The Ohio State University Astronomy Department Columbus, Ohio 43210
Abstract Zheng Zheng. Justin Oelgoetz is an OSU Chemical This annual report covers the period 2002 September Physics graduate student working on his Ph.D. thesis through 2003 August. with Pradhan. The Masters Degree was awarded to Fields, Mar- 1 PERSONNEL shall, and Onken. During the period covered by this report, the regu- Osmer represents OSU on the Board of Directors lar academic staff of the Department of Astronomy in- of the Large Binocular Telescope Corporation. He is cluded Richard Boyd, Darren DePoy, Jay Frogel, An- a member of the Publications Board of the American drew Gould, Eric Herbst, Smita Mathur, Jordi Miralda- Astronomical Society and also serves on the Board of Escud´e, Gerald Newsom, Patrick Osmer (chairperson), Directors of Research Corporation. Bradley Peterson, Marc Pinsonneault, Richard Pogge, Peterson completed a term as a member of the NASA Anil Pradhan, Barbara Ryden, Robert Scherrer, Kris- Structure and Evolution of the Universe Subcommittee. ten Sellgren, Gary Steigman, Donald Terndrup, Terrance He continues to serve as a member of the Astronomy Walker, and David Weinberg. In addition, Christopher and Astrophysics Advisory Committee (AAAC), which Kochanek has been appointed Ohio Eminent Scholar in was established by Congress to facilitate greater coop- the Department of Astronomy, starting October 1, 2003. eration between the National Science Foundation and Boyd was on leave, serving in the Physics Division of NASA. Peterson is OSU’s institutional representative to the National Science Foundation in Washington, D.C. the AURA Board and this year he was elected to the as Program Director for Nuclear Physics and for Par- Space Telescope Institute Council (STIC). ticle and Nuclear Astrophysics. Frogel was on leave at Sellgren began service on the SOFIA Science Coun- NASA Headquarters in Washington, D.C. cil, and served on the Scientific Organizing Committees Michele Kaufman and Sultana Nahar held appoint- for Galactic Center 2002 (Kona, HI, November 2002) and ments as Research Scientist, and David Ennis and Eric Astrophysics of Dust (Estes Park, CO, May 2003). She Monier were Lecturers. Emeritus members of the is also a member of the search committee for the Deputy Astronomy Department are Eugene Capriotti, George Director for the U.S. National Gemini Science Council. Collins II, Stanley Czyzak, Geoffrey Keller, William Pro- 2 TELESCOPES AND INSTRUMENTATION theroe, and Robert Wing. The staff of the Imaging Sciences Laboratory (ISL) OSU has a one-quarter share of the observing time included Bruce Atwood, Ralph Belville, David Brewer, on the 2.4-m and 1.3-m telescopes of MDM Observatory Paul Byard, Mark Derwent, Jerry Mason, Thomas O’- on Kitt Peak. The other MDM partners are Dartmouth Brien, Daniel Pappalardo, David Steinbrecher, and Ed- University, Columbia University, and the University of ward Teiga. Michael Savage was manager of the Astron- Michigan. OSU is also a partner in the Large Binocu- omy Department computer resources. lar Telescope (LBT), which is under construction at the In Tucson, AZ, Mark Wagner held the position of Mt. Graham International Observatory in Arizona, and Research Scientist, while Ray Bertram was Research As- will have one-sixth of its observing time. Other part- sociate. Wagner and Bertram are assigned to work full- ners in the LBT project are the University of Arizona, time on the Large Binocular Telescope (LBT) project. astronomical consortia in Italy and Germany, and the Wagner is Instrumentation Scientist for the LBT, coor- Research Corporation. dinating the instrumentation efforts of the LBT partners The LBT, with twin 8.4-m mirrors, will be the and developing instrument support on the mountain. world’s largest telescope on a single mount and will have Postdoctoral researchers in Astronomy during part a 22.8-m baseline for inteferometric observations. Dur- or all of this period were David Graff, Dirk Grupe, Eric ing the last year, the polishing of the first primary mirror Monier, and Marianne Vestergaard (Columbus Fellow). was completed at the Steward Observatory Mirror Lab- Graduate students in the Astronomy Department oratory, and the mirror is being integrated into its cell. during the academic year included Deokkun An, Niko- Figuring work on the back side of the second primary has lay Andronov, Misty Bentz, Christopher Burke, Julio begun. The telescope enclosure is complete, and work is Chanam´e, Guo-Xin Chen, Franck Delahaye, Dale Fields, well along on assembling the telescope structure. Fab- Stephan Frank, Angela Hanson, Susan Kassin, Juna rication of the first adaptive secondary is being done in Kollmeier, Jennifer Marshall, Christopher Morgan, Grant both Arizona and Italy. The prime focus camera is be- Newsham, Christopher Onken, Josh Pepper, James Piza- ing completed in Italy. First light with the prime focus gno, Adam Steed, Jeremy Tinker, Rik Williams, and camera and the first primary is planned for the summer of 2004.
