X- Spec: Multi-Object Survey Spectroscopy with CCAT

1. X-Spec:Multi-Object Survey Spectroscopy with CCAT Matt Bradford (JPL / Caltech) September 21, 2012 CCAT Extragalactic Workshop, Boulder, CO

2. High-excitation molecular gas: CO and water • 5 CO transitions AND 6 water transitions. • 1 confirmed with CARMA, more coming. • CO cooling fit with XDR model. • Water spectrum looks like that of Mrk 231 as measured with Herschel SPIRE, but scaled up and more highly excited. • -> Water is pumped with local far-IR radiation field, but over hundreds of parsecs. • Water abundance ~1.4e-7, explained by XDR chemical model.

3. Growth of Cosmic Star-Formation We would like to chart the onset and early growth of star formation in the epoch prior to z=4 (the first 1.5 Billion years) ? e.g. was this dominated by massive galaxies or small ones? How much does dusty SF contribute? z>4 has large uncertainties and all data on this epoch comes from rest-frame UV / optical surveys (Lyman break sources) Require redshift-resolved far-IR / submm luminosity functions to complement UV-based studies. SF history: Hopkins and Beacom, 2006

4. Continuum surveys select high-z objects,not epoch-of-reionization objects 350/870 flux ratio J. Vieira Bethermin et al. 2011 Contributions to the CFIRB -> even the longest wavelengths have mean redshift < 2.8 Far-IR / submm colors can select broadly high-z sources, but subject to a wide range in dust properties, not suitable for redshift binning.

5. Wideband Spectroscopy Probes the Cosmic History of Star Formation Near-IR Imaging. Which / Where is counterpart ?? HeRMES Survey Bright (lensed) sources identified at 250, 350, 500 mm. HSLS 1 Wang, Barger and Cowie, 2009 Direct Z-Spec redshift with CO lines in the mm: z=2.95 Near-IR Imaging. Kp-band Keck AO Z-Spec redshift enables PdB tuning for image of CO 5-4 Z-Spec / CSO K. Scott + 2011 CO 5-4 PdB Lens modeling w/ K, CO: m=10, Gavazzi+ 2011 BLISS for SPICA, M. Bradford et al.

6. CCAT Spectroscopic Sensitivity SNR, 20h L = 2 x 1012 CCAT – X-Spec vs ALMA for line surveys • ALMA is ~13 times more sensitive than CCAT, per CCAT spectrometer beam (CCAT single pol) • ALMA: 8 GHz BW, requires ~30 tunings to cover Band 1 + Band 2, but assume only 8 tunings to measure z. • A~30-beam X-Spec is a factor of 1.3 times faster than ALMA (or 15 beams x 2 polarizations). • A ~300-beam X-Spec is 13 times faster than ALMA (or 150 beams x 2 polarizations). • First light: 30-300 (beam xNpol) system with technology that can scale to produce an instrument with thousands of beams in the 2020 decade. S. Hailey-Dunsheath Detect L ~ 3 x 1011Lsun galaxy in 10 hrs (3σ)

7. Galaxy evolution in the first 1.5 billion years Galaxy luminosity function, converted to C+ ‘line counts’ z=4.4 z=7.3 • LF at early times completely unconstrained. Extrapolations from UV fluxes to total luminosity very uncertain. • Redshifts estimated via far-IR / submm colors have large intrinsic uncertainty. • Want ~ 10k spectroscopic redshifts in order to provide well-sampled luminosity functions from z=10 to z=4 in Dz/(1+z)=5% bins Can’t do with ALMA.

8. X-Spec / CCAT Spectroscopic Survey Goals • Measure high-z (z>4) luminosity functions w/ C+ by following up ‘red’ submm / mm sources: ~8 redshift x ~8 luminosity bins reaching below the knee, 100 sources per bin --> 1000s of redshifts. • Also provides independent study of growth of structure, require depth which gives ~100 sources per square degree (per redshift bin) over >20 square degrees. • C+ detections also provide interstellar gas properties (mass, temperature, UV field strength) • Measure molecular gas content in galaxies through the bulk of SF history (z=4 to 1) with the CO rotational ladder, both individual sources and stacking on known (e.g. optical) redshifts. • Requires 30-300 beams on the sky with full coverage of low-frequency atmospheric windows. • ALMA (8GHz) requires 10-20 years. 100-object X-Spec CCAT requires ~3 years.

