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Direct-Detection Spectroscopy at the CSO with Z-Spec and ZEUS

Direct-Detection Spectroscopy at the CSO with Z-Spec and ZEUS. Probing galaxies near and far with two new bolometers-based grating spectrometers Matt Bradford with input from Gordon Stacey August 4, 2008. Dominant gas coolants are in the far-IR / submm Redshifted to the submm / mm.

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Direct-Detection Spectroscopy at the CSO with Z-Spec and ZEUS

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  1. Direct-Detection Spectroscopy at the CSO with Z-Spec and ZEUS Probing galaxies near and far with two new bolometers-based grating spectrometers Matt Bradford with input from Gordon Stacey August 4, 2008

  2. Dominant gas coolants are in the far-IR / submmRedshifted to the submm / mm CSO @ z=0 CSO @ z=1.2 CSO @ z=2.6 CSO @ z=4.4 O++ O0 C+ N+ C0 CO SED courtesy A. Blain

  3. The World’s Only Submillimeter Grating Spectrometers ZEUS The Redshift (z) and Early Universe Spectrometer Stacey et al. (Cornell) w/ GSFC, NIST • Short submm windows: 350mm, 450mm • Slit-fed echelle grating, 4th and 5th order • Resolving power ~1200 (300 km/s) • 20 GHz (~2-4%) instantaneous bandwidth • 1x32 bolometer array, but TES upgrade underway Z-Spec Glenn (U. Colorado); Bradford, Bock, Zmuidzinas, (Caltech), Aguirre (CU-> Penn), Matsuhara (ISAS) • 1 mm window: 195-310 GHz • Single beam w/ new waveguide grating architecture • Resolving power ~300 (1000 km/s) • 115 GHz instantaneous bandwidth • 160 individually-mounted Ge-sensed bolometers Both with sensitivity very close to fundamental limits at the CSO

  4. Primary Scientific Objectives • ZEUS • J=6->5 and 7->6 in both 12CO and 13CO and [CI] J=2->1 constrain the mass and energy budget of the warm molecular gas. • Z-Spec • Complete 1-mm spectrum includes multiple high-critical-density species: CN, CS, HCN, HNC, HCO+. A rapid census of the dense molecular gas. • Embedded energy sources and conditions of star forming gas in local-universe infrared-bright galaxies (LIRGS and ULIRGS). • Interstellar medium conditions and spatial extent of star formation extent in the era of peak star-formation history (z=0.5 to 2) and prior. • Evolutionary history of energy release via unbiased redshift surveys. • ZEUS • C+ at z=1--1.2 and 1.8--2. C+ to dust continuum ratio measures the UV field intensity, constrains the extent of the starburst. • Access [OI], [NII], [OIII] at the highest redshifts. • Z-Spec • Full band provides at least 2 CO transitions to measure redshift as well as temperature, density, and mass of the molecular gas. • Unexplored rest-frame short-submm. • C+, other fine-structure transitions accessible beyond z=6.

  5. ZEUS on the CSO • Mounted on the left Nasmyth focus • Can be co-mounted with both Z-Spec and Bolocam • First light in 2006 • Steve Hailey-Dunsheath PH.D. (Cornell 2008) • Thanks to NSF and NASA support: • NSF ATI: 01-04, 04-07, 07-10 • NSF MRI for ZEUS-2 • NASA GSRP

  6. ZEUS Observations of LIRGs & ULIRGs IRAS 18293 Arp 220 CO(6-5) CO(6-5) IRAS 17208 CO(6-5) NGC 6240 CO(6-5) TMB(K) NGC 6240 CO(8-7) NGC 6240 [CI] (2-1) & CO (7-6) VLSR(km/s) VLSR(km/s) • Pre-ZEUS: 1 ULIRG in CO 6-5 (Mrk 231, Papadopoulos et al. 07) • ZEUS has observed ~19 LIRGs and ULIRGs to date • Most in CO (6-5) • Some also in CO (7-6) & [CI] (2-1) or CO (8-7) • Fractional mid-J CO luminosity decreases in the most powerful sources (as with C+). • -> More concentrated systems than the less-luminous starbursts. Nikola et al. in prep.

