scholarly journals Is the UV Alignment Effect Present in Low Redshift Radio Galaxies?

1996 ◽  
Vol 175 ◽  
pp. 234-235
Author(s):  
Andrea Cimatti ◽  
Sperello Di Serego Alighieri
Keyword(s):  
Rest Frame ◽  
Radio Galaxy ◽  
Selection Effect ◽  
Radio Galaxies ◽  
Emission Lines ◽  
Main Question ◽  
Strong Emission ◽  
Alignment Effect ◽  
Origin And Evolution ◽  
First Results

When a FRII radio galaxy at z > 0.7 is observed in the optical, its continuum appears extended and aligned with the radio axis. This phenomenon occurs actually when the optical bands start to sample the rest-frame UV, and it was called alignment effect (McCarthy et al. 1987). The UV continuum of high z radio galaxies shows also strong linear polarization due to scattering of anisotropic radiation escaping from the obscured quasar nucleus (di Serego Alighieri, Cimatti & Fosbury 1994). However, the observations of the UV continuum have been concentrated mostly on high z radio galaxies, leaving open a main question : is the alignment effect an evolutionary phenomenon present only at high z, or is it simply a selection effect due to the K-correction ? In order to investigate the origin and evolution of the UV alignment effect, we have started a ground-based imaging and polarimetric survey for studying the UV continuum in FR II radio galaxies with 0.1 < z < 0.5. Depending on the redshift, the filters U and B can be used to sample the UV continuum free from strong emission lines, and in the same rest-frame spectral region observed in radio galaxies at higher redshift. The survey is in progress and here we present only our first results.

scholarly journals Galaxies with Binary Nuclei

2013 ◽  
Vol 9 (S304) ◽  
pp. 363-370
Author(s):  
Yervant Terzian ◽  
Edward Khachikian
Keyword(s):  
Hubble Space Telescope ◽  
Radio Galaxies ◽  
Active Galaxies ◽  
Emission Lines ◽  
Special Astrophysical Observatory ◽  
Host Galaxies ◽  
Strong Emission ◽  
Space Telescope ◽  
Byurakan Astrophysical Observatory ◽  
The Common

AbstractIt is known that among active galaxies (AG) with strong emission lines (UV-galaxies, Sy1 and Sy2, Markarian and Kazarian galaxies, radio-galaxies, QSOs host galaxies and so on) there is a large percentage of objects with double and multiple (or complex) nuclei. The common sizes of these nuclei are of the order of a few hundred parsecs or kiloparsecs. We shall discuss the results of morphological and spectroscopic observations of a number of “active galaxies” carried out with the 5m Palomar telescope, 2.6m telescope of Ambartsumian Byurakan Astrophysical Observatory, 6m telescope of Special Astrophysical Observatory in Russia, and newer Hubble Space Telescope data.

scholarly journals Optical Spectra of Radio-Loud and Radio-Quiet Active Galactic Nuclei

1982 ◽  
Vol 97 ◽  
pp. 369-371 ◽  
Author(s):  
Donald E. Osterbrock
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Radio Galaxies ◽  
Optical Spectra ◽  
Emission Lines ◽  
Radio Sources ◽  
Strong Emission ◽  
Normal Galaxies ◽  
Many Sources

Many radio galaxies have strong emission lines in their optical spectra. The fraction with such lines is much larger than in “normal” galaxies. Radio galaxies generally also have very bright nuclei; thus those with strong emission lines are similar in both respects to Seyfert galaxies. Hence radio and Seyfert galaxies are both generally considered to be similar physical objects: active galactic nuclei. Their observational properties show they are closely related to quasars (quasi-stellar radio sources) and (radio-quiet) QSOs. A short table of the space density of these objects, culled from many sources, chiefly Schmidt (1978) and Simkim, Su and Schwarz (1980) is given below. Although all the numbers are quite uncertain, there is no doubt that the radio-loud objects are relatively rare. With less certainty, it appears that the ratio of numbers of radio galaxies to Seyfert galaxies is about the same as the ratio of numbers of quasars to QSOs.

scholarly journals The Origin and Evolution of Giant Radio Galaxies

2022 ◽  
Vol 8 ◽  
Author(s):  
David Garofalo
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Spiral Galaxies ◽  
Radio Galaxy ◽  
Galactic Nuclei ◽  
Radio Galaxies ◽  
High Excitation ◽  
Origin And Evolution ◽  
Black Hole Spin ◽  
Upper Limit

