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Starbursts & Super Star Clusters

Starbursts & Super Star Clusters. J. Gallagher U. Wisconsin-Madison with L. J. Smith, M. Westmoquette (UCL), R. O’Connell (UVa), R. de Grijs (U. Sheffield). MODEST-6 Workshop- 29 August 2005.

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Starbursts & Super Star Clusters

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  1. Starbursts & Super Star Clusters J. Gallagher U. Wisconsin-Madison with L. J. Smith, M. Westmoquette (UCL), R. O’Connell (UVa), R. de Grijs (U. Sheffield) MODEST-6 Workshop- 29 August 2005

  2. Super Star Clusters (SSCs):Upper Mass Range for Young Compact Clusters--Densest Single Generation Stellar Systems--Endpoint of Star Formation Dissipational Sequence • Stellar mass >104 Msun • Half light radius R1/2 ≤ 5-7 pc • Within R1/2 N*(1 Msun) ~104 - 106 pc-3 • Ages << globular clusters 0-few 100 Myr • Common in starbursts--sometimes tightly packed in starburst “clumps”

  3. Possible Starburst Scale-Intensity ULIRGs high 1012 L Starbursts N1275 M82 M83 1010 L Intensity Starbursts are not simply scaled-up versions of normal galactic disks. NGC1569 108 L Main SFR density starburst contribution from moderate mass galactic starbursts: “downsizing”. Orion OB Assoc low Spiral arm 0.01 1 0.1 Starburst Scale (kpc)

  4. Measuring Parameters • Linear size R--high angular resolution, 0.1 arcsec or better needed for D<10 Mpc; half light radius. • Age tcl--spectral energy distributions; colors okay if broad wavelength coverage; NIR alone difficult • Luminosity Lcl()--photometry & extinction correction; zone of radiative influence for ionization and mechanical luminosities • Chemical abundances Z*--stellar or HII spectra • Dynamical mass--stellar velocity dispersion, requires cool stars (tssc > 6-7 Myr) • Stellar mass function--resolved cluster or Mdyn/L with age & model from measured Lcl(, Z*, tcl, Mcl*)

  5. Hunter et al. 1995 ApJ, 448, 179 R136 Radial Profile Archetype: 30 Doradus: small super star cluster or “SSC” Berstein & Novaki 1999, APOD

  6. NGC 1569: SSCS in a dwarf starburst

  7. A = Double Cluster De Marchi et al. 1997, ApJ, 479, L27 B A 10 NGC 1569: Dwarf Starburst Galaxy P. Anders, U. Goettingen; data HST: ESA/NASA

  8. Composite spectra: Mixture of ages--high mass stars, >30-40 Msun present in SSCs; RSGs in optical of cluster A WR* Cluster A Cool star Ho & Filippenko 1996, ApJ, 466, L83

  9. Smith & Gallagher 2001, MNRAS, 326, 1027

  10. NGC 1569 - NIR with WIYN 3.5-m Telescope; Natural Seeing: SF Patterns: SSCs Embedded in Young Star Clouds NGC 1569--3 SSCs in ~10 Myr-- Feedback induced shift in SF mode? Increased pressure of SSC A a dominant factor? SFR declines as dense ISM exhausted-and ejected? GMC formation vs. destruction? SSCs10 A B

  11. Is the formation of SSCs a statistical process as the stellar IMF appears to be: More clusters= higher upper mass limit? (Yes in Antennae--but are these compact SSCs? (M82 ??) OR Is SSC formation in some cases a result of a feedback enhanced mode of star formation? (NGC1569?)

  12. NGC1569 SSCs NOT detected as luminous X-ray sources: L(x) ≤ 2 x 1036 erg/s Martin, Kobulnicky, Heckman, 2002, ApJ, 574,663

  13. M82-nearby giant starburst Stellar disk M. Westmoquette (UCL), J. Gallagher (UW), L. J. Smith (UCL) With NASA/ESA and WIYN Observatory/NSF M82: HST WFPC2 + WIYN

  14. M82 view from the ground: A VERY disturbed galaxy-- bright starburst clumps: dust and superimposed SSC “stars” D=3.6 MPC 1 arcsec ≈19 pc M82: 3.5-m WIYN Telescope I-band M82-SSCs F & L M82F M82- clump A M82- clump B J. Gallagher & L. J. Smith

  15. Melo et al. 2005, ApJ M82 SSCs & Starburst Clumps: V-band WFPC2 M82-A1 SSC: 106 M - r1/2~2-3 pc - t<10 Myr >> L. Smith Talk for Details! << Starburst Clump A ~10 Myr

  16. NGC 7673 starburst-WFPC2 Homeier, Gallagher, Pasquali ~8 kpc Clumping of compact young star clusters-a step beyond super OB associations? Characteristic of unstable gas-rich disks subject to intense star formation? Background galaxy D=40 Mpc; MV=-20

