Status of the Large Millimeter Telescope (and use of CASPER electronics)

Transcription

1 Status of the Large Millimeter Telescope (and use of CASPER electronics) Gopal Narayanan University of Massachusetts, Amherst 1 of 41

2 Overview LMT Status Brief Outline of Scientific Results New Instruments SEQUOIA 3mm Focal-Plane Array with ROACH-2 based spectrometer backend Phased Focal Plane Array (PFPA) for GBT & LMT 1mm VLBI Receiver & One Millimeter Array Receiver 2 of 41

3 About the LMT... 50m diameter millimeter-wave telescope 75 microns RMS surface accuracy 1 arcsec relative pointing Active Primary Surface Focal Plane Array Instrumentation 3 of 41 Binational Collaboration with Mexico Site in state of Puebla, MX 15,000' Seasonal site: Submm winter; 3mm summer.

4 The LMT Scoreboard Specification Diameter Surface Accuracy Active Surface RMS (microns) Elevation Range Desired Achieved (2014) 50m 32m Yes deg Yes deg N/A < Pointing Accuracy Absolute Relative 4 of 41

5 The LMT Scoreboard Specification Diameter Surface Accuracy Active Surface RMS (microns) Elevation Range Desired Achieved (2014) 50m 32m Yes deg Yes deg N/A < Pointing Accuracy Absolute Relative Two Instruments in place: AzTEC 144 -pixel 1.1mm continuum camera Redshift Search Receiver 3mm ultrawideband (38 GHz) spectrometer Second Season of Early Science Observations 5 of 41

6 AzTEC at the LMT 144-pixel bolometer array 1.1mm Wavelength 8 HPBW Lissajou On-the-Fly Mapping 6 of 41

7 AzTEC Image of M87 7 of 41 Image Courtesy: G. Wilson

8 8 of 41 Image Courtesy: D. Sanchez

9 Redshift Search Receiver GHz 38 GHz Bandwidth 31 MHz Resolution Erickson, Narayanan et al (2007) Arp 220 Dual Polarization, Dual Beam Receiver Excellent baselines High Sensitivity Trx ~ 75K Tsys ~ 100K One Hour Integration No Baselines Removed 9 of 41

10 Arp of 41 Image Courtesy: P. Schloerb

11 Molecular Line Detections in Arp 220 Molecule Transition ch3cn 13co hnco c18o hcccn v7 hcccn v7 hcccn hcccn v7 hcccn v7 hcccn cs ch3oh c34s n2h+ ch3cn hcccn v7 hcccn v7 hcccn hnc hco+ hcn hnco c2h c2h sio h13co+ h13cn hcccn v7 hcccn v7 hcccn (0,5)-4(0,4) (0,2)-1(0,1) (0,4)-3(0,3) 1-0 1/2-1/ /2-1/ Frequency Amplitude (GHz) (mjy) of 41 Error (mjy) SNR

12 LMT's Killer App Galaxy Evolution Submm View Optical View Williams et al Hughes et al of 41

13 What are the Submm Galaxies? ULIRGs at high redshift? Ultraluminous infrared galaxies (ULIRGs): Dusty, LIR>1012LSolar High rates of Star Formation Gas rich interacting/merging Surace, Sanders, & Evans 1999 Spectral energy distribution: strong peak near 100 micron from warm dust Peak gets redshifted to 1 mm by z~10 13 of 41 Yun 2000

14 Observations of Distant Galaxies Age of Universe (GYr) TODAY's LMT 5-sigma In 10 sqr arcmin Map with 2 hours Integration time Z Redshift 14 of 41 Continuum flux from dusty starbursts is almost independent of redshift In some models and cosmologies, objects get brighter with z.

15 9io9 (z=2.54) AzTEC (8 ) 9io9 identified as lensed object by volunteers in Zooniverse Project! 15 of 41

16 PJ (z=3.00) AzTEC (8 ) 16 of 41

17 HJ (z=3.26) Fu et al. (2012) Red arcs are lensed images of the z=3.26 galaxy 17 of 41

18 First VLBI Fringes The Future: Make an image of the Supermassive Black Hole at the center of the Galaxy with the Event Horizon Telescope 18 of 41

19 The Future The LMT works and is doing scientific work! Mexico committed to completing the full 50m antenna. Assuming timely allocation of funds, expect full 50m will be complete in Next generation of instruments coming online: SEQUOIA 16-pixel 3mm heterodyne focal plane array equipped with ROACH-2 based backend spectrometers A 1-mm single-pixel SIS receiver for VLBI observations 19 of 41

