scholarly journals Luminosity Selection Effects and Linear Size Evolution in the Quasar/Galaxy Unification Scheme

1998 ◽  
Vol 51 (1) ◽  
pp. 143
Author(s):  
A. A. Ubachukwu ◽  
J. N. Ogwo
Keyword(s):  
High Redshift ◽  
Radio Galaxies ◽  
Linear Size ◽  
Selection Effects ◽  
Size Evolution

The implications of linear size evolution and luminosity selection effects in the quasar/galaxy unification scheme have been investigated. We show that both radio galaxies and quasars undergo similar size evolution above some low redshift cut-off zc = 0·2–0·3. However, this evolution can be attributed largely to the strong luminosity selection effects present in the sample. We also observe that there is a marked difference in the luminosity–redshift slope between low and high redshift sources, which may be responsible for the conflicting results in the literature as to whether or not radio galaxies and quasars have similar linear size versus luminosity/redshift relationships. Our present result seems consistent with the quasar/galaxy unification scheme in which the two classes of object are expected to have similar linear size versus luminosity/redshift relationships.

A direct determination of linear-size evolution of elliptical radio galaxies

Nature ◽  
1987 ◽  
Vol 328 (6130) ◽  
pp. 500-501 ◽  
Author(s):  
M. J. A. Oort ◽  
P. Katgert ◽  
R. A. Windhorst
Keyword(s):  
Direct Determination ◽  
Radio Galaxies ◽  
Linear Size ◽  
Size Evolution

scholarly journals Galaxy Size Evolution at High Redshift and Surface Brightness Selection Effects: Constraints from the Hubble Ultra Deep Field

2004 ◽  
Vol 611 (1) ◽  
pp. L1-L4 ◽  
Author(s):  
R. J. Bouwens ◽  
G. D. Illingworth ◽  
J. P. Blakeslee ◽  
T. J. Broadhurst ◽  
M. Franx
Keyword(s):  
Surface Brightness ◽  
High Redshift ◽  
Selection Effects ◽  
Size Evolution ◽  
Hubble Ultra Deep Field

scholarly journals On the Unification of Radio Galaxies and Quasars

1994 ◽  
Vol 159 ◽  
pp. 501-501
Author(s):  
Krzysztof T. Chyzy
Keyword(s):  
Radio Galaxies ◽  
Linear Size ◽  
Expansion Velocity ◽  
Evolutionary Patterns ◽  
Consistency Test ◽  
Radio Structure ◽  
Size Evolution ◽  
The Asymmetry ◽  
Asymmetry Parameters ◽  
Independent Parameters

A comparison of the projected linear size evolution of extended quasars and radio galaxies are often used as a test of the radio galaxy - quasar unification schemes. If both the mentioned categories of radio sources differ to an observer only due to the various viewing directions, then their radio linear sizes are expected to evolve with redshift in the same way (Gopal-Krishna & Kulkarni, 1992). However, apart from the simplest linear size parameter L we can still determine two independent parameters assessing the asymmetry of the radio structure: Q - the arm lengths ratio; M - misalignment, which measures the apparent bending, and defined as the ratio of the displacement of the core from the source axis to the linear size. The asymmetry parameters Q and M can also be a powerful tool in the consistency test for the orientation based unification scheme as their evolutionary patterns should be the same for radio galaxies and quasars. Contrary to the linear size, they are not sensitive to the simple homological rescaling of the whole structure and hence to the age or expansion velocity of the structure.

scholarly journals Implications of a Nonzero Cosmological Constant and Luminosity Selection Effects on Cosmological Tests

1998 ◽  
Vol 51 (3) ◽  
pp. 585 ◽  
Author(s):  
A. A. Ubachukwu
Keyword(s):  
Cosmological Constant ◽  
The Other ◽  
Linear Size ◽  
Low Density ◽  
Selection Effects ◽  
Flat Universe ◽  
Size Evolution ◽  
Significant Difference ◽  
Cosmological Tests ◽  
The Universe

