The Chemical Evolution of the Galaxy and Dwarf Spheroidals of the ...

  • 255 views
Uploaded on

 

More in: Technology , Business
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
    Be the first to like this
No Downloads

Views

Total Views
255
On Slideshare
0
From Embeds
0
Number of Embeds
1

Actions

Shares
Downloads
1
Comments
0
Likes
0

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide
  • Classificazione delle sorgenti prima di tutto con la conferma spettroscopica poi con le altre informazioni
  • SN search are not uniform: 1 – galaxy dust obscuration (to be addressed later on)

Transcript

  • 1. The Chemical Evolution of the Galaxy and Dwarf Spheroidals of the Local Group Saas-Fee, March 4-10, 2007
  • 2. Chemical Evolution of the Galaxy and dSphs of the Local Group
  • 3. Outline of the lectures
    • Lecture I: Basic principles of chemical evolution, main ingredients (star formation history, nucleosynthesis and gas flows)
    • Lecture II: Supernova progenitors, basic equations, analytical and numerical solutions
    • Lecture III: Detailed chemical evolution models for the Milky Way
    • Lecture IV: Model results for the formation and evolution of the Milky Way
  • 4. Outline of the lectures
    • Lecture V: SFR and Hubble sequence, the effects of the time-delay model on different galaxies
    • Lecture VI: Chemical properties and models of chemical evolution of dSphs
    • Lecture VII: Comparison between the evolution of dSphs and the Milky Way. Interpretation of the alpha/Fe and s- and r- process el./Fe ratios
  • 5. How to model galactic chemical evolution
    • Initial conditions (open or closed-box; chemical composition of the gas)
    • Birthrate function (SFRxIMF)
    • Stellar yields (how elements are produced and restored into the ISM)
    • Gas flows (infall, outflow, radial flow)
    • Equations containing all of of this...
  • 6. Initial Conditions
    • a) Start from a gas cloud already present at t=0 (monolithic model). No flows allowed (closed-box)
    • b) Assume that the gas accumulates either fastly or slowly and the system suffers outflows (open model)
    • c) We assume that the gas at t=o is primordial (no metals)
    • d) We assume that the gas at t=o is pre-enriched by Pop III stars
  • 7. Star Formation History
    • We define the stellar birthrate function as:
    • B(m,t) =SFRxIMF
    • The SFR is the star formation rate (how many solar masses go into stars per unit time)
    • The IMF is the initial stellar mass function describing the distribution of stars as a function of stellar mass
  • 8. Parametrization of the SFR
    • The most common parametrization is the Schmidt (1959) law where the SFR is proportional to some power (k=2) of the gas density
    • Kennicutt (1998) suggested k=1.5 from studying star forming galaxies, but also a law depending of the rotation angular speed of gas
    • Other parameters such as gas temperature, viscosity and magnetic field are usually ignored
  • 9. Kennicutt’s (1998) SFR
  • 10. Kennicutt’s law
  • 11. SF induced by spiral density waves
  • 12. SFR accounting for feedback
  • 13. The IMF
  • 14. How to derive the IMF
    • The current mass distribution of local MS stars per unit area, n(m), is called Present Day Mass Function (PDMF)
    • For stars in the range 0.1-1 Msun, with lifetimes > the age of the Galaxy, tG, we can write:
  • 15. How to derive the IMF
    • If the IMF is assumed to be constant in time, we can write:
  • 16. How to derive the IMF
    • For stars with lifetimes << tG (m> 2 Msun) we can see only the stars born after
    • Therefore, we can write:
  • 17. How to derive the IMF
    • If we assume the IMF is constant in time we can write:
    • Having assumed that the SFR did not change during the time interval corresponding to stellar lifetimes
  • 18. How to derive the IMF
    • We cannot apply the previous approximations to stars in the range 1-2 Msun
    • Therefore, the IMF is this mass range will depend on b(tG):
  • 19. Constraints on the SFH from the IMF
    • In order to obtain a good fit of the two branches of the IMF in the solar vicinity one needs to assume (Scalo 1986):
  • 20. The IMF
    • Upper panel: different IMFs
    • Lower panel: normalization of the multi-slope IMFs to the Salpeter IMF
    • Figure from Boissier & Prantzos (1999)
  • 21. How to derive the local SFR
    • An IMF should be assumed and then one should integrate the PDMF in time
    • Timmes et al. (1995), by adopting the Miller & Scalo (1979) IMF , obtained:
  • 22. The Infall law
    • The infall rate can simply be constant in space and time
    • Or described by an exponential law:
  • 23. The outflow law
    • The rate of gas loss from a galaxy through a galactic wind can be expressed as:
  • 24. The Yield per stellar generation
    • The yield per stellar generation of a single chemical element, can be defined as (Tinsley 1980):
    • Where p_im is the stellar yield and the instantaneous recycling approximation has been assumed
  • 25. Instantaneous Recycling Approximation
    • The I.R.A. states that all the stars with masses < 1 Msun live forever (and this is true) but also that the stars with masses > 1 Msun die instantaneously (and this is not true)
    • I.R.A. affects mainly the chemical elements produced on long timescales (e.g. N and Fe)
  • 26. The returned fraction
    • We define returned fraction the amount of mass ejected into the ISM by an entire stellar generation
    • Instantaneous recycling approximation (IRA) is assumed , namely stellar lifetimes of stars with M> 1 Msun are neglected
  • 27.
