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The EVLA Project

The EVLA Project. Sean Dougherty National Research Council Herzberg Institute for Astrophysics. Rick Perley & Michael Rupen (NRAO) Peter Dewdney (HIA). What is the Very Large Array (VLA). What is the Very Large Array (VLA)?. Completed in 1980. 27 “movable” antennas. 25 m diameter each.

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The EVLA Project

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  1. The EVLA Project Sean Dougherty National Research Council Herzberg Institute for Astrophysics Rick Perley & Michael Rupen (NRAO) Peter Dewdney (HIA) The EVLA

  2. What is the Very Large Array (VLA) What is the Very Large Array (VLA)? Completed in 1980 27 “movable” antennas 25 m diameter each Receivers @ 92,21,6,3.6,2,1.3,0.7cm Total area = 130-m dish 100 MHz total bandwidth Y configuration (“2D” array) Longest baseline = 36 km World’s ‘largest’ array. The EVLA Sub - mm/mm Observing Techniques SMD – Basic Radio Astronomy Aug 14, 2006

  3. The VLA – the Scalable array Moveable Antennas Railroad and “trains” The EVLA

  4. Why upgrade the VLA? • The VLA is the world’s premier imaging radio telescope: • fast, sensitive, flexible, productive • If it’s so good – what’s the problem? • Astronomy today requires a more powerful and flexible radio telescope than the VLA. • more sensitivity • more frequency coverage • more spectral flexibility • better imaging…. • No significant technical upgrades since completion • 1970s technology severely limits scientific capability. • Modern electronics and signal processing  vastly increase the VLA’s scientific capabilities. The EVLA

  5. The EVLA Project – leveraging the VLA • Builds on the existing infrastructure • antennas, array, railroad, people • Implement new technologies • Receivers • Electronics • Data transmission • Correlator • Goal of ten Times the “astronomical capability” of the VLA • Sensitivity, Frequency coverage, Image Fidelity, Spectral Capabilities • On a timescale and cost far less than required to design, build, and implement a new facility. The EVLA

  6. EVLA: order-of-magnitude improvements • The EVLA performance is vastly better than the VLA • EVLA cost is less than ¼ the VLA capital investment • No increase in basic operations cost The EVLA

  7. Tsys lcm VLA EVLA 20 60 26 6 50 31 3.6 30 34 2 116 39 1.3 154 54 How is sensitivity improved? • Recall minimum detectable flux: • Reduce Tsys • Lower Trx - better receivers • Lower Tspill – new feed designs • Increase Ae via antenna efficiency • Improves both continuum & spectral line observations • For continuum, increase Dn • 100 MHz to 8 GHz The EVLA

  8. Frequency Coverage • Continuous frequency coverage from 1 to 50 GHz • a key EVLA requirement match instrument to science, not science to instrument! Blue - current VLA Green - EVLA Yellow letters and bars show band names and boundaries. Two low frequency bands (74 and 327 MHz) omitted The EVLA

  9. Point-Source Sensitivity Improvements : 1-s, 12-hours Red: Current VLA Black: EVLA Goals The EVLA

  10. Bandwidth, Spectral and Time resolution • Combination of 2:1 bandwidth ratios and huge number of spectral channels • instantaneous spectral indices, rotation measures, uv-coverage • instantaneous velocity coverage 53,300 km/s vs. current 666 km/s at 45 GHz • lines at arbitrary redshift • Spectral flexibility • 128 independently tunable sub-bands (vs. 2 currently) • “zoom in” on the lines of interest • Temporal flexibility • Fast time recording: initially 100 msec; 2.6 msec possible • Pulsars: 1000 phase bins of 200 μsec width, 15 μsec possible pulsar searches, timing, etc. with an interferometer! • Spectral/temporal capability due to the WIDAR correlator The EVLA

  11. The WIDAR correlator • Designed and built in Canada at HIA • $15M USD – initially enabled Canada’s participation in ALMA via the North American Partnership in Radio Astronomy (NAPRA) • 8-GHz bandwidth in each polarization covered by 4 x 2-GHz bands • Each of these 2 GHz bands covered by 16 sub-bands – each 128 MHz wide • 16,384 channels at 8 GHz bandwidth • 4,194,304 channels possible • 2 MHz – coarsest frequency resolution • 0.12 Hz – finest frequency resolution • Time sampling (up to 20 ms) • And lots more…………………………………………………… The EVLA

  12. The EVLA

  13. EVLA Design Driven By Four Science Themes Magnetic Universe Obscured Universe Image young stars and massive black holes in dust enshrouded environments. Measure the strength and topology of the cosmic magnetic field. Sgr A* Evolving Universe Transient Universe Study the formation and evolution of stars, galaxies and AGN. Follow the rapid evolution of energetic phenomena. CO at z=6.4 The EVLA

  14. Key EVLA Correlator Capabilities Deep Imaging Polarization • 8 GHz Bandwidth (dual polarization). • Full polarization processing. • Wide-field imaging. • 16,384 channels at max. bandwidth (BW). • >106 channels at narrow BWs. • Spectral resolution to match any linewidth. • Spectral polarization (Zeeman Splitting). Narrow spectral lines Wideband searches • Eight 2 GHz wide bands input. • Each input band decomposed into 16 tunable sub-bands of adjustable width • Gives 128 independent sub-bands Flexibility Many resources • 1000 pulsar “phase bins”. • “Single-dish” data output to user instruments. • Very fast time sampling (20 s). High time resolution The EVLA

