Accurate Radio Positions with the Tidbinbilla Interferometer

1979 ◽  
Vol 3 (6) ◽  
pp. 400-402 ◽  
Author(s):  
M. J. Batty ◽  
David L. Jauncey ◽  
P. T. Rayner ◽  
S. Gulkis
Keyword(s):  
Absorption Spectra ◽  
High Redshift ◽  
Optical Emission ◽  
Radio Sources ◽  
Stellar Objects ◽  
Bl Lac Objects ◽  
Optical Position ◽  
Bl Lac ◽  
Compact Galaxies ◽  
Optical Identifications

Radio position measurements with an error of <2” arc rms allow reliable optical identifications of compact radio sources to be made solely on the basis of radio-optical position coincidence. In this way neutral or red stellar objects, faint compact galaxies and faint QSOs can be reliably identified. Such identifications are of particular interest because they are rich in BL Lac objects, high-redshift QSOs, QSOs with unusual optical emission or absorption spectra and galaxies with active nuclei (see Jauncey et al. 1978).

scholarly journals High-redshift BL Lac Objects: Spectroscopy of Candidates

2018 ◽  
Vol 861 (2) ◽  
pp. 130 ◽  
Author(s):  
M. Landoni ◽  
S. Paiano ◽  
R. Falomo ◽  
R. Scarpa ◽  
A. Treves
Keyword(s):  
High Redshift ◽  
Bl Lac Objects ◽  
Bl Lac

scholarly journals The Possibility to Link Radio and Optical Reference Frames With Artificial Satellites

1990 ◽  
Vol 141 ◽  
pp. 194-194
Author(s):  
Tong Fu
Keyword(s):  
Reference Frame ◽  
Reference Frames ◽  
Artificial Satellites ◽  
Radio Sources ◽  
Bl Lac Objects ◽  
Extragalactic Radio Sources ◽  
Bl Lac ◽  
Optical Reference ◽  
Radio Stars ◽  
Fundamental Reference

Based on extragalactic radio sources, a new high precision extragalactic radio reference frame can be established from radio interferometric measurements. To link the optical fundamental reference frame presently represented by the FK4/5 to the extragalactic radio frame, the optical counterparts of extragalactic radio sources (quasars, BL Lac objects etc.) and radio stars are the most important classes of objects. Besides these two classes of objects, are there any other objects which can be used to link the optical and radio frames? A posible answer is that artificial satellites could be a candidate class of objects contributing to this subject.

Optical spectroscopy of BL Lac objects: TeV candidates

2020 ◽  
Vol 497 (1) ◽  
pp. 94-108 ◽  
Author(s):  
Simona Paiano ◽  
Renato Falomo ◽  
Aldo Treves ◽  
Riccardo Scarpa
Keyword(s):  
Lower Limit ◽  
Gamma Ray ◽  
Absorption Lines ◽  
Host Galaxies ◽  
Stellar Objects ◽  
Bl Lac Objects ◽  
Forbidden Transition ◽  
Bl Lac ◽  
Quasi Stellar Objects ◽  
Relationship Of

ABSTRACT We investigate the spectroscopic optical properties of gamma-ray sources detected with high significance above 50 GeV in the Third Catalog of Hard Fermi-LAT Sources and that are good candidates as TeV emitters. We focus on the 91 sources that are labelled by the Fermi team as BL Lac (BLL) objects or blazar candidates of uncertain type (BCUs), are in the Northern hemisphere, and are with unknown or uncertain redshift. We report here on GTC (Gran Telescopio Canarias) spectra (in the spectral range 4100–7750 Å) of 13 BCUs and 42 BLL objects. We are able to classify the observed targets as BLL objects and each source is briefly discussed. The spectra allowed us to determine the redshift of 25 objects on the basis of emission and/or absorption lines, finding 0.05 &lt; z &lt; 0.91. Most of the emission lines detected are due to forbidden transition of [O iii] and [N ii]. The observed line luminosity is found to be lower than that of quasi-stellar objects (QSOs) at similar continuum and could be reconciled with the line–continuum luminosity relationship of QSOs if a significant beaming factor is assumed. Moreover, for five sources we found intervening absorption lines that allow to set a spectroscopic lower limit of the redshift. For the remaining 25 sources, for which the spectra are lineless, a lower limit to z is given, assuming that the host galaxies are giant ellipticals.

scholarly journals Frequency Dependence of the Parsec-scale Polarization Structures of BL Lac Objects

2001 ◽  
Vol 205 ◽  
pp. 140-141
Author(s):  
A.B. Pushkarev ◽  
D.C. Gabuzda ◽  
T.V. Cawthorne
Keyword(s):  
Line Emission ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Sky Survey ◽  
Radiation Sources ◽  
Wide Wavelength Range ◽  
Bl Lac ◽  
5 Ghz

