Title: Investigators have produced UV-NIR images of a faint galaxy
1A Window on Cosmic Birth
- Exploring our Origins with the SIRTF and NGST
Space Missions - Judith L. Pipher
- University of Rochester
2Searching 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
4Why 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)
5Why 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)
6SIRTF 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
7SIRTF 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
8SIRTF - 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
9The 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)
10The 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
11NGST - 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
12Discovery Space for NGST
13Faint, 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
14Nearby 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
15Galaxies 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
16Mapping 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
17Starburst 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?
18Starburst 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
19Ultraluminous 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?
20The 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
21Formation 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
22Disks 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
23Debris 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
24Debris andProtoplanetary Disks
- Note resonant cleared gap - major planet
25Brown 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
26Brown Dwarfs in Orion
- Swarm of Newborn Brown Dwarfs found in Orion
stellar nursery
27Conclusion
- 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