Physical Conditions and Feedback in Intense Star Forming Environments

Physical Conditions and Feedback in

Intense Star Forming Environments

J. Gallagher-U. Wisconsin

L. J. Smith- Univ. College London

R. W. O’Connell- U. Virginia

May 2004 STScI Workshop

J. Gallagher & L. J. Smith

M82F

M82: 3.5-m WIYN Telescope I-band

M82 view from the ground:

A VERY disturbed galaxy--bright with complex structure: dust and superimposed “stars”

1 arcsec ≈20 pc

M82-A1

M82-F & L

Age = 60 20 Myr

WH

T s

pec

tros

cop

y: G

alla

gher

& S

mit

h 1

999,

MN

RA

S, 3

04, 5

40

25 a

rcsec

HST angular resolution essential to measure sizes!

430 p

cM82-F

€

M = 7.5σ 2r(half mass)

Gr(half mass) = 3.3 pc

σ =13.4 km /s

M =1.2 ×106 MsunSm

ith

& G

alla

gher

200

1, M

NR

AS

, 326

, 102

7M82-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?

Smit

h &

Gal

lagh

er 2

001,

MN

RA

S, 3

26, 1

027

L/M vs age of super star clusters Appears to

lack low mass stars!

32

1

0.1

M_min

M82-F

Cluster Dynamical Evolution: Mass Segregation

€

tmass ∝ trhm * / mu* ≤ 0.1trh

Compact young star clusters may be unstable against

mass segregation effects. Primordial mass segregation

potentially amplified. IMF & survival complex relationship.

M82-F as example. Appears likely candidate for disruption. Did low mass

stars ever form?

M82-Chandra X-ray vs HST NIC IR: X-Ray Binaries & SSCs?

Kaa

ret

et a

l. 20

04 M

NR

AS,

348

, L28 XRBs not

concentrated in SSCs: ejection? Implications for intermediate mass

BH growth?

10 x sharper view with HST:

“Stars” brightest super star clusters-stellar energy inputs on scales too small to measure from the ground.

Complex gas outflows & dust lanes; the violent atmosphere of a starburst

STScI-PRC2001-08bR. de Grijs

M82 A1

WFPC2 BVI+H

STIS spectroscopy of starbursts:

• resolve compact clusters from background and each other--close projected packing in starburst clumps.• high spectral resolution-advantage of diffraction-limited optics. Allows charting of substructures confused at ground-based resolutions.• Access to key lines, e.g., [OII] and [OIII] for empirical emission line abundances and Balmer jump absorption edge for ages.

M82 A1: A luminous compact star cluster in region A--WFPC2 “V” Image

170 pc

STIS slit position

O’Connell et al.GO 9117

L. J

. Sm

ith

et

al. 2

004

in p

rep

[NII]+H [SII]

STIS

Clu

ster

M8

2-A

1

Sm

ith

et

al 2

004

in

p

rep

Wavelength ->

Dis

tan

ce a

lon

g sl

it -

>

Smooth line profiles: projected random velocity fields relatively uniform.

[NII]+H [SII]

STIS

Clu

ster

M8

2-A

1

Sm

ith

et

al 2

004

in

p

rep

Dis

tan

c e a

lon

g sl

it -

>

Compact HII around M82-A1

FWHM size of M82-A1continuum ~0.3 arcsec=5 pcHII region slightly larger, ~10 pcExample of luminous, evolved, but compact HII region

M82 STIS [SII] Emission Lines

Nearly equal intensities-> ne≈1000 cm-3

Moderate I([SII])/I(H)=0.2 consistent with photoionization

High mean thermal pressure: P/k ≈107

Starburst: Fragmented ISM

Clouds embedded in low density hot, high pressure ISM: HII dominated by thin ionization fronts on dense, complex

and often dusty clouds. ISM not static. Ionized gas has complex morphology and velocities.

M82 STIS H + [NII] Emission

Lines rather broad; fwhm observed =2.8 Å -> HII velocity dispersion ≈35

km/s.

High turbulence=good environment for making

SSCs

Flu

x

0

10

20

30

40

50

60

70

80

HII Diffuse Shells M82

H F

WH

M (

km

/s)

Type of Ionized Region (Hunter & Gallagher 1997, ApJ, 475, 65)

WFPC2-H

WFPC2-V

Shocked high pressure ISM

Density boundedHII shell

RadiationboundedO++ zone

Soft H-ionizing radiation

Hot young SSC with stellar wind bubble

A theoretical idea:

Off center HII region from ISM

superwind

Possibility: Compact star clusters=Positive Star Formation Feedback?

To remain bound after star formation, require that ≥30% of mass in cloud center converted to stars.

Normal star formation efficiencies are <10%

Connection possible between intense star formation and high rates of star

cluster formation?Cluster Dominated Star Formation

= Efficient Star Formation Higher SFR/Molecular Cloud

Production Rate

Impacts of energy & mass outflows from starbursts

mass ejection vs. star formation rates preferential loss of metals from SNe structure of outflows--cooling rates mixing into IGM vs. infall & recapture stimulated star formation within &

beyond starburst zones ISM sweeping in companion galaxies

WIYN Narrow & broad band images: M82 Superwind

Stellar diskcontinuum

New perspectives on M82 superwind from the combination of WIYN 3.5-m & HST broad- and

narrow-band images

HST: 0.05 arcsec resolution, moderate surface brightness sensitivity, especially in narrow band filters.

WIYN: 0.5-1 arcsec resolution with excellent narrow band surface brightness sensitivity over wider FOV.

Dramatic?!!

M. W

estm

oque

tte

(UC

L),

J. G

alla

gher

(U

W),

L. J

. Sm

ith

(UC

L)

Wit

h N

ASA

/ES

A a

nd W

IYN

Obs

erva

tory

/NS

F

M82: HST WFPC2 + WIYN

M. W

estm

oque

tte

(UC

L),

J. G

alla

gher

(U

W),

L. J

. Sm

ith

(UC

L)

Wit

h N

ASA

/ESA

and

WIY

N O

bse

rvat

ory/

NSF

M82: HST WFPC2 + WIYN

Connections between scales: Kpc-size winds driven by 10 pc massive, compact

star clusters: energizing multiple nozzles=“shower head” wind

Tenorio-Tagle, Silich, Munoz-Tunon 2003 ApJ, 597, 279

Radio VLA + MERLIN: Wills et al. 1999, MNRAS, 309, 395

HST P NICMOS NIC GTO:Alonso-Herrero et al. 2003,

AJ, 125, 1210

M82: The Multi-Wave Poster Galaxy

Chandra x-ray with H + [NII] WIYN contour overlay--approx alignment

N

E

Not a simple wind in hollow cone--no limb brightening in optical emission, instead optical and x-ray emission nearly coincident. Multiple small flows escaping from ISM “tunnels” to form multi-stream cosmic “shower” vs. uniform wind?

NGC 3077: WFPC2 Studies-Stars, Gas & Feedback:

Confined outflows? Where are the Shocks?

D. Calzetti et al. 2004, AJ, 127, 1405

F300W H

NGC3077:

Shells & narrow shocks (black) from WFPC2 imaging emission line ratios.Shells: Martin (1998--polygons); CO Walter et al. (2002--ellipses)

Calzetti et al. 2004, AJ, 127,1405

Summary

High angular resolution reveals super star clusters as common star formation mode in starbursts:

• formation of 100s-1000s of massive stars in <1 Myr• maximum density star formation mode; requires <10 pc resolution • focused inputs of UV & mechanical power sources• positive feedback through dynamic, high pressure ISM?

HST reveals small-large scale connections in starbursts

• starburst clumps sources of unsteady outflows traced in ionized gas• shocks & compact ionization fronts; small intrinsic scale.• chemical enrichment of surroundings--how does mixing occur?

Intense star formation is not a simple scale-up of processes

commonly observed in galactic disks. Models exist and require

observational tests.

Only HST offers the combination of wavelength agility, angular resolution (WFPC3; HRC!+NIC),

and spectroscopy STIS (+COS! For winds) to study critical small scale structures and

processes in the nearest starbursts through optical photometric (r, L())& spectral line diagnostics (absorption [star clusters] & emission [nebulae] lines). A baseline for

astrophysics of distant galaxies.