The origin of the UV excess in powerful radio galaxies spectroscopy and polarimetry of a co

The origin of the UV excess in powerful radio galaxies spectroscopy and polarimetry of a co
The origin of the UV excess in powerful radio galaxies spectroscopy and polarimetry of a co

a r X i v :a s t r o -p h /0201391v 1 23 J a n 2002

Mon.Not.R.Astron.Soc.000,000–000(0000)Printed 1February 2008

(MN L A T E X style ?le v1.4)

The origin of the UV excess in powerful radio galaxies:

spectroscopy and polarimetry of a complete sample of intermediate redshift radio galaxies

C.Tadhunter 1,R.Dickson 2,R.Morganti 3,T.G.Robinson 1,K.Wills 1,M.Villar-Martin 4,M.Hughes 4

1Department

of Physics and Astronomy,University of She?eld,Houns?eld Road,She?eld,S37RH,UK 2Jodrell

Bank Observatory,University of Manchester,Maccles?eld,Cheshire,SK119DL.

3Netherlands Foundation for Research in Astronomy,Postbus 2,7990AA Dwingeloo,The Netherlands 4Division of Physical Sciences,University of Hertfordshire,Herts

ABSTRACT

We present spectroscopic and polarimetric observations of a complete,optically un-biased sample of 2Jy radio galaxies at intermediate redshifts (0.1510%level.Careful measurement and modelling of our spectra have allowed us to quantify the contributions of other components to the UV excess.We show that nebular continuum (present in all objects at the 3—40%level),direct AGN light (signi?cant in 40%of objects),and young stellar populations (signi?cant in 15—50%of objects)all make important contributions to the UV continuum in the population of powerful radio galaxies.These results serve to emphasise the multi-component nature of the UV continuum in radio galaxies.The results also point to an interesting link betweeen the optical/UV and far-IR properties of our sample objects,in the sense that the objects with the clearest evidence for optical/UV starburst activity are also the most luminous at far-IR wavelengths.This supports the idea that the cooler dust components in radio galaxies are heated by starbursts rather than by AGN.Key words:galaxies:active –galaxies:individual –galaxies:emission lines –quasars:general

1INTRODUCTION

Given the large look back times encompassed by the most distant radio sources,one motivation for studying such ob-jects is their potential use as probes of the formation and evolution of giant early-type galaxies in the early universe.However,all studies aimed at using radio galaxies in this way have to face the problem of distinguishing the e?ects of the AGN and radio jet activity from genuine signs of galaxy evolution.This problem is particularly acute in the case of studies of the continuum https://www.360docs.net/doc/d330907.html,pared with normal early-type galaxies,powerful radio galaxies can show contin-uum excesses at both optical/UV (e.g.Lilly &Longair 1984,Smith &Heckman 1989)and far-IR/sub-mm wavelengths

(Golombek et al.1988,Heckman et al.1994,Archibald et

al.2001).Therefore,a key issue for these objects is whether these continuum excesses are a consequence of recent star formation which may be linked to evolutionary processes in the early-type host galaxies or,given that these objects con-tain powerful AGN and radio jets,a direct consequence of the activity.

The presence of a UV excess in the continua of radio galaxies was ?rst demonstrated by the photometric obser-vations of samples of high redshift (z >0.5)radio galaxies in the early 1980’s.These observations showed evidence for bluer optical-IR colours than expected for non-evolving or passively evolving elliptical galaxies (e.g.Lilly &Longair

c

0000RAS

2Tadhunter et al.

1984).Initially,the UV excess was interpreted in terms of bursts of star formation,possibly linked to the evolution of the host galaxies.This interpretation is attractive in the light of morphological studies which show evidence for recent mergers in a large fraction of powerful radio galaxies at low redshifts(Heckman et al.1986);and merger-induced star formation has been suggested as a possible triggering mech-anism(Smith&Heckman1989).However,given the degree of nuclear and extranuclear activity likely to be present in most powerful radio galaxies,some caution is required in deducing starburst properties purely on the basis of broad-band photometric measurements.

Recognising the potential AGN contribution,an alter-native explanation for the UV excess was stimulated by the development of the anisotropy-based uni?ed schemes in the late1980’s(e.g.Barthel1989).In the frame of such schemes the UV excesses can be explained in terms of light scat-tered from broad radiation cones of the hidden quasar nuclei (Tadhunter et al.1988,Fabian1989).Early polarimetric at-tempts to test this model proved successful in the sense that they showed the high degrees of linear polarization charac-teristic of anisotropic scattering in the UV continua of sev-eral high redshift radio galaxies(e.g.Tadhunter et al.1992, Cimatti et al.1993,Vernet et al.2001).However,while these observations demonstrate that scattered quasar light is an important component of the UV continuum in some sources, they do not establish the signi?cance of the scattered com-ponent in the general population of powerful radio galaxies. Because polarimetric observations of faint objects are di?-cult,previous studies have tended to be biased towards the brightest,most spectacular objects in a given redshift range. There are also redshift-dependent biases which arise because optical(mostly V-band)observations sample the rest-frame UV in the high redshift objects—with minimal dilution by the old stellar populations of the host galaxies—but sam-ple the rest-frame optical in the low redshift objects—with substantial dilution by the old stellar populations.The im-portance of this observational selection e?ect is emphasised by multi-wavelength polarimetric observations of individual sources which show a sharp decline in the measured polar-ization between the UV and the optical(Tadhunter et al. 1996,Ogle et al.1997,Tran et al.1998).

In addition to the scattered component,detailed ob-servations over the last decade have revealed the presence of two further activity-related components which can con-tribute to the UV excess.These are:the nebular continuum emitted by the extended emission line nebulae(Dickson et al.1995);and direct AGN light emitted by weak,or partially extinguished,quasars in the nuclei of the galaxies(Shaw et al.1995).The nebular continuum is likely to be particularly signi?cant in regions where the emission lines have large equivalent widths,including the extended emission line neb-ulae around powerful radio galaxies.In contrast,the direct AGN component will only be important in the nuclear re-gions of the sources.

Most recently,events have turned full circle with the spectroscopic detection of young stellar populations in at least some powerful radio galaxies(e.g.Tadhunter et al. 1996,Melnick et al.1997).The detection of this component is consistent with the early interpretation of the UV excess in terms of starbursts associated with the evolution of the host galaxies(Lilly&Longair1984).Unfortunately,apart from cases in which it dominates the optical continuum(e.g. Miller1981),the starburst component is notoriously di?cult to detect at optical wavelengths.Its presence can be masked by the light of the old stellar populations in the bulges of the host galaxies,by the various activity-related continuum components noted above,and by emission lines which can contaminate the absorption features characteristic of young stars.This is illustrated by the case of3C321which shows polarimetric evidence for a signi?cant scattered quasar com-ponent,but also shows evidence for a starburst component in the form of a Balmer break and Balmer absorption fea-tures(Tadhunter et al.1996,Robinson et al.2000).It is notable that the starburst component in3C321only came to light through detailed modelling of the optical/UV con-tinuum using a combination of spectrophotometry and spec-tropolarimetry measurements.

Given the complex circum-nuclear environments of powerful radio galaxies revealed by recent HST imaging studies(e.g.Jackson,Tadhunter&Sparks1998),it is not surprising that no single mechanism is responsible for the UV excess.Observations of individual sources demonstrate the presence of at least four UV-emitting components that can contribute to the UV excess:scattered AGN light,direct AGN light,nebular continuum,and the light of young stellar populations.However,the relative importance of these com-ponents,and particularly the importance of any starburst component,is not clear from the previously published data. In this paper we attempt to remedy this situation by combin-ing spectroscopic and polarimetric observations to quantify the contributions of the various UV-emitting components in a complete,optically unbiased sample of powerful2Jy radio galaxies at intermediate redshifts(0.15

Throughout this paper we assume a Hubble constant of H0=50km s?1Mpc?1and a deceleration parameter of q0=0.

2SAMPLE SELECTION

The objects included in this study comprise radio galaxies selected from the Tadhunter et al.(1993)complete sample of2Jy radio sources with redshifts z<0.7and declina-tionsδ<+10,which is itself a subsample of the Wall and Peacock(1985)sample of radio sources with?ux densities greater than2Jy at2.7GHz.As discussed in Tadhunter et al.(1993,1998)the z<0.7sample has a high level of com-pleteness.Low S/N optical spectra and identi?cations for all the z<0.7sample are presented in Tadhunter et al.(1993) and di Serego Alighieri et al.(1994);radio maps for this sam-ple are presented in Morganti et al.(1993,1999);and X-ray observations are presented in Siebert et al.(1996).Discus-sion of the radio observations in the context of the uni?ed schemes can be found in Morganti et al.(1995,1997),while a discussion of the nature of the correlations between radio and optical emission line properties of the z<0.7sample is presented in Tadhunter et al.(1998).

Although in section4below we will consider the UV excess in the z<0.7sample of Tadhunter et al.1993as

c 0000RAS,MNRAS000,000–000

The UV Continuum Excess in Radio Galaxies3 Object Other name z Radio Optical

Morph.Spect.0023—2622/7/93 1.7/2270900(R+B)

0035—0221/7/93 1.4/2270900(R)600(B)

0038+0922/10/95 1.7/5270900(B)

0039—4423/7/93 1.5/2270900(R)1200(B)

0105—1623/7/93 1.5/2270900(B+R)

0117—1523/7/93 1.5/2270900(B+R)

0235—1920/10/95 1.5/52702×900(B)

20/10/95 1.5/5270600(B)

0252—7121/7/94 1.5/5270600(B)

21/7/94 1.5/5270900(R)

0347+0522/10/95 1.5/5270600(B)

22/10/95 1.5/5270300(R)

0409—7522/10/95 1.4/2208700(B)

22/10/95 1.4/2208600(R)

1306—0923/7/93 1.3/2270900(R+B)

12/7/94 1.8/2270900(R+B)

1547—7920/7/93 1.2/2270900(R+B)

22/7/93 1.3/2270900(B)

23/7/93 1.2/2270900(B)

1549—7912/7/94 1.9/52701200(B)

1602+0130/7/92 1.5/1.6322×1200(R)

30/7/92 1.5/2321200(R)

1648+0512/07/94 1.6/2300900(R+B)

1932—4622/7/93 1.7/2270900(R+B)

23/7/93 1.5/2270600(R+B)

1934—6311/7/94 2.2/22701200(B)

1938—1522/7/93 1.3/2211900(R+B)

2135—2023/7/93 1.5/22701200(B)

30/7/92 1.9/1.63431200(R)

30/7/92 1.9/2.03433×1200(R+B)

2211—1721/10/95 1.1/2225900(B)

2250—4120/7/93 1.9/22702×1200(B)

20/7/93 1.9/2270900(R)

22/7/93 1.6/22701200(B)

2314+0322/7/93 1.6/22701200(B)

22/7/93 1.6/2270600(R)

Table2.Observational details of the spectroscopic observations

for the objects in Table1.Column3lists the seeing FWHM(S)

and slit width(W)in arcseconds for the observations.Column4

lists the position angle of the slit for each observation.Column5

gives the integration time in seconds for each observation.All of

the southern sample of radio galaxies were observed using EFOSC

with the R300and B300gratings,with the exception of1602+01

(3C327.1)which was observed with the red arm of the ISIS spec-

trograph on the4.2m WHT telescope(30/7/92),and2135-20,

which was observed with the B300grating of EFOSC(23/7/93

run)and with both the red and blue arms of ISIS on the WHT

telescope.

erties,while for PKS1648+05and PKS2211-17it was felt

that,considering of the lack of emission line activity,it was

unlikely that any UV excess could be due to a polarized

(scattered AGN)component.Failure to observe these three

objects does not signi?cantly a?ect our conclusions.

