwidth/Rx

# of BBCs & Max ∆ν/BBC

Total single-pol RF Bandwidth

Total data rate

327, L, S,S-High, C, C-High, X

.05, .5 (#1,2 Rxs), 1 GHz

2 x 8, 16 MHz 256 MHz (max) 1024 Mbps

Co-Observing Networks:

1.VLBA + Ar & the HSA (HSA, includes the phased-VLA,

GBT, EF)2. European VLBI Network + Ar 3. Global - Network4. eVLBI (Real-time VLBI via

internet as yet with EVN only)

• A continuum observation, =18-cm, data-rate=512 Mbps, i.e. 128 MHz of RF bandwidth, dual-polarization, = 120 minutes on source:

Arecibo’s Contribution to the ArraysArecibo’s Contribution to the Arrays

• A spectral-line observation, =18-cm, 64 channels over 1-MHz, 2 pol, 120 min.

0.25 mJy/beam/ch 0.62 3.00.310.9 mJy/beam/ch

VLBA+Y27+Gb+ARVLBA+Y27+GBVLBAEVN+AREVN

HSA (VLBA+Y27+EF+GB+Ar) -Ar

1σ Image noise = 3.3 μJy/beam 7.1 μJy/beam

EVN+Ar-Ar

1σ Image noise = 3.8 μJy/beam 9 μJy/beam

Global (EVN+VLBA+Y27+Gb)+Ar-Ar

1σ Image noise = 2.5 μJy/beam 4.7 μJy/beam

eVLBI : Test run at 512-Mbit/sec First trans-Atlantic eVLBI fringes at a data rate of 512 Mbits/sec on 9

September 2008.

Data arriving at JIVE

Arecibo Fringes with EVN Telescopes

PRISANET (PR) of the Arecibo Obs./UPR.

AMPATH (US) of Florida Intl. Univ.

Abilene (US) of Internet 2.

SURFnet (NL) of SURFnet BV.

Arecibo has a dedicated 200 Mbit/sec, Internet-2 connection.In addition, for eVLBI run it borrows ~300 Mbps from the University of PR’s commodity internet, allowing data to be transferred at a rate of 512 Mbps.

Data leaving Arecibo

Scientific Results: Compact Cores in radio-quiet Seyfert galaxies: Giroletti et al.

“These are observations of parsec scale radio cores in Seyfert galaxies at 1.6 and 5 GHz. These galaxies are thought to be radio quiet, but it seems that the presence of a compact radio core is actually quite ubiquitous when the sources are observed with the proper sensitivity. Arecibo, of course, is essential for this goal, as it provides great sensitivity and long baselines (=high angular resolution) at the same time”.

Scientific Results contd.Scientific Results contd.: Supernovae & AGN(?) in the Western Nucleus of Arp220 - Conway, Lonsdale, et al.

eVLBI : Monitoring the Jet in M87 during a Tev Outburst (Giroletti et.al.)

Optical HST image of M87Jet & a knot of hot gas, HST-1, seen to be brightening in 2005

Superluminal motion in HST-1 during a TeV outburst

The inner Jet (collimated for ~200 mas) and the weaker complex, HST-1 (at 800 mas from the core), imaged at 5-GHz, with resolution 7 x 3 mas, and map noise of 0.12 mJy/beam.

Nov19

Jan27

Feb10Nov19Nov19

Mar02

Mar30

VLBI Sensitivity Upgrade VLBI Sensitivity Upgrade Increasing the US VLBI data recording rate to at least 4 Gbps by 2010:Goal set by the Taylor Committee.

Increasing the Bandwidth: Arecibo is in the process of:

(a) replacing the analog DAR with a Digital Back End (RDBE). - The Digital Down Conversion (DDC) personality consists of four independently tunable sub-bands per IF, with bandwidths 0.5 - 256 MHz and 1–8 bit output sample precision. There is also a Polyphase Filter Bank (PFB) personality with 32 sub-bands spanning the 500-MHz wide IF. Output is via 10-Gbit Ethernet transporting individual sub-band packet streams. Maximum data rate of 8 Gbps. Arecibo has ordered two RDEs from NRAO.

(b) upgrading to the Mark5C recording system developed by Haystack & Conduant Corp. Control software is still under development at Haystack. Arecibo has purchased and received two Mark5C units.

Increasing the Integration Time

VLBI is severely limited by ionospheric and tropospheric phase fluctuations, leading to a loss of coherence. As a solution, many VLBI observations these days are taken in “Phase referenced” mode. The most commonly used form of this mode needs slewing between the target and a strong, compact calibration source (generally within a few degrees of the target) every 3-4 min. Phase, derived from the calibrator, is then applied to the target data.

The low slew rate of 305-m antenna can lead to over 50% loss of integration time in phase-referenced VLBI.

The 12-m Antenna The 12-m Antenna Problem for the Big Dish - The low slew rate of 305-m antenna can lead to over 50% loss of integration time in phase-referenced VLBI.

Solution - A nearby antenna tracks the calibrator continually, while the 305-m tracks just the target, with occasional visits to the calibrator. Phase derived from the small antenna will be applied to the 305-m data under the assumption that the same ionospheric correction applies to both data sets.

How Big? - To provide a baseline sensitivity within a factor of 2 of an intra-VLBA baseline, the small antenna should be at least about 12-m. With this, sources brighter than ~110 mJy can be used as phase referencing calibrators.

Freq. Coverage - L, S, C & X bands are required for astronomy; S/X bands will be initially available. Eventually, 1 – 12 GHz will be covered.

Single Dish Uses - Education and research applications with Puerto-Rican universities and other educational establishments

Other Uses - (a) Possible participation in regular VLBA operations, and/or (b) VLBI2010; (c) The L-band, voltage beamwidth of a 12-m antenna contains all 7 ALFA beams, opening up the possibility of multi-beam interferometric applications..

Operational block diagram (evolving)

The 12-m Site The AUT Patriot 12-m Antenna

Timeline : 1. June 2010 – construction complete 2. Acceptance test using temporary backends, integrate RDBE+MK5C 3. Jan 2011 – test observations in VLBI mode at S/X 4. Wide band receivers by 2012

Science Areas: Astronomical VLBI with 305-m, Stand-alone VLBI for astronomy, astrometry & Geodesy, Single dish uses, and UG-teaching aid