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宣布英文Outskirts of Galaxy Clusters:inten life in the suburbs Proceedings IAU Colloquium No.195,2004A.Diaferio,ed.c 2004International Astronomical Union DOI:00.0000/X000000000000000X Internal kinematics of spiral galaxies in distant rich galaxy clusters K.J¨a ger 1,A.B¨o hm 1,B.L.Ziegler 1,J.Heidt 2,C.M¨o llenhoff21Universit¨a ts-Sternwarte G¨o ttingen,Germany,email:jaeger@uni-sw.gwdg.de 2Landessternwarte Heidelberg,Germany Abstract.We prent our project on galaxy evolution in the environment of distant rich clus-ters aiming at dintangling the importance of specific interaction and galaxy transformation process from the hierarchical evolution of field galaxies.Spatially resolved MOS spectra were gained with VLT/FORS to analyze the internal kinematics of disk galaxies.First results are shown for the clusters MS 1008.1−1224(z=0.30),Cl 0303+1706(z=0.42),and Cl 0413−6559(z=0.51).Out of 35late type cluster members,13galaxies exhibit a rotation curve of the uni-versal form rising in the inner region and passing over into a flat part.The other members have peculiar kinematics.The 13cluster galaxies for which a maximum rotation velocity could be derived are distributed in the Tully-Fisher diagram very similar to field galaxies from the FORS Deep Field with corresponding redshifts.The same is true for ven non-cluster galaxies obrved in the cluster fields.The TF-cluster spirals do not show any significant luminosity evolution as might be expected from certain clusterspecific phenomena.Contrary to that,the disturbed kinematics of the non–TF cluster spirals indicate ongoing or recent interaction pro-cess.
2K.J¨a ger et al.come clean
es a larger scatter of their sample galaxies in the TF diagram without evidence for an evolution of the zero point,the cond onefinds a trend towards brighter luminosities (0.5–1B mag)with respect tofield spirals of comparable redshifts.It is argued that either truncation of star formation or starbursts may cau an incread or decread mass–to–light ratio,respectively.
2.Project and obrvations
During5nights at the ESO–VLT we gained spectra of galaxies within7clusters in the redshift range0.3 z<0.6with FORS1&2.One of our goals was the derivation of spatially resolved RCs to analy the internal kinematics of the galaxies and to construct the TFR(Tully and Fisher1977)of distant clusters.HST/WFPC2images of the core regions were retrieved from the archive to complement our own ground–bad imaging. Here we prent results of three of the clusters,Cl0413–65(z=0.51)and MS1008–12 (z=0.30),Cl0303+17(z=0.42).Obrvations were made in1999and2000with FORS mounted at the Casgrain focus of the VLT.We ud grism600R and get a spectral resolution of R≈1200at a slitwidth of1arcc.The spatial scale was0.2arcc/pixel with a dispersion of∼1.08˚A/pixel.The total integration time was t to≈2hrs to meet our signal–to–noi requirements.
Seeing conditions ranged between0.4and1.3arcc FWHM.Two MOS tups have been obrved for each cluster,yielding116objects with apparent magnitudes in the range18.0<R<23.
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3.Data reduction and rotation curve modelling
A detailed description of the sample lection and data reduction includingfinding charts and data tables can be found in J¨a ger et al.(2004).For the derivation of position velocity diagrams we followed the way described in detail in B¨o hm et al.(2004)and Ziegler et al.(2003).Here we only give some short remarks on this topic.
All RCs were determined using either the[O ii]3727,Hβor[O iii]5007emission line. Gaussianfits have been applied stepping along the spatial axis with a medianfilter win-dow of typically0.6arccs to enhance the S/N.Since the apparent disk sizes of spirals at intermediate redshifts are only slightly larger than the slit width(1arcc),the spec-troscopy covers a substantial fraction of the two–dimensional velocityfield.Thus,the maximum rotation velocity v max(the constant rotation in the outer part of a galaxy due to the Dark Matter halo)cannot be determined“straightforwardly”from the ob-rved rotation.To tackle this problem,we simulated the spectroscopy of each galaxies’velocityfield with the respective inclination and position angle,also taking eing and luminosity weighting into ac
count.The simulated rotation curves which best reproduced the obrved ones(solid lines in Fig.1)yielded the values of v max.
4.Results and discussion
Redshifts and spectral types could be determined for89galaxies.From the50cluster members,35turned out to be late type galaxies.Only13cluster galaxies exhibit a rotation curve of the universal form rising in the inner region and passing over into a flat part.The other members have peculiar kinematics or too low S/N.For7non–cluster galaxies v max could also be measured.
