MultiObject Survey Spectroscopy with CCAT Matt Bradford JPL Caltech September 21 2012 CCAT Extragalactic Workshop Boulder CO Highexcitation m olecular gas CO and water 5 CO transitions AND 6 water transitions ID: 505307
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Slide1
X-Spec:Multi-Object Survey Spectroscopy with CCAT
Matt Bradford (JPL / Caltech)
September 21, 2012
CCAT Extragalactic Workshop, Boulder, CO Slide2
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.
2Slide3
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.Slide4
Continuum surveys select high-z objects,not epoch-of-reionization objects
Bethermin
et al. 2011
Contributions 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 ratioSlide5
Wideband Spectroscopy Probes the Cosmic History of Star Formation
HeRMES Survey
Bright (lensed) sources identified at 250, 350, 500
m
m.HSLS 1Wang, Barger and Cowie, 2009July 2, 2012
5
BLISS 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 / CSO
K. Scott + 2011Slide6
CCAT Spectroscopic SensitivityCCAT – 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 10
12
Detect L ~ 3 x 10
11
L
sun
galaxy in 10
hrs
(3
σ
)
S. Hailey-
Dunsheath
SNR, 20hSlide7
Galaxy evolution in the first 1.5 billion yearsLF 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=7.3Galaxy luminosity function, converted to C+ ‘line counts’Slide8
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.Slide9
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 increases2) 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)Slide10
X-Spec Positioner, Concept & Optical Design
Assumes f/6, wideband horns
l
ens/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 planeSlide11
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 3
rd
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 FPSlide12
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.Slide13
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 subtractionSlide14
X-Spec MOS
P
ositioner
,
example concept based on commercial stagesSystem 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 / CSLASlide15
X-Spec MOS
Positioners
,
example layout of 96 on CCAT 2.8-m focal planeSlide16
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% fillingSlide17
SuperSpec: New On-Chip Spectrometer TechnologyCaltech & JPL
C.M. Bradford
G.
Chattopadhyay
P. DayS. Hailey-DunsheathA. KovacsC. McKenneyR. O’BrientS. PadinT. ReckE. ShirokoffL. SwensonJ. Zmuidzinas
Cardiff UniversityP. BarryS. Doyle
Arizona State U.P. MauskopfComplutense U. of MadridN.
LlombartU. ArizonaD.P.
Marrone
(boldface => postdoctoral researcher)Slide18Slide19
Erik
Shirokoff
,
SuperSpec
chip designInverted microstrip stackSlide20Slide21
7 mm
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 designSlide22
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 designSlide23
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.Slide24
Have designed a wideband smooth-wall horn + housing.
Probe is built on a 20-micron SOI layer.
Theodore
Reck
, Goutam Chattopadhyay @ JPLSlide25
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. Slide26
extraSlide27
10 arcmin
250µm
Wide-field imaging surveys now underway
Optical / near-IR
Far-IR / Submm
Backgrounds including Spitzer stacking analyses at 70, 160
m
m.
Dole et al. 2006.
Herschel SPIRE HERMES Survey at 250, 350, 500
m
m.
>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
27Slide28
Positioner Requirements
Requirement
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
Speed
Travel
Modulation profile
Dead time (time that we are neither on or off source)
Yes.
1 Hz requirement, 2 Hz goal
3-5 beams
Square 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.Slide29
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?Slide30
Tomography with C+30
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.Slide31
Tomography in C+: Power SpectraY. Gong, A. Cooray, et al.
31
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, 49GSlide32
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.Slide33
April 2008
7.9 hours
half
t
~0.5, half t~0.15 Molecular gas reservoirs probed with CO, H2OSlide34
SuperSpec
A revolutionary
on-chip, mm-wave
f
ilter-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 cm
2
, using a single RF single readout line. Another chip with separate horn / antenna + readout covers 320-470 GHz.