NOAO-NSO Newsletter Issue 82 June 2005

Science Highlights Cerro Tololo Inter-American Observatory Low-Luminosity, Compact Accretion Sources SOAR Update ...... 24 in the Galaxy...... 3 Virtual Observing ...... 25 Gemini Observations of the Two Intrinsically Other Happenings at CTIO ...... 27 Brightest Minor Planets...... 5 Th e Sun’s New Neighbors ...... 7 Kitt Peak National Observatory Magnetic Field Changes during Solar Flares ...... 8 Tohono O’odham Dispute Process of VERITAS Th e Spatial Distribution of Sodium on Mercury ...... 9 Site Selection on Kitt Peak ...... 28 Community Time Off ered on Calypso 1.2-Meter Telescope...... 29 Director’s Offi ce More Details Emerge on the NSF Senior Review...... 11 National Solar Observatory/GONG New Partnership Opportunities at NOAO...... 13 A Time of Transitions ...... 30 Q&A with Tom Matheson ...... 14 Austin Keith Pierce 1918–2005 ...... 32 ATST Project Developments...... 33 NOAO Gemini Science Center SOLIS ...... 35 Th e Gemini Rapid Response Mode...... 16 Instrumentation for Nighttime Use at the NIRI and Altair: Report from a Successful McMath-Pierce Solar Telescope ...... 36 Observing Run ...... 17 GONG ...... 38 Phoenix in Classical Mode...... 18 Following the Aspen Process: Presentations Public Aff airs & Educational Outreach and Reviews ...... 18 Astrobiology Weekend at the NGSC Instrumentation Program Update ...... 20 McMath-Pierce Solar Telescope ...... 41 2005 CTIO REU/PIA PROGRAM ...... 41 Observational Programs Th e Sky is the Limit—Student Light Pollution Surveys 2005B Proposal Process Update...... 21 in Both Hemispheres...... 43 2005B Instrument Request Statistics by Telescope ...... 21 FunFest 2005 ...... 44 2005B TAC Members ...... 23 “World Year of Physics” Celebrated at Kitt Peak...... 44 On the Cover

Th e dynamic solar chromosphere on 18 January 2005 is seen in this false color image. Daily images like this one, made with the new SOLIS vector spectromagnetograph, have been obtained with various instruments on Kitt Peak for 31 years. Shown is the strength of the He I absorption line at 1083 nanometers; dark is increasing line absorption. Unique among lines accessible from the ground, helium line strength is controlled in part by the intensity of emission from the overlying corona and also has negligible strength in the cool photosphere. Th is allows mapping of the bases of coronal features like holes, fi lament channels, and streamers. Such features are important in forecasting space weather.

Image Credit: NSO/AURA/NSF

The NOAO-NSO Newsletter is published quarterly by the National Optical Astronomy Observatory P.O. Box 26732, Tucson, AZ 85726 [email protected]

—Governor—Governor JJanetanet NNapolitanoapolitano issuedissued thisthis letterletter toto tthehe AArizonarizona HHouseouse ooff RRepresentativesepresentatives followingfollowing hherer secondsecond vetoveto thisthis yearyear ofof legislationlegislation thatthat wouldwould hhaveave oopenedpened tthehe ddooroor Douglas Isbell, Editor for further development of illuminated billboards and fl ashing signs across the state.state. TheThe defeatdefeat ofof thisthis legislationlegislation waswas aidedaided signifisignifi cantlycantly byby a coalitioncoalition ofof ArizonaAr izona Section Editors observatoryobservatory directorsdirectors andand a streamstream ofof lettersletters fromfrom observatoryobservatory staffstaff members,members, allall Science Highlights promptedprompted byby thethe tirelesstireless effortsefforts ofof MarkMark Mayer,Mayer, whowho representsrepresents thethe interestsinterests ofof a Joan Najita coalition of Tucson neighborhood associations to state and local government. Dave Bell Observational Programs Mia Hartman Observational Programs Nicole S. van der Bliek CTIO Richard Green KPNO Notable Quotes Ken Hinkle NGSC Sally Adams NGSC “It’s“It’s thethe b bestest t thinghing s sinceince t twowo p piecesieces o off s slicedliced b breadread w wereere a assembledssembled t too m make ake John Leibacher NSO Priscilla Piano NSO a sandwich.” Douglas Isbell Public Affairs & —Paul—Paul GGinsparg,insparg, professorprofessor ofof physicsphysics andand informationinformation sciencescience atat CornellCornell University,Univer sity, Educational Outreach describing the capabilities of a new customized Web alert system from the NASA AstrophysicsAstrophysics DDataata SSystemystem ccalledalled ““myADS,”myADS,” qquoteduoted iinn a HHarvard-Smithsonianarvard-Smithsonian CCenterenter for Astrophysics press release, 18 April 2005. Production Staff Stephen Hopkins Managing Editor Mark Hanna Digital Processing Pete Marenfeld Design & Layout Kathie Coil Production Support

