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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