physical conditions and feedback in intense star forming environments
DESCRIPTION
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. M82 view from the ground: - PowerPoint PPT PresentationTRANSCRIPT
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)
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
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.