20 The Future (contd) Proposed New Instruments Phased Focal Plane Array at 3mm wavelength Heterodyne Focal Plane array at 1mm wavelength Follow-up to AzTEC a very large format mult-color TolTEC instrument 20 of 41

21 Introducing WARES (Wideband, Array, Roach Enabled Spectrometer) SEQUOIA 16 pixel GHz focal-plane array using MMIC LNA Amplifiers Used at the Quabbin 14m radio telescope for several years To be installed on the LMT for the season Will need new optics to interface with the LMT, and a new spectrometer 21 of 41

22 Wideband Spectrometer System for SEQUOIA 22 of 41

23 Wideband Spectrometer Modes Mode BW (MHz) NumChannels Resolution (khz) Velocity Resolution (km/s) of 41

24 Wideband Spectrometer Modes Mode BW (MHz) NumChannels Resolution (khz) Velocity Resolution (km/s) Future NB Spectrometer Based on LEDA 16-channel ADC using 2 (or 4) ROACH-2 boards Mode BW (MHz) NumChannels Resolution (khz) Velocity Resolution (km/s) of 41

25 Phased Focal Plane Array for GHz Neal Erickson, Gopal Narayanan, Joe Bardin Univ Massachusetts, Amherst Brian Jeffs and Karl Warnick Brigham Young Univ Karen O Neil NRAO, GBT 25 of 41

26 Conventional Focal Plane Array Large gaps between elements, 2x HPBW spacing. No ability to optimally illuminate telescope, particularly over a wide bandwidth. Relatively few elements fit into focal plane. Difficult to adapt to varying f ratios. Physically large. 26 of 41

27 Phased Focal Plane Array somewhat idealized Very small feeds, spaced ~ /2, are able to collect all of the signal in the focal plane. Combine feeds into groups that synthesize the optimum illumination. Requires amplification before combination. Correct for large scale telescope surface errors. Easily adapted to any telescope f ratio. Physically very small. 27 of 41

28 PFPA Goals Build a 64 element receiver. Demonstrate at the GBT that this is a viable mmwave technology. RF bandwidth GHz. Excellent band for GBT science. SiO, HCN, DCN, HNC, HCO+ IF bandwidth will be ~ MHz. Beam-forming is all digital (no analog summing). Budget is very limited, $1.3M, 3 years. 28 of 41

29 Waveguide Feed Element Machine the entire feed array including splitter from a single piece of aluminum. 29 of 41

30 Array Architecture One MMIC gain stage at 20K, 2nd stage at room temp. 30 of 41

31 First Stage Amplifier Circuit Board Separate drain bias for each element. 31 of 41

32 Beam Forming General process is very much like interferometry. 1. Form complex spectrum from each element. 2. Vector sum elements with predetermined weights.. Real-time summing network is very complex, 169 summing engines each with up to 25 inputs. If we allow for arbitrary focal plane distribution, then each beam requires all 64 inputs. Record and post-process may be needed 32 of 41

33 Beam Forming All signal processing uses ROACH boards with 64 channel ADC board Our budget is 8 boards, which may greatly limit the bandwidth (and resolution) we can process. ROACH2 boards much more capable. Interconnections in summing network require fast ethernet switch. 33 of 41

34 1mm Receivers For upcoming VLBI runs for EHT at the LMT, building a 1mm dual polarization sidebandseparation receiver with 4 12 GHz IF outputs (MSIP proposal outstanding) Also proposing to build over next 3-4 years, a 16-pixel dual-polarization (2x4x2) onemillimeter array receiver (OMAR) using SIS mixers will use CASPER-based spectrometers built for SEQUOIA for backend 34 of 41

35 Summary LMT is not fully complete but is already a working instrument, collecting valuable science A wideband array spectrometer based on ROACH-2 and ASIAA ADCs is being put together for the SEQUOIA FPA A novel Prototype Phased Focal Plane Array Receiver is being built to be commissioned at the GBT such instruments are poised to revolutionize heterodyne radio astronomy at mm/submm wavelengths 1mm wavelength single-pixel receiver for the EHT project is being prepared for the LMT OMAR a 1mm wavelength focal-plane array receiver for LMT 35 of 41

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37 Supplementary Slides 37 of 41

38 Combined Feed Element Waveguide port Waveguide port must be dielectric filled for best match, = of 41

39 Cold Preamp Circuit Design One continuous soft circuit board for all elements. Waveguides in and out pass through the circuit board, conductive vias act as waveguide walls. Circuit is glued to one block, clamped against another. In Pockets cut through board for MMIC amps and bias network. Single element of circuit board, repeated 64 times. Out 39 of 41

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41 OMAR 41 of 41