    • We call stellar yield the newly produced and ejected mass of a given chemical element by a star of mass m
    • Stellar yields depend upon the mass and the chemical composition of the parent star
    Stellar Yields
  • 28. Primary and Secondary elements
    • We define primary element an element produced directly from H and He
    • A typical primary element is carbon or oxygen which originate from the 3- alpha reaction
    • We define secondary element an element produced starting from metals already present in the star at birth (e.g. Nitrogen produced in the CNO cycle)
  • 29. Simple Model and Secondary Elements
    • The solution of the Simple model of chemical evolution for a secondary element Xs formed from a seed element Z
    • Xs is proportional to Z^(2)
    • Xs/Z goes like Z
  • 30. Primary versus secondary
    • Figure from Pettini et al. (2002)
    • Small dots are extragalactic HII regions
    • Red triangles are Damped Lyman-alpha systems (DLA)
    • Dashed lines mark the solution of the simple model for a primary and a secondary element
  • 31. Stellar Yields
    • Low and intermediate mass stars (0.8-8 Msun): produce He, N, C and heavy s-process elements. They die as C-O white dwarfs, when single, and can die as Type Ia SNe when binaries
    • Massive stars (M>8-10 Msun): they produce mainly alpha-elements, some Fe, light s-process elements and r-process elements and explode as core-collapse SNe
  • 32. Stellar Yields
    • Yields for Fe in massive stars (Woosley & Weaver 1995; Thielemann et al. 1996; Nomoto et al. 1997; Rauscher et al. 2002, Limongi & Chieffi 2003)
  • 33. Stellar Yields
    • Mg yields from massive stars
    • Big differences among different studies
    • Mg yields are too low to reproduce the Mg abundances in stars
  • 34. Stellar Yields
    • Oxygen yields from massive stars
    • Different studies agree on O yields
    • Oxygen increases continuously with stellar mass from 10 to 40 Msun
    • Not clear what happens for M>40 Msun
  • 35. Stellar Yields
    • New yield from Nomoto et al. (2007) for Oxygen in massive stars
    • They are computed for 4 different metallicities
  • 36. Stellar Yields
    • Yields of Fe from massive stars from Nomoto et al. (2007)
    • The yields are computed for 4 different metallicities
  • 37. Supernova taxonomy core collapse H I II Si Ia Ib Ic He IIP IIL phase phase light curve IIb early phase late IIn  line profile thermo nuclear Hypernovae = GRBs ? energy faint II luminosity
  • 38. Basic SN types Ia Ib II max. +10 months
  • 39. SN type ~ 10 53 ergs ~ 10 51 ergs total energy < 30 Myr 0.03 – 10 Gyr age 1 - 30 M O 1.4 M O Ejecta O, Mg, Si, Ne, Ca Fe composition neutron star (or BH) core-collapse thermo-nuclear Mechanism none Remnant 100% 5% ? realization single or binary massive star (> 8M O ) WD in binary system (M < 8M O ) Progenitor II+Ib/c Ia
  • 40. Kennicutt (1998) SFR and galaxy type
  • 41. Type Ia SN progenitors
    • Single-degenerate scenario Whelan & Iben 1974): a binary system with a C-O white dwarf plus a normal star. When the star becomes RG it starts accreting mass onto the WD
    • When the WD reaches the Chandrasekhar mass it explodes by C-deflagration as Type Ia supernova
  • 42. Type Ia SN progenitors
    • Double-Degenerate scenario (Iben & Tutukov, 1984): two C-O WDs merge after loosing angular momentum due to gravitational wave radiation
    • When the two WDs of 0.7 Msun merge, the Chandrasekhar mass is reached and C-deflagration occurs
    • The nucleosynthesis is the same in the two scenarios
  • 43. Single-Degenerate scenario
  • 44. DD-scenario
  • 45. The clocks for the explosions of SNe Ia
    • Single-Degenerate model: the clock to the explosion is given by the lifetime of the secondary star, m2. The minimum time for the appearence of the first Type Ia SN is tSNIa= 30Myr (the lifetime of a 8 Msun star)
    • Double-Degenerate model: the clock is given by the lifetime of the secondary plus the gravitational time-delay. tSNIa= 35 Myr + Delta_grav= 40 Myr
    • The maximum timescale is 10 Gyr in the SD
    • and several Hubble times in the DD
  • 46. Type Ia SN nucleosynthesis
    • A Chandrasekhar mass (1.44 Msun) explodes by C-deflagration
    • C-deflagration produces 0.6 Msun of Fe plus traces of other elements from C to Si
  • 47. Tycho SNR (type Ia) Chandra X-ray images color code: red .30-.95 keV, green .95-2.65 keV, blue 2.65-7.00 keV
  • 48. Type II SNe