  17. Hubble Ultradeep Field: High-z clumpy & compact starbursts--a key early star formation mode

  18. Chandra X-ray contours: wind mass loading + thermalization

  19. Basic astronomy: Astrometry key to IDs, especially as distance increases… Chandra vs clusters in Antennae: Fabbiano et al. 2002, ApJ, 577, 710 1 arcsec= 73(D/15 Mpc) pc

  20. 1 arcsec M82-Chandra X-ray vs HST NIC IR: X-Ray Shocked Winds & Binaries in SSCs? Most SSCs not luminous X-ray sources. Wind thermalization low within clusters (clumpy winds???) BH binaries ejected Implications for intermediate mass BH growth--nuclei vs. “field” Kaaret et al. 2004 MNRAS, 348, L28

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

  22. 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? SFE vs Mcl? Smith & Gallagher 2001, MNRAS, 326, 1027

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

  24. ? ? 5 pc “Using PSF-fitting photometry, we derive the cluster’s light-to-mass (L/M) ratio in both near-IR and optical light and compare to population-synthesis models. The ratios are inconsistent with a normal stellar initial mass function for the adopted age of 40–60Myr, suggesting a deficiency of low-mass stars within the volume sampled.King model light profile fits to new Hubble Space Telescope ACS images ofM82-F, in combination with fits to archival near-IR images, indicate mass segregation in the cluster. As a result, the virial mass represents a lower limit on the mass of the cluster.” McCrady, Graham, & Vacca 2005, ApJ, 621, 278

  25. ComplexStar Cluster Ecology: AffectsSurvivalRates! Low M/L in an older SSC--signature of impending disruption? Why do GCs survive when mortality rates seem high in nearby SSC systems? Extra binding (DM???)--Special Formation Conditions?? Gallagher & Grebel 2003, IAU 217

  26. Starburst field FUV spectra systematically “older” than SSCs --> substantial cluster dissolution within ~10 Myr? Chandar et al. 2005, ApJ, 628, 210

  27. BUT Many M82 region B star clusters have colors consistent with ages of near 1 gyr. (also Parmentier, de Grijs & Gilmore 2003, MNRAS, 342, 208) ->> Evidence of long lived clusters and multiple bursts associated with orbital period of M82. de Grijs, O’Connell, Gallagher (2001)

  28. M82 Starburst Clump B ~1000 Myr clusters But where are the 2000 Myr clusters?

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

  30. Summary • SSCs are commonly produced in intense star forming events with masses up to and beyond 106 Msun and R1/2 ~ 2-5 pc. • Densest stellar cluster--an extreme of star formation. • SSCs cluster to make “starburst clumps” where SSC-SSC interactions are possible and which drive galactic winds. • SSCs contain a full range of intermediate-high mass stars. • Central stellar densities can exceed 105 stars/pc3. • Mass segregation may have a major influence on the observed properties (low M/L ratios) and evolution (dissolution) of SSCs. PDMFs thus are uncertain. • Statistics of SSCs suggest high early disruption rates in starbursts, although in some cases significant numbers of clusters reach ~1 Gyr in age. • SSCs do not appear to generally host strong X-ray sources, suggesting that SNe II binaries are ejected.

  31. M82--11.7 microns--compact star forming regions Lipscy & Plavchan 2004, ApJ, 603, 82

  32. NGC1569-photo ages: Anders et al. 2004, MNRAS, 347, 17

  33. 2002 A&A, 381, 825 SNRs in NGC1569: Triggered SF? Merlin: compact radio sources

  34. McCrady, Gilbert, & Graham 2003, ApJ, 596, 240

  35. Cluster Dynamical Evolution: Crossing Time Cluster crossing times typically 1% or less of galactic orbital periods and 10% or less of massive star evolutionary time scales. We are dealing with systems that experience substantial dynamical evolution: SSCs not durable?

  36. Clusters & Dynamical Evolution: Two Body Relaxation Time scale for two-body relaxation to become important--a fundamental reference time in a star cluster: But time scale varies with position and mass: Cluster cores evolve rapidly, especially if massive stars Preferentially form near the cluster center. O. Gerhard 2000, Massive Stellar Clusters, p12

  37. X-ray sources & clusters--diffuse hot gas backgrounds Martin, Kobulnicky, Heckman 2002, ApJ, 574, 663 V(HII) ~ 100 km/s-- Slow optical wind

  38. M82 - SUPERWIND ! A C H +[NII] HST/WFPC2

  39. Smith & Gallagher 2001, MNRAS, 326, 1027

  40. Tosi et al WFPC2 Pasquali et al. WFPC2 Dwarf starbursts: NGC1705 Harris et al WFPC2 Nuclear starbursts: M83 Major mergers: NGC6240 Interactions: M82 Gallagher et al. WIYN

  41. M82: Radio (Rodriguiz-Rico et al. 2004, ApJ, 616, 783) vs. HST F160W NICMOS Image OR Perils of 1 arcsec rms positions + SNR x HII region

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