2 June 2005 Science Highlights

Low-Luminosity, Compact Accretion Sources in the Galaxy

Josh Grindlay (Harvard Observatory and CfA)

ccretion onto compact stellar objects (white dwarfs, careful treatment of astrometry for optical identifi cations, neutron stars, and black holes) from companions in and derived source fl uxes for a range of model spectra close binaries is the primary beacon for study of the and absorption columns for both the source number-fl ux Aastrophysics of the extreme: from endpoints of stellar and distribution, logN-logS, and X-ray spectral classifi cation. binary evolution, to the physical processes in the extremes of gravity, radiation, or magnetic fi elds. Accretion from the Initial ChaMPlane results were given for logN-logS in several interstellar medium on the presumed still larger population Galactic fi elds (Grindlay et al. 2003, AN, 324, 57), as well as an of isolated compact objects should, at least for relatively early description of the Mosaic imaging identifi cation survey more massive and low-velocity stellar black holes, also be (Zhao et al. 2003, AN, 324, 176). Th e survey has now achieved observable in certain conditions, yet never has been. Given nearly its original goal of ~100 Chandra ACIS-I or ACIS-S the fundamental role that accretion plays in so many key galactic plane fi elds, with in fact 94 now selected (through problems of interest in current astrophysics, it is surprising Chandra cycle 6). Th ese have |b| ≤ 12o, exposure times that the space density and luminosity function(s) of the most ≥12 ksec (most are >20–30 ksec), and are selected to avoid common accretion-powered compact objects—white dwarfs dense clusters or bright diff use optical emission, and accreting from low-mass stellar companions, or cataclysmic (if possible) to have a minimum hydrogen column density in variables (CVs)—has not been measured to better than a order to maximize the detection and subsequent identifi cation factor of ~10 in the solar neighborhood, and they have even of faint point sources. Th ese 94 ACIS fi elds are covered by less well-known spatial distributions in the Galaxy. 59 Mosaic fi elds (36 x 36 arcmin), as shown in fi gure 1.

Motivated by these and related questions, we set out in 2000–2001 to conduct a survey of low-luminosity accretion sources in the Galaxy with the newly-launched Chandra X-ray Observatory. We proposed the Chandra Multiwavelength Plane (ChaMPlane) Survey to constrain • CV space density and X-ray luminosity functions (XLFs) in the disk vs. Bulge; • Galactic Bulge source populations; • Populations of quiescent low-mass X-ray binaries (qLMXBs) with neutron star and black hole primaries and isolated BHs; Figure 1. Distribution of 59 Mosaic fi elds to cover 94 distinct • Be-High Mass X-ray binaries (HMXBs); ChaMPlane fi elds (April 2005). Some 15 Mosaic fi elds cover • Stellar coronal XLFs in the disk vs. Bulge. the Galactic Center region, which includes some 40 Chandra

31 ACIS fi elds. Chandra would fi rst detect low-luminosity (e.g., Lx ~10 erg/s at ~8kpc) sources with suffi cient precision (≤1 arcsec) to enable their optical counterpart candidates to be selected In fi gure 2, we show a “typical” resulting color magnitude and then identifi ed with follow-up spectroscopy for fi nal diagram and color-color diagram for a 16 x 16-arcmin fi eld classifi cation and study. Optical identifi cations were corresponding to one of the 30 short (12 ksec) Chandra essential, so we also proposed a fi ve-year NOAO Survey ACIS-I exposures in the Galactic Center Survey (Wang et al. Program to do deep imaging (R~24.5) with the Mosaic I and 2002, Nature, 415, 148), which contained 46 sources. All of Mosaic II CCD cameras on the Kitt Peak and Cerro Tololo 4-m this 2o × 1o survey centered on SgrA* was covered in fi ve of our telescopes. To detect the faintest accretion source candidates deep Mosaic images. One bright Ηα object is detected out of NOAO-NSO 82 Newsletter by their (near) ubiquitous Ηα emission, as well as prioritize the ~12,000 stars with >5σ detections in R and Ηα (vs. ~23,000 spectroscopy, the Mosaic imaging is comparably deep in in R alone), although many others are below the nominal Ηα and R to derive (Ηα– R) colors; exposures in V and I threshold of (Ηα – R) < -0.3 and are primarily dMe stars. allow color-color classifi cation. However, our follow-up spectra in June 2004 with the Blanco 4-m and Hydra (see fi gure 3) showed the bright-emission Th e survey was conceived as a serendipitous source survey (R = 18.7) object to be a CV. Th e small displacement off the using primarily archival Chandra data that would be main sequence track in the color-color diagram suggests reprocessed with a uniform set of custom tools to ensure it has a small extinction (Av~1). Using the distance versus continued

