Detection of Far-Ultraviolet High-Excitation Line Emission and Lyman- beta Absorption in the Gravitational Lens Q0957+561

1993 ◽  
Vol 417 ◽  
pp. L57 ◽  
Author(s):  
A. G. Michalitsianos ◽  
J. Nichols-Bohlin ◽  
F. C. Bruhweiler ◽  
D. Kazanas ◽  
Y. Kondo ◽  
...  
Keyword(s):  
Line Emission ◽  
Gravitational Lens ◽  
High Excitation ◽  
Excitation Line ◽  
Far Ultraviolet

Voyager Observations of Diffuse Far-Ultraviolet Continuum and Line Emission in Eridanus

1993 ◽  
Vol 419 ◽  
pp. 739 ◽  
Author(s):  
Jayant Murthy ◽  
M. Im ◽  
R. C. Henry ◽  
J. B. Holberg
Keyword(s):  
Line Emission ◽  
Ultraviolet Continuum ◽  
Far Ultraviolet

Possible detection of far-ultraviolet line emission from a hot galactic corona

1981 ◽  
Vol 249 ◽  
pp. L51 ◽  
Author(s):  
P. D. Feldman ◽  
W. H. Brune ◽  
R. C. Henry
Keyword(s):  
Line Emission ◽  
Far Ultraviolet

scholarly journals The “Gravitational Lens” 3C 321: A Remarkable Impostor

1987 ◽  
Vol 124 ◽  
pp. 761-765
Author(s):  
Alexei V. Filippenko
Keyword(s):  
Radio Galaxy ◽  
Line Emission ◽  
Careful Analysis ◽  
Gravitational Lens ◽  
Emission Lines ◽  
Optical Data ◽  
High Ionization ◽  
Spectrum Radio ◽  
Hα Emission

Recent observations of the radio galaxy 3C 321 are presented. The optical nucleus consists of two components (A, B), separated by ∼ 4″ (∼ 6 kpc), whose low-resolution spectra strongly resemble those of high-ionization type 2 Seyfert nuclei. The relative intensities of the emission lines differ in A and B by less than 1%, and their profiles are almost identical. 3C 321 appears to be a convincing example of a gravitationally lensed object.Careful analysis of high-quality radio and optical data, however, reveals that the system is almost certainly not a lens. The equivalent widths of the emission lines are roughly twice as high in B than in A, and there are significant spatial offsets between regions of bright continuum and line emission. A slight, but fundamental, difference is visible in the two Hα emission profiles. The radial velocities of A and B are discrepant by 31 ± 10 km s−1. Finally, component A is nearly coincident with a flat-spectrum radio core, whereas B is next to an extended, steep-spectrum knot of radio emission.This object should serve as a warning to lens hunters: beware of impostors, whose true properties may be difficult to ascertain without extensive optical and radio observations.

scholarly journals Faint Optical Line Emission from the Diffuse Interstellar Medium: Observations and Implications

1990 ◽  
Vol 139 ◽  
pp. 157-169
Author(s):  
R. J. Reynolds
Keyword(s):  
Galactic Disk ◽  
Emission Measure ◽  
Line Emission ◽  
Thick Layer ◽  
Photon Flux ◽  
H Ii Regions ◽  
Interstellar Gas ◽  
Emission Line Spectrum ◽  
Optical Line ◽  
Far Ultraviolet

Diffuse galactic Hα emission appears to cover the entire sky with an intensity that ranges from 3–12 R near the galactic equator to 0.25–0.8 R near the galactic poles. Observations of this H-recombination line and the forbidden lines, [S II] 6716 Å, [N II] 6583 Å, and [O III] 5007 Å, indicate that the emission originates from a low-density, 2–3 kpc thick layer of warm (~104 K), ionized interstellar gas that has an emission-line spectrum significantly different from that of the traditional, more localized H II regions. Along a line perpendicular to the galactic disk, the mean emission measure of this layer is 4.5 cm−6 pc, and the column density of the H+ is 2 × 1020 cm−2. The origin of this diffuse ionization is not yet clear; however, its existence requires the equivalent of about 14% of the total ionizing photon flux from O stars or nearly all of the power injected into the ISM by supernova. This optically emitting gas also may be a nonnegligible source of diffuse emission in the far ultraviolet (FUV) and infrared (IR).

scholarly journals Excitation of H2 and HD in Shocks and PDRs

2000 ◽  
Vol 197 ◽  
pp. 191-201 ◽  
Author(s):  
F. Bertoldi ◽  
B. T. Draine ◽  
D. Rosenthal ◽  
R. Timmermann ◽  
S. K. Ramsay Howat ◽  
...  
Keyword(s):  
Emission Line ◽  
High Velocity ◽  
Molecular Hydrogen ◽  
Line Emission ◽  
High Excitation ◽  
Vibrationally Excited ◽  
Photodissociation Regions ◽  
Very High

Photodissociation regions (PDRs) and shocks give rise to conspicuous emission from rotationally and vibrationally excited molecular hydrogen. This line emission has now been studied with ISO and from the ground in great detail. A remarkable discovery has been that toward the Orion outflow and other shock-excited regions, the H2 level populations show a very high excitation component. We suggest that these high-excitation populations may arise from non-thermal pumping processes, such as H2 formation and high-velocity ion-molecule collision in partially dissociative shocks. In PDRs such as NGC 7023 however, formation pumping is always less important than fluorescent pumping.We furthermore present two HD emission line detections toward Orion Peak 1. This enables the first comparison of the H2 and the HD excitation, which surprisingly turn out to be identical.

Discovery of highly ionized line emission in the far ultraviolet

1986 ◽  
Vol 6 (2) ◽  
pp. 79
Author(s):  
Christopher Martin ◽  
Stuart Bowyer
Keyword(s):  
Line Emission ◽  
Far Ultraviolet
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