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KIAA/PKU -- IoA workshop “Near Field Cosmology” Beijing, Dec 1-5, 2008 Star Formation and Chemical Evolution of the Milky Way and M31 Disks Jinliang HOU In collaboration with : Ruixiang CHANG, Jun YIN, Jian FU, Li CHEN, Shiyin SHEN et al. Center for Galaxy and Cosmology

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kiaa pku ioa workshop near field cosmology beijing dec 1 5 2008
KIAA/PKU --IoA workshop “Near Field Cosmology”Beijing, Dec 1-5, 2008

Star Formation and Chemical Evolution of the Milky Way and M31 Disks

Jinliang HOU

In collaboration with :

Ruixiang CHANG, Jun YIN, Jian FU,

Li CHEN, Shiyin SHEN et al.

Center for Galaxy and Cosmology

Shanghai Astronomical Observatory, CAS

a short introduction of our group
A short introduction of our group

Astronomical Mansion

Shanghai Astronomical Observatory, CAS

  • Star Clusters and the Structure of Galaxies
slide3

Research interests of the group

  • Structure and evolution of galaxies
  • ---- from the Milky Way to high z galaxies
  • Star clusters and the structure of the Milky Way Galaxy
  • Chemical evolution of the galaxies, high-z galaxies (mainly Damped Lyman Alpha systems)
  • Structure and dynamics of the nearby galaxies
  • Large sample analysis of the nearby galaxies(SDSS, Galex, 2MASS, LAMOST et al. )
  • Galaxy formation and evolution
slide4

Staff

  • HOU Jinliang
  • CHEN Li
  • SHAO Zhenyi (now in UMASS, USA)
  • CHANG Ruixiang
  • SHEN Shiyin
  • Senior Professors:
  • ZHAO Junliang
  • FU Chenqqi
  • WANG Jiaji
  • PhD students:
  • YIN Jun
  • LIU Chenzhe
  • SHI Xihen
  • GAO Xinhua
  • Wang Caihong
  • GAN Jinalin (now in Heideberg, MPIA),
  • HAN Xuhui (now in Paris Observatoire)
  • FU Jian (now in Munich, MPA)
  • MS Students:
  • YU Jinchen
  • WANG Youfen
slide5

Some international collaborators:

  • White S.D.M, Kauffmann G. (MPA)
  • Prantzos N. (IAP)
  • Boissier S. (Observatoire de Marseille)
  • Tytler D. (UCSD)
  • Mo Houjun (UMASS)
  • Levshakov S. (Ioffe Institute of Physical Technique)
  • de Grijs R. (U. Sheffield)
slide7

Content

  • Local SFR Law in the Milky Way disk based on abundance gradient evolution
  • Observed differences between M31 and MW disks
  • Model comparisons between M31 and Milky Way disks
  • Summary
kennicutt law average properties
Kennicutt Law --- average properties

Strong correlation between the average gas mass surface density and SFR density for nearby disk and starburst galaxies (Kennicutt 1998)

two types of correlations
Two types of correlations

The later form implies SFR depends on the angular frequency of the gas in the disk. This suggestion is based on the idea that stars are formed in the galactic disk when the ISM with angular frequency Omega is periodically compressed by the passage of the spiral pattern.

applications of kennicutt sfr law
Applications of Kennicutt SFR law

When the Kennicutt law is applied in the detailed studies of galaxy formation and evolution, there are several formulism that often adopted by the modelers :

SFR 

adoption of sfr law for the chemical evolution model of spiral galaxies
Adoption of SFR Law for the chemical evolution model of spiral galaxies
  • For the average properties of a galaxies, KS law is OK
  • For local properties, SFR could be local dependent, a simple description is the introducing of angular velocity (Silk 1997, Kennicutt 1998 )
slide17

Components in the Milky Way Galaxy

dark halo

stellar halo

thick disk

thin disk

bulge

We would like to understand how our Galaxy came to looklike this.

the milky way typical or not
The Milky Way, typical or not?
  • It is always regarded that the MWG is the typical spiral in the universe, especially at its mass range.
  • Is this true?
  • How about M31 galaxy, it is a spiral that is comparable with MWG in the Local Group, and now it is possible to have detailed observations.
disk profiles
Disk Profiles

Total disk SFR

MW

M31

Yin, Hou, Chang et al. 2009

o h gradient from young objects

Two gradients reported:

Steep: -0.07 dex / kpc

(Rudolph et al. 2006 )

Flat: -0.04 dex/kpc

(Deharveng et al. 2000

Dalfon and Cunha 2004)

[O/H]gradient from young objects

Scaled gradient

MWD:-0.161

-0.093

M31 :-0.094

-0.017 dex / kpc

scaled profiles
Scaled profiles

MW

MW

Gas

SFR

M31

M31

Gas

fraction

purpose of the chemical evolution study for the milky way and m31 disks
Purpose of the chemical evolution studyfor The Milky Way and M31 disks

Using the same model

  • Find common features
  • Find which properties are galaxy dependent
  • M31 and MWG, which one is typical ?
model classification
Model classification

Phenomenological Model /

Semi-Analytical Model

Disk only :

One component : Disk (Hou et al.)

Two components : Thick Disk + Thin Disk (Chang et al.)