Giant radio galaxies are arguably the least understood of jetted active galactic nuclei (AGN). We propose that radio galaxies are the product of large mergers that do not involve radio galaxies or radio quasars, such as in merging spiral galaxies, while giant radio galaxies emerge from a merger involving a parent that in the not-too-distant past harbored a radio galaxy. Predictions following from this are an upper limit to the number fraction of giant radio galaxies to radio galaxies, lower average redshift for giant radio galaxies, a higher incidence of high excitation for giant radio galaxies compared with radio galaxies, and lower average prograde black hole spin values for giant radio galaxies compared to radio galaxies and to bright radio quiet quasars.

scholarly journals Extended Emission Lines in Radio Galaxies

1982 ◽  
Vol 97 ◽  
pp. 65-67
Author(s):  
R A E Fosbury
Keyword(s):  
Chemical Composition ◽  
Physical State ◽  
Radio Galaxy ◽  
Optical Emission ◽  
Radio Galaxies ◽  
Elliptical Galaxies ◽  
Emission Lines ◽  
Ionization Mechanism ◽  
Nuclear Activity ◽  
Extended Emission

In whatever physical state the gas is found, observations of the interstellar medium in elliptical galaxies are of considerable interest. This is particularly true in the case of radio galaxies where we believe that the gas is an indespensable part of the cause of nuclear activity and plays a role in the origin and the evolution of the radio galaxy phenomenon. In a few cases we are fortunate to find some of the gas to be ionized with a temperature of about 104 K where optical spectroscopy allows us to deduce something about the excitation/ionization mechanism, about its chemical composition and about its state of motion. Here I wish to summarize observations of three Southern radio galaxies which show optical emission lines from regions tens of kiloparsecs in extent.

scholarly journals Superluminal Behaviour of the Double-Lobed Radio Galaxy 3C111

1988 ◽  
Vol 129 ◽  
pp. 105-106
Author(s):  
Eugen Preuss ◽  
Walter Alef ◽  
Kenneth I. Kellermann
Keyword(s):  
Radio Emission ◽  
Time Dependence ◽  
Radio Galaxy ◽  
Monitoring Program ◽  
Radio Galaxies ◽  
Scale Structure ◽  
Small Scale ◽  
Broad Line ◽  
First Results ◽  
First Time

Due to sensitivity problems only about a dozen of the powerful double-lobed radio galaxies have so far been mapped with VLBI. Even less is known about the time dependence of the small scale structure in these objects (Preuss and Alef, 1987). We have recently reported the first results of our monitoring program of classical double sources. We observed strong changes of the pc-scale structure in 3C111 (Götz et al., 1987) and 3C390.3 (Alef et al., 1987) implying “superluminal behaviour” in both sources. This is the first time that such a phenomenon has been found in lobe-dominated radio galaxies. Both objects are Broad Line Radio Galaxies of type N, and their radio emission from m to cm wavelengths is dominated by their outer lobes which are ∼300 kpc apart (H0 = 50 km/s/Mpc).

Properties of LBGs with [OIII] detection at z > 3: The importance of including nebular emission data in SED fitting

2019 ◽  
Vol 15 (S341) ◽  
pp. 201-205
Author(s):  
Fang-Ting Yuan ◽  
Denis Burgarella ◽  
David Corre ◽  
Veronique Buat ◽  
Médéric Boquien ◽  
...  
Keyword(s):  
Physical Properties ◽  
Emission Line ◽  
Equivalent Width ◽  
Spectroscopic Data ◽  
Rest Frame ◽  
High Redshift ◽  
Emission Lines ◽  
Emission Data ◽  
Strong Emission ◽  
The Difference

AbstractAt high redshift, the contribution of strong emission lines to the broadband photometry can cause large uncertainties when estimating galaxy physical properties. To examine this effect, we investigate a sample of 54 LBGs at 3 < zspec < 3.8 with detected [OIII] line emissions. We use CIGALE to fit simultaneously the rest-frame UV-to-NIR SEDs of these galaxies and their emission line data. By comparing the results with and without emission line data, we show that spectroscopic data are necessary to constrain the nebular model. We examine the K-band excess, which is usually used to estimate the emissions of [OIII]+Hβ lines when there is no spectral data, and find that the difference between the estimation and observation can reach up to > 1 dex for some galaxies, showing the importance of obtaining spectroscopic measurements of these lines. We also estimate the equivalent width of the Hβ absorption and find it negligible compared to the Hβ emission.

scholarly journals Cosmological Studies from the MRC/1Jy Radio Galaxy Sample: The Spectral Index – Redshift Correlation

1999 ◽  
Vol 183 ◽  
pp. 251-251
Author(s):  
R.M. Athreya ◽  
V.K. Kapahi
Keyword(s):  
Spectral Index ◽  
Rest Frame ◽  
Radio Galaxy ◽  
High Redshift ◽  
Radio Galaxies ◽  
Linear Size ◽  
Radio Sources ◽  
Frequency Range ◽  
Galaxy Sample ◽  
Frame Frequency

The MRC/1Jy sample of 559 radio sources with S408 MHz ≥ 0.95 Jy (McCarthy et al. 1996; Kapahi et al. in preparation) is a factor of 5 to 6 times deeper than the 3CRR sample; it is therefore, well suited for disentangling the redshift (z) and luminosity (P) dependence of several properties of extragalaxtic radio sources. Here we present results on the spectral index — redshift correlation for radio galaxies, based on a comparison of the well documented radio spectra (in the rest frame frequency range of about 1 to 16 GHz) of the following two matched-luminosity samples, (a) 14 high redshift radio galaxies (HRRG) from MRC with 2.0 < z < 3.2 and linear size i > 10 kpc, and (b) 21 intermediate z radio galaxies (IRRG) from 3CRR with 0.85 < z < 1.7 and l > 10 kpc. Both samples have P1.4 GHz in the range 1028 and 1028.8 WHz−1.

scholarly journals Physical Conditions in Radio Galaxies and Quasars

1977 ◽  
Vol 74 ◽  
pp. 183-191
Author(s):  
Donald E. Osterbrock
Keyword(s):  
Emission Line ◽  
Large Fraction ◽  
Radio Galaxies ◽  
Emission Lines ◽  
Ionized Gas ◽  
Strong Emission ◽  
Normal Galaxies ◽  
Physical Conditions ◽  
Early Survey ◽  
Optical Identifications

It is well known from the pioneering work of Baade and Minkowski that radio galaxies very often have strong emission lines in the spectra of their nuclei, indicating the presence of relatively large amounts of ionized gas. For instance, in the early survey of radio galaxies by Schmidt (1965), of the 35 galaxies observed, 32 had at least [0 II] λ3727 in their spectra and well over half had relatively strong [0 II] and other observable emission lines as well. In the recent review of optical identifications and spectroscopy of the revised 3C catalogue of radio sources by Smith et al. (1976), 137 radio galaxies are listed. Of these descriptive spectral information is given for 98, of which 49 show strong–emission line spectra, 19 intermediate–strength emission, 12 weak emission, and 18 a pure absorption–line spectrum without detectable emission lines. The fraction of objects with emission line–spectra is much higher than for normal galaxies. It is thus apparent that though the presence of emission lines is neither a necessary nor a sufficient condition that a galaxy be an observable radio source, nevertheless a large fraction of radio galaxies do contain ionized gas in their nuclei.

scholarly journals The SAMI Galaxy Survey: reconciling strong emission line metallicity diagnostics using metallicity gradients

2021 ◽  
Vol 502 (3) ◽  
pp. 3357-3373
Author(s):  
Henry Poetrodjojo ◽  
Brent Groves ◽  
Lisa J Kewley ◽  
Sarah M Sweet ◽  
Sebastian F Sanchez ◽  
...  
Keyword(s):  
Emission Line ◽  
Electron Temperature ◽  
Gas Phase ◽  
Mass Range ◽  
Accurate Method ◽  
Emission Lines ◽  
Mass Relation ◽  
Strong Emission ◽  
Data Release ◽  
Accurate Comparison

ABSTRACT We measure the gas-phase metallicity gradients of 248 galaxies selected from Data Release 2 of the SAMI Galaxy Survey. We demonstrate that there are large systematic discrepancies between the metallicity gradients derived using common strong emission line metallicity diagnostics. We determine which pairs of diagnostics have Spearman’s rank coefficients greater than 0.6 and provide linear conversions to allow the accurate comparison of metallicity gradients derived using different strong emission line diagnostics. For galaxies within the mass range 8.5 &lt; log (M/M⊙) &lt; 11.0, we find discrepancies of up to 0.11 dex/Re between seven popular diagnostics in the metallicity gradient–mass relation. We find a suggestion of a break in the metallicity gradient–mass relation, where the slope shifts from negative to positive, occurs between 9.5 &lt; log (M/M⊙) &lt; 10.5 for the seven chosen diagnostics. Applying our conversions to the metallicity gradient–mass relation, we reduce the maximum dispersion from 0.11 dex/Re to 0.02 dex/Re. These conversions provide the most accurate method of converting metallicity gradients when key emission lines are unavailable. We find that diagnostics that share common sets of emission line ratios agree best, and that diagnostics calibrated through the electron temperature provide more consistent results compared to those calibrated through photoionization models.

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