    • Type II SNe arise from the core collapse of massive stars (M=8-40 Msun) and produce mainly alpha-elements (O, Mg, Si, Ca...) and some Fe
    • Stars more massive can end up as Type Ib/c SNe
  • 49. Summary of Nucleosynthesis
    • During the Big Bang light elements are
    • formed,
    • Spallation process in the ISM produces 6Li, Be and B
    • Supernovae II produce alpha-elements (O, Ne, Mg, S, S, Ca), some Fe, light s- and r-process elements
  • 50. Summary of Nucleosynthesis
    • Type Ia SNe produce mainly Fe and Fe-peak elements plus some traces of elements from C to Si
    • Low and intermediate mass stars produce
    • Deuterium is only destroyed to produce 3He which is also mainly destroyed
  • 51. The Simple model
    • The Simple Model of galactic chemical evolution
    • One-zone, closed -box model (no infall or outflow)
    • IMF constant in time
    • Instantaneous recycling approximation
    • Instantaneous mixing approximation
  • 52. Solution of the Simple Model
    • If we assume that Xi is the abundance by mass of an element i, we have:
    • where
  • 53. Simple model with outflow
  • 54. Simple model with infall
  • 55. Abundance ratios and Simple Models
    • Under the assumption of the I.R.A.
    • it is always true that the ratio of two abundances is equal to the ratio of the two corresponding yields:
  • 56. Models with no I.R.A.
    • When the I.R.A. Is relaxed then is NOT more true that the ratio between the abundances of two different elements is equal to the ratio of the corresponding yield!!
  • 57. Basic Equations
  • 58. Definitions of variables
    • dGi/dt is the rate of time variation of the gas fraction in the form of an element i
    • Xi(t) is the abundance by mass of a given element i
    • Qmi is a term containing all the information about stellar evolution and nucleosynthesis
  • 59. Definition of variables
    • A =0.05-0.09 is the fraction in the IMF of binary systems of that particular type to give rise to Type Ia SNe. B=1-A
    • Tau_m is the lifetime of a star of mass m
    • f(mu) is the distribution function of the mass ratio in binary systems
    • A(t) and W(t) are the accretion and outflow rate, respectively
  • 60. The Milky Way
  • 61. The Milky Way
  • 62. The formation of the Milky Way
    • Eggen, Lynden-Bell & Sandage (1962) suggested a rapid collapse lasting 300 Myr for the formation of the Galaxy
    • Searle & Zinn (1978) proposed a central collapse but also that the outer halo formed by merging of large fragments taking place over a timescale > 1Gyr
  • 63. Different approaches in modelling the MW
    • Serial approach: halo, thick and thin disk form as a continuous process (e.g. Matteucci & Francois 1989)
    • Parallel approach: the different galactic component evolve at different rates but they are inter-connected (e. G. Pardi, Ferrini & Matteucci 1995)
  • 64. Different approaches in modelling the MW
    • Two-infall approach: halo and disk form out of two different infall episodes (e.g. Chiappini, Matteucci & Gratton 1997; Alibes, Labay & Canal 2001)
    • Stochastic approach: mixing not efficient especially in the early halo phases (e.g. Tsujimoto et al. 1999; Argast et al. 2000; Oey 2000)
  • 65. A scenario for the formation of the Galaxy
    • The two-infall model of Chiappini, Matteucci & Gratton (1997) predicts two main episodes of gas accretion
    • During the first one the halo and bulge formed, the second gave rise to the disk
  • 66. The two-infall model
    • The two-infall model has been adopted also in other studies such as Chang et al.(1999) and Alibes et al. (2001)
    • In particular, Chang et al. applied the two-infall scheme to the thick and thin disk
    • Alibes et al. adopted the same scheme as Chiappini et al. (1997)
  • 67. Gas Infall at the present time
  • 68. Another scenario
    • The creation of the Milky way
    • Hera, flowed when she realized she had been giving milk to Heracles and thrust him away her breast
  • 69. Recipes for the two-infall model
    • SFR- Kennicutt’s law with a dependence on the surface gas density (exponent k=1.5) plus a dependence on the total surface mass density (feedback). Threshold of 7 solar masses per pc squared
    • IMF, Scalo (1986) normalized over a mass range of 0.1-100 solar masses
    • Exponential infall law with different timescales for inner halo (1-2 Gyr) and disk (inside-out formation with 7 Gyr at the S.N.)
