2,326 research outputs found

    Far-infrared photometric observations of the outer planets and satellites with Herschel-PACS

    Full text link
    We present all Herschel PACS photometer observations of Mars, Saturn, Uranus, Neptune, Callisto, Ganymede, and Titan. All measurements were carefully inspected for quality problems, were reduced in a (semi-)standard way, and were calibrated. The derived flux densities are tied to the standard PACS photometer response calibration, which is based on repeated measurements of five fiducial stars. The overall absolute flux uncertainty is dominated by the estimated 5% model uncertainty of the stellar models in the PACS wavelength range between 60 and 210 micron. A comparison with the corresponding planet and satellite models shows excellent agreement for Uranus, Neptune, and Titan, well within the specified 5%. Callisto is brighter than our model predictions by about 4-8%, Ganymede by about 14-21%. We discuss possible reasons for the model offsets. The measurements of these very bright point-like sources, together with observations of stars and asteroids, show the high reliability of the PACS photometer observations and the linear behavior of the PACS bolometer source fluxes over more than four orders of magnitude (from mJy levels up to more than 1000 Jy). Our results show the great potential of using the observed solar system targets for cross-calibration purposes with other ground-based, airborne, and space-based instruments and projects. At the same time, the PACS results will lead to improved model solutions for future calibration applications.Comment: 25 pages, 11 figures, 11 table

    The far-infrared energy distributions of Seyfert and starburst galaxies in the Local Universe: ISO photometry of the 12 micron active galaxy sample

    Get PDF
    New far-infrared photometry with ISOPHOT, onboard the Infrared Space Observatory, is presented for 58 galaxies with homogeneous published data for another 32 galaxies all belonging to the 12 micron galaxy sample. In total 29 Seyfert 1's, 35 Seyfert 2's and 12 starburst galaxies, about half of the 12 micron active galaxy sample, plus 14 normal galaxies for comparison. The ISO and the IRAS data are used to define color-color diagrams and spectral energy distributions (SED). Thermal dust emission at two temperatures (one cold at 15-30K and one warm at 50-70K) can fit the 60-200 micron SED, with a dust emissivity law proportional to the inverse square of the wavelength. Seyfert 1's and Seyfert 2's are indistinguishable longward of 100 micron, while, as already seen by IRAS, the former have flatter SEDs shortward of 60 micron. A mild anti-correlation is found between the [200 - 100] color and the "60 micron excess". We infer that this is due to the fact that galaxies with a strong starburst component, and thus a strong 60 micron flux, have a steeper far-infrared turnover. In non-Seyfert galaxies, increasing the luminosity corresponds to increasing the star formation rate, that enhances the 25 and 60 micron emission. This shifts the peak emission from around 150 micron in the most quiescent spirals to shorter than 60 micron in the strongest starburst galaxies.Comment: Accepted for publication in The Astrophysical Journal AASTeX preprint with 49 pages and 20 figures Also available at http://orion.ifsi.rm.cnr.it/publ.htm

    Rotating Nuclear Rings and Extreme Starbursts in Ultraluminous Galaxies

    Full text link
    New high resolution interferometer data of 10 IR ultraluminous galaxies shows the molecular gas is in rotating nuclear rings or disks with radii 300 to 800 pc. Most of the CO flux comes from a moderate-density, warm, intercloud medium rather than self-gravitating clouds. Gas masses of ~ 5 x 10^9 Msun, 5 times lower than the standard method are derived from a model of the molecular disks. The ratio of molecular gas to dynamical mass, is M_gas/M_dyn ~ 1/6 with a maximum ratio of gas to total mass surface density of 1/3. For the galaxies VIIZw31, Arp193, and IRAS 10565+24, there is good evidence for rotating molecular rings with a central gap. In addition to the rotating rings a new class of star formation region is identified which we call an Extreme Starburst. They have a characteristic size of only 100 pc., about 10^9 Msun of gas and an IR luminosity of ~3 x 10^11 Lsun. Four extreme starbursts are identified in the 3 closest galaxies in the sample Arp220, Arp193 and Mrk273. They are the most prodigious star formation events in the local universe, each representing about 1000 times as many OB stars as 30 Doradus. In Arp220, the CO and 1.3 mm continuum maps show the two ``nuclei'' embedded in a central ring or disk and a fainter structure extending 3 kpc to the east, normal to the nuclear disk. There is no evidence that these sources really are the pre-merger nuclei. They are compact, extreme starburst regions containing 10^9 Msun of dense molecular gas and new stars, but no old stars. Most of the dust emission and HCN emission arises in the two extreme starbursts. The entire bolometric luminosity of Arp~220 comes from starbursts, not an AGN. In Mrk231, the disk geometry shows that the molecular disk cannot be heated by the AGN; the far IR luminosity of Mrk~231 is powered by a starburst, not the AGN. (Abridged)Comment: 97 pages Latex with aasms.sty, including 29 encapsulated Postscript figures. Figs 18 and 23 are GIFs. 31 figures total. Text and higher quality versions of figures available at http://sbastk.ess.sunysb.edu/www/RINGS_ESB_PREPRINT.html To be published in Ap. J., 10 Nov. 199

