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NASA NTRS1987

The spatial distribution of dwarf galaxies in the CfA slice of the universe

A complete (with the the exception of one) redshift sample of 58 galaxies in the Nilson catalog classified as dwarf, irregular, or Magellanic irregular is used to investigate the large-scale clustering properties of these low-surface brightness galaxies in the CfA slice of the universe (alpha in the range of 8-17 h, delta in the range of 26.5-32.5 deg). It is found that the low-surface brightness dwarf galaxies also lie on the structures delineated by the high-surface brightness normal galaxies and that they do not fill in the voids. This is inconsistent with a class of biased galaxy formation theories which predict that dwarf galaxies should be present everywhere, including the voids.

Thuan, Trinh X.↗
NASA NTRS1990

Are bars essential for starbursts in non-interacting galaxies

Analyzed here are the 1.6 and 2.2 micron images of a sample of galaxies that are classified as unbarred by the Revised Shapley-Ames Catalog. These galaxies have characteristic properties of nuclear starbursts and are examined through near infrared imaging in a search for hidden bars. Researchers selected a sample of 36 galaxies from the Revised Shapley-Ames Catalog that have far infrared luminosities greater than 10(exp 10) solar luminosity and hot Infrared Astronomy Satellite (IRAS) colors between 60 and 100 microns, indicative of nuclear starbursts, but are not classified as Seyfert 1 or 2. Their determination of the presence of a bar relies primarily on an analysis of the 2 micron image using the Galaxy Surface Photometry (GASP) package (Cawson, 1983). The GASP analysis programs determine the galaxy surface brightness and ellipticity profiles as well as the position angle and the center coordinates of the ellipses. To test the way that GASP will characterize the surface brightness of barred galaxies, two galaxies with known bars, NGC 1068 and NGC 2523, were imaged with the 2 micron camera and analyzed with GASP. Fifteen of the sample that are not clearly barred from optical data and are isolated were imaged at 1.6 and 2.2 microns; 9 of these do not appear to have bars. Strong bars therefore do not appear to be an absolute requirement for high infrared luminosity in isolated galaxies.

Pompea, Stephen M.↗
NASA NTRS1995

Repeating sources of classical gamma-ray bursts

From an analysis of the first catalog of the Burst and Transient Source Experiment (BATSE) experiment (Fishman et al. 1993, 1994a) on the Compton Gamma Ray Observatory (CGRO), we find an excessive number of pairs of gamma-ray bursts which are clustered in both a space and time . The angular separation between the two bursts in each pair is less than their positional uncertainties, and the interval between their occurrence times is within several days. Optimizing the signal, we find that the probability of observing such a clustered excess froma Poisson ensemble is approximately 2 x 10(exp -5). We suggest that these bursts arise from repeating sources. A detailed study of the most prolific source, GBS 0855-00, is presented in a separate paper (Wang & Lingenfelter 1993a, b). Unlike most of the 'soft' gamma-ray repeaters, these repeating bursts have relatively hard spectra, complex light curves, and widely varying durations, that are indistinguishable from classical gamma-ray bursts. Although the significance of the clustered excess was optimized a posteriori, because it depends on temporal and spatial bin sized that could not be defined a priori, we can use the optimizations from the first catalog to test subsequent BATSE data sets. Unfortunately, the failure of the on-board tape recorders during the second catalog period seriously reduced the number of accurately positioned bursts (Fishman et al. 1994b), so that we can neither confirm, nor refute, the predicted repitition in that sample, and we must await the results of the third catalog.

Wang, V. C.↗
NASA NTRS1997

Cosmic Dust Catalog: Particles from Collectors L2036 and L2021 - Volume 15

Since May 1981, the National Aeronautics and Space Administration (NASA) has used aircraft to collect cosmic dust (CD) particles from Earth's stratosphere. Specially designed dust collectors are prepared for flight and processed after flight in an ultraclean (Class-100) laboratory constructed for this purpose at the Lyndon B. Johnson Space Center (JSC) in Houston, Texas. Particles are individually retrieved from the collectors, examined and cataloged, and then made available to the scientific community for research. Cosmic dust thereby joins lunar samples and meteorites as an additional source of extraterrestrial materials for scientific study. This catalog summarizes preliminary observations on 468 particles retrieved from collection surfaces L2021 and L2036. These surfaces were flat plate Large Area Collectors (with a 300 cm2 surface area each) which was coated with silicone oil (dimethyl siloxane) and then flown aboard a NASA ER-2 aircraft during a series of flights that were made during January and February of 1994 (L2021) and June 7 through July 5 of 1994 (L2036). Collector L2021 was flown across the entire southern margin of the US (California to Florida), and collector L2036 was flown from California to Wallops Island, VA and on to New England. These collectors were installed in a specially constructed wing pylon which ensured that the necessary level of cleanliness was maintained between periods of active sampling. During successive periods of high altitude (20 km) cruise, the collectors were exposed in the stratosphere by barometric controls and then retracted into sealed storage container-s prior to descent. In this manner, a total of 35.8 hours of stratospheric exposure was accumulated for collector L2021, and 26 hours for collector L2036.