Only tho rotation curves which show no strong perturbations are eligible for a determination of v max as needed for the TF diagram which is shown in Fig.2.v max
Outskirts of Galaxy Clusters:inten life in the suburbs3
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Figure1.Spatially resolved velocity profiles for12disk galaxies in the cluster MS1008–12at z=0.30.Note,panels c&d,e&f,k&l and m&n reprent the same galaxy,rsp.,but obrved with different slit positions(the rotation angles of the two MOS masks differed by67◦).δgives the angle between slit direction and apparent major axis.Panels a–p are ordered according to the distance of the galaxies from the cluster center(upper left:smallest proj.radius).Values of the maximum rotation velocity could be determined for cas a,d,e,f,g,i,o&p indicated by the label“TF”.The galaxies enter the TFR shown in Fig.2.In all other cas,the kinematics are too disturbed.In one ca(m&n),we obrve a pr
ominent bar that caus a highly asymmetric rotation curve.
could be measured for7(MS1008–12),5(Cl0413–65),and2(Cl0303+17)cluster mem-bers,respectively.Luminosities were derived from total magnitudes(measured with SExtractor,e Bertin&Arnouts(1996))of V(MS1008–12),I(Cl0413–65),and R (Cl0303+17)FORS images corrected for Galactic and intrinsic extinction,transformed to restframe Johnson B according to SED type,and calculated for aflatΩλ=0.7 cosmology(H0=70km s−1Mpc−1).
Within our TF diagram the distant cluster spirals are distributed similar to the FORS
yes or no 14K.J¨a ger et al.
Figure 2.Tully–Fisher diagram of cluster spirals in MS1008–12(z=0.30),Cl0413–65 (z=0.51)and Cl0303+17(z=0.42).Also shown are7field objects(open symbols)that were also obrved in the clusters’field–of–view.In comparison to our FORS Deep Field sample of77field galaxies with a mean redshift of0.5(small open circles),the cluster galaxies are sim-ilarly distributed and do not deviate significantly from the linearfit to the FDF sample(solid line).The cluster members follow the same trend with respect to the local TFR(thefit±3σto the Pierce&Tully1992sample is given)as the distantfield galaxies.Since we obrved mostly bright cluster galaxies,their luminosities are not significantly incread in accordance with an undisturbed evolution.(Restframe B magnitudes were calculated for aflatΩλ=0.7cosmology with H0=70km s−1Mpc−1.)
Deep Field(FDF)spirals(Ziegler et al.2002,B¨o hm et al.2004)which have been ob-rved with exactly the same instrument configuration and which reprent a similar cosmic epoch( z FDF =0.5).
No significant deviation from the distantfield TFR is vis-ible and the cluster sample has not an incread scatter,but the low number of cluster members prohibits any quantitative statistical analysis.We can conclude that the mass–to–light ratios of the obrved distant cluster spirals cover the same range as the distant field population indicating that no clusterspecific phenomenon dramatically changed the stellar populations.In particular,there was no starburst in the recent past of the ex-amined cluster galaxies that would have significantly rin their luminosities.Since we mostly lected bright galaxies,the cluster members occupy a region in the TF diagram where no significant luminosity evolution is visible with respect to the local TFR.
Outskirts of Galaxy Clusters:inten life in the suburbs5 On the other hand,this conclusion is true only for tho objects that enter the TF diagram and is not valid for the whole cluster sample.More than half of our cluster galaxies can not be ud for a TF analysis due to their peculiar kinematics not follow-ing the“ri–turnover–flat”RC shape of large,isolated spirals.This is in contrast to the smaller fraction of peculiar curves in our sample of the FDF spirals.The objects with peculiar RCs may actually be subject to ongoing or recent interactions.Indeed, a morphological classification of the cluster spirals in terms of their asymmetry indices (Abraham et al.1996)reveals that they have a slightly higher degree of asymmetry on the mean than the kinematically less disturbed ones.A correl
ation between morphological and kinematical disturbance hints to a common origin for both in“strong”interactions like clo encounters with tidal effects,accretion events or even mergers.Such process most probably also influence the stellar populations of a galaxy changing its integrated luminosity as well.
No trend is visible of the RC form with(projected)clustercentric distance(cf.Fig.1). But since all obrved galaxies are located within the virial radius,this is in compliance with dynamical models in which the galaxy population of a cluster is well-mixed within that region.In particular,we most probably do not have any new arrivals from thefield in our sample.
Acknowledgements
Bad on obrvations with the ESO–VLT(64.O–0158&64.O–0152).This work has been supported by the Volkswagen Foundation(I/76520)and the Deutsche Forschungs-gemeinschaft(Fr325/46–1and SFB439).
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