White paper on science operations

Major changes are taking place in the way astronomy gets done. There are continuing advances in observational capabilities across the frequency spectrum, involving both ground-based and space-based facilities. There is also very rapid evolution of relevant computing and data management technologies. However, although the new technologies are filtering in to the astronomy community, and astronomers are looking at their computing needs in new ways, there is little coordination or coherent policy. Furthermore, although there is great awareness of the evolving technologies in the arena of operations, much of the existing operations infrastructure is ill-suited to take advantage of them. Astronomy, especially space astronomy, has often been at the cutting edge of computer use in data reduction and image analysis, but has been somewhat removed from advanced applications in operations, which have tended to be implemented by industry rather than by the end-user scientists. The purpose of this paper is threefold. First, we briefly review the background and general status of astronomy-related computing. Second, we make recommendations in three areas: data analysis; operations (directed primarily to NASA-related activities); and issues of management and policy, believing that these must be addressed to enable technological progress and to proceed through the next decade. Finally, we recommend specific NASA-related work as part of the Astrotech-21 plans, to enable better science operations in the operations of the Great Observatories and in the lunar outpost era

HST Imaging in the Chandra Deep Field South: II. WFPC2 Observations of an X-Ray Flux-Limited Sample from the 1 Msec Chandra Catalog

We present HST/WFPC2 observations of a well-defined sample of 40 X-ray sources with X-ray fluxes above the detection threshold of the full 1 Msec Chandra Deep Field South (CDFS). The sensitivity and spatial resolution of our HST observations are sufficient to detect the optical counterparts of 37 of the X-ray sources, yielding information on their morphologies and environments. In this paper we extend the results obtained in our previous study on the 300 ks CDFS X-ray data (Schreier et al. 2001, Paper I). Specifically, we show that the optical counterparts to the X-ray sources are divided into two distinct populations: 1) an optically faint group with relatively blue colors, similar to the faint blue field galaxy population, and 2) an optically brighter group, including resolved galaxies with average colors significantly redder than the corresponding bright field galaxy population. The brighter objects comprise a wide range of types, including early and late type galaxies, starbursts, and AGN. By contrast, we show that the faint blue X-ray population are most consistent with being predominantly Type 2 AGN of low to moderate luminosity, located at higher redshifts (z ~ 1 - 2). This conclusion is supported by luminosity function models of the various classes of objects. Hence, the combination of deep X-ray data with the high spatial resolution of HST are for the first time allowing us to probe the faint end of the AGN luminosity function at cosmologically interesting redshifts.Comment: AASTEX-Latex, 25 pages, 4 postscript figures, 9 jpg figures. Accepted by the Astrophysical Journal. Full-size postscript images and figures, included in the preprint, are available from: http://www.stsci.edu/~koekemoe/papers/cdfs-hst

Unveiling the Active Nucleus of Centaurus A

We report new HST WFPC2 and NICMOS observations of the center of the nearest radio galaxy Centaurus A (NGC 5128) and discuss their implications for our understanding of the active nucleus and jet. We detect the active nucleus in the near-IR (K and H) and, for the first time, in the optical (I and V), deriving the spectral energy distribution of the nucleus from the radio to X-rays. The optical and part of the near-IR emission can be explained by the extrapolation of the X-ray power law reddened by A_V~14mag, a value consistent with other independent estimates. The 20pc-scale nuclear disk discovered by Schreier et al. (1998) is detected in the [FeII] 1.64mic line and presents a morphology similar to that observed in Pa alpha with a [FeII]/Pa alpha ratio typical of low ionization Seyfert galaxies and LINERs. NICMOS 3 Pa alpha observations in a 50"x50" circumnuclear region suggest enhanced star formation (~0.3Msun/yr) at the edges of the putative bar seen with ISO, perhaps due to shocks driven into the gas. The light profile, reconstructed from V, H and K observations, shows that Centaurus A has a core profile with a resolved break at ~4" and suggests a black--hole mass of ~10^9 Msun. A linear blue structure aligned with the radio/X-ray jet may indicate a channel of relatively low reddening in which dust has been swept away by the jet.Comment: 19 pages, 13 figures, Astrophysical Journal, in press. High quality figures available at http://www.arcetri.astro.it/~marconi/colpic.htm

