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Investigators have produced UV-NIR images of a faint galaxy

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Investigators have produced UV-NIR images of a faint galaxy. ... Nature of objects contributing to the faint blue galaxy counts unknown ... – PowerPoint PPT presentation

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Title: Investigators have produced UV-NIR images of a faint galaxy


1
A Window on Cosmic Birth
  • Exploring our Origins with the SIRTF and NGST
    Space Missions
  • Judith L. Pipher
  • University of Rochester

2
Searching for Origins
  • How did galaxies form in the early universe?
  • How were galaxies different at early times?
  • When did galaxies first appear?
  • How do galaxies evolve?
  • Do galaxy collisions play a role?
  • What are galaxy luminosity sources? As evolve?
  • How and when do stars (and planets) form?

3
Big Themes Big Space Experiments - IR
  • SIRTF -
    Space InfraRed Telescope Facility
  • cold, 0.85-m telescope 7/02 launch
  • cameras 3 - 8 mm spectrometers
    5 - 40 mm photometers 24, 70,
    160 mm lo-res spectrometer
    52-99 mm
  • NGST - Next Generation Space Telescope
  • cold, 8-m telescope, planned for /08 launch
  • successor to the Hubble Space Telescope

4
Why Infrared - IR?
  • Cool objects radiate in the infrared
  • lmax ? T-1 Wiens blackbody law
    (e.g. T100K, lmax 30 mm
    30,000 nm)
  • Dusty clouds ( stellar nurseries) redden
    extinguish light from forming objects
  • extinction factor e-tl, where tl ? l-n where n
    1?2
  • Distant galaxies recede from us
  • recession speed dependent on the distance
  • red-shift z Dl/l shifts galaxy emission
    to red, IR (e.g. Ha 656.3 nm ? 4.6mm at
    z6)

5
Why Space?
  • Earth and its atmosphere bright in the IR
  • T 280K blackbody peaks at l10 mm 10000 nm
  • Atmosphere blocks out much of the IR
  • from l 0.8 mm - 1000 mm 1 mm
  • Atmosphere makes point-like objects fuzzy
  • seeing - atmospheric motion distorts image
  • space experiments can be diffraction limited
    (q l/D where D telescope diameter)

6
SIRTF and NGST Detector Array Development
  • SIRTFs Infrared Array Camera using InSb arrays
    developed at UR
  • 256 x 256 pixels 5 field of view
  • NGST - detector array selection in 2002
  • 8Kx8K focal plane, diffraction limited at 2 mm
  • UR working on NGST detector technologies
  • SIRTF and NGST Scientific Requirement
  • all instruments to be background limited - this
    requirement means ultra-low dark current,
    ultra-low noise IR detector arrays

7
SIRTF Background( of detected photons/s-pix vs
?)
  • Fluctuations in background radiation are noise
    source
  • for l 1-5mm, read noise lt 10 e- and dark
    current lt 1 e-/s
  • for NGST - noise lt 3 e- and dark current lt 0.005
    e-/s

8
SIRTF - A Window on
Cosmic Birth
  • SIRTF will be considerably more sensitive at
    wavelengths between 3 and 200 ?m than previous IR
    missions, primary science goals ? Origins themes
  • The Early Universe
  • Ultra-luminous IR galaxies - ULIRG
  • Proto-planetary disks
  • Brown Dwarf stars

9
The Early Universe
  • All objects in HDF - Hubble Deep Field - are
    galaxies
  • Small, faint red objects the most distant (z ?
    3.4)
  • SIRTF, NGST will study in IR to higher z (earlier
    times in the universe)

10
The Early Universe (HST)Composite Visible and IR
View
  • Blue visible
  • Green 1.1 mm (1100 nm)
  • Red 1600 nm
  • Red objects could be distant, or dusty, or
    contain old stars
  • need spectroscopy or other method to identify
    redshift z l/Dl

11
NGST - Visiting a Time When Galaxies Were Young
  • NGST primary science goals (large, diffraction
    limited IR telescope - q 0.05)
  • A Search for Galaxy Origins
  • HST - Hubble Deep Field (galaxies that formed a
    few by after Big Bang)
  • NGST - will probe the era between that probed by
    COBE (300,000 - 106 yr after Big Bang and the
    era probed by HST
  • to identify when galaxies form, state of universe

