arXiv:astro-ph/0311536v1 24 Nov 2003 on h infiateouinudroeb h C of between ac- ICM cluster into the host take by radio-source to undergone a important evolution in significant be are the will objects count it sufficient though once archive, X-ray the the from radio-source-related constraints and AGN- by components. emission X-ray contamination the the and of of because small reliable not generally generally is 1999) are work Worrall sizes & sample (Hardcastle but cluster-related unified be as- of emission, to extended predictions sumed of the observations test X-ray using to models made at- Some been measure. clustering have to the hard tempts as are sources classified the these of at environments objects high and low- at ) few their best radio-loud are work as (there models such unified redshift objects, classical identical. of the statistically However, be classes should two environments, clustering the radio- isotropic 1989) and of 1987, Barthel properties radio 1987, (Scheuer powerful quasars for loud models unified In Introduction 1. fe eerdt as to here- referred function, - covariance after the tradi- spatial of -galaxy the amplitude or rˆole for the galaxy calculating important of an method still tional is there meantime, htslcini oeta n pia le sdsrbeto recognised desirable is is filter it optical one Although than Lilly more 1993). in & selection Ellingson Hill that 1991; & Green & Yee & Miller 1991; Yates, Yee 1988; Ellingson, Peacock 1989; & Peacock Prestage 1987; Green & B DI ilb netdb adlater) hand by inserted be will (DOI: Astrophysics & Astronomy gg e words. Key predict. Abstract. 2018 17, December of Version Aven Tyndall Bristol, of University Physics, of Department aaisadqaasaesaitclycnitn ntere the in consistent low-excitatio statistically environments. of are richer properties significantly quasars in the and lie cl galaxies of two to result the tend which for a ple, models as unified simple mainly of arises predictions the betwe to difference tion environmental systematic a suggested have eiie:Teevrnet flwectto ai galax radio low-excitation of environments The revisited: Chandra eetmaueet fteglx lseigenvironments clustering galaxy the of measurements Recent aais cie–glxe:qaas eea aais c galaxies: – general quasars: galaxies: – active galaxies: B gg hudpoiesgicnl better significantly provide should eg ogi ede 99 Yee 1979; Seldner & Longair (e.g. aucitn.0605 no. manuscript z ∼ n nfidmodels unified and n .I the In 0. and 1 ROSAT eerhNote Research atnJ Hardcastle J. Martin -based fte r nfc n3R.Teeet fti isare bias this of effects The 3CR). in fact in are fraction their a them of only of basis whereas the emission, on extended themselves low-frequency objects would 3CR emis- they been extended (otherwise have sample in all comparison radio-luminous 3CR quasars the as YE93 as the sion general that in is in not result found were this were im- to An galaxies objection quasar. mediate radio any the than environments of richer number significantly a that sense odqaascmie yYe&Elnsn(93 here- 0 (1993: range radio- redshift Ellingson of the & sample in Yee a YE93) by of after compiled those quasars with consistent loud not were ies ag 0 range edt i npo niomns hyotie h sur- the obtained They the environments. that result poor prising in also lie would redshifts to these tend at in unified-model galaxies the radio located test that prediction are to aimed quasars HESR environments. radio-loud rich low-redshift, shown few lobe- had (1987) or that Green galaxies & Yee radio quasars. core-dominated FRII-type or luminous all almost are ananal opeestof set ob- cross- complete to able nearly and sources. were a they collating radio literature, tain clustering and the 1985) from observations, the data al. calibrating new of et making study (Spinrad By 3CR systematic of large properties a out carried environ- the source. of of measure classes statistical different a of provide ments to able be to ciego ttsisa ihrdhfs(are l 2003), al. simple et (Barr redshifts redshifts lower high at at statistics good achive sitrne0 range dshift h niomna rpriso ihectto radio high-excitation of properties environmental The e rso S T,U ([email protected]) UK 1TL, BS8 Bristol ue, nrdoglxe n ai-odqaas ncontradic- in quasars, radio-loud and galaxies radio en ai aaisicue nterdoglx sam- radio-galaxy the in included galaxies radio n eetyHrae ta.