a spitzer survey of the large magellanic cloud: surveying the agents of a galaxy’s evolution...

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

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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)

April 18, 2007 R. Blum – University of Connecticut Physics Colloquium

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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