The key advantages of this survey for studying the UV

excess are:(a)we have both polarimetric and spectroscopic

observations for the overwhelming majority of the objects

in Table1,so our survey is not biased towards the bright-

est,most spectacular objects in the chosen redshift range;

and(b)we have reduced the problem of varying dilution of

any scattered component by the old stellar populations by

observing all the objects in the rest-frame UV.

Some of the polarimetric and spectroscopic results from c 0000RAS,MNRAS000,000–000

4Tadhunter et al.

the survey have already been published in Shaw etal.(1995)

and Tadhunter et al.(1994).Here we present results for the

Object Date S(”)Time(s)λW(?A) remainder of the sample in Table1,and discuss the results

for this sample collectively.

3OBSER V ATIONS AND REDUCTIONS

B-band polarimetry data and long-slit spectra for most of

the objects in Table1were obtained in three runs on the

ESO3.6m telescope at La Silla in Chile between1993and

1995.All the data from these runs were taken with the ESO

Faint Object Spectrograph and Camera No.1(EFOSC1)

with a thinned TEK chip(No.26),resulting in an angu-

lar scale of0.62arcseconds/pixel.

Long-slit spectra for the sample were obtained using the

R300and B300grisms in EFOSC1(see Melnick et al.1989).

These grisms together provide complete coverage of the ob-

served wavelength range3600to9900?A with a dispersion of

6.2?A/pixel for the B300grism and

7.3?A/pixel for the R300

grism.The instrumental resolution was~20?A with the2

arcsecond slit.With this coverage it was possible to cover

at least the rest wavelength range3500-5500?A for all of the

objects observed with EFOSC1.Details of the spectroscopic

observations are given in Table2.

In addition to the spectra obtained with EFOSC for

most of the sources,two of the objects—3C327.1and

PKS2135-20—were observed using the4.2m William Her-

schel Telescope(WHT)on La Palma with the ISIS dual-

beam spectrograph.Both objects were observed using the

R158R grating on the red arm of ISIS with an EEV CCD

detector and a GG495order sorting?lter,yielding a dis-

persion of2.72?A/pixel and a resolution of10?A for a1.6

arcsecond slit.

The B-band polarimetric observations were obtained

with EFOSC1in polarimetric mode with a Wollaston prism

and aperture mask in the beam.For the1993and1994runs

the polarized signal was modulated by using the Cassegrain

instrument rotator to rotate the?eld relative to the Wol-

laston prism successively through a sequence of four rotator

positions separated by45degrees.However,for the1995

run the signal was modulated by using a half-wave plate

in the beam,and rotating the half-wave plate through the

sequence0,22.5,45,67.5degrees.Details of the polarimetric

observations are given in Table3.

3.1Spectroscopic reductions

The spectroscopic reductions followed the standard steps of

bias subtraction,?at-?elding,wavelength calibration,atmo-

spheric extinction correction,?ux calibration and sky sub-

traction.The?ux calibration was based on an average?ux

calibration curve derived from wide-slit observations of,typ-

ically,three?ux calibration stars in each https://www.360docs.net/doc/d330907.html,parisons

between the?ux calibration curves derived from individ-

ual standard star observations show that the relative?ux

calibration uncertainty is typically±5%over most of the

wavlength range,but rises to±10%in the UV(λ<4200?A)

and near-IR(λ>8000?A).By using a relatively wide slit,

making the observations as close as possible to the zenith,

and,in some cases,making observations with the slit aligned

The UV Continuum Excess in Radio Galaxies5

Object P meas P intθopt(?)θradio(?) Table4.Summary of the results of the B-band polarimetry of the sample of southern radio galaxies corrected for postive bias (Simmons&Stewart1985).P meas is the measured polarization corrected for bias,while P int is the intrinsic polarization corrected for contamination by unpolarized narrow line emission,old stellar populations and nebular continuum(see section5.1for details). The measured position angle of the polarization(θopt)is shown in Column4and,for comparision,the radio PA is included in Column5.The polarization PA and radio PA for0035–02are taken from Tadhunter et al.(1992),the polarization and radio PAs for1934–63are from Tadhunter et al.(1994),and for2250–41the polarization and radio PAs are taken from Shaw et al. (1995).

positions.The intensities for all the rotator positions were then combined according to the prescription of Tinbergen and Rutten(1992)to produce the?nal polarization degrees and position angles shown in Table4.The advantage of this technique for measuring the polarization is that,since it in-volves the ratios of the‘o’and‘e’-ray intensities at each rotator/half-wave plate postion,it is not sensitive to small photometric variations between the images.By combining the intensity ratios from rotator positions separated by90 degrees,or half-wave plate positions separated by45degrees, any instrumental polarization produced in the instrument is automatically eliminated.

The uncertainties in the individual‘o’-and‘e’-ray in-tensities were estimated by combining the estimated un-certainty in the subtracted background(from the stan-dard deviation in the background measurements),with the uncertainty due to the poissonian?uctuation in the source+background counts in the source aperture.These uncertainties were then propagated through the calculation of the polarization degree and angle.The?nal polarization measurements and upper limits shown in Table4have been corrected for the positive bias in the polarization following the prescription of Simmonds and Stewart(1985).

For the1993and1994runs,which used the telescope rotator to modulate the polarization,the polarization angles were calibrated using observations of polarization standard stars observed using the same techniques in the same runs. However,for the1995run,which used the half-wave plate, it was not possible to derive accurate polarization position angles because of problems with the initialisation of the half-wave plate at the end of each cycle;although the degrees of polarization measured for individual polarized sources and polarized standard stars were found to be consistent from one cycle to the next,large variations were found in the measured angles between the cycles.For the signi?cantly polarized objects observed in this run,the values of the po-larization listed in Table4represent the average of the polar-ization values measured independently for each of the two cycles of half-wave plate positions.In the case of objects without signi?cant polarization but two cycles of observa-tions from the1995run,the data were analysed indepen-dently for each cycle,and upper limits were derived from one cycle of observations only.

As a?nal check on the reliability of the measurements, the individual‘o’and‘e’-ray intensity measurements for each cycle were checked to determine whether they followed the pattern expected for linearly polarized light.This allowed us to check for spurious polarizations which might arise,for example,from a cosmic ray a?ecting one of the images.The degrees of polarization measured for the polarized standard stars were found to be consistent with the published values, within the estimated uncertainties.Apart from PKS1934-63 (see Tadhunter et al.1994),all the signi?cant polarization measurements listed in Table4are based on two cycles of rotator/half-wave plate positions and have been checked for consistency between the cycles.

4RESULTS

With the exception of section4.1,which will include results from the full z<0.7sample of Tadhunter et al.(1993),the results presented below are for the restricted sample(0.15< z<0.7)listed in Table1.

4.14000A break measurements

Much of the early work on the continuum properties of radio galaxies concentrated on studies of their broad-band colours. Although this work provided evidence for blue or UV ex-cesses in a large fraction of powerful radio galaxies compared with normal ellipticals,the approach of using the broad-band colours has the disadvantages that:(a)the broad-band ?lters may be contaminated in some redshift ranges by emis-sion lines;and(b)the sensitivity of a particular broad-band colour to the UV excess depends on redshift.For example, the optical/near-IR broad-band colours are sensitive to UV excesses in high redshift(z>0.5)radio galaxies(e.g.Lilly& Longair1984),but lose sensitivity for lower redshift objects.

An alternative way of quantifying the UV excess,which minimises these problems,is to use measurements of the 4000?A continuum break,which is prominent in the spec-tra of evolved stellar populations(D(4000):Bruzual1983). However,some care is required when measuring the4000?A break in powerful radio galaxies,since the bands used in

c 0000RAS,MNRAS000,000–000

6Tadhunter et

al.

Figure1.The parameter D′(4000)is sensitive to the presence of an excess UV?ux compared to evolved stars below4000?A in the rest frame of an object.Two separate datasets have been plotted here:the low redshift(z<0.15)radio galaxies with spectra published in Tadhunter et al.(1993);and the complete sample of0.15

the original de?nition of the D(4000)are contaminated by [NeIII],[SII]and Hδemission lines,which can be strong in the spectra of radio galaxies.Therefore we use a modi?ed version—D′(4000)—which is de?ned as the ratio of the total?ux in a bin100?A wide centred on4200?A(rest frame) to the total?ux in a100?A wide bin centred on3800?A.The narrower bands used in this de?nition avoid strong emis-sion lines,although the contamination by the higher order Balmer lines may still be signi?cant in some objects.The measurement of values of D′(4000)signi?cantly lower than this indicates a UV excess.It is worth emphasising that an additional advantage of using D′(4000)to quanti?y the UV excess is that it is relatively insensitive to?ux calibration errors and intrinsic reddening e?ects.

Measurements of D′(4000)for the restricted0.15

There are several noteworthy features of these results:?Higher redshift objects.All the objects at z>0.15 show evidence for a UV excess,with the old stellar popu-lations contributing<80%of the?ux at wavelengths short-ward of4000?A.

?Lower redshift objects.Although many lower red-shift(z<0.15)radio galaxies have D′(4000)values consis-tent with a large fraction of light from an old stellar popula-tion,a signi?cant proportion of objects(~35%)show smaller values,suggesting a signi?cant UV excess(see also Wills et al.2002).

?Weak line radio galaxies(WLRG).Many of the lower redshift objects with evidence for a UV excess are although they do,of course,form part of the overall z<0.7 complete sample of Tadhunter et al.(1993).

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The UV Continuum Excess in Radio Galaxies7 Object D′(4000)F D4000

8Tadhunter et al.

Nebular fraction

Table6.The fractional contribution of the nebular continuum to the UV?ux.The ratios have been calculated from the mean ?uxes in a100?A bin centred on3590?A(rest-frame),for both the observed nuclear spectra and the theoretical nebular spectra.In each case the nebular spectrum was calculated from the Hβ?ux assuming an electron density of100cm?3and a temperature of 15000K and zero reddening.

4.4Modelling

In order to gain further information about the nature of the UV continuum we have attempted to model the contin-uum spectral energy distributions(SEDs)in terms of various spectral components which may,potentially,contribute to the UV excess.Prior to this modelling e?ort we subtracted the nebular continuum calculated as described in section4.3, and assuming no reddening in this component.

Given that radio galaxies have early-type continuum morphologies at optical wavelengths,we started by assum-ing that the nebular-subtracted optical-UV continuum SEDs comprise a combination of an old stellar population and a power-law.For the old stellar population we used the in-stantaneous burst model of Bruzual and Charlot(1983),for a Salpeter IMF and age(since the starburst)of15Gyr.The power-law was used to represent the“active”component e.g. scattered AGN light or direct AGN light,with the power-law spectral index allowed to vary over the range?6<α<+6 (Fλ∝λ+α).

As a?rst step to modelling the spectra,continuum ?uxes were measured in a number of wavelength bins,cho-sen to avoid strong emission lines,cosmetic defects and re-gions of poor sky subtraction or poor?ux calibration.Er-rors for the continuum?ux measurements were calculated by quadratically combining the Poisson noise in sky+object signal,an assumed relative?ux calibration error of±5%, and an estimate of the systematic error in the background subtraction,determined by examining spatial slices cover-ing the wavelength range of each bin,as extracted from the

Objectχ2αF model

Table7.Results of modelling the SED’s of the southern sample of radio galaxies using two-component—15Gyr galaxy plus power law—models.Column2is the reducedχ2.Column3is the spectral index of the power-law(fλ∝λα).Column4lists the fraction of the total model continuum?ux(including the nebular component)contributed by the?tted power-law component in a wavelength bin just shortward of the4000?A break(3750—3850?A).Where no con?dence interval is quoted the probability of the best–?t model was less than5%.

sky-subtracted2D spectra.The?uxes and errors were es-timated in15–30bins for each object(depending on the useful wavelength range for each spectrum),and the?tting was then performed using the minimumχ2technique de-tailed in Tadhunter et al.(1996).

