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Probing the Birth of Super Star Clusters

Probing the Birth of Super Star Clusters. Kelsey Johnson University of Virginia. Hubble Symposium, 2005. Why study massive star cluster formation?. Most stars form in clusters! To understand star formation in general, we need to understand the “clustered” mode.

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Probing the Birth of Super Star Clusters

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  1. Probing the Birth of Super Star Clusters Kelsey Johnson University of Virginia Hubble Symposium, 2005

  2. Why study massive star cluster formation? Most stars form in clusters! To understand star formation in general, we need to understand the “clustered” mode

  3. Why study “Super Star Cluster” formation? age ≤ 10 Million years mass ≥ 104 - 105 M radii ≤ a few parsecs Super star clusters (SSCs): “A cluster that is young enough to still contain massive stars and has the possibility of evolving into a globular cluster” • Formation (may) require extreme physical conditions • They are plausibly the progenitors of globular clusters • Formation mode was (probably) common in early universe • They can have a tremendous impact on both ISM & IGM Spitzer image of 30Dor, NASA/JPL-Caltech/B.Brandl

  4. A fossil inthe Milky Way... • > 10 billion years old • a few parsecs in size • ~ 104 - 106 stars How were these incredible objects formed?

  5. HST image of the Antennae Galaxies B.Whitmore/NASA Observational strategy:If we want to understand cluster formation, it’s not a bad idea to observe them while they are forming. Problem: Once clusters are fully visible in optical light, their birth environments have been dramatically altered

  6. Can we learn from Galactic Star Forming Regions? From Ultracompact HII Regions to Proto Globular Clusters Key Questions: How do the properties of star formation scale between these regimes? How do the properties depend on environment?

  7. Compact, “inverted spectrum” sources Very dense HII regions non-thermal Sn free-free optically-thick free-free 100 1 l (cm) Strategy: Look for sources with similar SEDs to Ultracompact HII regions Model: • Radii of HII regions • Electron densities Pressures • Ionizing flux Stellar Masses Wood & Churchwell 1989

  8. VLA 2 cm contour, HST V-band color-scale (Kobulnicky & Johnson 1999, Johnson & Kobulnicky 2003) Henize 2-10(9 Mpc, linear res ~ 20pc) VLA 2 cm contour, Gemini 10mm color-scale (Vacca, Johnson, & Conti 2002) Three brightest radio sources alone account for at least 60% of the mid-IR flux from the entire galaxy

  9. Haro 3(13 Mpc, linear res ~ 20pc) These radio clusters also have an “infrared excess” Hot dust near the ionizing stars Color scale: HST V-band Contours: VLA X-band Johnson et al. 2004

  10. SBS 0335-052 (53 Mpc, linear res ~ 25pc)ultra-low metallicity (Z  1/40 Z) Johnson & Plante in prep. NLyc 12,000 1049 s-1 12,000O7* stars Yikes! Color scale: HST ACS F140LP Contours: VLA + Pie Town X-band Color scale: HST NICMOS Paa Contours: VLA + Pie Town X-band Massive proto-cluster detected in mid-IR: Av > 15 - 30 AND similar embedded stellar mass (Hunt, Vanzi, & Thuan, 2001; Plante & Sauvage, 2002)

  11. Modeling the Evolution of Super Star Clusters 3D Monte-Carlo Radiative Transfer • Enables dust structure • Enables multiple sources Near-IR J, H, K Spitzer IRAC 3.6, (4.5+5.8), 8.0 mm Spitzer MIPS 24, 70, 160 mm Example: 90% clumpy, Rin = 5pc, Rout=50pc, SFE=10% Johnson, Whitney, & Indebetouw in prep.

  12. Rin= 1pc Rin= 3pc Rin= 6pc Rin= 9pc Rin= 12pc Rin= 15pc Rin= 18pc Rin= 21pc Rin= 24pc 3D Monte-Carlo Radiative Transfer: Super Star Clusters Geometric Sequence (pseudo evolution) • Model Evolution of SED • SFE 10%, Rout=25pc % Smooth 100% 90% 50% 10% 1% Johnson, Whitney, & Indebetouw, in prep

  13. WARNING! WARNING! WARNING! Assuming that dust cocoons are smooth can lead to vastly misinterpreting Spitzer data. Proceed with caution!

  14. To Do List: • Directly measure densities, pressures, temperatures (use IR forbidden lines, molecular lines, RRLs) • Directly measure radii with high resolution (EVLA, SKA at some point) • Determine how much ionizing radiation escapes (need bolometric luminosities, clumpiness) • Determine star formation efficiency (high resolution HI, CO, H2) • Find out if the individual stars have individual cocoons? (dependence on the evolutionary state?) • Determine how clumpy the dust is (high-resolution imaging and SED models) • Determine the temperature profiles (high-resolution photometry and SED models)

  15. 106 M proto cluster at 10 Mpc Looking toward the Future (IR - mm)

  16. Summary • Super Star Clusters are an important mode of star formation (plausibly proto globular clusters!) • We have a sample of natal clusters in a range of galactic environments, and we are learning about their formation • Thermal IR SEDs can be significantly affected by clumping • There is a lot to learn about these objects, and the new generation of telescopes will provide powerful diagnostics • The future is extremely bright for this type of research

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