21cm	  cosmology	                 Ue-­‐Li	  Pen	   K.	  Masui,	  E.	  Switzer,	  R.	  Shaw,	  L.	  Cailin,	    G.	  Paciga...
Overview	  21cm	  physics	  Theory:	  dark	  energy,	  gravity	  waves,	  neutrinos,	    enhanced	  21cm	  pre-­‐reionizaT...
21cm:	  HI	  hyperfine	  transiTon	  •  Hyperfine	  transiTon	  when	  electron	  and	     proton	  spins	  flip:	  change	  ...
ApplicaTons                            	  Hydrogen	  Maser	  Clock	  Milky	  way	  mapping	  Nearby	  redshif	  surveys	  ...
21cm sky at z=0      Kalberla et al 2005, from WMAP LAMBDA
Image courtesy ofNRAO/AUI andChung et al.,ColumbiaUniversity
Atomic	  physics	  -­‐-­‐	  energy	  splihng=0.068K<<TCMB.	  -­‐-­‐	  Emission/absorpTon	  depends	  on	  spin	  temperatu...
21cm:	  emission	  δ Tb=τ TS = const
Spin	  evoluTon	           Furlanetto Oh & Briggs, 2006
21cm:	  observaTons	  •  Hydrogen	  is	  the	  most	  abundant	  element	  in	     the	  universe	  •  21cm	  line	  opTca...
21cm:	  observaTonal	  challenges	  •  Inverse	  square	  law:	  required	  collecTng	  area	     proporTonal	  to	  dista...
Technical	  challenges	  •  SensiTvity:	  bigger	  telescopes?	  •  Foreground	  contaminaTon:	  design/analysis?	  •  Tar...
The	  21	  cm	  universe	  •  Cosmological	  LSS	     treasure	  trove	  (UP04,	     Loeb&Zaldarriaga	  04,	     Lewis&Cha...
Fundamental	  Physics                                   	  •  0<z<2:	  dark	  energy,	  BAO,	  w-­‐w	  •  z>2:	  Large	  a...
Intensity	  Mapping	  •  Stars	  get	  fainter	  with	  distance:	  hard	  to	  see	     individually	  at	  cosmological	...
From: talk by O. Lahav
Foreground:	  GalacTc	  Synchrotron	  Haslam 408 MHz Much brighter than signal, but no spectral structure
Robert	  C	  Byrd	  Telescope:	  100m	  
HI	  content	  at	  z=0.8	  Cross-­‐correlaTng	  GBT	  HI	  &	  DEEP2	  opTcal	  galaxies	  at	  	            z	  ~	  0.7-...
•     Measure HI &                                               optical cross-                                           ...
GBT 15h auto power
IniTal	  Intensity	  Mapping	  •  Detected	  collecTve	  large	  scale	  structure	  with	     100h	  of	  GBT	  Tme:	  fir...
Baryon	  AcousTc	  OscillaTons	  –	  Dark	                  Energy	  Probe	  •  CMB	  acousTc	     oscillaTons:	     impri...
Present	  LSS	  BAO	  DetecTons	                                                     2007	                                ...
Blake et al 2011: WiggleZ, z~0.6   Masui et al: GBT-BAO                                   proposal 2012, z~1
Dedicated	  Survey	  Experiment	  •  Low	  frequency	  technology	  cheap,	  modest	  size:	     (100	  m)2	  to	  z<2	  •...
Darwin	         AUSTRALIA	                Brisbane	   Perth	                    Sydney	                  Melbourne	  +	   ...
CMU	  cylinder	  in	  operaTon:	  	  J.	  Peterson,	  U.	  Pen,	  U.	  Seljak,	  K.	  Bandura,	  K.	  Sigurdson	  
Fast Fourier Transform TelescopeCHIME, Tianlai, CRT, etc
New	  Cylinder	  Radio	  Telescopes                                         	  Canada,	  US,	  China,	  France,	  Morocco	...
Gravity	  Waves                                        	  •    Masui	  &	  Pen	  2010	  	  (PRL	  105,	  161302)	  •    An...
Linear	  gravity	  wave	  memory	  •  GW	  in	  iniTal	  condiTon,	  then	  redshifs	  away	  
Detectability	  
Conclusions	  •  21cm	  cosmology:	  probes	  of	  dark	  energy	  (BAO),	     modified	  gravity	  (lensing),	  InflaTon	  ...