  7. ZEUS High-Redshift Example: [CII] from MIPS J142824.0 +352619 • Identified as red object in MIPS Bootes field (Borys et al. 2006) • Integrated far-IR SED indicates Lfar-IR ~ 3.21013 L • Likely a mildly lensed super-starburst galaxy • ZEUS/CSO detection in April 2008 -- 1.5 hours of good (but not great) weather (225 GHz ~ 0.05 to 0.06) • I[CII] ~ 6 K-km/sec • Fline ~ 9.0  10-18 W m-2 • L[CII] ~ 2.5  1010 L • CII / far-IR ratio much greater than in local ULIRGs. Conclude that starburst is 2-3 kpc in extent – “galaxy wide starburst” Hailey-Dunsheath et al. 2008

  8. curved grating in parallel plate waveguide Z-Spec: A New Ultracompact Waveguide Grating • Propagation confined in parallel-plate waveguide • 2-D Geometry • Stray light eliminated • Curved grating diffracts and focuses • Efficient use of space • No additional optical elements • Custom “stigmatic” grating design possible at long wavelengths K.A. McGreer, 1996, IEEE Phot. Tech. 8 H.A. Rowland, 1883, Phil. Mag16

  9. Z-Spec Layout INPUT FEEDHORN GRATING ARC Individually mounted SiN bolometers Focal ARC CSO, Mauna Kea FRIDGE 3He RADIATION SHIELD ADR

  10. Z-Spec Support • NSF career (Glenn) + CSO • NASA SARA • JPL DRDF, Caltech Pres. Fund + Millikan • U. Colorado + Research Corp Z-Spec graduate students @ 13,400 ft Lieko Earle (Colorado), Bret Naylor (Caltech)

  11. Z-Spec 1 mm survey of NGC 253 Lieko Earle, U. Colorado Ph.D. ‘08 3.5 hours telescope time >15ID’d transitions > 3s +2-4 unID’d as of yet.

  12. Z-Spec Spectra from the CSO

  13. Z-Spec Spectra from the CSO

  14. Molecular Gas in Local-Universe Galaxies, ex. M82 B. Naylor et al., ApJ in prep. Compile all transitions, use RADEX to model excitation & transfer in the lines -> Generate Bayesian likelihoods HCO+ NE SW Cen Also include: CS HNC SO2Combine in a single model: -> evidence of cold, dense gas component -> the material actually forming the stars?

  15. 7.9 hours total time

  16. Weiss et al. continuum estimates

  17. Z-Spec Barvainis et al., 1997 Weiss et al., 2003

  18. APM 08279+5255 at z=3.91 Flux Density [Jy] Rest 322 mm 200 mm

  19. APM 08279+5255 at z=3.91 A reminder: Arp 220 in the far-IR ISO LWS, Gonzalez-Alfonso et al. 04 Flux Density [Jy] Rest 322 mm 200 mm

  20. APM 08279+5255 at z=3.91 Flux Density [Jy] Rest 322 mm 200 mm

  21. Plans for the next cycleZEUS & Z-Spec instrument teams funded Z-Spec Survey Program Funded by NSF AAG (Aguirre et al. U. Penn) • Dense gas in Local-Universe dense molecular gas surveys. • 50 galaxies, 8 hours per • Mid-J CO + spectral discovery in high-z objects with and without prior redshifts. • 20 galaxies, 24 hours per • Excellent use of low-frequency time at CSO. • Baseline 300 hours per year, could be more. • Helium recycler under study to reduce cryogen costs. ZEUS upgrade to ZEUS-2 Funded by NSF MRI • Incorporating (3) NIST 2-d TES bolometer arrays which share the focal plane and can operate simultaneously: • 10 x 24 at 200 mm • 9 x 40 at 350-450 mm • 5 x 12 at 650 mm • Up to 5 lines simultaneously (in extended sources) • Some imaging capability (9-10 beams) • Closed cycle refrigerators

  22. Backup material

  23. Direct-Detection SpectroscopyA survey capability which complements the high spatial and spectral resolution of interferometers (CARMA / ALMA) • Submillimeter is the region of overlap between coherent (heterodyne) and incoherent (direct-detection) techniques for astrophysics. • Coherent approaches have yielded much of the spectroscopic work to date. • High spectral resolution required for Galactic cores. • Large bandwidths not essential for Galactic sources or nearby galaxies. • SIS mixers near quantum limit, (also near background limit at 1 mm). • Until recently, direct detectors neither sufficiently sensitive, nor sufficiently arrayed to be compelling. • Direct-detection spectrometers (gratings and Fabry-Perots) for long wavelengths are large and expensive. • Direct-detection submillimeter spectrometers are now compelling • Submillimeter spectroscopy coming of age as an extragalactic probe. • Spectral resolution greater than few x 1000 not required. • Direct detectors are now readily background-limited, and are undergoing a revolution in format (driven by cameras). • Large fractional bandwidth presents a new discovery space for measuring redshifts and multiple lines. • Multi-object capability a natural progression with a direct-detection system.

