Physical Conditions and Feedback in Intense Star Forming Environments

1. Physical Conditions and Feedback in Intense Star Forming Environments J. Gallagher-U. Wisconsin L. J. Smith- Univ. College London R. W. O’Connell- U. Virginia May 2004 STScI Workshop

2. M82 view from the ground: A VERY disturbed galaxy--bright with complex structure: dust and superimposed “stars” 1 arcsec ≈20 pc M82: 3.5-m WIYN Telescope I-band M82F M82-F & L M82-A1 J. Gallagher & L. J. Smith

3. M82-F 430 pc 25 arcsec WHT spectroscopy: Gallagher & Smith 1999, MNRAS, 304, 540 Age = 60  20 Myr HST angular resolution essential to measure sizes!

4. M82-F: WHT Echelle Spectra& Mass: A Doomed SSC? SSCs have the mass and size of globular clusters. Star formation at the high density extreme of the interstellar gas cloud dissipation sequence. Roles of initial conditions & environment in survival? Smith & Gallagher 2001, MNRAS, 326, 1027

5. L/M vs age of super star clusters Appears to lack low mass stars! 3 2 1 M82-F 0.1 Smith & Gallagher 2001, MNRAS, 326, 1027 M_min

6. Cluster Dynamical Evolution: Mass Segregation Compact young star clusters may be unstable against mass segregation effects. Primordial mass segregation potentially amplified. IMF & survival complex relationship. M82-F as example. Appears likely candidate for disruption. Did low mass stars ever form?

7. M82-Chandra X-ray vs HST NIC IR: X-Ray Binaries & SSCs? XRBs not concentrated in SSCs: ejection? Implications for intermediate mass BH growth? Kaaret et al. 2004 MNRAS, 348, L28

8. 10 x sharper view with HST: “Stars” brightest super star clusters-stellar energy inputs on scales too small to measure from the ground. Complex gas outflows & dust lanes; the violent atmosphere of a starburst WFPC2 BVI+H M82 A1 STScI-PRC2001-08b R. de Grijs

9. STIS spectroscopy of starbursts: • resolve compact clusters from background and each other--close projected packing in starburst clumps. • high spectral resolution-advantage of diffraction-limited optics. Allows charting of substructures confused at ground-based resolutions. • Access to key lines, e.g., [OII] and [OIII] for empirical emission line abundances and Balmer jump absorption edge for ages.

10. M82 A1: A luminous compact star cluster in region A--WFPC2 “V” Image STIS slit position L. J. Smith et al. 2004 in prep O’Connell et al. GO 9117 170 pc

11. [NII]+H [SII] Smooth line profiles: projected random velocity fields relatively uniform. STIS Cluster M82-A1 Smith et al 2004 in prep Distance along slit -> Wavelength ->

12. [NII]+H [SII] Distance along slit -> STIS Cluster M82-A1 Smith et al 2004 in prep Compact HII around M82-A1 FWHM size of M82-A1continuum ~0.3 arcsec=5 pc HII region slightly larger, ~10 pc Example of luminous, evolved, but compact HII region

13. M82 STIS [SII] Emission Lines Nearly equal intensities-> ne≈1000 cm-3 Moderate I([SII])/I(H)=0.2 consistent with photoionization High mean thermal pressure: P/k ≈107

14. Starburst: Fragmented ISM Clouds embedded in low density hot, high pressure ISM: HII dominated by thin ionization fronts on dense, complex and often dusty clouds. ISM not static. Ionized gas has complex morphology and velocities.

15. M82 STIS H + [NII] Emission Lines rather broad; fwhm observed =2.8 Å -> HII velocity dispersion ≈35 km/s. High turbulence=good environment for making SSCs Flux

16. H FWHM (km/s) Type of Ionized Region (Hunter & Gallagher 1997, ApJ, 475, 65)

17. WFPC2-V WFPC2-H

18. Hot young SSC with stellar wind bubble A theoretical idea: Shocked high pressure ISM Soft H-ionizing radiation Density boundedHII shell Radiation bounded O++ zone Off center HII region from ISM superwind

19. Possibility: Compact star clusters=Positive Star Formation Feedback? To remain bound after star formation, require that ≥30% of mass in cloud center converted to stars. Normal star formation efficiencies are <10% Connection possible between intense star formation and high rates of star cluster formation? Cluster Dominated Star Formation = Efficient Star Formation  Higher SFR/Molecular Cloud Production Rate

20. Impacts of energy & mass outflows from starbursts • mass ejection vs. star formation rates • preferential loss of metals from SNe • structure of outflows--cooling rates • mixing into IGM vs. infall & recapture • stimulated star formation within & beyond starburst zones • ISM sweeping in companion galaxies

21. WIYN Narrow & broad band images: M82 Superwind Stellar disk continuum Emission line superwind

22. New perspectives on M82 superwind from the combination of WIYN 3.5-m & HST broad- and narrow-band images HST:0.05 arcsec resolution, moderate surface brightness sensitivity, especially in narrow band filters. WIYN: 0.5-1 arcsec resolution with excellent narrow band surface brightness sensitivity over wider FOV.

23. M82: HST WFPC2 + WIYN M. Westmoquette (UCL), J. Gallagher (UW), L. J. Smith (UCL) With NASA/ESA and WIYN Observatory/NSF Dramatic?!!

24. M. Westmoquette (UCL), J. Gallagher (UW), L. J. Smith (UCL) With NASA/ESA and WIYN Observatory/NSF M82: HST WFPC2 + WIYN

25. Connections between scales: Kpc-size winds driven by 10 pc massive, compact star clusters: energizing multiple nozzles=“shower head” wind Tenorio-Tagle, Silich, Munoz-Tunon 2003 ApJ, 597, 279

26. M82: The Multi-Wave Poster Galaxy HST P NICMOS NIC GTO: Alonso-Herrero et al. 2003, AJ, 125, 1210 Radio VLA + MERLIN: Wills et al. 1999, MNRAS, 309, 395

27. Chandra x-ray with H + [NII] WIYN contour overlay--approx alignment Not a simple wind in hollow cone--no limb brightening in optical emission, instead optical and x-ray emission nearly coincident. Multiple small flows escaping from ISM “tunnels” to form multi-stream cosmic “shower” vs. uniform wind? N E

28. NGC 3077: WFPC2 Studies-Stars, Gas & Feedback: Confined outflows? Where are the Shocks? F300W H D. Calzetti et al. 2004, AJ, 127, 1405

29. NGC3077: Shells & narrow shocks (black) from WFPC2 imaging emission line ratios. Shells: Martin (1998--polygons); CO Walter et al. (2002--ellipses) Calzetti et al. 2004, AJ, 127,1405

30. Summary • High angular resolution reveals super star clusters as common star formation mode in starbursts: • formation of 100s-1000s of massive stars in <1 Myr • maximum density star formation mode; requires <10 pc resolution • focused inputs of UV & mechanical power sources • positive feedback through dynamic, high pressure ISM? • HST reveals small-large scale connections in starbursts • starburst clumps sources of unsteady outflows traced in ionized gas • shocks & compact ionization fronts; small intrinsic scale. • chemical enrichment of surroundings--how does mixing occur?

31. Intense star formation is not a simple scale-up of processes commonly observed in galactic disks. Models exist and require observational tests. Only HST offers the combination of wavelength agility, angular resolution (WFPC3; HRC!+NIC), and spectroscopy STIS (+COS! For winds) to study critical small scale structures and processes in the nearest starbursts through optical photometric (r, L())& spectral line diagnostics (absorption [star clusters] & emission [nebulae] lines). A baseline for astrophysics of distant galaxies.