Ue-Li Pen - 21cm Cosmology
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Ue-Li Pen - 21cm Cosmology

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Ue-Li Pen - 21cm Cosmology

  1. 1. 21cm  cosmology   Ue-­‐Li  Pen   K.  Masui,  E.  Switzer,  R.  Shaw,  L.  Cailin,   G.  Paciga,  K.  Bandura,  J.  Peterson,  T.  Chang,  Y.  Liao,  X.  Chen,  Y.  Li,  T.  Voytek,   A.  Natarajan,  M.  Dobbs,  M.  Halpern,  J.R.  Bond,  G.  Hinshaw,  J.  Roy,  Y.  Gupta,   R.  Nityananda,  and  many  more  
  2. 2. Overview  21cm  physics  Theory:  dark  energy,  gravity  waves,  neutrinos,   enhanced  21cm  pre-­‐reionizaTon  structures.  ObservaTons:  first  detecTons  and  upper  bounds   (GBT,  GMRT)  Future:  dedicated  surveys  (CRT,  CHIME,  etc  )  
  3. 3. 21cm:  HI  hyperfine  transiTon  •  Hyperfine  transiTon  when  electron  and   proton  spins  flip:  change  in  magneTc  moment  •  h  ν  =α4  me  c2  (me/mp)    •  ν=1420.40575  MHz  •  Highly  forbidden,  lifeTme  t~107  years  •  Astronomical  Tme  scales  T>>t  
  4. 4. ApplicaTons  Hydrogen  Maser  Clock  Milky  way  mapping  Nearby  redshif  surveys  (HIPASS,  ALFALFA)  Cosmological  redshif  surveys  (GBT,  CHIME/CRT/ Tianlai)  High  redshif  universe  (GMRT/LOFAR/MWA/ PAPER)      
  5. 5. 21cm sky at z=0 Kalberla et al 2005, from WMAP LAMBDA
  6. 6. Image courtesy ofNRAO/AUI andChung et al.,ColumbiaUniversity
  7. 7. Atomic  physics  -­‐-­‐  energy  splihng=0.068K<<TCMB.  -­‐-­‐  Emission/absorpTon  depends  on  spin  temperature  TS  -­‐-­‐  Typically  collisionally/uv  excited.  -­‐-­‐  for  TS  >>  TCMB,  emissivity  independent  of  TS:  measure  hydrogen  (HI)  mass  robustly.  
  8. 8. 21cm:  emission  δ Tb=τ TS = const
  9. 9. Spin  evoluTon   Furlanetto Oh & Briggs, 2006
  10. 10. 21cm:  observaTons  •  Hydrogen  is  the  most  abundant  element  in   the  universe  •  21cm  line  opTcally  thin  from  the  ground  over   most  lines  of  sight  to  very  high  z  (~100)  
  11. 11. 21cm:  observaTonal  challenges  •  Inverse  square  law:  required  collecTng  area   proporTonal  to  distance2.  •  Highest  redshif  direct  galaxy  detecTons  at   z~0.2  using  2000  hours  of  WSRT  (5000m2)  •  For  cosmological  interests  (1<z<100)    and   wide  sky  maps  needs  km2  array:  SKA  
  12. 12. Technical  challenges  •  SensiTvity:  bigger  telescopes?  •  Foreground  contaminaTon:  design/analysis?  •  Target:  Galaxies,  Intensity  Mapping/BAO,   EoR?  
  13. 13. The  21  cm  universe  •  Cosmological  LSS   treasure  trove  (UP04,   Loeb&Zaldarriaga  04,   Lewis&Challinor  07,   EoR: etc)   GMRT/•  Up  to  1018  modes:     LOFAR (Jeans/Hubble)3   CHIME/ GBT MWA•  Physics:  Lensing,   gravity  waves,   Paper primordial  NG,  BAO,   SDSS AP  •  GW  to  r  ~  10-­‐8  •   fNL~  10-­‐4  •  Astrophysics:  EoR,   galaxy  evoluTon  •  Experiments  NOW   Tegmark &
  14. 14. Fundamental  Physics  •  0<z<2:  dark  energy,  BAO,  w-­‐w  •  z>2:  Large  angle  lensing:  modified  gravity  (Lu   &  UP  2009,  Masui  et  al  2010)  •  z>10:  gravitaTonal  waves  
  15. 15. Intensity  Mapping  •  Stars  get  fainter  with  distance:  hard  to  see   individually  at  cosmological  distance.    Galaxies   sTll  visible.  •  Galaxies  get  fainter  with  distance:  hard  to  see   in  HI.    Large  scale  structure  sTll  visible?  •  Large  scale  structure  is  LARGE:  degree  scale.     High  resoluTon  not  needed.  •  Modest  size,  monolithic  radio  telescopes   needed.    (CPPM  2008,  Wyithe&Loeb  2008)  
  16. 16. From: talk by O. Lahav
  17. 17. Foreground:  GalacTc  Synchrotron  Haslam 408 MHz Much brighter than signal, but no spectral structure
  18. 18. Robert  C  Byrd  Telescope:  100m  
  19. 19. HI  content  at  z=0.8  Cross-­‐correlaTng  GBT  HI  &  DEEP2  opTcal  galaxies  at     z  ~  0.7-­‐1.1  (Chang  et  al,  Nature  2010)   GBT radio continuum sources + HI GBT HI DEEP2 density
  20. 20. •  Measure HI & optical cross- correlation on 9 Mpc (spatial) x 2 Mpc (redshift) comoving scales •  HI brightness temperature on these scales at z=0.8: •  •  Highest-redshift detection of HI in emission at 4-Chang, Pen, Bandura, Peterson, Nature, sigma statistical 2010 significance.
