137 research outputs found
High Spatial Resolution Investigations of Microchannel Plate Imaging Properties for UV Detectors
Microchannel plate (MCP) photon counting detectors are currently being used with great success on many of the recent NASA/ESA ultraviolet (UV) astrophysics missions that make observations in the 1OO A - 1600 A range. These include HUT, the Wide Field Camera on ROSAT, EUVE, ALEXIS, ORFEUS, and SOHO. These devices have also been chosen to fly on future UV astrophysics missions such as FUSE, FUVITA, IMAGE, and both the HST STIS and Advanced Camera instruments. During the period of this award we have fabricated a dual-chamber vacuum test facility to carry out laboratory testing of detector resolution, image stability and linearity, and flat field performance to enable us to characterize the performance of MCPs and their associated read-out architectures. We have also fabricated and tested a laboratory 'test-bed' delay line detector, which can accommodate MCP's with a wide range of formats and run at high data rates, to continue our studies of MCP image fixed pattern noise, and particularly for new small pore MCP's which have recently come onto the market. These tests were mainly focussed on the assessment of cross delay-line (XDL) and double delay line (DDL) anode read-out schemes, with particular attention being focussed on flat-field and spatial resolution performance
Optical Structure and Proper-Motion Age of the Oxygen-rich Supernova Remnant 1E 0102-7219 in the Small Magellanic Cloud
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).Comment: 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/figure
Cosmic Origins (COR) Program Technology Development 2018
No abstract availabl
Single photon imaging at ultra-high resolution
Abstract We present a detection system capable of imaging both single photon/positive ion and multiple coincidence photons/positive ions with extremely high spatial resolution. In this detector the photoelectrons excited by the incoming photons are multiplied by microchannel plate(s) (MCP). The process of multiplication is spatially constrained within an MCP pore, which can be as small as 4 μm for commercially available MCPs. An electron cloud originated by a single photoelectron is then encoded by a pixellated custom analog ASIC consisting of 105 K charge sensitive pixels of 50 μm in size arranged on a hexagonal grid. Each pixel registers the charge with an accuracy o
The Star Formation Rate Function of the Local Universe
We have derived the bivariate luminosity function for the far ultraviolet
(1530Angstroms) and far infrared (60 microns). We used matched GALEX and IRAS
data, and redshifts from NED and PSC-z. We have derived a total star formation
luminosity function phi(L_{tot}), with L_{tot} = L_{FUV}+L_{FIR}. Using these,
we determined the cosmic ``star formation rate'' function and density for the
local universe. The total SFR function is fit very well by a log-normal
distribution over five decades of luminosity. We find that the bivariate
luminosity function phi(L_{FUV},L_{FIR}) shows a bimodal behavior, with L_{FIR}
tracking L_{FUV} for L_{TOT}< 10^10 L_sun, and L_{FUV} saturating at 10^10
L_sun, while L_{TOT} L_{FIR} for higher luminosities. We also calculate the SFR
density and compare it to other measurements.Comment: This paper will be published as part of the Galaxy Evolution Explorer
(GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of
papers will be available at http:/www.galex.caltech.edu/PUBLICATIONS/ after
November 22, 200
Performance results of the GALEX cross delay line detectors
We describe the performance results for the Galaxy Evolution Explorer (GALEX) far ultraviolet (FUV) and near ultraviolet (NUV) detectors. The detectors were delivered to JPL/Caltech starting in the fall of 2000 and have undergone approximately 1000 hours of pre-flight system-level testing to date. The GALEX detectors are sealed tube micro-channel plate (MCP) delay line readout detectors. They have a 65 mm diameter active area, which will be the largest format on orbit. The FUV detector has a spectral bandpass from 115 - 180 nm and the NUV detector has a bandpass from 165 - 300 nm. We report here on the performance of the detectors before and after integration into the instrument. Characteristics measured include the background count rate and distribution, gain vs. applied high voltage, spatial resolution and linearity, flat fields, and quantum efficiency
UV emission and Star Formation in Stephan's Quintet
we present the first GALEX UV images of the well known interacting group of
galaxies, Stephan's Quintet (SQ). We detect widespread UV emission throughout
the group. However, there is no consistent coincidence between UV structure and
emission in the optical, H\alpha, or HI. Excluding the foreground galaxy
NGC7320 (Sd), most of the UV emission is found in regions associated with the
two spiral members of the group, NGC7319 and NGC7318b, and the intragroup
medium starburst SQ-A. The extinction corrected UV data are analyzed to
investigate the overall star formation activity in SQ. It is found that the
total star formation rate (SFR) of SQ is 6.69+-0.65 M_\sun/yr. Among this,
1.34+-0.16 M_sun/yr is due to SQ-A. This is in excellent agreement with that
derived from extinction corrected H\alpha luminosity of SQ-A. The SFR in
regions related to NGC 7319 is 1.98+-0.58 M_\sun/yr, most of which(68%) is
contributed by the disk. The contribution from the 'young tail' is only 15%. In
the UV, the 'young tail' is more extended (~100 kpc) and shows a loop-like
structure, including the optical tail, the extragalactic HII regions recently
discovered in H\alpha, and other UV emission regions discovered for the first
time. The UV and optical colors of the 'old tail' are consistent with a single
stellar population of age t ~10^{8.5+-0.4} yrs. The UV emission associated with
NGC 7318b is found in a very large (~80 kpc) disk, with a net SFR of 3.37+-0.25
M_sun/yr. Several large UV emission regions are 30 -- 40 kpc away from the
nucleus of NGC7318b. Although both NGC7319 and NGC7318b show peculiar UV
morphology, their SFR is consistent with that of normal Sbc galaxies,
indicating that the strength of star formation activity is not enhenced by
interactions.Comment: This paper will be published as part of the Galaxy Evolution
Explorer(GALEX) Astrophysical Journal Letters Special Issue. Links to the
full set of papers will be available at
http:/www.galex.caltech.edu/PUBLICATIONS/ after November 22, 200
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