Astronomy 405 Solar System and ISM

1. Astronomy 405Solar System and ISM Lecture 20 Star Formation and Star Forming Regions March 1, 2013

2. 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.

3. 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

5. Young Stars Other newborn stars, reddened by dust Bright, hot newborn star, partially shrouded by dust

7. l Class 0:Youngest stellar objects (> 10 um) Cold black body Deeply embedded Envelope dominated emission fux l l l V IR mm Class II:Disk dominated Stellar contribution Class I:Embedded Strong disk and envelope contribution fux fux fux Class III:Stellar dominated Little dust contribution V IR mm V IR mm V IR mm grav collapse opposed by turbulence, B field, thermal Cartoon of Star Formation isolated, quasi-static, unbound, isothermal core simple W/Bfield disk & outflow due to angular momentum planetary system? clearing of envelope by wind After Shu et al. 1987,Shu et al. 1993

8. 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 Majority of T Tauri stars have disks (e.g. Beckwith & Sargent 1996) HR 4796 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 HH34

9. The Expansion of HH30’s Jet

10. Scattered/Absorbed Light Disks

11. Massive Star Formation

12. The Large Magellanic Cloud

13. Spitzer Space Telescope • 0.85 meter infrared telescope • Launched in August 2003 • Cooled to ~1.5 K IRAC PI: Fazio (CfA) Imaging at 3.6, 4.5, 5.8, 8.0 m MIPS PI: Rieke (UofA) Imaging at 24, 70, 160 m IRS PI: Houck (Cornell) Spectrographs (4) 5.3-38 m

14. Spitzer mosaic of the LMC - SAGE Meixner et al.

15. Identification of YSOs in the LMC Step 1 (DM of the LMC= 18.5) High-mass YSOs Intermed- Mass YSOs AGB Stars Galaxies Gruendl & Chu 2009, ApJS

16. Step 2 H+CO dss-r H 2MASS J 2MASS K 3.6 4.5 5.8 8.0 24 70

17. Step 2 H+CO dss-r H ISPI J ISPI K 3.6 4.5 5.8 8.0 24 70

18. Step 2 H+CO dss-r H ISPI J ISPI K 3.6 4.5 5.8 8.0 24 70

19. Step 2 H+CO dss-r H ISPI J ISPI K 3.6 4.5 5.8 8.0 24 70

20. Massive YSO Candidates in the LMC Source [8]>8[8]<8 YSO 858234 YSO 303 14 YSO 167 >4M >10M Neb 126 13 AGB 110 105 PNe 52 9 Galaxy 947 6 Galaxy? 126

21. 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.

22. Gravitationally Unstable Regions <1 (blue)

23. Gravitationally Unstable Regions Rafikov 2001

24. Star Formation in Superbubble N44 3.6, 8.0, 24 um Chen et al. 2009, ApJ, 695, 511

25. A Closer Look at YSOs’ Environments HST H ISPI J ISPI K SED 20"  20"

26. A Closer Look at YSOs’ Environments HST H ISPI J ISPI K SED HST View of YSOs’ Environments dark clouds, (2) bright-rimmed dust pillars, (3) small compact HII. Evolutionary Sequence. 20"  20"

27. YSOs in 30 Dor Red: [8.0]< 8 ; Green: [8.0]>8 ; Yellow: [8.0]>8, star + CSD or cHII HST Images of 30 Dor are available HST proposals due today at 7pm