Gas and Stars in Galaxies - Lessons from Eggs

1. Gas and Stars in Galaxies - Lessons from Eggs Matt Lehnert GEPI, Observatoire de Paris

2. this is my brain after 4 days of meeting Lessons from Eggs Eggs have negative effective "heat capacity" ... harden when heated violent mixing history tcooling~few-many tdyn high [butter/egg] spheroid-like w/ small v and large σ quiescent accretion history tcooling>>tdyn forms inside-out non-uniform heating central disky bulge low [butter/egg] (proto)-egg

3. SAURON Tim on the weekend Gas and Stars in Galaxies - A Multi- 3D Perspective GRAVITY VIMOS KMOS MUSE SINFONI VLA PdBI WSRT GIRAFFE ALMA SKA ATCA X-Shooter E-ELT EAGLE

4. Philosophical Considerations Two philosophical general views of science: • holism/emergentism (modern) • Connect processes through statistics and information theory • like to use the words ... • "complexity/organization" • "information" • "chaotic/non-linear/stochastic" • "propensity/irreducibility" • empirical physical sciences, anthropology, medicine • Reductionism (classical) • Always look for underlying simplicity • like to use the words ... • "causality" • "symmetry" • "fundamental" • "insightful/genius" • physicists, chemistry, cell biology

5. Assembly: Why so Difficult? • Developing a coherent model for the growth of baryons in galaxies is inherently difficult. Why? • Highly non-linear problem • Wide range of physical scales (LSS to Galaxies to Stars) • Lots of marginally constrained physics like feedback, star-formation, • form and nature of the IMF, interfaces between different phases, • phase changes, heat capacity of gas, gas accretion/infall, merging, etc. • − all highly stochastic and perhaps strong function of mass and epoch. • Thus ... • Models have little direct predictive power – need observational constraints

6. Solving the right problems? • Things we don't understand or "today's problems": • details of star-formation • Gas accretion in mergers versus quasi-adiabatic/violent accretion • Angular momentum problem in disks • secular evolutionary processes - Where and when important? • "mixing problem" - instantaneous recycling & sources of gradients? • AGN: exorcisms, maintenance, why exponential cutoff in mass • Which came first: Galaxies or AGN? • Stochasticity of star-formation in high redshift galaxies: What and why? • Self-regulation/limited efficiency of star-formation: how? • 3-D instruments are very effective for investigating galaxy evolution though archeology, relating the physics connecting a range of physical phases, and for observing galaxy evolution in situ, helping us to solve these problems

7. Physical Processes for Bulges Dynamical timescale “instability” or cooling timescales Kormendy & Kennicutt (2005)

8. Characterizing E/SOs • I was struck by: • evidence that angular momentum is expelled outwards • kinematics have reformed our ideas about morphological classifications • (i.e., importance of rotation) • importance of rotation implies the importance of unequal mass mergers • and relative mass is the strongest determinant of outcome. Minor mergers drive red • sequence evolution? Faded spirals? • relationship between UV "disk/arms", mm gas and young cold stellar • component (which falls along the "Kennicutt relation"), but not always so direct • (steepness of rotation ... Toomre criteria). Complexity/variance of the HI and • long dynamical times. • models within a cosmological context cannot get orbital structure • correct(?), there is a wealth of information to be exploited. • It is fascinating that we can see evidence for small, but important changes in early types and that we are now obtaining a good understanding of the relationship between stars and gas ... it is unfortunately that it is not clear how this relates generally to our cosmological model

9. Key Questions for Gas/Star-formation I was struck by: Star-formation efficiency is not strongly dependent on physical environment in disks, molecular gas forms with fixed efficiency, GMC populations are universal, GMC formation does depend on environment. It appears large scale dynamical processes play an important role. This was for nearby disks. But how well do we understand about more extreme environments? Even with really great data on a range of GMCs in nearby galaxies, we still cannot rule out models like "photo-moderated star-formation", e.g., McKee '89. CO missing large envelopes. Extremely important. Obviously, not the conference for this, but this is intriguing. We see gas accretion in HI, but it is typically about 0.1 M yr-1, while we would like dM/dtaccretion ~dM/dtstar-formation. What about cooling hot gas, OVI? Controversial. Strong cooling lines are good. Even modeling binary mergers have limited utility given the large number of free parameters, but is good for getting the geometry right, how long interacting, when star-formation might occur, but still a long way to go. Finding galaxies in the streams and characterizing them is very important and can constrain models and DM distribution (i.e., a lot more info needed). Nuclear star-formation self-regulated by its own mechanical energy ... violence vs. resistance!

10. Key Questions for Data/Analysis Despite "If you can write software, you can do anything!" ... software cannot remove "features" in instrument design, cannot make up for lack of S/N. Uncertainties always determine the interpretation of results ... sounds obvious, but is often forgotten ... explains the hesitancy of some to move to 3-D visualization ... can we be mis-lead. More attention to uncertainties must be a high priority. Interpolations and regriddings are almost always not well done ... let's try to avoid them ... Within increasing data rates, automated, trustworthy software is going to be urgently needed. Models to interpret the wealth of data will be important, especially molecular lines. Physically associating phases and interfaces is going to be crucial for explaining the myriad of global physical process in galaxies.

11. Relationship between BH-Galaxy-LSS? 10-1-1 pc [M/H] and B 101-3 pc 103-4 pc Self-reg & Eddington limiting 104-6 pc MBH-σ & mass disposal 106-8 pc Regulate ISM Galaxy formation Heat halo & cluster gas Dynamical evolution of galaxy centers & star-clusters LSS

12. Key Questions for AGN Did black holes really fall into place before galaxies? Over what time and physical scale is this true? Do we understand the relation between MBH-σspheriod-Lbulge empirically or theoretically? High mass and low mass end? vs. Exponential decline in BH mass function must mean growth is self-regulated and this probably happened early. But is the feedback on the galaxy positive or negative? Does it change with epoch or gas phase/content? It is likely that AGN can regulate cluster scale cooling flows (i.e., cluster entropy floor), but can they regulate galaxy growth? Plausible, but what if the BH forms first. How does the galaxy stop the BH from "over-growing"? In growing BHs, is their growth self regulated or regulated by the surrounding starburst? Does nuclear star-formation regulate the torus properties and hence the AGN class? Streaming motions from large scale are seen in Seyferts, but what's the connection with fueling? Do gravitational torques really drive gas flows? Do we need the addition of viscosity on the smallest scales? How do stars influence this?

13. Disk formation – accretion? Clumpy galaxies in the UDF … Elmegreen et al. (2005; 2007), Bournand et al. (2007; 2008) … represent about 10% of galaxy population at z~1-3 ... time scales imply all disks may have had a "clumpy phase" ...

14. Clump-Cluster Evolution Bournaud, Elmegreen, & Elmegreen (2007) Bournaud, Daddi, Elmegreen et al. (2008) Evolution driven by Jean's instability and then dynamical friction, dissipation, perhaps viscosity in redistributing the angular moment ... may form the central supermassive blackhole ...

15. Clump-Cluster Evolution “Skywalker” complex clump cluster morphology with a “red bulge” ... Bournaud, Daddi, Elmegreen et al. (2008) ... are these really clumpy disks ... or something more complex ...

16. Clump-Cluster Evolution Do the clumps rotate? Does this allow for sufficient dissipation? Bournaud, Daddi, Elmegreen et al. (2008) ... plausible that the rotating clump will dissipate and add to the red bulge of the "skywalker" ... first time there is dynamical support for such a model ...

17. Key Questions for High-z Galaxies What are the relative roles of gas accretion vs. mergers in galaxy growth? How do sample biases/mass/star-formation rate biases limit our ability to interpret these results? Are their local analogues ... SMGs=ULIRGs? Disks = Disks? When know that LSS influences the "outcomes" of galaxy evolution, does this affect our interpretations? Does finding rotating imply "cosmological" gas accretion? What are the important physical processes within these disks? Are they globally Jean's unstable? Do these clumps harbor BHs? Low physical resolutions, 100 mas = 0.8kpc at z=2, means we are combining a lot of different physical processes in each resolution element. AO PSF is ~diffraction limited core + "seeing-sized" halo, implies heavy "phase mixing" -- high v/σ no sigma peaks. Also, light distribution and scale and how it interacts with the PSF is extremely important in interpreting the data. Unfortunately, we do not know the underlying light distribution at sufficient resolution. Affects all data ... even mm. mm observations are fascinating and important -- need many more -- however, what is the relationship between the warm and cold gas? What is the physical nature of molecular emission? What is the range of gas depletion times and how does this compare to the dynamical times?

18. I learned a lot! Future seems bright! Thank you! And now for your immediate future!