Starbursts, Globular Clusters, and Dwarf Galaxies: What's Gone with the Winds?
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Transcript of Starbursts, Globular Clusters, and Dwarf Galaxies: What's Gone with the Winds?
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
NGC 1705--Tosi et al WFPC2
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
WLM-dIrrLuminous GCMV=-8.8WFPC2 studyHodge et al. 1999, ApJ, 521, 577
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
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NGC 147WIYN V-bandHodge clusters: inner & outer locationsHodge 1977, AJ, 81, 25
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
We conclude that----
Long ago small galaxies made sufficient numbers of dense, massive star clusters for some to survive to the present.
These are found in the range of neabry dwarf systems from dIrrs to dEs to dSphs in a range of spatial and kinematic patterns.
Questions: How did such small galaxies give birth to such clusters and what were the impacts? How does formation connect to chemistry and kinematics?
How important are GCs in powering outflows and reducing baryon content in low mass galaxies? Does this lead to very gas-poor galaxies?
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
Observational approach to dwarf galaxy massive star clusters &
gastrophysics--
Nearby dwarf starbursts host young massive “super star clusters” (SSCs); structural analogs to globular clusters:
• M ≥ 105 Msun• R(1/2) < 10 pc• Age < 30 Myr
SSCs--major power sources of L(Lyc) for [t<7-8 Myr] and L(mech) [t< 25-30 Myr].Observe feedback & cluster formation processes in action.
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
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NGC 1569: Gas-Rich Dwarf Starburst Galaxy, MV= -18
P. Anders, U. Goettingen; data HST: ESA/NASA
10 Myr, 106Msun
NGC1569 & NGC5253: Two starburst dwarfs
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
+ Super molecular cloud core: n>105 cm-3, Vturb~10 km/s + Mm to sub-mm -> dusty molecular ISM
+ Efficient star formation; SF>30% + SFR>0.1Msun/yr for T~106 yr; Mcl≥105 Msun+ Thermal IR & radio; super ultradense HII
+ Widespread photoionization + stellar wind cavity; supergiant HII region+ UVOIR -> stars + HII & X-ray-shocked ISM + Starburst required for M*≤ 3x108 Msun, MV> -15
Compact massive star cluster development & feedback: It’s the (re-)radiation!
After Kelsey Johnson 2002, Science, 297, 776; Johnson & Kobulnicky 2003, ApJ, 597, 923
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
Massive stars->> SNe IISSCs =>long lived supermassive star
SNe II feedback: main mechanical power at low metals:
Pmech~ (600km/s)2SN(SFR/dMW/dt)
Mass-loading efficiency & galaxy ISM structure largely determine possible
outflow speeds
SNe key factor in lower mass galaxies with Vesc < 500 km/s
Inevitable Nature of Stellar Energetics
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
Supershells:Blowouts--vent into halos from disks. Hot interior partially confined by cooler shell
Generally initial V(exp) << V(esc);P(z), n(z) critical
Different physics than steady winds!
Weaver et al. 1977, ApJ and later models
Effects on HI vs fate of hot gas?
Mac Low et al. 1989, ApJ, 337, 141
Disk
Halo
More mechanical luminosity: DISK BLOWOUTS
Photoionized surfacesPhotoionized surfaces
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
NUCLEAR STARBURST WIND STRUCTURE
Sustained mechanical energy inputs leads to galactic wind.
Supersonic gas flow upstream of a critical point. Organized outflow
M82 as a nearby example--seen in larger galaxies; matter of scale?
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
NGC 1569 - NIR with WIYN 3.5-m Telescope; Natural Seeing: SF Patterns: SSCs Embedded in Young Star Clouds
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NGC 1569--3 SSCs in ~10 Myr--Large jump in L(mech) associated with
SSCs!
Feedback induced shift in SF mode likely.
Superbubble from SSC A a likely dominant factor
SFR declines as dense ISM exhausted-and ejected? GMC formation vs. destruction?
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
Local views of NGC 1569-- WIYN & HST: multiple super bubbles
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WIYN H +[NII]WFPC2 H +[NII]
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
QuickTime™ and aTIFF (Uncompressed) decompressor
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Kinematic supershells in NGC 1569
M. Westmoquette et al. 2007 in prep
C. Martin 1998, ApJ, 506, 222
HI
HI
NGC1569: SSCs important supershell drivers.
Some likely to escape.
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
Martin, Kobulnicky, Heckman 2002, ApJ, 574, 663
V(HII) ~ 100 km/s--Slow optical wind
High spatial concentration of massive stars powers
hot gas outflow
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
2002, A&A, 392, 473
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NGC1569 HI: starburst small scale relative to HI
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August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
Dwarf dichotomy: gas-rich, slowly evolving vs. gas free
(e.g. Grebel, Gallagher & Harbeck 2003, AJ, 125, 1926)
Nature vs. Nurture.
NGC5253 - gas deficient starburstHI/L ‹ 0.1, MV≈-18
Starburst driving gas removal & transition to NGC205 dE-like
structure???
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
NGC5253-ACS
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
Kobulnicky & Skillman 1995
Summers et al 2000
Harris et al. 2004
Complex multi-phase ISM + persistent cool ISM in presence of intense star formation: Dellenbusch Wisconsin PhD
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
SSC D>17 kpc from NGC3310starburst: MV= -11≈106 MsunClose to tidal debris but no HIGC formation mode?
SDSS: Knapp et al.2006, AJ Tidal debris: Wehner et al. 2006, MNRAS; 2005, ApJL
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August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs
Globulars & Dwarfs: Now &Then
• SSC formation --> starbursts: require Mbary≥108 Msun Triggers for SSCs??
• SSCs in dwarfs usually centrally concentrated (NGC3310!)
• Multiple supershells--inefficient ISM mass loss. More efficient bleeding of metals
• Gas poor starbursts with central clusters (disks)--a final collapse phase of the ISM. Why & how (Kate Dellenbusch PhD)??
• GC formation REQUIRES starbursts in small galaxies
• GCs have wide spatial distribution in dwarfs, not always centrally concentrated; ISM energy deposition reduced
• GC formation not strictkly associated with gas loss--SF extends past GC era
• Denser IGM surroundings may choke winds--affect metal evolution and radiation escape
August 28, 2007
J. S. GallagherU. Michigan-Dwarfs + GCs