9. Implementation of X-Spec for CCAT • Long-term prospect for CCAT: up to a square degree of individual spectrometer pixels (3e4 x 1e3 = 3e7 detectors, 2030 in Zmuidzinas law) • Core technology is new superconducting on-chip filter-bank spectrometer SuperSpec with on-board Kinetic Inductance Detector (KID) array: • 500-channel R=700 chip covers Band 1 or Band 2, each is a few cm2 in size • Low-cost microfabrication -> instrument cost not dominated by detectors themselves. • Each chip (each spectrometer beam) coupled with a feedhorn or planar antenna. • At first light we will deploy 30-300 beams, depending primarily on the cost of KID readouts. • Studying 2 system architectures with downselect during design phase: • 1) Direct multi-pixel spectral imager scans the sky as per bolometric cameras • Single-band array. • Eventual architecture of choice as pixel count increases • 2) Incorporate steered front end for each spectrometer with an articulated quasioptical relay to couple to galaxy with a known position. • Optimal in the limit of small number of pixels, since source density on the sky is 1e-2 to 1e-3 per beam. Sensible if steering system is less expensive than ~10-100 spectrometer chips + readouts. • Use dual-band, dual pol architecture (4 chips per feed unit)

10. X-Spec Positioner, Concept & Optical Design Concept paper: Goldsmith & Seiffert 2008 lens/M1 form Gaussian Beam Telescope Detailed design for X-Spec: Steve Hailey-Dunsheath Assumes f/6, wideband horns Could accommodate 220 in the full CCAT focal plane

11. CCAT has curved, non-telecentric focal plane 5° (half the width of an f/6 cone) 0.94m 56° 1.4m (0.5°) • Considered adding 3rd mirror to CCAT, e.g. 3-mirror anastigmat • loses field and/or aperture, also expensive and unwieldy. • Considered correcting sub-fields with refractive optics in front. • possible, but large sub-fields require large optics, adds warm loading, lose overlap of positioners. • Add degrees of freedom to the positioner to accommodate the FP

12. Option 1: Aligning steering system to beams, then requires z translation of up to 30 cm. Option 2: Aligning steering system to local focal surface, then requires articulation of first mirror or additional optic.

13. Modulation for X-Spec? Z-Spec / CSO PSDs , knee at 0.2--0.5 Hz CCAT has no chopping secondary, has beam switching speed of 0.5 sec. -> 75% duty cycle corresponds to 0.25 Hz -- insufficient -> will test spectral template subtraction

14. X-Spec MOS Positioner, example concept based on commercial stages Option to incorporate nutating M3 and additional M4 / wedge pair Lupe Balanes JPL / CSLA System w/ Aerotech stages handily meets requirements for positioning accuracy under loads, tracking speed, but can’t chop. Hardware cost ~$10-15k upper limit. Custom system may be cheaper.

15. X-Spec MOS Positioners, example layout of 96 on CCAT 2.8-m focal plane

16. X-Spec MOS Positioners, example layout of 96 on CCAT 2.8-m focal plane 7cm upper arm, 69% filling 11 cm upper arm, 89% filling

17. Caltech & JPL C.M. Bradford G. Chattopadhyay P. Day S. Hailey-Dunsheath A. Kovacs C. McKenney R. O’Brient S. Padin T. Reck E. Shirokoff L. Swenson J. Zmuidzinas Cardiff University P. Barry S. Doyle Arizona State U. P. Mauskopf Complutense U. of Madrid N. Llombart U. Arizona D.P. Marrone SuperSpec: New On-Chip Spectrometer Technology (boldface => postdoctoral researcher)

19. Inverted microstrip stack Erik Shirokoff, SuperSpec chip design

21. SuperSpec first 80-channel test device Yield in KID resonators nearly perfect! (using 100-250 MHz KIDs) Feedhorn-coupled optical measurements coming soon. Erik Shirokoff, chip design 7 mm

22. SuperSpec first 80-channel test device Yield in KID resonators nearly perfect! (now using 100-250 MHz KIDs) Feedhorn-coupled optical measurements coming soon. Erik Shirokoff, chip design mm-wave feedline (niobium, traveling horizontally) mm-wave half-wave resonator (U-shape, niobium) mm-wave absorber = meandered KID inductor (titanium nitride) KID resonator capacitors (titanium nitride, interdigitated) KID coupling capacitors

23. Excellent KID yield in SuperSpec Test Chip • Optical measurements coming soon: • Coupling efficiencies, into chip and chip to resonator. • Loss in the microstrip (dielectric). • Responsivity of the TiN KID under operational loadings (lower photon = quasiparticle density than for SWCam prototype). • Noise performance of the KID. • Will inform 500-channel prototype design.