    Spitzer Power-law AGN Candidates in the Chandra Deep Field-North

    Get PDF
    We define a sample of 62 galaxies in the Chandra Deep Field-North whose Spitzer IRAC SEDs exhibit the characteristic power-law emission expected of luminous AGN. We study the multiwavelength properties of this sample, and compare the AGN selected in this way to those selected via other Spitzer color-color criteria. Only 55% of the power-law galaxies are detected in the X-ray catalog at exposures of >0.5 Ms, although a search for faint emission results in the detection of 85% of the power-law galaxies at the > 2.5 sigma detection level. Most of the remaining galaxies are likely to host AGN that are heavily obscured in the X-ray. Because the power-law selection requires the AGN to be energetically dominant in the near- and mid-infrared, the power-law galaxies comprise a significant fraction of the Spitzer-detected AGN population at high luminosities and redshifts. The high 24 micron detection fraction also points to a luminous population. The power-law galaxies comprise a subset of color-selected AGN candidates. A comparison with various mid-infrared color selection criteria demonstrates that while the color-selected samples contain a larger fraction of the X-ray luminous AGN, there is evidence that these selection techniques also suffer from a higher degree of contamination by star-forming galaxies in the deepest exposures. Considering only those power-law galaxies detected in the X-ray catalog, we derive an obscured fraction of 68% (2:1). Including all of the power-law galaxies suggests an obscured fraction of < 81% (4:1).Comment: Accepted for publication in the Astrophysical Journal, 27 pages, 20 figures, 5 tables, version with high-resolution figures and online-only tables available at: http://frodo.as.arizona.edu/~jdonley/powerlaw

    Age-related differences in the control of weight-shifting within the surface of support

    Get PDF
    BACKGROUND AND AIM: An important reason for falling in elderly is incorrect weight-shifting¹. In many daily life activities quick and accurate weight-shifting is needed to maintain balance, especially in situations when balance is suddenly disturbed and anticipation on the upcoming movement is difficult. Considering the deterioration in postural control in elderly², it is expected that they have more difficulties with executing these quick and accurate weight-transfers³. The present study aims to gain more insight in age-related differences in postural control strategies during a postural control task requiring weight-transfers of different amplitudes and in different directions within the surface of support METHODS: Nine healthy older adults (70.3±6.9 years) and twelve young adults (20.9±0.5 years) participated in the study. The participants performed a weight-shifting task by moving the whole body in different directions to move a cursor, representing real time COP position, towards targets of different sizes and at different distances projected on a screen. Movement time (MT) was the time between the appearance of the goal target and the moment a target switch was realized (i.e. the cursor stayed in the goal target for 0.5 second). The accuracy of the movement was quantified by Counts on Goal (CoG), that is the number of times the cursor hit the goal target before a target switch was realized and by Dwelling Time (DT), the time required to realize a target switch after the goal target was hit by the cursor for the first time. Fluency was expressed by the maximal deviation (MD) of the performed path with respect to the ideal path and the number of peaks (nP), or inflections in the performed path. RESULTS: Significant main effects of target size, target distance and age on all outcome measures were found (p<.01). With decreasing target size, increasing target distance and increasing age, MT significantly increased and fluency and accuracy significantly decreased (nP, MD, CoG and DT increased). Elderly used a slower, less accurate and less fluent weight-shifting strategy compared to younger adults with increasing task difficulty (e.g. decreasing target size and increasing target distance) as indicated by significant interaction effects of size*age and distance*age (p<.05). CONCLUSION: The results of this study provided insight in how elderly control their weight-shifting when the movement cannot be anticipatorily planned. Elderly exhibited slower and more variable movements, especially with increasing task difficulty. This weight-shifting strategy seems characterizing for an increased fall risk in elderly, since the results indicate that elderly might have more difficulties with executing an adequate (quick and accurate) adaptation to a perturbation in daily life. ¹SN Robinovitch et al. Lancet. (2013), 381(9860), 47-54. ²FB Horak. Age Ageing. (2006), 35(2), 7-11. ³V Jongman et al. Stud Health Technol Inform. (2012), 181, 93-97

