HI Intensity Mapping and Prospects for Detection with GMRT at z 1

Transcription

1 HI Intensity Mapping and Prospects for Detection with GMRT at z 1 Nishikanta Khandai NISER, Bhubaneswar National Workshop on Cosmology with the HI 21cm line, RRI, With: Shiv Sethi, Tiziana Di Matteo, Rupert Croft

2 Outline Introduction Modeling the HI distribution Detecting HI at z 1 in the DEEP2 field Constraints on the HI Mass Function with GMRT Tentative Detection with GMRT

3 Introduction Evolution of Neutral Hydrogen (HI) Ali & Bharadwaj 2005

4 Introduction Evolution of Neutral Hydrogen (HI) Ali & Bharadwaj 2005 Putman et al. 2009

5 Post-reionisation, a tiny fraction of neutral hydrogen (HI) survives ionization and is locked in dense clumps through self-shielding : DLA, LLS. The neutral fraction has remained consistent with a constant value of Ω HI O(10 3 ) z > 1 with large errors. SFR has been determined out to redshift 3 4, however measurements of cold gas in galaxies have been made out to only z = (Lah et. al 2009) A census of cold gas is crucial for galaxy formation models at moderate redshifts. Clustering properties of HI selected galaxies (HI bias, mass function), will give key insights into the clustering of their host halos.

6 We focus in the post-reionization era and make predictions for the distribution of HI in this regime, using the 21cm hyperfine transition of HI as a probe. T s T CMB at these redshifts hence the signal will be seen in emission. Direct detection for individual objects with an existing radio interferometer (GMRT) is not feasible. Noise is too large, flux is diluted at higher redshift. Strategy for direct detection: Stack the signal with known estimates of galaxy redshift from another survey: DEEP2. Independent constraint on Ω HI

7 Modeling the HI Distribution Simulation of DLAs at z=3 Bimodality at M Suppression in HI at M > M M halo also host the most significant HI. Pontzen et al 2008 ( ) 3 M vir M vcirc ( 1+zc ) 3/2 60km/s 4 V min circ 30km/s V max circ 200km/s

8 Observations: HIPASS galaxies at z = 0 (Zwaan et al. 2005) ( ) 0.37 ( ) dn dlnm = MHI M exp M HI HI MHI M HI = M Shift due to larger Ω HI (z = 1) Power et al 2010 Finite resolution: Mismatch at low masses

9 Simulation Details Gadget3: Dark Matter Simulation N part = , L box = 400h 1 Mpc, 1.5 larger than Millenium. Cosmology: σ 8 = 0.8, n s = 0.96, Ω Λ = 0.74, Ω m = 0.26 P(k) Eisenstein and Hu. Halofinder: SUBFIND with 20 bound particles. Mass resolution: M DM = M, 3 times finer than Millenium. Large volume will probe effects of cosmic variance on Ω HI

10 M HI (M halo ) m ) Mhalo n ( ) Mhalo p 1+( M + M min max Model 1: Fits Zwaan mass function but normalised to Ω HI = Model 2: HI suppression in low mass halos. Model 3: HI suppression in high mass halos. Table: Model Parameters Model M min (10 10 M ) M max (10 10 M ) m n p

11 Cosmic Variance

12 Neutral Fraction

13 Color code: HI fraction fhi

14 Observation time (statistical and direct) too large. Individual detection: no constraints on Ω HI Signal O(10µJy), Noise O(100µJy mjy) Beat noise by stacking sources, with independant redshift estimate.

15 Survey Considerations DEEP2 4 fields, each 120 by 30, comoving volume (h 1 Mpc) 3 Spectra of galaxies in redshift: GMRT Redshift Window: Noise for 24hr integration in 128KHz channel: Optimistic Case: 71µJy Conservative Case: 420µJy Simulation Volume Overlapping Volume: (h 1 Mpc) 3 Quarter of DEEP2 volume.

16 Detection of HI in the DEEP2 field with GBT Figure: Chang et al. 2013

17 Detection of HI in the DEEP2 field with GBT

18 Clustering of HI in the DEEP2 field with the GBT ξ HI,opt (r z ) = T b (d + r z )δ opt (d) ( ) ( ) ΩHI h = 284µK δ HI (d + r z )δ opt (d) ( Ωm + (1 + z) 3 ) 0.5 ( ) Ω Λ 1 + z 0.5. (1) δ HI = brδ opt b = δ 2 HI 1/2 / δ 2 opt 1/2 r = δ HI δ opt / ( δ 2 HI δ2 opt ) 1/2 Chang: brω HI = (5.5 ± 1.5) 10 4 Constraints from simulations: Ω HI = (1.03 ± 0.28, 0.95 ± 0.26, 1.12 ± 0.30) 10 3.

19 Detection of HI in the DEEP2 field with the GMRT Figure: Khandai et al. 2011

20 Tentative GMRT Detection in the DEEP2 field Figure: Sethi et al. 2013

21 Tentative GMRT Detection in the DEEP2 field Figure: Sethi et al. 2013

22 Detection Significance Errors Model 1 Model 2 Model 3 σ cosm (M > M 11.4 ) 8.63% 9.30% 8.59% σ cosm (M > M 12.0 ) 10.85% 11.43% 10.87% σ cosm (M > M 12.5 ) 13.56% 14.10% 13.58% σ rms = 71µJy σ MHI (M > M 11.4 ) 6.47% 5.23% 9.37% σ MHI (M > M 12.0 ) 8.55% 5.91% 12.11% σ MHI (M > M 12.5 ) 11.41% 6.87% 15.34% σ rms = 420µJy σ MHI (M > M 11.4 ) 42.23% 34.81% 60.04% σ MHI (M > M 12.0 ) 40.18% 29.82% 53.62% σ MHI (M > M 12.5 ) % 52.05% %