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Intracluster Planetary Nebulae in the Virgo Cluster I.Initial Results John J.Feldmeier 1and Robin Ciardullo 1Department of Astronomy and Astrophysics,Penn State University,525Davey Lab,University Park,PA 16802and George H.Jacoby Kitt Peak National Observatory,P.O.Box 26732,Tucson,AZ 85726ABSTRACT We report the initial results of a survey for intracluster planetary nebulae in the Virgo Cluster.In two 16′×16′?elds,we identify 69and 16intracluster planetary nebula candidates,respectively.In a third 16′×16′?eld near the central elliptical galaxy M87,we detect 75planetary nebula candidates,of which a substantial fraction are intracluster in nature.By examining the number of the planetaries detected in each ?eld and the shape of the planetary nebula luminosity function,we show that 1)the intracluster starlight of Virgo is distributed non-uniformly,and varies between subclumps A and B,2)the Virgo Cluster core extends ～3Mpc in front of M87,and thus is elongated along the line-of-sight,and 3)a minimum of 22%of Virgo’s stellar luminosity resides between the galaxies in our ?elds,and that the true number may be considerably larger.We also use our planetary nebula data to argue that the intracluster stars in Virgo are likely derived from a population that is of moderate age and metallicity.
Subject headings:planetary nebulae:general —galaxies:intergalactic medium —galaxies:interactions —clusters:individual:Virgo
1.Introduction
The concept of intracluster starlight was ?rst proposed by Zwicky (1951),when he claimed to detect excess light between the galaxies of the Coma cluster.Follow-up photographic searches for intracluster luminosity in Coma and other rich clusters (Welch &Sastry 1971;Melnick,
White,&Hoessel1977;Thuan&Kormendy1977)produced mixed results,and it was not until the advent of CCDs that more precise estimates of the amount of intracluster starlight were made(cf.Guldheus1989;Uson,Boughn,&Kuhn1991;V′ichez-G′o mez,Pell′o,&Sanahuja1994; Bernstein et al.1995).All these studies su?er from a fundamental limitation:the extremely low surface brightness of the phenomenon.Typically,the surface brightness of intracluster light is less than1%that of the sky,and measurements of this luminosity must contend with the problems presented by scattered light from bright objects and the contribution of discrete sources below the detection limit.Consequently,obtaining detailed information on the distribution,metallicity,and kinematics of intracluster stars through these types of measurements is extremely di?cult,if not impossible.
An alternative method for probing intracluster starlight is through the direct detection and measurement of the stars themselves.Recent observations have shown this to be possible.In their radial velocity survey of19planetary nebulae(PN)in the halo of the Virgo Cluster galaxy NGC4406(M86),Arnaboldi et al.(1996)found3objects with v>1300km s?1;these planetaries are undoubtably intracluster in origin.Similarly,Ferguson,Tanvir,&von Hippel(1998)detected Virgo’s intracluster component via a statistical excess of red star counts in a Hubble Space Telescope(HST)Virgo?eld over that in the Hubble Deep Field.Finally,intracluster stars have been unambiguously identi?ed from the ground via planetary nebula surveys in Fornax(Theuns &Warren1997)and Virgo(M′e ndez et al.1997;Ciardullo et al.1998).
Motivated by these results,we have begun a large scale[O III]λ5007survey of intergalactic ?elds in Virgo,with the goal of mapping out the distribution and luminosity function of intracluster planetary nebulae(IPN).Depending on the e?ciency of tidal stripping,Virgo’s intracluster component is predicted to contain anywhere from10%to70%of the cluster’s total stellar mass(Richstone&Malumuth1983;Miller1983).A survey of several square degrees
of Virgo’s intergalactic space with a four meter class telescope should therefore detect several thousand PN,and shed light on both the physics of tidal-stripping and on the initial conditions of cluster formation.Here,we present the?rst results of our survey.
2.Observations and Reductions
On1997March6-9and16,we imaged the Virgo Cluster through a44?A wide redshifted[O III]λ5007?lter(central wavelength,λc=5027?A)and a267?A wide o?-band?lter(λc=5300?A)with the prime focus camera of the Kitt Peak4-m telescope and the T2KB2048×2048Tektronix CCD. In this initial survey,three16′×16′?elds were chosen for study:one located at the isopleth center of Virgo subclump A approximately52′north and west from M87,one～34′north and east of the giant elliptical NGC4472in subclump B,and one～13′.8north of M87,also in subclump A(For the de?nitions of the subclumps,see Binggeli,Tammann,&Sandage1987).The conditions during the bulk of the observations were variable in both seeing and transparency.However,at least one image of each?eld was taken on the photometric nights of1997Mar8and9.These photometric
images served to calibrate the remaining frames,and allowed us to put all our measurements on a standard system.
The exact coordinates of the?eld centers,as well as a summary of the observations appear in Table1.Figure1displays the locations of our three?elds,along with the locations of other detections of Virgo’s intracluster stars:M86(via PN spectroscopy;Arnaboldi et al.1996),M87 (via PN imaging;Ciardullo et al.1998),an HST Virgo?eld(via excess red star counts;Ferguson, Tanvir,&von Hippel1998),and a blank Virgo?eld observed with the William Hershel Telescope (via PN imaging;M′e ndez et al.1997).
