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Astronomy 405 Solar System and ISM. Lecture 20 Star Formation and Star Forming Regions March 1, 2013. How do we know?. Young stars are seen near molecular clouds. - PowerPoint PPT Presentation
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Astronomy 405Solar System and ISM
Lecture 20
Star Formation and Star Forming Regions
March 1, 2013
How do we know?
• Young stars are seen near molecular clouds.• In infrared light, we can see into the deeper
regions of clouds, and see clusters of young stars with circumstellar material (dust and gas) surrounding them.
• Stars do not live forever, so they must be continuously formed in our galaxy.
Giant Molecular Clouds• Cool: < 100 K
• Dense: 102 – 105 H2 molecules/cm3 (still less dense than our best vacuum)
• Huge: 30 – 300 lyrs across, 105 – 106 solar masses
• CO molecular emission & dust emission trace structure 100 degrees
Infrared image from IRAS
Young Stars
Bright, hot newborn star, partially shrouded by dust
Other newborn stars, reddened by dust
After Shu et al. 1987,Shu et al. 1993
isolated, quasi-static, unbound, isothermal core
Cartoon of Star Formation
simple /Bfield
disk & outflow due to angular momentum
clearing of envelope by wind
grav collapse opposed by turbulence, B field, thermal
planetary system?
Class 0: Youngest stellar objects (> 10 um) Cold black body
Deeply embedded Envelope dominated emission
fux
V IR mm
Class I: Embedded Strong disk and envelope contribution
fux
V IR mm
fux
V IR mm
Class II: Disk dominated Stellar contribution
fux
V IR mm
Class III: Stellar dominated Little dust contribution
Starless cores and protostars with inward (collapse) motions(Gregersen et al. 1997, Mardones et al. 1997, Tafalla et al. 1998, Lee et al. 2001 )
YSO outflows
Alves et al. 2001, O’Dell et al. 1994, Chen et al. 1998, Jayawardhana et al. 1998, Padgett et al. 1999, Burrows et al. 1996, ESO 2000
Majority of T Tauri stars have disks (e.g. Beckwith & Sargent 1996)
HR 4796
HH34
The Expansion of HH30’s Jet
Scattered/Absorbed Light Disks
Massive Star Formation
The Large Magellanic Cloud
Spitzer Space Telescope
• 0.85 meter infrared telescope
• Launched in August 2003
• Cooled to ~1.5 K
MIPSPI: Rieke (UofA)
Imaging at 24, 70, 160 m
IRACPI: Fazio (CfA)
Imaging at 3.6,
4.5, 5.8, 8.0 m
IRSPI: Houck (Cornell)
Spectrographs (4)
5.3-38 m
Spitzer mosaic of the LMC - SAGE
Meixner et al.
Identification of YSOs in the LMC
AGB
Stars
Galaxies
Step 1 (DM of the LMC= 18.5)
Gruendl & Chu 2009, ApJSGruendl & Chu 2009, ApJS
High-mass YSOs
Intermed-Mass YSOs
Step 2
H+CO dss-r H 2MASS J
2MASS K 3.6 4.5 5.8
8.0 24 70
Step 2
H+CO dss-r H ISPI J
ISPI K 3.6 4.5 5.8
8.0 24 70
Step 2
H+CO dss-r H ISPI J
ISPI K 3.6 4.5 5.8
8.0 24 70
Step 2
H+CO dss-r H ISPI J
ISPI K 3.6 4.5 5.8
8.0 24 70
Massive YSO Candidates in the LMC
Source [8]>8 [8]<8
YSO 858 234YSO 303 14YSO 167 >4M >10M
Neb 126 13AGB 110 105PNe 52 9
Galaxy 947 6Galaxy? 126
How Do We Know We Are Right?
• Cycle 4 IRS follow-up observations of ~270 YSO candidates confirmed 95% of them (Seale et al. 2009, ApJ, 699, 150).
• 13 H2O maser sources found coincidence in ~10.
• Identified ~ expected number of background galaxies.
Gravitationally Unstable Regions
<1 (blue)
Gravitationally Unstable Regions
Rafikov 2001
Chen et al. 2009, ApJ, 695, 511
Star Formation in Superbubble N44
3.6, 8.0, 24 um
HST H ISPI J ISPI K SED
A Closer Look at YSOs’ Environments
20" 20"
HST H ISPI J ISPI K SED
A Closer Look at YSOs’ Environments
20" 20"
HST View of YSOsHST View of YSOs’’ Environments Environments
(1)(1) dark clouds, (2) bright-dark clouds, (2) bright-
rimmed rimmed
dust pillars, (3) small compact dust pillars, (3) small compact
HII.HII.
Evolutionary Sequence.Evolutionary Sequence.
YSOs in 30 DorRed: [8.0]< 8 ; Green: [8.0]>8 ; Yellow: [8.0]>8, star + CSD or cHII
HST Images of 30 Dor are availableHST proposals due today at 7pm