document: spectra of type 1 agn show a diversity of broad and narrow emission lines that provide direct insights into the structure and kinematics of photoionized , and otherwise excited , gas in the vicinity of the putative central massive object . 
   broad emission lines , like much studied h@xmath0 ( e.g. , * ? ? ? 
   * hereafter z10 ) , are thought to arise in or near an accretion disk acting as the fuel reservoir for the central supermassive black hole ( log m@xmath1 m@xmath2 ) . 
   h@xmath0 shows a diversity of line widths as well as profile shifts and asymmetries @xcite . despite this diversity 
   some systematics have emerged and are best highlighted via the concept of two type 1 agn populations @xcite . 
   population a show the smallest broad - line widths fwhm h@xmath0=1000 - 4000 and includes the narrow line seyfert 1 ( nlsy1 ) sources ( fwhm @xmath3 2000 ) . 
   a h@xmath0 profiles are currently best fit by a single lorentz function . 
   population b sources show fwhm h@xmath0=4000 - 12000 and require two gaussians ( one unshifted and one redshifted ) for a reasonable profile description . 
   `` broad - line '' h@xmath0 profiles as narrow as fwhm = 500 @xcite and as broad as fwhm = 40000 @xcite have been found . 
   a is predominantly radio - quiet while pop . 
   b involves a mix of radio - quiet and the majority of radio - loud quasars . 
   broad- and narrow - line profile shifts are known and the phenomenology can be confusing . 
   narrow emission lines like [ oiii]5007 are regarded as a reliable measure of the local quasar rest frame except in the case of `` blue outliers '' , usually found in sources with fwhm h@xmath0= 1500 - 3500 and weak [ oiii ] @xcite . 
   blue outliers show [ oiii ] blueshifts as large as @xmath41000 . no pop . 
   b sources with blueshifted [ oiii ] are known at low z ( or luminosity ) . careful use of [ oiii ] and h@xmath0 narrow line as rest frame measures suggests that broad h@xmath0 in pop . 
   a sources rarely shows a systematic red or blue shift above the fwhm profile level . a blueshifted component or asymmetry 
   is observed in some extreme feii strong pop . a sources @xcite . 
   b sources show more complex line shift properties . 
   the h@xmath0 profile usually shows two components : 1 ) a `` classical '' broad component ( bc ; fwhm = 4000  5000 ) with zero or small ( red or blue ) shift , and 2 ) a very broad ( vbc ; 10000 ) and redshifted ( @xmath51000 ) component . 
   composites involving the 469 brightest sdss - dr5 quasars suggest that these two components represent the underlying stable structure of h@xmath0 in pop . 
   b sources . 
   broad feii emission has been found in type 1 quasars since the era of photographic spectroscopy in the 60s . 
   feii emission blends are almost ubiquitous in a sample of the brightest ( usually highest s / n ) sdss quasars ( z10 ) . 
   circumstantial evidence has accumulated supporting the assumption that feii emission arises in or near the emitting clouds that produce other low ionization lines like h@xmath0 ( see e.g. , @xcite ) . 
   fwhm feii appears to correlate with fwhm h@xmath0  over the full range where feii can be detected ( fwhm=1000 - 12000 ) . 
   this can be clearly seen at low @xmath6  by observing the shape ( e.g. , smoothness ) of the feii 4450 - 4700   blue blend ( and the feii multiplet 42 line at 5018  ) near [ oiii]5007 . in pop . 
   a sources the blend resolves into individual lines while it becomes much smoother in pop . 
   b sources . sources with the strongest feii emission also show a weakening of h@xmath0 emission as expected if the latter is collisionally quenched in the same dense medium where strong feii emission can be produced @xcite . 
   obviously systematic line shifts place important constraints on models for the geometry and kinematics of the broad line region . 
   the most famous example involves a systematic blueshift of high ionization lines ( e.g. , civ 1549 ) relative to low ionization lines ( e.g. , balmer ) especially in pop . a sources ( e.g. , * ? ? ? 
   * ; * ? ? ? 
   * ; * ? ? ? 
   * ; * ? ? ? 
   evidence was recently advanced ( * ? ? ? 