BL Lacertae objects are active galactic nuclei with weak or undetectable line emission and strong variability in total intensity and linear polarization over a wide wavelength range from optical to radio. The radio emission and much of the optical emission is believed to be synchrotron radiation. Sources in the complete sample of BL Lac objects defined by Kühr and Schmidt (1990) have: 5 GHz fluxes of at least 1 Jy, radio spectral index α ≥ −0.5 (Sv ˜ v+α), rest frame equivalent width of the strongest emission lines less than 5 Å, and optical counterparts on the Sky Survey plates with brightness greater than 20m.

scholarly journals CONTEMPORANEOUS BROADBAND OBSERVATIONS OF THREE HIGH-REDSHIFT BL LAC OBJECTS

2016 ◽  
Vol 820 (1) ◽  
pp. 72 ◽  
Author(s):  
M. Ackermann ◽  
M. Ajello ◽  
H. An ◽  
L. Baldini ◽  
G. Barbiellini ◽  
...  
Keyword(s):  
High Redshift ◽  
Bl Lac Objects ◽  
Bl Lac

scholarly journals Accurate Positions and Some Optical Identifications for 255 Radio Sources Between Declinations +20° and ?33°

1969 ◽  
Vol 22 (2) ◽  
pp. 237 ◽  
Author(s):  
Jeannette K Merkelijn
Keyword(s):  
Radio Sources ◽  
Stellar Objects ◽  
Quasi Stellar Objects ◽  
Optical Identifications

Accurate positions have been measured at 2700 MHz for 255 sources from the Parkes catalogue between declinations +20� and -33�. The estimated accuracy in both coordinates is approximately 15N arc. For 103 of the sources, identifications are suggested using the accurate positions. Sixty-two of the sources are identified with galaxies and 41 with quasi-stellar objects.

scholarly journals New Optical Identifications from the Parkes 2700 MHz Resurvey of the ± 4° Declination Zone

1982 ◽  
Vol 35 (2) ◽  
pp. 207 ◽  
Author(s):  
Ann Savage ◽  
JG Bolton ◽  
Jenny Trett
Keyword(s):  
Radio Sources ◽  
Stellar Objects ◽  
Sky Survey ◽  
Quasi Stellar Objects ◽  
Optical Identifications

Identifications are suggested for 59 radio sources from the resurvey of declination zone �4�, 27 with galaxies and 32 with stellar objects; 19 of the latter are confirmed as quasi-stellar objects (QSOs). The identifications were made from the Palomar Sky Survey prints plus supplementary plates taken with the Palomar and U.K. Schmidt telescopes and the Anglo-Australian 3�9 m telescope.

scholarly journals A new catalogue of quasi-stellar objects

1986 ◽  
Vol 119 ◽  
pp. 51-52
Author(s):  
A. Hewitt ◽  
G. Burbidge
Keyword(s):  
Seyfert Galaxies ◽  
List Type ◽  
Type Number ◽  
Stellar Objects ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lac ◽  
Similar Information ◽  
Quasi Stellar Objects ◽  
Objective Prism

We have prepared a new catalogue of QSOs and BL Lac objects containing approximately 3400 entries. A complete update of the Hewitt-Burbidge (1980) catalogue has been made with approximately another 2000 objects with known redshifts added. The references to discovery, magnitudes, redshifts, color, spectra and polarimetry have been updated for the objects listed in 1980, and complete new references are included for the new objects. In addition to the basic optical information, the new catalogue also contains X-ray, radio and infrared information for all objects. Absorption redshifts are listed when they are available. A supplementary catalogue which is now in preparation will contain similar information for objects described variously as Seyfert galaxies, N systems and AGNs. In doubtful cases we have used the operational dividing line ƶ = 0.1. All objects with ƶ < 0.1 are put in the supplementary catalogue unless their discoverers have unambiguously defined them as QSOs. With approximately twice as many objects included it is interesting to note that: a)There are still very few genuine BL Lac objects, ∼100.b)The largest number of additions has come from identifications using the objective prism-grism techniques.

scholarly journals The Brightness and Polarization Structure of Compact Radio Sources

1988 ◽  
Vol 129 ◽  
pp. 161-162
Author(s):  
Raymond Rusk
Keyword(s):  
Position Angle ◽  
Active Galaxies ◽  
Radio Sources ◽  
Optical Polarization ◽  
Polarization Data ◽  
Core Component ◽  
Structural Position ◽  
Bl Lac Objects ◽  
The Core ◽  
Bl Lac

New VLA polarization data for 140 radio sources have been used to study the correlation between VLBI structural position angle and radio and optical polarization position angles reported in Rusk and Seaquist (1985). We confirm that there is a strong tendency, in active galaxies and quasars, for the radio E vector (of the core component) to lie normal to the VLBI structural axis. However, in BL Lac objects we find a tendency for the core radio E vector to be aligned parallel to the VLBI structural axis.

Optical Identifications for a Sample of Rexs: Search for BL Lac Objects

1996 ◽  
pp. 271-272 ◽  
Author(s):  
C. Ruscica ◽  
A. Caccianiga ◽  
T. Maccacaro ◽  
A. Wolter
Keyword(s):  
Bl Lac Objects ◽  
Bl Lac ◽  
Optical Identifications
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