This paper examines the implications of a nonzero cosmological constant Λ 0 on the amount of linear size evolution and the luminosity selection effects usually required in the interpretation of the angular diameter–redshift (θ–z) test. This is based on three typical cases chosen on various plausible assumptions which can be made concerning the contribution of Λ 0 to the density of the universe (parametrised by ?0). The results show that a fairly strong linear size evolution will be required to interpret the θ–z data of extended steep spectrum quasars for all three cases, if luminosity effects are neglected. However, this evolution is significantly steeper in a matter-dominated universe with ?M = ?0 = 1 than in both the flat universe with ?Λ = 0·8, ?M = 0·2 and an open universe with ?M = 0·2, Λ = 0. Furthermore, when the luminosity selection effects present in the sample are considered, a milder size evolution is obtained for the ?M = 1, ?Λ = 0 model while little or no size evolution is found for the other two cases. There is therefore no significant difference in our results for an open low density universe with ?Λ = 0 and a flat universe dominated by ?Λ predicted by inflation. The present results therefore imply that an open low density universe with ?M = 0·2 and ?Λ = 0 is compatible with an inflationary model of the universe with ?M = 0·2 and ?Λ = 0 · 8. This leads to a contradiction since the universe cannot be open and spatially closed at the same time (the existence of one should preclude the other).

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 Linear Size Evolution and Luminosity Selection Effects in Quasars

1997 ◽  
Vol 50 (5) ◽  
pp. 967
Author(s):  
A. A. Ubachukwu
Keyword(s):  
Linear Size ◽  
Selection Effects ◽  
Large Sample ◽  
Size Evolution

We have quantitatively estimated the amount of luminosity selection effects present in the observed linear size-redshift data for a large sample of extended steep spectrum quasars. We show that ~90% of the observed dependence of sizes of quasars on redshift can be interpreted in terms of luminosity selection effects alone. This gives quantitative support to earlier results which show that little or no intrinsic linear size evolution appears to be occurring among quasars.

The Quest for Relics: Massive compact galaxies in the local Universe

2019 ◽  
Vol 15 (S359) ◽  
pp. 441-443
Author(s):  
F. S. Lohmann ◽  
A. Schnorr-Müller ◽  
M. Trevisan ◽  
R. Riffel ◽  
N. Mallmann ◽  
...  
Keyword(s):  
High Redshift ◽  
Control Sample ◽  
Sloan Digital Sky Survey ◽  
Integral Field Spectroscopy ◽  
Sky Survey ◽  
Size Evolution ◽  
Compact Galaxies ◽  
Minor Mergers ◽  
Significant Size ◽  
Integral Field

AbstractObservations at high redshift reveal that a population of massive, quiescent galaxies (called red nuggets) already existed 10 Gyr ago. These objects undergo a significant size evolution over time, likely due to minor mergers. In this work we present an analysis of local massive compact galaxies to assess if their properties are consistent with what is expected for unevolved red nuggets (relic galaxies). Using integral field spectroscopy (IFS) data from the MaNGA survey from the Sloan Digital Sky Survey (SDSS), we characterized the kinematics and properties of stellar populations of massive compact galaxies, and find that these objects exhibit, on average, a higher rotational support than a control sample of average sized early-type galaxies. This is in agreement with a scenario in which these objects have a quiet accretion history, rendering them candidates for relic galaxies.

scholarly journals Lyα excess in high-redshift radio galaxies: a signature of star formation★

2007 ◽  
Vol 375 (4) ◽  
pp. 1299-1310 ◽  
Author(s):  
M. Villar-Martín ◽  
A. Humphrey ◽  
C. De Breuck ◽  
R. Fosbury ◽  
L. Binette ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Radio Galaxies

scholarly journals Spatially resolved studies of extragalactic jets in high redshift radio galaxies

2014 ◽  
Vol 10 (S313) ◽  
pp. 231-235
Author(s):  
Leah K. Morabito ◽  
Adam Deller ◽  
J. B. R. Oonk ◽  
Huub Röttgering ◽  
George Miley
Keyword(s):  
High Redshift ◽  
Low Frequency ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Spatially Resolved ◽  
Long Baseline ◽  
Early Results ◽  
Spectrum Radio ◽  
Extragalactic Jets ◽  
Frequency Survey

AbstractThe correlation between radio spectral steepness and redshift has been successfully used to find high redshift (z ⩾ 2) radio galaxies, but the origin of this relation is unknown. The ultra-steep spectra of high-z radio sources make them ideally suited for studies with the Low Band Antenna of the new Low Frequency Array, which covers 10–80 MHz and has baselines up to about 1300 km. As part of an ongoing survey, we use the longest baselines to map the low-frequency (< 70 MHz) spatial distributions along the jets of 5 bright extended steep spectrum high-z radio sources. From this, we will determine whether the spectra change over these spatially resolved sources, thereby constraining particle acceleration processes. We present early results from our low-frequency survey of ultra-steep spectrum radio galaxies. The first low frequency long baseline images of these objects are presented.

Sign in / Sign up

Export Citation Format

Share Document