June 2005 3 NOAO-NSO Newsletter 82 4 as aChandraCVand23otheropticalIDs, largelyforeground stars, outof the46Chandrasourcesinfi eld. Figure 2. ( e st ( site Web and photometric catalogs are being archived on the ChaMPlane Th deepe Mosaic images of now ~21 squaredegrees of thePlane results for one of Anticenter the fields (Zhao etal. 2005). discussion detailed of the optical/Mosaic processingsurvey a and example and 2005), al. et fi (Hong Anticenter elds these for results X-ray and processing X-ray the of Anticenterdescription a 2005), al. et Galactic (Grindlay the in fields 14 populationfrom CV constraintsthe on initial and ChaMPlane of overview the the to We 2005). have submitted papersthree al. et the Laycock see sources; for cusp SgrA* Be-HMXBs out rules which Magellan/PANIC, with SgrA* around been IR fi10-arcmin a of have fromimaging eld(JHKBrγ) results or our (e.g., preparation submitted in are Bulge, the in results as tantalizing well other as object, this on results Full of which are typical values for a CV. and luminosity L A byreddened is1.010x band keV Th 2-8 Chandra the e in ux fl colors. de-reddened its and secondary M thusand kpc, ~1.2 of distance a gives 205) 409, A Low-Luminosity, Compact Accretion Sources continued v Science Highlights model of Drimmel et al. (2003, al. et Drimmelof model m o d AstrophysicalJournal e l

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ApJ, Figure 3. Hydra spectrum of the ChaMPlane Chandra CV initially identifi ed with Mosaic. a rgos are regions as ) made possible. this having Program Survey NOAO the for grateful extremely are We catalogs. photometric and images Ηα deep these with conducted be could display.projectsandMany other analysis their for tools Web-based with together line, on submittedfor publication. Th e fi 14 rst Anticenter fi elds are Science Highlights

Gemini Observations of the Two Intrinsically Brightest Minor Planets

Chadwick Trujillo (Gemini Observatory), Michael Brown (Caltech), David Rabinowitz (Yale University) & Th omas Geballe (Gemini Observatory)

e have obtained fi rst-look observations of Orcus and Sedna (provisional Wdesignations 2004 DW and 2003 VB12) in order to place constraints on their composition. Th ese two planetary objects are unique in that they have the largest absolute magnitudes of any minor planets (this includes all asteroids, comets and Kuiper Belt objects, but not moons or planets). Orcus and Sedna were both discovered within the past two years as part of our ongoing survey of the outer solar system. Although they are brighter in an absolute sense when compared to all other minor planets, they are quite faint due to their extreme distance. Orcus is farther from the Sun than Pluto and is likely to be at least 1/3 the size of Pluto if its albedo is similar to that of other icy planets, which have albedos around 30%. Sedna is 60% farther from the Sun than any other known body bound to the solar system and is probably similar in size. Th e most interesting aspect of Sedna is its orbit: its perihelion of roughly 70 AU is 60% farther than any other solar system body.

Th e extreme distance of Sedna (reaching about 1,000 AU at aphelion) means that surface temperatures from Spectrum of Orcus. At the top of the plot, the relative refl ectance spectrum of solar heating never exceed 38 Kelvin (dropping to 11 Kelvin at apehelion). Orcus (black fi lled circles) is compared with the best-fi t water ice model (black We do not know what to expect on line) and 1-sigma limits on the best-fi t model (gray lines). For comparison, the such an extreme surface, because no spectrum of the nearby sky (gray circles) is shown at the bottom of the plot. The solar system surfaces with such peculiar middle spectrum shows the residual model of Orcus after subtracting the best-fi t orbits have been studied. However, two water ice model (hollow circles, offset vertically for clarity). The gray line on the NOAO-NSO 82 Newsletter possibilities present themselves: (1) the middle spectrum illustrates the 3-sigma methane ice model. Any greater amount of surface could be rich in volatile ices, methane is ruled out by our observations. The model shown is for 100-µm diameter which could be present based on the particles. Spectrum error bars are computed from the reproducibility of the spectral low temperature of the body as is the data in each spectral point. case for Pluto and Pluto’s moon Charon; or (2) the surface could be devoid of any ices, as bombardment by cosmic rays and solar UV should carbonize simple

continued

June 2005 5 NOAO-NSO Newsletter 82 6 irgn l hv bod absorptions and broad have monoxide, all nitrogen carbon ammonia, methanol, methane,water, as such Ices surfaces. planetary icy study to regime Th the near-IR e preferred is wavelength no other resurfacing process. is there if timescales megayear on ices woe pcrm s oiae by hand, other the dominated on Orcus, ice). is water spectrum (whose is spectrum dominated by methane ice) and Charon (whose Pluto on found out strong ice absorptions, such as those rule to enough high was ratio to-noise However, datacollected. the signal- the in featurelessappears Sedna’s spectrum to follow). composition surface (with more detailed basic studies on limits crude place enough to was Th is discovery. their of months few a within targets the of each of on-source K-band spectroscopy from hours two about collected we (NIRI), Using Imager Infrared Near North’s particular. Gemini in K-band the in Gemini Observations of Two Britghtest Minor Planets continued Science Highlights June 2005 suig oeae o ag grain large studied. to moderate combinations Assuming albedo and models grain most under ice water 70% than less by covered surface be must Sedna of the to fi that nd confi we dence spectra, 3-sigma collected the of modeling Hapke Using primarily unknown. are limited Orcus and Sedna of albedos the because are Our conclusions Orcus. and Sedna of properties surface the on limits crude some place can we hand, in already data the Using two reveal additional will objects icespecies. these of studies deeper that hope We ice. water have to shown been have several other Kuiper Belt objects (KBOs) the figure). Th is is not unexpected, since showsstrong signatures of water (see ice fraction is less than 50%. Additionally, 50%. than less is fraction surface ice water the that suggest larger and best-fi µm t 25 diameters the grain for models Orcus, For confidence. 3-sigma to ice, methane 60% than less coveredby must be Sedna of larger), surface the or µm 100 (diameters models eel bu tee w ms extreme minor planets. most two these about reveal will spectra deeper what see to anxious Weareidentifi other species. no far, ed some of so and ice, water 50% to up with typical KBOs, more is hand, other the on Orcus, radiation. UV solar and rays cosmic by processed surface a with Pluto or Charon. of Instead, it that is consistent unlike very is Sedna of surface the that clear Th is it aside, numbers ese considered. be one modelneed albedo only as constrained, signifi more cantly be will results above the measured, are Orcus and Sedna of albedos the When ice. methane 30% coveredmorebythan are Orcus smaller than 25 µm, its on surface cannot be diameters grain unless n ie at ph/0504280 line on the in Th is workwill be publishedthis summer srpyia Journal Astrophysical ). xxx.lanl.gov/abs/astro- (available (a va i l a b l e Science Highlights

The Sun’s New Neighbors

Todd Henry (Georgia State University)

he Cerro Tololo Inter-American Observatory Parallax Earth. A trigonometric parallax series is typically considered Investigation (CTIOPI) began in August 1999 under fi nished when we have acquired at least 40 frames over a the auspices of the NOAO Survey Program as a two-year period, yielding parallax errors of ~2 mas. Tsignifi cant research track of the Research Consortium on Nearby Stars (RECONS). Since February 2003, CTIOPI has From the 0.9-m program, we have determined 217 parallaxes been continued as part of the Small and Moderate Aperture to date—20 are for new systems in the RECONS 10-pc Research Telescope System (SMARTS) Consortium. CTIOPI sample, and an additional half dozen have been placed fi rmly is an international collaboration with the primary goal of within 10 pc for the fi rst time (previous parallaxes had large revealing unrecognized neighbors of the Sun. Particular errors). We have also found 110 more systems between 10 and emphasis is placed on red dwarfs within 10 pc (the horizon 25 pc. For comparison, only 195 trigonometric parallaxes of the RECONS sample) and white dwarfs within 25 pc. Th e from ground-based eff orts have been published since the latter distance is the horizon of the Nearby Stars Project defi nitive Yale Parallax Catalog (van Altena et al. 1995). (NStars) and Catalog of Nearby Stars (CNS) programs, Perhaps most importantly, the new 10 pc members constitute which are US and German eff orts to provide compendia of a 10% increase in the RECONS sample, illustrating that we stars within 25 pc. have many neighbors with whom we are not familiar. In the table, we present a few of the more intriguing distance Th ree groups in the United States (Todd Henry, Wei-Chun determinations. Th is list is not exhaustive, and these results Jao, and John Subasavage at Georgia State University; should be considered preliminary. Defi nitive results are Phil Ianna and Jennifer Bartlett at the University of Virginia; forthcoming in the Astronomical Journal asas partpart ofof thethe and Dave Koerner at Northern Arizona University) and one RECONS series of papers entitled “Th e Solar Neighborhood.’’ in Chile (Edgardo Costa and Rene Mendez at Universidad de What becomes clearer with each round of parallax reductions Chile) work together to discover and characterize the true is that the Universe is dominated by the Sun’s small red dwarf stellar population of the Sun’s environment. Th e only other cousins, which account for more than 70% of all stars. substantial parallax program currently underway is that of the US Naval Observatory in Flagstaff , AZ. During complementary photometric programs on the 0.9-m, we have also amassed VRI photometry for more than CTIOPI was carried out on the CTIO 0.9-m and 1.5-m 400 systems. Spectral typing work carried out on the CTIO telescopes through time granted by NOAO, and the program 1.5-m during SMARTS time has also allowed us to determine continued on the 0.9-m as part of SMARTS. Th e fi rst results defi nitive spectral types for more than 500 systems. Th is from both programs have recently been published (Jao et al. allows us to evaluate the true natures of the stars we place on 2005, AJ, 129, 1954, for the 0.9-m program) or are in press the CTIOPI observing list for intense observations. When (Costa et al 2005, AJ, July issue, for the 1.5-m program). combined, these astrometric, photometric, and spectroscopic We observe promising nearby star candidates that have eff orts provide a complete portrait of our stellar neighbors. some combination of high proper motions, photometric, or Th ey also provide an ideal research environment in which spectroscopic information indicating a small distance from young astronomers can learn many tools of the trade.

CTIOPI Distances for New Nearby Stars Name Distance SpType SO 0253+1652 3.82 +/- 0.06 pc M7.0V SCR 1845-6357 3.94 +/- 0.04 pc M8.5V NOAO-NSO 82 Newsletter DEN 1048-3956 4.04 +/- 0.03 pc M8.5V LHS 1723 5.43 +/- 0.06 pc M4.5V LHS 2090 6.29 +/- 0.18 pc M4.5V GJ 1128 6.53 +/- 0.11 pc M4.5V LHS 337 6.58 +/- 0.16 pc M4.0V GJ 1068 6.97 +/- 0.10 pc M4.5V SCR 1138-7721 7.96 +/- 0.52 pc M5.5V LHS 145 9.80 +/- 0.16 pc white dwarf

June 2005 7 NOAO-NSO Newsletter 82 8 required to power solar flares, together with their association stressed magnetic field configurations. Estimates of solar atmosphere the above strong, energy complicated, and presumably S which show the line-of-sight component of the vector fivector the eld of component line-of-sight the show which magnetograms, The GONG events. of number large a for flsolar fiduring aresmagnetic changes of eld characteristics single a telescopes have GONG aff for of network orded us a global unique opportunity results to the assess the from Magnetograms presented event. have publications Most transverse magnetic field during solar fl ares. andlongitudinal the both in changespermanent andabrupt cadence observations have provided unequivocal evidence of fiyears,however,six past In the lines. eld high-quality, high- magnetic along plasma the ofheating the by changescaused effprofiinstrumental line an of result be the toproved ect, le confused. Transient situation the magnetic fi leaving literature,eld changes the were in oftappeared en reported, but these an intervalof 50G.Thehorizontal axisspans240minutes, andtickmarks appearat anintervalof 30minutes. offlend the and peak, flX-ray GOES to according are marksat tick appear and G, 300 spans axis vertical measurements.The ux of time for one of the representative points. The black line represents the fi t to the data. denote the positions of The the representative three points used in vertical our analysis.lines (d) A denote plot ofthe the start, longitudinal magnetic fi eld as a function image each in boxes white fifiand magnetic the black in The decrease a increase.indicates an Black indicates white eld. eld, same the of magnetogram GONG remapped A active region. (b) Black indicates negative fi coordinates. heliographic eld; white in indicates positive fipixel per 0.125° eld. (c) is A map of the fiscale image The t parameter for the square.change in the offlimage the light” “white GONG remapped A (a) 1. Figure pixels128 is image The 2003. November 2 on region active aring the through 1950s 1990s, positive and the negative reports of magnetic Fromfi eld changes fl ensued. ares solar during fi changes magnetic eld for search the and photosphere the fimagnetic the map to possible became it in 1950s eld the In flares must electromagnetic be inorigin. thatconclusion fi the magnetic complicatedto with led elds, Science Highlights explosions, the largest in the solar system, occur in the the in occur system, solar the largestin explosions, the for mystery these that astrophysicalshown have Observations years. 150 almost an been have flares olar June 2005 Magnetic Field Changes during Solar Flares Jeff (NSO) Harvey &Jack Sudol can be modeled with a simple step function. A model of the the of model A function. step simple a with modeled be can fiand abruptmagnetic quite the are changesthat showedeld prototype,GONG+ the with includingNovember 2000 in observations work, Previous fi 1). (see gure rotation solar for image was remapped to an overhead with compensation view Each the are. of fl peak aft the and before er hour one least availableatwereforsite GONG single a frommagnetograms solar continuous which during for selected changes fl were fi X-class flares 15 eld ares, magnetic the characterize To of resolution aspatial 5 arcsec and an instrumental noise of about 3G. have one-minute e magnetograms Th a at available cadence. are disk, solar entire the across of the cases, the magnetic field change occurred on a time scale range from 30 G (the detection limit) to almost 300 G. In 70% region during all 15 flares. Th e magnitudesfl the in oflocation one theleast at active in aring occurred changes fi eld changes signififiabrupt, permanent that and found cant,Wehave eld for study.selected further was fi occurred, the eld in change strongest the most and the abrupt where point the point, representative a site, each Forfisignifi magnetic a occurred. the had in changeeld cant Based on these parameter maps, 42 sites were identifi ed where the characteristics of the field changes across show the active toregion. constructed fiwere the parameters of t Maps pixel. fi the fifiin change wasthe abrupt ofeld,an each andto eld t magnetic field as a function of time, allowing for the evolution continued Science Highlights

Magnetic Field Changes during Solar Flares continued of less than ten minutes. In about two-thirds of the cases, If our favorite scenario is correct, work is associated with the the longitudinal magnetic fi eld decreased, in the remaining tilting of the fi eld, and this work must be included in the energy cases, the fi eld increased. Most fi eld changes occurred in budget of any theory. Because the fi eld changes always occur the penumbrae of sunspots. In six cases, the change in the aft er the fl are start, it is likely that the observed fi eld changes magnetic fi eld appears to have propagated across the active are just one of the numerous post-fl are phenomena and not region. Th e rates of propagation range from 5 to 30 km s-1. the event that triggers fl ares. Still, the observed fi eld changes may help sort out the basic physics of the fl are phenomenon. Because the full fi eld vector is not observed, the interpretation Th is work contradicts current theories that posit that the of these results is ambiguous. Among several possible photospheric magnetic fi eld does not change during a fl are. scenarios, we favor one in which the observed change in Extensions to our work will cover more events by relaxing our the longitudinal fi eld is a result of the vector fi eld becoming selection criteria and including weaker events. more vertical as an immediate consequence of the fl are.

The Spatial Distribution of Sodium on Mercury

Drew Potter (NSO) & Rosemary Killen (University of Maryland)

e are mapping the sodium emission from total sodium intensity from one hemisphere to the other. We planet Mercury using the McMath-Pierce Solar calculated north-south and east-west ratios, using the brightest Telescope, a 10-arcsec-square image slicer, and pixel in the surface refl ection image as the center of the image. Wthe stellar spectrograph. We obtain sodium images that are Th e north-south ratios are plotted against true anomaly angle 10 arcsec square with 1-arcsec pixels. Since 1997, we have in fi gure 2. accumulated approximately a thousand of these images, covering a nearly complete range of true anomaly angles. Th e reason for collecting so many images is that the sodium distribution over the planetary surface is variable, sometimes from one day to the next. We expect that analysis of these variations will lead to a better understanding of the processes that govern the interaction of the space environment with planetary surfaces.

Figure 1 shows four sodium images that represent the most common kinds of sodium distribution. Figure 1a (upper left ) shows limb brightening, resulting from an approximately uniform distribution of sodium vapor in the Mercury atmosphere. Th e long path length through sodium vapor above the planetary limb yields an image with bright sodium emission along the limb. Figure 1b (upper right) shows dawn-side enhancement of sodium. For this case, we are viewing the dawn terminator. As the sun rises, sodium that has condensed on the cold dark side of the planet is warmed, and evaporates into the atmosphere, leading to NOAO-NSO 82 Newsletter excess sodium on the dawn side. An additional dawn-side eff ect is the precipitation of sodium photo-ions to the surface, Figure 1. Sample distributions of sodium on the which some theoretical models predict should occur mostly surface of Mercury. Figure 1a is a limb-brightened in the dawn hemisphere (Killen et al. 2004, Icarus, 171, 1). image, as expected for a uniform distribution Figures 1c and 1d show another sodium distribution eff ect, in of sodium. Figure 1b shows sodium emission which we see excess sodium in either the northern hemisphere extending to the dawn terminator, and fi gure 1c (fi gure 1c) or the southern hemisphere (fi gure 1d). and 1d show northern and southern hemisphere excess sodium, respectively. Th e simplest quantity that we can use to characterize the distribution patterns illustrated in fi gure 1 is the ratio of the continued

June 2005 9 NOAO-NSO Newsletter 82 10 the solar wind on the surface. Sarantos surface. the on wind solar the of impact direct by rocks surface from sodium of sputtering is the result of hemispheres or in southern seen the northern sodium excess the We that two. about of suggest factor a by excess northern over predominating excess southern with south, or in north the in either sodium excess show ratios brightening the limb of third a However,about unity. near are ratios the of for most seen as fi gure 1a, the ratio should be unity, or close to very it. In such fact, symmetric distributions, perfectly For lines. dashed the by represented 10%, about of deviation standard a with day, one on taken data Each point the represents average of ten or more images Spatial of Distribution Sodium on Mercury continued side images is shown infigure 3. dawn-foranomalyangle againsttrue ratioseast-west of plot features. Th e interesting some showed Th ratios east-west e spatial resolution was images are to resolve needed question. this emission where longitudes other.hemisphereone the consistentlyBetter or in excess in clear-cut no were there wereinconclusive—for this Results location.atthat sodium south or north excess of clump a see would we formations, geological with emission sodium of correlation some were there if that expectation the in image, the in point brightest We also plotted the north-south ratio against longitude of the by shown (2003, Shemansky as are agents, wind solar effi sputtering the in cient ions extraordinarily stripped heavy that fact important the Equally is (IMF). Field Magnetic Interplanetary the of values on depend locations hemispheric and number their and latitudes, high at surface Mercury’s with connect Sci Space iue . h vrain f ot-ot rto f sodium of ratio north-south emission withtrueanomalyangle. of variation The 2. Figure Science Highlights ., 49, 1629) have shown that open fi eld lines can can fi lines open eld that shown have 1629) 49, ., June 2005 AIP Conf. Proc., Proc., Conf. AIP 63, 687). 687). 63, et al. et

(2001, (2001, Planet. Planet. rp blw nt, ugsig ht h dw enhancement eff dawn has disappeared. ect We of that the speculatesodium locus the that suggesting unity, below drops quickly ratio the angles, However,larger at 120°. near 1.6 as into sunlight, the sodium ratio increases as condensed expected, rising movingto values as is high that velocity terminator As the true anomaly angle increases, accompanied by increasing photo-ion of result precipitation on dawn the hemisphere. the is this Perhaps unity. than greater slightly actually are ratios observed the but angles, anomaly true zero nearfi unityto than expect less mightratio we a nd Consequently, days. few a for direction reverses fact in and slowly, very moving is terminator the because evaporation, zero, near angles sodium anomalyfrom enhancement dawn no or little be true should there at However, unity. than we expect that the ratio of east to west to be equal to or greater sky, the in seen that so thereif is stronga dawn enhancement, as planet the of side east the Th on the is Sun.terminator the of en east seen is Mercury whenever view in is terminator dawn the that such Th is observations Mercury of egeometry h eitne f h dw ehneet bevd by observed enhancement dawn the Sprague et of al. (1997, existence the support also data Our wind Mercury. on signifi solar process a cant the is by rocks surface of the sputtering support that data concept distribution sodium our that believe We to other. the hemispherefavored one from switch a in resulting recycling, ion controlfi that electric eld the in changes be might there that is speculation effAnother this explain mightect. which Sun,temperature increasing the fromdistancewith decreases Mercury’s surface as limb the towardmove may evaporation anomaly angle presents some as-yet unexplained features. anomaly angle. Figure 3. The variation of dawn-side east-west ratio with true Icarus , 129, 506), but its variation with true DIRECTOR’SOFFICE NATIONAL OPTICAL ASTRONOMY OBSERVATORY

More Details Emerge on the NSF Senior Review

Jeremy Mould

s I outlined in the March 2005 NOAO-NSO Newsletter, the In order to treat NRAO, NOAO, NSO, Gemini, and NAIC on an equal NSF Division of Astronomical Sciences (AST) is beginning footing and to obtain an in-depth understanding of the contributions the process of a “Senior Review” of its facilities portfolio. that each of our facilities makes, component by component, NSF is ThA is review, a recommendation of the most recent Decadal adopting a “zero-base” approach. Under this approach, NOAO and Survey, is motivated at this particular time by a combination of the our sibling observatories will consider and document: current Federal budget outlook, the ambitions of the astronomical • Th e case for, and priority of, each component of NOAO community as evidenced in the Decadal Survey and in other reports NSO (KPNO, CTIO, NSO, SacPeak, GONG, etc.), along such as “Connecting Quarks with the Cosmos,” and by the growth in with a defensible cost for each. the AST budget over the past fi ve years. • Th e case for a forward-looking observatory operation, the highest priority components of which would exist Th is review is designed to examine the balance of our investments in 2011. in the various facilities that we support. Th e primary goal of the • As realistic an estimate as possible of the cost and review, and the adjustment of balance that will result, is to enable timescale that would be associated with divestiture of progress on the recommendations of the Decadal Survey, including each component. such things as operations funds for the Atacama Large Millimeter Array (ALMA), and other priorities. NSF expects that our deliberations will: • Be based on extensive consultation with the user NSF has adopted the following boundary conditions for the review: community. • An assumption that the AST budget will grow no • Involve evaluation of component facilities and capabilities faster than infl ationary increases for the remainder of using well-defi ned and carefully documented metrics to the decade. defi ne productivity, cost eff ectiveness, and future utility. • In concert with the advice of every community advisory • Take into consideration systemic issues such as body (and in keeping with its own evaluation of complementing observations at other wavelengths, balance and need), NSF will not use resources from the fi lling critical niches in the overall US system, roles unrestricted grants programs to address the challenges of in training and technical innovation, and impact on facility operations or the design and development costs shared infrastructure. for new facilities of the scale of the Large Synoptic Survey • Explore opportunities to deliver scientifi c knowledge Telescope (LSST), the Giant Segmented Mirror Telescope at reduced cost or increased effi ciency through new (GSMT), the Square Kilometer Array (SKA), etc. operating modes. • No facilities will be considered to be “off the table.” • Th e process and the adjustments in balance that may result NSF seeks to have our input by July 31. With this information in must be realistic and realizable. hand from all of the facilities, and with the best understanding of the • Recommendations should be based on well-understood needs for development and future programs, AST will then present criteria. a number of scenarios to the senior review committee for their • Th ere should be ample opportunity for community input comment and advice. Th ese scenarios will necessarily trade progress at all stages. on the various recommendations against preservation of existing capability. Th e challenge will be to strike an acceptable balance. Th e specifi c goal of the review is to examine the impact and the gains from redistributing $30 million of annual spending from AST In the words of NSF AST Director Wayne Van Citters, “We recognize funds. Th ese funds would be obtained by selective reductions in the that this will be a diffi cult task and that the end result may well operations of existing facilities. Th e review will not revisit existing be that some facilities are judged to be no longer viable under community priorities and recommendations for how these funds the circumstances. We also recognize that the landscape of US would be used. Th e near-term needs for new investment has lead NSF astronomy could almost certainly change dramatically as a to seek to generate the $30 million in annual redistributed funding result of some these actions. Th e question for all of us is to by the end of FY 2011. Even with this, there will be challenges to be judge whether these changes are viable and lead to a vital and met to satisfy projected need in FY 2007–2008. NSF’s target is to sustainable future, or whether the pace and scope of change have the advice of the committee in hand by September of this year. continued

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