24. Have designed a wideband smooth-wall horn + housing. Probe is built on a 20-micron SOI layer. Theodore Reck, GoutamChattopadhyay @ JPL

25. Summary • Wideband multi-object spectroscopy with CCAT enables powerful 3-D surveys impossible with ALMA. • Fine-structure + molecular transitions probe physical conditions in embedded in dusty galaxies. • Individual detections + stacking on optical / near-IR redshifts around the SF history peak. • Unique redshift survey sensitivity for earliest times using C+ (z=4-9) • Fluctuation analyses for sub-threshold sources. • Full capitalization of CCAT wide field and sensitivity requires large-format spectrograph (10s to 1000s of beams, each with 500-1000 detectors). • Developing an on-chip filterbank spectrograph, a natural outgrowth of superconducting transmission line technology and large-format arrays. • Source densities, even for sub-threshold populations are sparse on the sky, particularly for interesting sub-samples (e.gz>4 galaxies). • Studying a beam steering system to maximize science on the way to field-filling spectrograph.

26. extra

27. Wide-field imaging surveys now underway 250µm 250µm 350µm Backgrounds including Spitzer stacking analyses at 70, 160 mm. Dole et al. 2006. Far-IR / Submm Optical / near-IR 500µm Herschel SPIRE HERMES Survey at 250, 350, 500 mm. >27,000 galaxies in 20 square degrees so far. This is just the tip of the iceberg. J. Bock, S. Oliver et al. 10 arcmin

28. Positioner Requirements

29. Optical / near-IR Spectroscopic Follow-Up HeRMES Survey Bright (lensed) sources identified at 250, 350, 500 mm. HSLS 1 MOSFIRE bands Caitlin Casey Near-IR Imaging. Kp-band Keck AO Even with counterparts, high redshift O/NIR spectroscopy challenging due to few lines, high and variable extinction in Ly-a. Which source corresponds to the submm source?

30. Tomography with C+ Background-limited sensitivity relative to the mean intensity. This gets much harder at earlier times. Power spectrum measurement requires only fractional SNR in each spatial-spectral bin (voxel) • Lower-redshift measurement in 650, 850 micron windows a first step.

31. Tomography in C+: Power SpectraY. Gong, A. Cooray, et al. The aggregate glow of undetected small galaxies. Shot-noise dominates, but clustering enters at low k. Error bars based on Z-Spec like instrument scaled up to 64 spatial pixels, and R=700 with 312 spectral pixels -> 20,000 total detectors.  Need integral field on-chip spectrometers. Assume mapping 16 square degrees with 4000 hours total. TIME experiment under development at Caltech / JPL (J. Bock + others). Precursor experiment at z=4.5 likely first step, e.g. at CSO. 2012 ApJ 745, 49G

32. Cross correlation C+ with HIY. Gong, A. Cooray, et al. Basic C+ sensitivity independent of aperture, but would like to probe angular scales which show inversion of correlation with HI. • Large scales: HI anticorrelated with galaxies which produce reionizing photons. • Anti-correlation disappears on scales of the ionizing bubble size. arxiv.org/1107.3553v1 • 10m aperture for C+ is well-suited to comparison with 21-cm experiments. • a potential long-term future experiment at CSO or GLT: automated, low overhead, if the instrumentation can be developed.

33. Molecular gas reservoirs probed with CO, H2O April 2008 7.9 hours half t~0.5, half t~0.15

34. Feedline and 2 full readout channels SuperSpec A revolutionary on-chip, mm-wave filter-bank spectrometer using kinetic inductance detectors (KIDs) KID inductor KID capacitor mm resonator (filter) mm feedline Mm-wave radiation couples to a bank of half-wave resonant filters, deposits power in the MKID inductor • Signal coupled via a feedhorn propagates on a superconducting transmission line. • A suite of half-wave resonators, one for each frequency bin, is coupled to the main feedline and to a direct detector (a KID). • For CCAT X-Spec, we will have ~500 channels from 195-305 GHz in a chip of size is 2-4 cm2, using a single RF single readout line. Another chip with separate horn / antenna + readout covers 320-470 GHz. Simulated response for various channel spacing