Download Disks around low-mass stars in extreme environments

Disks around low-mass stars in extreme environments
HD 93256
O3.5 V
HD 303308
O4 V
HD 93129 O3 If
HD 93128 O3.5 V
η Car
(LBV)
HD 93205
O3.5 V
Tr16-244 O4 I
WR 25 WN6
Thomas Preibisch
© ESO images
www.usm.uni-muenchen.de/ys/
University Observatory
Ludwig Maximilians University
Munich
Science Context: How important is feedback from massive stars ?
Orion Nebula Cluster
R136 / 30 Dor – LMC
Antennae
Consequences of radiative/wind feedback:
●
Less fragmentation? → higher stellar masses ?
→ deficit of low-mass stars ?
●
Destruction of protoplanetary disks ?
Consequences for planet formation ?
Science Context: How important is feedback from massive stars ?
Orion Nebula Cluster
θ1C Ori: SpT = O6
M = 36 M⊙
QEUV ≈ 1049 s-1
Pwind ≈ 100 L⊙
→ Feedback is
not very important
in this cluster
R136 / 30 Dor – LMC
The most massive stars in
starburst clusters produce
much stronger feedback:
Antennae
SpT = O3
M✶ ~ 100 M⊙
QEUV ~ 1050 s-1
Pwind ~ 10 000 L⊙
To study the effect of massive star feedback,
we need to look at more massive = more distant regions
→ requires observations with high resolution & sensitivity
The Great Nebula in Carina
Tr 15
Tr 14
η Car
the galaxy's most
luminous star
D = 2.3 kpc
15 '
10 pc
Tr 16
Orion Nebula
at the same
physical scale
+ 70 O+WR stars (M✶,max ~ 120 M⊙)
Orion Nebula
Carina Nebula
R136 / 30 Dor
2 O stars
70 O+WR stars
~1000 O stars
M✶,max = 36 M⊙
M✶,max ~ 120 M⊙
M✶,max ~ 150 M⊙
large enough to sample the top of the IMF
close enough to study low-mass stars
1'' = 420 AU = 0.002 pc
1'' = 2300 AU = 0.01 pc
1'' = 52 000 AU = 0.25 pc
Carina is the best bridge between
detailed studies of nearby regions and
more massive but more distant extragalactic starburst regions
Spitzer IRAC map shows cloud surfaces
+ a ( highly incomplete! ) sample
of ~ 1500 YSOs
Many dust columns contain
young stellar objects
in their heads
HAWK-I J, H, K
Treasure Chest
Smith et al. 2010:
Scenario of triggered star formation
Detection of the full stellar population
Very deep near-infrared survey with HAWK-I / VLT
3 nights for a 24 field mosaic
in J, H, Ks
Survey area:
1280 square-arcmin
10 σ completeness limit:
J=22.3, H=20.7, Ks =19.7
Detect all young stars
down to 0.075 M⊙ for AV = 25 mag
0.035 M⊙ for AV = 10 mag
Preibisch, Ratzka, Kuderna, Ohlendorf, King, Hodgkin, Irwin, Lewis, McCaughrean, Zinnecker, 2011, A&A 530,A43
HAWK-I J-H-Ks image of the central region
600 336 infrared sources in the Carina Nebula
galactic latitude = -0.6°
> 95% of these are unrelated background objects !
How to distinguish the young low-mass stars
from the millions of old background stars in the field-of-view ?
Solution: X-ray observations
Old star
(like Sun)
Young stars
(< 108 yrs)
X-ray faint:
LX/Lbol ~ 10-6
X-ray bright:
LX/Lbol ~ 10-3
Illustration
infrared image
X-ray image
How to distinguish the young low-mass stars
from the millions of old background stars in the field-of-view ?
Solution: X-ray observations
Old star
(like Sun)
Young stars
(< 108 yrs)
X-ray faint:
LX/Lbol ~ 10-6
X-ray bright:
LX/Lbol ~ 10-3
Illustration
infrared image
X-ray image
Identifying the young stellar population:
The Chandra Carina Complex Project
PI: Leisa Townsley (Penn State)
Total exposure time: 15.6 days
●
14 368 X-ray point sources
●
10 714 Carina members
The first unbiased sample of the
low-mass stellar population.
≥ 80% (50%) complete at ~ 1 M⊙ (0.5 M⊙)
●
Diffuse X-ray emission
Stellar winds (+ supernovae ?)
have filled the super-bubble
with hot plasma.
