a spitzer survey of the large magellanic cloud: surveying the agents of a galaxy’s evolution...
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A Spitzer Survey of the Large Magellanic Cloud:
Surveying the Agents of a Galaxy’s Evolution (SAGE)
Bob Blum (NOAO/Tucson)and the SAGE Team
http://sage.stsci.edu/
Image credit, Karl Gordon
April 18, 2007 R. Blum – University of Connecticut Physics Colloquium
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SAGE team members: http://sage.stsci.edu/
• Space Telescope Science Institute: Meixner (PI, database lead), Leitherer (team web page), Nota, Panagia, Vijh
• University of Wisconsin: Churchwell (IRAC pipeline lead), Meade, Babler, Bracker, Gallagher
• SSI: Whitney (star formation co-lead)
• University of Arizona: Gordon (MIPS pipeline lead), Engelbracht, Misselt, For, Zaritsky, Harris, Kelly, Perez
• Spitzer Science Center/JPL: Reach (ISM co-lead), Latter, van Dyk, Werner, Gorjian
• NOAO: Blum (Evolved star lead), Olsen, Mould, Points
• Nagoya University, Japan: Onishi, Fukui, Kawamura, Mizuno, Mizuno (CO survey), Shibai (ASTRO-F), Shuji (Near-IR survey)
• CESR/Saclay/IAS: Bernard (ISM co-lead), Madden, Boulanger, Paladini
• UC Berkeley: Cohen (calibration)• University of Virginia: Indebetouw
(star formation co-lead)• Harvard/CfA: Hora (IRAC team) • NASA/Ames: Tielens (IRS)• Gemini: Volk• University of Michigan: Oey• University College London: Smith• AURA: Frogel• CSIRO: Staveley-Smith• JHU: Srinivasan• University of Denver: Ueta• Manchester: Markwick-Kemper
(IRS)
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Preliminaries• 1 parsec (pc) = 3.25 light yr = 3.1x1018
cm
• CMD = color-magnitude diagram
(temperature vs luminosity for stars-
>temperature vs mass)
• Color = ratio of flux in two broad pass
bands (filters)
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Lambda CDM
&
Galaxy
Formation
•=~ 70%
•DM =~ 25%
•b =~ 5%
•+DM+b=1
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Galaxy Formation via Merging
Look
Back
Tim
e (
Gyr)
Colo
r (B - V
)
Run simulation, compare to galaxy counts (e.g. SDSS)
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The Local Group
Resolved
stellar
populations
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Mergers in the Local Group
• Milky Way streams, O Cen, Sgr Dwarf
• Andromeda halo inhomogeneities
• Problem for LCDM? Deficit of dwarf
galaxies
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Magellanic Clouds
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The Large Magellanic Cloud
• galaxy evolution– Star formation history (SFH)– Chemical enrichment history (CEH)– Interactions (merger)
• 50 kpc• 1010 Msun
• 108 Msun in gas
• SFR ~ 0.5-1 Msun/yr
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Parr (1998,CISRO)
Magellanic Stream
•H I
•Ram pressure
•Tidal stripping
•Bridge
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New Proper Motions
Besla et al. (2007)
•HST proper
motions (QSOs)•Two year
separation•New 3-space
velocity (380
kms)•Unbound!
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HST SFH
Smecker-Hane et al., 2002
•Stellar evolution
models
•Maximum
likelihood fit to
number of stars in
each cell of CMD
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LMC SFH
Smecker-Hane et al., 2002
SFR
(M
sun
/yr/
sqdeg
) S
FR (
Msu
n/y
r/sq
deg
)
Age (Gyr) Age (Gyr)
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Chemical Enrichment:
Element Ratios
Solar Abundance: Log10(nH)=12
Plot credit: NASA
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-Element Ratios
• SNe Type I vs Type II
• Star formation history
• Chemical imprint in stellar
abundance patterns
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Johnson, et al. (2006)
-Element Ratios
•LMC, Milky Way have
distinct enrichment
histories
•No local dwarf looks
like components of
the Milky Way
•WFMOS
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SAGE and The Large Magellanic Cloud
• Add MLH to SFH+CEH -> Complete picture of a galaxy's evolution
• Life cycle of matter: Old stars <-> ISM <-> Young Stars
• Global SED, contributions from ext and point srcs
• Use the galaxy components to inform studies of SF at high redshift
• Overview: Meixner et al. (2006); Evolved stars: Blum et al. (2006)
April 18, 2007 R. Blum – University of Connecticut Physics Colloquiumcredit: http://hea-www.cfa.harvard.edu/CHAMP/EDUCATION/PUBLIC/ICONS/
Intermediate mass stars High mass stars
Tracing the Life Cycle of Baryonic Matter:
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Spitzer
• Launch August
25, 2003 (day
1332)
• Mission life 5
yr+ (Cycle 4 last
full cycle)
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Spitzer
• 85 cm Telescope
– DL 6.5um
– LHe cooled (360 ltr)
– Trailing Earth orbit
(0.1 AU/yr)
– Temp ~ 40 K
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Spitzer Instruments• IRAC (Infrared Array Camera),
– 3.6 um, 4.5 um InSb
– 6.5 um, 8.0 um SiAs
– 5.12 arc minute FOV, 1.2'' pixels
• MIPS (Multi-band Imaging Photometer)
– 128x128 SiAs 24 um, 32x32, 2x20 GeGa 70, 160 um
– 2.5'', 5''/10'', 16'' pixels
• IRS (Infrared Spectrometer)
– 5-40 um
– R=50-600
April 18, 2007 R. Blum – University of Connecticut Physics Colloquium
Spitzer Instruments 2
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SAGE Science: Key ISM Questions
• ISM in the LMC:– What are the properties and abundance of
dust in different parts of the LMC? – What is the structure of the ISM in the
LMC? Separate stars from extended emission, investigate HII, PDRs, MCs, diffuse ISM. Explore relationship of dust emission to UV and kinetic energy sources
April 18, 2007 R. Blum – University of Connecticut Physics Colloquium
SAGE key Star Formation questions:
• Star Formation in the LMC:– What is the galaxy-wide star formation rate
of the LMC and how do the details vary on scales of a few pc?