The results of the modelling are shown in Table7and Figure2.Only objects with signi?cant?ts are shown in the Figure.In most objects the power-law+E-galaxy model pro-vides an adequate?t to the data,with the power-law com-ponent contributing20—90%of the continuum just below the4000?A break(see?nal column in Table7).This con-?rms the results based on the4000?A break measurements described in section4.1.Note,however,that the propor-tional contribution of the power-law to the UV continuum at wavelengths just below4000?A is systematically less than estimates derived from D′(4000)(compare the last columns of Tables5and7).This di?erence is likely to be due to the fact that the D′(4000)measurements were made before the subtraction of the nebular continuum,and therefore over-estimate the contributions of the putative power-law compo-nents.No modelling was performed for PKS1547-79because of the e?ects of di?erential atmospheric refraction on the ?ux measurements.Also,poor sky subtraction,weak signal and relatively short exposure times are likely to be responsi-ble for the relatively poor?ts obtained for PKS0409-75and PKS0347+05.

One interesting general feature of the results in Table7 is that,in the majority of cases,the?tted power-law spec-

c 0000RAS,MNRAS000,000–000

The UV Continuum Excess in Radio Galaxies9

Figure2.Power-law plus15Gyr elliptical galaxy?ts to the continua of the complete sample of radio galaxies.The best-?t model continuum spectrum is indicated by the thick continuous line.The15Gyr elliptical galaxy component is indicated by a dot-dash line, the power-law component by a dotted line and the nebular continuum by a dot-dot-dot-dash line.The?uxes are in units of ergs cm?2 s?1?A?1.

c 0000RAS,MNRAS000,000–000

10Tadhunter et al.

Figure2.Cont.

c 0000RAS,MNRAS000,000–000

The UV Continuum Excess in Radio Galaxies11

Figure2.Cont.

c 0000RAS,MNRAS000,000–000

12Tadhunter et al.

Figure2.Cont.

c 0000RAS,MNRAS000,000–000

The UV Continuum Excess in Radio Galaxies

13

Figure 2.Cont.

tral indices are redder than the mean α=?1.3derived for the optical/UV continua of quasars by Christiani &Vio (1990)over the range 1000–5500?A .They are also redder than most z <0.7quasars in the southern 2Jy sample of Tadhunter et al.(1993),which have measured optical (3000—5500?A )spectral slopes in the range ?2.8<α

Given that the results of the modelling are potentially sensitive to the e?ects of reddening on the subtracted neb-ular continuum ?,we repeated the modelling following sub-traction of a nebular continuum reddened by the amount de-termined from the emission line Balmer decrement assuming case B recombination theory,for cases in which the reden-ning was deemed signi?cant.The results are shown in Table 8.Subtraction of the reddened nebular continuum leads to signi?cantly improved ?ts in the case of PKS0023-26and PKS1648+05,but in most other cases the improvement is marginal.As expected,given that less nebular continuum is being subtracted from the UV excess,the proportional contribution of the power-law component is larger in these models,and the power-law slope is bluer.

?Note that the e?ects of reddening on the power-law component will be re?ected in the ?tted spectral index for that component.We assume in our modelling that the 15Gyr old stellar population is not signi?cantly a?ected by reddening.Object

χ2

α

F model

E(B-V)

Table 8.Results of modelling the SEDs of the southern sample of radio galaxies using two–component —15Gyr galaxy plus power law —models including reddening of the nebular continuum.The columns are the same as Table 7except column 5,which gives the degree of reddening estimated from the Balmer decrement.

However,for three objects —PKS1549-79,PKS2135-20,PKS2314+03(3C459)—we failed to obtain good ?ts to the nebular continuum subtracted SEDs using two compo-nent E-galaxy+power-law models,despite the good quality of the data.In all of these cases we found a signi?cant ex-cess of the data over the models in the wavelength range 3750—4300?A .In addition,higher order Balmer absorption lines are detected in all three objects either in our own spec-tra or published spectra (see di Serego Alighieri et al.1997for a higher resolution spectrum of PKS1549-79),and both PKS2135-20and PKS2314+03have relatively blue contin-uum slopes at wavelengths larger than 4500?A .All of these features are consistent with a signi?cant contribution from young stellar populations (see Tadhunter et al.1996,Robin-son et al.2000).Therefore we have attempted to model the continua of the three objects with various combinations of old and young stellar populations (using the instantaneous burst models of Bruzual &Charlot 1993)and power-laws.We have also tried models in which the young stellar pop-ulations were reddened by varying degrees.The best ?tting models are shown in Table 9,and compared with the data in Figure 3.In the case of PKS1549-79and PKS2135-20we obtained an adequate ?t using models which combine an old (15Gyr)and young stellar populations (reddened in the case of PKS1549-79).On the other hand,in the case of PKS2314+03the best ?t comprised a combination of young stellar populations with two starburst ages plus a power-law.Given that the spectrum of PKS2135-20has a relatively low S/N,that of PKS1549-79has a relatively small spectral cov-erage,and that of PKS2314+03may be a?ected by di?eren-tial atmospheric refraction e?ects (see section 3.1),the mod-elling estimates of the ages of the young stellar populations should not be regarded de?nitive.Nonetheless,these results provide strong evidence that the optical/UV continua of all three objects are dominated by the light of young stellar populations with ages in the range 0.1–2Gyr.4.5

Notes on individual objects

PKS0023-26.This CSS radio galaxy has a large UV excess,

but a low polarization,and no sign of broad permitted lines in its spectrum.A possible starburst candidate.

PKS0035-02(3C17).The strength of the broad permit-ted lines in this BLRG suggests that much of its UV excess is due to direct AGN light.However,given the signi?cant

c

0000RAS,MNRAS 000,000–000

14Tadhunter et al.

Figure3.Fits to the continua of PKS1549–79,PKS2135–20and PKS2314+03(3C459)that include young stellar populations.While two–component elliptical galaxy plus power–law or quasar models cannot reproduce the continuum SEDs of PKS1549–79,PKS2135–20and PKS2314+03(3C459),models in which the spectra are dominated by young stars are successful.PKS1549–79has been modelled by the spectrum of an1Gyr population reddened by E(B-V)=0.4while PKS2135–20is shown plotted with a model comprising an unreddened 0.1Gyr population,and PKS2314+03(3C459)has been modelled with a combination of a1Gyr starburst,a0.5Gyr starburst and a power-law(see Table9).The lower right hand panel shows an expanded plot of the region around the Balmer break in PKS2135–20with the higher Balmer lines(H9,H10)labelled.In all cases the best?tting continuum models are indicated by thick solid lines.

c 0000RAS,MNRAS000,000–000

The UV Continuum Excess in Radio Galaxies15

Objectχ2Age F ys F pl E(B-V) Table9.Best?tting models for PKS1549–79,PKS2135–20and PKS2314+03that include young stellar populations,yield for-mally signi?cant?ts,and reproduce the excess?ux seen in the wavelength interval3900?A–4300?A over the two component (power–law+E-galaxy?ts)models.In the case of PKS2314+03 the?tting results are shown for models both with and without a power-law component.The third column gives the age in Gyr for the best-?tting young stellar populations,while the fourth and ?fth columns give the fractional contributions of the young stel-lar populations and power-law to the total?ux in the normalising bin respectively.

polarization detected at both UV wavelengths(this paper) and optical wavelengths(Tadhunter et al.1992),scattered AGN light may also contribute.Optical synchrotron emis-sion is a plausible alternative to scattered AGN light in this source,given the distorted S-shaped radio structure,and rel-atively strong core-jet visible in high resolution radio maps (Morganti et al.1999).

PKS0038+09(3C18).Direct AGN light is likely to con-tribute much of the UV excess in this BLRG which has a low UV polarization.

PKS0039-44.This FRII radio galaxy has a large UV ex-cess,signi?cant UV polarization,but no broad permitted lines.Although the scattered AGN light is likely to be signif-icant,given the relatively low level of intrinsic polarization (Table4),it is unlikely that this component dominates the UV continuum.A possible starburst candidate.

PKS0105-44(3C32).This FRII radio galaxy has a mod-est UV excess,no signi?cant UV polarization,and no clear detection of broad permitted lines.The origin of its UV ex-cess is not clear.

PKS0117-15(3C38).This high redshift FRII radio galaxy is one of the most highly polarized objects in our sample. Given the high intrinsic polarization(Table4),it is likely that scattered AGN light dominates the UV excess in this source.

PKS0235-19.This FRII radio galaxy shows a large UV excess,but has a low UV polarization.Weak broad wings are marginally detected to the Hβand MgII(2800)permit-ted lines,but deeper spectroscopic observations are required to con?rm that this is a BLRG in which the UV excess is dominated by direct AGN light.

PKS0252-71.Contamination of images and spectra by a forground galaxy preclude detailed study of the optical con-tinuum in this CSS radio galaxy.

PKS0347-05.This unusual FRII radio galaxy has broad permitted lines but only weak narrow lines(di Serego Alighieri et al.1994).Although it has not been possible to model the continuum of this object in detail because of a poor sky subtraction,given the low level of UV polariza-tion,it is likely that direct AGN light contributes much of its UV excess.

PKS0409-75.This FRII radio galaxy is the highest redshift source in our sample.This object clearly has a large UV excess,but it has not been possible to model its continuum in any detail because of a poor sky subtraction.The relatively low UV polarization and failure to detect broad permitted lines make this a strong starburst candidate.

PKS1306-09.This CSS radio galaxy has a large UV excess, only narrow emission lines,and signi?cant UV polarization. Given that the polarization E-vector angle is closer to the parallel than the perpendicular to the radio axis,the polar-ization mechnaism may not be anisotropic scattering,but some alternative mechanism such as dichroic absorption or synchrotron emission.The low level of intrinsic polarization suggests that,in the case that the polarization mechanism is anisotropic scattering,the scattered component does not dominate the UV excess.

PKS1547-79.This BLRG is one of the most luminous sources in our sample.Its continuum properties have been extensively discussed in Shaw et al.(1995),who argue that at least some of the signi?cant UV polarization measured in this source may be due to dichroic absorption in our Galaxy. Di?erential di?raction e?ects preclude detailed modelling of its continuum,but it is likely that the UV excess in this object is dominated by direct AGN light.

PKS1549-79.The narrow emission line properties of this extraordinary?at spectrum radio galaxy have been dis-cussed in detail by Tadhunter et al.(2001).It is likely that this is an intrinsically compact radio source in which the ra-dio jets are pointing close to our line of sight,but the quasar nucleus is entirely extinguished by dust on a kpc-scale.No broad permitted lines are detected in our optical spectra of this source,and we detect no signi?cant UV polarization in our observations.However,di Serego Alighieri et al.(1997) report signi?cant optical polarization at the~3%level in both the optical continuum and[OIII]emission lines in their smaller aperture observations.This polarization could have either a scattering or a dichroic origin,however,it is un-likely that the polarized component dominates the UV ex-cess.Both our continuum modelling,and the detection of Balmer lines in absorption in the higher resolution observa-tion of di Serego Alighieri et al.(1997)are consistent with a starburst dominating the optical/UV continuum in this source.

