X-Spec:Multi-Object Survey Spectroscopy with CCAT

Matt Bradford (JPL / Caltech)September 21, 2012

CCAT Extragalactic Workshop, Boulder, CO

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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.

Growth of Cosmic Star-Formation

SF history: Hopkins and Beacom, 2006

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.

Continuum surveys select high-z objects,not epoch-of-reionization objects

Bethermin et al. 2011Contributions to the CFIRB -> even the longest wavelengths have mean redshift < 2.8

J. Vieira

Far-IR / submm colors can select broadly high-z sources, but subject to a wide range in dust properties, not suitable for redshift binning.

350/870 flux ratio

WIDEBAND SPECTROSCOPY PROBES THE COSMIC HISTORY OF

STAR FORMATION HeRMES SurveyBright (lensed) sources identified at 250, 350, 500 mm.HSLS 1

Wang, Barger and Cowie, 2009

July 2, 2012 5BLISS for SPICA, M. Bradford et al.

Direct Z-Spec redshift with CO lines in the mm: z=2.95

Near-IR Imaging.Which / Where is counterpart ??

Near-IR Imaging.Kp-band Keck AO

CO 5-4 PdB

Z-Spec redshift enables PdB tuning for image of CO 5-4

Lens modeling w/ K, CO: m=10, Gavazzi+ 2011

Z-Spec / CSOK. Scott + 2011

CCAT Spectroscopic Sensitivity

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 x Npol) system with technology that can scale to produce

an instrument with thousands of beams in the 2020 decade.

L = 2 x 1012

Detect L ~ 3 x 1011 Lsun galaxy in 10 hrs (3σ)

S. Hailey-Dunsheath

SNR, 20h

Galaxy evolution in the first 1.5 billion years

• 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.

z=4.4z=7.3

Galaxy luminosity function, converted to C+ ‘line counts’

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.

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)

X-Spec Positioner, Concept & Optical Design

Assumes f/6, wideband horns

lens/M1 form Gaussian Beam Telescope

Concept paper: Goldsmith & Seiffert 2008

Detailed design for X-Spec: Steve Hailey-Dunsheath Could accommodate

220 in the full CCAT focal plane

1.4m (0.5°)

0.94m 56°

5° (half the width of an f/6 cone)

CCAT has curved, non-telecentric focal plane

• 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

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.

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

X-Spec MOS Positioner, example concept based on commercial stages

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.

Option to incorporate nutating M3 and additional M4 / wedge pair Lupe Balanes JPL / CSLA

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

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

11 cm upper arm, 89% filling

7cm upper arm, 69% filling

SUPERSPEC: NEW ON-CHIP SPECTROMETER TECHNOLOGY

Caltech & JPLC.M. BradfordG. ChattopadhyayP. DayS. Hailey-DunsheathA. KovacsC. McKenneyR. O’BrientS. PadinT. ReckE. ShirokoffL. SwensonJ. Zmuidzinas

Cardiff UniversityP. BarryS. Doyle

Arizona State U.P. Mauskopf

Complutense U. of MadridN. Llombart

U. ArizonaD.P. Marrone

(boldface => postdoctoral researcher)

Erik Shirokoff, SuperSpec chip design

Inverted microstrip stack

7 m

m

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

SuperSpec first 80-channel test device Yield in KID resonators nearly perfect! (now using 100-250 MHz KIDs)Feedhorn-coupled optical measurements coming soon.

KID coupling capacitors

mm-wave feedline (niobium, traveling horizontally)

KID resonator capacitors (titanium nitride, interdigitated)

mm-wave half-wave resonator (U-shape, niobium)

mm-wave absorber = meandered KID inductor (titanium nitride)

Erik Shirokoff, chip design

Excellent KID yield in SuperSpec Test ChipOptical 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.

Have designed a wideband smooth-wall horn + housing.Probe is built on a 20-micron SOI layer.

Theodore Reck, Goutam Chattopadhyay @ JPL

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.g z>4 galaxies).

• Studying a beam steering system to maximize science on the way to field-filling spectrograph.

EXTRA

10 arcmin

250µm

Wide-field imaging surveys now underway

Optical / near-IR Far-IR / Submm

Backgrounds including Spitzer stacking analyses at 70, 160 mm. Dole et al. 2006.

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.

250µm

350µm

500µm

July 2, 2012 27

Positioner RequirementsRequirement Value

Number of Elements Maximize subject to FOV and spacing between centers

Patrol radius > 14 cm (center of feed to center of M4), attempt to maximize

Spacing between element centers 2 * 12.124 cm (root3/2 * 14 cm)

Beam Switching?Switch SpeedTravelModulation profileDead time (time that we are neither on or off source)

Yes.1 Hz requirement, 2 Hz goal3-5 beamsSquare wave< 25% (for 3 Hz) settling time to 1/10 of a beam of 100 ms. 1/10 beam is 400 microns (gives 80% duty cycle at 1 Hz, 60% duty cycle at 2Hz)

Mapping mode for deep field? Use telescope raster

Positioning accuracy < 1/30 of a beam (<130 microns) [ beam: 3.6 mm ]

Field rotation sky tracking accuracy < 1/30 of a beam, sufficient rate to guarantee this accuracy

Typical observation time per config 8 hours

Lifetime > 10 years, operated at 50% of 16 hour nights duty cycle, with < 10% failure, refurbishment is okay.

Survival Temperature -40 to +40 C

Operational Temperature -10 to +20 C (TBC)

Optical alignment tolerance - TBD, allow shimming in mounting steering system to cryostat

Time to reconfigure for next field < 10 minutes

Optical alignment relative to cryostat mounting < 0.1 mm, allow shimming between cryostat and steering system upon assembly.

Relative alignment of mirrors in steering system < 0.1 mm, To be confirmed.

Optical / near-IR Spectroscopic Follow-Up

Even with counterparts, high redshift O/NIR spectroscopy challenging due to few lines, high and variable extinction in Ly-a.

MOSFIRE bands

Caitlin Casey

HeRMES SurveyBright (lensed) sources identified at 250, 350, 500 mm.HSLS 1

Near-IR Imaging.Kp-band Keck AO

Which source corresponds to the submm source?

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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.

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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

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.

April 20087.9 hours half t~0.5, half t~0.15

Molecular gas reservoirs probed with CO, H2O

SuperSpecA revolutionary on-chip, mm-wavefilter-bank spectrometer using kinetic inductance detectors (KIDs)

Simulated response for various channel spacing

Feedline and 2 full readout channels

Mm-wave radiation couples to a bank of half-wave resonant filters, deposits power in the MKID inductor

KID inductor

KID capacitor

mm resonator (filter) mm feedline

•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.