The First Billion Year of History - Galaxies in the Early Universe. Stephen Wilkins, Silvio Lorenzoni, Joseph Caruana, Holly Elbert, Matt Jarvis

Transcription

1 The First Billion Year of History - Galaxies in the Early Universe Stephen Wilkins, Silvio Lorenzoni, Joseph Caruana, Holly Elbert, Matt Jarvis

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3 X recent z=8.3 GRB CCDs HST Keck Subaru

4 Picture credit: NASA

5 Subaru Telescope (NAOJ), sited on Hawai'i 8m telescope with wide field of view

6 Current narrow-band record now z=7.215 Shibuya et al. 2012

7 Neutral gas simulation at z~3, Theuns et al.

8 (Intergalactic Medium) "Lyman break technique" - sharp drop in flux at short (blue) wavelengths - hydrogen gas between us and the distant object absorbs light at the energy of electron transitions. Lower redshift, so shorter wavelength. A distant (high redshift) object should have no detectable emission at short wavelength

9 "Lyman break technique" - sharp drop in flux at λ below Ly-α. Steidel et al. have >1000 z~3 objects, "drop" in U-band. Pushing to higher redshift- Finding Lyman break galaxies at z~6 : using i-drops.

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11 Stanway, Bunker & McMahon (2003) Bunker et al. (2003) MNRAS Using HST/ACS GOODS data - CDFS & HDFN, 5 epochs B,v,i',z'

12 Picture credit: NASA

13 INITIAL EXCITEMENT orbits of HST with WFC3 in 3 near-ir filters on Hubble Ultra Deep Field. Galaxies at z=7-9! Data first taken in August-Sept papers immediately (Bouwens et al., Bunker et al., McLure et al., Oesch et al.) and >10 more since. Large HST surveys Illingworth UDF ; WFC3 ERS team O Connell ; CANDELS; HUDF12

14 Hubble Ultra-Deep Field 2009 (HUDF09)

15 Subaru Telescope (NAOJ), sited on Hawai'i 8m telescope with wide field of view

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18 Discovering a Star- Forming Galaxy less than 1 billion years after the Big Bang Bunker, Stanway, Ellis, McMahon & McCarthy (2003) Keck/DEIMOS spectral follow-up & confirmation z=5.8 Hubble Space Telescope image - red candidate Elizabeth Stanway, Andrew Bunker, Richard McMahon 2003 (MNRAS)

19 Now pushing spectroscopy to z~7-8; mostly upper limits Caruana et al. (2012)

20 Redshift z After era probed by the microwave background, Universe enters the so-called dark ages prior to formation of first stars Hydrogen atoms are then reionized by UV light from the newly-formed stars 1100 DARK AGES When did this happen? What did it? 0

21 Brightest HUDF Y-drop Found in Sept 2009: YD3 in Bunker et al UDFy in Bouwens et al.; #1721 in McLure et al. In late 2009, Nature paper Lehnert et al. claiming spectroscopic confirmation of Ly-alpha at z=8.55 with SINFONI-IFU on VLT

22 No evidence of Ly-alpha at z=8.55 in 5-hour VLT/XSHOOTER And 11-hour Subaru/MOIRCS spectrum. Also, the deep HST/WFC3 Y-band encompasses Ly-alpha, should be detected at ~4sigma but is undetected Bunker et al. (2013, MNRAS 430, 3314)

23 Emission lines Star formation rates, metallicity (oxygen, R 23 ), dust extinction (Hα/Hβ), line widths/rot curves kinematics/masses

24 Near-infrared spectroscopy to detect the emission lines from metals at high redshift hard previously restricted to individual objects. FMOS spectrograph on Subaru changes that 400 at once. Built by University of Kyoto and University of Oxford Worked on data from this at Kyoto University & Tokyo (NAOJ & IPMU) under a JSPS short-term invitation fellowship programme

25 Spectra with FMOS on 8-m Subaru To measure star formation rates and metal enrichment when the Universe was ~30% its current age Evolution of Star-formation & Metallicity in the Universe at high Reshift with FMOS evol SMURF

26 Press release yesterday results from FMOS, Silverman, IPMU (Zahid et al., Kashino et al.)

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28 What Can we Learn about High-redshift Galaxies: star formation rate density cosmic star formation history The (mostly) UV inferred Cosmic Star Formation History

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30 Wilkins et al. (2010) MNRAS The Luminosity Function at z~7 An increasing problem for reionization: requires steep faint-end slope (α<-1.7), large contribution from unobserved faint galaxies, high escape fraction (f esc >0.5) and very smooth IGM (low clumping, C~5)

31 The Key Problem! We know the intergalactic medium of the Universe reionizes at z>6 (probably around z=10-11)! What is the source of the UV photons to do this?! AGN are under-abundant at these high redshifts! Can star formation do it? Or is it something else?! Have been successful in recent years in finding starforming galaxies at z=6 and beyond! Insufficient photon density from the high redshift luminous galaxies we have found so far! Is it the unobserved faint end of the luminosity function?

32 Picture credits: NASA

33 ESA Contributions to JWST NIRSpec ESA Provided Detector & MEMS Arrays from NASA MIRI Optics Module ESA Member State Consortium Detector & Cooler/ Cryostat from NASA Ariane V Launcher

34 James Webb Space Telescope

35 Goddard Space Flight Centre Northrop Grumman Operations:STScI Project Scientist: John Mather

36 Future Prospects Subaru HSC+PFS Find the brighter but rarer Lyman break galaxies at z>6 which are amenable to continuum spectroscopy Also: ALMA for Molecules and dust, In future SPICA

37 Conclusions Exciting time in astrophysics have used Hubble Space Telescope and wide-field ground based images (e.g. Subaru) to identify galaxies in the first billion years after the Big Bang Still unclear if there are sufficient galaxies detected to reionize the intergalactic medium at very high redshifts Spectroscopy moving into new era with multiobject and wide-field capability (Subaru FMOS & PFS) ALMA might get redshifts even if the Lyman-