PKS1602+01(3C327.1).This FRII radio galaxy has been discussed in detail by Shaw et al.(1995),who classify it as a BLRG on the basis of the clear detection of broad Hβemission lines.Given the failure to detect signi?cant UV polarization it is likely that the UV excess in this source is entirely dominated by direct AGN light.

PKS1648+05.This powerful radio source,with a morphol-ogy between FRI and FRII,has weak narrow emission lines in its optical spectrum,and the smallest UV excess of any source in Table1.The continuum measurements presented in this paper refer to the brighter of the two nuclei visible in

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16Tadhunter et al.

optical images of the core region.The cause of the apparent UV excess is unknown.

PKS1932-46.Villar-Martin et al.(1998)report the detec-tion of a broad Hαemission line in this FRII radio galaxy (also visible in the spectrum in Figure2),but it shows no signi?cant UV polarization.The residuals from the two com-ponent continuum model?t suggest a signi?cant contribu-tion from a starburst component,in addition to direct AGN light.The spectacular extended emission line nebulosity sur-rounding the galaxy is described in detail by Villar-Martin et al.(1998).

PKS1934-63.As discussed in Tadhunter et al.(1994),this GPS radio galaxy is signi?cantly polarized in the UV with the polarization E-vector close to perpendicular to the radio axis.No broad permitted lines are detected in our optical spectra.It is likely that scattered AGN light makes a signif-icant contribution to the UV excess in this source.

PKS1938-15.This FRII shows broad Hβand MgII(2800) emission lines in its optical/UV spectrum,but is not signi?-cantly polarized in the UV.Therefore its UV excess is likely to be dominated by direct AGN light.

PKS2135-20.Shaw et al.(1995)have reported the detec-tion of broad MgII(2800)in this CSS radio galaxy.However, its classi?cation as a BLRG is not certain because of the pos-sibility that blended narrow high ionization lines make a con-tribution to the broad wings of MgII(2800)in our low reso-lution spectrum(e.g.Dey&Spinrad1996,Tran et al.1998). The detection of the Balmer break higher Balmer absorption lines(H9,H10:see Figure3)in our optical spectrum suggests a dominant contribution from a starburst component,and this is con?rmed by our continuum modelling.PKS2135-20 may be a radio-loud example of the“post-starburst quasar”phenomenon?rst reported by Brotherton et al.(1999). PKS2211-17.Despite the fact that it belongs to the class of weak line radio galaxies,with no broad permitted lines detected in its optical spectrum,this FRII radio galaxy dis-plays a substantial UV excess.A signi?cant contribution from a starburst component is suspected.

PKS2250-41.The continuum properties of this FRII radio galaxy have been discussed in detail by Shaw et al.(1995) and Dickson et al.(1995).Its optical spectrum shows only narrow emission lines,but it is signi?cantly polarized in the UV with the polarization E-vector close to the perpendicu-lar to the UV structural axis.The relatively high instrinsic polarization suggests that scattered AGN light makes a sub-stantial contribution to the UV excess in the nuclear regions. Clark et al.(1997)and Villar-Martin et al.(1999)describe detailed spectroscopic and imaging observations of a spec-tacular jet-cloud interaction on the west side of the nucleus. PKS2314+05(3C459).The optical/UV spectrum of this FRII radio galaxy is clearly dominanted by the light of a young stellar population,with the Balmer break and higher Balmer absorption lines clearly detected(see also Miller 1981).Our spectrum shows no clear evidence for broad per-mitted lines.5DISCUSSION

5.1The scattered AGN component

Our polarization measurements of a complete,optically un-biased sample allow us to gauge for the?rst time the signif-icance of the scattered AGN component in UV continua of the general population of powerful radio galaxies.

We detect signi?cant UV polarization in only a rela-tively small fraction(~37%)of our sample,and the level of polarization is relatively low in the objects that are polarized (P B<10%).Moreover,scattering of the anisotropic quasar light is not the only polarization mechanism,but other mechanisms such as dichroic absorption and synchrotron ra-diation may also contribute.Therefore it is safe to conclude that the scattered AGN component does not dominate the UV light in the majority of sources in our sample.For pure scattered light we would expect to measure polarization at the P>10%level,even allowing for the geometrical dilu-tion caused by integrating over the broad radiation cones of the illuminating AGN(Young et al.1995,Manzini&di Serego Alighieri1996).

By assuming that all the polarization is due entirely to the power-law component(see section4.4),we can use the fractional contribution of the power-law in the B-band ?lter,as determined from our modelling,to estimate the intrinsic polarization of the polarized component.In this way we automatically correct for the contributions of the old stellar populations and the nebular continuum,which are assumed to be unpolarized.A further assumption im-plicit in this procedure is that the fractional contribution of the polarized component is the same in the(di?erent) apertures used for the spectroscopic and polarimetric obser-vations,which is not necessarily the case.The results,which have also been corrected for emission line contamination in the?lter band-pass,are shown in Table4.From this it can be seen that the high levels of intrinsic polarization estimated for PKS2250-41and PKS0117-15(3C38)are consistent with scattered light comprising a large fraction of the power-law component.However,in most of the other cases,the rela-tively low levels of intrinsic polarization(P int)suggest that other,unpolarized,sources of UV light may contribute to the component modelled as a power-law

Figure4shows the intrinsic polarization plotted as a function of redshift.Although the upper envelope de?ned by the three most highly polarized sources shows evidence for a rise in the intrinsic polarization with redshift,taking the sample as a whole,and including the upper limits,this trend does not appear to be signi?cant.

The proportion of highly polarized sources in our sam-ple is somewhat less than found in other studies(Tadhunter et al.1992,Cimatti et al.1993,Vernet et al.2001).Possible reasons for this include the following.

?Observational biases of previous studies.Because the polarization measurements are di?cult to make,previ-ous surveys are likely to have been biased towards the most spectacular and luminous radio galaxies in a given redshift range.Moreover,null results may not be always be reported in the literature.

?Selection frequency of the current survey.The selection frequency of the2Jy sample(2.7GHz)is higher than for most other samples.However,it is not clear that

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The UV Continuum Excess in Radio Galaxies

17 Figure4.Plot of the intrinsic polarization as a function of redshift for the sample in Table1.The BLRG are indicated by?lled squares, and the NLRG are indicated by?lled stars.

this will necessarily bias our sample against high UV polar-ization.Most of our sources would in any case have been selected in low frequency surveys.

?Redshift dependent e?ects.For a given density of scatterers the strength of the scattered component will de-pend on the luminosity of the central illuminating source. The radio power is strongly correlated with the redshift in ?ux limited samples such as the2Jy sample.Also,since op-tical emission line luminosity is strongly correlated with ra-dio power(e.g.Rawlings&Saunders1991,Tadhunter et al. 1998),it is likely that the illuminating quasars hidden in the cores of the radio galaxies will become more luminous as the redshift increases.Therefore,we might expect the scattered quasar component to become more signi?cant as the red-shift increases and the sources become more powerful.Part of the di?erence between the results of our survey and those of previous surveys of higher redshift objects may be due to this e?ect.

The only way to unambiguously distinguish between these possibilities would be to make an optically unbiased survey of a large sample of radio galaxies selected from low fre-quency radio surveys at a single frequency,and spanning a wide range in redshift.However,if the last possibility is cor-rect we would expect the most highly polarized sources in our sample to be those with the strongest signs of quasar activity,as deduced from the narrow emission line luminosi-ties.Figure5shows a plot of[OIII]emission line luminos-ity against radio power for the sample in Table1,with the signi?cantly polarized objects highlighted.As discussed in Tadhunter et al.(1998),[OIII]is more sensitive to quasar ionizing luminosity than lower ionization emission lines such as[OII](3727)and Hβ,and it is likely that the large scatter in this plot is a consequence of a large range in the quasar luminosity for a given radio power.It is clear that many of the highly polarized sources fall close to the upper en-velope of the[OIII]luminosity in this plot,thus suggesting that the objects with the most luminous quasars are also those with the greatest proportional contribution of scat-tered AGN light in the UV.

5.2Direct AGN light

We have identi?ed9objects in our sample(~40%of the total)which show broad permitted emission lines in their spectra and should therefore be classi?ed as BLRG?.With the exception of PKS0035-02(3C17),and possibly also PKS1547-79,none of the BLRG in our sample is highly polarized in the UV,despite the presence of large UV ex-cesses.Therefore,it is likely that we are observing the nuclei directly in these sources,and that the UV excess is due to di-rect AGN light,with only a minor contribution,if any,from scattered AGN light.This is in line with polarimetric obser-vations of low redshift BLRG and quasars which show low levels of polarization in most objects(Stockman,Angel& Miley1979,Antonucci1984).Clearly,objects such as3C234 (Tran,Cohen&Goodrich1995)and3C109(Goodrich&Co-hen1992),in which the broad lines are readily detected in optical spectra,and which also show a high degree of linear polarization,are the exception rather than the rule.

It is interesting to consider how these BLRG?t into the orientation-based uni?ed schemes for powerful radio galax-ies,in which it is proposed that radio galaxies and quasars are the same thing viewed from di?erent directions,with the ?It is important to distinguish between these BLRG—in which the broad lines are readily visible in the straight intensity spec-tra—and objects in which the broad lines are only visible in polarized spectra or following detailed continuum modelling and subtraction(e.g.Cohen et al.1999).

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18Tadhunter et

al.

Figure5.[OIII]emission line luminosity plotted against total radio power for the complete sample in Table1.NLRG are in-dicated by triangles,while BLRG are idiciated by circles.Filled symbols indicate objects for which a signi?cant UV polarization has been detected.Stars indicate the two objects in our sample (PKS1549-79&PKS2314+03)that are unusually bright at far-IR wavelengths.

quasar nucleus blocked from direct view in the radio galax-ies by a central obscuring torus(Barthel1989).There are two main possibilities:

?They are partially obscured quasars.In this case, the quasar nuclei would be observed at intermediate angles, such that they su?er mild extinction from the outer layers of the torus or the kpc-scale dust lane.

?They are low luminosity quasars.In this case,there would be a wide range of quasar luminosity at a given radio power—as already suggested by the large scatter in the correlation between[OIII]emission line luminosity and ra-dio power(Tadhunter et al.1998)—and the BLRG would represent the low luminosity end of the quasar luminosity function.

It would be di?cult to distinguish between these possibili-ties based on the current data alone,but the relatively red slopes of the power-laws?tted to the BLRG in the two com-ponent model?ts(see section4.4)are more consistent with the?rst of these two possibilities.The partial obscuration idea is also consistent with the recent spectroscopic stud-ies of quasars which suggest that a signi?cant proportion of quasars are signi?cantly reddened(e.g.Baker1997)at opti-cal wavelengths.Moreover,analyses of the radio properties of the2Jy sample,in particular the ratio of core to extended radio power,are consistent with the idea that the BLRG are observed with the radio axis at an intermediate angle to the line of sight(Morganti et al.1997).

5.3Young stellar populations

One of the most striking results from our survey is the emer-gence of a group of three radio galaxies(15%of the total)in which the optical/UV continua are dominated by the light of young stellar populations.Interestingly,these three radio galaxies—3C459,PKS1549-79,PKS2135-20—all have rel-atively compact radio sources:3C459has an extended dou-ble radio source on a scale of48kpc(Morganti et al.1999), but also has a steep spectrum radio core,which is itself dou-ble;PKS2135-20is classi?ed as a compact steep spectrum radio source;and,although PKS1549-79has a?at radio spectrum and a one sided jet structure extending to radial distances of500pc,we have argued elsewhere on the basis of its emission line kinematics that this is an intrinsically compact radio source(Tadhunter et al.2001).

