Old Massive Galaxies in the Early Universe tell better Stories about Reionization

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Old Massive Galaxies in the Early Universe tell better Stories about Reionization. Nino Panagia (STScI, INAF, SN Ltd). Mostly based on work done in collaboration with: (in inverse alphabetical order ) Tommy Wiklind Massimo Stiavelli Bahram Mobasher Mike Fall Et Al. - PowerPoint PPT Presentation

Transcript of Old Massive Galaxies in the Early Universe tell better Stories about Reionization

  • Old Massive Galaxiesin the Early Universetell better Storiesabout ReionizationNino Panagia (STScI, INAF, SN Ltd)

    The End of the Dark Ages

  • Mostly based on work donein collaboration with: (in inverse alphabetical order)Tommy Wiklind Massimo StiavelliBahram Mobasher Mike Fall Et Al.

    The End of the Dark Ages

  • We know that the Universe is not quite ionized at redshift z=6.28Becker et al. (2001)

    The End of the Dark Ages

  • Becker et al (2001):The full story

    The End of the Dark Ages

  • The Principles of Reionization (RI) Reionization requires sources of Lyman continuum photons

    Reionization depends primarily on the UV output of the RI sources integrated over time

    Reionization is a function of the UV photon escape fraction, f, from the RI sources and the clumpiness of the IGM

    = f 1 B(z1,z2,C) Ly-c photonsHI mass =HIVolumeescapefractionphotons neededper ionization

    The End of the Dark Ages

  • The effect of the IGM clumping on Reionization[Stiavelli, Fall & Panagia 2004a]Clumping factor C = /2Effective number of photons to ionize an atom

    The End of the Dark Ages

  • Recognizing the Reionization Agents(Young Bright) Galaxies at z>6.5 are doing it

    (Evolved Massive) Galaxies at z

  • 32 30 28 26 24 32 30 28 26 24 mAB(rest=1400) Reionization constraints from HUDF observationsStiavelli, Fall & Panagia (2004b) T=100,000K (Z=0)T=50,000K (Z=Z/100)The blue line refers to UDF objects selected by i-z>2, the red one to i-z>1.3.The galaxies that may be ionizing NOW

    The End of the Dark Ages

  • HUDF-JD2, a Balmer Break Galaxy prototypeA galaxy that did it in the past?[Mobasher et al. 2005]

    z=2.5-3.4z = 6.5M = 61011 M Observed [m] 0.5 1 2 5 10Rest-frame [m] 0.1 0.2 0.4 0.8

    The End of the Dark Ages

  • Properties of HUDF-JD2[Mobasher et al 2005, Panagia et al 2005]Massive M/M = 6 1011

    Bright L/L = 1012

    Evolved Age > 350-650 Myr zform > 9

    Ionizing Q ~ 4 1072 Ly-c photons

    The End of the Dark Ages

  • HUDF-JD2:An Old Galaxy that did a LOTeff: Ratio of the time averaged Lyman continuumphoton flux to the present UV fluxAgeModel includingchemical evolution[Panagia et al 2005]

    The End of the Dark Ages

  • HUDF-JD2dereddenedcompanionsEnough to re-ionizeits region of Universe?By itself only if high escape fractionand low clumpingEasily if invisible companions with a reasonable LF are presentPanagia et al. 2005

    The End of the Dark Ages

  • HUDF-JD2: A summaryMassive, luminous, protypical Balmer-break galaxy

    It has had an important impact (>20%) on the reionization of the IGM starting a z~15

    With the help of fainter companions distributed according to an =1.6 Schechter LF it may account for the whole effect

    The End of the Dark Ages

  • Is HUDF-JD2 unique? Tommy Wiklind answered this question: not quite

    Actually, combining deep HST and Spitzer multi-band photometry one finds about one bright BBG per 10 square-arcmin field

    The End of the Dark Ages

  • BBGs in the GOODS Field South [Wiklind et al 2006, Panagia et al 2006] = 11.9 = 11.3

    = 72.2

    The End of the Dark Ages

  • Re-Ionization Balance - I UV output from BBGs in the Chandra Deep Field South Qtot = 4.2 1073 f Lyman-continuum photons

    H-atoms in a volume in the redshift interval 7-15

    NH = 1.2 1073 atoms

    If the detected BBGs are the only UV sources in the field

    B/f = 3.5

    The End of the Dark Ages

  • The effect of the IGM clumping on Reionization[Stiavelli, Fall & Panagia 2004a]Clumping factor C = /2Effective number of photons to ionize an atom

    The End of the Dark Ages

  • Re-Ionization Balance - II With a clumping C > 10 B > 2 f > 0.6 unlikely!?

    The IMF may be top-heavy too easy!!!

    Additional, fainter, undetected galaxies contribute to the reionization possible

    In this case, with C>10 and f

  • ConclusionsBig BangH IIz ~ 6-10 Dark AgesTIGM ~ 4z Kz ~ 103 z ~ recombinationtzH ITIGM ~ 104 Knormal galaxyS1Here Nowprimordial galaxyHubble Deep FieldHubble Ultra Deep Fieldend of reionizationJWSTHST

    The End of the Dark Ages

  • ConclusionsBalmer-Break Galaxies (BBG) are important for the reionization of the IGM starting at z~15 or higher

    With the help of fainter companions they have the potential of ionizing the IGM entirely

    JWST is needed to detect and study the population of reionizers

    The End of the Dark Ages

  • THE END

    The End of the Dark Ages

    This schematic drawing shows the development of the universe since the time of the Big Bang. The era of recombination, leading to the Cosmic Microwave Background, occurs at redshifts around 1000.The era of galaxy formation occurs between redshifts of about 20 (max) and 1, with the re-ionization of the universe occuring around z~6 as the number of hot, young stars becomes large enough to ionize the neutral gas.The Dark Ages occurred between the time of recombination (z=1000) and the time of re-ionization (z~6) and currently represents an interesting but unobserved phase of the evolution of structure in the universe.The Hubble Deep Field got us to a time when galaxy buildup was active but still not at the edge of the dark ages.The Hubble Ultra Deep Field should take us right up to the edge, to a time before starlight was kept the electrons and protons apart and the universe transparent. It should get us to the boundary of the dark ages.

    HST will be able to probe out to about z~6 with its instruments after SM4. With more powerful instruments, it could conceivably push even farther into the Dark Ages; otherwise, we will await JWST.