– GMC's: look for low mass or embedded SF– Do tidally-triggered star formation events
sustain themselves by propagating through the ISM, or are they short-lived? Interplay between triggering and dispersal.
April 18, 2007 R. Blum – University of Connecticut Physics Colloquium
SAGE Science: Key Evolved Star Questions:
• Stellar Mass-loss Return to the LMC:– What is the mass budget of material injected
into the ISM by evolved stellar winds? – How does stellar mass loss rate depend on
stellar parameters: L, Teff, period, chemistry (C- or O-rich), Z?
• SFH+colors -> building blocks of high z galaxies
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Spitzer SAGE survey in context of other LMC surveys
Two epochs: Jul/Aug 05, Oct/Nov 05, 500 hr
MIPS bands: 24, 70, 160 um,Fast Scan map, 38 legs of 25'x4 deg
IRAC bands:3.6, 4.5, 5.6, 8 um,14x28 HDR 0.6s 12s per 1.1 deg tile
CO
HIHI IRAS Halpha/MIPS
UV Stars/IRACUV
IRAS 100 um Ha
Stellar density
MCELS, Smith, Points et al.
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Previous IR surveys of LMC• IRAS: 12, 25, 60, 100 um (Schwering 1989)
– 8.5x8.5 degree coverage– 1 arc minute angular resolution– 1823 object point source list
• MSX: 8 um (Egan, van Dyk & Price 2001)– 10x10 degree coverage– 20'' angular resolution– 1806 object point source list
• 2MASS: J, H, Ks (Nikolaev & Weinberg 2000) & DENIS I, J, H, Ks (Cioni et al. 2000)
– ~2'' angular resolution– 820,000; 1.3 million
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IRAC Tile, 3.6, 4.5, 8.0
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24
70
160
MIPS Scan Maps
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IRAC 3.6, 4.5, 8.0C
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MIPS 24, 70, 160
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Hess Diagram
LMC A-G SG
Saturation
J-band limit
Foreground
LMC OBTRGB
AGB
RGB
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Models 1• Marigo (2002)
• C/O varies on TP-AGB
• Previous models used fixed, scaled, opacity (C/O=solar)
• New models have variable opacities
• Net result, C stars move to lower Teff (O-rich stars don't)
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Models 2
Ks
J-Ks• Cioni et al. (2006) use Marigo models to
explain C-star locus in 2MASS CMD• Define photometric selection of C-, M-
stars
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• SAGE has IRAC plus
2MASS catalog, so we
can define regions in
NIR/MIR CMDs
• Four main evolved star types:
– C-rich
– O-rich
– SG
– Extreme
O-richC-rich
SGExtreme
[3.6
]
J - [3.6]
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Spatial
distributions
match
source types
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Dust
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Galaxies
Lots of galaxies, “2MASS J-band drop outs”
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SWIRE ELAIS N1• Approx 300 sources
per square degree to [8.0]=13.5,
• Similar result using [8.0] and [24]
• Slightly more SAGE sources at [3.6], [8.0]
• Brighter sources in LMC -> YSOs
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24 microns
• SAGE sees all important
mass losing sources
• Lower L mass losing
sources -> cool, dusty
envelopes
• IRS spectra give dust
envelope chemistry
Buchanan et al. (2006)
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Mass Loss Rates
van Loon et al., (1999)
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Mass Loss RatesLo
g1
0 (
10
6*M
sun/y
r)
Log
10 (
10
6*M
sun/y
r)
[24][24]
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Kevin Volk
Dust Shell Models
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Model Grid
Kevin Volk
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Young Stellar Objects
?
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Identifying and Analyzing on-going SF
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N4
30”
RGB=24,8,4.5um contours=cm continuum (RI et al. 2005)
candidate YSOs: example
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''Image courtesy of Rémy Indebetouw
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12CO from NANTEN, Fukui et al.Images courtesy of Rémy Indebetouw
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The Global SED
*
* * All evolved
stars
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Carbon Rich AGB stars: 1.70E-03, 25%
Oxygen Rich AGB stars: 1.70E-03, 25%
Super giants ([3.6] < 10): 1.00E-03, 13%
Extreme AGB: 2.60E-03, 37%
Total: 7.00E-03, 100%
Similar to SN rate (Chu & Kennicutt 1988)
Mass Loss by type over Entire LMC(Msun/yr)
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Summary
• SAGE completes galaxy evolution for the
LMC, leveraging a vast archive of UV,
Optical, IR, and radio data
• Detects ``all'' mass losing sources in
galaxy
• Evolved stars are a very significant
source of input to the ISM