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/[email protected]
Extragalactic Star Formation