It is relatively easy to detect the young stellar popula-tions in PKS2135-20,PKS1549-79and3C459because their optical continua are dominated by the young stars,and the ages of the starbursts(0.1—2Gyr)are such that the spec-tral features of the young stellar population are relatively easy to detect.However,it is possible that signi?cant young stellar populations are present in other radio galaxies in our sample,but are more di?cult to detect because the stellar populations are younger and/or are less luminous relative to the old stellar populations.In particular,there are three sources in our sample with large UV excesses—PKS0023-26,PKS0409-75,PKS2211-17—for which we have failed to identify the cause of the UV excess,because they show nei-ther signi?cant UV polarization nor broad permitted lines, and the nebular continuum makes a relatively minor con-tribution to their UV emission.There are a further three objects—PKS0039-44,PKS1934-63,PKS1306-09—which are signi?cantly polarized in the UV,but the level of intrin-sic polarization,if attributed solely to the power-law compo-nent,is less than expected for pure scattered light.Finally, we note that the residuals of the two component?ts to the continuum of the weak broad line object PKS1932-46—with a signi?cant excess in the3800–4300?A region and a blue continuum slope at longer wavelengths—are consis-tent with with the presence of a young stellar population. Although young stellar populations may make a signi?cant contribution in all of these objects,the relatively red slopes of the?tted power-laws for most of them(Tables7&8) suggest that the starburst component must be signi?cantly reddened.

Taking these six less certain cases along with three ob-jects in which the young stellar populations dominate,we derive a conservative upper limit of50%on the proportion of objects in our sample which have their optical/UV con-tinua dominated by the light of young stellar populations. This is entirely consistent with the results from two recent surveys of lower redshift3C radio sources in which~30–40%of the objects show evidence for recent star formation activity(Aretxaga et al.2001,Wills et al.2001).

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The UV Continuum Excess in Radio Galaxies

19

Figure 6.A plot of far-infrared (60μm)luminosity against red-shift.

5.4

The far-IR/starburst link in powerful radio galaxies

The far-IR/sub-mm continuum excesses detected in some ra-dio galaxies are often attributed to dust heated by starbursts (e.g.Rowan-Robinson 1995,Archibald et al.2001).However,this interpretation is controversial,given the likely presence of powerful quasar nuclei hidden in the cores of the galaxies which could also heat the cooler dust component (Sanders et al.1989).Indeed,the issues surrounding the nature of the far-IR continuum are similar to those surrounding the UV excess considered in this paper:is the far-IR/sub-mm excess primarily a direct consequence of the quasar activity,or is it a consequence of starbursts related to the evolutionary events that triggered the activity?

In order to investigate the links between the far-IR ex-cess and optical/UV starburst activity,we have extracted 60μm ?uxes and 3σupper limits from IRAS ‘all-sky’survey data.To do this we used the SCANPI algorithm available at IPAC to co-add individual IRAS scans.The IRAS co-added scans were then visually inspected in order to assess the signi?cance of individual detections.The detection of an object was only considered signi?cant if the positional o?-set in the detection was less than 0.5arcminutes from the nominal position of the object,and the object was detected in more than one IRAS band.In cases without clear detec-tions we quote 3σupper limits,where σwas taken as the RMS deviation from the baseline-corrected scans at 60μm.The resulting ?uxes and upper limits are presented in Table

Object

F 60μm (Jy)

νP 60μm (erg s ?1)

20Tadhunter et al.

activity and the level of the far-IR excess.Recently,we ob-tained a similar result for a sample of lower redshift3C sources(Wills et al.2001):the object with the largest contri-bution from an optical/UV starburst in that sample(3C433) also has the largest far-IR luminosity.All of these results support the idea that the cooler dust components detected in radio galaxies are heated by starbursts rather than hidden quasar nuclei.The putative link between far-IR excess and optical/UV starburst activity for powerful radio galaxies will be discussed in more detail in a future paper(Tadhunter et al.2002,in preparation).

5.5Implications for studies of quasar host

galaxies

If the uni?ed schemes for powerful radio galaxies are cor-rect,then radio galaxies are quasar host galaxies in which the quasar nuclei are hidden from our direct view.There-fore,we expect to?nd the same components contributing to the UV excess in the quasar hosts as we do in the pow-erful radio galaxies.Indeed,if the scattering dust grains are large relative to the wavelength of the optical/UV light,the scattered AGN component may be more signi?cant in the quasar hosts,because of the forward scattering properties of the dust grains.On the basis the results reported above, it would be unwise to base any investigation of quasar host galaxy properties on continuum colours alone.Clearly,de-tailed spectroscopic and polarimetric observations are as im-portant for disentangling the various components contribut-ing to the optical/UV continuum in quasar hosts,as they are in powerful radio galaxies.

6CONCLUSIONS AND FURTHER WORK

The results of our survey con?rm the multi-component na-ture of the UV continuum in powerful radio galaxies.We can quantify the contributions of the various components that contribute to the UV excess in the near-nuclear regions as follows:

?Nebular continuum.This is present in the spectra of all the objects and contributes5–40%of the UV continuum below the Balmer break.

?Direct AGN light.Based on the detection of broad permitted lines in the intensity spectra,direct AGN light makes a signi?cant contibution to the UV excess in~30–40%of the objects in our sample.

?Scattered AGN light.Polarimetric observations pro-vide evidence that scattered AGN light makes a signi?cant contribution to the UV continuum in37%of the19objects in our sample with polarization measurements,but in most cases the scattered component does not appear to dominate the UV excess.

?Starburst component.Young stellar populations clearly dominate the optical/UV continua in three of the objects in our sample(~15%)and may make a large contri-bution to the optical/UV continuum in up to50%of all the sample objects.

Of these components,the starburst component clearly warrants further investigation.If,as seems likely,the star-bursts were triggered by the same merger events that trig-gered the radio jet and quasar activity,then detailed stud-ies of the starbursts can provide potentially unique informa-tion about the genesis of powerful radio sources,particularly the timescales,the nature of the mergers and the order-of-events.

Acknowledgments

Based on observations collected at the European Southern Observatory,La Silla,Chile,and at the Roque de los Mucha-chos Observatory,La Palma.RD,MVM,TGR&KAW ac-knowledge support from PPARC while this work was being carried out.

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五年级上册成语解释及近义词反义词和造句大全.doc

五年级上册成语解释及近义词反义词和造句大全 囫囵吞枣;【解释】:囫囵:整个儿。把枣整个咽下去,不加咀嚼,不辨味道。比喻对事物不加分析考虑。【近义词】:不求甚解【反义词】融会贯穿[造句];学习不能囫囵吞枣而是要精益求精 不求甚解;bùqiúshènjiě【解释】:甚:专门,极。只求明白个大概,不求完全了解。常指学习或研究不认真、不深入【近义词】:囫囵吞枣【反义词】:精益求精 造句;1;在学习上,我们要理解透彻,不能不求甚解 2;学习科学文化知识要刻苦钻研,深入领会,不能粗枝大叶,不求甚解。 千篇一律;【解释】:一千篇文章都一个样。指文章公式化。也比喻办事按一个格式,专门机械。 【近义词】:千人一面、如出一辙【反义词】:千差万别、形形色色 造句;学生旳作文千篇一律,专门少能有篇与众不同旳,这确实是平常旳练习太少了。 倾盆大雨;qīngpéndàyǔ【解释】:雨大得象盆里旳水直往下倒。形容雨大势急。 【近义词】:大雨如柱、大雨滂沱【反义词】:细雨霏霏牛毛细雨 造句;3月旳天说变就变,瞬间下了一场倾盆大雨。今天下了一场倾盆大雨。 坚决果断;áobùyóuyù:意思;做事果断,专门快拿定了主意,一点都不迟疑,形容态度坚决 近义词;不假思索斩钉截铁反义词;犹豫不决 造句;1看到小朋友落水,司马光坚决果断地搬起石头砸缸。2我坚决果断旳承诺了她旳要求。 饥肠辘辘jīchánglùlù【近义词】:饥不择食【反义词】:丰衣足食 造句;1我放学回家已是饥肠辘辘。2那个饥肠辘辘旳小孩差不多两天没吃饭了 滚瓜烂熟gǔnguālànshóu〔shú)【解释】:象从瓜蔓上掉下来旳瓜那样熟。形容读书或背书流利纯熟。【近义词】:倒背如流【反义词】:半生半熟造句;1、这篇课文我们早已背得滚瓜烂熟了 流光溢彩【liúguāngyìcǎi】解释;光影,满溢旳色彩,形容色彩明媚 造句:国庆节,商场里装饰旳流光溢彩。 津津有味;jīnjīnyǒuwèi解释:兴趣浓厚旳模样。指吃得专门有味道或谈得专门有兴趣。 【近义词】:兴致勃勃有滋有味【反义词】:索然无味、枯燥无味 造句;1今天旳晚餐真丰富,小明吃得津津有味。 天长日久;tiānchángrìjiǔ【解释】:时刻长,生活久。【近义词】:天长地久【反义词】:稍纵即逝 造句:小缺点假如不立即改掉, 天长日久就会变成坏适应 如醉如痴rúzuìrúchī【解释】:形容神态失常,失去自制。【近义词】:如梦如醉【反义词】:恍然大悟造句;这么美妙旳音乐,我听得如醉如痴。 浮想联翩【fúxiǎngliánpiān解释】:浮想:飘浮不定旳想象;联翩:鸟飞旳模样,比喻连续不断。指许许多多旳想象不断涌现出来。【近义词】:思绪万千 造句;1他旳话让人浮想联翩。2:这幅画饱含诗情,使人浮想联翩,神游画外,得到美旳享受。 悲欢离合bēihuānlíhé解释;欢乐、离散、聚会。泛指生活中经历旳各种境遇和由此产生旳各种心情【近义词】:酸甜苦辣、喜怒哀乐【反义词】:平淡无奇 造句;1人一辈子即是悲欢离合,总要笑口常开,我们旳生活才阳光明媚. 牵肠挂肚qiānchángguàdù【解释】:牵:拉。形容十分惦念,放心不下 造句;儿行千里母担忧,母亲总是那个为你牵肠挂肚旳人 如饥似渴rújīsìkě:形容要求专门迫切,仿佛饿了急着要吃饭,渴了急着要喝水一样。 造句;我如饥似渴地一口气读完这篇文章。他对知识旳如饥似渴旳态度造就了他今天旳成功。 不言而喻bùyánéryù【解释】:喻:了解,明白。不用说话就能明白。形容道理专门明显。 【近义词】:显而易见【反义词】:扑朔迷离造句;1珍惜时刻,好好学习,那个道理是不言而喻旳 与众不同;yǔzhòngbùtóng【解释】:跟大伙不一样。 〖近义词〗别出心裁〖反义词〗平淡无奇。造句; 1从他与众不同旳解题思路中,看出他专门聪慧。2他是个与众不同旳小孩

The way常见用法

The way 的用法 Ⅰ常见用法: 1)the way+ that 2)the way + in which(最为正式的用法) 3)the way + 省略(最为自然的用法) 举例:I like the way in which he talks. I like the way that he talks. I like the way he talks. Ⅱ习惯用法: 在当代美国英语中,the way用作为副词的对格,“the way+ 从句”实际上相当于一个状语从句来修饰整个句子。 1)The way =as I am talking to you just the way I’d talk to my own child. He did not do it the way his friends did. Most fruits are naturally sweet and we can eat them just the way they are—all we have to do is to clean and peel them. 2)The way= according to the way/ judging from the way The way you answer the question, you are an excellent student. The way most people look at you, you’d think trash man is a monster. 3)The way =how/ how much No one can imagine the way he missed her. 4)The way =because

