Engineering topics

Moseley, H.

Publications and source records attributed to Moseley, H..

At least 19 records

NASA NTRS2013

SEDS: The Spitzer Extended Deep Survey. Survey Design, Photometry, and Deep IRAC Source Counts

The Spitzer Extended Deep Survey (SEDS) is a very deep infrared survey within five well-known extragalactic science fields: the UKIDSS Ultra-Deep Survey, the Extended Chandra Deep Field South, COSMOS, the Hubble Deep Field North, and the Extended Groth Strip. SEDS covers a total area of 1.46 deg(exp 2) to a depth of 26 AB mag (3sigma) in both of the warm Infrared Array Camera (IRAC) bands at 3.6 and 4.5 micron. Because of its uniform depth of coverage in so many widely-separated fields, SEDS is subject to roughly 25% smaller errors due to cosmic variance than a single-field survey of the same size. SEDS was designed to detect and characterize galaxies from intermediate to high redshifts (z = 2-7) with a built-in means of assessing the impact of cosmic variance on the individual fields. Because the full SEDS depth was accumulated in at least three separate visits to each field, typically with six-month intervals between visits, SEDS also furnishes an opportunity to assess the infrared variability of faint objects. This paper describes the SEDS survey design, processing, and publicly-available data products. Deep IRAC counts for the more than 300,000 galaxies detected by SEDS are consistent with models based on known galaxy populations. Discrete IRAC sources contribute 5.6 +/- 1.0 and 4.4 +/- 0.8 nW / square m/sr at 3.6 and 4.5 micron to the diffuse cosmic infrared background (CIB). IRAC sources cannot contribute more than half of the total CIB flux estimated from DIRBE data. Barring an unexpected error in the DIRBE flux estimates, half the CIB flux must therefore come from a diffuse component.

Spitzer↗

NASA NTRS2011

The Atacama Cosmology Telescope: Cosmological Parameters from the 2008 Power Spectrum

We present cosmological parameters derived from the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz and 218 GHz over 296 deg(exp 2) with the Atacama Cosmology Telescope (ACT) during its 2008 season. ACT measures fluctuations at scales 500 < l < 10,000. We fit a model for the lensed CMB, Sunyaev-Zel'dovich (SZ), and foreground contribution to the 148 GHz and 218 GHz power spectra, including thermal and kinetic SZ, Poisson power from radio and infrared point sources, and clustered power from infrared point sources. At l = 3000, about half the power at 148 GHz comes from primary CMB after masking bright radio sources. The power from thermal and kinetic SZ is estimated to be Beta(sub 3000) is identical to 6.8 +/- 2.9 mu K (exp 2), where Beta (sub l) is identical to l(l + 1) C(sub l)/2pi. The IR Poisson power at 148 GHz is Bewta(sub 3000) 7.8 +/- 0.7 muK(exp 2) (C(sub l) = 5.5 +/- 0.5 nK(exp 2)), and a clustered IR component is required with Beta (sub 3000) = 4.6 +/- 0.9 muK(exp 2), assuming an analytic model for its power spectrum shape. At 218 GHz only about 15% of the power, approximately 27 mu K(exp 2), is CMB anisotropy at l = 3000. The remaining 85% is attributed to IR sources (approximately 50% Poisson and 35% clustered), with spectral index alpha = 3.69 +/- 0.14 for flux scaling as S(nu) varies as nu(sup alpha). We estimate primary cosmological parameters from the less contaminated 148 GHz spectrum, marginalizing over SZ and source power. The ACDM cosmological model is a good fit to the data (chi square/dof = 29/46), and ACDM parameters estimated from ACT+Wilkinson Microwave Anisotropy Probe (WMAP) are consistent with the seven-year WMAP limits, with scale invariant n(sub s) = 1 excluded at 99.7% confidence level (CL) (3 sigma). A model with no CMB lensing is disfavored at 2.8 sigma. By measuring the third to seventh acoustic peaks, and probing the Silk damping regime, the ACT data improve limits on cosmological parameters that affect the small-scale CMB power. The ACT data combined with WMAP give a 6 sigma detection of primordial helium, with Y(sub p) = 0.313 +/- 0.044, and a 4 sigma detection of relativistic species, assumed to be neutrinos, with N(sub eff) = 5.3 +/- 1.3 (4.6 +/- 0.8 with BAO+H(sub 0) data). From the CMB alone the running of the spectral index is constrained to be d(sub s) / d ln k = -0,034 +/- 0,018, the limit on the tensor-to-scalar ratio is r < 0,25 (95% CL), and the possible contribution of Nambu cosmic strings to the power spectrum is constrained to string tension G(sub mu) < 1.6 x 10(exp -7) (95% CL),