   * hereafter h08 ) for the existence of a _ 
   systematic _ redshift of feii relative to [ oiii]5007 ( and hence the balmer lines ) in a majority of type 1 quasars . 
   this result , along with a narrower estimated feii line width , has been ascribed to feii emission arising in a region with dynamics dominated by infall and located at larger radius than the region producing the bulk of h@xmath0 . 
   h08 argue that the amplitude of the shifts correlates inversely with source eddington ratio ( l / l@xmath7@xmath8@xmath9 ) . 
   interpretations for such an feii redshift have already appeared @xcite reflecting the potential importance of such a first - order kinematic signature . 
   having worked on line spectra and profile shifts for many years we were surprised by the h08 claims and decided to test the hypothesis of a systematic feii redshift . 
   could we have missed it ? 
   first let us consider what we know . 
   a quasars show relatively symmetric unshifted lorentz - like h@xmath0 profiles with fwhm@xmath34000 . in our work using the brightest ( @xmath10 17.5 or @xmath11 17.5 ; @xcite ) sdss dr5 quasars we processed spectra for @xmath4260 pop . a sources ( from a sample of 469 quasars ; z10 ) and we found no evidence for a systematic shift of feii lines relative to h@xmath0 or . 
   such an feii shift should be easiest to detect in the brightest pop . a sdss spectra with narrowest broad - line profiles and strongest feii emission . 
   it is immediately suspicious that more and larger feii redshifts are claimed for pop . 
   b sources . in only one pop . 
   a source in our sample sdss j0946 + 0139 do we find a large h@xmath0 peak ( 90@xmath12 intensity level ) redshift of 1830 . 
   this source is similar to oq208 ( @xcite and discussed in h08 ) which shows @xmath13 @xmath142000 . 
   sdss j0946 is the only pop . 
   a source with a large feii redshift in our z10 sample ( 1/260 ) . 
   z10 found 19 quasars with an h@xmath0 peak ( 9/10 fractional intensity ) blueshifted more than -320 and 4 sources with the peak redshift more than + 320 . the remaining 241 pop . 
   a sources showed no significant h@xmath0  peak shift ( figure 8 of z10 ) . 
   best feii template fits to these sources show no significant difference in centroid redshift between feii and h@xmath0 . 
   there are two possible causes of small and spurious h@xmath0 ( or feii ) shifts : 1 ) host galaxy contamination and 2 ) blue outliers.except in rare cases host galaxy contamination is unlikely to induce systematic redshifts with the amplitudes reported by h08 . 
   extreme blue outliers with [ oiii ] blueshifts in the range 400 - 1000 are rare and therefore can not be the cause of the large and systematic shifts reported in h08 . 
   in fact h08 selection criteria rejected sources likely to be seriously affected by 1 ) or 2 ) . 
   h08 chose 4000 + sources from sdss dr5 with computed s / n @xmath15 10 . 
   z10 also used dr5 where @xmath494% of sources show s / n @xmath15 10 . 
   our sample was magnitude - limited with a slightly shallower redshift upper limit ( z=0.7 instead of 0.8 ) . 
   why do we reach different conclusions about feii shifts ? 
   a big part of the answer could involve how s / n was computed . 
   compute s / n over the range 44305500@xmath16 . 
   this procedure overestimates the quality of the data because it includes major emission lines in the computation . 
   we compute s / n in the range 5600 - 5800@xmath16 , which is free of strong lines and represents as close as one can approach to an estimate of continuum s / n near h@xmath0 . using our range the h08 sample shows mean and median s / n values of 10.6 and 7.4 , respectively ; approx . 
   65% show s / 
   n @xmath3 10 . 
   we find that only 182 spectra of our bright sample are included in the h08 s . the majority of the h08 s sources are lower s / n than those in our sample . 
   one can not estimate reliable feii line shifts using individual sdss spectra for sources fainter than about g@xmath417 - 17.5 . in rough order of importance 
   our studies indicate that the accuracy of feii shift measures depends on : 1 ) feii strength and feii / h@xmath0  profile widths , 2 ) spectral s / n and 3 ) if estimates depend heavily on fits to the 4430 - 4680   blend , strength of heii 4686 emission . typical individual spectra used by h08 _ show _ too low s / n to allow convincing conclusions about feii shift and width  typical parameter uncertainties for individual sources are much larger than the ones connected with our high s / n composites ( for a typical a2 source with s / n@xmath1720 uncertainties of shift estimates are larger than @xmath181500 ) . 
   individual source spectra with large quoted feii redshift and s / n near the sample median were extracted from the h08 sample and specfit modelled . using an feii template with fixed shifts ranging from zero up to the largest values quoted by h08 
   , @xmath19 can not distinguish between zero and e.g. , 1000 redshift in the majority of the sources . 
   the best recourse is to generate high s / n composite spectra . 
   h08 argue that one can not confirm or refute the existence of a systematic feii redshift using composite spectra because of the large dispersion of fwhm , shifts and flux values for both h@xmath0 and feii . 
   this is likely true for composites generated from random subsamples of sources but not true if one generates composites over more limited ranges of parameter values . 
   one can generate binned composites over limited ranges of fwhm h@xmath0 and feii strength using the 4de1 formalism ( @xcite ; z10 ) . 