Warren, J.↗
NASA NTRS2013

The Interplanetary Network Supplement to the Fermi Gbm Catalog of Cosmic Gamma-Ray Bursts

We present Interplanetary Network (IPN) data for the gamma-ray bursts in the first Fermi Gamma-Ray BurstMonitor (GBM) catalog. Of the 491 bursts in that catalog, covering 2008 July 12 to 2010 July 11, 427 wereobserved by at least one other instrument in the nine-spacecraft IPN. Of the 427, the localizations of 149 could beimproved by arrival time analysis (or triangulation). For any given burst observed by the GBM and one otherdistant spacecraft, triangulation gives an annulus of possible arrival directions whose half-width varies betweenabout 0. 4 and 32, depending on the intensity, time history, and arrival direction of the burst, as well as the distancebetween the spacecraft. We find that the IPN localizations intersect the 1 GBM error circles in only 52 of thecases, if no systematic uncertainty is assumed for the latter. If a 6 systematic uncertainty is assumed and added inquadrature, the two localization samples agree about 87 of the time, as would be expected. If we then multiply theresulting error radii by a factor of three, the two samples agree in slightly over 98 of the cases, providing a goodestimate of the GBM 3 error radius. The IPN 3 error boxes have areas between about 1 arcmin2 and 110 deg2,and are, on the average, a factor of 180 smaller than the corresponding GBM localizations. We identify two burstsin the IPNGBM sample that did not appear in the GBM catalog. In one case, the GBM triggered on a terrestrialgamma flash, and in the other, its origin was given as uncertain. We also discuss the sensitivity and calibration ofthe IPN.

INTERPLANET↗
NASA NTRS1993

H1 in RSA galaxies

The original Revised Shapley-Ames (RSA) galaxy sample of almost 1300 galaxies has been augmented with further bright galaxies from the RSA appendix as well as newer galaxy catalogs. A complete and homogeneous, strictly magnitude-limited all-sky sample of 2345 galaxies brighter than 13.4 in apparent blue magnitude was formed. New 21 cm H1 line observations for more than 600 RSA galaxies have been combined with all previously available H1 data from the literature. This new extentise data act allows detailed tests of widely accepted 'standard' reduction and analysis techniques.

Richter, OTTO-G.↗
NASA NTRS2004

The Burst and Transient Source Experiment (BATSE) Earth Occultation Catalog of Low-Energy Gamma-Ray Sources

The Burst and Transient Source Experiment (BATSE), aboard the Compton Gamma Ray Observatory (CGRO), provided a record of the low-energy gamma-ray sky (approx. 20-1000 keV) between 1991 April and 2000 May (9.1 yr). BATSE monitored the high-energy sky using the Earth occultation technique (EOT) for point sources whose emission extended for times on the order of the CGRO orbital period (approx. 92 min) or greater. Using the EOT to extract flux information, a catalog of sources using data from the BATSE Large Area Detectors has been prepared. The first part of the catalog consists of results from the all-sky monitoring of 58 sources, mostly Galactic, with intrinsic variability on timescales of hours to years. For these sources, we have included tables of flux and spectral data, and outburst times for transients. Light curves (or flux histories) have been placed on the World Wide Web. We then performed a deep sampling of these 58 objects, plus a selection of 121 more objects, combining data from the entire 9.1 yr BATSE data set. Source types considered were primarily accreting binaries, but a small number of representative active galaxies, X-ray-emitting stars, and supernova remnants were also included. The sample represents a compilation of sources monitored and/or discovered with BATSE and other high-energy instruments between 1991 and 2000, known sources taken from the HEAO 1 A-4 and Macomb & Gehrels catalogs. The deep sample results include definite detections of 83 objects and possible detections of 36 additional objects. The definite detections spanned three classes of sources: accreting black hole and neutron star binaries, active galaxies, and Supernova remnants. The average fluxes measured for the fourth class, the X-ray emitting stars, were below the confidence limit for definite detection.