1 OSU is providing the aluminizing system as part of obtain metallicity estimates. These estimates are used its in-kind contribution to the LBT. During the year the to select ideal clusters for planet searches, as well as dummy mirror cell and vacuum bell jar were unpacked adding more accurate metallicity measurements to the and set up in rented hangar space at Rickenbacker air- literature. port near Columbus. The mechanical pumps were rein- Gould, Pepper, and DePoy have considered the sen- stalled and the O-ring assembly was cleaned. Tests show sitivity of transit searches to habitable-zone planets. that the pumps and vacuum seal are performing well. Photon-limited transit surveys in the V band are in prin- The cryogenic panels for producing high vacuum were ciple about 20 times more sensitive to planets of fixed fabricated and installed, and first tests show that the size in the habitable zone around M stars than G stars. overall system achieves the required vacuum level. The In the I band the ratio is about 400. The advantages design of the boron nitride crucibles was completed and a of a closer habitable zone and smaller stars (together prototype unit was built and tested; then the remaining with the numerical superiority of M stars) more than crucible assemblies were fabricated. The design of the compensate for the reduced signal because of the lower electrical power distribution system was completed and luminosity of the later-type stars. That is, M stars can its fabrication and installation are nearing completion. yield reliable transit detections at much fainter appar- A first test of the system with four crucibles has been ent magnitudes than G stars. However, to achieve this carried out. The remaining crucibles are to be installed greater sensitivity, the later-type stars must be moni- and tested during autumn, 2003. tored to these correspondingly fainter magnitudes, which The instrumentation group continued to work on can engender several practical problems. They show that the Multi-Object Double Spectrograph (MODS) for the with modest modifications, the Kepler mission could ex- LBT. Key milestones met in the past year were procur- tend its effective sensitivity from its current MV =6to ing the first large optics and ordering the large structural 9. This would not capture the whole M dwarf peak but framework for the instrument. There was also substan- would roughly triple its sensitivity to Earth-like planets tial work on the various mechanisms, control software, in the habitable zone. To take advantage of the huge and a system to compensate for any flexure and other bump in the sensitivity function at MV = 12 would re- image motions for the instrument. quire major changes in Kepler. However, the reduced The instrumentation group also worked on general photometric-precision requirements at MV = 12 makes maintenance and repair of existing instruments at MDM a search for these transits possible from the ground. Pho- Observatory and CTIO. In particular, ANDICAM (a tometric stability requirements are much less severe for camera capable of simultaneous imaging at optical and M stars than G stars. To detect Earth-mass planets in near-infrared wavelengths) was moved to the CTIO (ex- the habitable zone around G stars, the variability on 2MASS) 1.3-m telescope and returned to nightly opera- transit timescales must be less than 2 × 10−5, but for tions as part of the SMARTS consortium. Work also con- middle M stars the limit is 1.2 × 10−3. tinued on upgrading the detector array in the MDM facil- Pepper, Gould, and Depoy have proposed an all-sky ity near-infrared camera and spectrograph (TIFKAM). survey to find planetary transits. Transits of bright stars DePoy, Gould, and Pepper are building the 2-in (5- offer a unique opportunity to study detailed properties cm) Kilo-square-degree Extremely Little Telescope of extrasolar planets that cannot be determined through (KELT), which will carry out a 2π steradian search for radial-velocity observations. They propose a new tech- planetary transits to V = 10. nique to find such systems using all-sky small-aperture Marshall has been developing the Image Motion transit surveys. They derive a general formula for the Compensation System (IMCS) for MODS, and has pro- number of stars that can be probed for such systems as duced results within specifications for flexure compensa- a function of the characteristics of the star, the planet, tion in the lab prototype of the IMCS. and the survey. They use this formula to derive the op- Marshall and Kollmeier, with DePoy, have been con- timal telescope design for finding transits of bright stars: tinuing work on two filter wheels that will be going to a1 to 2 (2.5-cm to 5-cm) “telescope” with a 4k × 4k the MDM and YALO observatories. The first of these is camera. scheduled for commissioning at MDM in December 2003. 4 MICROLENSING 3 EXOPLANETS Gould is currently focusing his work on applications DePoy, Gould, Pogge, and Yoo are working in the of microlensing and Galactic structure. Microlensing µFUN collaboration to search for extra-solar planets by work includes detection of planets, microlensing obser- intensive follow-up observations of ongoing microlensing vations toward M31, developing new methods to ex- events. µFUN has substantial observing time on the tract additional information about individual microlens- SMARTS 1.3-m, the Wise 1-m, and the Hawaii 0.6-m ing events, investigation of the relation between star telescopes. counts and microlensing, and measurement of the masses Marshall has worked with Burke, DePoy, and Gaudi of nearby stars using astrometric microlensing. Gould is on STEPSS: the Survey for Transiting Extrasolar Plan- PI on a SIM Microlensing Key Project whose primary ets in Stellar Systems. Marshall has obtained spectro- aim is to measure the mass function of both dark and lu- scopic data on several open clusters, from which they minous objects in the Galactic Bulge. Galactic structure
2 work is primarily focused on completing a Revised NLTT interactions. Catalog with better astrometry and new optical/infrared Delahaye and Pinsonneault are expanding the treat- photometry, and using the reduced proper motions from ment of microscopic diffusion processes (radiative accel- this catalog to isolate various stellar populations for fur- eration, detailed gravitational settling) in the stellar evo- ther study. lution code. In particular, they are comparing results Terndrup has contributed to several ongoing studies derived from OPAL data with recent Opacity Project of galactic microlensing and of gamma-ray burst after- work on radiative acceleration rates. The resolution of glows, using data obtained at MDM. the monochromatic opacities is proving to have a sig- nificant impact on the radiative acceleration rates. The 5STARS main focus of this work will be the effect of radiative Fields, Gould, J. An (Cambridge), the PLANET levitation on horizontal branch stars and the interaction Collaboration, J.-F. Glicenstein (DAPNIA-SPP) of the between mixing and diffusion processes. EROS collaboration, and P. Hauschildt (Hamburg), com- Chanam´e, Pinsonneault, and Terndrup are inves- pared the limb darkening, measured for the K3 III source tigating giant branch models with rotational mixing. star for the microlensing event EROS BLG–2000–5, with Models compatible with the survival of angular momen- predictions from atmospheric models. These are the first tum in horizontal branch stars are found to have mixing limb-darkening data to be taken of this type of giant (gi- on the RGB consistent with the data. They are explor- ants approximately 10 times its physical size have been ing the inhibiting effects of µ gradients on mixing and resolved by near-infrared interferometry). In addition, angular momentum transport, as well as self-consistent the quality of their data makes this limb-darkening mea- models including both mixing and angular momentum surement the second best ever (next to the sun). transport. Marshall, together with DePoy, Gould, Pinsonneault, Pinsonneault, with J. Bahcall (IAS), is working on and Terndrup, is undertaking a survey of metal-poor a revision of the solar neutrino fluxes and helioseismic subdwarfs. They are obtaining photometry and mod- properties of the standard solar model. Recent proposed erate resolution spectroscopy for a sample of 1000 stars reductions in the solar CNO abundances may be creating in the solar neighborhood. ¿From these data they plan a conflict between the predicted and observed depth of to obtain accurate colors and metallicity estimates for the solar surface convection zone. these halo stars. Once an astrometric mission (such as Andronov and Pinsonneault have continued to inves- FAME or SIM) obtains parallaxes of these stars, they tigate the evolution of interacting binaries. They have will be able to calibrate theoretical Galactic globular found that evolved secondary stars in CVs are required cluster CMDs to obtain much more accurate distance es- to understand the observed mass–period relationship in timates to globular clusters in the Galaxy than currently CVs. In addition, they found that tidally-induced mix- exist. These data will also allow them to study stellar ing may occur on a short enough timescale to induce populations in the Galaxy and Galactic abundance pat- changes in the mass–radius relationship for evolved sec- terns. ondary stars in CVs; this may explain the CV period Marshall is working with DePoy and Gould on com- gap. piling a similar database of photometric and spectro- Andronov and Pinsonneault are currently studying scopic data on a sample of 50 extreme subdwarfs. This the impact of spots covering a large fraction of the stel- unique population of halo stars defines the metal-poor lar surface on the structure and evolution of low mass lower main sequence. From the colors they obtain for stars. Potential features that could be impacted would these objects, they will better define the red end of the be the radii of short-period eclipsing binaries, pre-main main sequence. Spectroscopic observations will yield sequence light element depletion, and the mass–radius metallicity estimates as well as 3-D space velocities for relationship for interacting binary stars. these objects. This work will triple the currently known Zheng and Gould, with S. Salim (UCLA), C. Flynn number of such stars. (Tuorla Obs., Finland), and J. Bahcall (IAS), derived Newsham and Pinsonneault are investigating the the I−band luminosity function of Galactic disk dwarfs role of hydrodynamic and magnetohydrodynamic mech- using HST star counts. anisms for angular momentum transport (and the asso- ciated chemical mixing) in low-mass stars. The obser- 6STARCLUSTERS vations to be reconciled with theory include helioseis- Burke, Pinsonneault, and A. Sills (McMaster U.) mological data on the solar internal rotation rate, the have completed their thorough investigation of the input solar abundances of light elements such as 7Li and 9Be, physics uncertainties for determining the ages of open the observed spin-down of open cluster stars of known clusters using the lithium depletion boundary (LDB) ages, and their surface elemental abundances. The im- technique. Ages for 20–200 Myr open clusters using the pact of pre-main sequence accretion disks upon the sub- traditional main-sequence fitting technique are uncertain sequent rotational evolution of stars is also under inves- by a factor of nearly 2. The main uncertainty in main- tigation and conversely what the observed angular mo- sequence fitting arises from the amount of convective mentum distributions of open cluster stars have to tell core overshoot in the theoretical models. Stellar mod- us about the processes of star formation and star-disk els that include convective core overshoot have a longer
3 main-sequence lifetime and result in older open cluster these are the latest spectral types found to date for SMC ages. The LDB age technique is an independent method supergiants. The relation between CN strength and the to determine the ages of open clusters and can be used near-infrared absolute magnitude M(104) differs signif- to determine how much, if any, convective core overshoot icantly between the SMC, the LMC, and the Galaxy, is required for main-sequence fitting ages. Ages for open indicating the extent to which the CN strength depends clusters determined with the LDB age technique are con- upon the metallicity. This result makes it possible to sistent with including modest amounts of convective core express the CN–luminosity calibration as a function of overshoot in the theoretical models. However, the sig- metallicity, thereby enhancing the usefulness of red su- nificance of the age difference has not previously been pergiants as distance indicators for nearby galaxies of quantified. This study shows that based on theoretical known metallicity. errors alone, absolute open cluster ages with the LDB Wing and Walker have observed a number of well- age technique are possible to 3 – 8% precision. The ob- studied open clusters and Landolt standard fields with servational uncertainties of locating the LDB and bolo- a set of narrow-band filters in order to establish stan- metric corrections (10% and 7%, respectively) are cur- dard stars for CCD observations on their six–color, near- rently larger than the theoretical errors. Ages of open infrared photometric system. Work is underway to de- clusters obtained without convective core overshoot are rive the transformations between this system and the ruled out with high confidence. similar eight–color system previously used for photoelec- Andronov and Pinsonneault have examined blue tric work. stragglers from binary mergers. The observed blue strag- gler population in old open clusters can be explained 7 STELLAR POPULATIONS with the angular momentum loss rate inferred from With R. Peterson (Astrophysical Advances), E. Sad- young open cluster stars if the mass function of sec- ler (U. of Sydney) and A. Walker (NOAO/CTIO), Tern- ondary stars in close binaries relative to primary stars drup, An, and Hansen continue work on their survey is flat. Another production mechanism related to rota- for extreme horizontal branch (EHB) stars in the Bulge. tional mixing is likely necessary to explain blue stragglers They show that the Bulge contains the same sorts of faint in young open clusters. (MV ≥ 4.5) blue objects on color-magnitude diagrams Pinsonneault, with L. Hobbs (U. Chicago), Schuler, that are confirmed EHB stars in many galactic globular and King (Clemson U.), is involved in a spectroscopic clusters. Terndrup and Peterson are now writing up the study of oxygen abundances in dwarf stars of the Pleiades results of their imaging and spectroscopic survey. and M34. Large differences between oxygen abundances Terndrup is also finishing a study on carbon isotopic derived from the O i triplet and from the forbidden [O i] abundances in the Bulge, a continuation of an earlier line were found. If the forbidden line is treated as a study by Smith, Terndrup, and Suntzeff on ω Centauri. more reliable indicator, the Pleiades has a moderately They find that luminous, metal-poor Bulge stars show high [O/Fe] ratio of +0.14. signs of deep mixing, as indicated by an abundance ra- Terndrup and Pinsonneault are continuing their stud- tio 12C/13C ≈ 4, but that mixing is greatly reduced in ies of the angular momentum evolution of stars in young metal-rich Bulge giants. and intermediate age open clusters. K. Stassun (Vander- bilt U.) and Terndrup organized a conference reviewing 8 INTERSTELLAR MEDIUM angular momentum evolution at the Albuquerque AAS Herbst has calculated intensity factors to allow re- meeting. cent observations of rotational spectral lines of deuter- Terndrup and Pinsonneault, with J. Stauffer (IPAC/ ated methanols in the protostellar source IRAS 16293 Caltech), R. Hanson (UCO/Lick), and An, have begun a –2422 to be converted into column densities. The ra- new study designed to obtain precise distances, redden- tio of deuterated methanols to normal methanol is quite ing estimates, and photometric metallicities for several high, and indicates an active grain surface chemistry. nearby open clusters. One new aspect of this work is that Herbst’s program of research into the modeling of the distances and age estimates from the lower main se- the gas-phase and grain–surface chemistry of interstel- quence may be affected by the presence of rapid rotators lar clouds continues, with an emphasis on star forma- that have blue colors that leave them markedly below tion regions. With postdoctoral associate H. Roberts the main sequence, as shown previously by Stauffer. (OSU Physics), Herbst has shown that standard mod- Wing and OSU undergraduate student K. Walker, in els of deuterium fractionation underestimate the effect collaboration with D. J. MacConnell (CSC/STScI) and at high densities, such as pertain at the center of pre- E. Costa (U. de Chile), have compared a set of 36 red su- stellar cores. Here, the depletion of heavy molecules such pergiants in the Small Magellanic Cloud to similar stars as CO onto grains leads to a much stronger fractionation, + in NGC 2100 of the LMC and the Double Cluster h & which is confirmed by observations of the ion H2D in χ Per of the Galaxy. The stars were observed on a six– the pre-stellar core L1544. color system of narrow-band photometry that measures With T. Millar (UMIST) and other members of the bands of TiO and CN together with near-infrared contin- UMIST group, Herbst has explored the chemistry of pro- uum points. Two new SMC variables were found, both toplanetary nebulae in general and the source CRL 618 of which reach types later than M2.0 at minimum light; in particular.
4 With Y. Aikawa (Kobe, Japan), Herbst has studied tected in fluorescent H2, but that the 2.18 µm continuum molecular evolution in a collapsing pre-stellar core using is strongest in a broad region halfway between the illu- both gas-phase and grain–surface chemistry. minating star of NGC 7023 and the filaments observed Herbst and I. Smith (Birmingham, UK) are in the in the 3.3 µm aromatic feature. Furthermore, the ratio final stages of developing a new chemical network for of 2.18 µm flux to 3.3 µm flux decreases with projected low-temperature interstellar clouds. distance r from the star as r−2. This suggests that the With a group headed by O. Biham (Hebrew U., carriers of the 3.3 µm aromatic emission feature and the Jerusalem), Herbst has studied the formation of H2 and 2.18 µm continuum are not identical, as previously as- its isotopomers HD and D2 on the surfaces of small sumed. Instead they are separate ISM components, but grains using a mathematical technique known as the di- their flux ratio is regulated by the strength of the stellar rect master equation. The results show that HD and D2 illumination. have enhanced rates of production compared with H2 at Yoo, Sellgren, and R. Blum (CTIO) are pursuing certain temperatures. After learning to use the mas- follow-up images of other reflection nebulae with a range ter equation technique for small systems, Herbst and of physical conditions (Teff , G0,andn). Successful ob- OSU Physics graduate student T. Stantcheva are cur- serving runs at the IRTF in December 2002/January rently incorporating this technique for surface chemistry 2003 and July 2003 produced high-quality data for the into large-scale gas–grain chemical models of interstellar follow-up analysis. clouds. The results are expected to be more accurate than those of previous models, in which approximate 9 GALACTIC CENTER techniques for the rates of surface reactions were used. R. Blum (CTIO), S. V. Ram´ırez (SIRTF Science With E. Falco (SAO), E. Mediavilla (IAC) and J. Center), Sellgren, and K. Olsen (CTIO) have completed Mu˜noz (Valencia), Kochanek has been measuring the ex- a project on the star formation history of the inner- tinction curves of the dust in distant lens galaxies using a most regions of the Galaxy. They have obtained low- combination of HST imaging and spectroscopy designed resolution H−band and K−band spectra for roughly to reach the region around the redshifted 2175 A˚ bump. 60 stars to derive Teff and Mbol for the Galactic Cen- So far they have one system with a relatively normal ter stars. They place the Galactic Center stars on the Galactic extinction curve including the 2175 A˚ feature, H–R diagram, compare their positions to theoretical one system which must lack the feature and have an ex- isochrones with ages between 10 Myr and 12 Gyr, and tinction curve similar to the SMC, and one system where derive a star formation history for the central 5 pc of the image is behind a molecular cloud and has a peculiar the Galaxy. Most stars in the Galactic Center formed high RV extinction curve like those observed for dust in more than 5 Gyr ago, but star formation has continued Galactic molecular clouds. More data are being obtained through the lifetime of the Milky Way, with star forma- in the current HST Cycle. tion rates that vary from epoch to epoch. Pizagno, Sellgren, K. I. Uchida (Cornell) and M. W. Ram´ırez, Sellgren, Blum, and Terndrup continue Werner (JPL) are comparing the fraction of total dust their work on elemental abundances in cool, luminous emission emitted in the IRAS 12 µm band to predictions stars near the Galactic Center. They found in a pre- from models of various polycyclic hydrocarbon (PAH) vious paper that M supergiants and AGB stars in the molecules, and to theoretical models for a size distribu- GC have a distribution of [Fe/H] indistinguishable from tion of PAHs. They find that no single analog material that of similar cool, luminous stars in the solar neigh- can recreate the ratio of 12 µm to total infrared emission borhood. The range of ages for the Galactic Center su- from dust, but that a model including a range of PAH pergiants and AGB stars, from ∼ 10 Myr to ∼ 1Gyr, molecule sizes provides a better fit. suggests that some mechanism, or interplay between sev- Honors undergraduate student M. Pitts (now U. eral mechanisms, in the Galactic Center is holding the Hawai‘i), working with Sellgren, completed his Senior iron abundance at a fixed value over a Gyr of star forma- Honors thesis on the molecular hydrogen lines in the re- tion. They are currently acquiring data to detemine the flection nebula NGC 7023. They derived the rotational ratio of α−element abundances to iron abundances, as temperature of H2 in the photodissociation region in a clue to the type of stars (high-mass or low-mass) that NGC 7023, using spectra of pure H2 rotational lines ob- dominate chemical enrichment in the Galactic Center. tained with the Short Wavelength Spectrograph on the Ram´ırez, Sellgren, Blum, and Terndrup are following Infrared Space Observatory. Previous observations of up on Sellgren’s earlier work with J. Carr (NRL) and other photodissociation regions show that the rotational S. Balachandran (U. Maryland), which found that the temperatures are too high to be explained by current abundances of C, N, and O in one Galactic Center M models. supergiant implied extreme stellar mixing, beyond the Sellgren and J. An (U. Cambridge) have completed a predictions of the most recent high-mass stellar models paper on the difference in spatial morphology of the 3.3 including stellar rotation. They are currently analyzing µm aromatic emission feature and the 2.18 µm narrow- CNO abundances in several additional Galactic Center band continnum filter in the visual reflection nebula stars, and proposing to obtain more observations, to see NGC 7023. Surprisingly, they find the 3.3 µm emission if the extremely strong mixing in one Galactic Center feature is strongest in narrow filaments, previously de- M supergiant is unique to that star. A second Galactic
5 M supergiant shows normal mixing. It is intriguing that perpendicular collision with a small companion. the star with extra mixing is only 0.2 pc from the 4 Kassin, Pogge, and R. de Jong (STScI) used sur- 6 × 10 M black hole at the Galactic Center, while the face photometry of nearly 50 galaxies from the Ohio star with normal mixing is 30 pc from the central black State University Bright Spiral Galaxy Survey (OSUB- hole, but more results are needed to distinguish between SGS), that span the Hubble sequence and have high- possible explanations of unusual CNO abundances in one qualtiy rotation curves in the literature, to map radial Galactic Center star. distributions of dark and luminous matter. Kassin, Frogel, Pogge, G. Tiede (U. Florida), and 10 NORMAL GALAXIES Sellgren completed their pixel-by-pixel analysis of op- A. Stephens (U. Cat´olica, Chile) and Frogel com- tical and near-infrared images of NGC 4038/4039 (the pleted their analysis of NICMOS/HST data for M31. In Antennae). Their analysis of images from the OSUB- this final part of their study they determined the stel- SGS used multicolor techniques developed for analyzing lar populations present in M31 using nine sets of adja- the colors of stars. They derived maps of the distribu- cent HST–NICMOS Camera 1 and 2 fields with distances tions of stellar populations and dust extinction for the ranging from 2 to 20 from the center of the galaxy. two galaxies. Their analysis of the pixel-by-pixel stel- These infrared observations provide some of the highest lar population maps reveals two distinct episodes of star spatial resolution measurements to date of the central formation: one currently in progress and a second that regions of M31. Their data place tight constraints on occurred about 600 Myr ago. A roughly 15-Gyr-old pop- the maximum luminosities of stars in the bulge of M31. ulation is also found which traces the old disks of the The tip of the red giant branch (RGB) is clearly visi- galaxies and the bulge of NGC 4038. The ages derived ble at Mbol ∼−3.8, and the tip of the asymptotic giant are consistent with those found from previous HST ob- branch (AGB) extends to Mbol ∼−5.0. This AGB peak servations of individual star clusters. In addition, they luminosity is significantly fainter than claimed; through found five luminous super-star-clusters in the K−band direct comparisons and simulations they show that pre- images of the galaxies that do not appear on the B or vious measurements were affected by image blending. V images. These clusters are located in the overlap re- They do find field-to-field variations in the luminosity gion between the two galaxies, and are hidden by dust functions, but simulations show that these differences with visual extinctions of AV > 3 mag. The techniques can be produced by blending in the higher surface bright- they have developed should be generally applicable to ness fields. They conclude that the RGB of the bulge of the study of stellar populations in galaxies for which de- M31 is not measurably different from that of the Milky tailed star-cluster-scale resolution with HST is not pos- Way’s bulge. They also found an unusually high num- sible. ber of bright bluish stars (7.3 per square arcmin) which Kochanek is PI of a large HST program to obtain appear to be Galactic foreground stars. images of 45 multiply-imaged gravitational lenses. The Kaufman, C. Struck (Iowa State), E. Brinks (U. largest segment of the collaboration, known as CAS- Guanajuato), B. G. Elmegreen (IBM), D. M. Elmegreen TLES, consists of Kochanek, E. E. Falco (SAO), C. D. (Vassar), K. Sheth (Caltech), and M. Thomasson (On- Impey (Steward), C. R. Keeton (Chicago), B. McLeod sala) continued their study of the grazing encounter be- (SAO), J. Mu˜noz (Valencia), C. Peng (Steward), H.-W. tween the ocular galaxy IC 2163 and the spiral galaxy Rix (MPIA), D. Rusin (U. Penn) and J. Winn (Harvard). NGC 2207. Previous data are supplemented by 12CO Recent applications of these data and their earlier HST observations at SEST and OVRO and a radio contin- imaging surveys have been to use the fundamental plane uum image with 250 pc resolution. The star formation of gravitational lenses to determine the rate at which the rates per unit mass of gas are normal in both galaxies, stellar populations of early-type galaxies evolve between and neither galaxy contains an AGN, but the ratio of now and redshift unity and to estimate the mean mass FIR/radio continuum is abnormally low. Enhanced ra- distribution of early-type galaxies. The measured evolu- dio continuum emission, indicative of large-scale shock tion rate is consistent with a typical star formation red- fronts, occurs along the rim of the eye-shaped oval of shift of zf 2 – 3, very similar to what is measured for IC 2163 and in the outer part of the companion side galaxies in rich clusters. The mass profile of the galaxies of NGC 2207, particularly along a backlit spiral arm. must be very close to isothermal, indicating that early- New two-disk models of the encounter suggest moderate type galaxies have the same conspiracy between their mass transfer from IC 2163 to NGC 2207 and that tidal luminous and dark components to jointly produce a flat torques on NGC 2207 may have led to bulk compression rotation curve as is observed in spiral galaxies. of gas and magnetic fields on the companion side of NGC With the CASTLES collaboration, Kochanek has 2207. obtained deep infrared images of time-delay gravita- In another study of close, non-merging encounters, tional lenses using HST to measure the properties of the Kaufman and the same group have obtained broad–band lensed images of the quasar host galaxies in detail. These optical, Hα, radio continuum, and H i observations of the can be used to constrain the gravitational field of the spiral galaxy NGC 3145 and its two companions. Opti- lens galaxy in order to understand the estimates of the cally, NGC 3145 appears to have a swallowtail structure, Hubble constant from the time delays. As part of this a caustic that can be generated by a somewhat off-center program they also obtained Chandra X-ray Observatory
6 (CXO) images of the time-delay lenses, for which X-ray Ryden is undertaking a comparison of the global el- images were lacking, in order to search for nearby groups lipticity of late-type to early-type spirals, using near in- or clusters that need to be included in the models. frared imaging. Preliminary results indicate that late- Kochanek, in collaboration with E. Falco (CfA), M. type spirals (Sc to Sm) have apparent shapes which are Hartman (CfA), V. Hradecky (CfA), J. Huchra (CfA), consistent with a population of thin, axisymmetric disks. L. Macri (NOAO), and M. Pahre (CfA), has been study- Early-type spirals (Sa to Sbc) are markedly nonaxisym- ing the properites of local infrared-selected galaxies from metric in addition to being thicker. The different degrees the 2MASS survey. They have redshifts for all 2MASS of axisymmetry indicate different formation and evolu- galaxies with K ≤ 11.25 mag and a galactic latitude tion histories for early-type and late-type spirals. |b| > 5◦. These will be used to produce revised J, H and K infrared galaxy luminosity functions and densi- 11 AGNs ties. They have obtained deeper optical and infrared im- Fields collaborated with Pogge, P. Martini (Carnegie ages of a random sample of roughly 450 2MASS galaxies Obs.) and J. Shields (Ohio U.) to use narrow-slit STIS to measure their photometric profiles and to accurately observations of the nuclei of Seyfert 2 galaxies to get a calibrate the conversion of 2MASS luminosities into to- view of the nucleus with a minimum of contaminating tal luminosities and estimates of the infrared luminos- starlight. ity density. They have also obtained long-slit spectra of Fields, with Mathur and Pogge, is investigating the these galaxies to measure rotation curves and velocity narrow-line Seyfert 1 galaxy Mrk 1044 with UV obser- dispersions in order to make an accurate estimate of the vations from HST. High-resolution spectra around Lyα, local velocity function of galaxies. M. White (Berkeley) C iv and N will give the metallicity of the warm absorber and Kochanek are using the 2MASS galaxies to produce material intrinsic to Mrk 1044, as well as of interstellar local X-ray cluster catalogs using a modern matched fil- material resident in our own Galaxy. This analysis will ter method. The catalogs are cross-correlated with X-ray be heavily strengthened by the inclusion of two other luminosity and temperature measurements and are used datasets, near-simultaneous observations by FUSE and to explore the halo occupancy distribution. Chandra. Kollmeier and Miralda-Escud´e have been working on Grupe, Mathur and M. Elvis (CfA) have analyzed a project aimed at understanding black hole growth in the XMM–Newton data of two Broad Absorption Line the centers of galaxies, and the connection between this Quasars (BAL QSOs), Q1246−057 and SBS 1542+541. growth and the dynamics of the stars in the bulge com- They found that the intrinsic X-ray luminosity is similar ponent of these galaxies. to non-BAL QSOs suggesting that the often observed X- Pizagno, Weinberg, Pogge, F. Prada (Calar Alto), ray weakness in BAL QSOs is due to absorption rather and H.-W. Rix (MPIA) are studying the Tully-Fisher than being intrinsically X-ray weak. relation for a sample of galaxies selected from the Sloan Grupe and Mathur, in collaboration with B. Wilkes Digital Sky Survey (SDSS). The galaxies were selected and M. Elvis (both CfA), studied the XMM-Newton from the SDSS database to cover a wide range in lumi- data of two high redshift quasars: RX J1028−0844 and nosity, but have no restrictions on the morphology or BR 0351−1034. The data for the radio-loud quasar RX degree of interaction of the galaxy. To obtain dynam- J1028−0844 showed that the high intrinsic absorption of ical information, long-slit Hα spectra have been taken neutral elements is lower by at least a factor of 10 than at Calar Alto (Prada) and MDM observatories (Piza- previously claimed from ASCA observation. Most likely gno, Pogge, and Weinberg). It is found that the intrin- this is due to calibration uncertainties in the ASCA data sic scatter is slightly larger for this sample than previ- below 1 keV and the superior sensitivity of the EPIC PN ous pruned Tully-Fisher samples. A correlation between detector down to energies < 0.2 keV. The radio-quiet color and Tully-Fisher residual is found that resembles quasar BR 0351−1034 became fainter by a factor of 6 the findings of previous studies. A more detailed study between the XMM observation and a pointed ROSAT of correlations among residuals, and making mass mod- PSPC observation ten years earlier. A change in the els from the SDSS images at g, r,andi, are planned for spectral shape of the X-ray spectrum suggests that part the future. of this variability is due to a variable cold absorber in The global ellipticity of disk galaxies is of interest the source. because the shape of the luminous disk is linked to the Grupe, B. J. Wills (UT Austin), K. M. Leighly (U. poorly determined non-axisymmetry of dark halos. Ry- Oklahoma, Norman), and H. Meusinger (Thueringer den, using photometric information from the Sloan Dig- Landessternwarte Tautenburg, Germany) have studied ital Sky Survey, determined that the projected shapes the optical properties of a complete sample of bright, of disk galaxies are consistent with a log–normal distri- soft-X-ray-selected AGN. About half of these sources bution of intrinsic ellipticities, with ln ε ≈−1.8 ± 0.9 are Narrow-Line Seyfert 1 galaxies (NLS1s) which show in the i band. This much ellipticity in the underlying the strongest Fe ii emission, steepest X-ray spectra and potential would produce a full magnitude of scatter in strongest soft X-ray variability. They found that there the Tully-Fisher relation, more than is observed. Thus, are no differences in the luminosity, redshift, and Hβ the distribution of starlight is not a good tracer of the equivalent width distributions between NLS1s and Broad underlying potential shape. Line Seyfert 1s. Grupe was able to show, in a Princi-
7 pal Component Analysis of the soft-X-ray-selected sam- D. Nestor, (U. Pittsburgh), W. Lane (NRL), and J. Berg- ple, that the most important parameter that governs the eron (Institut d’Astrophysique), studied four absorption properties of the AGN is the Eddington accretion rate. systems with z<1 from their sample of damped Lyα Kochanek and collaborators have developed a radi- (DLA) systems at low redshifts. They used optical and cally new method of analyzing quasar microlensing light near-infrared imaging from MDM, WIYN, and IRTF to curves. They have applied it to the lens Q2237+0305 to derive photometric redshifts for galaxies in the fields sur- estimate the mean stellar mass, the size of the quasar rounding background QSOs. The identified DLA galax- accretion disk, and the mass of its black hole. They ies span a mixture of morphological types from patchy, 9 find, for example, that the black hole mass is 10 M irregular, and low surface brightness to spiral galaxies. ∗ ∗ (factor of two uncertainty) and that the lens galaxy is The luminosities range from 0.02 LK to 1.2 LK. The to- composed mostly of stars (as expected for a lens where tal sample now contains 14 DLA galaxies in the redshift the images are seen through the bulge of a large, nearby range 0.05 ≤ z ≤ 1, with low-luminosity dwarf galaxies spiral galaxy). With Gould, Depoy, E. Falco (SAO), E. at small impact parameters being most common. Four Mediavilla (IAC), N. Morgan (Yale), Pogge, P. Schechter of the five highest column density systems, which dom- (MIT), E. Turner (Princeton), and J. Winn (SAO) he inate in the determination of the cosmological neutral has assembled a consortium to industriously monitor gas mass density, arise in low surface brightness dwarf gravitational lenses in order to mass-produce both time galaxies. delays and microlensing light curves. The primary ob- Bentz and Osmer carried out a search of the Sloan jective is to determine the surface density and stellar Early Data Release (EDR) for nitrogren–rich quasars mass fraction of the lens galaxies in the transition re- to see if more objects like Q0353−383 could be found. gion near 1–3 effective radii where the galaxy changes Q0353−383 shows evidence for CNO processing and a from being dominated by the stars to being dominated metallicity greater than solar, but it is the only object of by dark matter. Secondary objectives are to survey the its kind that is known. It may represent a late stage in size and structure of the source quasar accretion disks, the evolution of the central region of its host galaxy, to estimate their black hole masses, and to determine and it is important to find more such objects. Six- the mean stellar masses in the lens galaxies. teen candidates were found in the EDR, four of which Kollmeier and Weinberg have been working on a had prominent emission lines of N iii] and N iv], but project aimed at determining the connection between op- none had emission as strong as in Q0353−383. Subse- tical and X-ray obscuration in AGN. They are develop- quently, in a collaboration with P. Hall (Princeton), they ing a theoretical framework for predicting how the AGN searched the Sloan Data Release 1 (DR1) and found 20 luminosity function should look as a function of wave- objects with strong nitrogen emission, four of which have length and selection criteria. This gets to the heart of strengths comparable to Q0353−383. The search also the X-ray/optical obscuration connection in AGN. uncovered a number of quasars with unusual emission- Mathur has been using X-ray and UV spectroscopy line or absorption-line properties. to probe the regions near the central black hole in ac- One such object is a bright Lyman break galaxy tive galactic nuclei using Chandra, XMM–Newton, HST, (LBG) candidate at z =2.55. This led Bentz, Osmer, and FUSE. Her interests include broad absorption line and Weinberg to search the DR1 for similar objects, and quasars, narrow line Seyfert 1 galaxies, high redshift five more were found. The candidates have r magni- quasars, and AGN evolution. Recently she has been tudes of 19.8 to 20.5 and redshifts of 2.5 to 2.8. If they working on understanding the low redshift warm–hot in- are starburst galaxies and are not gravitationally lensed, tergalactic medium using high resolution spectroscopy they are the most luminous LBGs known. However, their with Chandra and FUSE. spectra are unusual and do not match in detail known Miralda-Escud´e and OSU Physics graduate student LBGs, AGNs, or submm–selected starburst galaxies. It M. Schirber found three pairs of quasars in the Sloan is possible they are hybrid starburst/AGNs. survey within an angular separation of 4 arc minutes, Onken, Peterson, Pogge, and Vestergaard, with L. at different redshifts, to measure the effect of the lower Ferrarese and D. Merritt (Rutgers) and A. Wandel (He- redshift quasar on the Lyα forest in the spectrum of brew U.) are investigating the relationship between host- the higher redshift quasar. They calculated that the in- galaxy bulge velocity dispersion and the central black tensity of ionizing radiation from the foreground quasar hole mass inferred from reverberation mapping measure- should be many times larger than the cosmic ionizing ments. They find that active galaxies show the same background. Although they were expecting to see re- strong correlation between these properties that is found duced Lyα absorption because of the higher ionizing in- in quiescent galaxies, and that the black hole mass mea- tensity, the spectra show, if anything, an increase in ab- surements based on reverberation results are accurate to sorption. They investigated three possible explanations: a factor of ∼ 3. In collaboration with M. Malkan (UCLA) high gas density near a quasar, quasar variability over and H. Netzer, D. Maoz, and S. Kaspi (Tel-Aviv U.), timescales of order millions of years, or anisotropy of the they are also working towards improving both the ac- ionizing emission. They discussed problems with each of curacy and precision of reverberation-based mass mea- these explanations. surements. Once this is complete, improved luminosities, Monier, in collaboration with D. Turnshek, S. Rao, both absolute and relative to the Eddington luminosity,
8 and scaling relationships between the broad-line region culated Kα resonance strengths in O i –Ovi. size and luminosity will be defined more precisely. T.A.A. Sigut (U. Western Ontario) and Pradhan Bentz, Peterson, Pogge, and Vestergaard are work- have computed theoretical templates of ∼ 23,000 Fe ii ing on a Hubble Space Telescope project to image all spectral lines from IR to UV for conditions in the broad the reverberation–mapped AGNs for the purpose of de- line regions of AGN, incorporating exact radiative trans- termining the host–galaxy contribution to their optical fer and using the Iron Project data computed by Na- fluxes. har. Among the important physical processes included Peterson is leading two approved HST target-of- is Lyα fluorescent excitation. The theoretical line fluxes opportunity (TOO) programs. The first of these is in- are available from the authors and have been used for tended to measure nuclear stellar kinematics in order to spectral analysis of AGN by a number of researchers. use stellar dynamical methods to measure the black hole Steed and collaborators present a flexible frame- mass in two AGNs for which the black hole radius of in- work for constructing physical models of quasar evo- fluence is resolved with HST. The TOO will be initiated lution that can incorporate a wide variety of observa- when one of the sources goes into a low–flux state, thus tional constraints, such as multi-wavelength luminosity reducing the problem of nuclear glare. The second TOO functions, estimated masses and accretion rates of ac- program is to obtain an ultraviolet spectrum of NGC tive black holes, space densities of quasar host galaxies, 4051 to complement optical data that suggest that, in clustering measurements, and the mass function of black faint states, the inner part of the accretion disk goes holes in the local universe. The central actor in this for- into a radiatively inefficient accretion mode. Collabo- mulation is the accretion rate distribution p(M˙ |M,z), rators are monitoring these candidate targets in X-rays the probability that a black hole of mass M at redshift with RXTE (I. McHardy, U. Southampton) and in the z accretes at a rate M˙ in Eddington units. Given a optical (S. Sergeev, Crimean Astrophysical Obs.). model of accretion physics that specifies the radiative ef- Peterson continues to work with K. Horne (U. of St. ficiency and spectral energy distribution as a function of Andrews) on reverberation–mapping simulations for the M˙ , the quasar luminosity function (QLF) is determined purpose of defining observational requirements for fu- by a convolution of p(M˙ |M,z) with the black hole mass ture efforts, one of which will be a proposal for a multi- function n(M,z). In the absence of mergers, p(M˙ |M,z) wavelength Medium Explorer, Kronos, which is designed also determines the full evolution of n(M,z), given a specifically for astrotomography. “boundary value” of n(M) at some redshift. If p(M˙ |z) Pogge and Fields, along with P. Martini (Carnegie is independent of mass, then the asymptotic slopes of the Obs./CfA) and J. Shields (Ohio U.), are completing a QLF match the asymptotic slopes of n(M), and n(M) 33–orbit Hubble Space Telescope study of the nuclear evolves in a self-similar fashion, retaining its shape while (r<30 pc) spectra of a sample of 20 Seyfert 2 galax- shifting to higher masses. Matching the observed decline ies using the STIS spectrometer. They have detected of the QLF “break” luminosity at z<2 requires either weak, broad Hα emission lines characteristic of Type 1 ashiftinp(M˙ |z) that increases the relative probability Seyfert nuclei in a number of these galaxies, and often of low accretion rates or an evolving mass dependence see faint high-excitation narrow lines that are only visible of p(M˙ |M,z) that preferentially shuts off accretion onto because Hubble allows them to get past the contaminat- high mass black holes at low z. These two scenarios ing starlight into the nucleus proper. These objects are make different predictions for the masses and accretion effectively “declassified” as Seyfert 2s. A few of these rates of active black holes. If the first mechanism dom- Seyfert 2s, however, are clearly unreddened and do not inates, then the QLF changes character between z =2 show broad emission lines, and therefore are plausible and z = 0, shifting from a sequence of black hole mass to- candidates for “true” Seyfert 2s: objects without broad wards a sequence of L/Ledd. Steed and collaborators use lines not because they are blocked by the so-called “ob- their framework to compare the predictions of five mod- scuring torus,” but because they are truly absent. They els that illustrate different assumptions about the quasar have been granted 40 ksec with the Chandra X-ray Ob- population: two dominated by unobscured thin-disk ac- servatory to investigate their X-ray properties. cretion with short and long quasar lifetimes, respectively, Pradhan’s group is theoretically studying the time one with a 4:1 ratio of obscured to unobscured systems, dependence of Kα lines of helium–like iron as function one with substantial black hole merger activity at low of temperature, density, and non-thermal photoexcita- redshift, and one with substantial low redshift growth in tion, that may be applicable to accretion disk flares and radiatively inefficient flows. They discuss the observa- temporal temperature variability of AGN. tional advances that would be most valuable for distin- X-ray O vi lines formed by resonance absorption, guishing such models and for pinning down the physics as predicted by Pradhan, have been observed in AGN that drives black hole and quasar evolution. outflows. It is inferred that the column densities from Vestergaard is continuing to study the distribution of O vi UV absorption alone are ‘often severely underesti- black-hole masses in the centers of high redshift (z>1.5) mated.’ This concept can also be applied to resonance quasars. The first results show that even at the highest complexes in several ionization states of an element for redshifts (4