  • 70. Recipes for the model
    • Type Ia SNe- Single degenerate model (WD+RG or MS star), recipe from Greggio & Renzini (1983) and Matteucci & Recchi (2001)
    • Minimum time for explosion 35 Myr (lifetime of a 8 solar masses star), confirmed by recent findings (Mannucci et al. 2005, 2006)
    • Time for restoring the bulk of Fe in the S.N. is 1 Gyr (depends on the assumed SFR)
  • 71. Solar Vicinity
    • We study first the solar vicinity, namely the local ring at 8 kpc from the galactic center
    • Then we study the properties of the entire disk from 4 to 22 Kpc
  • 72. Stellar Lifetimes
  • 73. The star formation rate (threshold effects)
  • 74. Stellar abundances
    • [X/Fe]= log(X/Fe)_star-log(X/Fe)_sun is the abundance of an element X relative to iron and to the Sun
    • The most recent accurate solar abundances are from Asplund et al. (2005)
    • Previous abundances from Anders & Grevesse (1989) and Grevesse & Sauval (1998)
    • The main difference is in the O abundance, now lower
  • 75. Predicted SN rates
    • Type II SN rate (blue) follows the SFR
    • Type Ia SN rate (red) increases smoothly (small peak at 1 Gyr)
  • 76. Time-delay model
    • Blue line= only Type II SNe to produce Fe
    • Red line= only Type Ia SNe to produce Fe
    • Black line: Type II SNe produce 1/3 of Fe and Type Ia SNe produce 2/3 of Fe
  • 77. Specific prediction by the two-infall model
    • The adoption of a threshold in the gas density for the SFR creates a gap in the SFR
    • This gap occurs between the halo-thick disk and the thin-disk phase
    • It is observed in the data
  • 78. G-dwarf distribution (Chiappini et al.)
  • 79. Different timescales for disk formation
  • 80. G-dwarf distribution(Alibes et al.)
  • 81. G-dwarf distribution
    • Chiappini et al. (1997) , Alibes et al. (2001) and Kotoneva et al. (2002) concluded that a good fit to the G-dwarf metallicity distribution can be obtained only with a time scale of disk formation at the solar distance of 7-8 Gyr
  • 82. Evolution of the element abundances
    • Chiappini et al. follow the evolution in space and time of 35 chemical species (H, D, He, Li, C, N, O, Ne, Mg, Si, S, Ca, Ti, K, Fe, Mn, Cr, Ni, Co, Sc, Zn, Cu, Ba, Eu, Y, La, Sr plus other isotopes)
    • They solve a system of 35 equations where SFR, IMF, nucleosynthesis and gas accretion are taken into account
    • Yields from massive stars WW95, from low-intermediate stars van den Hoeck+ Groenewegen 1997, from Type Ia SNe Iwamoto et al. 1999
  • 83. Results from Francois et al. 2004
  • 84. Results from Francois et al. 2004
  • 85. Results from Francois et al. 2004
  • 86. Corrected Yields
  • 87. Corrected Yields
  • 88. Corrected Yields
  • 89. Suggestions for the Yields
    • Yields from Woosley & Weaver 1995 (WW95), Iwamoto et al. (1999)
    • Major corrections for Fe-peak elements
    • O, Fe, Si and Ca are ok. Mg should be increased
  • 90. Inhomogeneous Model
    • Argast et al. (2000) computed 3-D hydrodynamical calculations following the evolution of SN remnants
    • No mixing was assumed for [Fe/H] > -3.0 dex, complete mixing for [Fe/H]> -2.0 dex
    • They predicted a too large spread for [Mg/Fe] and [O/Fe] vs. [Fe/H]
  • 91. Results from Alibes et al.
    • Alibes et al. (2001) adopted the two-infall model
    • Metallicity-dependent yields from WW95 and Van den Hoeck & Groenewegen (1997)
  • 92. Results from Chiappini et al.
    • Evolution of Carbon and Nitrogen as predicted by the two-infall model of Chiappini, Matteucci & Gratton (1997)
    • The green line in the N plot is an euristic model with primary N from massive stars
  • 93. Last data on Nitrogen
    • From Ballero et al. (2005)
    • It shows new data (filled circles and triangles) at low metallicity endorsing the suggestion that N should be primary in massive star
    • Stellar rotation can produce such N (Meynet & Maeder 2002)
  • 94. Last data on N and C
    • Primary nitrogen from rotating very metal poor massive stars
    • Models from Chiappini et al. (2006) (dashed lines)
    • Large squares from Israelian et al. 04; asterisks from Spite et al. 05; pentagons from Nissen 04
  • 95. s- and r-process elements
    • Data from Francois et al.(2006) with UVES on VLT
    • Models Cescutti et al. (2006): red line, best model, with Ba_s from 1-3 solar masses (Busso et al.01) and Ba_r from 10-30 solar masses
  • 96. Old Prescriptions
    • Travaglio et al.(1999) assumed Ba_r from 8-10 solar masses
    • The new data show a source of Ba_r from more massive stars is required
  • 97. s- and r- process elements
    • Data from Francois et al. (2006)
    • Models from Cescutti et al. (2006): red line, best model with Eu only r-process from 10-30 solar masses
  • 98. s- and r- process elements
    • Lanthanum- Data from:
    • Francois et al. (2006) (filled red squares), Cowan & al.(2005) (blue hexagons), Venn et al.(2004) (blue triangles), Pompeia et al.(2003) (green hexagons)
    • Models from Cescutti, Matteucci, Francois & Chiappini (2006): same origin as Ba
  • 99. Abundance Gradients
    • The abundances of heavy elements decrease with galactocentric distance
    • in the disk
    • Gradients of different elements are slightly different (depend on their nucleosynthesis and timescales of production)
    • Gradients are measured from HII regions, PNe, B stars, open clusters and Cepheids
  • 100. How does the gradient form?
    • If one assumes the disk to form inside-out, namely that first collapses the gas which forms the inner parts and then the gas which forms the outer parts
    • Namely, if one assumes a timescale for the formation of the disk increasing with galactocentric distance, the gradients are well reproduced
  • 101. Abundance gradients
    • Predicted and observed abundance gradients from Chiappini, Matteucci & Romano (2001)
    • Data from HII regions, PNe and B stars, red dot is the Sun
    • The gradients steepen with time (from blue to red)
  • 102. Abundance gradients
    • Predictions from Boissier & Prantzos (1999), no threshold density in the SF
    • They predict the gradient to flatten in time
    • The difference is due to the effect of the threshold
  • 103. Abundance Gradients
    • New data on Cepheids from Andrievsky & al.(02,04) (open blue circles)
    • Red triangles-OB stars from Daflon & Cunha (2004)
    • Blue filled hexagons, Cepheids from Yong et al.(2006), blue open triangles from Young et al. 05, cian data from Carraro et al.(2004)
  • 104. Different halo densities
    • Only Cepheids data from Andrievsky
    • Blue dot-dashed line: model with halo density decreasing outwards
    • Red continuous line (BM):model with halo constant density
  • 105. Abundance Gradients
    • Blue filled hexagons from open Cepheids (Yong et al. 2006)
    • Cian data from open clusters (Carraro et al. 2004), open triangles are open clusters
    • Black data from Cepheids (Andrievsky et al., 2002,04)
    • Dashed lines=prediction for 4.5 Gyr ago
  • 106. Abundance Gradients
    • Blue filled hexagons from Andrievsky & al.(02,04)
    • Red squares are the average values
    • For Barium there are not yet enough data to compare
  • 107. The Galactic Bulge
    • A model for the Bulge (green line, Ballero et al. 2006)
    • Yields from Francois et al. (04), SF efficiency of 20 Gyr^(-1), timescale of accretion 0.1 Gyr
    • Data from Zoccali et al. 06, Fulbright et al. 06, Origlia &Rich (04, 05)
  • 108. The Galactic Bulge
    • Model (red, Ballero et al. 2006)
    • Predicts large Mg to Fe for a large Fe interval
    • Turning point at larger than solar Fe. Mg flatter than O
    • Data from Zoccali et al. 06; Fulbright et al. 06, Origlia & Rich (04, 05)
  • 109. The Galactic Bulge
    • Metallicity Distribution of Bulge stars, data from Zoccali et al. (2003) and Fulbright et al. (2006) (dot-dashed)
    • Models from Ballero et al. 06, with different SF eff.