CCCP Special Issue
Vol. 194, May 2011
The size of the low-mass stellar population
Preibisch et al. 2011, A&A 530, A34
●
●
Number of X-ray detected stars with
mass estimate (from CMD) ≥ 1 M⊙: 3185
78 known stars with M > 20 M⊙
Field-star IMF (Kroupa 2002) prediction
N(M ≥ 1 M⊙)expected ≈ 3500
1 M⊙
There is clearly
no deficit of low-mass stars
0.25 M⊙
IMF(Carina Nebula) ≈ IMF(field) down to 1 M⊙
Field IMF extrapolated down to 0.1 M⊙:
Orion
fa
N✶ ≥ 45 000, M✶,tot ≥ 30 000 M⊙
Carina
ct
or
Carina Nebula > NGC 3603, Arches Cluster
≈ Westerlund 1
16
The Carina Nebula is one of the most massive
clusters known in our Galaxy!
log Lx
Spatial distribution
5 pc
Tr 15
Only the 30% brightest
X-ray members are shown:
Tr 14
Clustering analysis:
Feigelson et al. 2011,
ApJS 194, 9
●
20 principal clusters
(mostly known before)
+31 small groups
→ 5457 X-ray sources
in a clustered population
5271 X-ray sources in
a distributed population
●
(previously unknown)
Tr 16
Characterization of the individual stellar populations: ages
●
Example: Tr 16
AV = 10 mag
Typical age of the
low-mass stars:
~ 3-4 Myr
is well consistent with the
age of the high-mass stars
1 Myr
3 Myr
●
Tr 15: ~ 5-8 Myr
●
Tr 14 (core): ≤ 1-2 Myr
Cluster CMDs are consistent with
the assumption of coeval formation
of high- & low-mass stars
●
Widely distributed population:
range of ages [0 … ~8] Myr
most objects ≤ 4 Myr
10 Myr
Tr 16
●
Ages and circumstellar disk fractions
IR color-color/color-magnitude diagrams
of the X-ray selected populations:
Ages and infrared excess fractions
Tr 16: ~ 3-4 Myr
(7 ± 1) %
Tr 14: ~ 1-2 Myr
(10 ± 1) %
Tr 15: ~ 5-8 Myr
(2 ± 1) %
TCC:
< 1 Myr
(32 ± 5) %
Preibisch et al. 2011, A&A 530, A34
The infrared excess (= disk) fractions
in the clusters in the Carina Nebula are
lower than in other clusters of similar ages!
→ faster dispersal of circumstellar disks due to the harsh environment
see also: Wang et al. 2011, ApJS 194, 11;
Wolk et al. 2011, ApJS 194, 12
From Carina back to Earth:
Implications on the formation environment of our planetary system
The oldest Meteorites in our Solar System contain excesses
in the daughter products of short-lived radionuclides:
26
Al τ½ = 0.7 Myr;
comes from winds of evolved stars,
or supernovae (M✶ ≤ 30 M⊙)
60
Fe τ½ = 2.6 Myr;
only from core-collapse supernovae
Must have been injected into the
proto-solar nebula at most a few Myr
after the formation of our Sun.
Our solar system formed in an environment
containing high-mass stars (M✶ > 30 M⊙)
Problem of many injection scenarios:
In most clusters (e.g., Orion Nebula Cluster),
all stars formed at ~ the same time.
When the first supernova happens (after > 4 Myr),
most low-mass stars have already largely
dispersed their disks
(i.e. planetesimal formation is already finished).
~ 1 Myr
→ no efficient injection of 60Fe possible
Supernovae come too late
~ 2 Myr
~ 3 Myr
~ 5 - 10 Myr
Multiple-generation
triggered star form.
in the Carina Nebula
Thousands of
low-mass stars are
forming today by
radiatively triggered
cloud collapse.
Their protoplanetary
disks contain already
26
Al from the massive
star winds.
Chandra X-ray
optical
Herschel 70 μm
Multiple-generation
triggered star form.
in the Carina Nebula
Within < 1 Myr, the
collapsing protostars
and their
protoplanetary disks
will be enriched
with 60Fe from the
SN explosion of
η Carina.
C O Ni
Hammer et al. 2010,
ApJ 714, 1371
Chandra X-ray
optical
Herschel 70 μm