12
Discovery Space for NGST
13
Faint, Red Distant Galaxies
  • Investigators have produced UV-NIR images of a
    faint galaxy. NIR signature identifies it as
    distant, red-shifted galaxy expands upon Lyman
    drop-out galaxy technique exploited on HST

14
Nearby Dwarf Galaxies
  • Nature of objects contributing to the faint blue
    galaxy counts unknown
  • Irregular, peculiar galaxies in composite colors
    (HST) formed at similar rates at higher z - but
    faint
  • Bright blue episode of star formation

15
Galaxies asCosmological Tools
  • Studies of galaxies probe cosmology in several
    ways
  • galaxies at z ?1 have significant look-back
    time - or early age (?0.4 current age)
  • quasars luminous galaxies observed to redshifts
    z 6
  • space density as function of z
  • star formation rates as function of z,
    morphological galaxy type
  • important to study distribution of average and
    dwarf galaxies to higher z
  • need contributions to extragalactic background

16
Mapping Dark Matter at High z with Gravitational
Lensing
  • HST image of massive galaxy cluster A2218 can
    deduce Mgalhalo
  • NGST simulations of lensed features for broad
    distribution of galaxies to z 10, with
    evolution applied, and size-dependence with z ?
    deduce core size of cluster mass distn

17
Starburst Galaxies
  • luminous nearby galaxies have bursts of massive
    star formation taking place - NGC 4214
  • during starburst epoch(s) galaxy luminosity can
    be 100-1000 x Milky Way luminosity
  • starburst triggers?

18
Starburst Activity Quantified
  • Star formation rate a function of z (age)
    normalized to the present epoch
  • HST observations suggest steep rise in starburst
    soon after the Big Bang ground-based
    observations show decline
  • HST, SIRTF, NGST probe the peak and early times

19
Ultraluminous Galaxies
  • Some galaxies are ULIRG - ultraluminous infrared
    galaxies - 1000 x luminosity of Milky Way galaxy
  • Many of these are examples of multiple colliding
    systems
  • Relation to starbursts? AGNs?

20
The Early UniverseVisible and Deep X-Ray View
  • 6 galaxies in the HDF N are X-ray emitters
  • one, an extremely red edge-on spiral, hosts AGN
    (Active Galactic Nucleus with accretion disk, 109
    M? black hole)
  • AGN
  • 3 ellipticals
  • 1 spiral
  • X-ray sources AGN hot gas emission X-ray binary

21
Formation of Stars
  • Well established that stars form in GMCs (giant
    molecular clouds), and that formation of a disk
    and high velocity outflows a signature
  • yields important information on cloud support
    how angular momentum conserved as protostars
    shrink
  • Stars blow away disk as evolve to main sequence
  • If star forms planetary system, onset of debris
    disk

22
Disks and Jets
  • HH111 shows pair of 12 ly jets blasted from
    system of 3 stars located near a tilted edge-on
    dusty torus, episodic ejections
  • NGST will image in close to the central YSO -
    both SIRTF and NGST can extend sample to nearby
    galaxies

23
Debris and Proto-planetary Disks
  • IRAS discovered that ordinary stars had disks
    emitting in the far IR
  • Many examples studied with a coronograph from the
    ground - most famous example, ? Pictoris
  • Early solar system had disk (proto-planetary
    disks)
  • New studies (HST, ground) show resonant gaps
  • SIRTF will FIR images and spectroscopy of debris
    disks (structure, mass, composition) NGST can
    exploit superior sensitivity and spatial
    resolution

24
Debris andProtoplanetary Disks
  • Debris Disk b Pictoris
  • Note resonant cleared gap - major planet

25
Brown Dwarfs
  • Importance of low mass
    failed stars as halo
    constituents in our own
    Milky Way Galaxy,
    and in
    clusters within our Galaxy unknown
  • Gliese 229B best known methane dwarf example -
    few dozen now known
  • L dwarfs - objects T lt2000K few hundred known
  • Spectra dominated by molecular bands
  • SIRTF surveys spectroscopy NGST surveys -
    contribution to mass budget

26
Brown Dwarfs in Orion
  • Swarm of Newborn Brown Dwarfs found in Orion
    stellar nursery

27
Conclusion
  • SIRTF and then NGST will take us back to the
    early times when galaxies formed, and will
    address
  • range in z that formation took place AGN,
    starburst phases in galaxy evolution pin down
    cosmological parameters
  • bottom-up or top-down scenario for star formation
    in galaxies mass function of galaxies
  • SIRTF and NGST will define the history of
    planetary systems around other stars
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