scholarly journals Optical Line Emission fromz∼ 6.8 Sources with Deep Constraints on LyαVisibility

2017 ◽  
Vol 839 (2) ◽  
pp. 73 ◽  
Author(s):  
M. Castellano ◽  
L. Pentericci ◽  
A. Fontana ◽  
E. Vanzella ◽  
E. Merlin ◽  
...  
Keyword(s):  
Line Emission ◽  
Optical Line

scholarly journals Discovery of diffuse optical emission lines from the inner Galaxy: Evidence for LI(N)ER-like gas

2020 ◽  
Vol 6 (27) ◽  
pp. eaay9711 ◽  
Author(s):  
D. Krishnarao ◽  
R. A. Benjamin ◽  
L. M. Haffner
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Center ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Hydrogen Gas ◽  
Emission Lines ◽  
Neutral Gas ◽  
Optical Line ◽  
Tilted Disk

Optical emission lines are used to categorize galaxies into three groups according to their dominant central radiation source: active galactic nuclei, star formation, or low-ionization (nuclear) emission regions [LI(N)ERs] that may trace ionizing radiation from older stellar populations. Using the Wisconsin H-Alpha Mapper, we detect optical line emission in low-extinction windows within eight degrees of Galactic Center. The emission is associated with the 1.5-kiloparsec-radius “Tilted Disk” of neutral gas. We modify a model of this disk and find that the hydrogen gas observed is at least 48% ionized. The ratio [NII] λ6584 angstroms/Hα λ6563 angstroms increases from 0.3 to 2.5 with Galactocentric radius; [OIII] λ5007 angstroms and Hβ λ4861 angstroms are also sometimes detected. The line ratios for most Tilted Disk sightlines are characteristic of LI(N)ER galaxies.

scholarly journals The Compact Magnetic Field Structures of AGN from Space VLBI Polarization Observations

2001 ◽  
Vol 205 ◽  
pp. 134-135
Author(s):  
D.C. Gabuzda ◽  
J.L. Gómez
Keyword(s):  
Magnetic Field ◽  
Active Galactic Nuclei ◽  
Linear Polarization ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Emission Mechanism ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Bl Lac ◽  
Optical Line

BL Lacertae objects are active galactic nuclei with weak, sometimes undetectable, optical line emission and strong variability in total intensity and linear polarization over a broad range of wavelengths from ultraviolet to radio. It is believed that synchrotron radiation is the dominant emission mechanism virtually throughout the spectrum. Their strong linear polarization makes BL Lac objects prime targets for space VLBI polarization 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 The Galactic Halo Ionising Field

1997 ◽  
Vol 14 (1) ◽  
pp. 59-63 ◽  
Author(s):  
J. Bland-Hawthorn ◽  
P. R. Maloney
Keyword(s):  
Galactic Halo ◽  
Galactic Disk ◽  
Line Emission ◽  
Young Stars ◽  
Star Forming ◽  
Star Forming Regions ◽  
Optical Line ◽  
The Mean ◽  
Alternative Sources ◽  
Magellanic Stream

AbstractThere has been much debate in recent decades as to what fraction of ionising photons from star-forming regions in the Galactic disk escape into the halo. The recent detection of the Magellanic Stream in optical line emission at the CTIO 4 m and the AAT 3·9 m telescopes may now provide the strongest evidence that at least some of the radiation escapes the disk completely. We present a simple model to demonstrate that, while the distance to the Magellanic Stream is uncertain, the observed emission measures (εm ≈ 0·5 – 1 cm−6 pc) are most plausibly explained by photoionisation due to hot, young stars. This model requires that the mean Lyman-limit opacity perpendicular to the disk is τLL ≈ 3, and the covering fraction of the resolved clouds is close to unity. Alternative sources (e.g. shock, halo, LMC or metagalactic radiation) contribute negligible ionising flux.

scholarly journals Unification in the low radio luminosity regime: evidence from optical line emission

2005 ◽  
Vol 361 (2) ◽  
pp. 469-475 ◽  
Author(s):  
M. J. M. Marchã ◽  
I. W. A. Browne ◽  
N. Jethava ◽  
S. Antón
Keyword(s):  
Line Emission ◽  
Radio Luminosity ◽  
Optical Line

scholarly journals Optical Line Emission from IO

1974 ◽  
Vol 65 ◽  
pp. 527-531 ◽  
Author(s):  
Robert A. Brown
Keyword(s):  
Line Emission ◽  
Early Summer ◽  
Time Varying ◽  
Sodium Atoms ◽  
Optical Line

In early summer of 1972, we discovered an anomalous brightness in the spectrum of Io near the sodium D-lines. This effect is revealed to be time-varying emission by free sodium atoms on Io.

scholarly journals The Relationship of Hard X‐Ray and Optical Line Emission in Low‐Redshift Active Galactic Nuclei

2005 ◽  
Vol 634 (1) ◽  
pp. 161-168 ◽  
Author(s):  
T. M. Heckman ◽  
A. Ptak ◽  
A. Hornschemeier ◽  
G. Kauffmann
Keyword(s):  
Active Galactic Nuclei ◽  
Line Emission ◽  
Galactic Nuclei ◽  
X Ray ◽  
Optical Line ◽  
Relationship Of ◽  
The Relationship

The Wind‐Wind Collision Region of the Wolf‐Rayet Binary V444 Cygni: How Much Optical Line Emission Does It Produce?

2001 ◽  
Vol 563 (1) ◽  
pp. 341-350 ◽  
Author(s):  
Aaron Flores ◽  
Lawrence H. Auer ◽  
Gloria Koenigsberger ◽  
Octavio Cardona
Keyword(s):  
Line Emission ◽  
Collision Region ◽  
Optical Line

scholarly journals An Atlas of Extragalactic Radio Sources

1996 ◽  
Vol 175 ◽  
pp. 157-158 ◽  
Author(s):  
J.P. Leahy ◽  
A.H. Bridle ◽  
R.G. Strom
Keyword(s):  
High Resolution ◽  
Line Emission ◽  
Radio Sources ◽  
X Rays ◽  
Complete Sample ◽  
High Quality ◽  
Extragalactic Radio Sources ◽  
Optical Line

Our Atlas of Extragalactic Radio Sources will present high-quality images of the nearer half of “3CRR”, the sample defined by Laing, Riley & Longair (1983). This is the best-studied complete sample of extragalactic radio sources. All 173 members have secure redshifts and most have been imaged in the radio at high resolution. There is also copious information on their optical line emission, and many have been detected in the sub-mm, FIR, and in X-rays. 3CRR is widely used as a baseline against which fainter, higher-redshift samples can be compared to define the evolution of the population (e.g. Neeser et al. 1995; Law-Green, this conference).

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