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

10/21/00 AAPT/APS Joint Fall Meeting2 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?

10/21/00 AAPT/APS Joint Fall Meeting3 Big Themes Big Space Experiments - IR SIRTF - Space InfraRed Telescope Facility –cold, 0.85-m telescope; 7/02 launch –cameras  m; spectrometers  m; photometers 24, 70, 160  m; lo-res spectrometer  m NGST - Next Generation Space Telescope –cold, 8-m telescope, planned for /08 launch –successor to the Hubble Space Telescope

10/21/00 AAPT/APS Joint Fall Meeting4 Why Infrared - IR? Cool objects radiate in the infrared – max  T -1 Wien’s blackbody law (e.g. T=100K, max =30  m = 30,000 nm) Dusty clouds (= stellar nurseries) redden & extinguish light from forming objects –extinction factor e- , where     n where n =1  2 Distant galaxies recede from us –recession speed dependent on the distance –red-shift z =  shifts galaxy emission to red, IR (e.g. H  nm  4.6  m at z=6)

10/21/00 AAPT/APS Joint Fall Meeting5 Why Space? Earth and its atmosphere bright in the IR –T ~280K blackbody peaks at ~10  m = nm Atmosphere blocks out much of the IR –from  = 0.8  m  m = 1 mm Atmosphere makes point-like objects fuzzy – “seeing” - atmospheric motion distorts image –space experiments can be diffraction limited (  ~ /D where D = telescope diameter)

10/21/00 AAPT/APS Joint Fall Meeting6 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  m –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

10/21/00 AAPT/APS Joint Fall Meeting7 SIRTF Background (# of detected photons/s-pix vs ) Fluctuations in background radiation are noise source for = 1-5  m, read noise < 10 e- and dark current < 1 e-/s for NGST - noise < 3 e- and dark current < e-/s

10/21/00 AAPT/APS Joint Fall Meeting8 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 Ë Ultra-luminous IR galaxies - ULIRG Ì Proto-planetary disks Í Brown Dwarf stars

10/21/00 AAPT/APS Joint Fall Meeting9 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)

10/21/00 AAPT/APS Joint Fall Meeting10 The Early Universe (HST) Composite Visible and IR View Blue = visible Green = 1.1  m (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 = 

10/21/00 AAPT/APS Joint Fall Meeting11 NGST - Visiting a Time When Galaxies Were Young NGST primary science goals (large, diffraction limited IR telescope -  ~ 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, yr after Big Bang and the era probed by HST – to identify when galaxies form, state of universe

10/21/00 12 Discovery Space for NGST

10/21/00 AAPT/APS Joint Fall Meeting13 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

10/21/00 AAPT/APS Joint Fall Meeting14 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

10/21/00 AAPT/APS Joint Fall Meeting15 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

10/21/00 AAPT/APS Joint Fall Meeting16 Mapping Dark Matter at High z with Gravitational Lensing HST image of massive galaxy cluster A2218: can deduce M gal+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

10/21/00 AAPT/APS Joint Fall Meeting17 Starburst Galaxies luminous nearby galaxies have bursts of massive star formation taking place - NGC 4214 during starburst epoch(s) galaxy luminosity can be x Milky Way luminosity starburst triggers?

10/21/00 AAPT/APS Joint Fall Meeting18 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

10/21/00 AAPT/APS Joint Fall Meeting19 Ultraluminous Galaxies Some galaxies are ULIRG - ultraluminous infrared galaxies x luminosity of Milky Way galaxy Many of these are examples of multiple colliding systems Relation to starbursts? AGNs?

10/21/00 AAPT/APS Joint Fall Meeting20 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, 10 9 M  black hole) –AGN –3 ellipticals –1 spiral X-ray sources: AGN; hot gas emission; X-ray binary

10/21/00 AAPT/APS Joint Fall Meeting21 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

10/21/00 AAPT/APS Joint Fall Meeting22 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

10/21/00 AAPT/APS Joint Fall Meeting23 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

10/21/00 AAPT/APS Joint Fall Meeting24 Debris and Protoplanetary Disks Debris Disk  Pictoris Note resonant cleared gap - major planet

10/21/00 AAPT/APS Joint Fall Meeting25 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 <2000K; few hundred known Spectra dominated by molecular bands SIRTF surveys & spectroscopy; NGST surveys - contribution to mass budget

10/21/00 AAPT/APS Joint Fall Meeting26 Brown Dwarfs in Orion Swarm of Newborn Brown Dwarfs found in Orion stellar nursery

10/21/00 AAPT/APS Joint Fall Meeting27 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