APPLICATION FOR OBSERVING TIME

Transcription

1 Strategic TAC for Max Planck Institute for Astronomy (MPIA) Königstuhl 17 D Heidelberg / Germany Application No. Observing period F 2013 Received APPLICATION FOR OBSERVING TIME from X MPIA X September Jaunary Telescope: LBT X 2.1 Applicant Dr. Albert Conrad MPIA Name Institute Koenigstuhl 17 Heidelberg street Germany country ZIP code - city aconrad@mpia.de 2.2 Collaborators Drs. I. de Pater & K. de Kleer U.C. Berkeley name(s) Dr. Lisa Kaltenegger name(s) institute(s) MPIA institute(s) 2.3 Observers Conrad, de Kleer, de Pater Hinz, Strutskie name S-TAC points out that by specifying the names under item 2.3 it is obligatory to also send out these observers to Mt. Graham. Correspondence on the rating of this application will be sent to the applicant (P.I.) as quoted under 2.1 above. name 3. Observing programme and method: Category: F Title Abstract : : High-Resolution Imaging of Volcanoes on Io Io is the most volcanically active body in our Solar System and stands as a very interesting template for hot rocky exo-planets which can give us a first insight into the potential atmospheric composition of small rocky lava worlds. However, despite several spacecraft encounters and groundbased monitoring for 40 years, we still lack a basic understanding of Io s volcanic activity. Two factors will provide an opportunity this winter to resolve volcanic features on Io down to 100 km resolution, providing improvements on Io during opposition of order 3-4 over previous observations. Using LMIRcam at LBTI we will thus more accurately: (1) pinpoint the source of volcanoes thermal emission and (2) determine the extent of the emission region. 4. Instrument: LBTI/LMIRcam Method: Imaging 5. Brightness range of objects to be observed: from 5.2 to 5.8 V-mag 6. Number of Hours: applied for already awarded still needed no restriction grey dark 7. Optimum date range for the observations: Usable range in local sidereal time LST:... 3h 16h

2 8a. Description of the observing programme Astrophysical context Io is the most volcanically active body in our Solar System. However, despite several spacecraft encounters (Voyager, Galileo, Cassini, and New Horizons) and groundbased monitoring for 40 years, we still lack a basic understanding of Io s volcanic activity. For example, although we do know that Io s volcanic activity is caused by the strong tidal heating that is induced by the orbital eccentricity forced by Jupiter and the 4:2:1 Laplace resonance between Io, Europa, and Ganymede, details of this process are still unknown. We do not know, for example, where and how the heat is dissipated, nor do we know whether Io s heat flow is steady or episodic. These questions can be addressed through long-term monitoring programs, such as that described in our other proposal requesting time on a single eye. Another basic question that we hope to address through this proposal is that of the eruption style, evolution, and eruption mechanism. Typical volcanic eruptions on Earth have temperatures of 1470 K; many eruptions on Io have been found at similar or lower temperatures. However, eruption temperatures as high as 1700 K have been reported at Pele, indicative of an ultramafic composition (McEwen et al., 1998), which is associated with a style of volcanism that on Earth only occurred early in its history (Matson et al., 1998). Peak effusion rates on Io may reach 10 6 m 3 /s (Davies, 2007). A more typical effusion rate is closer to 10 4 m 3 /s (e.g., the eruption at Pillan in 1997 Davies, 2007), which might be similar to that of terrestrial flood basalts tens of millions of years ago. Thus, the amount of magma emplaced on Io, and the extreme high eruption temperature make Io into a volcanic laboratory that allows processes that are long-extinct on Earth and Mars to be studied. In addition the different composition of such lava leads to insights into the diversity of rocky exoplanets and moons and provides input to atmospheric models of such planets. Such hot, close by rocky planets will be among the first rocky planets that can be characterized remotely. Such atmospheres should give insight into the composition of rocky planets and therefore also planet formation. Io can serve as a template for such worlds. Even though it is too small to maintain a dense atmosphere like bigger rocky exoplanets that orbit close to their stars would, the composition of its lava can serve as insight to models for such planetary atmospheres (Miguel et al., 2011). Therefore observations of Io provide essential information for models of hot rocky exoplanets. Immediate aim Using LMIRcam on the LBTI we intend to accomplish two things: 1) pinpoint the source of a volcano s thermal emission with much higher accuracy than has been possible in the past, and 2) determine the extent of the emission region. Two factors will provide an opportunity this winter to resolve volcanic features on Io down to 100 km resolution, down by a factor of 3-4 from the previous best high resolution images on 10-m telescopes. First, there exists a new capability to coherently combine the L-band AO-corrected images of the two 8.2 meter LBT mirrors to produce a 23-meter baseline (Leisenring et al. 2012). In addition, by observing Io during a particularly close opposition this Dec. 2013, when its angular diameter is 1.2 rather than the typical 0.9, the relative resolution compared to previous observations can be increased further. These two factors combined provide a 3-4 fold improvement (4/3 23/8) over typical past ground-based resolution as shown in figure 1. Previous work Our team has been making ground-breaking observations of Io for over a decade. These observations include our complete mapping of the Ionian surface using NIRC2 at Keck in (Le Mignant et al., 2002; Marchis et al., 2005). Since that initial demonstration of the power of adaptive optics to continue Io monitoring from the ground (since spacecraft visits are no longer being conducted by NASA or ESA), we have published 10 articles reporting our analysis of Io data (Keck and more recently Gemini) in the refereed literature, with several more papers in prep, as well as numerous conference proceedings/abstracts. These include spatial mapping of sulfur monoxide gas (de Pater et al. 2007) and SO2-ice (Laver and de Pater, 2008, 2009), and demonstration of novel techniques to reveal a more complete view of all Ionian volcanoes (de Pater et al. 2004). Layout of observations We request on four successive nights, two hours per night. We will image Io at 3.8 and 4.7 um (L and M). This spacing will provide sufficient time to set-up using this newly commissioned mode and will provide the opportunity to observe specific volcanoes at paralactic angle variation (Conrad et al. 2011) sufficient to perform image reconstruction (a feat valuable scientifically as above, and also of significant public relations value for our community). Thermal emission ( K) peaks in the 3-5 um range of the infrared; this window thus maximizes the fraction of flux coming from thermal emission, while still being sensitive to the hottest (1500+ K) eruptions. While the thermal emission from active hot spots can vary considerably from night to night, the net flux from the surface in non-active regions is quite stable. Still, we request occasional observations of photometric standard stars on photometric nights for flux calibration. Strategic importance for MPIA LBT is poised to make a break-through with L-band imaging with the 23-meter baseline. Io at this close opposition is the ideal scientific demonstration. This is an excellent opportunity for MPIA to gain the advantages of leading this ground-breaking observation.

