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The Chemical and Color Evolution of M33

The Chemical and Color Evolution of M33

2008.12

Reporter: Jun Yin (Shao) Supervisor: Jinliang Hou (Shao)

Contents

Observations1

Models2

Results & Forming History3

Summary4

Observation

Sc II-III, i=56, D=840 kpc Mtot=5~8×109M⊙

rd,tot=2.4kpc, rd,*~1.4kpc no merger

wholewhole

gas & SFRgas & SFR

abundanceabundance

SB, colorSB, color

Observation H2,tot=0.2×109M⊙, HItot=2.2×109M⊙

rd,H2=2.5kpc, rd,tot=7.8kpcwholewhole

gas & SFRgas & SFR

abundanceabundance

SB, colorSB, color

Observation

wholewhole

gas & SFRgas & SFR

abundanceabundance

SB, colorSB, color

Observation

Munoz-Mateos et al. (2007)

MFUV = -16.63 (GALEX) MK = -21.78 (2MASS)

wholewhole

gas & SFRgas & SFR

abundanceabundance

SB, colorSB, color

Chemical & Color Evolution Model

Star Formation Rate

Gas Infall Rate

Outflow……

mass

SFR

Z, MDF

color

……

stella

r evolu

tion

th

eory

Initia

l co

nditio

ns

Model

fout~b·Ψ, Zout=Z(t)

Ψ~(Σgas)1.4 r -1

fin~t·exp(-t/τ), Zin=0

td=a·r Gyr

Mtot=7×109M⊙, rd,tot=2.2kpc

Σtot(r)=230*exp(-r/rd,tot)TotalTotal

SFRSFR

Infall rateInfall rate

OutflowOutflow

Results & Forming History

Does M33 form quickly ? if τsmall infall quick gas ， SFR low stellar disk big abundance high, steep SB dark, color red

NONO

τ= r+5 Gyrτ= r+5 Gyr

Results & Forming History

Does infall delay at outer part ? if td large infall late

gas fraction high stellar disk small

abundance low, steep

color blue, steep

Not necessaryNot necessary

td = 0 Gyrtd = 0 Gyr-0.015-0.022-0.034

μr= 23.2 mag arcsec-2

Gkpc= -0.016

Results & Forming History

Does gas flow out ? if b large outflow large gas, SFR, star do not

change much abundance low, flat color a little flatter

YES !YES !

b=1.0b=1.0

-0.020-0.017-0.015

μr= 23.2 mag arcsec-2

Gkpc= -0.016

Results & Forming History

MDF & evolution of some global variables in our best model τ= r+5 Gyr td = 0 Gyr b= 1.0

Summary

M33 should be forming though slow accretion process, i.e. longer infall time scale.

The whole disk should form simutaneously, no obvious infall delay at outer disk.

Outflow is not negligible because of its low metallicity.

The M33 should obey similar SF law with our Galaxy.

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