Investigation to understand assumptions made in extragalactic obs
- MW single example - what is unique, what general?
- SNR / CR interaction model works in M82 & NGC 253, not in MW
- MW SFR? Is it right?
- lots of nearby SAB moderately-barred spirals moderately analogous to MW
- Maffei 2 + 5x10^7 msun mol gas in rotating core
- NGC 253 + 10^8 msun molecular gas
- MW + 3-4x10^7
Similar molecular and stellar content
- Major differences
- MW: SFR 0.01 Msun/yr [my comment: this seems low?]
- IC 342 & Maffei 2: 1 Msun/yr
- NGC 253, M82: 3-8 msun/yr + nuclei don't follow CO vs SFR
- NGC 253: huge wind (almost naked eye) + 10-100x MW CMZ thermal pressure
- Gamma rays: MW overluminous at low energies?
Statement: "No correlation. Extragalactic relation totally fails" on a plot with 5 data points...
- not tied to CO
- Must be a large range in SF efficiency
- SFR not correlated with nuclear stellar mass
- MW in SFR low-state
- Episodic SF
- Physical state varies + Chemical transition? + driven by chemistry rather than mass?
- SF bimodal? Need larger sample
- Unexpected SMBH impacts?
Advertisement: AJ - interested in improving figure distribution. aj@astro.wisc.edu
Questions
- Q: Comment - SF adequate to explain energetics seen
- Q Longmore: Idea for what's stopping SF in our own galaxy. Rate limiting factor is that gas is not self-gravitating.
- A: turbulent, yeah.
- Q Mitch: Positive feedback. SF starts, gets intensified. Squeezed by external pressures.
- A: Agree
- Q: SFR density of mol gas.
- A: Cloud production mechanism is different (rather than SF "relation" breaking down)
- Q: Large range in star formation. Is wind/outflow to SFR more constant?
- A: would like to know. Outflows not well-measured.
- Q: Constant at what value?
- A: Outflow/SFR constant
- Q Farhad: Dense gas in other galaxies?
- A: Not known yet. Need to know dense gas fractions
- Q Farhad: Need to know fraction of dense gas.
- A: Bigger debate in N253