The Extremes of Formation in Super Star Clusters

Kelsey Johnson

With help from: Alan Aversa, Crystal Brogan, Rosie Chen, Jeremy Darling, Miller Goss, Remy Indebetouw, Amanda Kepley, Chip Kobulnicky, Amy Reines, Bill Vacca, Lisa May Walker, David Whelan, Barb Whitney The Extremes of Star Formation in Super Star Clusters

1) What physical conditions are required to form these clusters?

2) Does this extreme environment affect affect the SF process itself? Strategy: Look for sources with similar SEDs to Ultracompact HII regions

Compact, “inverted spectrum” sources Very dense HII regions non-thermal

Sν free-free

optically-thick free-free 100 1 λ (cm)

Wood & Churchwell 1989 NGC 4449 II ZW 40 NGC 4490

Aversa et al.sub Image credit: Michael Gariepy/ Kepley et al. in prep, Beck et et al. Adam Block/NOAO/AURA/NSF Reines et al. 08

NGC 2537 NGC 5253 NGC 3125

Aversa et al. sub Turner et al. 00 Aversa et al. sub Image Credit: Sloan Digital Sky Survey Image credit: Angel Lopez-Sanchez

Haro 3 IC 4662 NGC 4214

Beck et al. 00 Image Credit: NASA and Hubble Heritage Team (STScI) Johnson et al. 03 Johnson et al. 04 Natal Clusters are rare! (i.e. short‐lived)

Recent radio survey of nearby “star-forming” : Only 9/28 have detected thermal sources

(Aversa, Johnson, Brogan, Pisano, & Goss submitted) Early Universe Analog?

SBS 0335‐052 ultra‐low metallicity: 12 + log(O/H) = 7.25

VLA + Pie Town X‐band, HST opcal

≈ 10,000 O-type*

Reines, Johnson, & Hunt 08 HST ACS H, V‐band, UV Johnson, Hunt, & Reines 09 What can we learn from the radio continuum?

Radii of HII regions → as small as a few pc

7 Electron densies → Pressures > 10 kB Ionizing flux → Stellar Masses: up to 1000s O7‐type stars Radio recombination lines - a better tool! (e.g. Mohan, Anantharamaiah, & Goss 2001 & others)

4 -3 • Densities: ne > 10 cm • Radii: r ~ 2-10 pc 52 • Ionizing Flux: Nlyc > 10

excellent agreement with simple models!

Example: prediction for H92a line α α α α α α α α α α H62 H63 H70 H69 H67 H65 H64 H68 H66 H71 (1, 12 hours)

Don’t forget the EVLA!

EVLA + GBT Radio Recombination Line survey in the works! Led by Amanda Kepley ⇒ Stay tuned! Water masers!

⇒ All maser sources appear to be extremely young

Brogan, Johnson & Darling submitted Darling, Brogan, & Johnson 09 Natal SSCs are really darn bright in the IR!

He 2-10

The radio sources alone account for at least 60% of the mid-IR flux from the entire

VLA 2 cm, Gemini 10um (Vacca, Johnson, & Conti 2002) • Electron densities • Hardness of radiation field • Ionizing flux

Spitzer ch1,ch4, 24um (b,g,r) Radio 3.6cm contours

Johnson, Whelan, Indebetouw, & Reines in prep I-band Excess?

See Posters by Reines (GP2) & also Adamo (IP11)

NGC4449 Reines, Johnson, & Goss 08 Reines et al. 2010

VLA 3.6cm HST V-band Panchromatic data is essential: stars, dust, and gas all contributing Is star formation always hierarchical?

If so, there is nothing particularly “super” about super star clusters

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L Is star formation always hierarchical?

If so, there is nothing particularly “super” about super star clusters

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L One of these things is not like the others

Contention: Star formation is a local process. Power-laws are build from ensembles over space & time.

Why does a cluster with particular properties form when and where it does? Or Given the properties of a cluster can we say something about its formation? He 2-10

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VLA+PT 1.3 cm contours,

Johnson et al in prep…

Linear resolution ~5pc

Johnson et al. 00 The initial cluster luminosity function in He2-10