Early Extragalactic Results from Spitzer

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Early Extragalactic Results from Spitzer Tom
Soifer Caltech/SSC
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Cutaway View of the Spitzer Space Telescope
Dust Cover Secondary Mirror Primary
Mirror Instrument Chamber Startrackers Gyros
High Gain Antenna
Solar Panel Solar Panel Shield Outer
Shell Cryostat Helium Tank Spacecraft
Shield Spacecraft Bus
Cutaway provided by Ball Aerospace
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Spitzers Instruments
Payload is simple and robust one mechanism and
7-to-8 observing modes among the three
instruments
IRS infrared spectrograph J.Houck Cornell
MIPS multiband imaging photometer G.Rieke Arizon
a
IRAC infrared array camera G.Fazio Harvard/ SAO
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Spitzer Wavelength Coverage
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Spitzer Sensitivity Comparison (on-orbit
performance)
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M81 Visible Light
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M81 3.5 to 8µm Composite
M81 Spitzer 3.5 to 8µm Composite
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Power of IR ClassificationEdge-on Spiral NGC
5746
Spitzer/IRAC 3 -10 mm
Optical gri
2MASS JHK
Jarrett et al. 2003 (AJ, 125, 525)
Frei al. 1996 (AJ, 111, 174)

• Prominent dust lane in optical (and even near-IR)
  prevents unambiguous classification
• IR images demonstrate class "Sab" with ring
• Star formation concentrated along ring and
  outside it

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NGC 5128 - Centaurus A
Visible image
IRAC image
Keene et al. 2004
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IR Galaxy Gallery
NGC 777
NGC 5846
NGC 5813
NGC 5322
NGC 5077
NGC 1023
E
S0
NGC 5079
NGC 5363
NGC 4203
NGC 6340
NGC 5548
NGC 3031 (M 81)
NGC 5746
S0
Sab
NGC 3147
NGC 1961
NGC 5669
NGC 6689
NGC 5668
NGC 300
Sbc
Sd
NGC 5585
NGC 5204
NGC 2366
NGC 1156
NGC 1569
NGC 4038/9 "Antennae"
Im
Sm
Pahre et al. 2004, ApJSupp
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(Armus et al. 2004)
Figure 7 Low-resolution spectrum of UGC 5101
(top). The plots to the right show zoom-ins on
the Ne II, Ne III, H2 and S III lines
observed with the high-resolution modules (a
Gaussian fit to the line is overplotted in red).
This example illustrates the complementary
utilization of both low- and high-resolution
modules.
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High resolution spectrum of UGC 5101
(Armus et al. 2004)
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FLS Extragalactic Source Counts at 24 mm
0.2 0.7
Galaxy evolution models
Franceschini et al. (2001) Rodighiero et al.
(2004) non-evolving normal pop, fast-evolving
type-II AGNs starbursts, evolving type-I AGNs
Lagache, Dole Puget (2003) non-evolving normal
spirals and starbursts with L density evolving
with redshift
IRAS data points (transformed to 24 µm) (Hacking
Soifer 1991 Sanders et al. 2003)
No-evolution model normalized to IRAS counts
Marleau, Fadda, Storrie-Lombardi, et al. 2004
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What is the content of the sky at 24 microns?
Without more detailed knowledge color-color
plots provide first inkling of what sources
might be. Top Panel Scatter plot of sources
found in First Look Survey, along with deep
visible Imaging information. Bottom Panel
tracks of what known classes of extragalactic
sources would do in this plane as a function of
redshift
Yan et al. 2004, ApJSupp
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(No Transcript)
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The 24µm Blank Field Sources
A NEW CLASS OF GALAXY?

• 0.4 of sources _at_ 0.7 mJy have no
• optical counterpart to 26.5(Vega) mag
• At z2 f?(24µm)/ f?(R)gt250
• Exceeding Arp 220 most extreme IR
• galaxy in local universe by factor of 40
• Some have IRAC SEDs, but unresolved
• at IRAC spatial resolution
• IRS spectra required for z determination
• What are they? (AGN, Starburst, ??)
• Eisenhardt et al. 2004 ApJSupp

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Properties of Optical Counterparts
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Low Metallicity, High Luminosity, High Star
Formation Rate
MIPS Position
z2.658 system
Lya nebula 6 or 50 Kpc
Lbol 4x1013Lo (4x103 Mo/yr star formation rate)
Dey et al. 2004
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Overall Assessment
GOODS CDF-S IRAC 4.5 µm Feb. 2004 23
hours/point 10 x 10 arcmin
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Spitzer Looks Back in Time and Space
4.5 µm
3.6 µm
5.8 µm
8 µm
z5.8 galaxy
M.Dickinson GOODS team
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Spitzer IRAC images (Egami et al.) are
consistent with the spectral energy distribution
of a newly forming galaxy
IRAC image at 3.6um
HST discovery image
LENSED GALAXY AT z7 J-P Kneib, R. Ellis et
al. DISCOVERY WITH HST/ACS
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model fits
Age 50-450 Myr Mass 5-10 x 108 M?
Age of Universe at time galaxy is observed 800
Myr Age of Universe when galaxy started forming
600Myr (z9) Combining Spitzer data with other
results permits more accurate estimates of when
galaxies formed
Egami, Kneib et al. 2004
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Summary

• Spitzer is producing spectacular results for
• Extragalactic Astronomy !!!!
• IRAC probes the structure of galaxies in both
  starlight and molecular gas with unparalleled
  resolution, area coverage, sensitivity
• IRS probes the spectra of IR Bright Galaxies with
  sensitivity such that we can reach to substantial
  fractions of the age of the Universe
• MIPS surveys are leading to new understanding of
  the dusty infrared universe
• IRAC deep observations seeing rest frame optical
  light in the youngest galaxies
• New populations of galaxies are being discovered
  in deep surveys
• Spitzer will uncover much more of the Dusty
  Universe
• Much remains to be discovered by Herschel ALMA

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Spitzer Observation Planning Workshops for Cycle 2

• Washington, DC, USA, 6 7 Dec 2004
• San Diego, CA, USA, 9 January 2005
  (immediately before AAS Meeting)
• Noordwijk, Netherlands, at ESTEC 12
  January 2005

• To register, go to http//ssc.spitzer.caltech.edu/
  ost/workshops
• or email obsplan_at_ipac.caltech.edu

Proposals for Cycle 2 Due 12 February 2005