Probable igneous relations in the floor of the crater J. Herschel
Structural characteristics of floor of crater J. Herschel and possible volcanic origin
FLOOR↗
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The peculiar UV extinction of Herschel 36
The differential extinction curve of Herschel 36 was determined from International Ultraviolet Explorer data. It is quite unusual, characterized by a distinct 2200 A peak with a very low far blue end at 5 to 7 mu to the -1 power. The star appears to be an extreme member of the group Savage drew attention to, previously consisting only of theta Ori, NU Ori, sigma Sco, and rho Oph. It appears that multiple scattering effects are needed to explain the observations.
Hecht, J.↗
The peculiar extinction of Herschel 36
The extinction of Herschel 36 was measured and found to be peculiar in the same sense as that observed in Orion. Following the treatment of Mathis and Wallenhorst, this can be explained by the presence of large silicate and graphite grains than are normally found in the interstellar medium. Correcting the stellar flux for foreground extinction results in a residual extinction curve for the associated dust cloud, with an unusually small normalized extinction (less than 1.0) at 1500 A. This low UV extinction may be due to the effects of scattering by the dust cloud material.
Donn, B.↗
The peculiar extinction of Herschel 36
The extinction of Herschel 36 has been measured and been found to be peculiar in the same sense as that observed in Orion. Following the treatment of Mathis and Wallenhorst (1981), this can be explained by the presence of silicate and graphite grains that are larger than those normally found in the interstellar medium. Correcting the stellar flux for foreground extinction results in a residual extinction curve for the associated dust cloud with an unusually small normalized extinction (less than 1.0) at 1500 A. This low UV extinction may be due to the effects of scattering by the dust cloud material.
Hecht, J.↗
The ejecta deposit of the ancient basin Herschel - An example of a generally unrecognized Martian sedimentological unit
This paper discusses geomorphic features of Martian impact basins and of the basin ejecta landforms, with special attention given to the Hershel Basin (14 deg S, 230 deg W; 300-km diam) and its interior and exterior landforms. A map of geomorphic features in and around Hershel Basin is presented together with data on the basin's areal densities. It is estimated that the impact that formed Herschel Basin occurred during the Late Noachian Epoch upon an already heavily cratered Middle Noachian surface.
Edgett, K. S.↗
New information on solar activity, 1779-1818, from Sir William Herschel's unpublished notebooks
Herschel's observations are analyzed in order to determine the level of solar activity for solar cycle 5. It is concluded that solar cycle 5 may have peaked as early as 1801 based upon the average number of groups with a probable secondary maximum in 1804. Depending on the technique adopted, the peak for solar cycle 5 occurred sometime between 1801 and 1804, rather than 1805.2, as commonly assumed. Instead of a solar cycle of 17 yrs, a cycle length of 14 yrs is found. It is also found that the peak yearly mean sunspot number is only about 38 rather than 45, as deduced by Wolf (1855). A technique for making early solar observations homogeneous with modern sunspot observations is proposed.
Hoyt, Douglas V.↗
Fan Noise Control Using Herschel-quincke Resonators
The research effort proposed for this NASA NRA is mainly experimental. In addition, Virginia Tech is working in partnership with Goodrich Aerospace, Aerostructures Group for the analytical development needed to support the experimental endeavor, i.e. model development, design, and system studies. In this project, Herschel-Quincke (HQ)liner technology experiments will be performed at the NASA Glenn Active Noise Control Fan (ANCF) facility. A schematic of both inlet and aft HQ-liner systems installed in the ANCF rig as well as a picture of the Glenn facility is shown. The main goal is to simultaneously test in both the inlet and bypass duct sections. The by-pass duct will have HQ-systems in both the inner and outer duct walls. The main advantages of performing tests at the ANCF facility are that the effect of the inlet HQ-system on the by-pass HQ-system and vice versa, can be accurately determined from the in-duct modal data. Another significant advantage is that it offers the opportunity to assess (on a common basis) the proposed noise reduction concept on the ANCF rig which in the past has been used for assessing other active and passive noise reduction strategies.
Burdisso, Ricardo A.↗
The effects of aberrations (low order and quilting) on the performance of the all-composite design for the Herschel Space Observatory
The effects of specific aberrations on the optical performance of the all-composite design for the Herschel Space Observatory are examined. A review of the all-composite design for the large aperture (3.5 m) telescope that satisfies the target specifications is presented. Cryogenic experiments with carbon fiber reinforced polymer (CFRP) 2 m demonstration mirror have yielded empirical bounds on the high-and low-order spatial frequency aberrations that will be anticipated in the full 3.5 m Ritchey-Chretien telescope design. Detailed analysis is presented on the effect of the low order aberrations of the primary mirror on the system wavefront error and encircled energy. Predictable limits of correction via low order shaping of the secondary mirror are described. The impact of higher order surface errors on the encircled energy and the stray light will also be presented. Comments are made regarding the impact of the optical prescription and CRFP design on flight telescope testing.
energy↗
1400-1900 GHz local oscillators for the Herschel Space Observatory
JPL continues to develop robust planar, all solid-state sources to cover the 1414 to 1908 GHz band. These sources will be used as local oscillators to drive hot electron bolometer (HEB) heterodyne mixers on the Herschel Space Observatory to observe high resolution spectra in the interstellar medium. We report our current progress and present recent results.
Schottky diode frequency multiplier THz local osci↗
Herschel and the Molecular Universe
Over the next decade, space-based missions will open up the universe to high spatial and spectral resolution studies at infrared and submillimeter wavelengths. This will allow us to study, in much greater detail, the composition and the origin and evolution of molecules in space. Moreover, molecular transitions in these spectral ranges provide a sensitive probe of the dynamics and the physical and chemical conditions in a wide range of objects at scales ranging from budding planetary systems to galactic and extragalactic sizes. Hence, these missions provide us with the tools to study key astrophysical and astrochemical processes involved in the formation and evolution of planets, stars, and galaxies. These new missions can be expected to lead to the detection of many thousands of new spectral features. Identification, analysis and interpretation of these features in terms of the physical and chemical characteristics of the astronomical sources will require detailed astronomical modeling tools supported by laboratory measurements and theoretical studies of chemical reactions and collisional excitation rates on species of astrophysical relevance. These data will have to be made easily accessible to the scientific community through web-based data archives. In this paper, we will review the Herschel mission and its expected impact on our understanding of the molecular universe.
Tielens, A. G. G. M.↗
THz Instrumentation for the Herschel Space Observatory's Heterodyne Instrument for Far Infrared
The Heterodyne Instrument for Far Infrared (HIFI) on ESA's Herschel Space Observatory utilizes a variety of novel RF components in its five SIS receiver channels covering 480-1250 GHz and two HEB receiver channels covering 1410-1910 GHz. The local oscillator unit will be passively cooled while the focal plane unit is cooled by superfluid helium and cold helium vapors. HIFI employs W-band GaAs amplifiers, InP HEMT low noise IF amplifiers, fixed tuned broadband planar diode multipliers, high power W-bapd Isolators, and novel material systems in the SIS mixers. The National Aeronautics and Space Administration through the Jet Propulsion Laboratory is managing the development of the highest frequency (1119-1250 GHz) SIS mixers, the local oscillators oscillators for the three highest frequency receivers as well as W-band power amplifiers, high power W-band isolators, varactor diode devices for all high frequency multipliers and InP HEMT components for all the receiver channels intermediate frequency amplifiers. The NASA developed components represent a significant advancement in the available performance. This paper presents an update of the performance and the current state of development.
local oscillators↗
Astronomy from Space: The Hubble, Herschel and James Webb Space Telescopes
Space-based astronomy is going through a renaissance, with three Great Observatories currently flying: Hubble in the visible and ultraviolet, Spitzer in the infrared and Chandra in X-rays. The future looks equally bright. The final servicing mission to Hubble will take place in February 2009 and promises to make the observatory more capable than ever with two new cameras, and refurbishment that will allow it to last at least five years. The upcoming launch of the Herschel Space Telescope will open the far-infrared to explore the cool and dusty Universe. Finally, we look forward to the launch of the James Webb Space Telescope in 2013, which wil provide a successor to both Hubble and Spitzer. In this talk, the author discusses some of the highlights of scientific discovery in the last 10 years and reveals the promise to the next 10 years.
Gardner, Jonathan P.↗
Herschel-ATLAS: Dust Temperature and Redshift Distribution of SPIRE and PACS Detected Sources Using Submillimetre Colours
We present colour-colour diagrams of detected sources in the Herschel-ATLAS Science Demonstration Field from 100 to 500/microns using both PACS and SPIRE. We fit isothermal modified-blackbody spectral energy distribution (SED) models in order to extract the dust temperature of sources with counterparts in GAMA or SDSS with either a spectroscopic or a photometric redshift. For a subsample of 331 sources detected in at least three FIR bands with significance greater than 30 sigma, we find an average dust temperature of (28 plus or minus 8)K. For sources with no known redshifts, we populate the colour-colour diagram with a large number of SEDs generated with a broad range of dust temperatures and emissivity parameters and compare to colours of observed sources to establish the redshift distribution of those samples. For another subsample of 1686 sources with fluxes above 35 mJy at 350 microns and detected at 250 and 500 microns with a significance greater than 3sigma, we find an average redshift of 2.2 plus or minus 0.6.
Amblard, A.↗
The Herschel ATLAS: Evolution of the 250 Micrometer Luminosity Function Out to z = 0.5
We have determined the luminosity function of 250 micrometer-selected galaxies detected in the approximately equal to 14 deg(sup 2) science demonstration region of the Herschel-ATLAS project out to a redshift of z = 0.5. Our findings very clearly show that the luminosity function evolves steadily out to this redshift. By selecting a sub-group of sources within a fixed luminosity interval where incompleteness effects are minimal, we have measured a smooth increase in the comoving 250 micrometer luminosity density out to z = 0.2 where it is 3.6(sup +1.4) (sub -0.9) times higher than the local value.
Dye, S.↗
A Debris Disk Case Study: 49 Ceti with Herschel
Gas-poor debris disks represent a fundamentally different class of circumstellar disk than gas-rich protoplanetary disks. Their gas probably originates from the same source as the dust, i.e. planetesimal destruction, but the low gas densities make it difficult to detect. So far, Herschel has detected far-IR gas emission from one debris disk, Beta Pictoris. Here I discuss a well-known debris disk system in the GASPS survey, 49 Ceti. It serves as a case study for modeling low-density gas in optically thin disks. The dust disk appears to be spatially resolved at 70 um. Most interestingly, there appears to be a hint of ClI 158 urn emission at the roughly 2 sigma level. Preliminary modeling suggests that reconciling the sub-mm CO emission from this system with the weak or non-existent far-IR atomic lines may require an unusual chemical composition in the gas of this disk.
Roberge, Aki↗
The Herschel Multi-Tiered Extragalactic Survey: SPIRE-mm Photometric Redshifts
We investigate the potential of submm-mm and submm-mm-radio photometric red-shifts using a sample of mm-selected sources as seen at 250, 350 and 500 micrometers by the SPIRE instrument on Herschel. From a sample of 63 previously identified mm-sources with reliable radio identifications in the GOODS-N and Lockman Hole North fields 46 (73 per cent) are found to have detections in at least one SPIRE band. We explore the observed submm/mm colour evolution with redshift, finding that the colours of mm-sources are adequately described by a modified blackbody with constant optical depth Tau = (nu/nu(0))beta where beta = +1.8 and nu(0) = c/100 micrometers. We find a tight correlation between dust temperature and IR luminosity. Using a single model of the dust temperature and IR luminosity relation we derive photometric redshift estimates for the 46 SPIRE detected mm-sources. Testing against the 22 sources with known spectroscopic, or good quality optical/near-IR photometric, redshifts we find submm/mm photometric redshifts offer a redshift accuracy of |delta z|/(1+z) = 0.16 (less than |delta z| greater than = 0.51). Including constraints from the radio-far IR correlation the accuracy is improved to |delta z|/(1 + z) = 0.15 (less than |delta z| greater than = 0.45). We estimate the redshift distribution of mm-selected sources finding a significant excess at z greater than 3 when compared to 850 micrometer selected samples.
Roseboom, I. G.↗
The Infrared Properties of Sources Matched in the Wise All-Sky and Herschel ATLAS Surveys
We describe the infrared properties of sources detected over approx 36 sq deg of sky in the GAMA 15-hr equatorial field, using data from both the Herschel Astrophysical Terahertz Large-Area Survey (HATLAS) and Wide-field Infrared Survey (WISE). With 5sigma point-source depths of 34 and 0.048 mJy at 250 micron and 3.4 micron, respectively, we are able to identify 50.6% of the H-ATLAS sources in the WISE survey, corresponding to a surface density of approx 630 deg(exp -2). Approximately two-thirds of these sources have measured spectroscopic or optical/near-IR photometric redshifts of z < 1. For sources with spectroscopic redshifts at z < 0.3, we find a linear correlation between the infrared luminosity at 3.4 micron and that at 250 micron, with +/- 50% scatter over approx 1.5 orders of magnitude in luminosity, approx 10(exp 9) - 10(exp 10.5) Solar Luminosity By contrast, the matched sources without previously measured redshifts (r approx > 20.5) have 250-350 micron flux density ratios that suggest either high-redshift galaxies (z approx > 1.5) or optically faint low-redshift galaxies with unusually low temperatures (T approx < 20). Their small 3.4-250 micron flux ratios favor a high-redshift galaxy population, as only the most actively star-forming galaxies at low redshift (e.g., Arp 220) exhibit comparable flux density ratios. Furthermore, we find a relatively large AGN fraction (approx 30%) in a 12 micron flux-limited subsample of H-ATLAS sources, also consistent with there being a significant population of high-redshift sources in the no-redshift sample
Bond, Nicholas A.↗
Herschel Observations of Debris Disks from WISE
The \Vide Field Infrared Survey Explorer (WISE) has just completed a sensitive all-sky survey in photometric bands at 3.4, 4.6,12 and 22 microns. We report on a study of main sequence Hipparcos and Tycho catalog stars within 120 pc with WISE 22 micron emission in excess of photospheric levels. This warm excess emission traces material in the circumstellar region likely to host terrestrial planets and is preferentially found in young systems with ages < 1 Gyr. Nearly a hundred of the WISE new warm debris disk candidates detected among FGK stars are being observed by Herschel/PACS to characterize circumstellar dust. Preliminary results indicate 70 micron detection rates in excess of 80% for these targets, suggesting that most of these systems have both warm and cool dust in analogy to our asteroid and Kuiper belts. In this contribution, we will discuss the WISE debris disk survey and latest results from Herschel observations of these sources.
Padgett, D. L.↗