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![Page 1: Probing the Birth of Super Star Clusters Kelsey Johnson University of Virginia Hubble Symposium, 2005.](https://reader036.fdocuments.net/reader036/viewer/2022062523/5a4d1add7f8b9ab059975644/html5/thumbnails/1.jpg)
Probing the Birth of Super Star Clusters
Kelsey JohnsonUniversity of Virginia
Hubble Symposium, 2005
![Page 2: Probing the Birth of Super Star Clusters Kelsey Johnson University of Virginia Hubble Symposium, 2005.](https://reader036.fdocuments.net/reader036/viewer/2022062523/5a4d1add7f8b9ab059975644/html5/thumbnails/2.jpg)
Why study Why study massive star massive star
cluster cluster formation?formation?
Most stars form in clusters!
To understand star formation in general,
we need to understand the
“clustered” mode
![Page 3: Probing the Birth of Super Star Clusters Kelsey Johnson University of Virginia Hubble Symposium, 2005.](https://reader036.fdocuments.net/reader036/viewer/2022062523/5a4d1add7f8b9ab059975644/html5/thumbnails/3.jpg)
Why study “Super Star Cluster” Why study “Super Star Cluster” formation?formation?
Spitzer image of 30Dor, NASA/JPL-Caltech/B.Brandl
• 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
“A cluster that is young enough to still contain
massive stars and has the possibility of evolving into a
globular cluster”
age ≤ 10 Million yearsmass ≥ 104 - 105 M
radii ≤ a few parsecs
Super star clusters (SSCs):
![Page 4: Probing the Birth of Super Star Clusters Kelsey Johnson University of Virginia Hubble Symposium, 2005.](https://reader036.fdocuments.net/reader036/viewer/2022062523/5a4d1add7f8b9ab059975644/html5/thumbnails/4.jpg)
A fossil inthe Milky
Way...• > 10 billion years old• a few parsecs in size• ~ 104 - 106 stars How were these
incredible objects formed?
![Page 5: Probing the Birth of Super Star Clusters Kelsey Johnson University of Virginia Hubble Symposium, 2005.](https://reader036.fdocuments.net/reader036/viewer/2022062523/5a4d1add7f8b9ab059975644/html5/thumbnails/5.jpg)
Observational strategy:If we want to understand cluster formation, it’s not a bad idea to observe them while they are
forming.
HST image of the Antennae Galaxies B.Whitmore/NASA
Problem:Once clusters are fully visible in optical light,
their birth environments have been dramatically
altered
![Page 6: Probing the Birth of Super Star Clusters Kelsey Johnson University of Virginia Hubble Symposium, 2005.](https://reader036.fdocuments.net/reader036/viewer/2022062523/5a4d1add7f8b9ab059975644/html5/thumbnails/6.jpg)
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?
![Page 7: Probing the Birth of Super Star Clusters Kelsey Johnson University of Virginia Hubble Symposium, 2005.](https://reader036.fdocuments.net/reader036/viewer/2022062523/5a4d1add7f8b9ab059975644/html5/thumbnails/7.jpg)
Strategy: Look for sources with similar SEDs to Ultracompact HII regions
S
(cm)100 1
non-thermal
free-free
optically-thick free-free
Wood & Churchwell 1989
Compact, “inverted spectrum” sources
Very dense HII regions
• Radii of HII regions• Electron densities Pressures • Ionizing flux Stellar Masses
Model:
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Henize 2-10 (9 Mpc, linear res ~ 20pc)
VLA 2 cm contour, Gemini 10m 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
VLA 2 cm contour, HST V-band color-scale(Kobulnicky & Johnson 1999, Johnson & Kobulnicky
2003)
![Page 9: Probing the Birth of Super Star Clusters Kelsey Johnson University of Virginia Hubble Symposium, 2005.](https://reader036.fdocuments.net/reader036/viewer/2022062523/5a4d1add7f8b9ab059975644/html5/thumbnails/9.jpg)
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-bandContours: VLA X-band
Johnson et al. 2004
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Massive proto-cluster detected in mid-IR: Av > 15 - 30 AND similar embedded stellar mass
(Hunt, Vanzi, & Thuan, 2001; Plante & Sauvage, 2002)
SBS 0335-052 (53 Mpc, linear res ~ 25pc)
ultra-low metallicity (Z 1/40 Z)
NLyc 12,000 1049 s-
1 12,000 O7* stars Yikes!
Color scale: HST NICMOS Pa
Contours: VLA + Pie Town X-band
Color scale: HST ACS F140LPContours: VLA + Pie Town X-band
Johnson & Plante in prep.
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3D Monte-Carlo Radiative Transfer
Johnson, Whitney, & Indebetouw in prep.
Near-IRJ, H, K
Spitzer IRAC3.6, (4.5+5.8), 8.0 m
Spitzer MIPS24, 70, 160 m
Modeling the Evolution of Super Star Clusters
Example: 90% clumpy, Rin = 5pc, Rout=50pc, SFE=10%
• Enables dust structure• Enables multiple sources
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3D Monte-Carlo Radiative Transfer: Super Star Clusters Geometric Sequence (pseudo evolution)
Johnson, Whitney, & Indebetouw, in prep
Model Evolution of SED• SFE 10%, Rout=25pc
% Smooth
100%90%50%10%1%
Rin= 1pcRin= 3pcRin= 6pcRin= 9pcRin= 12pcRin= 15pcRin= 18pcRin= 21pcRin= 24pc
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WARNING!WARNING!WARNING!WARNING!WARNING!WARNING!Assuming that dust cocoons are
smooth can lead to vastly misinterpreting Spitzer data. Proceed
with caution!
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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)
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Looking toward the Future (IR - mm)
106 M proto cluster at 10 Mpc
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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