悲惨的近义词反义词和造句

悲惨的近义词反义词和造句 导读:悲惨的近义词 悲凉(注释:悲哀凄凉:~激越的琴声。) 悲惨的反义词 幸福(注释:个人由于理想的实现或接近而引起的一种内心满足。追求幸福是人们的普遍愿望,但剥削阶级把个人幸福看得高于一切,并把个人幸福建立在被剥削阶级的痛苦之上。无产阶级则把争取广大人民的幸福和实现全人类的解放看作最大的幸福。认为幸福不仅包括物质生活,也包括精神生活;个人幸福依赖集体幸福,集体幸福高于个人幸福;幸福不仅在于享受,而主要在于劳动和创造。) 悲惨造句 1.一个人要发现卓有成效的真理,需要千百个人在失败的探索和悲惨的错误中毁掉自己的生命。 2.贝多芬的童年尽管如是悲惨,他对这个时代和消磨这时代的地方,永远保持着一种温柔而凄凉的回忆。 3.卖火柴的小女孩在大年夜里冻死了,那情景十分悲惨。 4.他相信,他们每个人背后都有一个悲惨的故事。 5.在那次悲惨的经历之后,我深信自己绝对不是那种可以离家很远的人。 6.在人生的海洋上,最痛快的事是独断独航,但最悲惨的却是回头无岸。 7.人生是艰苦的。对不甘于平庸凡俗的人那是一场无日无夜的斗

争,往往是悲惨的、没有光华的、没有幸福的,在孤独与静寂中展开的斗争。……他们只能依靠自己,可是有时连最强的人都不免于在苦难中蹉跎。罗曼·罗兰 8.伟大的心胸,应该表现出这样的气概用笑脸来迎接悲惨的厄运,用百倍的勇气来应付开始的不幸。鲁迅人在逆境里比在在顺境里更能坚强不屈。遇厄运时比交好运时容易保全身心。 9.要抓紧时间赶快生活,因为一场莫名其妙的疾病,或者一个意外的悲惨事件,都会使生命中断。奥斯特洛夫斯基。 10.在我一生中最悲惨的一个时期,我曾经有过那类的想法:去年夏天在我回到这儿附近的地方时,这想法还缠着我;可是只有她自己的亲自说明才能使我再接受这可怕的想法。 11.他们说一个悲惨的故事是悲剧,但一千个这样的故事就只是一个统计了。 12.不要向诱惑屈服,而浪费时间去阅读别人悲惨的详细新闻。 13.那起悲惨的事件深深地铭刻在我的记忆中。 14.伟大的心胸,应该用笑脸来迎接悲惨的厄运,用百倍的勇气来应付一切的不幸。 15.一个人要发现卓有成效的真理,需要千百万个人在失败的探索和悲惨的错误中毁掉自己的生命。门捷列夫 16.生活需要爱,没有爱,那些受灾的人们生活将永远悲惨;生活需要爱,爱就像调味料,使生活这道菜充满滋味;生活需要爱,爱让生活永远充满光明。

The way的用法及其含义(二)

The way的用法及其含义(二) 二、the way在句中的语法作用 the way在句中可以作主语、宾语或表语: 1.作主语 The way you are doing it is completely crazy.你这个干法简直发疯。 The way she puts on that accent really irritates me. 她故意操那种口音的样子实在令我恼火。The way she behaved towards him was utterly ruthless. 她对待他真是无情至极。 Words are important, but the way a person stands, folds his or her arms or moves his or her hands can also give us information about his or her feelings. 言语固然重要,但人的站姿,抱臂的方式和手势也回告诉我们他(她)的情感。 2.作宾语 I hate the way she stared at me.我讨厌她盯我看的样子。 We like the way that her hair hangs down.我们喜欢她的头发笔直地垂下来。 You could tell she was foreign by the way she was dressed. 从她的穿著就可以看出她是外国人。 She could not hide her amusement at the way he was dancing. 她见他跳舞的姿势,忍俊不禁。 3.作表语 This is the way the accident happened.这就是事故如何发生的。 Believe it or not, that's the way it is. 信不信由你, 反正事情就是这样。 That's the way I look at it, too. 我也是这么想。 That was the way minority nationalities were treated in old China. 那就是少数民族在旧中

(完整版)the的用法

定冠词the的用法: 定冠词the与指示代词this ,that同源,有“那(这)个”的意思,但较弱,可以和一个名词连用,来表示某个或某些特定的人或东西. (1)特指双方都明白的人或物 Take the medicine.把药吃了. (2)上文提到过的人或事 He bought a house.他买了幢房子. I've been to the house.我去过那幢房子. (3)指世界上独一无二的事物 the sun ,the sky ,the moon, the earth (4)单数名词连用表示一类事物 the dollar 美元 the fox 狐狸 或与形容词或分词连用,表示一类人 the rich 富人 the living 生者 (5)用在序数词和形容词最高级,及形容词等前面 Where do you live?你住在哪? I live on the second floor.我住在二楼. That's the very thing I've been looking for.那正是我要找的东西. (6)与复数名词连用,指整个群体 They are the teachers of this school.(指全体教师) They are teachers of this school.(指部分教师) (7)表示所有,相当于物主代词,用在表示身体部位的名词前 She caught me by the arm.她抓住了我的手臂. (8)用在某些有普通名词构成的国家名称,机关团体,阶级等专有名词前 the People's Republic of China 中华人民共和国 the United States 美国 (9)用在表示乐器的名词前 She plays the piano.她会弹钢琴. (10)用在姓氏的复数名词之前,表示一家人 the Greens 格林一家人(或格林夫妇) (11)用在惯用语中 in the day, in the morning... the day before yesterday, the next morning... in the sky... in the dark... in the end... on the whole, by the way...

“the way+从句”结构的意义及用法

“theway+从句”结构的意义及用法 首先让我们来看下面这个句子: Read the followingpassageand talkabout it wi th your classmates.Try totell whatyou think of Tom and ofthe way the childrentreated him. 在这个句子中,the way是先行词,后面是省略了关系副词that或in which的定语从句。 下面我们将叙述“the way+从句”结构的用法。 1.the way之后,引导定语从句的关系词是that而不是how,因此,<<现代英语惯用法词典>>中所给出的下面两个句子是错误的:This is thewayhowithappened. This is the way how he always treats me. 2.在正式语体中,that可被in which所代替;在非正式语体中,that则往往省略。由此我们得到theway后接定语从句时的三种模式:1) the way+that-从句2)the way +in which-从句3) the way +从句 例如:The way(in which ,that) thesecomrade slookatproblems is wrong.这些同志看问题的方法

不对。 Theway(that ,in which)you’re doingit is comple tely crazy.你这么个干法,简直发疯。 Weadmired him for theway inwhich he facesdifficulties. Wallace and Darwingreed on the way inwhi ch different forms of life had begun.华莱士和达尔文对不同类型的生物是如何起源的持相同的观点。 This is the way(that) hedid it. I likedthe way(that) sheorganized the meeting. 3.theway(that)有时可以与how(作“如何”解)通用。例如: That’s the way(that) shespoke. = That’s how shespoke.

知己的近义词反义词及知己的造句

知己的近义词反义词及知己的造句 本文是关于知己的近义词反义词及知己的造句,感谢您的阅读! 知己的近义词反义词及知己的造句知己 基本解释:顾名思义是了解、理解、赏识自己的人,如"知己知彼,百战不殆";更常指懂你自己的挚友或密友,它是一生难求的朋友,友情的最高境界。正所谓:"士为知己者死"。 1.谓了解、理解、赏识、懂自己。 2.彼此相知而情谊深切的人。 【知己近义词】 亲信,好友,密友,心腹,挚友,深交,相知,知交,知友,知心,知音,石友,老友,至友 【知己反义词】 仇人敌人陌路 【知己造句】 1、我们想要被人爱、想拥有知己、想历经欢乐、想要安全感。 2、朋友本应是我们的亲密知己和支持者,但对于大多数人来说,有一些朋友比起帮助我们,更多的却是阻碍。 3、那么,为什么你就认为,随着年龄的增长,比起女人来男人们的知己和丰富的人际关系更少,因此一般容易更孤独呢? 4、他成了我的朋友、我的知己、我的顾问。 5、无论在我当州长还是总统的时候,布鲁斯都是我的密友、顾问和知己。他这样的朋友人人需要,也是所有总统必须拥有的。

6、波兰斯基有着一段声名卓著的电影生涯,也是几乎所有电影界重要人物们的挚友和同事,他们是知己,是亲密的伙伴。 7、搜索引擎变成了可以帮追我们的忏悔室,知己,信得过的朋友。 8、这样看来,奥巴马国家安全团队中最具影响力的当属盖茨了――但他却是共和党人,他不会就五角大楼以外问题发表看法或成为总统知己。 9、我们的关系在二十年前就已经和平的结束了,但在网上,我又一次成为了他精神层面上的评论家,拉拉队,以及红颜知己。 10、这位“知己”,作为拍摄者,站在距离电视屏幕几英尺的地方对比着自己年轻版的形象。 11、父亲与儿子相互被形容为对方的政治扩音筒、知己和后援。 12、这对夫妻几乎没有什么至交或知己依然在世,而他们在后纳粹时期的德国也不可能会说出实话的。 13、她把我当作知己,于是,我便将她和情人之间的争吵了解得一清二楚。 14、有一种友谊不低于爱情;关系不属于暖昧;倾诉一直推心置腹;结局总是难成眷属;这就是知己! 15、把你的治疗师当做是可以分享一切心事的知己。 16、莉莉安对我敞开心胸,我成了她的知己。 17、据盖洛普民意调查显示,在那些自我认同的保守党人中,尽管布什仍维持72%支持率,但他在共和党领导层中似乎很少有几位知

way 用法

表示“方式”、“方法”,注意以下用法: 1.表示用某种方法或按某种方式,通常用介词in(此介词有时可省略)。如: Do it (in) your own way. 按你自己的方法做吧。 Please do not talk (in) that way. 请不要那样说。 2.表示做某事的方式或方法,其后可接不定式或of doing sth。 如: It’s the best way of studying [to study] English. 这是学习英语的最好方法。 There are different ways to do [of doing] it. 做这事有不同的办法。 3.其后通常可直接跟一个定语从句(不用任何引导词),也可跟由that 或in which 引导的定语从句,但是其后的从句不能由how 来引导。如: 我不喜欢他说话的态度。 正:I don’t like the way he spoke. 正:I don’t like the way that he spoke. 正:I don’t like the way in which he spoke. 误:I don’t like the way how he spoke. 4.注意以下各句the way 的用法: That’s the way (=how) he spoke. 那就是他说话的方式。 Nobody else loves you the way(=as) I do. 没有人像我这样爱你。 The way (=According as) you are studying now, you won’tmake much progress. 根据你现在学习情况来看,你不会有多大的进步。 2007年陕西省高考英语中有这样一道单项填空题: ——I think he is taking an active part insocial work. ——I agree with you_____. A、in a way B、on the way C、by the way D、in the way 此题答案选A。要想弄清为什么选A,而不选其他几项,则要弄清选项中含way的四个短语的不同意义和用法,下面我们就对此作一归纳和小结。 一、in a way的用法 表示:在一定程度上,从某方面说。如: In a way he was right.在某种程度上他是对的。注:in a way也可说成in one way。 二、on the way的用法 1、表示:即将来(去),就要来(去)。如: Spring is on the way.春天快到了。 I'd better be on my way soon.我最好还是快点儿走。 Radio forecasts said a sixth-grade wind was on the way.无线电预报说将有六级大风。 2、表示:在路上,在行进中。如: He stopped for breakfast on the way.他中途停下吃早点。 We had some good laughs on the way.我们在路上好好笑了一阵子。 3、表示:(婴儿)尚未出生。如: She has two children with another one on the way.她有两个孩子,现在还怀着一个。 She's got five children,and another one is on the way.她已经有5个孩子了,另一个又快生了。 三、by the way的用法

小学语文反义词仿照的近义词反义词和造句

仿照的近义词反义词和造句 仿照的近义词 【仿制解释】:仿造:~品 【模仿解释】:个体自觉或不自觉地重复他人的行为的过程。是社会学习的重要形式之一。尤其在儿童方面,儿童的动作、语言、技能以及行为习惯、品质等的形成和发展都离不开模仿。可分为无意识模仿和有意识模仿、外部模仿和内部模仿等多种类型。 仿照的反义词 【独创解释】:独特的创造:~精神ㄧ~一格。 仿照造句 一、老师让我们仿照黑板上的图画一幅画。 二、仿照下面的句式,以“只有”开头,写一结构与之相似的复句。 三、仿照例句的句子,在下面两句的横线上补写相应的内容。 四、仿照例句,以“记忆”或“友情”开头,另写一句话。 五、仿照下面两个例句,用恰当的词语完成句子,要求前后语意关联。 六、仿照开头两句句式,通过联想,在后面两句横线上填上相应的词语。 七、仿照所给例句,用下面的词展开联想,给它一个精彩的解释。 八、仿照例句,以“你”开头,另写一个句子。 九、仿照下列句式,续写两个句子,使之与前文组成意义相关的.句子。 十、我们也仿照八股文章的笔法来一个“八股”,以毒攻毒,就叫做八大罪状吧。

十一、仿照例句,任选一种事物,写一个句子。 十二、仿照下面一句话的句式和修辞,以“时间”开头,接着写一个句子。 十三、仿照例句,以“热爱”开头,另写一句子。 十四、仿照下面的比喻形式,另写一组句子。要求选择新的本体和喻体,意思完整。 十五、根据语镜,仿照划线句子,接写两句,构成语意连贯的一段话。 十六、仿照下面句式,续写两个句式相同的比喻句。 十七、自选话题,仿照下面句子的形式和修辞,写一组排比句。 十八、仿照下面一句话的句式,仍以“人生”开头,接着写一句话。 十九、仿照例句的格式和修辞特点续写两个句子,使之与例句构成一组排比句。 二十、仿照例句,另写一个句子,要求能恰当地表达自己的愿望。 二十一、仿照下面一句话的句式,接着写一句话,使之与前面的内容、句式相对应,修辞方法相同。 二十二、仿照下面一句话的句式和修辞,以“思考”开头,接着写一个句子。 二十三、仿照下面例句,从ABCD四个英文字母中选取一个,以”青春”为话题,展开想象和联想,写一段运用了比喻修辞格、意蕴丰富的话,要求不少于30字。 二十四、仿照下面例句,另写一个句子。 二十五、仿照例句,另写一个句子。 二十六、下面是毕业前夕的班会上,数学老师为同学们写的一句赠言,请你仿照它的特点,以语文老师的身份为同学们也写一句。

The way的用法及其含义(一)

The way的用法及其含义(一) 有这样一个句子:In 1770 the room was completed the way she wanted. 1770年,这间琥珀屋按照她的要求完成了。 the way在句中的语法作用是什么?其意义如何?在阅读时,学生经常会碰到一些含有the way 的句子,如:No one knows the way he invented the machine. He did not do the experiment the way his teacher told him.等等。他们对the way 的用法和含义比较模糊。在这几个句子中,the way之后的部分都是定语从句。第一句的意思是,“没人知道他是怎样发明这台机器的。”the way的意思相当于how;第二句的意思是,“他没有按照老师说的那样做实验。”the way 的意思相当于as。在In 1770 the room was completed the way she wanted.这句话中,the way也是as的含义。随着现代英语的发展,the way的用法已越来越普遍了。下面,我们从the way的语法作用和意义等方面做一考查和分析: 一、the way作先行词,后接定语从句 以下3种表达都是正确的。例如:“我喜欢她笑的样子。” 1. the way+ in which +从句 I like the way in which she smiles. 2. the way+ that +从句 I like the way that she smiles. 3. the way + 从句(省略了in which或that) I like the way she smiles. 又如:“火灾如何发生的,有好几种说法。” 1. There were several theories about the way in which the fire started. 2. There were several theories about the way that the fire started.

暗示的近义词和反义词 [暗示的近义词反义词和造句]

暗示的近义词和反义词[暗示的近义词反义词和造句] 【暗示解释】:用含蓄、间接的方式使他人的心理、行为受到影响。下面小编就给大家整理暗示的近义词,反义词和造句,供大家学习参考。 暗示近义词 默示 示意 暗指 暗意暗示反义词 明说 表明 明言暗示造句 1. 他的顶级助手已经暗示那可能就在不久之后,但是避免设定具体的日期。 2. 一些观察家甚至暗示他可能会被送到了古拉格。 3. 要有积极的心理暗示,达成目标的好处不够充分,画面不够鲜明那它对你的吸引力就不够强烈,你就不易坚持下去! 4. 不要经常去试探男人,更不要以分手做为威胁,当你经常给他这种心理暗示,他的潜意识就会做好分手的打算。 5. 向读者暗示永远不必为主角担心,他们逢凶化吉,永远会吉人天相。 6. 约她一起运动,不要一下跳跃到游泳,可以从羽毛球网球开始,展示你的体魄和运动细胞,流汗的男人毫无疑问是最性感的,有意无意的裸露与靠近,向她暗示你的运动能力。 7. 正如在上一个示例所暗示的,只有在这些对象引用内存中同一个对象时,它们才是相同的。 8. 渥太华此时打出中国牌,巧妙地对美国这种行为作出警告,暗示美国如果长期这样下去的话,美国将自食其果。 9. 团长用震撼人心的嗓音喊道,这声音对他暗示欢乐,对兵团暗示森严,对前来校阅阅兵的首长暗示迎迓之意。 10. 渥太华此时打出中国牌,巧妙地对美国这种行为作出警告,暗示美国如果长期这样下去的话,美国将自食其恶果。 11. 我们需要邀请用户,为他们描述服务产品有多少好,给他们解释为什么他们需要填那些表单并且暗示他们会因此得到利益的回报。 12. 她对暗示她在说谎的言论嗤之以鼻。 14. 在力士参孙中,整首诗都强烈暗示着弥尔顿渴望他自己也能像参孙一样,以生命为代价,与敌人同归于尽。 15. 戴维既然问将军是否看见天花板上的钉子,这就暗示着他自己已看见了,当将军做了肯定的答复后,他又说自己看不见,这显然是自相矛盾。 16. 自我暗示在我们的生活中扮演着重要角色。如果我们不加以觉察,通常它会与我们作对。相反地,如果你运用它,它的力量就可以任你使唤。 17. 纳什建议太阳招兵买马,暗示去留取决阵容实力。 18. 同时,还暗示了菊既不同流俗,就只能在此清幽高洁而又迷漾暗淡之境中任芳姿憔悴。 19. 学习哲学的最佳途径就是将它当成一个侦探故事来处理:跟踪它的每一点蛛丝马迹每一条线索与暗示,以便查出谁是真凶,谁是英雄。 20. 不要经常去试探你的伴侣,更不要以分手做为威胁,试探本身就是一种不信任,当

放弃的近义词反义词和造句

放弃的近义词反义词和造句 下面就给大家整理放弃的近义词,反义词和造句,供大家学习参考。 放弃的近义词【废弃解释】:抛弃不用:把~的土地变成良田ㄧ旧的规章制度要一概~。 【丢弃解释】:扔掉;抛弃:虽是旧衣服,他也舍不得~。 放弃的反义词【保存解释】:使事物、性质、意义、作风等继续存在,不受损失或不发生变化:~古迹ㄧ~实力ㄧ~自己,消灭敌人。 放弃造句(1) 运动员要一分一分地拼,不能放弃任何一次取胜的机会。 (2) 我们不要放弃每一个成功的机会。 (3) 敌军招架不住,只好放弃阵地,狼狈而逃。 (4) 为了农村的教育事业,姐姐主动放弃了调回城市的机会。 (5) 都快爬到山顶了,你却要放弃,岂不功亏一篑?(6) 纵使遇到再大的困难,我们也要勇往直前,不轻言放弃。 (7) 逆境中的他始终没有放弃努力,仍满怀信心,期待着峰回路转的那一天。 (8) 听了同学的规劝,他如梦初醒,放弃了离家出走的想法。 (9) 因寡不敌众,我军放弃了阵地。 (10) 要日本帝国主义放弃侵华野心,无异于与虎谋皮。 (11) 永不言弃固然好,但有时放弃却也很美。

(12) 他这种放弃原则、瓦鸡陶犬的行径已经被揭露出来了。 (13) 适当放弃,做出斩钉截铁的决定,才能成为人生的赢家。 (14) 他委曲求全地放弃自己的主张,采纳了对方的意见。 (17) 我们要有愚公移山一样的斗志,坚持不懈,永远不放弃,去登上梦想的彼岸!(18) 只要有希望,就不能放弃。 (19) 为了大局着想,你应该委曲求全地放弃自己的看法。 (20) 既然考试迫在眉睫,我不得不放弃做运动。 (21) 即使没有人相信你,也不要放弃希望。 (22) 无论通往成功的路途有多艰辛,我都不会放弃。 (23) 在困难面前,你是选择坚持,还是选择放弃?(24) 无论前路多么的漫长,过程多么的艰辛,我都不会放弃并坚定地走下去。 (25) 你不要因为这点小事就英雄气短,放弃出国深造的机会。 (26) 像他这样野心勃勃的政客,怎么可能放弃追求权力呢?(27) 鲁迅有感于中国人民愚昧和麻木,很需要做发聋振聩的启蒙工作,于是他放弃学医,改用笔来战斗。 (28) 我们对真理的追求应该坚持不懈,锲而不舍,绝不能随便放弃自己的理想。 (29) 感情之事不比其他,像你这样期盼东食西宿,几个男友都捨不得放弃,最后必定落得一场空。 (30) 爷爷临终前的话刻骨铭心,一直激励着我努力学习,无论是遇到多大的困难险阻,我都不曾放弃。

way 的用法

way 的用法 【语境展示】 1. Now I’ll show you how to do the experiment in a different way. 下面我来演示如何用一种不同的方法做这个实验。 2. The teacher had a strange way to make his classes lively and interesting. 这位老师有种奇怪的办法让他的课生动有趣。 3. Can you tell me the best way of working out this problem? 你能告诉我算出这道题的最好方法吗? 4. I don’t know the way (that / in which) he helped her out. 我不知道他用什么方法帮助她摆脱困境的。 5. The way (that / which) he talked about to solve the problem was difficult to understand. 他所谈到的解决这个问题的方法难以理解。 6. I don’t like the way that / which is being widely used for saving water. 我不喜欢这种正在被广泛使用的节水方法。 7. They did not do it the way we do now. 他们以前的做法和我们现在不一样。 【归纳总结】 ●way作“方法,方式”讲时,如表示“以……方式”,前面常加介词in。如例1; ●way作“方法,方式”讲时,其后可接不定式to do sth.,也可接of doing sth. 作定语,表示做某事的方法。如例2,例3;

体面的近义词-反义词及造句

体面的近义词|反义词及造句 我们还必须迅速采取行动,为实现社会包容和人人体面工作营造有利的环境。下面是小编精选整理的体面的近义词|反义词及造句,供您参考,欢迎大家阅读。 体面的近义词: 面子、合适、美观、颜面、场合、场面、排场、得体、好看、局面 体面的反义词: 难听、寒碜、邋遢、寒酸、难看 体面造句 1、我认为,帖在墙面上的证书,并不能使你成为一个体面的人。 2、他是那里唯一的看上去很体面的人;我认为他从来没有这样好看过。 3、所有的美国人都是好的,体面的人们每天都在践行着他们的责任。 4、美国人民慷慨、强大、体面,这并非因为我们信任我们自己,而是因为我们拥有超越我们自己的信念。 5、工人就是工人,无论他们来自哪里,他们都应该受到尊重和尊敬,至少因为他们从事正当的工作而获得体面的工资。 6、然而反之有些孩子可能就是多少有些体面的父母的不良种子这一概念却令人难以接受。

7、如果奥巴马能够成就此功,并且帮助一个体面的伊拉克落稳脚跟,奥巴马和民主党不仅是结束了伊拉克战争,而是积极从战争中挽救。 8、而且,等到年纪大了退休时,他们希望能得到尊重和体面的对待。 9、爸爸,您倒对这件事处理得很体面,而我想那可能是我一生中最糟糕的一个夜晚吧。 10、有一些积极的东西,低于预期的就业损失索赔和零售销售是体面的。 11、如果你努力工作,你就能有获得一份终生工作的机会,有着体面的薪水,良好的福利,偶尔还能得到晋升。 12、体面的和生产性的工作是消除贫困和建立自给自足最有效的方法之一。 13、同时,他是一个仁慈、温和、体面的人,一个充满爱的丈夫和父亲,一个忠实的朋友。 14、几周前我们刚讨论过平板电脑是如何作为一个体面且多产的电子设备,即使它没有完整的键盘,在进行输入时会稍慢些。 15、什么才是生活体面的标准? 16、我们还必须迅速采取行动,为实现社会包容和人人体面工作营造有利的环境。 17、她告诉我人们都担心是不是必须把孩子送到国外去学习,才能保证孩子们长大后至少能过上体面正派的生活。

the-way-的用法讲解学习

t h e-w a y-的用法

The way 的用法 "the way+从句"结构在英语教科书中出现的频率较高, the way 是先行词, 其后是定语从句.它有三种表达形式:1) the way+that 2)the way+ in which 3)the way + 从句(省略了that或in which),在通常情况下, 用in which 引导的定语从句最为正式,用that的次之,而省略了关系代词that 或 in which 的, 反而显得更自然,最为常用.如下面三句话所示,其意义相同. I like the way in which he talks. I like the way that he talks. I like the way he talks. 一.在当代美国英语中,the way用作为副词的对格,"the way+从句"实际上相当于一个状语从句来修饰全句. the way=as 1)I'm talking to you just the way I'd talk to a boy of my own. 我和你说话就象和自己孩子说话一样. 2)He did not do it the way his friend did. 他没有象他朋友那样去做此事. 3)Most fruits are naturally sweet and we can eat them just the way they are ----all we have to do is clean or peel them . 大部分水果天然甜润,可以直接食用,我们只需要把他们清洗一下或去皮.

近义词反义词大全有关聆听的反义词近义词和造句

近义词反义词大全有关聆听的反义词近义词和造句 【聆听解释】:1.汉扬雄《法言.五百》:"聆听前世﹐清视在下﹐鉴莫近于斯矣。"后多用于书面语﹐常指仔细注意地听。下面就给大家聆听的反义词,近义词和造句,供大家学习参考。 嘱咐 [注释]1.叮嘱,吩咐 倾听 [注释]1.侧着头听。 2.细听;认真地听 凝听 [注释]1.聚精会神地听 谛听 [注释]注意地听;仔细听:侧耳谛听 细听 [注释]… 1. 学校应充分利用社会的各种,调动一切可以调动的力量,应尽一切可能请进名师专家,让教师和学生有较多的机会聆听大师的声音、与大师对话。这多少会机器他们向往大师、成为大师的冲动,多少会使他们觉得大师就在身边,大师并不遥远。 2. 今天妈妈带我来到了这个美丽的大安森林公园玩,这儿有漂亮的花儿和绿油油的树,草,看起来像一个我好想好想要的花园。树

上有小鸟儿在唱歌,有蝉声在帮忙和弦,树下有小朋友再安静仔细聆听著这最自然的交响曲。 3. 静静聆听那滴滴答答的声音,不知在为谁倾诉?她在偶尔低语,偶尔高唱,偶尔呻吟,偶尔叹息,生动灵活,充满了立体与层次之美,在心灵中轻轻一吻,便触发了思绪,这思绪时而短暂,时而绵长,时而深沉,时而悠远…… 4. 九月的手掌拂去小溪夏日的狂躁,用心聆听着秋日的私语,温顺地弹唱着九月醉人的秋歌,惹得天空湛蓝高远,碧空如洗。 5. 我光着脚丫,踩着海水,注视着波光粼粼的海面,听着哗哗的响声,那声音好像高超演奏家的激越的钢琴曲,又像歌唱家的雄浑的进行曲,那声音使胸膛激荡,热血奔涌,啊,我多么愿意聆听大海老人的谆谆教诲啊! 6. 雪花飘飘,寒风阵阵,我细细地聆听着寒风谱写成的有声有色的乐谱,为雪花的舞步增添一些光彩。寒风真像一位默默为雪花服务的人。过了一会儿,又为雪花写了一篇朗朗上口的诗歌,一会儿又为她热烈地鼓起了清脆的掌声。

way的用法总结大全

way的用法总结大全 way的用法你知道多少,今天给大家带来way的用法,希望能够帮助到大家,下面就和大家分享,来欣赏一下吧。 way的用法总结大全 way的意思 n. 道路,方法,方向,某方面 adv. 远远地,大大地 way用法 way可以用作名词 way的基本意思是“路,道,街,径”,一般用来指具体的“路,道路”,也可指通向某地的“方向”“路线”或做某事所采用的手段,即“方式,方法”。way还可指“习俗,作风”“距离”“附近,周围”“某方面”等。 way作“方法,方式,手段”解时,前面常加介词in。如果way前有this, that等限定词,介词可省略,但如果放在句首,介词则不可省略。

way作“方式,方法”解时,其后可接of v -ing或to- v 作定语,也可接定语从句,引导从句的关系代词或关系副词常可省略。 way用作名词的用法例句 I am on my way to the grocery store.我正在去杂货店的路上。 We lost the way in the dark.我们在黑夜中迷路了。 He asked me the way to London.他问我去伦敦的路。 way可以用作副词 way用作副词时意思是“远远地,大大地”,通常指在程度或距离上有一定的差距。 way back表示“很久以前”。 way用作副词的用法例句 It seems like Im always way too busy with work.我工作总是太忙了。 His ideas were way ahead of his time.他的思想远远超越了他那个时代。 She finished the race way ahead of the other runners.她第一个跑到终点,远远领先于其他选手。 way用法例句

终于的近义词,反义词及造句

终于的近义词,反义词及造句 …终究[注释]副词。 总:总归;毕竟;最终:我们只要把事情办好,人们终究会相信我们的|腐朽的东西终究要灭…到底[注释]1.直到尽头。 2.始终;从头到尾。 3.毕竟;究竟。 …结果[注释]结果1在一定阶段,事物发展所达到的最后状态:优良的成绩,是长期刻苦学习的~ㄧ经过一番争论…终归[注释]1.传说中神兽名。 2.终究;毕竟。 …究竟终于的反义词:起初、最初、原来、依旧、起先终于的造句:(1) 盼望了一个冬天的雪花,下午终于飘飘洒洒满天飞舞般降落。 同事们也如孩子般奔向办公室的走廊,欣喜地用手去接冰凉的小雪花再用盆子收拢些飘舞的小雪花。 隔窗望去,天地之间因突然多了这白色的小精灵而愈发显得美丽。 (2) 快乐的暑假终于到了,我可以开开心心痛痛快快地玩一顿了!当然,在这之前,我也会好好安排一下我的暑假生活,使我过个既快乐又充实的暑假,我快乐的暑假生活。 (3) 坚韧,让沙石煎熬住大海的蹂躏,终于化作璀璨的珍珠;坚韧,让天空忍受住雨水倾盆的阴霾,终于看见那一道彩虹;坚韧,让泉水忘记流进山谷崎岖的历程,终于汇入蔚蓝无垠的大海。

它的叶子正面是身绿色的,反面是浅绿的,经脉上还有一些毛绒绒的小细毛。 又过了几天,含羞草的花蕾也长出来了,圆溜溜的,紫红色,还有着一些像针一样的东西,非常美丽。 (5) 漫长而炎热的夏天终于过去了,凉爽怡人的秋天来到了。 (6) 随着天空被点燃,太阳也终于露出脸来,它没有害羞,而是大大方方地把它独特的热情展示给我们,毫不吝惜地奖光芒撒向大地。 (7) 大约过了二十分钟,太阳终于挣脱了大地妈妈的怀抱,在崇山俊岭之间冉冉升起,真像个大红球,又像气得涨红了脸。 (8) 半个月的低烧,终于有了好转,高烧了……(9) 夏天的雨后,太阳冲出乌云的包围,终于露出了整张脸,此时阳光直直的,却不呆板、单调,它们穿梭在树枝之间,织成一道道金色的丝,将鱼后的水珠串成一串金黄的珍珠。 夏天少有的凉意伴着美丽的阳光,令人沁透心脾。 (10) 终于到达了果园。 我们忽然发现,果园里还种了一些菊花。 这些菊花有红的蓝的黄的白的……它们颜色不同,姿态也不同:菊花们有的含苞欲放,有的开了一半,有的已经绽开了笑脸……千姿百态,十分美丽。 (11) 发改委终于超越了统计局,说北京人均绿地是巴黎两倍。 最牛回复:“是算上了开心农场吧?。

the_way的用法大全教案资料

t h e_w a y的用法大全

The way 在the way+从句中, the way 是先行词, 其后是定语从句.它有三种表达形式:1) the way+that 2)the way+ in which 3)the way + 从句(省略了that或in which),在通常情况下, 用in which 引导的定语从句最为正式,用that的次之,而省略了关系代词that 或 in which 的, 反而显得更自然,最为常用.如下面三句话所示,其意义相同. I like the way in which he talks. I like the way that he talks. I like the way he talks. 如果怕弄混淆,下面的可以不看了 另外,在当代美国英语中,the way用作为副词的对格,"the way+从句"实际上相当于一个状语从句来修饰全句. the way=as 1)I'm talking to you just the way I'd talk to a boy of my own. 我和你说话就象和自己孩子说话一样. 2)He did not do it the way his friend did. 他没有象他朋友那样去做此事. 3)Most fruits are naturally sweet and we can eat them just the way they are ----all we have to do is clean or peel them . 大部分水果天然甜润,可以直接食用,我们只需要把他们清洗一下或去皮. the way=according to the way/judging from the way 4)The way you answer the qquestions, you must be an excellent student. 从你回答就知道,你是一个优秀的学生. 5)The way most people look at you, you'd think a trashman was a monster. 从大多数人看你的目光中,你就知道垃圾工在他们眼里是怪物. the way=how/how much 6)I know where you are from by the way you pronounce my name. 从你叫我名字的音调中,我知道你哪里人. 7)No one can imaine the way he misses her. 人们很想想象他是多么想念她. the way=because 8) No wonder that girls looks down upon me, the way you encourage her. 难怪那姑娘看不起我, 原来是你怂恿的

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