1Surface of Last Scattering (CMB)z = 1100Re-ionizationz ~ 11- 7Z = 1089Age of U.(Gyr)0.000180.180.481.20 2.19 3.345.935.93When did galaxy formation occur?How did galaxy formation occur?CDM bottom upsmaller larger[CO Table 30.3]ionizedionizedneutralz = 7 galaxy?Gravitationally lensed galaxy observed at Keck by Ellis et al.Ly 1215 break?2Z ~ 10 galaxies?Grav. lensingcritical curvesKeck NIRSPEC slit positionsExpected (rest frame) spectrumHST broadband images show no continuum emission.INFRAREDSPECTA6 possible Lyemission lines (circled)z ~ 8.5 – 10.42 best bets are z ~ 10 912ALyman breakWavelength z = 8.1 Gamma Ray Burst• Detected with Swift satellite.• Core collapse supernova (massive star) – beamed jet.• Follow up infrared spectrum with 3.6m telescope shows underlyinggalaxy.• Universe 640 million yrs old.Salvaterra et al. 2009, Nature, 461, 1258Atmospheric transmissionNear-IR spectrum1216A Lyman break3The Hubble Deep FieldNorthern field:• 10 days, 150 orbits– WFPC2 camera– 5.3 arcmin2• 5000 objects– 20 stars– rest are galaxiesSouthern field:• 70 hours•QSO in centerPhotometric RedshiftszSpec= 1.355zSpec= 0.089zSpec= 0.475www.ifa.hawaii.edu/~cowie/tts/tts.html• Pioneered by Loh & Spillar 1986• Used with HDF and most deep surveys since.• Reasonable redshift accuracy. • Reasonable ability to classify galaxies.• Only need a few broad-band images, not spectra.4Hubble Ultra Deep Field Advanced Camera for Surveys• 3 x 3 arcmin2• 11.3 days exposure.NICMOS• 2.4 x 2.4 arcmin2• 4.5 days exposure+ many other surveys… GOODS, Chandra, etcBasic idea behind galaxy formation -objects start small and grow by mergingAbraham & van den Bergh (2001)Do galaxiesform this way? Does star formationoccur before,during or aftermass assembly?When and howdo Hubble Types form?5Star formation rate as a function of timeMeasured from• Blue light (O star continuum)•H emission (H II regions)“Madau diagram”Star Formation Rate Density Hopkins & Beacom2006, ApJ, 651, 1425.9 3.3 2.2 1.6 0.8 Gyr since Big BangFrom the HST PR dept:TimeEach box is same size in proper distance
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