Origin and evolution of dust in Origin and evolution of dust in galaxiesgalaxies

Can we account for the dust in Can we account for the dust in galaxies by stellar sources?galaxies by stellar sources?

Origin and evolution of dust in Origin and evolution of dust in galaxiesgalaxies

Can we account for the dust in Can we account for the dust in galaxies by stellar sources?galaxies by stellar sources?

Mikako MatsuuraOrigin’s fellow, Institute of Origins, University College London

M.J. Barlow, G.C. Sloan, A.A. Zijlstra, D. Stock, P.A. Whitelock, P. R. Wood,

M.-R.L. Cioni, M.A.T. Groenewegen, K. Volk, J. Bernard-Salas, F. Kemper, T. Kodama, E. Lagadec, M. Meixner, S. Srinivasan, C.

Szyszka, J.Th. van Loon

IntroductionIntroductionIntroductionIntroductionMid- and far-IR emission of

galaxies◦ Thermal emission from dust grains

Questions to answer◦ Can we account for dust mass in the

interstellar medium (ISM) by stellar sources? C.f. Main source of the dust in our Galaxy

Asymptotic giant branch stars (AGB) stars – low and intermediate stars (Gerz 1989)

SNe – high mass stars ?

◦ Can we apply for that to all galaxies? Testing based on observations

Dust mass in the ISM of galaxies

Drain et al. (2007)

Case 1: Large Magellanic Cloud Case 1: Large Magellanic Cloud (LMC)(LMC)Case 1: Large Magellanic Cloud Case 1: Large Magellanic Cloud (LMC)(LMC)

One of the nearest galaxy ◦ 50 kpc

Spitzer Space Telescope observations◦ Spectroscopic survey of

selected objects◦ Photometric survey 3.6-

160 mcron Entire census of AGB stars Measuring dust mass formed

in AGB stars

3.6 micron: blue8.0 micron: green24 micron: red

Optical image

SAGE

Dust mass in the ISM of galaxies

Analysis (1) : selection of dust Analysis (1) : selection of dust forming AGB starsforming AGB starsAnalysis (1) : selection of dust Analysis (1) : selection of dust forming AGB starsforming AGB stars

Matsuura et al. (2009, MNRAS 396, 918)

AGB stars are the brightest population in mid-infrared

Distant galaxies

Foreground stars

Emission line objects(WR stars)

HII regions / YSOs

Dust mass in the ISM of galaxies

Mid-infrared color magnitude diagramme [8.0] vs [3.6]-[8.0]

Analysis (2) estimate of gas and Analysis (2) estimate of gas and dust lost from individual AGB dust lost from individual AGB starsstars

Analysis (2) estimate of gas and Analysis (2) estimate of gas and dust lost from individual AGB dust lost from individual AGB starsstarsDetailed analysis of 40

AGB stars provides dust/gas mass-loss rate rate (M yr-1)

JHKL photometry Spitzer spectra (5-35 micron)

◦ Spectral energy distributions are fitted, using radiative transfer code, including dust

Groenewegen et al. (2007, MNRAS 376, 313)

Dust mass-loss rate: 3.1x10-8 M yr-1

Dust mass in the ISM of galaxies

Log dM/dt=-6.2/[([3.6]-[8.0])+0.83]-3.39

Identified AGB stars + Identified AGB stars + measured their mass-loss rate measured their mass-loss rate (gas and dust mass)(gas and dust mass)

Identified AGB stars + Identified AGB stars + measured their mass-loss rate measured their mass-loss rate (gas and dust mass)(gas and dust mass)

Detecting dust-embedded AGB stars using SpitzerMatsuura et al. (2009, MNRAS, 396, 918)

Global dust budget in the Global dust budget in the Large Magellanic CloudLarge Magellanic CloudGlobal dust budget in the Global dust budget in the Large Magellanic CloudLarge Magellanic Cloud

Missing dust mass problem in the LMC! Current LMC dust mass: 2x106 M

◦ HI+H2 gas mass (8x108 M) x dust-to-gas ratio (0.0025)

Dust injection rate from AGB stars: 4.3x10-5 M yr-1 (up to 8x10-5 M yr-1)

◦ requires>20 Gyrs Lifetime of the LMC (~15 Gyrs)◦ Dust lifetime was estimated to be 4-8x108 yrs (Jones et al. 1994)

Dust deficit is short by a factor of 30

ISM dust2x106 M

ISM dust2x106 M

SNeDust formation?

Shock destruction?

Dust mass in the ISM of galaxies

Solutions for the dust deficit?Solutions for the dust deficit?Solutions for the dust deficit?Solutions for the dust deficit? Lower SN dust destruction rate

Dust from high mass stars◦ Higher SNII dust production rate

0.5 M from Cas A and 1.2 M from Kepler

◦ Dust from red supergiants (RSG) High number of RSG population in the LMC

Unaccounted dust mass in AGB stars?

Dust may be formed in starforming regions

Herschel/SPIRE 240 micron imageN49: Supernova Remnant

Dust mass in the ISM of galaxies

Case 2:Case 2:Case 2:Case 2:

Dust in different environment: low-metallicity galaxies

- Bridging local group galaxies to high-z galaxies

Dust mass in the ISM of galaxies

Can dust be formed at low metallicities?Can dust be formed at low metallicities?Dust needs (astronomical) metals!Dust needs (astronomical) metals!Can dust be formed at low metallicities?Can dust be formed at low metallicities?Dust needs (astronomical) metals!Dust needs (astronomical) metals!

Oxides◦ Olivines : Mg2xFe(2-2x)SiO4

◦ Pyroxenes : MgxFe1-xSiO3

Carbonaceous dust◦ Graphite : C◦ Amorphous : C◦ Polycyclic aromatic

hydrocarbons (PAHs)

Dust mass : as a function of metallicity of galaxiesIt has been suggested that it is difficult to form dust grains in stars in low metallicity (Z<0.1 Z) galaxies

Dust mass : as a function of metallicity of galaxiesIt has been suggested that it is difficult to form dust grains in stars in low metallicity (Z<0.1 Z) galaxies

But … we found unexpected results

Dust mass in the ISM of galaxies

The Galaxies of the Local The Galaxies of the Local GroupGroupThe Galaxies of the Local The Galaxies of the Local GroupGroupSome galaxies have low metallicities

Sculptor dwarf spheroidal (dSph) galaxy [Z/H]~-1.33

Fornax dwarf spheroidal galaxy[Z/H]~-1.0

Dust mass in the ISM of galaxies

Spitzer spectraSpitzer spectraSpitzer spectraSpitzer spectra

Sculptor dSph galaxy [Z/H]~-1.33Sloan, Matsuura et al. (2009, Science 323, 353)

Contrary to expectation, we detected dust at low metallicities

SiC

Amorphous Carbon

Fornax dSph galaxy [Z/H]~-1.0Matsuura et al. (2007, MNRAS 382, 1889)

Dust mass in the ISM of galaxies

Dust at low metallicityDust at low metallicityDust at low metallicityDust at low metallicityAGB stars

We detected amorphous (+SiC) dust

Carbon atoms synthesized in AGB stars

Dust formation process around stars is affected◦ not only by the

metallicity of the parent galaxies

◦ but also by elements formed inside stars, in particular, carbon

◦ Amorphous carbon, PAHs

Matsuura et al. (2005 A&A 434, 691)

(Fornax and Sculptor dSph galaxies)(Our Galaxy)

Dust mass in the ISM of galaxies

Implications for high-z galaxies Implications for high-z galaxies with dustwith dust

Implications for high-z galaxies Implications for high-z galaxies with dustwith dust

Dust sources:AGB stars + SNe? About solar metallicity

10-15 Gyrs

Assumed to be low metallicity initially

z~6.4; 0.84 Gyrs(e.g. Bertoldi et al. 2003)

Dust sources:SNe (>8 Msun)

(Before our study)

Our GalaxyHigh-z galaxies

Dust can be formed in AGB stars and SNe even at low metallicity

Age of AGB stars is much younger than previously thought (starting 50 Myrs)Sloan, Matsuura et al. (2009, Science, 323, 353)

ConclusionsConclusionsConclusionsConclusionsAGB stars are important dust sources

◦But still found deficit in dust budget in the LMC Solutions will be tested using Herschel observations

◦Dust from AGB stars are more carbon-rich, and contain more PAHs at lower metallicity <-> ISM: weak PAHs High UV radiation in the ISM at low metallicity destroy

PAHs

High-z galaxies◦Lower metallicities do not hamper dust formation

in AGB stars◦Dust mass in high-z galaxies may be explained, if

both SNe and AGB stars contribute dust formation

Dust mass in the ISM of galaxies

5-8th July 2010Windsor Great Park, suburb of London, Englandhttp://zuserver2.star.ucl.ac.uk/~cl2010/cl2010@star.ucl.ac.uk

Extragalactic Star Formation