Lecture 16: Jets & Outflows I: observations 1 Outline Herbig-Haro objects Optical jets IR outflows Bipolar molecular outflows Radio Jets H 2 emission
3 Schematic Picture of Star- Forming Molecular Cloud Outflows interact with cloud at different distances from source, from < 0.01 to > 1pc.
The importance of outflows Every star produces an outflow for its first 10 5 to 10 6 years, during its YSO stage Outflows interact with their surrounding gas, injecting energy and momentum in cloud. This may help drive turbulence in cloud Energy from shocks can dissociate molecules, heat gas, affect dust thereby triggering chemical reactions that do not (and cannot) occur in the quiescent gas. Outflows can push gas around, create cavities and shells. They can modify their parent cloud s structure (even at great distances from source). Interaction between outflow and circumstellar envelope may help end the infall stage. History of HH object research (I): 1950 s- discovery by Herbig and Haro (Herbig 1951; Haro 1952) HH 1 1970 s- detailed study of HH object spectra showed shock-like spectra in HH objects (Schwartz 1975) late 70 s, early 80 s- proper motion studies revealed velocities of 100-350 km s -1, and bipolarity (non-spherical) aspect of stellar wind. (e.g., Cudworth & Herbig 1979; Herbig & Jones 1981) 0.25 pc HH 2 C-S star HH 1 - HH 2: Herbig & Jones 1981
History of HH object research (II): 0.13 pc 1980 s- CCD surveys of HH objects revealed HH jets originating from young stars (e.g., Mundt & Fried 1983; Mundt et al. 1984) late 1980 s, early 1990 s - Episodic nature of HH flows discussed (e.g., Reipurth 1989; Hartmann et al. 1993) HH 34 - Buehrke et al. 1988 History of HH object research (III): 1990 s- HST images of HH flows 10 3 AU 8
History of HH object research (IV): mid to late 1990 s- wide-field CCD camera surveys of star-forming regions: giant HH flows discovered (e.g., Eislöffel & Mundt 1997; Reipurth et al. 1997) 1 pc 9 HH 315 - Reipurth et al. 1997 History of HH object research (V): mid to late 1990 s- High-res. studies of jet proper motion using HST (e.g., Hartigan et al. 2001; 2005)
History of HH object research (V): From proper motions: v ~ a few x 100 km/s History of HH object research (V): 12
HH knot spectra Hartigan et al. 1999 Herbig-Haro objects Nebulous optical patches located at the end of jets and outflows Interaction of the jet with clumps of gas and dust or dense plugs of material which plough supersonically into a more diffuse medium Often bow shaped Proper motions velocity ~ 300 km/s Some evidence for episodic outflow 14
Herbig-Haro objects and optical jets Optical jets properties: shocked ionized gas (H α, [SII]) low ionization fraction ~10% highly collimated ~ 100:1 dense ~ 10 3 cm -3 fast ~ 300 km s -1 knots along the jet some evidence of precession IR outflow In general, IR flows trace the bow shock flanks
IR Outflow observed by Spitzer Notice the outflow cavity walls traced by the Mid-IR emission. The 17 cavity walls are only seen in the Mid-IR emission, not in optical or near IR. An example of how our knowledge of outflows has changes over the years NGC 1333 (before 1995) Herbig (1974); Aspin et al. (1994) 1.5 pc
NGC 1333 (in 1995) Bally et al. (1996) 1.5 pc 19 NGC 1333 in 2005 Spitzer Image of NGC1333 1.5 pc Gutermuth et al. (2005) 20
History of Molecular (CO) Outflow research (I): 1970 s- detection of extremely highvelocity gas toward star-formation region CO(1-0) spectrum of KL Nebula in Orion - Zuckerman et al. (1976) History of Molecular (CO) Outflow research (II): 1980 s- first molecular outflow maps revealed bipolar wind coincident with HH objects. (e.g., Snell et al. 1980; Rodríguez et al. 1980) Proper Motions: Cudworth & Herbig 1979 CO(1-0) map of L1551 outflow Snell et al. (1980)
Outflow Integrated Intensity Contour Maps: Red Outflow lobe Radio telescope only detects radial velocity (V radial ) component Line of sight V radial V tangential Blue Outflow lobe Intensity Velocity Intensity Redshifted lobe Velocity Blueshifted lobe Resolution matters! 21 beam HH211 Outflow Greyscale: NIR image Contours: CO (2-1) 1.5 beam
Molecular Outflows Low density molecular gas seen at high velocities 10-50 km s-1 Mainly 12C16O(J=1-0) 2.6mm line, collisionally excited Red and blue wings spatially separated bipolar flow Usually poorly collimated length/width ~ 2 Extent ~ arcmins sizes ~ 0.1-3 pc Masses ~ 0.1-100 M! 25 http://www.cfa.harvard.edu/sma/press/2009/imagecontest/images/sma_contest_qiu-v.jpg Radio Jets 26