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


WLM-dIrrLuminous GCMV=-8.8WFPC2 studyHodge et al. 1999, ApJ, 521, 577

August 28, 2007


H1

H2

H3

NGC 147WIYN V-bandHodge clusters: inner & outer locationsHodge 1977, AJ, 81, 25

August 28, 2007


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


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


A

B

10

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


+ 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


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


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


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


NGC 1569 - NIR with WIYN 3.5-m Telescope; Natural Seeing: SF Patterns: SSCs Embedded in Young Star Clouds

B

A

SSCs10

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


Local views of NGC 1569-- WIYN & HST: multiple super bubbles

M. W

est

moqu

ett

e, K

. Exte

r, L

. Sm

ith

, J. G

alla

gher-

-2007

in p

rep

WIYN H +[NII]WFPC2 H +[NII]

August 28, 2007


QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

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


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


2002, A&A, 392, 473

B A

NGC1569 HI: starburst small scale relative to HI

QuickTime™ and aTIFF (LZW) decompressor


August 28, 2007


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


NGC5253-ACS

August 28, 2007


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


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





August 28, 2007


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


Starbursts, Globular Clusters, and Dwarf Galaxies: What's Gone with the Winds?

Documents

Transcript of Starbursts, Globular Clusters, and Dwarf Galaxies: What's Gone with the Winds?