Windows to the Past: Using Gravitational Telescopes to Study our Cosmic Origins

Transcription

1 Windows to the Past: Using Gravitational Telescopes to Study our Cosmic Origins Austin Hoag University of California, Davis July 15, / 21

2 Collaborators Maru sa Brada c (PhD advisor; UCD), Tommaso Treu (UCLA), Kuang-Han Huang (UCD), Kasper Schmidt (AIP), Michele Trenti (Melbourne), Xin Wang (UCLA), Julie He (UCD), Tim Schrabback (Bonn), ASTRODEEP team (PI Adriano Fontana; INAF) 2 / 21

3 The Epoch of Reionization (EoR) Robertson+10 Phase transition from neutral to ionized hydrogen, marking the end of the Dark Ages after recombination Planck measures an average redshift of z = (Planck Collaboration XLVII 2016) Quasar spectra show evidence that reionization is complete by z 6 (e.g. Becker+01, Fan+06b) 3 / 21

4 Observations of the EoR With HST WFC3/IR, thousands of candidate z 7 galaxies have been found, e.g. BoRG, CANDLES, HFF (e.g. Finkelstein+15, Bouwens+15) Spectroscopic confirmation via Lyman-alpha successful for L L so far Evidence that L L galaxies primarily reionized the universe (e.g. Bouwens+15) Cluster lensing enables the identification and spectroscopic confirmation of L < L galaxies 4 / 21

5 Gravitational Telescopes Number Cluster α J2000 δ J2000 z Sample 1 Abell h14m21.2s -30d23m50.1s 0.31 HFF/GLASS 2 MACS h16m08.9s -24d04m28.7s 0.40 HFF/GLASS 3 MACSJ h17m d45m20.0s 0.55 HFF/GLASS/SURFS UP 4 MACSJ h49m34.3s +22d23m42.0s 0.54 HFF/GLASS/SURFS UP 5 RXCJ h48m44.4s -44d31m48.5s 0.35 HFF/GLASS 6 Abell h39m52.9s -01d34m36.5s 0.38 HFF/GLASS 7 RXJ h47m32.0s -11d45m42.0s 0.59 GLASS/SURFS UP 8 MACSJ h23m48.3s +24d04m47.0s 0.54 GLASS/SURFS UP 9 MACSJ h29m26.2s -07d42m26.2s 0.59 GLASS/SURFS UP 10 MACSJ h44m51.8s +39d27m33.0s 0.70 GLASS/SURFS UP 11 MACSJ h54m10.9s -03d01m07.0s 0.54 SURFS UP 12 MACSJ h14m57.4s -14d00m10.8s 0.30 SURFS UP 13 Bullet Cluster 06h58m27.4s -55d56m47.0s 0.30 SURFS UP 14 RCS h27m28.2s -02d04m25.0s 0.70 SURFS UP HFF = Hubble Frontier Fields Leading the effort to construct lens models for all 14 clusters with SWunitedAMR (Bradac+05,09) 10/14 (blue) have completed lens models, co-supervising undergraduates to complete remaining 4 clusters Interactive webtools to access the GLASS and SURFSUP lens models will be made publicly available, HFF already available: 5 / 21

6 Lens Modeling Model clusters using SWunitedAMR, a combined strong- and weak-lensing code developed by Bradac+05,09 χ 2 minimization on a non-uniform grid No light-traces-mass assumption or assumption of mass profile, in contrast to other popular cluster-scale lens-modeling codes (e.g. Lenstool, Zitrin-ltm, GLAFIC) 6 / 21

7 MACS AB mag 5σ limiting magnitude in 7 HST filters 194 candidate multiple images Collaborative effort by HFF modeling teams to vet images (CATS, Sharon, Zitrin, Williams, GLAFIC, Diego) Hoag+16 7 / 21

8 GLASS Spectroscopy (MACS0416) Spectroscopic redshifts paramount for modeling (Rodney+15a, Rodney+16, Treu and Rosati talks) At least 3 people inspected the GLASS spectroscopic data for emission lines coming from the multiple images confirmed 16 systems, 6 of which had no previous spectroscopic measurement. Example: Quadruply-imaged system, system 5 8 / 21

9 GLASS Spectroscopy (MACS0416) 5.1 (z grism = 2.09 ± 0.01) 9 / 21

10 GLASS Spectroscopy (MACS0416) 5.2: z spec = 2.10 ± / 21

11 MACS0416 Mass/light Comparison Significant variation in f throughout WFC3/IR FOV. 11 / 21

12 MACS0416 Mass/light Comparison Variation in f real up to M /kpc 2, uncertain above this mass limit. 12 / 21

13 Keck/MOSFIRE follow-up of GLASS targets Schmidt+16 identified 24 candidate Lyman-alpha emitters at z 7 in GLASS. Ongoing Keck/MOSFIRE and DEIMOS campaigns to confirm candidates with higher spectral resolution Keck/DEIMOS confirmations at z 7 (Huang+15,Huang+16) 13 / 21

14 GLASS z 8 LAE behind MACS1423 Magnified by µ 10 L 0.2L 14 / 21

15 GLASS z 8 LAE behind MACS1423 Thanks to: K. Huang. Redshift code: EAZY (Brammer+08) 15 / 21

16 GLASS z 8 LAE behind MACS1423 GLASS spectrum: MOSFIRE spectrum: 16 / 21

17 Conclusions GLASS spectroscopy has been paramount for focusing the Hubble Frontier Fields (HFF) and other clusters Light traces mass in MACS0416, A2744, and perhaps in other HFF clusters, is not necessarily a good assumption Extreme objects at the cosmic dawn are easier to confirm, but ordinary population is more important to understand EoR Cluster-scale lensing needed to study the more common L < L population Follow up programs have been successful 17 / 21