    Characterizing Exoplanets in the Visible and Infrared: A Spectrometer Concept for the EChO Space Mission

    Get PDF
    Transit-spectroscopy of exoplanets is one of the key observational techniques to characterize the extrasolar planet and its atmosphere. The observational challenges of these measurements require dedicated instrumentation and only the space environment allows an undisturbed access to earth-like atmospheric features such as water or carbon-dioxide. Therefore, several exoplanet-specific space missions are currently being studied. One of them is EChO, the Exoplanet Characterization Observatory, which is part of ESA's Cosmic Vision 2015-2025 program, and which is one of four candidates for the M3 launch slot in 2024. In this paper we present the results of our assessment study of the EChO spectrometer, the only science instrument onboard this spacecraft. The instrument is a multi-channel all-reflective dispersive spectrometer, covering the wavelength range from 400 nm to 16 microns simultaneously with a moderately low spectral resolution. We illustrate how the key technical challenge of the EChO mission - the high photometric stability - influences the choice of spectrometer concept and drives fundamentally the instrument design. First performance evaluations underline the fitness of the elaborated design solution for the needs of the EChO mission.Comment: 20 pages, 8 figures, accepted for publication in the Journal of Astronomical Instrumentatio

    Dust in Spiral Galaxies: Comparing Emission and Absorption to Constrain Small-Scale and Very Cold Structures

    Get PDF
    The detailed distribution of dust in the disks of spiral galaxies is important to understanding the radiative transfer within disks, and to measuring overall dust masses if significant quantities of dust are either very opaque or very cold. We address this issue by comparing measures of dust absorption, using the galaxy-overlap technique in the optical, with measures of the dust grains' thermal emission from 50-2000 micron using ISOPHOT on board ISO and SCUBA at the JCMT. We examine three spiral galaxies projected partially in front of E/S0 galaxies --- AM1316-241, NGC 5545, and NGC 5091 (for NGC 5091 we have only optical and ISO data). Adopting an empirical exponential model for the dust distribution, we compare column densities and dust masses derived from the absorption and emission techniques. This comparison is sensitive to the amount of dust mass in small, opaque structures, which would not contribute strongly to area-weighted absorption measures, and to very cold dust, which would contribute to optical absorption but provide only a small fraction of the sub-mm emission. In AM1316-241, we find global dust masses of 2-5 x 10^7 M_solar, both techniques agreeing at the 50% level. NGC 5545 has about half this dust mass. The concordance of dust masses is well within the errors expected from our knowledge of the radial distribution of dust, and argues against any dominant part of the dust mass being so cold or opaque. The 50-2000 micron data are well fitted by modified Planck functions with an emissivity law beta=-2, at 21 +/- 2 K. We also present 12 micron ISOCAM observations of these pairs.Comparison of H-alpha and 12 micron images of NGC 5545 indicate that ISOCAM images are reliable tracers of star formation.Comment: 16 pages, 4 tables, 8 figures, in press for October Astronomical Journa

    Beyond butyrate:microbial fiber metabolism supporting colonic epithelial homeostasis

    Get PDF
    Human gut bacteria produce metabolites that support energy and carbon metabolism of colonic epithelial cells. While butyrate is commonly considered the primary fuel, it alone cannot meet all the carbon requirements for cellular synthetic functions. Glucose, delivered via circulation or microbial metabolism, serves as a universal carbon source for synthetic processes like DNA, RNA, protein, and lipid production. Detailed knowledge of epithelial carbon and energy metabolism is particularly relevant for epithelial regeneration in digestive and metabolic diseases, such as inflammatory bowel disease and type 2 diabetes. Here, we review the production and role of different colonic microbial metabolites in energy and carbon metabolism of colonocytes, also critically evaluating the common perception that butyrate is the preferred fuel.</p
    corecore