   4de1 bins a2 ( fwhm h@xmath0= 1000 - 4000 , 0.5 @xmath20 @xmath20 1.0 ) and b1 ( fwhm h@xmath0=4000  8000 , @xmath20 0.5 ) are of particular interest because they include the largest numbers of sources in random samples 
   . specfit analysis ( @xcite ; details in @xcite ) of an a2 median composite involving n = 130 z10 sources ( s / n  90 ) gives a best - fit consistent with zero feii redshift . 
   the situation for the b1 composite ( n=131 sources from z10 ; s / n  110 ) is less constraining because lines are broader and feii weaker . 
   table 1 reports feii template shifts and 2@xmath21  uncertainties for specfit tests discussed in this paper . 
   we also report peak shifts of  bc extracted from the best specfit solutions along with  `` core '' shifts measured at the centroid of the line peak after  nc subtraction . in no case 
   do we find a significant shift between feii and the rest frame or between feii and . 
   we also do not find any significant feii shifts if we restrict to sources with l / l@xmath7 ratio @xmath22  ( h08 suggested the shifts might be largest for low l / l@xmath7 sources ) .      since we find no evidence for systematic feii redshifts in our z10 bright quasar sample composites it is useful to generate feii shift composites using the h08 sample . 
   we generate them within the 4de1 context thereby restricting the ranges of fwhm h@xmath0 , feii relative strength ( and likely also fwhm feii ) for each composite . 
   since the distribution of feii shifts shown in h08 is continuous we focus on the sources with largest quoted shift values . 
   if these shifts are not confirmed then smaller shifts are even less likely to be real . 
   we therefore focus on constructing median composites for all h08 sources falling in 4de1 bins a2 and b1 with h08 feii redshift estimates @xmath23  ( figure 1 ) . 
   two composites were constructed for each spectra bin : 1 ) one with no restriction on feii width ( h08 do not constrain fwhm feii in their template fits so it is sometimes very different from fwhm h@xmath0 ) and 2 ) one with feii width constrained to the fwhm range of h@xmath0  in a particular bin ( i.e. , @xmath24  for a2 and @xmath25  for b1 ) . 
   upper and lower panels of figure 1 show bins a2 ( fwhm h@xmath0 @xmath3 4000 ) and b1 ( fwhm h@xmath0=4000 - 8000 ) , respectively ( n=156 for bin a2 and n=240 for bin b1 ) . 
   the s / n @xmath4 55 - 60 for both composites . 
   spectra show best - fit specfit models superimposed . 
   the left and center panels involved feii templates fixed to the best fit and 1500 shifts , respectively . 
   our template prescription is described in @xcite    graphical results for the best - fits are shown in the right panels of figure 1 . 
   fits were performed over the range @xmath17 4470  5450  , where feii and continuum emission account for the total flux making it the safest region for normalized @xmath26  computations . 
   @xmath26  values are shown for the range of adopted feii shifts . in order to estimate confidence intervals we considered a set of fits with displacements @xmath27= + @xmath28 , for integer @xmath29 , along with the best fit and a few additional @xmath27   cases in proximity to the minimum @xmath26 . 
   one can see a clear preference for zero or near - zero fits . 
   the significance of @xmath26 variations is described by @xmath30  statistics appropriate for ratios of @xmath26  values @xcite . given the large number of degrees of freedoms in the sampling range ( 4500  4630 , 5040  5090 , 5310  5360  ) any @xmath26  differences between two fits become significant at a 95%  confidence level if @xmath31 . 
   the @xmath26   values indicate that zero shift and `` best shift '' values in table 1 are not significantly different . 
   all fits involving shifts @xmath5 500  are statistically significant . 
   the middle panel of figure 1 upper row demonstrates visually that the fit with @xmath13 = + @xmath32  ( and even more the fits with larger displacement ) do not reproduce the observed feii emission . 
   both the residuals and @xmath19  results rule out any systematic redshift for at least half of the h08 sample ( pop . 
   note especially the fits to the two relatively isolated multiplet 42 feii lines between h@xmath0 and [ oiii]4959 and on the red wing of [ oiii]5007 . 
   the redshifted fit fails to include the blue side of the 4450  4700 blend and the red side is confused by the frequent presence of heii 4686 . 
   the latter line is not mentioned in the h08 study leaving us to conclude that it was not included in their fits . 
   it can certainly give the impression of a redshift of the feii blue blend , which is the most useful feii diagnostic in the optical spectra of low redshift quasars ( the red feii blend is frequently affected by coronal lines as well as mgii host galaxy absorption in lower redshift sources ) 
   . pioneering principal component analysis of the bqs survey @xcite found that heii4686 equivalent width anticorrelates with sources luminosity ( it is eigenvector 2 ) . there is a tendency for the h08 sources with largest feii redshifts to favor a smaller and lower ( @xmath33 ) range of source luminosity than those with near zero shifts ( @xmath34 ) . 
   thus the effect of heii will tend to play a larger role in the sources where the largest feii redshifts have been found . 
   show composite spectra for five bins of feii redshift in their figure 12 . 
   the three bins involving largest feii redshift sources show a prominent heii signature that , if not subtracted , will increase the apparent significance of any assumed feii redshift . 
   only the bin involving sources with no feii redshift ( within the uncertainties ) shows no evidence of heii emission . 
   figure 9a of h08 suggests that a larger fraction of quasars with fwhm h@xmath35 4000 ( population b ) show large feii redshifts . 
   the lower panels of our figure 1 show specfit models superimposed on a b1 median composite constructed from all h08 sources with quoted feii redshift greater than 1000 . 
   the situation is certainly more ambiguous than for the a2 composite . 
   it is hard to identify individual feii features . 
   lines are broad , feii is weak and under these conditions there are serious limitations on the reliability of fwhm and shift estimates for feii ( cf . fig . 3 of @xcite ) . 
   the same analysis as done for a2 composite shows much poorer constraints on the feii shift . 
   the best fit yields @xmath13 @xmath36  but is not distinguishable from a zero shift solution . 
   if one actually computes @xmath26  values over the ranges 4474  4640  , 5040  5105  , 5320  5400  , the @xmath26   monotonically increases from 0 shift ( figure 1 , lower rightmost panel ) , although the increase remains insignificant until @xmath17 1100 , where @xmath37 . 
   b1 feii is too faint and the lines are too broad to make inferences about line shifts and widths . 
   the claim of large feii shifts are not , and can not be , confirmed . 
   @xcite recently report an feii study of sdss quasars and any feii redshifts they measure ( their figure 16 ) are much smaller than those reported by h08 ( the average feii shift relative to the narrow lines is 100 @xmath18 240 ) .    returning to our previous list of major sources of uncertainty for feii shift and fwhm estimates leads us to suggest that low spectral s / n and above average heii strength are the culprits . 
   the fit to the 4430  4680 blue blend drives the best fit @xmath19 results . 
   the exclusion of heii4686 from the h08 fits likely results in a tendency for heii to `` redshift '' the blue feii blend . 
   this effect in a typically low luminosity sample , where heii is stronger than average , likely drove the conclusion that feii was systematically redshifted . 
   we tested this conclusion omitting the heii line from our fits to the bin a2 and b1 composites generated from the h08 sample . 
   feii shifts in lines 2 and 5 of table 1 increase from -60 to + 770km / s and from 730 to 1570km / s , respectively . 
   the more constraining a2 results suggest that heii can produce the entire systematic redshift claimed by h08 . 
   we _ do not _ confirm large feii redshifts relative to narrow [ oiii ] and broad h@xmath0  emission in type 1 agn but can not rule out the existence of small red ( or blue ) shifts in particular subsamples . 
   fitting median composites built from spectra with large claimed feii shifts ( @xmath23 ) indicates small shifts with an upper limit @xmath17 300  for bin a2 . in the case of b1 
   the best fit suggests @xmath17700  but the shift is very poorly constrained . in both cases the shifts are not significantly different from 0 . 
   these results do not support the origin of feii emission from a dynamical disjoint region from the one emitting the broad core of . 
   our result also challenges the usefulness of feii shift as orientation parameter . 
   small systematic shifts of feii with respect to the rest frame seem plausible but a reliable analysis is possible only on spectra of high s / n ratio . 
   lcccccc a2 - z10 & -40 @xmath18 90 & 10 & 0 & @xmath38 & 130 + a2 - h08 , @xmath39 & -60 @xmath18 400 & 80 & 90 & 70 & 156 + a2 - h08 , @xmath40 & -160 @xmath18 375 & 100 & 10 & 45 & 194 + b1 - z10 & -340 @xmath18 400 & -150 & -80 & @xmath38 & 131 + b1 - h08 , @xmath39 & + 730@xmath41 & 0 & 100 & @xmath38 & 240 + b1 - h08 , @xmath40 & + 180 @xmath18 450 & -80 & 40 & @xmath38 & 410 + b1 - h08 @xmath42 z10 , @xmath40 & -150 @xmath18 470 & -170 & -140 & 45 & 22 +
summary: we test the recent claim by hu et al . 
   ( 2008 ) that feii emission in type 1 agn shows a systematic redshift relative to the local source rest frame and broad - line h@xmath0 . 
   we compile high s / n median composites using sdss spectra from both the hu et al . sample and our own sample of the 469 brightest dr5 spectra . 
   our composites are generated in bins of fwhm h@xmath0 and feii strength as defined in our 4d eigenvector 1 ( 4de1 ) formalism . 
   we find no evidence for a systematic feii redshift and consistency with previous assumptions that feii shift and width ( fwhm ) follow h@xmath0 shift and fwhm in virtually all sources . 
   this result is consistent with the hypothesis that feii emission ( quasi - ubiquitous in type 1 sources ) arises from a broad - line region with geometry and kinematics the same as that producing the balmer lines .