THE MILKY WAY AS A STAR FORMATION ENGINE
Authors:
S. Molinari (INAF-IAPS, Rome, Italy), J. Bally (University of Colorado, Boulder, United States), J.-P. Bernard (IRAP, Toulouse, France), S. Glover (Heidelberg University, ITA, Germany), P. Martin (University of Toronto, Canada), T. Moore (Liverpool John Moores University, United Kingdom), A. Noriega-Crespo (IPAC-Caltech, Pasadena, United States), R. Plume (University of Calgary, Canada), L. Testi (ESO-HQ, Garching, Germany), E. Vazquez-Semadeni (UNAM, Morelia, Mexico), A. Zavagno (LAM, Marseille, France)
We review and discuss the latest observational scenario globally emerging from the latest generation of continuum and spectroscopic global-scale surveys of the mid-plane of the Galaxy from infrared to radio wavelengths, in terms of cloud formation and evolution, star and clump formation rate and efficiency throughout the Galaxy, evidence for density thresholds for the formation of protocluster-forming clumps, as well as the role of large-scale filamentary structures in channeling diffuse ISM into gravitationally bound clumps. The new view of the Milky Way thus assembled will be discussed in the context of competing theoretical frameworks distinguishing between "slow" and "fast" formation, outlining some of the challenges that this body of evidence poses to a variety of theoretical scenarios for large-scale star formation. We will review the most recent methods and evolutionary indicators used to classify the star formation activity in molecular clumps, comparing the different possible derivations of the local SFR and discussing its variation as a function of Galactocentric radius. The order-of-magnitude increase in the number of sources (mostly clumps) that are revealed in state-of-the-art infrared and submillimeter Galaxy-wide surveys make such studies possible with an unprecedented statistical significance. We will also review the present status of our understanding of the Galaxy as a global star formation engine in the context of similar studies in extragalactic systems, evaluating how the data on our own Galaxy compare with the proposed global star formation laws that relate properties of the interstellar medium to the star formation rate.
Intro
Link the MW to high redshift.
"Galactic Ecology"
- Efficiency "<15%"
- Feedback -> "superbubbles"
- "oops"
- solar circle Z-scale oscillation 80 Myr
- Epicyclic period 170 Myr [what is this orbital scale?)
- orbital timescale 220 Myr
Large scale view:
- Sco-Cen HI supershell (1973 A&AS)
- Rho Oph filament swept up by Sco-Cen bubble?
- Sco-Cen has HI, not H-alpha
- Alpha-Persei blew a bubble for Cosmologists
Orion CO
- Integral shaped filament
- Velocity jump occurs at cluster
- Vazquez-Semadeni 2008 colliding cloud resembles ISF
BGPS -> ATLASGAL -> Herschel
And now let's start the talk...
HiGal
HiGal 360 in OT2
W3/W4/W5
- W3 OB cluster
- W4 cometary cloud
- W5 (name drop)
- NGC 7538
- filament full of H2 outflows
- W43
- 50 Orions
- 3 Myr old
- older subgroup to the south
- Goodman's "we're out of the plane"
- Nearby spiral arms below the "plane"
- W51 - Spitzer
- massive clusters
- Back to M16, M17
- M17
- M17swex
- red square
- Nessie (Jackson)
- extended Nessie from Alyssa Goodman
- Carina Nebula
- eta car
- Trumpler 16
NGC 3603
Filament Formation
"Zeldovich Pancakes" - tend to collapse along minor axes first Converging flows "shadowing" HII regions -> cometary filament = tail Vazquez-Semadeni colliding flows movie
- Filaments in HiGal
- Schisano 2013 - Herschel filaments is continuously distributed (no threshold effect)
- Mass per unit length increases with amt of star formation
Distances
- Russeil "Bootstrap Morphology"
- BeSSeL parallax
- Distance PDF (Ellsworth-Bowers) * showed example DPDFs * Shirley & Schlingman HCO+/N2H+ velocities * description of the algorithm
- Bessel points colored by arm
- Battersby 2011 "Maybe I'll skip this"
- How does dust vary with SF signature
- Pestalozzi face-on view of the galaxy
- mass-luminosity plot
- Finish with the CMZ
- 80% of gas at n>10^4 in CMZ
- Bania's clump - strange kinematics
- Orbits in a bar
- Inner Lindblad resonance?
- compare our CMZ to NGC 1097
- Dust at l > 0, 24um sources at l < 0
- Molinari Ring
- Vertical oscillation timescale twice orbit timescale
- Sgr B2 has high proper motion in the plane
- Battersby temperature / column maps
- several 10^7 msun of non-star-forming gas
- Back to CMZ:
- Free-free emission
- CND / circumnuclear ring
- Sgr A* has no influence on the Galaxy
- star formation starves Sgr A*
Plug for CCAT, ALMA
Storm the Castle!
Questions
- Q: Mordecai - seen fragmentation starvation in massive star formation as well
- A: Yep. Also, Phil knows disk around black hole is like a disk around a protostar
- Q: Philippe - Threshold issue. No threshold in Hi-Gal data.
- A: missed it, someone walked in front of me
- A: Molinari - Different physics, different scales?
- Q: Sergei - Fermi bubble feature. Attributed to star formation. In other galaxies... we've seen one other analog? More than enough energy in a Sgr A* outburst.
- A: Should ask how we distinguish AGN-driven vs. star-formation-driven flows. AGN should be low-mass, light, relativistic launch. Star formation blows out big HI bubbles (high-mass).
- Same guy: Cosmologists say AGN can blow up whole galaxies
- Q Hans: Sequential star formation, triggered SF... are we more informed about triggering now than before?
- A: Triggering is a great model, but observationally indistinguishable. Only way to know is precision kinematics. Need GAIA. It happens, but can't be proved.