Dunkley, J.↗

NASA NTRS2011

Mu-Spec - A High Performance Ultra-Compact Photon Counting spectrometer for Space Submillimeter Astronomy

We have designed and are testing elements of a fully integrated submillimeter spectrometer based on superconducting microstrip technology. The instrument can offer resolving power R approximately 1500, and its high frequency cutoff is set by the gap of available high performance superconductors. All functions of the spectrometer are integrated - light is coupled to the microstrip circuit with a planar antenna, the spectra discrimination is achieved using a synthetic grating, orders are separated using planar filter, and detected using photon counting MKID detector. This spectrometer promises to revolutionize submillimeter spectroscopy from space. It replaces instruments with the scale of 1m with a spectrometer on a 10 cm Si wafer. The reduction in mass and volume promises a much higher performance system within available resource in a space mission. We will describe the system and the performance of the components that have been fabricated and tested.

Moseley, H.↗

NASA NTRS2010

The Atacama Cosmology Telescope: A Measurement of the 600 less than l less than 8000 Cosmic Microwave Background Power Spectrum at 148 GHz

We present a measurement of the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz. The measurement uses maps with 1.4' angular resolution made with data from the Atacama Cosmology Telescope (ACT). The observations cover 228 deg(sup 2) of the southern sky, in a 4 deg. 2-wide strip centered on declination 53 deg. South. The CMB at arc minute angular scales is particularly sensitive to the Silk damping scale, to the Sunyaev-Zel'dovich (SZ) effect from galaxy dusters, and to emission by radio sources and dusty galaxies. After masking the 108 brightest point sources in our maps, we estimate the power spectrum between 600 less than l less than 8000 using the adaptive multi-taper method to minimize spectral leakage and maximize use of the full data set. Our absolute calibration is based on observations of Uranus. To verify the calibration and test the fidelity of our map at large angular scales, we cross-correlate the ACT map to the WMAP map and recover the WMAP power spectrum from 250 less than l less than 1150. The power beyond the Silk damping tail of the CMB (l approximately 5000) is consistent with models of the emission from point sources. We quantify the contribution of SZ clusters to the power spectrum by fitting to a model normalized to sigma 8 = 0.8. We constrain the model's amplitude A(sub sz) less than 1.63 (95% CL). If interpreted as a measurement of as, this implies sigma (sup SZ) (sub 8) less than 0.86 (95% CL) given our SZ model. A fit of ACT and WMAP five-year data jointly to a 6-parameter ACDM model plus point sources and the SZ effect is consistent with these results.

Fowler, J. W.↗

NASA NTRS2010

Implications of a High Angular Resolution Image of the Sunyaev-Zel'Dovich Effect in RXJ1347-1145

The most X-ray luminous cluster known, RXJ1347-1145 (z = 0.45), has been the object of extensive study across the electromagnetic spectrum. We have imaged the Sunyaev-Zel'dovich effect (SZE) at 90 GHz (lambda = 33 mm) in RXJ1347-1145 at 10" resolution with the 64 pixel MUSTANG bolometer array on the Green Bank Telescope, confirming a previously reported strong, localized enhancement of the SZE 20" to the southeast of the center of X-ray emission. This enhancement of the SZE has been interpreted as shock-heated (>20keV) gas caused by an ongoing major (low mass ratio) merger event. Our data support this interpretation. We also detect a pronounced asymmetry in the projected cluster pressure profile, with the pressure just east of the cluster core approx. 1.6x higher than just to the west. This is the highest resolution image of the SZE made to date.

Mason, B. S.↗

NASA NTRS2010

Detection of Shock-Heated Gas Using the Sz Effect in Rxj 1347-1145

Using the MUSTANG 3.3 mm bolometer array on the GBT we have measured the Sunyaev-Zel'dovich Effect (SZE) in the most x-ray luminous cluster known, RXJ 1 347-1145 (z=0.45) at a resolution of 10" (fwhm). This is the highest resolution image of the SZE to date and confirms previous indications of a localized departure from pressure equilibrium in the form of a small, very hot (>0 keV) parcel of gas, presumably resulting from a merger shock. We discuss the measurements, their interpretation, and future work.

Mason, Brian S.↗

NASA NTRS2009

Observations of M87 and Hydra A at 90 GHz

This paper presents new observations of the AGNs M87 and Hydra A at 90 GHz made with the MUSTANG bolometer array on the Green Bank Telescope at 8.5" resolution. A spectral analysis is performed combining this new data and archival VLA data or1 these objects at longer wavelengths. This analysis can detect variations in spectral index and curvature expected from energy losses in the radiating particles. L187 shows only weak evidence for steepening of the spectrum along the jet suggesting either re-acceleration of the relativistic particles in the jet or insufficient los~esto affect the spectrum at 90 GHz The jets in Hydra A show strong steepening as they move from the nucleus suggesting unbalanced losses of the higher energy relativistic particles The difference between these two sources may be accounted for by the different lengths over which the jets are observable, 2 kpc for 5187 and 45 kpc for Hydra A. Subject headings: galaxies: jets, galaxies: active, radio continuum, galaxies: individual (M87. Hydra A),

Cotton, W. D.↗

NASA NTRS2005

Submillimeter Spectroscopy with SOFIA

Four submillimeter spectrometers are being developed for use on SOFIA, the Stratospheric Observatory for Infrared Astronomy. They will be nearly diffraction limited by SOFIA'S 2.5 m telescope, giving for example images of 8.5 arc seconds FWHM at 100 microns. The instruments are FlFI LS, an integral-field imaging grating spectrometer (MPE) covering 40-210 microns with ~150 km/s resolution; SAFIRE an imaging Fabry-Perot spectrometer covering 100-'650 microns with resolution ~200 km/s, and two heterodyne receivers with resolving powers up to ~0.03 km/s: GREAT covering bands from 158-187 um, 110-125, and 62-65 microns, and CASIMIR, operating from 150-264 and 508-588 microns. These instruments will enable a variety of studies including topics relating to the origins of stars, planets, and biogenic materials in the interstallar medium of our own and other galaxies. Opportunities for observing with these and the other SOFIA instruments will be available to general investigators. SOFIA is a joint project of NASA in the U.S. and DLR in Germany.

Erickson, E.↗

NASA NTRS1991

Report of the direct infrared sensors panel

The direct infrared sensors panel considered a wide range of options for technologies relevant to the science goals of the Astrotech 21 mission set. Among the technologies assessed are: large format arrays; photon counting detectors; higher temperature 1 to 10 micro-m arrays; impurity band conduction (IBC) or blocked impurity band (BIB) detectors; readout electronics; and adapting the Space Infrared Telescope Facility and Hubble Space Telescope. Detailed development plans were presented for each of these technology areas.

Mccreight, Craig↗

NASA NTRS1991

Upcoming planetary missions and the applicability of high temperature superconductor bolometers

Planetary missions to Mars and beyond can last 11 years and longer, making impractical the use of stored cryogens. Passive radiative coolers and single-stage mechanical coolers remain possibilities. Cassini and Comet Rendezvous/Asteroid Fly-by (CRAF), both using the newly developed Mariner Mark 2 spacecraft, will be the next outer planet missions after Galileo; they are intended to provide information on the origin and evolution of the solar system. CRAF is slated for a 1994 launch. Cassini was chosen by ESA and will be launched by a Titan 4/Centaur in 1996. It will fly by Jupiter in 2000, inject an ESA-supplied probe into Titan in 2002, and take data in Saturn's orbit from 2002 to 2006. NASA/Goddard is currently developing a prototype Fourier transform spectrometer, the Composite Infrared Spectrometer (CIRS), for the Cassini mission. The baseline infrared detectors for CIRS are HgCdTe to 16 microns and Schwarz-type thermopiles from 16 to 1000 microns. The far infrared focal plane could be switched from thermopiles to high temperature superconductor (HTS) bolometers between now and 1996. An HTS bolometer could be built using the kinetic inductance effect, or the sharp resistance change at the transition. The transition-edge bolometer is more straightforward to implement, and initial efforts at NASA/Goddard are directed to that device. A working device was made and tested in early 1989. It also has somewhat elevated noise levels below 100 Hz. Upcoming efforts will center on reducing the time constant of the HTS bolometer by attempting to deposit an HTS film on a diamond substrate, and by thinning SrTiO3 substrates. Attempts will be made to improve the film quality to reduce the 1/4 noise level, and to improve the thermal isolation to increase the bolometer sensitivity. An attempt is being made to deposit good-quality HTS films on diamond films using a metal-organic chemical vapor deposition (MOCVD) technique.

Brasunas, J.↗

NASA NTRS1990

Upcoming planetary missions and the applicability of high temperature superconductor bolometers

Planetary missions to Mars and beyond can last 11 years and longer, making impractical the use of stored cryogens. Passive radiative coolers and single-stage mechanical coolers remain possibilities. CRAF and CASSINI, both using the newly developed Mariner Mark 2 spacecraft, will be the next outer planet missions after Galileo; they are intended to provide information on the origin and evolution of the solar system. CRAF is a cometary rendezvous mission slated for a 1994 launch. CASSINI has been chosen by ESA and will be launched by a Titan 4/Centaur in 1996. It will fly by Jupiter in 2000, inject an ESA-supplied probe into Titan in 2002, and take data in Saturn orbit from 2002 to 2006. NASA/Goddard is currently developing a prototype Fourier transform spectrometer (CIRS) that will be proposed for the CASSINI mission. The baseline infrared detectors for CIRS are HgCdTe to 16 microns and Schwarz-type thermopiles from 16 to 1000 microns. The far infrared focal plane could be switched from thermopiles to high temperature superconductor (HTS) bolometers between now and 1996. An HTS bolometer could be built using the kinetic inductance effect, or the sharp resistance change at the transition. The transition-edge bolometer is more straightforward to implement and initial efforts at NASA/Goddard are directed to that device. A working device was made and tested in early 1989. It also has somewhat elevated noise levels below 100 Hz. Upcoming efforts will center on reducing the time constant of the HTS bolometer by attempting to deposit an HTS film on a diamond substrate, and by thinning SrTiO3 substrates. Attempts will be made to improve the film quality to reduce th 1/f noise level, and to improve the thermal isolation to increase the bolometer sensitivity. An attempt is being made to deposit good-quality HTS films on diamond films using an MOCVD technique.

Brasunas, J.↗

NASA NTRS1990

Multiwavelength observations of two B-star nurseries - DR 15 and DR 20

New observations of DR 15 and 20 are reported as part of a study of compact H II regions in the Cyg X region. The radio and FIR data for these objects, when combined with (C-12)O maps, IRAS imagery, and optical photographs, provide new insights into the structure of this complex region and the nature of the star-formation process there. The observations show that DR 15 may consist of one or two B0 ZAMS stars whose H I regions have formed a low-density cavity within a molecular cloud. DR 20 appears to be a young OB cluster. The cluster is dominated by an O5.5 ZAMS star and also contains an approximately 3500-yr-old B0 star appearing as a compact H II region, along with weak FIR sources that may be B0-star candidates.

Odenwald, S. F.↗

NASA NTRS1990

Upcoming planetary missions and the applicability of high temperature superconductor bolometers

Past and present planetary exploration is briefly reviewed, and the planned 1996 Cassini mission to Saturn and Titan is examined. The CIRS experiment aboard Cassini, which will retrieve information on the atmospheres of Titan and Saturn, is discussed. Ongoing efforts to build a high-sensitivity, high-Tc bolometer that would greatly improve detection in Titan's atmosphere are addressed.

Brasunas, J.↗

NASA NTRS1990

Observing soft X-ray line emission from the interstellar medium with X-ray calorimeter on a sounding rocket

For an X-ray calorimeter working at 0.1 K, the energy resolution ideally can be as good as one eV for a practical detector. A detector with a resolution of 17 eV FWHM at 6 keV has been constructed. It is expected that this can be improved by a factor of two or more. With X-ray calorimeters flown on a sounding rocket, it should be possible to observe soft X-ray line emission from the interstellar medium over the energy range 0.07 to 1 keV. Here, a preliminary design for an X-ray calorimeter rocket experiment and the spectrum which might be observed from an equilibrium plasma are presented. For later X-ray calorimeter sounding rocket experiments, it is planned to add an aluminum foil mirror with collecting area of about 400 sq cm to observe line features from bright supernova remnants.

Zhang, J.↗

NASA NTRS1986

Spectral characteristics of dust in carbon rich objects

Some carbon-rich objects exhibit a strong broad emission feature beginning at lambda is approximately 24 microns and extending to lambda is greater than 30 microns. A 20 to 65 microm spectrum of the carbon star IRC+10216 and 30 to 50 micron spectra of three carbon-rich planetary nebulae, IC 418, NGC 6572, and BD+30 degrees 3639 are presented. The strong emission feature around 30 microns is seen clearly in IRC+10216, IC 418, and NGC 6572. The role of silicon carbides and magnesium sulfur particles in this feature is discussed.

Silverberg, R. F.↗

NASA NTRS1986

Far-infrared and radio observations of DR 6, DR 7, and DR 22

Far-infrared maps are presented for three young H II regions in the Cygnus X region. DR 6 and 7 were mapped in the wavelength band from 40 to 250 microns at 1 arcmin resolution, while DR 22 was mapped in the same band and also at 100-250 microns, providing dust temperature and optical depth information. New VLA maps of these sources are also presented. It is concluded that DR 6 and 7 are powered by clusters of late O or early B type stars, with ages 100,000 yr or less, while DR 22 appears to be produced by a single O6 ZAMS star. Existing (C-12)O maps suggest that the formation of these objects occurred near the edges of molecular clouds.

Odenwald, S.↗

NASA NTRS1986

Characterization of NTD germanium and ion-implanted Si bolometers at 0.3K and 0.1K

Bolometer elements were built and tested using NTD germanium and ion-implanted Si thermometer elements. The thermal links were made using aluminum wires and NbC(x)N(y) coated carbon fibers. The temperature dependence of the detector resistance, lead thermal conductivity, and heat capacity were measured. The dependence of the detector resistance on applied electric field was also measured. This, combined with the current-voltage curve for the detector, allowed the calculation of the detector responsivity. Known amounts of energy were deposited into the detector by allowing X-rays from the decay of Fe-55 to be thermalized in the detector. In the best-measured case, the predicted pulse height/measured height was 1.04 + or - .05. The noise at frequencies above 25 Hz in the NTD Ge was near that predicted by thermodynamics. The noise below 25 Hz has a 1/f character and may be in the carbon fiber/bolometer junction. The implanted detectors show some 1/f noise which depends on the total thermometer volume. Comparison between noise measurements and theory will be presented.

Moseley, H.↗

NASA NTRS1986

Spectral characteristics of dust in planetary nebulae

Some carbon-rich planetary nebulae exhibit a strong broad emission feature beginning at Lambda which is approximately 24 microns and extending to Lambda greater than 30 microns. Thirty to 55 micron spectrophotometry of Ic 418 and NGC 6572, both of which have the strong broad emission feature, allow the wavelength dependence of the emissivity of the dust responsible for the feature to be defined. Comparison with laboratory spectra of candidate materials which are likely to condense in a carbon-rich environment suggests that the feature arises from MgS. The implications of such a strong feature arising from a relatively minor dust constituent are discussed. The environment in which MgS may be found is considered. It is speculated that MgS will be seen in objects with C/O ratios only slightly greater than one, but not in extremely carbon rich objects. In objects with much higher carbon abundances, the formation of CS consumes S so that insufficient MgS can form to exhibit the strong feature. These observations imply that the emergent far infrared spectrum of carbon-rich objects are very different depending on the abundance of the low temperature condensate MgS.

Moseley, H.↗