HST infrared imaging polarimetry of Centaurus A: implications for the unified scheme and the existence of a mis-directed BL Lac nucleus

We report results from HST/NICMOS 2 micron imaging polarimetry of the central region of Centaurus A. In the vicinity of the nucleus we observe a complex polarization structure which we explain by a combination of scattering of nuclear light and dichroic polarization associated with the dust lane. The scattered nuclear radiation is found in an angular region which extends over ~ 70 degrees and thus it does not originate from a highly collimated beam, but is associated with more omni-directional nuclear illumination. These observations also show the presence of an unresolved, highly polarized (P = 11.1 %) nuclear source whose polarization angle PA = 148.2 degrees is perpendicular to the jet axis. We set an upper limit of 0.04'' (~0.8 pc) to its extent. The observed nuclear polarization is naturally accounted for if we are observing scattered light from an otherwise obscured nucleus provided that both the scattering region and the occulting torus are extremely compact, with an outer radius of less than ~ 1 pc. Alternatively, we might be directly seeing the infrared counterpart of the radio core, similar to those found in other low luminosity radio-galaxies observed with HST. We discuss these results in the framework of the FRI / BL Lac unifying model.Comment: 12 pages, 5 figures, accepted for publication in Ap

Sturgeon in the Sacramento–San Joaquin Watershed: New Insights to Support Conservation and Management

The goal of a day-long symposium on March 3, 2015, Sturgeon in the Sacramento–San Joaquin Watershed: New Insights to Support Conservation and Management, was to present new information about the physiology, behavior, and ecology of the green (Acipenser medirostris) and white sturgeon (Acipenser transmontanus) to help guide enhanced management and conservation efforts within the Sacramento–San Joaquin watershed. This symposium identified current unknowns and highlighted new electronic tracking technologies and physiological techniques to address these knowledge gaps. A number of presentations, each reviewing ongoing research on the two species, was followed by a round-table discussion, in which each of the participants was asked to share recommendations for future research on sturgeon in the watershed. This article presents an in-depth review of the scientific information presented at the symposium with a summary of recommendations for future research

Peering through the dust: Evidence for a supermassive Black Hole at the nucleus of Centaurus A from VLT IR spectroscopy

We used the near infrared spectrometer ISAAC at the ESO 'Very Large Telescope' to map the velocity field of Centaurus A (NGC 5128) at several position angles and locations in the central 20" of the galaxy. The high spatial resolution (~0.5") velocity fields from both ionized and molecular gas (PaBeta, [FeII], BrGamma, and H2) are not compromised by either excitation effects or obscuration. We identify three distinct kinematical systems: (i) a rotating 'nuclear disk' of ionized gas, confined to the inner 2", the counterpart of the PaAlpha feature previously revealed by HST/NICMOS imaging; (ii) a ring-like system with a ~6" inner radius detected only in H2, likely the counterpart of the 100pc-scale structure detected in CO by other authors; (iii) a normal extended component of gas rotating in the galactic potential. The nuclear disk is in keplerian rotation around a central mass concentration, dark (M/L>20 Msun/LsunK) and point-like at the spatial resolution of the data (R<0.25" ~4pc). We interpret this mass concentration as a supermassive black hole. Its dynamical mass based on the line velocities and disk inclination (i>15deg) is M=2(+3.0;-1.4) 10^8 Msun. The ring-like system is probably characterized by non-circular motions; a 'figure-of-8' pattern observed in the H2 position-velocity diagram might provide kinematical evidence for the presence of a nuclear bar.Comment: 43 pages, 19 figures, Astrophysical Journal in press, higher quality figures available at http://www.arcetri.astro.it/~marconi/pubs.htm

Limits on the Spatial Extent of AGN Measured with the Fine Guidance Sensors of the HST

Accepted for publication in the Astrophysical JournalConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal