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Stellar water fountains Hiroshi Imai (Kagoshima University) Contents Discovery and identification of the water fountains Properties of the water fountains.

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Presentation on theme: "Stellar water fountains Hiroshi Imai (Kagoshima University) Contents Discovery and identification of the water fountains Properties of the water fountains."— Presentation transcript:

1 Stellar water fountains Hiroshi Imai (Kagoshima University) Contents Discovery and identification of the water fountains Properties of the water fountains and circumstellar envelopes –Stellar evolution and the water fountains –Corkscrew jets? Equatorial flows? –Precursors of water fountains? Stellar kinematics in the Galaxy Earlier than the water fountain phase Summary

2 From spherically symmetric to asymmetric mass loss flow When/how is a bipolar jet launched in the final stellarevolution? Betelgeuse NASA Egg Nebula NASA

3 First high velocity flow seen in water maser emission W43A (Genzel & Downes 1977) This is an extremely interesting source, probably a late-type star. but might be a young stellar object? This is an extremely interesting source, probably a late-type star. but might be a young stellar object?

4 Water fountains in AGB/post-AGB phases Associated with evolved stars Faster than expansion velocity of OH maser shell (V exp >> 30 km/s) W43A IRAS IRAS High velocity H 2 O maser sources (Likkel et al. 1992) High velocity H 2 O maser sources (Likkel et al. 1992)

5 10 water fountains identified to date –W43A (Diamond et al. 1985; Imai et al. 2002, 2005; Vlemmings et al. 2006) –IRAS (Imai et al. 2004; 2007) –IRAS (Sahai et al. 1999; Morris et al. 2003; Claussen et al. 2004) –OH (Boboltz & Marvel 2005) –IRAS (Imai et al. 2007) –IRAS (Imai et al. 2007) –IRAS (Deacon et al. 2007) –IRAS (Deacon et al. 2007) –IRAS (Deacon et al. 2007) –IRAS (Deacon et al. 2007)

6 W43A: First identification of a water fountain in maser images Imai et al Nature 417, 829 Imai et al Nature 417, 829 Periodic OH maser variation (P~360 days) (Hertman & Habing 1985) Jet velocity =145 km/s, dynamical age ~50 yr Periodic OH maser variation (P~360 days) (Hertman & Habing 1985) Jet velocity =145 km/s, dynamical age ~50 yr

7 Quenching water fountain within < 1000 years Continuum radio emission (=planetary nebula) and H 2 O/OH masers in K3-35 (Miranda et al. 2001) Photodissociation destroying H 2 O molecules Collimated jet before full photoionization Dispersing water fountain in Pre-PN phase Photodissociation destroying H 2 O molecules Collimated jet before full photoionization Dispersing water fountain in Pre-PN phase 5000 AU

8 IRAS Optically visible in pre-planetary nebula (PPN) phase Flow dynamical age ~50 years Imai et al. (2007) HST image km/s km/s

9 Dynamical ages < 100 years IRAS (Morris, Sahai & Claussen 2003) IRAS (Morris, Sahai & Claussen 2003) OH (Boboltz & Marvel 2005) OH (Boboltz & Marvel 2005)

10 W43A: AGB phase No nebulosity, detected by SPITZER GLIMPSE (Deguchi et al. 2007) OH maser shell (R~500 AU, V exp =9km/s) SiO maser detection (Nakashima & Deguchi 2002) Dust envelope radius < 3000 AU Dynamical age T~ 260 yr (OH), 1600 yr (dust)

11 W43A details: Jet precession Precession period ~55 years Precession angle amplitude ~5° (10-year scale) length growth speed (1-year scale) maser feature proper motions Imai et al. 2005

12 Magnetohydrodynamical (MHD) jet Zeeman effect and linear polarization (Vlemmings, Diamond & Imai 2006, Nature 440, 58)

13 Bow shock? Spiral flow? (VLA) 500 AU at 8 kpc (VLBA) Imai et al. (2004) Imai et al. (2007) IRAS

14 Corkscrew jets? Bow shocks? W43A (Imai & Diamond in prep) IRAS (Sahai et al. 2005)

15 Biconical SiO maser flow (~15 km/s) | within 10 AU | H 2 O maser jet (Imai et al. 2005) (Imai et al. in prep.) Biconical SiO maser flow (~15 km/s) | within 10 AU | H 2 O maser jet (Imai et al. 2005) (Imai et al. in prep.) SiO/H 2 O and continuum locations Where is a disk? Equatorial flow?

16 Proper motion in the equatorial flow W43A (Imai & Diamond in prep) W43A (Imai & Diamond in prep) Flow velocity ~30 km/s

17 New water fountains IRAS (Deguchi et al. in prep.) IRAS (Deguchi et al. in prep.)

18 New water fountains IRAS (Deguchi et al. in prep.) IRAS (Deguchi et al. in prep.) Equatorial flow ? (see Miyajis talk) Equatorial flow ? (see Miyajis talk)

19 Maser source astrometry with position-reference QSO Galactic rotation H 2 O masers in IRAS (Imai et al. 2007)

20 Annual parallax and Galactic rotation

21 Location and velocity in the Galaxy IRAS (Imai et al. 2007) IRAS (Imai et al. 2007) –Annual parallax distance = kpc –Location: (R, θ, z)=(7.4 kpc, 62deg, 650 pc) –3D velocity (V R, V θ, Vz) =(3, 125, 8)[km/s] Travel time from the Galactic plane > 7.7 x 10 7 years >> M * < 5 M sun c.f. Progenitors of bipolar nebulae may be higher mass stars located near the Galactic plane.

22 Summary Magneto-hydrodynamical Corkscrew/precessing jet V> 100 km/s, T~100 years Magneto-hydrodynamical Corkscrew/precessing jet V> 100 km/s, T~100 years Equatorial flow V~ km/s Evolution from AGB flow? Equatorial flow V~ km/s Evolution from AGB flow? M * < 5 M sun single AGB/post-AGB star (or binary <10 AU?) M * < 5 M sun single AGB/post-AGB star (or binary <10 AU?) Only 10 water fountains in the whole Galaxy? Only 10 water fountains in the whole Galaxy?


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