scholarly journals High-Redshift Milli-Jansky Radio Galaxies

1996 ◽  
Vol 175 ◽  
pp. 581-582
Author(s):  
J. Dunlop ◽  
J. Peacock ◽  
R. Windhorst ◽  
H. Spinrad ◽  
A. Dey ◽  
...  
Keyword(s):  
Luminosity Function ◽  
High Redshift ◽  
Radio Galaxies ◽  
Elliptical Galaxies ◽  
Observational Cosmology ◽  
Redshift Distribution ◽  
Flux Limit ◽  
Formation And Evolution ◽  
Radio Luminosity Function ◽  
Radio Power

The study of radio galaxies selected at mJy flux levels has the potential to resolve two important issues in observational cosmology provided redshifts can be determined or reliably estimated for complete samples of such sources. First, the deep flux limit, combined with the shape of the radio luminosity function means that the redshift distribution of such samples provides a much more powerful test of the existence of a high-redshift cutoff for radio sources (Dunlop & Peacock 1990) than can be provided by further studies of brighter radio samples. Second, as a consequence of selection from bright radio surveys, the detailed study of galaxies at z > 2 has to date been confined to objects of extreme radio power (e.g. 4C41.17, Chambers et al. 1990; B2 0902+34, Eales et al. 1993), and it has now become clear that the ultraviolet-infrared properties of such sources are strongly contaminated by processes connected to the AGN (Eales & Rawlings 1993; Dunlop & Peacock 1993). Being 100-1000 times less radio luminous than these extreme sources, mJy radio galaxies at comparable redshifts should provide much more representative probes of the formation and evolution of elliptical galaxies in general.

scholarly journals High Redshift Radio Galaxies

1996 ◽  
Vol 168 ◽  
pp. 79-87
Author(s):  
James S. Dunlop
Keyword(s):  
High Redshift ◽  
Spatial Association ◽  
Radio Galaxies ◽  
Elliptical Galaxies ◽  
Powerful Radio ◽  
High Redshift Galaxies ◽  
3 Dimensional ◽  
Baryonic Mass ◽  
Radio Power

The potentially important role of jet-cloud interactions in determining the appearance of high-redshift radio galaxies is discussed and investigated via new 3-dimensional simulations of off-axis jet-cloud collisions. The results indicate that the most powerful radio sources are likely to be observed during or shortly after a jet-cloud interaction, and that such interactions can explain both the radio structures and the spatial association between optical and radio light found in powerful radio galaxies at high redshift. It is argued that, due to the radio-power dependence of such complicating effects, the optical-infrared colours and morphologies of very radio-luminous high-redshift galaxies can tell us essentially nothing about their evolutionary state. Either one must study much less radio-luminous sources in which the AGN-induced contamination is minimised, or one must attempt to determine what fraction of the baryonic mass of the radio galaxy has been converted into stars at the epoch of observation. Recent observations aimed at performing the latter experiment on two well-known high-redshift radio galaxies (4C 41.17 & B2 0902+34) are described. It is concluded that at present there exists no clear evidence that either of these famous galaxies is ‘primæval’; on the contrary, the continued low-dispersion of the infrared Hubble diagram atz> 2 points toward a much higher redshift of formation for elliptical galaxies.

scholarly journals Feedback from AGN: The Kinetic/Radio Luminosity Function

2009 ◽  
Vol 5 (S267) ◽  
pp. 402-402
Author(s):  
Gabriele Melini ◽  
Fabio La Franca ◽  
Fabrizio Fiore
Keyword(s):  
Galaxy Formation ◽  
Probability Distribution Function ◽  
Luminosity Function ◽  
Complete Sample ◽  
X Ray ◽  
Galaxy Formation And Evolution ◽  
Formation And Evolution ◽  
Radio Luminosity Function ◽  
Radio Power ◽  
Good Agreement

We have measured the probability distribution function of the ratio RX = log L1.4/LX, where L1.4/LX = ν Lν(1.4 GHz)/LX(2–10 keV), between the 1.4 GHz and the unabsorbed 2–10 keV luminosities and its dependence on LX and z. We have used a complete sample of ~1800 hard X-ray selected AGN, observed in the 1.4 GHz band, cross-correlated in order to exclude FR II-type objects, and thus obtain a contemporaneous measure of the radio and X-ray emission. The distribution P(RX|LX,z) is shown in Figure 1. Convolution of the distribution P(RX|LX,z) with the 2–10 keV X-ray AGN luminosity function from La Franca et al. (2005) and the relations between radio power and kinetic energy from Best et al. (2006) and Willott et al. (1999) allows us to derive the AGN kinetic power and its evolution. As shown in Figure 1, our results are in good agreement with the predictions of the most recent models of galaxy formation and evolution (e.g., Croton et al. 2006), where AGN radio feedback is required to quench the star formation.

The intermediate-power population of radio galaxies: morphologies and interactions

2018 ◽  
Vol 14 (A30) ◽  
pp. 90-93
Author(s):  
Diana M. Worrall ◽  
Ryan T. Duffy ◽  
Mark Birkinshaw
Keyword(s):  
Luminosity Function ◽  
Full Range ◽  
Radio Galaxies ◽  
Power Sources ◽  
X Ray ◽  
Power Injection ◽  
Work Done ◽  
The Universe ◽  
Radio Luminosity Function ◽  
Radio Power

AbstractRadio galaxies of intermediate power dominate the radio-power injection in the Universe as a whole, due to the break in the radio luminosity function, and so are of special interest. The population spans FR I, FR II, and hybrid morphologies, resides in a full range of environmental richness, and sources of all ages are amenable to study. We describe structures and interactions, with emphasis on sources with deep high-resolution Chandra X-ray data. As compared with low-power sources there is evidence that the physics changes, and the work done in driving shocks can exceed that in evacuating cavities. A range of morphologies and phenomena is identified.

scholarly journals Optical and IR Properties of Radio Galaxies as a Function of their Radio Power

1996 ◽  
Vol 171 ◽  
pp. 414-414
Author(s):  
L. Maxfield ◽  
S.G. Djorgovski ◽  
D. Thompson ◽  
M.A. Pahre ◽  
R.R. de Carvalho ◽  
...  
Keyword(s):  
High Redshift ◽  
Spectroscopic Properties ◽  
Radio Galaxies ◽  
Active Nucleus ◽  
Data Set ◽  
Uv Emission ◽  
Two Samples ◽  
Order Of Magnitude ◽  
Ir Photometry ◽  
Radio Power

We compare optical and infrared photometric and spectroscopic properties of high-redshift radio galaxies from the 3CR and B3 surveys. At a given redshift and a fixed restframe frequency, the two samples differ on average by an order of magnitude in radio power, thus providing a fair baseline in radio powerfor a range of redshifts. We present new optical and IR photometry and spectrosopy for a number of B3 sources. We combine these data with the existing corresponding information on B3 and 3CR sources, in order to explore different correlations of source properties with redshift, and among themselves. B3 sources follow the same trend as 3CR's in the K band Hubble diagram, although they do seem to be slightly fainter on average at a given redshift. This trend is slightly more prominent in the Gunn r band. This suggests that some fraction of the observed light in the r and K bands is contributed by an active nucleus, which also powers the radio lobes. The B3's also tend to have lower emission line luminosities than 3CR's at any given redshift, suggesting that there may be a correlation between line luminosity and radio power. Such a correlation is clearly seen and is followed by both samples. It suggests that the UV emission lines are largely powered by the active nucleus, ostensibly a hidden quasar, which is also responsible for the radio emission. We also examine the behavior of the optical and radio PA alignments for the combined B3+3CR data set. We find that high-power and high-redshift subsamples for both B3's and 3CR's show the alignments more prominently, but we still cannot tell which of these variables dominates this effect. This work was supported in part by the NSF PYI award AST-9157412, and the Bressler Foundation.

scholarly journals Radio Galaxies as Large-Scale Cosmological Probes

1988 ◽  
Vol 130 ◽  
pp. 579-579
Author(s):  
J.A. Peacock ◽  
L. Miller ◽  
C.A. Collins ◽  
D. Nicholson ◽  
S. J. Lilly
Keyword(s):  
Large Scale ◽  
A Priori ◽  
Radio Galaxies ◽  
Elliptical Galaxies ◽  
Central Component ◽  
Selection Effects ◽  
Core Radius ◽  
Point Correlation ◽  
Point Correlation Function ◽  
Radio Power

We are working on an all-sky sample of radio-selected elliptical galaxies to provide a powerful probe of clustering & streaming velocities on 10–100 Mpc scales. Our eventual sample will have the limits (i) S>0.5 Jy at 1.4 GHz; (ii) 0.01<z<0.1; (iii) |b| >15°; about 400 galaxies satisfy these criteria. We are pursuing an optical programme to obtain (i) B & I CCD frames for all galaxies; (ii) spectra for the galaxies without accurate redshifts; this is now about 30% complete. Accurate optical luminosity indicators exist for radio galaxies, without needing to measure velocity dispersions (using the correlations with optical core radius and radio central-component luminosity: Hoessel 1980: Ap. J. 241, 493; Fabbiano et al. 1984: Ap. J. 277, 115). We therefore expect to provide an accurate test of the Rubin-Ford effect, and to extend such studies to higher redshift. We also have a preliminary result for the 3D two-point correlation function of radio galaxies (see Figure). This strong clustering signal is seen only from galaxies in the decade of radio power below the Fanaroff-Riley division. These objects are known a priori to lie in cluster environments of average Abell richness 0 (Longair & Seldner 1979: MNRAS 189, 433). This result therefore provides confirmation of a trend of clustering with richness independent of optical selection effects in choosing a cluster sample.

Massive Elliptical Galaxies at High Redshift: NICMOS Imaging ofz ≈ 1 Radio Galaxies

2003 ◽  
Vol 585 (1) ◽  
pp. 90-111 ◽  
Author(s):  
Andrew W. Zirm ◽  
Mark Dickinson ◽  
Arjun Dey
Keyword(s):  
High Redshift ◽  
Radio Galaxies ◽  
Elliptical Galaxies

scholarly journals Morphological Evolution in High‐Redshift Radio Galaxies and the Formation of Giant Elliptical Galaxies

1998 ◽  
Vol 502 (2) ◽  
pp. 614-629 ◽  
Author(s):  
Wil J. M. van Breugel ◽  
S. A. Stanford ◽  
Hyron Spinrad ◽  
Daniel Stern ◽  
James R. Graham
Keyword(s):  
Morphological Evolution ◽  
High Redshift ◽  
Radio Galaxies ◽  
Elliptical Galaxies

scholarly journals The radio luminosity function of the NEP distant cluster radio galaxies

2006 ◽  
Vol 446 (1) ◽  
pp. 97-111 ◽  
Author(s):  
M. Branchesi ◽  
I. M. Gioia ◽  
C. Fanti ◽  
R. Fanti ◽  
R. Perley
Keyword(s):  
Luminosity Function ◽  
Radio Galaxies ◽  
Radio Luminosity ◽  
Distant Cluster ◽  
Radio Luminosity Function

scholarly journals Radio Source Evolution Derived from Low Frequency Surveys

2002 ◽  
Vol 199 ◽  
pp. 50-53
Author(s):  
C.A. Jackson ◽  
J.V. Wall
Keyword(s):  
Radio Source ◽  
Luminosity Function ◽  
Low Frequency ◽  
Radio Galaxies ◽  
Parametric Models ◽  
Radio Luminosity ◽  
Space Density ◽  
Radio Data ◽  
Radio Luminosity Function

We find simple parametric models to describe the space density evolution of radio-loud AGN, treating FRI and FRII radio galaxies separately as the two parent populations in our dual-population unified scheme. In this we use low frequency radio data (v < 500 MHz), where radio samples are unbiased by Doppler beaming. Incorporated into this latest analysis is a new determination of the local radio luminosity function at 1.4 GHz from galaxies common to both the 2dFGRS and NVSS surveys.

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