  • 110. The Galactic Bulge
    • Models with different IMF
    • The best IMF for the Bulge is flatter than in the S.N: and flatter than Salpeter
    • Best IMF: x=0.95 for M> 1 solar mass and x=0.33 below
  • 111. Bulge vs. Thick and Thin Disk Stars
    • Zoccali et al. (2006) compared new high resolution data for the Bulge (green dots and red crosses) with data for thick disk (yellow triangles) and thin disk (blue crosses)
    • The Bulge stars are systematically more overabundant in O
  • 112. Other Bulge Models
    • Molla, Ferrini & Gozzi (2000): the Bulge formed by collapse but with a more prolonged star formation history
    • They failed in reproduding [Mg/Fe]
  • 113. Other Bulge Models
    • Immeli et al. (2004) computed dynamical simulations for the formation of the Bulge
    • They studied the efficiency of energy dissipation and different SF histories
    • Model B assumes an early and fast SFR
  • 114. Comparison with data
    • Comparison between the B, D and F models of Immeli et al. (2004) with data from Zoccali et al. (2006)
    • The best model predicts a very fast Bulge formation
    • However, Immeli’s models have a fixed delay for Type Ia SNe
  • 115. Conclusions on the Bulge
    • The best model for the Bulge suggests that it formed by means of a strong starburst
    • The efficiency of SF was 20 times higher than in the rest of the Galaxy
    • The IMF was very flat, as it is suggested for starbursts
    • The timescale for the Bulge formation was 0.1 Gyr and not longer than 0.5 Gyr
  • 116. Conclusions on the Milky Way
    • The Disk at the solar ring formed on a time scale not shorter than 7 Gyr
    • The whole Disk formed inside-out with timescales of the order of 2 Gyr in the inner regions and 10 Gyr in the outer regions
    • The inner halo formed on a timescale not longer than 2 Gyr
    • Gradients from Cepheids are flatter at large Rg than gradients from other indicators
  • 117. Dwarf Spheroidals of the Local Group
  • 118. SF and Hubble Sequence from Sandage
  • 119. SF and HS from Kennicutt
  • 120. Models for the Hubble Sequence
  • 121. Type Ia SN rate in galaxies
  • 122. Timescales for Type Ia SNe enrichment
    • The typical timescale for the Type Ia SN enrichment is the maximum in the Type Ia SN rate (Matteucci & Recchi 2001)
    • It depends on the star formation history of a specific galaxy, IMF and stellar lifetimes
  • 123. Typical timescales for SNIa
    • In ellipticals and bulges the timescale for the maximum enrichment from Type Ia SNe is 0.3-0.5 Gyr
    • In the solar vicinity there is a first peak at 1 Gyr, then it decreases slightly (gap in the SF) and increases again till 3 Gyr
    • In irregulars the peak is for a time > 4 Gyr
  • 124. Time-delay model in different galaxies
  • 125. Interpretation of time-delay model
    • Galaxies with intense SF (ellipticals and bulges) show overabundance of alpha-elements for a large [Fe/H] range
    • Galaxies with slow SF (irregulars) show instead low [alpha/Fe] ratios at low [Fe/H]
    • The SFR determines the shape of the [alpha/Fe] vs. [Fe/H] relations
  • 126. Identifying high-z objects
    • Lyman-break galaxy cB58, data from Pettini et al. 2002
    • The model predictions are for an elliptical galaxy of 10^(10) Msun (Matteucci & Pipino 2002)
  • 127. Dating high-z objects
    • The Lyman-break galaxy cB58
    • Predicted abundance ratios versus redshift
    • The estimated age is 35 Myr
  • 128. Conclusions on high-z objects
    • Comparison between data and abundance ratios of high-z objects suggests:
    • DLA are probably dwarf irregulars or at most external parts of disks
    • Lyman-break galaxies are probably small ellipticals in the phase of galactic wind
  • 129. How do dSphs form?
    • CDM models for galaxy formation predict dSph systems (10^7 Msun) to be the first to form stars (all stars should form < 1Gyr)
    • Then heating and gas loss due to reionization must have halted soon SF
    • Observationally, all dSph satellites of the MW contain old stars indistinguishable from those of Galactic globular clusters and they have experienced SF for long periods (>2 Gyr, Grebel & Gallagher, 04)
  • 130. Chemical Evolution of Dwarf Spheroidals
    • Lanfranchi & Matteucci (2003, 2004) proposed a model which assumes the SF as derived by the CMDs
    • Initial baryonic masses 5x10^(8)Msun
    • A strong galactic wind occurs when the gas thermal energy equates the gas potential energy. DM ten times LM but diffuse (M/L today of the order of 100)
    • The wind rate is assumed to be several times the SFR
  • 131. Standard Model of LM03
    • LM03 computed a standard models for dwarf spheroidals
    • They assumed 1 long star formation episode (8 Gyr), a low star formation efficiency <1 Gyr^(-1)
    • They assumed that galactic winds are triggered by SN explosions at rates > 5 times the SFR . The final mass is 10^(7)Msun
    • The IMF is that of Salpeter (1955)
  • 132. Galactic winds
    • LM03 included the energetics from SNe and stellar winds to study the occurrence of galactic winds, the condition for the wind being:
    • Dark matter halos 10 times more massive than the initial luminous mass (5x10^(8) Msun) but not very concentrated (see later)
  • 133. The binding energy of gas
  • 134. The binding energy of gas
  • 135. Binding energy of gas
    • S is the ratio between the effective radius of the galaxy and the radius of the dark matter core
    • We assume S=0.10 in dSphs
  • 136. DM in Dwarf Spheroidals
    • Mass to light ratios vs. Galaxy absolute V magnitude (Gilmore et al. 2006)
    • The solid curve shows the relation expected if all the dSphs contain about 4x10^(7) Msun of DM interior to their stellar distributions
    • No galaxy has a DM halo < 5x10^(7)Msun
  • 137. DM in dSphs
    • Mass to light ratios in dSphs from Mateo et al. (1998)
    • In the bottom panel the visual absolute magnitude has been corrected for stellar evolution effects
    • The Sgr point is an upper limit
  • 138. Galactic Winds
    • The energy feedback from SNe and stellar winds in LM03 is:
    • SNe II inject 0.03 Eo (Eo is the initial blast wave energy of 10^(51) erg )
    • SNe Ia inject Eo since they explode when the gas is already hot and with low density (Recchi et al. 2001)
    • Stellar winds inject 0.03 Ew (Ew is 10^(49) erg)
  • 139. Gas Infall and Galaxy Formation
    • LM03 assumed that each galaxy forms by infall of gas of primordial chemical composition
    • The formation occurs on a short timescale of 0.5 Gyr
  • 140. Standard Model of LM03
    • Standard Model: SF lasts for 8 Gyr, strong wind removes all the gas
    • Different SF eff. and wind eff. are tested, from 0.005 to 5 Gyr^(-1) for SF and from (6 to 15) xSF for the winds
  • 141. Abundance patterns
    • It is evident that the [alpha/Fe] ratios in dSphs show a steeper decline with [Fe/H] than in the stars in the Milky Way
    • This is the effect of the time-delay model, namely of a low SF efficiency coupled with a strong galactic wind
    • After the wind SF continues for a while
  • 142. Individual galaxies
    • Then LM03,04 computed the evolution of 6 dSphs: Carina, Sextan, Draco, Sculptor, Sagittarius and Ursa Minor
    • They assumed the SF histories as measured by the Color-Magnitude diagrams (Mateo, 1998;Dolphin 2002; Hernandez et al. 2000; Rizzi et al. 2003)
  • 143. Star Formation Histories in LM03
  • 144. SF histories of dSphs (Mateo et al. 1998)
  • 145. Individual galaxies
  • 146. Dwarf Spheroidals : Carina
    • Model Lanfranchi & Matteucci (04,06)
    • SF history from Rizzi et al. 03. Four bursts of 2 Gyr, SF efficiency 0.15 Gyr^(-1) < 1- 2 Gyr^(-1) (S.N.), wind=7xSFR
    • Salpeter IMF
  • 147. Predicted C and N in Carina
    • Predicted evolution of C and N for Carina’s best model
    • The continuous line is for secondary N in massive stars
    • The dashed line assumes primary N from massive stars
  • 148. Metallicity distribution in Carina
    • Data from Koch et al. (2005)
    • Best model from Lanfranchi & al. (2006)
    • This model well reproduces also the [alpha/Fe] ratios in Carina
  • 149. Dwarf Spheroidals: Draco
    • Model and data for Draco
    • SF history, 1 burst of 4 Gyr, SF efficiency of 0.03 Gyr^(-1)
    • Wind=6xSFR
    • Salpeter IMF
  • 150. Draco’s metallicity distribution
    • Predicted metallicity distribution for Draco compared with the predicted metallicity distribution for the Solar Vicinity
  • 151. Dwarf Spheroidals: Sextans
    • Best Model: 1 burst of 8 Gyr
    • SF efficiency 0.08 Gyr^(-1)
    • Wind=9xSFR
    • Salpeter IMF
  • 152. Sextans: metallicity distribution
    • Predicted metallicity distribution for Sextans by LM04
    • The predicted G-dwarf metallicity distribution for Solar Vicinity stars is shown for comparison
  • 153. Dwarf Spheroidals: Ursa Minor
    • Best Model: 1 burst of 3 Gyr
    • SF efficiency 0.2 Gyr^(-1)
    • Wind=10xSFR
    • Salpeter IMF
  • 154. Ursa Minor’s metallicity distribution
    • Predicted metallicity distribution for Ursa Minor by LM04
    • The predicted G-dwarf metallicity distribution for the solar vicinity is shown for comparison
  • 155. Dwarf spheroidals: Sagittarius
    • Best model:one long episode of SF of duration 13 Gyr (Dolphin et al 2002)
    • SF eff. Like the S.N., but very strong wind 9XSFR
  • 156. Metallicity distribution in Sagittarius
    • Predicted metallicity distribution by LM04 for Sagittarius: continuous line (Salpeter IMF), dashed line (Scalo IMF)
    • The predicted G-dwarf metallicity distribution for the solar vicinity is shown by the dotted line
  • 157. Dwarf Spheroidals: Sculptor
    • Model and data for Sculptor
    • SF efficiency 0.05-0.5 Gyr^(-1), wind 7 XSFR
    • One long SF episide lasting 7 Gyr
    • Salpeter IMF
  • 158. Sculptor’s metallicity distribution
    • Predicted metallicity distribution in Sculptor (LM04)
    • The predicted G-dwarf metallicity distribution for the solar vicinity is shown for comparison
  • 159. s- and r- process elements in dSphs
    • Lanfranchi et al. 2006 adopted the nucleosynthesis prescriptions for the s- and r- process elements as in the S.N.