3 8b. Figures and tables Figure 1: These images, at L-band with Altair/NIRI on Gemini North, were taken when Io subtended about 0.9 arseconds. Given the approximately 100 mas diffraction limit at L on an 8-meter, resolution down to about 400 km is achieved here. By observing Io at an unusually close opposition this winter, when it subtends 1.2 arcseconds, and using the 23 meter baseline of LBT, we improve by a factor of 3-4 to push resolution at L- band to just above 100 km at opposition. Note that Io will not be this large on the sky again until UT date transit time (UT) sub-e long UT date transit time (UT) sub-e long 2013-Dec-01 10: Dec-02 10: Dec-06 10: Dec-07 10: Dec-08 10: Dec-09 09: Dec-10 09: Dec-26 08: Dec-27 08: Dec-28 08: Dec-29 08: Dec-30 08: Dec-31 08: Jan-01 08: Jan-02 08: Jan-05 07: Jan-06 07: Jan-07 07: Jan-08 07: Jan-23 06: Jan-24 06: Jan-25 06: Jan-26 06: Jan-27 06: Jan-28 06: Jan-29 06: Jan-30 06: Jan-31 06: Table 1. We request 4 consecutive or nearly consecutive nights. On each night we request a a four-hour block centered about the transit time. (Transit times have been rounded to the nearest hour.) A selection with the sub-earth longitude of one or more nights near that of the Loki volcano (i.e., latitude 310) would be preferable. Nights when Io is too close to the moon and/or occulted by, or too close to, Jupiter have been excluded.

4 9a. Objects to be observed (Objects to be observed with high priority should be marked in last column. Please limit the number of targets in this list to max. 30) Designation α (2000) δ (2000) magnitude in spectral range to be observed priority Io (J1) 07 h 09 m 14 ṣ a approx. 8 b 1 a This is the RA/Dec on 1.jan.2014 when the subtended angle for Io is at a maximum for this opposition (1.197 arcseconds). The RA/Dec vary by up to about 0.5 degrees on the sky (and the subtended angle by a few percent) during this optimal viewing period between 01.nov.2013 and 01.mar b L-band 8th magnitude (approx. depending on volcanic activity at the time of the observation.) 9b. Comments on the selection of target sample: Io is the only possible object for this campaign.

5 10. Justification of the amount of observing time requested: We request four nights, four hours per night when Io is well-positioned (see section 11 below and table 1). This spacing will provide sufficient time to set-up using this newly commissioned mode and will provide the opportunity to observe specific volcanoes at paralactic angle variation (Conrad et al. 2011) sufficient to perform image reconstruction (a feat valuable scientifically as above, and also of significant public relations value for our community). We will use lucky-phasing to image Io at 3.8 um (L ) and 4.7 um (M). We will always observe at L, and occasionally include M if and when we see a strong erruption. By including the second filter we can estimate the black body temperature. Temperature gives us an important clue toward determining composition. 11. Constraints for scheduling observations for this application: Io is a late object, with airmass below 1.6 starting near 0800 UT (approx. 5 hours before sunrise) in early November, centered at opposition late December, then becoming an early object going to airmass below 1.6 by 0500 UT (approx 4 hours after sunset) by end of January. To best observe a particular volcano we chose dates at which its longitude is near the Earth sub-longitude as Io transits. For example, Loki is near latitude 310 and the Earth sub-longitude for Io is 320 at 8 UT on 2014.jan.02 which is near the time of transit. This allows us to image Loki from two hours east to two hours west on that night. With the declination of Io currently above 20 north, this gives us a range in paralactic angle of approximately 100 degrees. On any night we can observe those volcanoes available within the Earth-facing hemisphere, but we ideally target those nights on which volcanoes known to have strong eruptions are facing Earth as Io transits. See table Observational experience of observer(s) named under 2.3: (at least one observer must have sufficient experience) de Pater has over 100 hours observing Io with Keck, Gemini, and HST. Conrad has approx 10 hours observing Io at Keck, and over 100 observing Solar System objects with Keck and Gemini North and South. The participating LBTI instrument team, Hinz and Strutskie, are of course the most experienced of anyone for sing LMIRcam for this observation. 13. MPIA runs (preferably during the last 3 years) and publications resulting from these Telescope instrument date nights success rate publications None

6 14. References for items 8 and 13: Conrad, A. et al. Observing Io at high-resolution from the ground with LBT (2011): DPS-LPSC, 795 Davies, A. et al. Thermal signature, eruption style, and eruption evolution at Pele and Pillan on Io (2001): JGR 106, Davies, A. Volcanism on Io: A Comparison with Earth (2007): Cambridge University Press de Pater, I. et al. Spatially resolved observations of the forbidden SO a XΣ rovibronic transition on Io during an eclipse and a volcanic eruption at Ra Patera (2007): Icarus 156, 296 de Pater, I. et al. Keck AO observations of Io in and out of eclipse (2004): Icarus 165, 137 Laver, C., and I. de Pater Spatially Resolved SO 2 Ice on Io, observed in the near IR (2008): Icarus 195, 752 Laver, C., and I. de Pater, The global distribution of Sulfur Dioxide ice on Io, observed with OSIRIS on the W. M. Keck telescope. (2009): Icarus 201, 172 Le Mignant, D. et al. Io, the movie (2003): SPIE 4834, 319 Leisenring, J. M. et al. On-sky operations and performance of LMIRcam at the Large Binocular Telescope (2012): 8446, 4F-1 Marchis, F. et al. Keck AO survey of Io s global volcanic activity between 2 and 5 µm (2005): Icarus 176, 96 Matson, D. et al. Io and the early earth (1998): LPI 29, 1650 McEwen et al. (1998): High-Temperature Silicate Volcanism on Jupiter s Moon Io Science 281, 87 Miguel, Y.; Kaltenegger, L.; Fegley, B., Jr.; Schaefer, L. Compositions of Hot Super-Earth Atmospheres: exploring Kepler Candidates (2011): ApJL, 742, 2 Williams, D. et al. Volcanism on Io: New insights from global geologic mapping (2011): Icarus 214, 91

7 Tolerance limits for planned observations: maximum seeing: 2.5 minimum transparency: 20% maximum airmass: 1.6 photometric conditions: no moon: max. phase / : 0.8/30 min. / max. lag: -/- nights Instrumentation form omitted since LBTI not yet supported by the style file. / /