The Hubble Sphere Hydrogen Survey

Transcription

1 The Hubble Sphere Hydrogen Survey A 3D mapping of neutral hydrogen to study Dark Energy Ch.Yèche (CEA-Irfu/SPP, Saclay) on behalf of HSHS group XLIIIrd Rencontres de Moriond, Cosmology session, March 15th-22nd 2008, La Thuile Italy N5055

2 HSHS Concept 2

3 Baryonic Oscillations : 3D radio survey Principles Measurement of a standard ruler for different z 3D survey of galaxies in Universe Radio-detection up to z~ thanks to HI line HI dominant line below 1.4 GHz Survey parameters: 21cm HI line (1.4 GHz at z=0) Frequency Range: f = f 0 /(1+z) (0.0<z<1.5) GHz Sky coverage (1/2 sky ~ ) Volume: Gpc observed galaxies Standard spiral Galaxy at z=2 3

4 Intensity Mapping: Brightness Temperature Not necessary to detect individual galaxies but measurement of HI flux per pixel (see T.-C. Chang et al. arxiv: , accepted by PRL) Maximal pixel size Mpc to measure 150Mpc oscillations σ θ ~20 at z=1.5 Minimal size of the interferometer~ m At z=1.5 in such a pixel : Nb of galaxies with m>m* ~ 200 Total HI mass ~ M For each pixel measurement of the mean brightness temperature T b At z=1.5 T b ~ 300 µk T b ΔT Noise ~ 100µK x (T obs /20hours) -1/2 Transit telescope ~ 5-10mns/day System temperature T sys ~50K ΔT Noise Intensity mapping techniques favored by high z (w.r.t. galaxy z survey) 4

5 Overview of HSHS project Concept proposed by J. Peterson (CMU, Pittsburgh) and U.-L. Pen (CITA). First version with resolution sacrificed Dark energy oriented project A study Design for intensity mapping: A packed array interferometer: 100m x 100m 10 South-North static cylindrical reflectors with ~10mx100m Surface: from m 2 Focus in the East-West direction 128 x 8 antennas (dipoles) per cylinder 500 MHz ( 250 MHz wide windows) N S E W Currently many simulations to optimize this design If intensity mapping is promising next step, full HSHS (1km x 1km) 5

6 8 dipoles LNA Mixer ADC Evenly spaced dipoles 8 dipoles 8 dipoles X 128 LNA LNA X 128 Re Re Mixer Mixer Re Time FFT Cylinder 1 ADC ADC Im f Im f Im f Time FFT Time FFT Cylinder 2 f f f Digital correlator Transposition Grouping by column of frequency Transposition Grouping by column of frequency FFT in y Correlation along cylinder X 8 Cylinders FFT in y Correlation along cylinder NlogN instead of N 2 P P P P P sinδ/λ sinδ/λ sinδ/λ sinδ/λ sinδ/λ Classical Correlation in x between cylinders sinα/λ 6

7 What is new in HSHS approach? BAO with HI is not new (see SKA project) but in HSHS Galaxies are not resolved (HI flux measured in 10 x10 pixels) Low cost cylinders (mesh and cable) because they are static (transit telescope) Re-use technology developed for cell phones (Price of LNA ~ a few ) Digital correlator: FFT of the evenly spaced antennas along the cylinder direction (NlogN instead of N 2 ) Low cost for the packed array project: ~ 5-10 M. 7

8 Sensitivity on cosmological parameters P(k) Acoustic oscillations z=1.5 Power spectrum k (Mpc -1 ) For a Δz~0.2 slice of universe, we simulate 100 realizations Extract sensitivity on the angular distance D A (z) and H(z) Constraint on ratio w=p/ρ with w = w 0 + w a x z/(1+z) For HSHS project : σ(w 0 )~5% and σ(w a )~15% 8

9 Comparison with other BAO projects Same priors applied on the (h,ω m,ω b ) parameters AAOmega: z=~0.7 σ(k perp )/k perp : 1.8% σ(k par )/k par : 2.7% WFMOS: z=1.0 and 2.5 σ(k perp )/k perp : 1.0% and 1.5 % σ(k par )/k par : 1.2% and 1.8 % SDSS-III: z=0.35,0.6 and 2.5 (Lyman-α) σ(k perp )/k perp : 1.1%, 1.1% and 1.4 % σ(k par )/k par : 1.9%, 1.9% and 2.0 % HSHS: Better thanks to 1.0<z<1.5 Complementary with optical surveys 9