  15. Synergy with ALMA • High-redshift star-forming galaxies • CO lines from star-forming galaxies • Key science goal of ALMA • At redshifts of a few CO J=1-0 and 2-1 line in EVLA bands • At high redshifts (z~6) CO J=3-2 line in EVLA bands • EVLA will detect synchrotron component out to z ~ 3 (normal) or z~5 (ultraluminous) • contribution of AGN • EVLA will detect free-free emission from HII regions out to z~ 2 • EVLA will be able to detect dust continuum out to redshifts > 10 • Young & proto-stellar objects • ALMA “bread and butter” – so where does the EVLA come in? • Defeat high dust opacity in the densest regions – opaque to 10’s of GHz • identify dust from free-free from synchrotron emission The EVLA

  16. Star-Forming Galaxies at High Redshift • Enabled by EVLA sensitivity • Synchrotron emission: AGN, SNR • Free-free emission: HII regions • Thermal dust emission • Resolution 50 mas = 200 pc @ z=10 • EVLA+ALMA • similar sensitivity • dust+ionized gas+NT • SED over 3-orders of magnitude in frequency • large range of redshift Spitzer dust non-thermal/AGN ionized gas Arp220 SED scaled to high redshifts. The EVLA

  17. Molecular lines in High-RedshiftStar-Forming Galaxies • Currently: • 50 MHz (z range of 0.001 at 50 GHz!) • Need to know a precise redshift or be lucky! • 8 spectral channels = no frequency resolution • No z searches • Very poor spectral resolution • Each line must be done independently (CO, HCN, HCO+, …) COJ=3-2 Z = 6.42 Peak ~ 0.6 mJy Carilli, Walter, & Lo The EVLA

  18. Molecular lines in High-RedshiftStar-Forming Galaxies • EVLA: • 8 GHz bandwidth @ 40-50GHz (z=1.4 -1.9 for CO J=1-0; z=3.8 to 4.8 for J=2-1) • 16384 spectral channels at maximum bandwidth • Searches are a piece of cake! • Other lines: HCN, HCO….. Arp 220 @ z=8 Red line = EVLA in 8 hrs CO J=1-0 @ 12.7 GHz J=2-1 @ 25.6 GHz J=3-2 @ 38.3 GHz The EVLA

  19. EVLA Setup for CO Z-Search • 42-50 GHz band provides lowest redshift. • z = 1.4 to 1.9 for J=1-0. • z = 3.8 to 4.8 for J=2-1. • v ~ 5.0 km s-1 (1 MHz). • 200 km-s-1 galaxy would occupy ~40 channels. • Interferometry • High resolution imaging. The EVLA

  20. Magnetic Fields in the ISM • ~30 H+ recom lines within 4 MHz band width (also He+, C+) • Each line individually targeted • Zoom in – 128 to 4 MHz • Each of 62 spectra gets 256 channels • Dn = 15.6 kHz (1.6 km/s) • EVLA imaging gives: • Gas density • Temperature • B-field (Zeeman splitting is weak - 2.8 Hz/mG) • Improve SNR by “stacking” 2 GHz

  21. Many Spectral Lines at once! • Nobeyama obs of TMC-1. • 414 lines (8 to 50 GHz) • 38 species • including “heavy” molecules • Slow rotators • Some may show Zeeman splitting. • EVLA can observe 8 GHz at once • an average of 80 lines • EVLA Correlator can “target” many (~60) lines at once. 8 GHz Kaifu et al., 2004. TA* The EVLA

  22. EVLA Project Status • Six (of 27) antennas currently withdrawn from VLA service, and being outfitted with new electronics. • Two antennas are fully outfitted, are now part of regular VLA observations • Two others being outfitted with final electronics, and under test. Available for astronomical use by late summer. • Two others in early stages of outfitting. • Antennas will be cycled through the conversion process at a rate six per year, beginning in 2007. The EVLA

  23. New Capabilities Timescale • The old correlator will be employed until the new correlator achieves full 27-antenna capability – mid 2009. • Full band tuning available before 2009, on schedule shown here. The EVLA

  24. Major Future Milestones • Test prototype correlator mid 2007 • Four antenna test and verification system • Not available for science • Correlator installation and testing begins: mid 2008 • Capabilities will rapidly increase until mid 2009. • Correlator Commissioning begins: mid 2009 • VLA correlator turned off • New correlator capabilities will be much greater at this time. • Last antenna retrofitted 2010 • Last receiver installed 2012 The EVLA

  25. Summary • The EVLA will improve the VLA capabilities more than tenfold through up-to-date receivers, data transmission and the WIDAR correlator • The project is on-track for completion in 2010 (antennas and correlator), and 2012 (for all frequency bands). • The HIA-designed WIDAR correlator is an essential and critical component of the EVLA. • Powerful new capabilities will begin to be available in 2008 • just two years from now! The EVLA

  26. The EVLA: A North American Partnership Project info: http://www.aoc.nrao.edu/evla/ The EVLA

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