Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 The EVLA Project Sean Dougherty National Research Council Herzberg Institute for Astrophysics Rick Perley & Michael Rupen (NRAO) Peter Dewdney (HIA)

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

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 Moveable Antennas Railroad and “trains” The VLA – the Scalable array

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 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.

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 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.

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 EVLA: order-of-magnitude improvements ParameterVLAEVLAFactor Point Source Sensitivity (1- , 12 hours)10  Jy1  Jy 10 Maximum BW in each polarization0.1 GHz 8 GHz80 # of frequency channels at max. bandwidth1616, Maximum number of frequency channels5124,194, Coarsest frequency resolution50 MHz2 MHz25 Finest frequency resolution381 Hz0.12 Hz3180 (Log) Frequency Coverage (1 – 50 GHz)22%100%5 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

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 How is sensitivity improved? Recall minimum detectable flux: Reduce T sys –Lower T rx - better receivers –Lower T spill – new feed designs Increase A e via antenna efficiency Improves both continuum & spectral line observations For continuum, increase  –100 MHz to 8 GHz EVLA VLA cm T sys

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 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

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 Point-Source Sensitivity Improvements : 1- , 12-hours Red: Current VLA Black: EVLA Goals

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 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

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 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  s) And lots more……………………………………………………

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 EVLA Design Driven By Four Science Themes Magnetic Universe Obscured Universe Transient Universe Evolving Universe Measure the strength and topology of the cosmic magnetic field. Image young stars and massive black holes in dust enshrouded environments. Follow the rapid evolution of energetic phenomena. Study the formation and evolution of stars, galaxies and AGN. CO at z=6.4 Sgr A *

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 Key EVLA Correlator Capabilities Deep Imaging Polarization 8 GHz Bandwidth (dual polarization). Full polarization processing. Wide-field imaging. Narrow spectral lines Wideband searches 16,384 channels at max. bandwidth (BW). >10 6 channels at narrow BWs. Spectral resolution to match any linewidth. Spectral polarization (Zeeman Splitting). 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 High time resolution 1000 pulsar “phase bins”. “Single-dish” data output to user instruments. Very fast time sampling (20  s).

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 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

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 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 z=10 EVLA+ALMA – similar sensitivity – dust+ionized gas+NT –SED over 3-orders of magnitude in frequency – large range of redshift Arp220 SED scaled to high redshifts. Spitzer non-thermal/AGN ionized gas dust

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 CO J=3-2 Z = 6.42 Peak ~ 0.6 mJy Carilli, Walter, & Lo Molecular lines in High-Redshift Star-Forming Galaxies Currently: –50 MHz (z range of 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+, …)

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 EVLA: –8 GHz 40-50GHz (z= 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….. Molecular lines in High-Redshift Star-Forming Galaxies Arp z=8 Red line = EVLA in 8 hrs CO 12.7 GHz 25.6 GHz 38.3 GHz

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 EVLA Setup for CO Z-Search 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.

~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  = 15.6 kHz (1.6 km/s) EVLA imaging gives: Gas density Temperature B-field (Zeeman splitting is weak Hz/  G) Improve SNR by “stacking” 2 GHz Magnetic Fields in the ISM

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 Many Spectral Lines at once! Nobeyama obs of TMC 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. TA*TA* 8 GHz Kaifu et al., 2004.

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 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.

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 New Capabilities Timescale The old correlator will be employed until the new correlator achieves full 27-antenna capability – mid Full band tuning available before 2009, on schedule shown here.

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 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 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

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 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!

Sub-mm/mm Observing TechniquesThe EVLAAug 14, 2006 The EVLA: A North American Partnership Project info: