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We present a detailed analysis of the protostellar outflow activity in the massive star-forming region NGC 3324, as revealed by new Early Release Observations (ERO) from the James Webb Space Telescope (JWST). Emission from numerous outflows is revealed in narrow-band images of hydrogen Paschen-$\alpha$ (Pa-$\alpha$) and molecular hydrogen. In particular, we report the discovery of 24 previously unknown outflows based on their H$_2$ emission. We find three candidate driving sources for these H$_2$ flows in published catalogs of young stellar objects (YSOs) and we identify 15 IR point sources in the new JWST images as potential driving protostars. We also identify several Herbig-Haro (HH) objects in Pa-$\alpha$ images from JWST; most are confirmed as jets based on their proper motions measured in a comparison with previous Hubble Space Telescope (HST) H$\alpha$ images. This confirmed all previous HST-identified HH jets and candidate jets, and revealed 7 new HH objects. The unprecedented capabilities of JWST allow the direct comparison of atomic and molecular outflow components at comparable angular resolution. Future observations will allow quantitative analysis of the excitation, mass-loss rates, and velocities of these new flows. As a relatively modest region of massive star formation (larger than Orion but smaller than starburst clusters), NGC 3324 offers a preview of what star formation studies with JWST may provide., Comment: MNRAS, accepted

22 pags., 8 figs., 1 tab., Massive stars disrupt their natal molecular cloud material through radiative and mechanical feedback processes. These processes have profound effects on the evolution of interstellar matter in our Galaxy and throughout the universe, from the era of vigorous star formation at redshifts of 1-3 to the present day. The dominant feedback processes can be probed by observations of the Photo-Dissociation Regions (PDRs) where the far-ultraviolet photons of massive stars create warm regions of gas and dust in the neutral atomic and molecular gas. PDR emission provides a unique tool to study in detail the physical and chemical processes that are relevant for most of the mass in inter-and circumstellar media including diffuse clouds, proto-planetary disks, and molecular cloud surfaces, globules, planetary nebulae, and star-forming regions. PDR emission dominates the infrared (IR) spectra of star-forming galaxies. Most of the Galactic and extragalactic observations obtained with the James Webb Space Telescope (JWST) will therefore arise in PDR emission. In this paper we present an Early Release Science program using the MIRI, NIRSpec, and NIRCam instruments dedicated to the observations of an emblematic and nearby PDR: the Orion Bar. These early JWST observations will provide template data sets designed to identify key PDR characteristics in JWST observations. These data will serve to benchmark PDR models and extend them into the JWST era. We also present the Science-Enabling products that we will provide to the community. These template data sets and Science-Enabling products will guide the preparation of future proposals on star-forming regions in our Galaxy and beyond and will facilitate data analysis and interpretation of forthcoming JWST observations., Support for JWST-ERS program ID 1288 was provided through grants from the STScI under NASA contract NAS5-03127 to STScI (K.G., D.V.D.P., M.R.), Univ. of Maryland (M.W., M.P.), Univ. of Michigan (E.B., F.A.), and Univ. of Toledo (T.S.-Y.L.). O.B. and E.H. are supported by the Programme National “Physique et Chimie du Milieu Interstellaire” (PCMI) of CNRS/INSU with INC/INP co-funded by CEA and CNES, and through APR grants 6315 and 6410 provided by CNES. E. P. and J.C. acknowledge support from the National Science and Engineering Council of Canada (NSERC) Discovery Grant program (RGPIN-2020-06434 and RGPIN-2021-04197 respectively). E.P. acknowledges support from a Western Strategic Support Accelerator Grant (ROLA ID 0000050636). J.R.G. and S.C. thank the Spanish MCINN for funding support under grant PID2019-106110GB-I00. Work by M.R. and Y.O. is carried out within the Collaborative Research Centre 956, subproject C1, funded by the Deutsche Forschungsgemeinschaft (DFG)—project ID 184018867. T.O. acknowledges support from JSPS Bilateral Program, grant No. 120219939. M.P. and M.W. acknowledge support from NASA Astrophysics Data Analysis Program award #80NSSC19K0573. C.B. is grateful for an appointment at NASA Ames Research Center through the San José State University Research Foundation (NNX17AJ88A) and acknowledges support from the Internal Scientist Funding Model (ISFM) Directed Work Package at NASA Ames titled: “Laboratory Astrophysics—The NASA Ames PAH IR Spectroscopic Database.”

We present the first images of the nebula around eta Carinae obtained with HST/WFC3, including a UV image in the F280N filter that traces MgII emission, plus contemporaneous imaging in the F336W, F658N, and F126N filters that trace near-UV continuum, [NII], and [FeII], respectively. The F336W and F658N images are consistent with previous images in these filters, and F126N shows that for the most part, [FeII] 12567 traces clumpy shocked gas seen in [NII]. The F280N image, however, reveals MgII emission from structures that have not been seen in any previous line or continuum images of eta Carinae. This image shows diffuse MgII emission immediately outside the bipolar Homunculus nebula in all directions, but with the strongest emission concentrated over the poles. The diffuse structure with prominent radial streaks, plus an anticorrelation with ionized tracers of clumpy shocked gas, leads us to suggest that this is primarily MgII resonant scattering from unshocked, neutral atomic gas. We discuss the implied structure and geometry of the MgII emission, and its relation to the Homunculus lobes and various other complex nebular structures. An order of magnitude estimate of the neutral gas mass traced by MgII is 0.02Msun, with a corresponding kinetic energy around 1e47erg. This may provide important constraints on polar mass loss in the early phases of the Great Eruption. We argue that the MgII line may be an excellent tracer of significant reservoirs of freely expanding, unshocked, and otherwise invisible neutral atomic gas in a variety of stellar outflows., Comment: accepted by MNRAS. 15 pages, 6 figures

We present new proper motion measurements of optically emitting oxygen-rich knots of supernova remnant 1E 0102.2-7219 (E0102), which are used to estimate the remnant's center of expansion and age. Four epochs of high resolution Hubble Space Telescope images spanning 19 yr were retrieved and analyzed. We found a robust center of expansion of alpha=1:04:02.48 and delta=-72:01:53.92 (J2000) with 1-sigma uncertainty of 1.77 arcseconds using 45 knots from images obtained with the Advanced Camera for Surveys using the F475W filter in 2003 and 2013 having the highest signal-to-noise ratio. We also estimate an upper limit explosion age of 1738 +/- 175 yr by selecting knots with the highest proper motions, that are assumed to be the least decelerated. We find evidence of an asymmetry in the proper motions of the knots as a function of position angle. We conclude that these asymmetries were most likely caused by interaction between E0102's original supernova blast wave and an inhomogeneous surrounding environment, as opposed to intrinsic explosion asymmetry. The observed non-homologous expansion suggests that the use of a free expansion model inaccurately offsets the center of expansion and leads to an overestimated explosion age. We discuss our findings as they compare to previous age and center of expansion estimates of E0102 and their relevance to a recently identified candidate central compact object., 14 pages, 11 figures, revised according to referee comments and resubmitted to ApJ

We present a comprehensive study of phase curves and secondary eclipses in the Kepler data set using all data from 16 quarters that were available in 2013-2014. Our sample consists of 20 confirmed planets with R_p > 4 R_e ,P < 10d, V_mag < 15. Here we derive their temperatures and albedos, with an eye towards constraining models for the formation and evolution of such planets. Where there was overlap our results confirm parameters derived by previous studies, whereas we present new results for Kepler 1b-8b, 12b-15b, 17b, 40b, 41b, 43b, 44b, 76b, 77b, and 412b derived in a consistent manner. We also present lightcurve analyses for Kepler 91b and Kepler 74b, which both show extra dimmings at times other than from the expected primary and secondary eclipses. Corrected for thermal emission we find most of the massive planets from our sample to be low in albedo (0.1)., 50 pages, 7 figures - PASP accepted

The Hubble Space Telescope has been a scientific marvel that has provided unimaginable imagery and scientific discovery. Its exquisite UV/Visible imaging performance is unmatched from the ground. In NASA’s future planning, the earliest possible successor mission would be in the 3030s, well beyond the expected lifetime of Hubble. The ASTRO-1 space telescope is a 1.8m off-axis (unobscured) observatory that looks to fill this critical void with Hubble-like performance to continue the scientific quest while also providing the possibility for exoplanet research with a coronagraphic instrument and/or a free flying starshade. BoldlyGo Institute seeks to reach beyond NASA funding to leverage the high public interest in space research and exploration, and the search for life beyond Earth.

The NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA), a 2.5-meter infrared telescope on board a Boeing 747-SP, will conduct 0.3 - 1,600 μm photometric, spectroscopic, and imaging observations from altitudes as high as 45,000 ft., where the average atmospheric transmission is greater than 80 percent. SOFIA's first light cameras and spectrometers, as well as future generations of instruments, will make important contributions to the characterization of the physical properties of exoplanets. Our analysis shows that optical and near-infrared photometric and spectrophotometric follow-up observations during planetary transits and eclipses will be feasible with SOFIA's instrumentation, in particular the HIPO-FLITECAM optical/NIR instruments. The airborne-based platform has unique advantages in comparison to ground- and space-based observatories in this field of research which we will outline here. Furthermore we will present two exemplary science cases, that will be conducted in SOFIA's cycle 1.

We present Space Telescope Imaging Spectrograph (STIS) spectral images of the HH~30 stellar jet taken through a wide slit over two epochs. The jet is unresolved spectrally, so the observations produce emission-line images for each line in the spectrum. This rich dataset shows how physical conditions in the jet vary with distance and time, produces precise proper motions of knots within the jet, resolves the jet width close to the star, and gives a spectrum of the reflected light from the disk over a large wavelength range at several positions. We introduce a new method for analyzing a set of line ratios based on minimizing a quadratic form between models and data. The method generates images of the density, temperature and ionization fraction computed using all the possible line ratios appropriately weighted. In HH 30, the density declines with distance from the source in a manner consistent with an expanding flow, and is larger by a factor of two along the axis of the jet than it is at the periphery. Ionization in the jet ranges from ~ 5% to 40%, and high ionization/excitation knots form at about 100 AU from the star and propagate outward with the flow. These high-excitation knots are not accompanied by corresponding increases in the density, so if formed by velocity variations the knots must have a strong internal magnetic pressure to smooth out density increases while lengthening recombination times.

The extreme, high-velocity interstellar absorption-line profiles toward η Carinae and 16 neighboring stars in Trumpler 16 are examined, including several new sight lines observed in the ultraviolet with the Hubble Space Telescope or in the optical from the Magellan and European Southern Observatories. No two sight lines are identical, but many velocity components are in common. When the velocity scale is shifted to a standard of rest defined by the Carina Nebula emission lines, the symmetries between negative and positive velocities are striking; at least 15 distinct "shells" can be recognized. This circumstance suggests that the complex expanding structures are predominantly in front of the ionizing cluster. There may be a relationship to indications of a supernova remnant in this direction, including a recent Chandra X-Ray Observatory image. Interpretations in terms of high-energy phenomena generated by ongoing star formation possibly on the near side of the giant H ii region are also discussed.

Hubble Space Telescope images with the Wide Field Planetary Camera 2 of the young, oxygen-rich, Crab-like supernova remnant SNR0540-69.3 in the Large Magellanic Cloud (LMC) reveal details of the emission distribution and the relationship between the expanding ejecta and synchrotron nebula. The emission distributions appear very similar to those seen in the Crab nebula, with the ejecta located in a thin envelope surrounding the synchrotron nebula. The [O III] emission is more extended than other tracers, forming a faint "skin" around the denser filaments and synchrotron nebula, as also observed in the Crab. The [O III] exhibits somewhat different kinematic structure in long-slit spectra, including a more extended high-velocity emission halo not seen in images. Yet even the fastest expansion speeds in SNR 0540 s halo are slow when compared to most other young supernova remnants, though the Crab nebula has similar slow expansion speeds. We show a striking correspondence between the morphology of the synchrotron nebula observed in an optical continuum filter with that recently resolved in Chandra X-ray images. We argue that the multi-component kinematics and filamentary morphology of the optical emission-line features likely result from magnetic Rayleigh-Taylor instabilities that form as the synchrotron nebula expands and sweeps up ejecta, as seen in the Crab nebula. Our images and spectra help to refine our understanding of SNR 0540 in several more detailed respects: they confirm the identification of H(alpha)+[N II] in the red spectrum, they show that the systemic velocity of SNR 0540 is not significantly different from that of the LMC, and they hint at a lower Ne abundance than the Crab (potentially indicating a more massive progenitor star).

We use low-dispersion spectra obtained at the Magellan Observatory to study the broad H-alpha emission from the reverse shock of the infant supernova remnant SNR1987A. These spectra demonstrate that the spatio-kinematic structure of the reverse shock can be distinguished from that of the circumstellar ring and hotspots, even at ground-based spatial resolution. We measure a total dereddened H-alpha flux of 1.99(pm0.22)e-13 ergs/s/cm2 at an epoch 18.00 years after outburst. At 50 kpc, the total reverse shock luminosity in H-alpha is roughly 15 Lsun, which implies a total flux of neutral hydrogen atoms across the reverse shock of 8.9e46/s, or roughly 2.3e-3 Msun/yr. This represents an increase by a factor ~4 since 1997. Lyman continuum radiation from gas shocked by the forward blast wave can ionize neutral hydrogen atoms in the supernova debris before they reach the reverse shock. If the inward flux of ionizing photons exceeds the flux of hydrogen atoms approaching the reverse shock, this pre-ionization will shut off the broad Ly-alpha and H-alpha emission. The observed X-ray emission of SNR1987A implies that the ratio of ionizing flux to hydrogen atom flux across the reverse shock is presently at least 0.04. The X-ray emission is increasing much faster than the flux of atoms, and if these trends continue, we estimate that the broad Ly-alpha and H-alpha emission will vanish within about 7 years., 5 pgs, Fig 1 in color, accepted by ApJ Letters

We present narrowband images of eta Carinae in the light of [O III] 5007 obtained with HST/WFPC2, as well as a ground-based image in the same emission line with a larger field of view. These images show a thin veil of [O III] emission around eta Car and its ejecta, confirming the existence of an oxygen-bearing ``cocoon'' inferred from spectra. This [O III] veil may be the remnant of the pre-outburst wind of eta Car, and its outer edge probably marks the interface where eta Car's ejecta meet the stellar wind of the nearby O4 V((f)) star HD303308 or other ambient material -- i.e., it marks the ``astropause'' in eta Car's wind. This veil is part of a more extensive [O III] shell that appears to be shaped and ionized by HD303308. A pair of HST images with a 10 yr baseline shows no proper motion, limiting the expansion speed away from eta Car to 12pm13 km/s, or an expansion age of a few times 10^4 yr. Thus, this is probably the decelerated pre-outburst LBV wind of eta Car. The [O III] morphology is very different from that seen in [N II], which traces young knots of CNO-processed material; this represents a dramatic shift in the chemical makeup of material recently ejected by eta Car. This change in the chemical abundances may have resulted from the sudden removal of the star's outer envelope during eta Car's 19th century outburst or an earlier but similar event., Comment: 11 pages, 4 figs. Figs 1 and 3 in color. Accepted to AJ, October 2005

We present high-resolution X-ray proper motion measurements of Cassiopeia A using Chandra observations from 2000 and 2002. We separate the emission into four spectrally distinct classes: Si-dominated, Fe-dominated, low-energy-enhanced, and continuum-dominated. These classes also represent distinct spatial and kinematic components. The Si- and Fe-dominated classes are ejecta and have a mean expansion rate of 0.2%/yr. This is the same as for the forward shock filaments but less than the 0.3%/yr characteristic of optical ejecta. The low-energy-enhanced spectral class possibly illuminates a clumpy circumstellar component and has a mean expansion rate of 0.05%/yr. The continuum-dominated emission likely represents the forward shock and consists of diffuse circumstellar material which is seen as a circular ring around the periphery of the remnant as well as projected across the center., 15 pages, 3 figures, accepted to ApJ

We report the first detection of X-ray emission associated with the Homunculus Nebula which surrounds the supermassive star Eta Carinae. The emission is characterized by a temperature in excess of 100 MK, and is consistent with scattering of the time-delayed X-ray flux associated with the star. The nebular emission is bright in the northwestern lobe and near the central regions of the Homunculus, and fainter in the southeastern lobe. We also report the detection of an unusually broad Fe K fluorescent line, which may indicate fluorescent scattering off the wind of a companion star or some other high velocity outflow. The X-ray Homunculus is the nearest member of the small class of Galactic X-ray reflection nebulae, and the only one in which both the emitting and reflecting sources are distinguishable., 17 pages, 5 figures, accepted by ApJ

The 3" pair of B9 stars, HD 28867, is one of the brightest X-ray sources in the Taurus-Auriga star forming region. In this multi-wavelength study, we attempt to deduce the source of the X-ray emission. We show that the East component is the X-ray source. The East component has a near-IR excess and displays narrow absorption lines in the optical, both of which are consistent with a cool stellar companion. This companion is one of the brightest low mass pre-main sequence stars in Tau-Aur; at 2 microns it and the B9 star are equally bright. We see evidence for radial velocity variability in the cool component of >34 km/s. It is not visible in K band speckle imaging, which constrains the companion to lie within 14 AU of the B star. We also report on a possible fourth member of the group, an M1 star 18" south of HD 28867., Comment: accepted by the Astronomical Journal

We report the discovery of dozens of compact objects in the Carina Nebula (NGC 3372) that closely resemble proplyds (photoablating protoplanetary disks and dark silhouette disks) seen previously in the Orion Nebula. This is the first detection of a large number of such objects outside Orion. They imply that low- and intermediate-mass star formation is proceeding actively in Carina, despite threatening conditions imposed by very hot massive stars. The proplyd candidates that we have detected are larger than those in Orion but more compact than irregular molecular globules within the H II region. Smaller proplyds may still be lurking in Carina, waiting to be discovered. Orion apparently lacks objects of comparable size, and we consider several explanations. Larger proplyds may come from larger and more massive circumstellar disks surrounding young Herbig Ae/Be stars that should be numerous in Carina. Alternatively, far-UV radiation from the massive star η Car may have, in the recent past, enhanced photoablation and expanded proplyd ionization fronts. Some unusual proplyd candidates may also imply that time-dependent effects associated with η Car's current evolutionary state may be critical.

We discuss optical and infrared emission from the putative planetary nebula in the young open cluster NGC 3572. Velocity images of [N ii] λ6583 obtained with the Rutgers/CTIO Fabry‐Perot interferometer reveal that most gas in the nebula is expanding at velocities ≲5 km s \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $^{-1}$ \end{document} , with marginal evidence for bipolar expansion. A few outer condensations are seen at faster redshifted velocities, but their origin is uncertain. Optical spectra reveal a spatial exc...

We summarize 2007 radial velocity measurements of 91 metal-poor field red giants. Excluding binary systems with orbital solutions, our coverage averages 13.7 yr per star, with a maximum of 18.0 yr. We report four significant findings. (1) Sixteen stars are found to be spectroscopic binaries, and we present orbital solutions for 14 of them. The spectroscopic binary frequency of the metal-poor red giants, with [Fe/H] ≤ -1.4, for periods less than 6000 days, is 16% ± 4%, which is not significantly different from that of comparable-metallicity field dwarfs, 17% ± 2%. The two CH stars in our program, BD -1°2582 and HD 135148, are both spectroscopic binaries. (2) Velocity jitter is present among about 40% of the giants with MV ≤ -1.4. The two best-observed cases, HD 3008 and BD +22°2411, show pseudoperiodicities of 172 and 186 days, longer than any known long-period variable in metal-poor globular clusters. Photometric variability seen in HD 3008 and three other stars showing velocity jitter hints that starspots are the cause. However, the phasing of the velocity data with the photometry data from Hipparcos is not consistent with a simple starspot model for HD 3008. We argue against orbital motion effects and radial pulsation, so rotational modulation remains the best explanation. The implied rotational velocities for HD 3008 and BD +22°2411, both with MV ≤ -1.4 and R ≈ 50 R⊙, exceed 12 km s-1. (3) Including HD 3008 and BD +22°2411, we have found signs of significant excess line broadening in eight of the 17 red giants with MV ≤ -1.4, which we interpret as rotation. In three cases, BD +30°2034, CD -37°14010, and HD 218732, the rotation is probably induced by tidal locking between axial rotation and the observed orbital motion with a stellar companion. But this cannot explain the other five stars in our sample that display signs of significant rotation. This high frequency of elevated rotational velocities does not appear to be caused by stellar mass transfer or mergers: there are too few main-sequence binaries with short enough periods. We also note that the lack of any noticeable increase in mean rotation at the magnitude level of the red giant branch luminosity function bump argues against the rapid rotation's being caused by the transport of internal angular momentum to the surface. Capture of a planetary-mass companion as a red giant expands in radius could explain the high rotational velocities. (4) We also find significant rotation in at least six of the roughly 15 (40%) red horizontal-branch stars in our survey. It is likely that the enhanced rotation seen among a significant fraction of both blue and red horizontal-branch stars arose when these stars were luminous red giants. Rapid rotation alone therefore appears insufficient cause to populate the blue side of the horizontal branch. While the largest projected rotational velocities seen among field blue and red horizontal-branch stars are consistent with their different sizes, neither are consistent with the large values we find for the largest red giants. This suggests that some form of angular momentum loss (and possibly mass loss) has been at work. Also puzzling is the apparent absence of rotation seen in field RR Lyrae variables. Angular momentum transfer and conservation in evolved metal-poor field stars thus pose many interesting questions for the evolution of low-mass stars.

The abundance of heavy elements (metallicity) in the photospheres of stars similar to the Sun provides a 'fossil' record of the chemical composition of the initial protoplanetary disk. Metal-rich stars are much more likely to harbour gas giant planets(1-4), supporting the model that planets form by accumulation of dust and ice particles(5). Recent ground-based surveys suggest that this correlation is weakened for Neptunian-sized planets(4,6-9). However, how the relationship between size and metallicity extends into the regime of terrestrial-sized exoplanets is unknown. Here we report spectroscopic metallicities of the host stars of 226 small exoplanet candidates discovered by NASA's Kepler mission(10), including objects that are comparable in size to the terrestrial planets in the Solar System. We find that planets with radii less than four Earth radii form around host stars with a wide range of metallicities (but on average a metallicity close to that of the Sun), whereas large planets preferentially form around stars with higher metallicities. This observation suggests that terrestrial planets may be widespread in the disk of the Galaxy, with no special requirement of enhanced metallicity for their formation.

We report 25,563 radial velocity measurements for 1359 single-lined stars in the Carney-Latham sample of 1464 stars selected for high proper motion. For 171 of these, we present spectroscopic orbital solutions. We find no obvious difference between the binary characteristics in the halo and the disk populations. The observed frequency is the same, and the period distributions are consistent with the hypothesis that the two sets of binaries were drawn from the same parent population. This suggests that metallicity in general, and radiative opacities in particular, have little influence over the fragmentation process that leads to short-period binaries. All the binaries with periods shorter than 10 days have nearly circular orbits, while the binaries with periods longer than 20 days exhibit a wide range of eccentricities and a median value of 0.37. For the metal-poor high-velocity halo binaries in our sample, the transition from circular to eccentric orbits appears to occur at about 20 days, supporting the conclusion that tidal circularization on the main sequence is important for the oldest binaries in the Galaxy.

We present new, deep Hα and [S II] images of the HH 34 jet and bow shock obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope (HST), which reveal the structure of this fine HH flow with unprecedented detail. Many of the knots in the jet appear to form small working surfaces with bright [S II] cores and thin Hα filaments where the mini–bow shocks extend into the surrounding medium. In combination with earlier, short-exposure HST images we have determined very precise proper-motion vectors for the various shock structures in the outflow. The jet becomes visible within about an arcsecond of the source, where a new knot has emerged between our two epoch images; it has a space velocity of at least 300 km s-1, as derived from the proper motions and correcting for the 30° angle of the flow to the line of sight. The jet rapidly slows down to a mean space velocity of about 220 km s-1, with a standard deviation of 20 km s-1 among the jet knots. Such low internal velocities lead to weak shocks, consistent with the high [S II]/Hα ratio along the jet body and in accordance with the internal working surface model for jets. The jet motion appears to be ballistic, with no evidence for a turbulent boundary layer. The jet is well resolved and steadily expands with a half-opening angle of 04. The large HH 34 working surface shows a multitude of knots, all of which are enveloped by a series of very thin, limb-brightened Hα-emitting filaments immediately behind the shock front where the flow faces into the preshock medium. One of these filaments developed four regularly spaced tiny knots between the two epochs, possibly due to a Rayleigh-Taylor instability along the filament or caused by the presence of small, dense clumps in the ambient medium. Proper motions of the HH 34 working surface show an obvious expansion due to material being squirted sideways. In addition to the large-scale S-shaped symmetry of the giant HH 34 flow, the jet shows a marked and surprisingly abrupt change in flow direction during a 65 yr interval that ended 10 yr ago, suggesting that the jet-disk system may have been influenced by powerful tidal effects by a companion star during a recent periastron passage. A second, smaller bowlike flow, called HH 534, possibly emanates from the HH 34 source region, and if so this supports the contention that the source is a binary. This data set is a testament to the unique abilities of the HST to follow morphological, photometric, and excitation changes on cooling timescales in the shocks of flows from young stars.

We summarize the results from a program of monitoring the radial velocities of 10 metal-poor, high-velocity field stars whose colors are 0.01 to 0.13 mag bluer than main-sequence turnoffs of comparable-metallicity globular clusters. Two of the candidate halo blue stragglers (BD +72 94 and BD +40 1166) show no signs of velocity variability, one (HD 84937) shows only weak signs of variability, one (BD +25 1981) appears to be a very long-period binary, and six (BD -12 2669, HD 97916, HD 106516, BD +51 1817, G66-30, and G202-65) are single-lined spectroscopic binaries, with periods ranging from 167 to 844 days. Velocity coverage for the four candidates without orbital solutions ranges from 15.9 to 19.0 years. The orbital eccentricities are all low, e < 0.30 and e = 0.11. Five of the six binary orbits have very low eccentricities, with e = 0.07. We have reanalyzed the velocity data from Preston & Sneden and have derived orbital solutions similar to theirs for 10 of the spectroscopic binaries among their "blue metal-poor" stars with [Fe/H] ≤ -0.6. We confirm their conclusion that the binary frequency is high; we find 47 ± 10% if we include only the definite binaries with [Fe/H] ≤ -0.6. Our orbital solutions for the seven binaries with periods longer than 20 days all have low eccentricities, with e ≤ 0.26 and e = 0.11. These orbital characteristics are very similar to the Ba II, CH, subgiant CH, and dwarf carbon stars, suggesting that mass transfer has been involved in their formation. Of the five binary stars in our program with published abundances of lithium, all have been found to be deficient (and one in beryllium as well). In contrast, two of the three apparently single stars have published lithium abundances and show no deficiency. The mass functions for the six binaries in our program and seven similar systems studied by Preston & Sneden are consistent with their unseen companions all being white dwarfs with M ≈ 0.55 M⊙ and random orbital inclinations. Taking all of our observations and those of others together, we argue that the results are consistent with all field blue stragglers being binary systems with long periods and low eccentricities, the primary stars being deficient in lithium and the secondary stars being normal-mass white dwarfs. All these properties are suggestive of a blue-straggler formation model that involves mass transfer. For six of the 13 stars in the two programs for which s-process elemental abundances are available, no signs of enhancement are discernible, suggesting that the donor star was a first-ascent red giant. For the star with the longest orbital period (1307 days), CS 22956-028, s-process abundance enhancements have been reported. This star may be a precursor to the subgiant CH class, as suggested by Luck & Bond.

The young SNR Cassiopeia A was imaged with WFPC-2 through four filters selected to capture the complete velocity range of the remnant's main shell in several important emission lines. Primary lines detected were [O III] 4959,5007, [N II] 6583, [S II] 6716,6731 + [O II] 7319,7330 + [O I] 6300,6364, and [S III] 9069,9532. About 3/4th of the remnant's main shell was imaged in all four filters. Considerable detail is observed in the reverse-shocked ejecta with typical knot scale lengths of 0.2"-0.4" (1 - 2 x 10^16 cm). Both bright and faint emission features appear highly clumped. Large differences in [S III] and [O III] line intensities indicating chemical abundance differences are also seen, particularly in knots located along the bright northern limb and near the base of the northeast jet. A line of curved overlapping filament in the remnant's northwestern rim appears to mark the location of the remnant's reverse shock front in this region. Finger-like ejecta structures elsewhere suggest cases where the reverse shock front is encountering the remnant's clumped ejecta. Narrow-band [N II] images of the remnant's circumstellar knots ("QSFs") reveal them to be 0.1"-0.6" thick knots and filaments, often with diffuse edges facing away from the center of expansion. Three color composite images of the whole remnant and certain sections along with individual filter enlargements of selected regions of the bright optical shell are presented and discussed.

New Hα and [S II] images of the HH 111 jet taken with the Hubble Space Telescope reveal marked proper motions and morphological changes when compared with similar images obtained 4 years earlier. Knots in the jet, which are dominated by emission from nested bow shocks, generally move ballistically, with no evidence for turbulent motions even in regions where the emission has a complex morphology. These bow shocks sometimes overtake one another; the new images show this occurred in knot L about 80 years ago. Photometric variability, clearly visible for the first time at subarcsecond scales, can confuse ground-based measurements that require many years between epochs to detect reliable proper motions. With the exception of the bow shock L, whose wings expand laterally, the jet moves mainly along its long axis. Because HH 111 lies nearly in the plane of the sky, the proper motions translate accurately to space velocities, which range from 220 to 330 km s-1 with a typical uncertainty of ±5 km s-1. The fastest knots are associated with object E at the base of the visible jet, where a cooling layer is in the process of forming behind one of the shocks. Velocity differences between adjacent knots within the optically bright part of the jet are typically 40 km s-1, in line with predictions of nonmagnetic shock models based on emission-line fluxes. This agreement limits the component of the magnetic field perpendicular to the axis of the jet to be 1 mG.

We present proper-motion measurements of the bipolar lobes and equatorial disk features ejected from η Carinae during the last century and deduce their relative ages in order to determine the likelihood of multiple ejection events. Hubble Space Telescope Wide Field Planetary Camera 2 images taken in 1994, 1995, and 1999 were compared, and the motions of small (~1'') patches throughout the nebula were measured. Assuming that the material has not been accelerated or decelerated, the projected expansion velocities of both lobes and two equatorial features (the "Paddle" and regions in the NN Jet) indicate that the bipolar lobes and fast equatorial ejecta have the same origin date, some 150 years ago during the Great Eruption. We also conclude that the ejection of the partial shell of outer debris preceded the Great Eruption by at least several decades or possibly a century, confirming that the nebula surrounding η Car represents at least two outburst events and maybe more.

We present new optical emission-line and continuum images taken with the Hubble Space Telescope of the shocked bubble HH 168 (GGD 37) associated with the massive star formation region Cepheus A. The new images clearly resolve the interface between the molecular flow, defined by near-IR images of H2, and the shocked, optically emitting gas. The H2 emits in a clumpy sheath that surrounds the optical emission, in what appears to be a precursor or a C-type shock. This region also emits in [S II]. Hence, unlike most other Herbig-Haro (HH) regions, where [S II] radiates only behind Hα in a cooling zone, in HH 168 the [S II] emission leads Hα when H2 emission is present. The [S II] in the precursor C-shock separates spatially from the H2; hence, this region is not isothermal. H2 emission is absent and [O III] is bright near the apices of the high excitation bow shocks in the flow, as expected from theory. Radial velocities of H2 derived from high spectral resolution slit maps of the two highest excitation HH objects lie within ~30 km s-1 of the molecular cloud velocity, consistent with the precursor scenario. Some of the H2 emission in the region is redshifted and apparently unrelated to the HH 168 bubble. Additional discoveries include numerous bright pointlike Hα emission objects, some of which may be T Tauri stars, a bright jet unrelated to the bubble flow, a bumpy morphology to the bright bow shock S, and several locations where "fingers" of H2 terminate in optically visible HH emission, similar to what is seen in the Orion Nebula.

Multiepoch HST/WFPC2 images of η Carinae are used to investigate the relationship between the photometric variability of the circumstellar nebula and the variability of the central star. In the past few years, the central star has brightened considerably, and the response of the reflection nebula to this brightening has been surprisingly complex. While the central star has brightened by a factor of 2 at near-ultraviolet and optical wavelengths, bright dust condensations in the bipolar lobes have increased by only a factor of ~1.3, and dark lanes between these dust condensations have brightened by factors of 1.5–2. Certain regions of the nebula have brightened much more than the star itself (as much as a factor of 8), and others have actually faded, despite the brightening of the star. Some of the anomalous fading can be attributed to contributions of intrinsic [S III] and [N II] line emission. The variations of the equivalent width of [S III] λ6312 and [N II] λ6583 as measured in the WFPC2 F631N and F658N filters follow the same trend of other high-excitation lines observed in ground-based spectra during η Car's 5.5 yr spectroscopic cycle, and the amplitude of the change accounts for the total change measured in ground-based spectra for these same lines. The WFPC2 images indicate, however, that these high-excitation lines are emitted by circumstellar gas at distances of a few hundred to a few thousand AU from the star, probably located in the equatorial plane. Thus, periodic ionization of gas at large distances from the central star appears to dominate the spectroscopic changes that define the 5.5 yr cycle. The fact that the variable high-excitation emission is extended places important constraints on models for η Car's 5.5 yr spectroscopic variability.

We present Hubble Space Telescope (HST) Wide Field and Planetary Camera 2 images and Faint Object Spectrograph data of two young supernova remnants in the Magellanic Clouds, N132D (LMC) and 1E 0102.2-7219 (SMC). The spectra cover essentially the entire UV/optical range available to HST and provide the first true comparison of UV/optical line intensities from astrophysical shocks that do not depend on scalings from different aperture sizes or instruments. For the spectra, we isolated specific knots and filaments that contain fast-moving debris of nuclear-processed material that are devoid of hydrogen and appear to have originated from the cores of the progenitor stars. In N132D we also observed a knot on the outer rim of the remnant that represents a shocked interstellar cloud. In the debris from both remnants, we identify only the elements O, Ne, C, and Mg. We find no evidence for oxygen-burning products, such as S, Ca, Ar, etc., which are seen in Cas A and are expected from models of Type II supernovae. We suggest that the progenitor stars of N132D and 1E 0102.2-7219 had large, oxygen-rich mantles (perhaps Wolf-Rayet stars) and may be the products of Type Ib supernovae. Shock modeling demonstrates systematic differences in the relative abundances in the O-rich debris, possibly pointing to different progenitor masses for these two objects. The shocked interstellar knot in N132D shows that we are probably seeing a range of conditions within the ~1'' aperture and that no evidence is present for enrichment by a precursor star wind.

We present new velocity-resolved Fabry-Perot images in [S II] λ6731 and Hα of the blueshifted portion of the protostellar outflow L1551. These new data isolate the line emission from the reflected continuum and make it possible to visualize the kinematics of the shock waves in the outflow clearly for the first time on large scales with subarcsecond spatial resolution. Velocity images of the L1551 jet confirm that a fainter, slower jet lies a few arcseconds below the main jet. Emission from the main jet decreases sharply in radial velocity and the emission-line width increases suddenly as the jet encounters bright knot 3, in agreement with bow shock models. This knot must move into previously ejected material to account for the observed radial velocities, supporting the idea that shocks in Herbig-Haro (HH) flows form as the result of variable velocity ejections from the embedded protostar. However, a velocity gradient observed along the entire edge of the bow shock is spatially larger than expected if the bow shock alone were responsible for all the line emission. Deviations from the simple model are most easily explained if a Mach disk alters the emission and kinematics within the bow shock region, though a precursor to the bow shock is an alternate possibility. The spatial distribution of radial velocities and emission-line widths across HH 29 implies that this object is a slower portion of the outflow currently being overtaken by faster material. New proper-motion images of HH 29 independently confirm this result. The large-scale velocity structure of the L1551 outflow is complex but can generally be understood if faster material drives shock waves into slower material around the edge of a cavity. A striking circular feature whose center lies near the intersection of the axis of the bright jet and the cavity resembles similar structures in the Orion Nebula and could define a hole through which a fast jet has penetrated. The velocity structure along a string of HH objects to the southwest of HH 29 is consistent with the recent result of Devine et al. that L1551 NE drives this portion of the outflow. Linear features that cross the L1551 flow may be associated with separate, unrelated jets from the HH 30 region or elsewhere within L1551.

We present new spectra obtained with the Faint Object Spectrograph aboard the Hubble Space Telescope of the HH 47A bow shock and Mach disk that cover the entire spectral range between λλ2220 and 6810. In addition to emission lines seen previously from HH objects, we uncover over a dozen weak Fe IItransitions in the ultraviolet. The flux ratios between these permitted lines can only be understood if transitions to the ground state are resonantly scattered within HH 47A. The expected column density of Fe II within HH 47A suffices to scatter these lines, although the scattering optical depths imply that the Fe II line broadening must exceed that expected from thermal motions. Excitation of ultraviolet Fe II occurs locally within HH 47A, probably from collisions within the hot postshock gas and not from UV pumping from some nearby O stars. The data show no evidence for significant depletion of Fe within HH 47A. The emission line's fluxes and ratios indicate that jet material currently enters the Mach disk with a density of ~350 cm-3 and a velocity of ~40 km s-1. The mass-loss rate of the exciting star, as measured by the mass flux through the Mach disk, is 1.6×10 M☉ yr-1. This mass-loss rate is considerably lower than that closer to the star where the jet is brighter, probably because the density along the jet is highly nonuniform. A single-shock velocity does not match the bow shock spectrum well. We propose that secondary shocks reheat the gas within the cooling zone of the HH 47A bow shock. Compression from the first shock will cause these secondary shocks to be strongly magnetized, and the secondary shocks should emit strongly in low-excitation lines such as Mg II, C II], and [S II]. The weak blue continua seen at optical wavelengths in spectra of the Mach disk and bow shock extend into the ultraviolet and have spectral energy distributions and total fluxes consistent with those expected from two-photon emission.

Hubble Space Telescope (HST) continuum and emission-line images of η Carinae obtained with the Planetary Camera (PC) of the Wide Field Planetary Camera 2 show a startling wealth of detailed structure in the expanding Homunculus Nebula and outer debris field. Using a combination of dithering and image deconvolutions, we have achieved a resolution of about 50 mas over the ~30'' field of view covered by the PC. The complex network of bright cells and reddish, dusty lanes that lace the surfaces of the bipolar lobes of the Homunculus resemble similar structures observed in recent HST images of planetary nebulae. The contrast between these dust lanes and the adjacent bright cells, together with the dimensions of these features, is used to estimate the opacity and density of the obscuring material. Though radiation pressure is expected to accelerate the dust lanes by less than 10–20 km s-1 with respect to the 650 km s-1 expansion of the Homunculus, it may be the source of the instability responsible for their formation, and we discuss the formation of the bright cells and dusty filaments in this context. We present new data on the debris field beyond the Homunculus. This region contains a set of high-velocity "whiskers" (or "streamers") that show bipolar kinematics that associate them with the radially expanding lobes of the Homunculus and extend away from the central star like shrapnel from an explosion with trailing strings. The whiskers are several arcseconds long but often less than 01 wide, with some having length-to-width ratios exceeding 100. They are also remarkably uniform in brightness. We observe excess UV light several arcseconds northwest of the central star in the vicinity of a recent burst of radio emission. This "blue glow" appears to emanate from the equatorial region between the bipolar lobes. Though we cannot confirm temporal variability of this excess light, it may be connected with a burst of ultraviolet radiation that escaped the central region and ionized gas in this direction, perhaps generating radio-wavelength hydrogen recombination line emission. The near-ultraviolet glow in our images may be produced by fluorescent Fe II emission lines in the bandpass of the F336W filter, as seen in our recent HST Goddard High Resolution Spectrograph observations of this region.

We discuss the morphology and kinematics of the extended gas in the type 2 Seyfert galaxy NGC 5252 based on Hubble Space Telescope (HST) WFPC2 continuum and emission-line images (including a new [O III] λ5007 image) and a ground-based Fabry-Perot (F-P) velocity map of the ionized gas. The fine-scale morphology of the ionized gas in this galaxy's very extended (~40 kpc) ionization bicone consists of a complex network of filamentary strands. The new WFPC2 [O III] image also reveals more detail in the circumnuclear (~3 kpc) gas disk than is seen in the Hα + [N II] image presented previously by Tsvetanov and coworkers. The F-P velocity map shows an obvious antisymmetry of the velocity field of the ionized gas across the nucleus. We conclude that there are three dynamical components to the extended gas in NGC 5252. Two of these components are gas disks aligned with the stellar disk, one rotating with the stars and the other counterrotating. The third component is the circumnuclear gas disk seen in the HST observations and its extension to larger scales; this disk has an inclination of ~40° and a kinematic major axis in P.A. ~ 90°-135°, some 80°-125° from the major axis of the stellar disk. This simple model of two inclined rotating disks, superposed along the line of sight, describes well the seemingly complex kinematics observed in the optical emission lines and the H I 21 cm radio maps. The large misalignment between the second disk and the stellar disk suggests that the gas distribution, and possibly the nuclear activity, in NGC 5252 may have resulted from a galaxy merger event. The absence of significant radial motions, together with the well-defined ionization cones, strongly suggests that the gas is photoionized by a compact nuclear source rather than being ionized in situ by shock waves in a large-scale outflow.

Ultraviolet emission lines in supernova remnants (SNRs) provide important clues to the shock velocities, densities, grain destruction, and thermal structure of the cooling regions in these objects. However, several of the brightest ultraviolet emission lines seen in SNRs, including C II ?1335, C IV ?1550, and O VI ?1034, are resonance lines whose brightnesses will be reduced by scattering if the column density along the line of sight is sufficiently large. Scattering is particularly important in the bright filaments of SNRs because these shock waves are seen nearly edge-on. To assess the importance of resonant scattering in the UV, we have taken advantage of the enormous diffuse source sensitivity of the Hopkins Ultraviolet Telescope to observe the UV emission from a face-on shock in the Vela supernova remnant. The position chosen is seen in projection near the center of the remnant and corresponds to a bright soft X-ray region. A 165 km s-1 shock with a 30% carbon depletion matches most of the line intensities, but the weakness of the N V ?1240 line may suggest a departure from the simple shock models. We compare the spectrum of the face-on shock to that of a nearby bright filament and find some differences in shock velocity as well as in resonance-line scattering. We also derive the ram pressure of the shock from Fabry-Perot observations, and find that it greatly exceeds the thermal pressure derived from the [S II] doublet. This result strongly suggests pressure support by magnetic fields or cosmic rays.

We present Hubble Space Telescope Hα and [S II] images of HH 29. The proximity of HH 29 (140 pc) and the high resolution of the Planetary Camera has resulted in the most detailed images obtained so far of any Herbig-Haro object. The most prominent feature is a linear Hα ridge leading the working surface of a bow shock with a chaotic trailing [S II] bright region. The high-excitation ridge is perpendicular to a line extending toward the class 0 protostar L1551-NE, supporting its recent identification as the driving source. Previous studies have identified several low-velocity features within the working surface. Our images reveal them to be miniature bow shocks facing upstream. Evidently a cluster of dense quasi-stationary clumps have been overrun by a faster, lower density flow. The shock front impacted the front of the largest clump several decades ago, and during the 1990s, a prominent gap appeared in the advancing bow shock in the wake of the obstacle. The Hubble Space Telescope images show that by 1998 the shock front had wrapped around the back of the clump, closing the shock shadow it produced.

We present near and mid-infrared observations of the pulsar-wind nebula (PWN) B0540-69.3 and its associated supernova remnant made with the {\it Spitzer Space Telescope}. We report detections of the PWN with all four IRAC bands, the 24 $\mu$m band of MIPS, and the Infrared Spectrograph (IRS). We find no evidence of IR emission from the X-ray/radio shell surrounding the PWN resulting from the forward shock of the supernova blast wave. The flux of the PWN itself is dominated by synchrotron emission at shorter (IRAC) wavelengths, with a warm dust component longward of 20 $\mu$m. We show that this dust continuum can be explained by a small amount ($\sim 1-3 \times 10^{-3} \msun$) of dust at a temperature of $\sim 50-65$ K, heated by the shock wave generated by the PWN being driven into the inner edge of the ejecta. This is evidently dust synthesized in the supernova. We also report the detection of several lines in the spectrum of the PWN, and present kinematic information about the PWN as determined from these lines. Kinematics are consistent with previous optical studies of this object. Line strengths are also broadly consistent with what one expects from optical line strengths. We find that lines arise from slow ($\sim 20$ km s$^{-1}$) shocks driven into oxygen-rich clumps in the shell swept-up by an iron-nickel bubble, which have a density contrast of $\sim 100-200$ relative to the bulk of the ejecta, and that faster shocks ($\sim 250$ km s$^{-1}$) in the hydrogen envelope are required to heat dust grains to observed temperatures. We infer from estimates of heavy-element ejecta abundances that the progenitor star was likely in the range of 20-25 $M_\odot$., Comment: 46 pages, 10 figures, accepted for publication in ApJ

We present new optical emission-line images of the young SNR 1E 0102-7219 (E0102) in the SMC obtained with the HST Advanced Camera for Surveys (ACS). E0102 is a member of the oxygen-rich class of SNRs showing strong oxygen, neon , and other metal-line emissions in its optical and X-ray spectra, and an absence of H and He. The progenitor of E0102 may have been a Wolf-Rayet star that underwent considerable mass loss prior to exploding as a Type Ib/c or IIL/b SN. The ejecta in this SNR are fast-moving (V > 1000 km/s) and emit as they are compressed and heated in the reverse shock. In 2003, we obtained optical [O III], H-alpha, and continuum images with the ACS Wide Field Camera. The [O III] image captures the full velocity range of the ejecta, and shows considerable high-velocity emission projected in the middle of the SNR that was Doppler-shifted out of the narrow F502N bandpass of a previous Wide Field and Planetary Camera 2 image from 1995. Using these two epochs separated by ~8.5 years, we measure the transverse expansion of the ejecta around the outer rim in this SNR for the first time at visible wavelengths. From proper-motion measurements of 12 ejecta filaments, we estimate a mean expansion velocity for the bright ejecta of ~2000 km/s and an inferred kinematic age for the SNR of \~2050 +/- 600 years. The age we derive from HST data is about twice that inferred by Hughes et al.(2000) from X-ray data, though our 1-sigma error bars overlap. Our proper-motion age is consistent with an independent optical kinematic age derived by Eriksen et al.(2003) using spatially resolved [O III] radial-velocity data. We derive an expansion center that lies very close to X-ray and radio hotspots, which could indicate the presence of a compact remnant (neutron star or black hole)., 28 pages, 8 figures. Accepted to the Astrophysical Journal, to appear in 20 April 2006 issue. Full resolution figures are posted at: http://stevenf.asu.edu/figures

HST ACS images of the young SN remnant Cas A are used to explore the expansion and spatial distribution of its highest velocity debris. Proper motions of over 1800 outlying ejecta knots are reported. The distribution of transverse expansion velocities for these knots shows a striking bipolar asymmetry with the highest velocity knots confined to nearly opposing northeast and southwest `jets'. The jets appear kinematically and chemically distinct with respect to the remnant's highest velocity debris seen in other directions. Significant gaps in the spatial distribution of outlying ejecta lie in directions which are approximately perpendicular to the jets. Extrapolations of 9 month proper motions for all outer ejecta knots and a subsample of 72 bright and compact knots suggest explosion dates (assuming no knot deceleration) of 1662 +/- 27 and 1672 +/- 18, respectively. We find some evidence for non-uniform deceleration in different directions with knots located along the northwestern limb among the least decelerated ejecta suggesting a convergence date of 1681 +/-19. The remnant's central X-ray point source lies some $7''$ to the southeast of the estimated expansion center (PA = 169 deg) indicating a projected motion of ~350 km/s toward the middle of the broad southern outer ejecta knot gap., Comment: 13 pages, 5 figures, ApJ, in press

Hubble Space Telescope images of the young Galactic supernova remnant Cassiopeia A reveal a far larger population of outlying, high-velocity knots of ejecta with a broader range of chemical properties than previously suspected. We identify three main classes of outer ejecta: 1) Knots dominated by [N II] 6548,6583 emission; 2) Knots dominated by oxygen emission lines especially [O II] 7319,7330; and 3) Knots with emission line strengths similar to the [S II] strong FMK ejecta commonly seen in the main emission shell. The discovery of a significant population of O-rich ejecta situated in between the suspected N-rich outer photospheric layer and S-rich FMK-like ejecta suggests that the Cas A progenitor's chemical layers were not completely disrupted by the supernova explosion outside of the remnant's NE and SW high velocity `jet' regions. In addition, we find the majority of O-rich outer ejecta at projected locations out beyond (v = 6500 - 9000 km/s) the remnant's fastest moving Fe-rich X-ray emission material (6000 km/s) seen in Chandra and XMM data along the eastern limb. This suggests that penetration of Fe-rich material up through the S and Si-rich mantle did not extend past the progenitor's N or O-rich outer layers for at least this section of the remnant., 17 pages including 3 tables and 7 figures. To appear in ApJ

A second generation near-infrared instrument was built by the University of Colorado for the ARC 3.5 meter telescope and is being commissioned at the Apache Point Observatory. An initial engineering run, first light, commissioning observations, and initial facility science operations have been accomplished in the last year. Instrument imaging performance was good to excellent from first light and consortium observers began to employ the instrument on a shared-risk basis immediately after commissioning operations. Instrument optical and mechanical performance during this testing and operations phase are discussed. Detector system (Rockwell Hawaii-1RG 1024x1024 HgCdTe focal plane array with Leach controller) characteristics during these early operations are detailed along with ongoing efforts for system optimization. High resolution (R~10,000) spectroscopy is planned employing a Queensgate (now IC Optical) cryogenic Fabry-Perot etalon, though mechanical difficulties with the etalon precluded a system performance demonstration. The Consortium has decided that the instrument will retain the name NIC-FPS (Near Infrared Camera and Fabry-Perot Spectrometer) after commissioning.

We present a proper motion study of the shock waves within the classic stellar jet HH 47 based on Hubble Space Telescope H-alpha and [S II] images of the region taken over two epochs. Individual knots within the jet and in the bow shock/Mach disk working surface of HH 47A move significantly in the five years that separate the images, and the excellent spatial resolution of HST makes it possible to measure the proper motions with enough precision to easily observe differential motions throughout the flow. The bright portion of the jet emerges at 37.5 +/- 2.5 degrees from the plane of the sky with an average velocity of 300 km/s. Dynamical ages of the shock waves in the jet range from a few decades for knots recently ejected by the source to ~ 1300 years for the faint extended bow shock HH 47D. The jet curves, but motions of knots in the jet are directed radially away from the exciting source, and velocity variability in the flow drives the shock waves that heat the jet internally. The jet orientation angle varies with time by about 15 degrees, and currently points to the northwestern portion of a cavity outlined by a reflection nebula, where a quasi-stationary shock deflects the jet. The major working surface HH 47A is more complex than a simple bow shock/Mach disk, and contains numerous clumps that move relative to one another with velocities of ~ +/- 40 km/s. Small clumps or instabilities affect the Mach disk, and dense clumps may move all the way through the working surface to cause the bumpy morphology seen at the bow shock. A localized area between the bow shock and Mach disk varies significantly between the two sets of images., full resolution figures available at http://sparky.rice.edu/~hartigan/pub.html; Accepted for publication in the Astronomical Journal

To fulfill the National Aeronautic and Space Administration's some of the goals of the Origins program, we present the candidate Middle Class Explorer, ORION. ORION will image all the nearby star forming regions at high resolution at several astrophysically relevant emission lines. By imaging the nearby star forming regions ORION will answer profound questions about the origin of stars like the Sun, and therefore the planets that may contain life elsewhere in the universe. To compete with existing instruments, both in space and on the ground, we make use of new technologies and our ability to optimize the design for a single purpose.

The ORION MIDEX mission is a 1.2m UV-visual observatory orbiting at L2 that will conduct the first-ever high spatial resolution survey of a statistically significant sample of visible star-forming environments in the Solar neighborhood in emission lines and continuum. This survey will be used to characterize the star and planet forming environments within 2.5 kpc of the Sun, infer global properties and star formation histories in these regions, understand how environment influences the process of star and planet formation, and develop a classification scheme for star forming regions. Based on these findings a similar survey will be conducted of large portions of the Magellanic Clouds, extending the classification scheme to new types of regions common in external galaxies, allowing the characterization of low mass star forming environments in the Magellanic Clouds, study of the spatial distribution of star forming environments and tracing of star formation history. Finally the mission will image a sample of external galaxies out to ~5 Mpc. The distribution of star forming region type will be mapped as a function of galactic environment to infer the distribution and history of low-mass star formation over galactic scales, and characterize the stellar content and star formation history of galaxies.

The Destiny space telescope is a candidate architecture for the NASA-DOE Joint Dark Energy Mission (JDEM). This paper describes some of the scientific and observational issues that will be explored as part of our mission concept study. The Destiny ~1.8-meter near-infrared (NIR) grism-mode space telescope would gather a census of type Ia and type II supernovae (SN) over the redshift range 0.5 < z < 1.7 for measuring the expansion rate of the Universe as a function of time and characterizing the nature of dark energy. The central concept is a wide-field, all-grism NIR survey camera. Grism spectra with 2-pixel resolving power R~70-100 will provide broad-band spectrophotometry, redshifts, SN classification, as well as valuable time-resolved diagnostic data for understanding the SN explosion physics. Spectra from all objects within the 1° x 0.25° FOV will be obtained on a large HgCdTe focal plane array. Our methodology requires only a single mode of operation, a single detector technology, and a single instrument.

The Dark Energy Space Telescope (DESTINY) is a proposed approach to the Joint Dark Energy Mission (JDEM). This paper describes its current design and trades of an on-going mission concept study. The DESTINY ~1.8-meter near-infrared (NIR) grism-mode space telescope would gather a census of type Ia and type II supernovae (SN) over the redshift range 0.5

The Near-Infrared Camera and Fabry-Perot Spectrometer (NIC-FPS) will provide near-IR imaging over the wavelength range ~0.9-2.45 microns and medium resolution (R~10,000) full-field Fabry-Perot spectroscopy in the 1.5-2.4 micron range. Science observation will commence by mid 2004 on the Astrophysical Research Consortium 3.5-m telescope at the Apache Point Observatory in Sunspot, NM. NIC-FPS will allow a wide variety of extragalactic, galactic, and solar system observational programs to be conducted. NIC-FPS will support two observational modes, near-IR imaging or Fabry-Perot spectroscopy. For spectroscopy of line-emitting objects, the cryogenic Fabry-Perot etalon is inserted into the optical path to generate 3D spectral datacubes at ~30 km/s spectral resolution. For narrow to broad-band imaging, the etalon is removed from the optical path. Both modes will utilize a Rockwell Hawaii 1RG 1024 x 1024 HgCdTe detector which features low dark current, low noise and broad spectral response required for astronomical observations. The optics and detector will provide a full 4.6' × 4.6' field of view at 0.27" pixel. NIC-FPS will be mounted to the ARC telescope's Nasmyth port. NIC-FPS will significantly increase ARC's near-IR imaging and spectroscopy capabilities. We present NIC-FPS's optical design and instrument specifications.

We present optical spectra of the ionized `Outer Ejecta' of Eta Carinae that reveal differences in chemical composition at various positions. In particular, young condensations just outside the dusty Homunculus Nebula show strong nitrogen lines and little or no oxygen -- but farther away, nitrogen lines weaken and oxygen lines become stronger. The observed variations in the apparent N/O ratio may signify either that the various blobs were ejected with different abundances, or more likely, that the more distant condensations are interacting with normal-composition material. The second hypothesis is supported by various other clues involving kinematics and X-ray emission, and would suggest that Eta Car is enveloped in a ``cocoon'' deposited by previous stellar-wind mass loss. In particular, all emission features where we detect strong oxygen lines are coincident with or outside the soft X-ray shell. In either case, the observed abundance variations suggest that Eta Car's ejection of nitrogen-rich material is a recent phenomenon -- taking place in just the last few thousand years. Thus, Eta Carinae may be at a critical stage of evolution when ashes of the CNO cycle have just appeared at its surface. Finally, these spectra reveal some extremely fast nitrogen-rich material, with Doppler velocities up to 3200 km/s, and actual space velocities that may be much higher. This is the fastest material yet seen in Eta Car's nebula, but with unknown projection angles its age is uncertain., 18 pages, 5 figures, 2 tables. Accepted by ApJ, April 20 2004

Asymmetric variability in ultraviolet images of the Homunculus obtained with the Advanced Camera for Surveys/High Resolution Camera on the Hubble Space Telescope suggests that Eta Carinae is indeed a binary system. Images obtained before, during, and after the recent ``spectroscopic event'' in 2003.5 show alternating patterns of bright spots and shadows on opposite sides of the star before and after the event, providing a strong geometric argument for an azimuthally-evolving, asymmetric UV radiation field as one might predict in some binary models. The simplest interpretation of these UV images, where excess UV escapes from the secondary star in the direction away from the primary, places the major axis of the eccentric orbit roughly perpendicular to our line of sight, sharing the same equatorial plane as the Homunculus, and with apastron for the hot secondary star oriented toward the southwest of the primary. However, other orbital orientations may be allowed with more complicated geometries. Selective UV illumination of the wind and ejecta may be partly responsible for line profile variations seen in spectra. The brightness asymmetries cannot be explained plausibly with delays due to light travel time alone, so a single-star model would require a seriously asymmetric shell ejection., Comment: 8 pages, fig 1 in color, accepted by ApJ Letters