Engineering topics

Matthews, K.

Publications and source records attributed to Matthews, K..

At least 55 records · Page 3

NASA NTRS1991

Near-infrared observations of the z about 2.3 IRAS source FSC 10214 + 4724

Near-infrared imaging and spectroscopy of the extremely luminous IRAS source FSC 10214 + 4724 have been obtained using the Cassegrain infrared camera on the 200-inch Hale Telescope. A low-resolution spectrum in the 2.0-2.4 micron atmospheric window shows a very strong H-alpha line at the optically determined redshift z = 2.286. The observed rest-frame equivalent width of H-alpha is 0.07 +/-0.02 microns, consistent with the largest values found in quasars. The images show an unresolved source, while the near-infrared colors are somewhat redder than the mean colors of quasars observed at the same redshift. The reddening inferred is about 1.5 mag, with an upper limit of about 3.0 mag. If FSC 10214 + 4724 is a quasar, the reddening-corrected bolometric luminosity is approximately equal to the observed infrared luminosity.

Soifer, B. T.↗

NASA NTRS1991

The dust enshrouded quasar in the ultraluminous galaxy Markarian 463 - Radio, near-infrared, and optical imaging

New imaging data are presented at radio, near-infrared, and optical wavelengths to elucidate the processes associated with the ongoing merger and nuclear activity in Mrk 463. Imaging at 20 cm reveals previously unknown components 4 arcsec north and 18 arcsec south of Mrk 463E, and a source 10 arcsec to the northwest which is believed to be linked to the nuclear region. The western nucleus, Mrk 463W, was detected at 6 and 20 cm; it has a radio luminosity comparable to that of a moderately luminous Seyfert galaxy or a highly luminous starburst galaxy. Near-infrared images at wavelengths less than 2.3 microns show the two nuclei; only Mrk 463E has been detected at 3.7 microns. Brightness profiles of Mrk 463E are unresolved at K and L-prime, but extended at J. It is inferred from the fact that radio continuum components 4-18 kpc from the nucleus are aligned with previously known 0.05-1.5 kpc radio structure and extended conical O-III forbidden omission lines that Mrk 463E is powering weak radio lobes and therefore exemplifies a transition between the confined linear sources in Seyfert galaxies and the extended lobes in classical quasars and radio galaxies.

Mazzarella, J. M.↗

NASA NTRS1991

Research in planetary Astronomy

The focus was on the study, via near infrared observations, of the outer planets and their satellites. In the last year, these observations have emphasized imaging observations using the Cassegrain infrared camera at the f/70 focus of the 200 inch Hale telescope.

Matthews, K.↗

NASA NTRS1991

Near infrared imaging of the outer planets

In the last year we have continued our program of near infrared imaging of the outer planets of the solar system. Uranus is virtually invisible at 2.3 microns, showing that the methane is an effective absorber of the incident sunlight and that there is very little aerosol content in the upper atmosphere. On the other hand, Neptune shows a haze present over the entire Northern Hemisphere at 2.3 microns. This leads to the inference that there is an aerosol layer at a high altitude. We have recovered the Neptune satellite, 1989 N1, which was first discovered in Voyager images. The satellite is exceedingly faint in the near infrared, and was detectable only because the planet itself was comparatively faint at this wavelength. Observations of this satellite, coupled with the Voyager images, permit us to substantially refine the satellite's orbit, and hence carefully probe the gravitational field of Neptune.

Matthews, K.↗

NASA NTRS1990

The nature of unidentified 12 micron IRAS sources at high Galactic latitudes

A sample of 47 previously uncatalogued objects located above a Galactic latitude of 50 deg, and detected at 12 microns by the IRAS, is studied using near-infrared photometry. Ground-based observations show that the objects consist primarily of late-type M giant stars with long-wavelength excesses probably due to emission from dust associated with mass loss. The sample contains one oxygen-rich giant star undergoing rapid mass loss; an extremely cool (1230 K) carbon star 12560-1656 that may be as far as 10 kpc away; and a luminious quasar 13349-2438. The absence of nearby, low-luminosity infrared sources in this sample limits the space density of field brown dwarf stars. The fact that almost all the IRAS 12 micron sources have stellar counterparts visible on both the red and blue Palomar Observatory Sky Survey prints provides a tool for discriminating ordinary red stars.

Beichman, C. A.↗

NASA NTRS1989

Continuum energy distribution of quasars - Shapes and origins

Continuum observations from 0.3 nm to 6 cm are presented for 109 optically selected quasars from the Palomar-Green (PG) Bright Quasar Survey. The far-infrared to soft X-ray continuum of radio-quiet and steep-spectrum radio-loud PG quasars can be described in a model consisting of two broad peaks: an 'infrared bump' at about 2 microns to 1 mm and the well-known 'big blue bump' at about 10 nm to 0.3 micron. All PG quasars emit a significant fraction of their bolometric luminosity at infrared wavelengths of 1.5-100 microns. The fraction varies from 10 to 50 percent with a typical value of 30 percent. The ratio of the 6 cm flux density to that at 1 micron has a bimodal distribution. There is no evidence for a tight correlation between the infrared and X-ray continua of quasars. It is suggested that the bulk of the emission between 2 microns and 1 mm in the infrared bump of the radio-quiet PG quasars and the radio-loud quasars with steep radio spectral indices is produced by thermal processes.

Sanders, D. B.↗

NASA NTRS1989

The near-infrared variability of a sample of optically selected quasars

A complete sample of 108 optically selected quasars, the Palomar-Green quasars, has been studied at near-infrared wavelengths over an average time base of about 6 yr; in some cases the time base extends to 20 yr. The measurements show that about half the quasars have a high probability of having varied, but that half show little evidence of variability, in sharp contrast to published studies indicating that most quasars vary on comparable timescales at optical wavelengths. The maximum amplitude of variation is less than 1 mag and generally near 0.5 mag.

Neugebauer, G.↗

NASA NTRS1988

The IRAS Bright Galaxy Sample. III - 1-10 micron observations and coadded IRAS data for galaxies with L(IR) equal to or greater than 10 to the 11th solar luminosities

This paper presents the results of 1-10-micron observations and coadded IRAS data on 61 galaxies from the Bright Galaxy Sample, with IR luminosities, L(IR), equal to or greater than 10 to the 11th solar luminosities. It was found that an increase in the total L(IR) above 10 to the 11th solar luminosity is correlated with increased emission from hot dust with characteristic temperatures about 800 K. This hot dust contributes a substantial fraction of the 2.2- and 3.7-micron emission, resulting in a greatly increased dispersion in R(3.7/1.6) and R(2.2/1.6) for these high-luminosity galaxies, relative to lower-luminosity galaxies. This excess hot-dust emission appears to 'turn on' at luminosities of about 10 to the 11th solar luminosity. The spatial distribution of the 10-micron emission indicated a substantial extended component for most of the galaxies in this sample, implying that star-formation processes contribute significantly to the luminosities.

Carico, David P.↗

NASA NTRS1987

Ultraluminous infrared galaxies

The IRAS survey of the local universe has revealed the existence of a class of ultraluminous infrared galaxies with L(8 to 1000 micrometer) greater than 10 to the 12th L sub 0 that are slightly more numerous, and as luminous as optically selected quasars at similar redshift. Optical CCD images of these infrared galaxies show that nearly all are advanced mergers. Millimeter wave CO observations indicate that these interacting systems are extremely rich in molecular gas with total H2 masses 1 to 3 x 10 to the 10th power M sub 0. Nearly all of the ultraluminous infrared galaxies show some evidence in their optical spectra for nonthermal nuclear activity. It is proposed that their infrared luminosity is powered by an embedded active nucleus and a nuclear starburst both of which are fueled by the tremendous reservoir of molecular gas. Once these merger nuclei shed their obscuring dust, allowing the AGN to visually dominate the decaying starburst, they become the optically selected quasars.

Sanders, D. B.↗

NASA NTRS1987

Near-infrared observations of IRAS minisurvey galaxies

Near infrared photometry at J, H, and K was obtained for 82 galaxies from the IRAS minisurvey. The near infrared colors of these galaxies cover a larger range in J-H and H-K than do normal field spiral galaxies, and evidence is presented of a tighter correlation between the near and far infrared emission in far infrared bright galaxies than exists between the far infrared and the visible emission. These results suggest the presence of dust in the far infrared bright galaxies, with hot dust emission contributing to the 2.2 micron emission, and extinction by dust affecting both the near infrared colors and the visible luminosities. In addition, there is some indication that the infrared emission in many of the minisurvey galaxies is coming from a strong nuclear component.

Carico, David P.↗

NASA NTRS1986

Near-infrared observations of IRAS minisurvey galaxies

Near-infrared photometry was obtained for 82 galaxies from the Infrared Astronomy Satellite (IRAS) minisurvey, a sample of infrared selected galaxies. The near-infrared colors of these galaxies are similar to those of normal field spiral galaxies, but cover a larger range in J - H and H - K. There is evidence of a tighter correlation between the near and far infrared emission than exists between far-infrared and the visible emission. These results suggest that hot dust emission contributes to the 2.2 micron luminosity, and extinction by dust affects both the near-infrared colors and the visible luminosities. In addition, there is an indication that the far-infrared emission in many of the minisurvey galaxies is coming from a strong nuclear component.

Carico, David P.↗

NASA NTRS1986

Multifrequency observations of the superluminal quasar 3C 345

Attention is given to the continuum properties of the superluminal quasar 3C 345, on the basis of radio, optical, IR, and X-ray frequency monitorings, as well as by means of simultaneous multifrequency spectra extending from the radio through the X-ray bands. Radio outbursts, which appear to follow IR-optical outbursts by about one year, first occur at the highest frequencies, as expected from optical depth effects; the peak flux is nevertheless often reached at several frequencies at once. The beginning of outbursts, as defined by mm-measurements, corresponds to the appearance of the three known 'superluminal' components. An increase in the X-ray flux during 1979-1980 corresponds to increased radio flux, while the IR flux changes in the opposite sense.

Bregman, J. N.↗

NASA NTRS1986

Near-infrared observations of IRAS minisurvey galaxies

Carico, D. P.↗

NASA NTRS1986

Moderate resolution spectroscopy for the Space Infrared Telescope Facility (SIRTF)

A conceptual design for an IR spectrometer capable of both low resolution (lambda/Delta-lambda = 50; 2.5-200 microns) and moderate resolution (1000; 4-200 microns) has been developed. This instrument will allow the spectroscopic study in the infrared of objects ranging from within the solar system to distant galaxies. The spectroscopic capability provided by this instrument for SIRTF will give astronomical orders of magnitude greater sensitivity for the investigation of faint objects than has been previously available.

Houck, J. R.↗

NASA NTRS1986

Moderate resolution spectroscopy for the Space Infrared Telescope Facility (SIRTF)

The conceptual design presented for a low-to-moderate resolution IR spectrometer is expected to allow the spectroscopic study of objects whose location ranges from within the solar system to distant galaxies, with far greater sensitivity than previously available for the study of faint objects. The low resolution mode will allow detailed continuum radiation studies to be conducted, while the moderate resolution mode will facilitate studies encompassing the IR spectral signatures of small outer solar system bodies and the nature of more luminous active galaxies and QSOs at greater distances. The five spectrometer modules share a common aperture, and all gratings share a single scan mechanism. All heat sources other than the detectors operate at 7 K and are separated from the 4 K cold station. Two-dimensional area detector arrays are used in the 2.5- to 120-micron bands to simultaneously monitor adjacent regions in extended objects and to measure the background near point sources.

Houck, J. R.↗

NASA NTRS1984

Infrared observations of interacting/merging galaxies

The present sample of 20 galaxy systems, selected on the basis of morphological evidence for the tidal interaction or merger of two galaxies and observed at 1-10 microns, is noted to include 11 systems, detected at 10 microns, which have on average a significantly higher IR luminosity than noninteracting galaxies. The enhanced IR radiation is due to star formation bursts. On the basis of IR Astronomical Satellite results for a sample of galaxies, as much as 30 percent of all the far-IR emission observed arises in bursts of star formation that are triggered by interactions, and massive stars account for most of the luminosity in these bursts. It is suggested, in view of a massive star formation rate in the interacting and merging galaxies that is about 3 times higher than in noninteracting systems, that much of this star formation occurred in either nuclear regions or merger remnants.

Lonsdale, C. J.↗

NASA NTRS1984

Two multifrequency observations of 3C 371

Observations of 3C371 made at frequencies from the radio to the ultraviolet and coordinated during two short time intervals separated by 3 months are presented. Also presented are 1 keV X-ray flux densities measured at a different time. The multifrequency measurements indicate spectral steepening at visual wavelengths, and that an extrapolation of the ultraviolet continuum falls below the X-ray data. The infrared through X-ray data is explained as relativistically beamed synchrotron self-Compton emission, and source parameters are derived for two possible models. The present ultraviolet spectra both show strong Lyman-alpha emission at the same redshift as weak optical emission lines reported previously. Production of these lines by recombination of gas, after its ionization by the ultraviolet to X-ray continuum radiation, is favored as an explanation. C IV and N V absorption lines are tentatively identified in one ultraviolet spectrum, which, if real, suggest the presence of a hot (about 300,000 K) gaseous halo in 3C 371.

Puschell, J. J.↗

NASA NTRS1983

The rings of Uranus - Occultation profiles from three observatories

Occultation profiles for the nine confirmed Uranian rings obtained from Las Campanas, the European Southern Observatory, and Cerro Tololo on 15-16 August 1980 are compared. The alpha ring shows a 'double-dip' structure; the eta ring shows a broad and narrow component (similar to Saturn's F ring); and the epsilon ring shows six features that appear in the data from all three observatories. Diffraction fringes appear at the edges of several of the occultation profiles.

Elias, J. H.↗