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    Downsizing & Galaxy Formation

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    axlzeke
    Galaxy formation theory generically favors formation of small galaxies before larger ones, and tends generically to overproduce early star formation. Observations unambiguously favor downsizing for both galaxies and for SMBH. ... At lower and higher masses, the star formation is substantially less efficient.

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    Downsizing & Galaxy Formation

    Uploaded by

    axlzeke
    22 views49 pages
    Galaxy formation theory generically favors formation of small galaxies before larger ones, and tends generically to overproduce early star formation. Observations unambiguously favor downsizing for both galaxies and for SMBH. ... At lower and higher masses, the star formation is substantially less efficient.

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    Galaxy formation theory generically favors formation of small galaxies before larger ones, and tends generically to overproduce early star formation. Observations unambiguously favor downsizing for both galaxies and for SMBH. ... At lower and higher masses, the star formation is substantially less efficient.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    22 views49 pages

    Downsizing & Galaxy Formation

    Uploaded by

    axlzeke
    Galaxy formation theory generically favors formation of small galaxies before larger ones, and tends generically to overproduce early star formation. Observations unambiguously favor downsizing for both galaxies and for SMBH. ... At lower and higher masses, the star formation is substantially less efficient.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 49

    Downsizing

    & Galaxy
    Formation
    P. McCarthy
    OCIW

    Gemini Deep
    Deep Survey
    2nd Mitchell Symposium - April 2006 Team
    How are Galaxies Formed?

    Monolithic Collapse Hierarchical


    ala ELS Assembly
    The Hierarchical Merger Tree

    -----------------Z = 3

    --------------- Z = 1

    ------------- Z=0
    Two Kinds of Galaxies

    -------------------------------
    Red
    Massive-Passive

    Light-Active
    Blue

    3 x 1010Msun

    Kauffmann et al 2003
    Star Formation History
    Mass Assembly History
    Gemini Deep Deep Survey
    Gemini GMOS spectrograph

    GMOS
    LRIS
    LDSS1
    30 hour exposures - 300+ redshifts
    I (Vega) ~ 24.5 1<z<2
    Abraham, Glazebrook, PMcC, et al.
    Stellar Mass Determinations
    100,000 Model Spectral Energy Distributions
    f(Age, SF history,abundance, reddening)
    +
    Observed Spectral Energy Distributions, Redshifts

    χ 2 Best-fit Template, range of templates

    Best-fit M/L, range X MK


    = Mstar, range
    The Most Massive Galaxies

    Glazebrook et al.
    Mass Downsizing

    L. Cowie 1996
    Three Views of Downsizing

    • Stellar Mass Density Evolution


    • Star Formation Histories by Mass
    • Early Assembly of Massive Galaxies
    Stellar Mass Density

    Cosmic Stellar mass density has not


    evolved at the high-mass end since z ~ 2
    The Evolving Stellar Mass Density
    New, improved semi-analytic models
    Star Formation Histories by Mass

    Massive Galaxies ceased star formation


    at z > 2, low mass galaxies continued
    active star formation to late epochs
    Star Formation Histories
    Juneau et al.
    Mass Downsizing
    Post Starburst Galaxies

    50% Post-Star Burst


    Only 1 in @ z ~ 1.5
    10,000
    galaxies
    in LCRS
    have
    similar
    EWs
    Early Assembly of Massive Galaxies

    10% of today’s stellar mass was assembled into


    massive galaxies at z > 3,
    and 5% before z ~ 4.
    The Most Massive Galaxies

    ~ 20% z = 0
    mass density

    Glazebrook et al.
    Spectral Types at z > 1.3
    Star Forming

    Pure Passive
    Old Galaxies at 1.3 < z < 1.8

    <z>=1.3
    Old Galaxies at 1.3 < z < 1.8

    <z>=1.3
    <z>=1.8
    Old Galaxies at 1.3 < z < 1.8

    <z>=1.3
    <z>=1.8

    <z>=0.3
    Old Galaxies at 1.3 < z < 1.8

    <z>=1.3
    <z>=1.8
    2Gyr
    Pegase Model
    Old Galaxies at 1.3 < z < 1.8
    Age Fitting of 20
    individual Galaxies
    1.3 < z < 2.0

    <zf> ~ 2.5
    [Fe/H] > 0
    E(B-V) ~ 1

    <zf> ~ 4
    [Fe/H] = 0
    Star Forming Galaxies 1.3 < z < 2.0

    ACS F814W
    Pure Passive Systems

    ACS
    F814W
    NICMOS
    F160W

    75-80%
    Spheroids
    Surface Brightness Profiles
    Z = 1.84

    0.3 < Re< 1′′

    Z = 1.32
    Size Distribution

    Little or no
    evolution
    in the size
    distribution
    Kormendy Relation at 1.3 < z < 2

    Rest Frame

    V-Band
    Kormendy
    Diagram
    Kormendy Relation at 1.3 < z < 2

    Passive
    Evolution
    ~1 mag per
    unit redshift
    “Old” Galaxies at z ~ 6

    ~ 1/2 M* @ z ~ 10!

    Eyles et al. 2005


    10 M*!

    Mobasher et al. 2005


    Basics ``Up-Sizing′′
    Giant Magellan Telescope
    24m Aperture
    18′ x 18′ VMOS
    7′ x 7′ NIRMOS
    Conclusions

    • Galaxy Formation Proceeds from high to low


    masses
    • Some of today’s massive galaxies formed
    quite early
    • Good prospects for JWST and ELTs
    Wider or Deeper Surveys?
    Wider
    IMACS on the
    6.5m Baade
    Telescope

    27′ Diameter
    field of view
    350-500 slits per mask
    R ~ 1000

    Nod & Shuffle sky subtraction


    Spectral Evolution
    Spectral
    Classes
    Passive
    Intermediate
    Composite
    Young
    Emission Absorption

    Z = 0.1

    M > 3 x 1010 Msun

    Le Borgne et al.
    Emission Absorption

    Z = 1.2

    M > 3 x 1010 Msun

    Le Borgne et al.
    Hδ Strong Fraction Post-Starburst Galaxies

    M > 3 x 1010 Msun

    50% of massive galaxies are post-starburst


    Systems at z ~ 1 !
    Massive Post Starburst Galaxies

    Intermediate Mass Galaxies had their star


    formation truncated at z ~ 1.5
    CIRSI + LCO Wide Field IR Camera

    du Pont 2.5m telescope


    4 1024 x 1024 arrays
    cryogenic Offner relay
    16 channel electronics Persson, Murphy, Birk
    Post-Starburst Galaxies

    50% Post-Star Burst


    Le Borgne et al.

    @ z ~ 1.5

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