  24. Grant Numbers • ZEUS • NSF Grant AST-0096881 (Advanced Technology and Instrumentation 2001-2004) • NSF Grant AST-0352855 (Advanced Technology and Instrumentation 2004-2007) • NSF Grant AST-0705256 (Advanced Technology and Instrumentation 2007-2010) • NASA Grant NGT5-50470 (NASA GSRP 2003-2006) • NSF Grant AST-0722220 (Major Research Instrumentation 2007-2010) • Z-Spec • NSF CAREER grant (Glenn): AST0239370 • NASA SARA grants: NAG5-11911 • JPL DRDF • Caltech President's Fund • Caltech Millikan Fellowship • Research Corporation Innovation Award: RI-0928 • University of Colorado

  25. ZEUS: Optical Path Grating BP Filter Wheel M4 LP Filter 2 Grating Detector Array M6 M2 M3 4He Cold Finger LP Filter 1 Entrance Beam f/12 Quartz & LP Filter 1 M5: Primary M1 Scatter Filter Dual Stage 3He Refrigerator Refrigerator 4He cryostat • 35 cm long R2 echelle grating blazed for 5th order @ 359 m • There is a series of a scatter, quartz, 2 long  pass, and a bandpass filter in series to achieve dark performance (Cardiff U.) • Total optical efficiency: ~ 30%, or 15% including bolometer DQE

  26. ZEUS/CSO  ZEUS observations of NGC 253: First Extragalactic Detection of 13CO(6-5) • Line is bright ~ 10% that of the 12CO(6-5) line indicating optically thick emission in the main line. • Also re-observed (and mapped) the CO(7-6) line to constrain LVG models • 35 to 55% of the molecular ISM is warm and dense: T~ 120 K, n~104 cm-3 • Heating this much gas is difficult: likely due to that X-rays from the starburst or the decay of micro-turbulence within clouds must dominate the heating. • These processes are powered by the starburst -> the starburst is self-regulating. Hailey-Dunsheath et al. in prep. • [CI] (2-1) line only 1000 km/s to the blue and always within ZEUS band.

  27. Starlight that contributes to  but not G [CII]/far-IR continuum luminosity ratio vs. density for various G (from Kaufman 1999). [CII]/far-IR Constrains Starburst Extent L[CIII] ~ 2.5  1010 L Lfar-IR ~ 3.2  1013 L 30% of [CII] from ionized medium R =5.5  10-4  G ~ 2000 far-IR = L/(4D2) = 14 DL~ 9.2 Gpc  = IR/(G 2) = 3.5 x 10-3  = beam = 0.083(”)2 d ~ 0.32”  2.75 kpc +3600 - 700 Galaxy-wide starburst supports the contention that hyper-luminous systems may be giant elliptical galaxies in formation (unlike local ULIRGs)

  28. Z-Spec channel spectral response Measured with long-path FTS (~100 MHz resolution) • Range: 185--305 GHz • Resolving power: 250--400 • (Not over sampled) • (750 < v < 1200 km/s) • Complete coverage from channel to channel -> no gaps

  29. Z-Spec Sensitivity Observed noise white with atmospheric 1/f Relative to an imaging system, fundamental noise levels are lower, but some systematic aspects are easier. Chopping -> response to a single frequency Narrow spectrometer bandwidth helps NEFsky ~  NEFGaussian noise ~ sqrt() Scaling consistent with e.g. Bolocam observations

  30. Z-Spec Sensitivity Clear scaling with , very close to photon background limit Blue -> achieved at =0, 0.1, 0.2 Black -> simple model for Z-Spec at CSO Det, amplifier, & internal load NEP: 6.4e-18 W/sqrt(Hz) (not tracking detector parameters in detail) measured instrument trans (~0.25) Aperture efficiency per taper + Ruze (60-70%) measured chop duty cycle (65%) photon noise from sky + telescope the most important term -> additional factor of 1.2 =0.2 500 =0 =0.1 300

  31. Z-Spec labor force James Aguirre -> U. Penn Jansky Fellow Colorado, NRAO Bret Naylor Recent Caltech Ph.D. Lieko Earle Colorado Ph.D. student (finishing Spring 08)

  32. ULIRG Survey Preliminary Results [ Line fluxes in Jy km/s, HCN / CO ratio corrected for to TMB ] Line fluxes SNR 4 - 20 Not finding overluminous HNC / HCN 3-2 ratio as per Aalto, Cernicharo. will follow-up further at CSO.

  33. Nearby Seyfert NGC 1068

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