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  • ASTROPHYSICS  (8)
  • 1990-1994  (8)
  • 1
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    The properties of infrared galaxies in the local universe (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The 60-micron selected IRAS Bright Galaxy Sample is used as a starting point to derive additional complete flux-limited samples of extragalactic objects at 12, 25, and 100 microns. With these complete samples the luminosity functions at all IRAS wavelengths are derived for the local universe. These luminosity functions are used to determine the infrared emission of the local universe. The maximum in the energy output of galaxies occurs at 100 microns. The infrared emission of galaxies at 12 and 25 micron represents about 30 percent of the total infrared luminosity in the local universe. The mean infrared colors of infrared selected galaxies vary systematically with infrared luminosity; the ratio S sub nu (60 microns)/S sub nu(100 microns) increases and S sub nu(12 microns)/S sub nu(25 microns) decreases with increasing infrared luminosity.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 101; 354-361
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  • 2
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    Near-infrared images and color maps of Arp 220 (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Near-infrared images (1.3-3.7 microns) are presented for the nuclear region of Arp 220. Color maps in J - H and H - K reveal steep gradients, and the two nuclei previously detected at 20 cm and 2.2 microns appear on the J - H image as peaks separated by 1 arcsec. Hot dust emission (T about 1000 K) at 3.7 microns and extremely red J - H and H - K colors are found for both nuclei. The increasingly red color approaching the center of the galaxy are explained most naturally by a mixture of extinction and emission by increasing amounts of hot dust. The near-infrared emission is consistent with a circumnuclear starburst extending to a radius of about 1.5 kpc from the nuclei; further from the center the colors are consistent with a normal late-type stellar population. Inside a radius of 1 kpc the color maps show a NE-SW elongation that aligns with the concentration of molecular gas seen in CO images. The observed 3.7-micron luminosity, when corrected for nuclear extinction determined by 10-micron silicate absorption measurements and normalized by the bolometric luminosity, is consistent with UV-excess quasars and is about 10 times greater than that found in infrared luminous starburst galaxies.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 103; 413-421
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  • 3
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    The dust enshrouded quasar in the ultraluminous galaxy Markarian 463 - Radio, near-infrared, and optical imaging (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: 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.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 102; 1241-125
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  • 4
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    Near-infrared observations of the z about 2.3 IRAS source FSC 10214 + 4724 (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: 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.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 381; L55-L57
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  • 5
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    Diffraction limited infrared images of the binary star T Tauri (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: High-resolution images of T Tau and its infrared companion have been reconstructed from near- and midinfrared data collected at the Hale 5-m telescope. The near-infrared (1-5 microns) results were obtained by 2D speckle imaging and the midinfrared (10-20 microns) results were derived from shift-and-add procedures applied to slit scans. The spectral energy distributions of the separated components were constructed from 1- to 20-micron data collected in less than half a year (September 1990 to January 1991). The spectral energy distribution of the optical component (T Tau N) is interpreted as containing two distinct constituents, a photosphere and a surrounding disk of circumstellar material. Measurements at a number of infrared wavelengths over the period December 1985 to January 1991 show a 2-mag color-independent change in the brightness of the infrared component (T Tau S). It is proposed that this may have been caused by an increase in accretion onto T Tau S and model the spectral energy distribution of T Tau S as being dominated by an accretion disk.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 102; 2066-207
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  • 6
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    1.25-mm observations of luminous infrared galaxies (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Measurements at a wavelength of 1.25 mm have been obtained for 17 IRAS galaxies selected on the basis of high far-infrared luminosity. These measurements are used to estimate the lower and upper limits to the mass of cold dust in infrared galaxies. As a lower limit on dust mass, all of the galaxies can be successfully modeled without invoking any dust colder than the dust responsible for the 60 and 100 micron emission that was detected by IRAS. As an upper limit, it is possible that the dust mass in a number of the galaxies may actually be dominated by cold dust. This large difference between the lower and upper limits is due primarily to uncertainty in the long-wavelength absorption efficiency of the astrophysical dust grains.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 104; 681; p. 1086-1090.
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  • 7
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    High spatial resolution continuum and H-alpha imaging of the high-redshift IRAS source FSC 10214+4724 (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: New observations are reported which support the view that the high-redshift IRAS source FSC 10214+4724 is a rare extreme example of the class of ultraluminous infrared galaxies observed in the local universe. The presence of two continuum components and a compact H-alpha source suggests that a merger between two or more gas-rich systems has triggered the production of a powerful dust-enshrouded quasar which is responsible for the bulk of the luminosity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 399; 1; p. L55-L58.
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  • 8
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    Multifrequency observations of BL Lacertae (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Optical, IR, and radio monitoring data covering 20 years are presented for BL Lac. Also, four simultaneous multifrequency spectra are given, covering the range 10 to the 9th - 10 to the 18th Hz. These spectra include ground-based observations and data from the Einstein, Exosat, IUE, and IRAS satellites. From the monitoring data, the character of emission variability is determined using structure functions. The multifrequency spectra are used to study the origin of X-ray emission and to determine the physical parameters of emitting regions. The data show that the emitting region is inhomogeneous, with a small inner region of high density and magnetic field that eventually becomes a large, partially opaque radio emitting region with a low density and magnetic fields. Also, the two simple predictions of the synchrotron self-Compton model are reproduced by the multifrequency spectra.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 352; 574-586
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