(01 eefe ER have HESR) hereafter (2001: al. et Harvanek Recently se fojc.Iso htteaprn difference apparent the that show I object. of asses . 15 utr:gnrl–rdocnium galaxies continuum: radio – general lusters: < z < ruditreit-esitrdosources radio intermediate-redshift around . 15 < z < 0 . 5 C bet nti esitrange redshift this in objects 3CR 65. B gg 0 . ,a nfidmdl would models unified as 4, B auso hi C ai galax- radio 3CR their of values gg eemntosse likely seem determinations B gg ausi h redshift the in values . 15 < z < eebr1,2018 17, December 0 . ,i the in 4, ies 2 Martin J. Hardcastle: Bgg revisited hard to quantify, but since (for equal jet powers and source Table 1. Supplementary emission-line classifications for ages) simple radio-galaxy physics suggests that a more lu- HESR sources minous object will lie in a richer environment, it might tend to produce a difference in the sense of the one ob- Source Emission line classification Reference served by HESR. In what follows I shall ignore this po- in HESR adopted tential problem and concentrate instead on the effects on 3C 28 – E 1 HESR’s conclusions of using a more sophisticated variant 3C 48 – B 2 of the unified model. 3C 49 – N 3 3C 67 – B 4 2. Unification at low redshifts and the 3C 93.1 – N 3 3C 99 – N 3 low-excitation objects 3C 196.1 – N 3 At low redshifts (or, more generally, low luminosities) 3C 234 N/B? N 5 the simple unified model of Barthel (1989) breaks down, 3C 268.3 – B? 9 3C 277.1 – B 6 most obviously because of the absence of low-redshift 3C 288 – E 7 FRII quasars. I have argued elsewhere (Hardcastle et al. 3C 295 – N 8 1998) that the broad-line radio galaxies (BLRG) take the 3C 299 – N 3 place of quasars at low redshifts/luminosities, although 3C 303.1 – N 3 that does not rule out the possibility that more lumi- 3C 346 – E 3 nous BLRG are objects intermediate in viewing angle be- 3C 455 – B 6 tween quasars and narrow-line radio galaxies (NLRG) (e.g. Dennett-Thorpe et al. 2000). However, low-excitation ra- Emission-line types here are E (low-excitation), N (high- dio galaxies (LERG) (Hine & Longair 1979; Laing et al. excitation, narrow-line) and B (broad-line). References are as 1994), which are a significant population at low FRII lu- follows: (1) Schmidt (1965) (2) Greenstein & Schmidt (1964) minosities, cannot be unified with either BLRG or quasars (3) Spinrad et al. (1985) (4) Laing et al. (1994) (5) See if the narrow-line emission is isotropic. Instead, it has been Hardcastle et al. (1997) for the argument for assigning this suggested (Barthel 1994, Laing et al. 1994), that they form to the N class (6) Quasar, assumed broad-line (7) Smith & a separate population, possibly unified at small angles to Spinrad (1980) (8) Minkowski (1960) (9) Laing & Riley, in the line of sight with FRII-like BL Lac objects. They have preparation. other anomalous properties: Hardcastle et al. (1998) noted that the LERG in their z < 0.3 3CR/3CRR sample were on average significantly smaller than the high-excitation objects, and that they included a number of objects with prominent jets and relaxed or absent hotspot structure. Hardcastle & Worrall (1999) found that the LERG in their ROSAT-observed subsample of 3CRR tended to have relatively luminous X-ray environments, whereas at least some of the NLRG at similar redshifts were in poorer en- vironments. This motivates a re-analysis of the results of HESR taking into account the emission-line type of the radio galaxies.

3. Data and analysis The data for 3CR objects, including the emission-line classifications, are taken from HESR, with emission-line classifications supplemented by data from the literature (Table 1). HESR took most of their emission-line classi- fications from Jackson & Rawlings (1997). Lacking new spectroscopic observations, I have classified objects that were not classified in Jackson & Rawlings mostly on the basis of qualitative statements in the literature, such as Fig. 1. B .

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