Harmon, B. A.↗
NASA NTRS1994

Deep VLA imaging of twelve extended 3CR quasars

A representative sample of 12 extended quasars from the 3CR catalog has been imaged at 4.9 GHz using the Very Large Array (VLA). These full synthesis observations typically achieve an rms noise of 20 micro-Jy per beam. Jets are detected on at least one side of every source. The jets are well collimated compared with those in less powerfull sources, but spreading is detected in most of them. The opening angles of several jets are not constant, but show recollimation after an initial regime of rapid spreading. Many of the jets contain quasiperiodic strings of knots, of which the knot closest to the central feature is usually the brightest (until the jet nears its hot spot). The degrees of linear polarization at the jet knots range from less than 5% to approx. 50%, but show no common trend with distance along the jets. In knots that are elongated in directions close to that of the jet, the E vectors tend to be orthogonal to the jet axis. The prominence of the inner, straighter jet segments relative to the extended lobes correlates significantly with the prominence of the milliarcsecond-scale central features, but the prominence of the more bent jet segments does not. Candidates for counterjet emission are detected in seven sources, but there is no unambiguous, continuous counterjet in any of them. Estimates of the flux density ratios between the straighter jet segments and the counterjets based on these tentative detections range from 1.2:1 to greater than 175:1. There is no evidence in this sample that counterjet detectability correlates with such putative inclination indicators as central feature prominence or projected linear size. There is also no evidence that the prominence of the counterjets anticorrelates with that of the jets as predicted by simple relativistic-beaming models for the jet/counterjet asymmetry. There is, however, strong evidence that large bends in the main jet favor counterjet detection, and there are no counterjet candidates opposite long, uninterrupted straight segments of the main jets. The detectability of the counterjets in these quasars may therefore be strongly influenced by interactions between the underlying beams and inhomogeneities in the surrounding material. We offer a new empirical definition of the term 'hot spot' that is intended to improve the distinction between such features and 'jet knots.' Both the compactness of hot spots and their position in the lobe are affected by whether they are fed by a detectable jet. When the hot spots differ significantly in compactness, the more compact one is always on the jetted side. Jetted hot spots are also more likely to be recessed deeply from the outer edge of their lobes than are their counterjetted counterparts. The jetted hot spot is less prominent relative to other extended emission if the jet bends through a large angle, particularly if a large bend occurs abruptly. The counterjetted hot spot is also less well defined if the jet is more bent. The lobes of several sources show considerable inhomogeneity, including filamentation.

Bridle, Alan H.↗
NASA NTRS2015

Genesis Solar Wind Samples: Update of Availability

The Genesis mission collected solar wind atoms for 28 months with a variety of collectors. The array wafer collector availability is displayed in the online catalog. The purpose of this report is to update the community on availability of array wafer samples and to preview other collectors which are in the process of being added to the online catalog. A total of fifteen pure materials were selected based on engineering and science requirements. Most of the materials were semiconductor wafers which were mounted on the arrays.

Gonzalez, C. P.↗
NASA NTRS2003

The Burst and Transient Source Experiment(BATSE)Earth Occultation Catalog of Low-Energy Gamma-Ray Sources. Short title: BATSE Earth Occultation Catalog v2.0

The Burst and Transient Source Experiment (BATSE), aboard the Compton Gamma Ray Observatory (CGRO), provided a record of the low-energy gamma-ray sky (approx. 20-1000 keV) between 1991 April and 2000 May (9.1y). BATSE monitored the high energy sky using the Earth occultation technique (EOT) for point sources whose emission extended for times on the order of the CGRO orbital period (approx. 92m) or greater. Using the EOT to extract flux - 2 - information, a catalog of sources using data from the BATSE large area detectors has been prepared. The first part of the catalog consists of results from the all-sky monitoring of 58 sources, mostly Galactic, with intrinsic variability on timescales of hours to years. For these sources, we have included tables of flux and spectral data, and outburst times for transients. Light curves (or flux histories) covering the entire nine mission are being placed on the world wide web. We then performed a deep-sampling of these 58 objects, plus a selection of 121 more objects, combining data from the entire 9.ly BATSE dataset. Source types considered were primarily accreting binaries, but a small number of representative active galaxies, X-ray-emitting stars, and supernova remnants were also included. The sample represents a compilation of sources monitored and/or discovered with BATSE and other high energy instruments between 1991 and 2000, known sources taken from the HEAO 1 A-4 (Levine et al. 1984) and Macomb and Gehrels (1999) catalogs. The deep sample results include definite detections of 82 objects and possible detections of 36 additional objects. The definite detections spanned three classes of sources: accreting black hole and neutron star binaries, active galaxies and supernova remnants. The average fluxes measured for the fourth class, the X-ray emitting stars, were below the confidence limit for definite detection. Flux data for the deep sample are presented in four energy bands: 20-40, 40-70, 70-160, and 160-430 keV. The limiting average flux level (9.1 y) for the sample varies from 3.5 to 20 mCrab (5delta) between 20 and 430 keV, depending on systematic error, which in turn is primarily dependent on the sky location. To strengthen the credibility of detection of weaker sources (approx.5-25 mCrab), we generated Earth occultation images, searched for periodic behavior using FFT and epoch folding methods, and critically evaluated the energy-dependent emission in the four flux bands. The deep sample results are intended for guidance in performing future all-sky surveys or pointed observations in the hard X-ray and low-energy gamma-ray band, as well as more detailed studies with the BATSE EOT.

Harmon, B. A.↗
NASA NTRS1988

On the universality of the two-point galaxy correlation function

The behavior of the two-point galaxy correlation function in volume-limited subsamples of three complete redshift surveys is investigated. The correlation length is shown to scale approximately as the square root of the distance limit in both the CfA and Southern Sky catalogs, but to be independent of the distance limit in the IRAS sample. This effect is found to be due to factors such as the large positive density fluctuations in the foreground of the optically selected catalogs biasing the correlation length estimate downward, and the brightest galaxies appearing to be more strongly clustered than the mean.

Davis, Marc↗
NASA NTRS1997

Two Extremely Red Galaxies

This report concerns one of the major observational studies in the ISO Central Programme, the ISO Normal Galaxy Survey. This is a survey of an unbiased sample of spiral and lenticular galaxies selected from the Revised Shapley-Ames Catalog. It is therefore optically-selected, with a brightness limit of blue magnitude = 12, and otherwise randomly chosen. The original sample included 150 galaxies, but this was reduced to 74 when the allocated observing time was expended because the ISO overheads encountered in flight were much larger than predicted.

Joseph, Robert D.↗
NASA NTRS2020

Hunting Distant BL Lacertae Objects with the Photometric Technique Using Swift and SARA

BL Lacertae objects represent a large fraction (22%) of γ-ray sources in the Third Fermi Large Area Telescope catalog (3FGL). Nearly half of the BL Lac object population remains without a redshift because of their featureless optical spectra. We aim to increase the number of BL Lac objects with a redshift measurement by using the photometric technique. For this work, we have used six Swift-UVOT filters and SDSS g′, r′, i′, and z′ optical filters mounted on the 0.65 m SARA–CTIO located in Chile and the 1.0 m SARA–ORM in the Canary Islands. A sample of 45 sources was selected from the 3FGL catalog for which photometry was performed in 10 optical and UV filters to obtain redshift measurements. We found three sources with z > 1.3, while reliable upper limits have been provided for 17 sources. The results presented here bring the total number of high-z (z > 1.3) BL Lac objects to 29.

M. Rajagopal↗
NASA NTRS1992

Newly identified main-sequence A stars with circumstellar dust

The IRAS Faint Source Survey data base and the ADDSCAN/SCANPI software are used to search for systems with circumstellar dust in two samples: all of the 62 A stars in Woolley's catalog, which lie near the main sequence and are typically within 25 pc of the sun, and all A stars in the Bright Star Catalogue with mV in the range 4-5 and v sin i not less than 100 km/s. In the first sample, 11 nearby A stars having (12)-(25) and (25)-(60) colors consistent with circumstellar dust are found. The analysis of the second sample demonstrates that the use of the FSS data base increases the likelihood of identifying A stars with circumstellar dust fainter than mV = 4. Three more new dusty systems are found in this sample. Beta Pictoris (A5 IV-V) is the only star within 25 pc of the sun that displays IR colors indicative of both warm and cool dust. It is inferred from the absence of cool dust in the vast majority of the systems that the dust disks of these stars are much less extended than that seen around Beta Pictoris.

Cheng, K.-P.↗
NASA NTRS1986

Studies of an x ray selected sample of cataclysmic variables

Just prior to the thesis research, an all-sky survey in hard x rays with the HEAO-1 satellite and further observations in the optical resulted in a catalog of about 700 x-ray sources with known optical counterparts. This sample includes 43 cataclysmic variables, which are binaries consisting of a detached white-dwarf and a Roche lobe filling companion star. This thesis consists of studies of the x-ray selected sample of catalcysmic variables.

Silber, Andrew D.↗
NASA NTRS2014

Observations of Environmental Quenching in Groups in the 11 GYR Since z = 2.5: Different Quenching For Central and Satellite Galaxies

We present direct observational evidence for star formation quenching in galaxy groups in the redshift range 0 less than z less than 2.5. We utilize a large sample of nearly 6000 groups, selected by fixed cumulative number density from three photometric catalogs, to follow the evolving quiescent fractions of central and satellite galaxies over roughly 11 Gyr. At z approximately 0, central galaxies in our sample range in stellar mass from Milky Way/M31 analogs (M=6.5x10(exp 10) M/solar mass) to nearby massive ellipticals (M=1.5x10(exp 11) M/solar mass). Satellite galaxies in the same groups reach masses as low as twice that of the Large Magellanic Cloud (M=6.5x10(exp 9) M/solar mass). Using statistical background subtraction, we measure the average rest-frame colors of galaxies in our groups and calculate the evolving quiescent fractions of centrals and satellites over seven redshift bins. Our analysis shows clear evidence for star formation quenching in group halos, with a different quenching onset for centrals and their satellite galaxies. Using halo mass estimates for our central galaxies, we find that star formation shuts off in centrals when typical halo masses reach between 10(exp 12) and 10(exp 13) M/solar mass, consistent with predictions from the halo quenching model. In contrast, satellite galaxies in the same groups most likely undergo quenching by environmental processes, whose onset is delayed with respect to their central galaxy. Although star formation is suppressed in all galaxies over time, the processes that govern quenching are different for centrals and satellites. While mass plays an important role in determining the star formation activity of central galaxies, quenching in satellite galaxies is dominated by the environment in which they reside.

Environmental↗
NASA NTRS1986

The cluster-cluster correlation function

The clustering properties of the Abell and Zwicky cluster catalogs are studied using the two-point angular and spatial correlation functions. The catalogs are divided into eight subsamples to determine the dependence of the correlation function on distance, richness, and the method of cluster identification. It is found that the Corona Borealis supercluster contributes significant power to the spatial correlation function to the Abell cluster sample with distance class of four or less. The distance-limited catalog of 152 Abell clusters, which is not greatly affected by a single system, has a spatial correlation function consistent with the power law Xi(r) = 300r exp -1.8. In both the distance class four or less and distance-limited samples the signal in the spatial correlation function is a power law detectable out to 60/h Mpc. The amplitude of Xi(r) for clusters of richness class two is about three times that for richness class one clusters. The two-point spatial correlation function is sensitive to the use of estimated redshifts.

Postman, M.↗
NASA NTRS1995

Large-Scale Structures in the Zone of Avoidance: The Galactic Anticenter Region

We have selected a sample of 876 galaxy candidates from the IRAS Point Source Catalog in the region of 2(exp h) < alpha < 10(exp h) and 0 deg < delta < 36 deg, which crosses the Galactic anticenter part of the Zone of Avoidance (ZOA) and includes most of the highly obscured Orion-Taurus complex region. We have identified galaxies among the candidate sources by attempting to detect the 21 cm H I line of those sources which were not known to be galaxies at the beginning of the survey. In this manner, we constructed a galaxy sample which is largely free from Galactic reddening. Of the 272 observed candidates, 89 were detected in the H I line up to a heliocentric velocity of v(sub h) approximately 16,000 km/s. The resulting galaxy sample of 717 galaxies is fairly complete (within about 10%) and uniform (within about 4%) in the part of the survey area 10 deg away from the Galactic plane and for velocities up to at least 9000 km/s. This provides, for the first time, a largely unbiased view on the large-scale structures in much of the survey area. Our main results are the following: (1) Several large voids are identified. In particular, a void between alpha approximately equals 3(sup h) and 4(sup h), up to v(sub h) approximately 6000 km/s, separates the Pisces-Perseus supercluster at alpha < 3(sup h) from structures at alpha > 4(sup h); and a "nearby void" occupies most of our survey area and reaches out to a redshift of nearly 3000 km/s. (2) We found no nearby galaxy concentration that could significantly contribute to the "Local Velocity Anomoly" (LVA), but a general excess of galaxies around v(sub h) approximately 5000 km/s in the survey area. (3) The contrast between the "Great Wall" at v(sub h) approximately 8500 km/s and the void in front of it appears to gradually diffuse out after it enters the Zone of Avoidance from the northern Galactic hemisphere. (4) Our data combined with other galaxy surveys in or near the Galactic anticenter part of the ZOA suggest that the main ridge of the Pisces-Perseus supercluster does not extend to Abell 569, a cluster in the northern Galactic hemisphere, and that the simple gravitational model consisting of the Local Void of Tully & Fisher, our nearby void, and Puppis and Fornax-Eridanus clusters would predict a LVA whose direction is probably too far away from that derived from observations.

Lu, Nanyao Y.↗