    • They calculated the evolution of the [s/Fe] and [r/Fe] ratios in dSphs
    • They predicted that s-process elements, which are produced on long timescales are higher for the same [Fe/H] in dSphs
  • 160. Model and data for Carina
  • 161. Model and data for Draco
  • 162. Model and data for Sextans
  • 163. Model and data for Sculptor
  • 164. Model and data for Sagittarius
  • 165. Sagittarius: more data
    • Best model is continuous line. Dotted lines are different SF efficiencies
    • Dashed line is the best model with no wind
    • The strong wind compensate the high SF efficiency
    • Data from Bonifacio et al. 02,04 & Monaco et al. 05 (open squares)
  • 166. C and N in Sagittarius: predictions
  • 167. Other Models for dSphs
    • Carigi, Hernandez & Gilmore (2002) computed models for 4 dSphs by assuming SF histories derived by Hernandez et al. (2000)
    • They assumed gas infall and computed the gas thermal energy to study galactic winds
    • They assumed a Kroupa et al.(1993) IMF
  • 168. Carigi et al. (2002)
    • They assumed only a sudden wind which devoids the galaxy from gas instantaneously
    • They predicted a too high metallicity for dSphs and not the correct slope for [alpha/ Fe] ratios
  • 169. Carigi et al’s predictions for Ursa Minor
  • 170. Model of Ikuta & Arimoto (2002)
    • They adopted a closed model (no infall, no outflow)
    • They suggested a very low SFR such as that of LM03, 04
    • They had to invoke external mechanisms to stop the SF
    • They assumed different IMFs
  • 171. Ikuta & Arimoto (2002)
  • 172. Model of Fenner et al. 2006
    • Very similar to the model of LM03, 04 with galactic winds for Sculptor
    • They suggest 0.05 Gyr^(-1) as SF efficiency
    • Their galactic wind is not as strong as the winds of LM03, 04
    • They conclude that chemical evolution in dSphs is inconsistent with SF being truncated after reionization epoch (z = 8)
  • 173. Comparison between dSphs and MW
    • Blue line and blue data refer to Sculptor
    • Red line and red data refer to the Milky Way
    • The effect of the time-delay model is to shift towards left the model for Sculptor with a lower SF efficiency than in the MW
  • 174. Comparison dSph and MW
    • Eu/Fe in Sculptor and the MW
    • Model and data for Sculptor are in blue
    • Model and data for the MW are in red
  • 175. Conclusions on dSphs
    • By comparing the [alpha/Fe] ratios in the MW and dSphs one concludes that they had different SF histories
    • The [alpha/Fe] ratios in dSphs are always lower than in the MW at the same [Fe/H], as a consequence of the time delay model and strong galactic wind
  • 176. Conclusions on dSphs
    • Very good agreement both for [alpha/Fe] and [s/Fe] and [r/Fe] ratios is obtained if a less efficient SF than the S.N. one and a strong wind are adopted
    • It is unlikely that the dSphs are the building blocks of the MW
    • Interactions between the MW and its satellites are not excluded but they must have occurred after the bulk of stars of dSphs was formed
  • 177. Other spirals
  • 178. Results for M101 (Chiappini et al. 03)
  • 179. Results for M101
  • 180. Properties of spirals (Boissier et al. 01)
  • 181. Conclusions on Spirals
  • 182. [SII] red, [OIII] green, [OI] blue N132D in LMC oxygen rich SN remnant
  • 183. How to search SN 1998dh
    • Compare images taken at different epochs
    • few days < time interval < 1-2 month
    • 14 < limiting magnitude < 24
    • 0.01 < target redshift < 1
    • 5 arcmin < field of view < 1 deg
    • B-V < band < R-I
  • 184. SN search target reference - SN 2000fc type Ia z = 0.42 V=22.4 IAUC7537 difference =
  • 185. SN distribution in galactic coordinates
  • 186. SN rate with redshift Madau, Della Valle & Panagia 1998 On the evolution of the cosmic supernova ra te Sadat et al. 1998 A&A 331, L69 Cosmic star formation and Type Ia/II supernova rates at high Z Yungelson & Livio 2000 ApJ 528, 108 Supernova Rates: A Cosmic History Kobayashi et al. 2000 ApJ 539, 26 The History of the Cosmic Supernova Rate Derived from the Evolution of the Host Galaxies Sullivan et al. 2000 MNRAS 319, 549 A strategy for finding gravitationally lensed distant supernovae Dahlèn & Fransson 1999 A&A 350, 349 Rates and redshift distributions of high-z supernovae Calura & Matteucci 2003 ApJ 596, 734 τ =3Gy 1Gy 0.3Gy Madau, Della Valle & Panagia 1998 MNRAS 297, L17
  • 187. Zampieri et al. (2003) MNRAS 338, 711 NS BH GRBs Astrophysics : massive star evolution