Science with Laser Guide Stars: Planetary applications ESO - PowerPoint PPT Presentation

Science with Laser Guide Stars: Planetary applications ESO Planetary Sciences Journal Club Tuesday Sep. 11, 2007 C. Dumas C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

Motivation for this presentation: 1) - Call for proposal P81 (NACO + SINFONI) !!! 2) - Overview of VLT LGS system characteristics 3) - Applications to Planetary Sciences 4) - Some results (mainly from Keck) C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

LGS overcomes *some* limitation of adaptive optics • Typical mag limit for NGS AO observations: - Visible WFS: V~14-15 - IR WFS: K~12-13 AO-LGS can be used to study objects with R-mag >~ 18 • Fainter and/or extended objects can be observed using Titp-tilt • Reference within 1 arcmin and R-mag >~18 Correction over a larger field (several arcmin) will need future • MCAO systems (see MAD results). C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

LGS system available with NACO and SINFONI at UT4 C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

Main characteristics of VLT LGS system: • 50cm wide laser beam excites Na (0.589 µ m) layer at 90km altitude • PARSEC (MPE): Continuum laser with output power ~ 10W • Airtcraft detection camera • Artificial star Rmag~ 12 • Increase sky coverage from 1% to nearly 80% • Strehl achieved ~ 20% C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

LGS @ VLT - TTS: R-mag ~ 18/18.5 - Distance from target: up to 1 arcmin - CLR sky (not even cirrus), excellent seeing conditions - Seeing enhancer mode exists (SINFONI), not offered yet, but promising. Will need excellent seeing conditions (no tip-tilt correction). 100% sky coverage!!! - Differential tracking (NACO only) - All main modes offered (imaging, spectroscopy, coronagraphy … NO CHOPPING C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

Gemini North Keck-II Starfire Palomar Hale Lick Observatory C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

Planetary applications: - Study of brown dwarf companions, and surrounding disks - Solar system: - Companions to faint objects (small asteroids, dark asteroids, Trans-Neptunian objects) - Companion to large asteroids - Spectroscopy of faint objects (planetary satellites, TNOs, rings, outer irregular satellites, etc …). LGS improves SNR by concentrating light on fewer pixels. - Selected regions of giant planets’ atmospheres (e.g. polar region) C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

Some stats: About 25 papers since 2005 (Keck) • About 1/3 related to planetary sciences: • Brown dwarfs studies (5 papers) • Solar system (3 papers): satellites of TNOs and • asteroids More papers in preparations (Gemini/VLT/Palomar) • C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

Brown dwarf studies: Liu and Legget, 2005, ApJ 634, 616 1st result with Keck LGS AO. The images of this free-floating L dwarf, Kelu1, reveal its binarity nature, which in turn, explains the peculiar photometric behaviour of this BD. Another paper by Gelino et al. 2006, PASP, 118, 611 reports also Keck AO-LGS monitoring of the Kelu1-AB system, which orbits on a 81deg. Inclined orbit, with a period > 40 years. C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

Brown dwarf studies (Cont’d): Liu et al, 2006, ApJ 647, 1393 LGS-AO at Keck is used to separate the T-dwarf into a tight (~0.1” sep.) binary system. Multi-band photometry reveals the distinctive brightening at J-band for the early/mid T-dwarf types, which is explained as a property of the ultracool photosphere for these objects. Other Keck AO-LGS observations of a cool binary are reported by Siegler et al., 2007, ApJ, 133, 2320, with a separation of 66mas and spectral types of L5 and L7.5 for both components. C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

Brown dwarf studies (Cont’d): Close et al, 2007, ApJ 660, 1492 LGS-AO at Keck is used to resolve two BD binary systems from the Ophiucus star forming region. The wide separation permits to carry out near-infrared spectroscopic measurement of both components. The authors claim that their measured masses for the components of Oph 11 are higher than previously reported by Jayawardhana and Ivanov, and that the system is unlikely to be of planetray mass regime. C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

Solar system studies: Brown et al, 2005, ApJ 632, L45 LGS-AO at Keck is used to resolve the Trans-Neptunian Object 2003 EL61 into a binary system. The satellite orbits the primary in ~49days on an eccentric orbit. The presence of the satellite permits to assess the mass of the system (4.2 10 21 kg), which is evaluated to be ~30% that of Pluto-Charon. C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

Solar system studies (Cont’d): Brown et al, 2006, ApJ 639, L43 The same team usesLGS-AO at Keck is used to search for more binary systems among the TNO population. They recover a second satellite for the 2003EL61 system, and discover a satellite to the largest TNO 2003 UB313 (Eris). The presence of small satellites Around the large TNOs 2003 EL61, 2003 UB313, points to a different formartion mechanism than in the case of Pluto. C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

Solar system studies (Cont’d): Marchis et al, 2006, Nature 439, 565 Again, LGS-AO was used at Keck to image a subset of the population dark Trojan asteroids. The binary object 617 Patroclus was Monitored at several epochs and a very low density of 0.8g.cm 3 was measured (smaller than water ice), pointing to an ice-rich porous interior for this body. C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

Solar system studies (Cont’d): Dumas et al … in preparation First planetray result obtained with the VLT-LGS system. Both satellites of 2003 EL61 are recovered with SINFONI. The image demonstrate the high contrast achieved by the use of LGS (right) wrt seeing-limited observations (left) of the same object. In only 1/2h of integration time both satellites are detected (mag 19 and 20.5 resp). The primary body (R~17) is used to provide tip-tilt reference for the wavefront correction. C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007

Solar system studies (Cont’d): GEMINI result -with LGS-Altair Star formations in Orion C. Dumas, ESO Planetary Sciences Journal Club, Tues. Sep. 11, 2007