10 HSHS Collaboration Jeff Peterson (CMU) Kevin Bandura Bruce Taylor Derrick McKee Jim McGee Steve Schweiser Keewan Park Uros Seljak (U. C.Berkeley) Peter Timbie (U. Wisc.) Ue-Li Pen (CITA) Jean-Marc Le Goff (CEA-IRFU) Christophe Magneville Nathalie Palanque-Delabrouille Jim Rich Vanina Ruhlmann-Kleider Christophe Yèche Reza Ansari (IN2P3-LAL) Marc Moniez Bruce Bassett (SAAO) John Bunton (CSIRO) Kris Sigurdson (UBC) 10

11 HSHS Prototype 11

12 Overview of the prototype Goals Detection of the Galaxy and nearby galaxies Technical validation of the reflectors Validation of concept: multi-lobes reconstruction with early digitization (time and spatial FFT) Realistic estimate of the project cost Two cylinder prototype Carnegie Mellon University Prototype in Pittsburgh (CMU) 2 cylinders (25mx10m) Surface: 500 m 2 Angular resolution ~ 1 128x2 dipoles (beam forming: antennas grouped by 4). Study and construction of an electronics prototype by IN2P3-LAL (Orsay) and CEA-Irfu (Saclay) 12

13 Prototype in Pittsburg Dipole +LNA On PCB Ch. Yèche HSHS project Moriond-Cosmo, March 20,

14 Antenna board 4 dipoles 5 4 2nd 4.5 it/ s 5 ADC (500MHz) 4 channels 4 HSHS project Gb Spatial FFT (FPGA) X8 Clock distribution Ch. Yèche Time FFT FPGA Down conversion filtering 4. 4 Gb ADC (500 MHz) 4 channnels X4 128 dipoles X4 2nd PC s it/ Antenna board 4 dipoles Down conversion filtering X4 Electronics chain /s it Gb Time FFT FPGA Gb it/ s PC Moriond-Cosmo, March 20,

15 Test in Nançay radio-telescope Strategy Equipment of one of the two RT dipoles with our electronic chain directly in the focal carriage Observation in parallel with the other channel. Comparison with standard RT channel. focal carriage Two tests campaigns: Dec. 2007: Tests of the analog electronics and clock distribution system Spring 2008: Tests of the final ADC boards and PCIexpress board 15

16 Dec. 2008: First tests in Nançay Successful test of the analog boards Sampling of MHz with an homemade ADC (MATACQ) with a large dead time (not final version) 250 MHz Wide band NGC6822 V rad =-58km/s f (MHz) Extragalactic HI f (MHz) f (MHz) 16

17 Conclusions BAO with HI detection to study DE: Promising idea already proposed by SKA More ambitious with 3D intensity mapping HSHS : low cost project (BAO oriented) 5-10M Elegant concept but few cross-checks are required: Validation of the concept (early digitization and digital correlator) with prototype Estimates of reflectors and electronics costs First attempts to address the main issues: Electronics: Tests in Nançay and Pittsburgh (summer 2008) Beam forming-interferometry: Pittsburgh prototype (2009) HI power spectrum: with HIPASS catalog (arxiv: ) and test at NRT and GBT (2008) 17

18 Additional Slides 18

19 First detection of Cosmic Structure in the HI Intensity field (Ue-Li Pen et al., arxiv: ) HI intensity Survey: HIPASS data cube Not a galaxy catalog but an intensity map (pixel size ~ 0.5 h -1 Mpc) Cross-correlation Optical galaxy survey: 6dFGS survey galaxy redshifts in the region of overlap with HIPASS Results: Cross-correlation different from zero up to 3 h -1 Mpc First proof of HI mapping intensity approach Still not visible in HI auto correlation (systematics limited) 19

20 Photometric/spectro Redshift σ z /(1+z)=1% Factor 4 loss on FOM with photo-z assuming σ(z)/(1+z)~1% (very optimistic!!!) Best photo-z resolution expected are about 2-4% 20

21 Comparison for z<1.0 z<1.0 Loss of factor 3 on FOM for z<1.0 compared to z<1.5 21