M82 as Playground for Galaxy and Star Formation

Wing-Huen IpInstitute of Astronomy

National Central University

Weihai, August 11, 2005

Outline

•Introduction•Star Formation History – Density Wave vs. SSPSF•M82 – A Prototype of Starburst Galaxy•M82 – Dusty Superwind and H Cap•Disk-Halo Interaction•Massive Coronas of Galaxies•Summary

Learning from BATC

• Juei-Hua Hu: NGC 2168 (Exoplanets/V*)

NGC 381 V*

SLT 20-cm (Exoplanets/V*)• Zhong-Yi Lin: Comets Q2; 9P/Tempel 1 (Deep Impact)• Chia-Hao Hsia: H imaging of PNe (also 2.16 m)

H imaging of nearby galaxies (LOT) to compare

with 2Mass NIR data

NGC 6946

From Yi-Tong Chen

Large-scaled Star Formation Process

• Density Wave Theory: Orbital velocity pattern plus gas density enhancement at spiral arms

• Stochastic Self-Propagating Star Formation: Pressure waves generated by supernovae or massive stars plus differential rotation

Test Cases

• Dwarf galaxies (no spiral arms)

• Starburst galaxies (nuclear regions)

• Both types provide information on star formation and galaxy building processes in early universe (Lyman forests with metal absorption lines -> massive coronas ….)

The Rosette Nebula

30 Doradus in LMC

Henize 70 in LMC

2.3 Elephant Trunk of the Rosette Nebula

LOTKenboo WuNCU

http://amundsen.swarthmore.edu/SHASSA/

Diffuse Ionized Gas (DIG) or Reynold Layer

H emission 11 Kpc above M82Devine and Bally (1999)

Continuous H emission out to11-12 kpc from nuclues until a cap-like structure

Shell-like feature (colliminated super-wind?) with blueshifted speed of50-200 km/s

Formation of bow shock from theexpansion of the superwind?

Question: Any similar structure inother wavelengths (BATC obs.?)

Other Important Obs.

• Very extended soft X-ray emission in good correlation with H emission (kT = 0.87 keV); Lehnert et al., 1999; Stevens et al., 2004

• Shock heating (galactic superwind speed ~ 800 km/s); Lehnert et al., 1999.• Galex obs. of UV halos suggested emissio

n of cold gas and dust (until the H cap); Hoopes et al., 2005.

Massive Coronas of Galaxies

• Dark matter halos contain about 10 times the mass of the visible baryonic matter.

• Mass in the extended corona (r ~ 300 kpc) of a spiral galaxy in ionized hot gas could be much larger than the “condensed” baryons (Fukugita and Peebles, 2005)

• Half coronal hot plasma (kT ~ 0.3 kev) and half dark matter!

• Star fomration rate balanced by plasma condensation rate!

NGC 6946

From Yi-Tong Chen

Summary

Still many puzzles and many challenging issues inspired by M82!