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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

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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

Shanghai Astronomical Observatory, CAS


A short introduction of our group

Astronomical Mansion

Shanghai Astronomical Observatory, CAS

  • Star Clusters and the Structure of Galaxies


  • 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


  • 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


  • 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)


Some group members


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


  • Local SFR Law in the Milky Way disk based on abundance gradient evolution


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

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

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 


The evolution of abundance gradient along the Milky Way disk

Infall

SF Law

Model A, B

Model C


Fu, Hou, Chang et al. 2009


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 )


  • Observed differences between M31 and MWG


M31 and MWG have similar mass and morphology


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?

  • 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

Total disk SFR

MW

M31

Yin, Hou, Chang et al. 2009


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

MW

MW

Gas

SFR

M31

M31

Gas

fraction


  • Model comparisons between M31 and Milky Way 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

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

  • 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

  • Gas profile

  • SFR profile

  • Abundance gradient

  • Do the similar chemical evolution models reproduce the global properties for the Milky Way and M31 disks ?


SFR


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


Simulation

Observed

M32

Two rings

structure

Block et al. (Nature 2006)


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.


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)


Comparison among MW, M31 and M33


Thanks


Observed difference between M31 and Milky Way galaxies


Halo properties

Metal - Velocity

Tully-Fish Relation

SDSS: 1047 edge-on spirals

Hammer et al. 2007


Halo properties

X

X -- M33

Metallicity – luminosity relation

Mouhcine et al. 2005


Disk scale length

M31 distance: 785kpc

Band Observed scale length ( kpc )

M31 the Milky Way

U7.7

B6.6 4.0-5.0

V6.0

R5.52.3-2.8

I5.7

K4.8

L6.1

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


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

  • 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

  • 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

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

Phenomenological Model

  • Two time scales:

    • hdepends on the halo formation mechanism

    • das a function of radius, disk formation

Halo Disk delayed by tdelay


Star formation: Kennicutt law

Halo

Disk


Chemical evolution

Gas of an elementi

Gas depletion

Low mass

SNIa

IMS star

SNII

Halo and disk


K dwarf

Halo


Halo :

Disk :

Disk and halo surface density profile

Disk : exponential

Halo: modified Hubble law


Metallicity Distribution in the MW Disk and Halo


Infall Model

Phenomenological Model

  • Two time scales:

    • hdepends on the halo formation mechanism

    • das a function of radius, disk formation

Halo Disk delayed by tdelay


Rudolph et al. 2006

[O/H] gradient from young objects in theMilky Way Disk

-0.07 dex / kpc


Halo Globular Clusters

Number distribution

 Double peak

Number:

 M31: 700

 MW: 162


[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

  • 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 ?

  • 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 ?


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