Disk+Halo:

Two components : Disk +Halo

Three components : Thick Disk + Thin Disk + Halo

Disk+Halo+Bulge:

Three components : Bulge+Disk+Halo

unified one component model
Unified One Component Model
  • Disk forms by gas infall from outer dark halo
  • Infall is inside-out
  • SFR:
    • modified KS Law (SFR prop to v/r)
radial profiles as constrains
Radial Profiles as constrains
  • Gas profile
  • SFR profile
  • Abundance gradient
  • Do the similar chemical evolution models reproduce the global properties for the Milky Way and M31 disks ?
m31 gas and sfr in disk
M31 gas and SFR in disk
  • Observed of gas and SFR profiles are abnormal when compared with Kennicutt law.
  • Gas and SFR must be modified by some interaction
slide29

Simulation

Observed

M32

Two rings

structure

Block et al. (Nature 2006)

summary m31 disk properties
Summary : M31 disk properties
  • Current star formation properties are atypical in the M31 disk.
    • Disk formation be affected by interactions
  • Has low SFR in disk

 shorter time scale for the infall.

 contradicts the longer infall time scale for halo.

slide31
Problems
  • Chemical evolution model cannot reproduce the outer profiles of gas surface density and SFR profiles at the same time
  • The observed abundance gradient along the Milky Way disk still not consistent
  • The evolution of gradients is very important.

Two tracers :

      • PN (Maciel et al. 2003, 2005, 2006, 2007) and
      • Open Clusters (LAMOST Survey, CHEN Li’s talk, this workshop)
slide36

Halo properties

Metal - Velocity

Tully-Fish Relation

SDSS: 1047 edge-on spirals

Hammer et al. 2007

slide37

Halo properties

X

X -- M33

Metallicity – luminosity relation

Mouhcine et al. 2005

slide38

Disk scale length

M31 distance: 785kpc

Band Observed scale length ( kpc )

M31 the Milky Way

U 7.7

B 6.6 4.0-5.0

V 6.0

R 5.5 2.3-2.8

I 5.7

K 4.8

L 6.1

Note: SDSS average rd = 4.75kpc (Pizagno et al. 2006)

slide39

Disk specific angular momentum (AM)

Hammer et al. 2007

AM prop to rdVrot

(Mo et al. 1998)

MW is about a factor

of 2 less than nearby

spirals

observation which galaxy is a typical spiral statistical
Observation: which galaxy is a “typical” spiral? Statistical
  • M31 : metal-rich halo
  • MWG: metal-poor halo
  • Zibetti et al. (2004) from SDSS survey: 1000 edge-on disc galaxies, metal-rich halo is more common.
  • Harris & Harris (2001) NGC5128 similar to M31 halo

Metal-rich seems more common

  • How halo forms ? Why metal-rich ?
  • Does observed halo really halo?
observational constrains in the solar neighborhood
Observational constrains in the solar neighborhood
  • Find a set of parameters that can best reproduce some observational constrains in the solar neighborhood.
  • Observables of the Milky Way Galaxy
    • MDF (Metallicity Distribution Function)

disk and halo

    • [O/Fe] versus [Fe/H] from metal poor to metal rich
    • SFR at present time
physics of the model gas infall and star formation proceeds in each ring
Physics of the model : Gas infall and star formation proceeds in each ring

Rings independent

  • Solar neighborhood
  • Gas fraction
  • Abundance ratio
  • [O/Fe] ~[Fe/H]
  • G-dwarf metallicity etc.

Physical process

  • Disk profile
  • Gas
  • SFR
  • Abundance gradients
  • other global quantities
infall model
Infall Model

Phenomenological Model

  • Two time scales:
    • h depends on the halo formation mechanism
    • d as a function of radius, disk formation

Halo Disk delayed by tdelay

chemical evolution
Chemical evolution

Gas of an elementi

Gas depletion

Low mass

SNIa

IMS star

SNII

Halo and disk

slide47
Halo :

Disk :

Disk and halo surface density profile

Disk : exponential

Halo: modified Hubble law

infall model49
Infall Model

Phenomenological Model

  • Two time scales:
    • h depends on the halo formation mechanism
    • d as a function of radius, disk formation

Halo Disk delayed by tdelay

halo globular clusters
Halo Globular Clusters

Number distribution

 Double peak

Number:

 M31: 700

 MW: 162

fe h gradient from open clusters in the milky way disk

[Fe/H] gradient from Open Clustersin the Milky Way disk

Chen, Hou, Wang (2003)

All Open Clusters :age mixed

-0.063dex/kpc

summary 2 possible correlation between halo z and mstar
Summary – 2 : possible correlation between halo Z and Mstar
  • Model predicts more massive stellar halo in M31, about 6 to 9 times than that of MW halo.
  • Massive halo has higher metallicity.

Bekki, Harris & Harris (2003) simulation :

Stellar halo comes from the outer part of the progenitor discs when the bulge is formed by a major merger of two spirals.

 Correlation between halo metallicity and bulge mass

what we can do next for m31
What we can do next for M31 ?
  • Similar model, at present, we only concentrate on disk
  • Need to include halo also, a lot of observations are available for the halo, especially in the field of globular clusters.
  • To add the color evolution, this is important to constrain the model, is it possible to consistent between chemical and color ?
  • To solve the problem of low gas density in the outer disk, introduce new assumption ?
    • Higher outer disk SFE ?
    • Wind in the outer disk ?
    • Interaction ?