Arp 220 - A starburst Galaxy and nearest ULIRG Arp 220 - A starburst Galaxy
VLBA Image of the core of Arp 220 at 1.4 GHz - Lonsdale et al. in prep SFR vs Hubble type! -1 E ~ 0 M yr -1 S0 ≤ 0.004 M yr -1 Sa ~ 0.3 M yr -1 Sb ~ 3 M yr -1 Sc ~ 5 M yr -1 Sd-Im ~ 1 M yr (smaller galaxies) There is much variations, huge range, often in bursts. Note: spread within a Hubble type > difference between types. Astronomy 422
Lecture 10: Normal Galaxies III Spiral structures Key concepts:! Spiral structure - density waves Resonances help to create stable structures Disk instabilities comes in different forms - spiral structure is one of them.
M83 - a pinwheel structure???! Recall Hubble classification: • a, b or c classification refers to size of nucleus and the tightness of the spiral arms.
• Sc has smaller nucleus and less tightly wound spiral arms than an Sa.
• Number of arms, and how tightly they are wound are correlated with large scale properties: – Bulge/disk luminosity ratio – Amount of gas