Transcript Lifting the Dusty Veil on the Cradle of Star Birth

A Window on Cosmic Birth:
Exploring our Origins with the
SIRTF and NGST Space
Missions
Judith L. Pipher
University of Rochester
Searching for Origins

How did galaxies form in the early
universe?
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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?
10/21/00
AAPT/APS Joint Fall Meeting
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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
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Why Infrared - IR?

Cool objects radiate in the infrared
– lmax  T-1 Wien’s blackbody law
(e.g. T=100K, 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 z=6)
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Why Space?

Earth and its atmosphere bright in the IR
– T ~280K blackbody peaks at l~10 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)
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SIRTF and NGST Detector
Array Development

SIRTF’s 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
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SIRTF Background
(# of detected photons/s-pix vs l)
5
1 10

4
1 10
N' l i , 0.85 . m , I SIRTF l i
sec
1
q beam l i , 0.85 . m

1000
100
arcsec

10
1
1
10
100
1000
Fluctuations in
background radiation
are noise source
for l = 1-5mm, read
noise < 10 e- and dark
current < 1 e-/s
for NGST - noise < 3 eand dark current <
0.005 e-/s
li
mm
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SIRTF - A Window on
Cosmic Birth
SIRTF will be considerably more sensitive at
wavelengths between 3 and 200 mm than
previous IR missions, primary science goals
 Origins themes
 The Early Universe
 Ultra-luminous IR galaxies - ULIRG
 Proto-planetary disks
 Brown Dwarf stars
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AAPT/APS Joint Fall Meeting
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The Early Universe
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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)
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The Early Universe (HST)
Composite Visible and IR View
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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
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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
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Discovery Space for NGST
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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 dropout galaxy” technique exploited on HST
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Nearby Dwarf Galaxies
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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
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Galaxies as
Cosmological 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
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Mapping Dark Matter at High
z with Gravitational Lensing
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HST image of massive
galaxy cluster A2218:
can deduce Mgal+halo
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 dist’n
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AAPT/APS Joint Fall Meeting
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Starburst Galaxies
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luminous nearby
galaxies have bursts
of massive star
formation taking
place - NGC 4214
during starburst
epoch(s) galaxy
luminosity can be 1001000 x Milky Way
luminosity
starburst triggers?
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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
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AAPT/APS Joint Fall Meeting
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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?
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The Early Universe
Visible 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
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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
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If star forms planetary system, onset of
debris disk
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Disks and Jets
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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
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AAPT/APS Joint Fall Meeting
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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
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Debris and
Protoplanetary Disks
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Debris Disk  Pictoris
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Note resonant cleared
gap - major planet
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Brown Dwarfs
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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 <2000K; few hundred known
 Spectra dominated by molecular bands
 SIRTF surveys & spectroscopy; NGST surveys contribution to mass budget
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AAPT/APS Joint Fall Meeting
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Brown Dwarfs in Orion
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Swarm of Newborn Brown Dwarfs
found in Orion stellar nursery
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Conclusion
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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
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SIRTF and NGST will define the history of
planetary systems around other stars
10/21/00
AAPT/APS Joint Fall Meeting
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