  21. 21. GBT 15h auto power
  22. 22. IniTal  Intensity  Mapping  •  Detected  collecTve  large  scale  structure  with   100h  of  GBT  Tme:  first  demonstraTon  of   distant  IM.    No  individual  galaxies  detected,   many  galaxies  per  resoluTon  element  •  Proposal  submited  for  z=1  BAO  survey  on  4   pixel  array  at  GBT  
  23. 23. Baryon  AcousTc  OscillaTons  –  Dark   Energy  Probe  •  CMB  acousTc   oscillaTons:   imprinted   standard  ruler,   100  Mpc.  •  Present  in   current  mater   distribuTon  •  KinemaTc  metric   WMAP5  and  other,  Nolta  et  al   of  universe   (2008)  
  24. 24. Present  LSS  BAO  DetecTons   2007   Percival  et  al   2005   Eisenstein  et  al   •  Percival  et  al  2007  
  25. 25. Blake et al 2011: WiggleZ, z~0.6 Masui et al: GBT-BAO proposal 2012, z~1
  26. 26. Dedicated  Survey  Experiment  •  Low  frequency  technology  cheap,  modest  size:   (100  m)2  to  z<2  •  Large  field  of  view:  receiver  arrays  •  High  surface  brightness  sensiTvity:  compact   arrays  •  Stable,  reliable:  no  moving  parts  •  Technologies:  aperture  arrays  (Wyithe,  Loeb,   Geil  2008),  cylinders  (Peterson  et  al)  
  27. 27. Darwin   AUSTRALIA   Brisbane   Perth   Sydney   Melbourne  +   Adelaide  Canberra   Molonglo   Hobart   Northern   Cross  Molonglo  Ooty Cambridge   Pushchino
  28. 28. CMU  cylinder  in  operaTon:    J.  Peterson,  U.  Pen,  U.  Seljak,  K.  Bandura,  K.  Sigurdson  
  29. 29. Fast Fourier Transform TelescopeCHIME, Tianlai, CRT, etc
  30. 30. New  Cylinder  Radio  Telescopes  Canada,  US,  China,  France,  Morocco  Map  the  Hubble  volume  to  0.8<z<2.5  Most  sensiTve  BAO,  RSD,  lensing  survey  Ancillary  science:  21cm  absorbers,  radio   transients,  pulsar  search/monitoring,   magneTc  fields  Scalable  to  z~20:  tens  of  square  kilometers    
  31. 31. Gravity  Waves  •  Masui  &  Pen  2010    (PRL  105,  161302)  •  Analogous  to  lensing:  shearing  of  cosmic  structure.  •  Fossil  memory  effect:  h~10-­‐6  (inflaTon)  •  Measure  r,nT  at  z~15  •  Requires  1/h2  modes  •  Separates  from  lensing:  transverse  traceless  •  Structures  available  to  k~10-­‐3-­‐103:horizon  to  Jeans   scale,  ~1018  modes,  peaks  at  z~15  
  32. 32. Linear  gravity  wave  memory  •  GW  in  iniTal  condiTon,  then  redshifs  away  
  33. 33. Detectability  
  34. 34. Conclusions  •  21cm  cosmology:  probes  of  dark  energy  (BAO),   modified  gravity  (lensing),  InflaTon  (tensor  modes),   etc.    Beyond  intrinsic  power  spectrum.  PotenTal   measure  of  gravity  waves.  •  Intensity  Mapping:  21cm  unresolved  galaxies,   accessible  in  redshif  desert  z=1-­‐3,  iniTal  HI  detecTon   and  surveys  with  GBT  at  z~1.    Upper  bounds  at  z=9.  •  Prototypes  and  observaTons  under  way.    Cylinder   telescopes  a  promising  technology  for  fast,  large,   economic  surveys.    OpTmal  calibraTon  and  dynamic   range.  

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