Our survey technique was as described in Jacoby et al.(1989)and Ciardullo,Jacoby,&Ford (1989b).Planetary nebula candidates were identi?ed by“blinking”the sum of the on-band images against corresponding o?band sums,and noting those point sources which were only visible in [O III].This procedure netted76planetary nebula candidates in Field1,16PN in Field2,and 75in Field3.The magnitudes of the IPN were then measured relative to bright?eld stars via the IRAF version of DAOPHOT(Stetson1987),and placed on a standard system by comparing large aperture measurements of?eld stars on the Mar8and9images with similar measurements of Stone(1977)standard stars.Finally,monochromatic?uxes for the PN were computed using the techniques outlined in Jacoby,Quigley,&Africano(1987),Jacoby et al.(1989)and Ciardullo, Jacoby,&Ford(1989b).These were converted to m5007magnitudes using:
m5007=?2.5log F5007?13.74(1) where F5007is in units of ergs cm?2s?1.
We note here that our m5007magnitudes carry an additional uncertainty which is unique to IPN photometry.In order to compare the monochromatic?ux of an emission line object with the ?ux of a continuum source(i.e.,a standard star),the transmission of the?lter at the wavelength of the emission line must be known relative to its total integrated transmission(cf.Jacoby,Quigley, &Africano1987).For PN observations within other galaxies,this quantity is known(at least, in the mean)from the recessional velocity and velocity dispersion of the target galaxy.However, for our intergalactic PN survey,we do not know a priori what the kinematic properties of the target objects are,and hence we do not know the mean wavelength of their redshifted[O III]
λ5007emission lines.In deriving our monochromatic[O III]λ5007magnitudes,we have assumed that the velocity dispersion of the intracluster PN follows that of the Virgo Cluster as a whole (cf.Binggeli,Sandage,&Tammann1985),but this may not be true.Although the systematic error introduced by this uncertainty is small(～5%),the e?ect may be important for individual objects.
2.1.Obtaining a Statistical Sample
Before we can compare the numbers and luminosity functions of IPN,we must?rst determine the photometric completeness limit in each?eld,and de?ne a statistical sample of objects.Because our data were taken in mostly blank?elds,our ability to detect IPN was not a strong function of position.We therefore used the results of Jacoby et al.(1989)and Hui et al.(1993)and equated our limiting magnitude for completeness with a signal-to-noise of9.This is approximately the location where the PNLF(which should be exponentially increasing at the faint end)begins to turn down.The relative depth of each?eld derived in this way also agrees with that expected from measurements of the seeing and mean transparency on the individual images.
In addition to excluding faint sources,we must make one other modi?cation to the IPN luminosity function.Any galaxy that is within,or adjacent to our data frames,can potentially contaminate our IPN sample with PN still bound to their parent galaxies.Because PN are relatively rare objects,this source of contamination is unimportant for the small,low luminosity, dwarf galaxies that are scattered throughout the Virgo Cluster.However,PN in the halos of bright galaxies can be mistaken for intracluster objects,and must be taken into account.
In Fields1and2,there is only one contaminating object of any consequence,NGC4425,a relatively bright(0.2L?)lenticular galaxy on the extreme western edge of Field1.From numerous observations(examples include Jacoby,Ciardullo,&Ford1990;Ciardullo et al.1989a),PN very closely follow the spatial distribution of galaxy starlight.We therefore used surface photometry measurements to exclude seven of our PN candidates that fell within2′.4of NGC4425’s nucleus. From the B-band surface photometry of Bothun&Gregg(1990),this distance corresponds to approximately?ve e?ective radii or seven disk scale lengths.Without these objects,we have69 and16IPN candidates in Fields1and2,respectively,and a total of44and9objects in the photometrically complete samples.
For Field3,which has a total of47objects in its photometrically complete sample,the situation is more complex.Because the?eld is only13′.8from the center of M87,some fraction of the objects in this region are probably bound to the galaxy.The angular distribution of the 75planetary candidates does roughly follow the gradient de?ned by the M87surface brightness measurements of Caon,Capaccioli,&Rampazzo(1990),and this does suggest an association with the galaxy.However,these data,by themselves,do not exclude the possibility that a large fraction of our PN are intracluster in origin.Indeed,since intracluster stars contribute luminosity just as galactic stars do,it is di?cult to distinguish intracluster light from galactic light from surface photometry alone.The situation is further complicated by the recent discovery of an extremely large,highly elongated,low surface brightness halo which surrounds M87and extends～15′on the sky(Weil,Bland-Hawthorn,&Malin1997).This structure is so large,that it is probably not all bound to the galaxy.The complexity of the region makes it impossible to determine the precise number of galactic PN contaminating the intracluster counts of Field3using surface photometry. We will return to this issue in§3below.
We note that there is one other possible source of contamination to our intracluster PN sample.Any object that emits a large amount of?ux in our redshiftedλ5007?lter,but is undetectable in the o?band?lter will be mistaken for a planetary nebula.Thus,distant objects, such as gas-rich starburst galaxies or quasars,could have enough?ux in a redshifted emission line to be detected in our survey.In practice,however,this is extremely unlikely.The emission lines of importance are[O II]λ3727at z～0.35and Lyαat z～3.1.From surveys of high-redshift quasars(Schmidt,Schneider,&Gunn1995),we should expect much less than one z=3.1 bright quasar in our three?elds combined.Additionally,since our PN candidates have point-like point-spread-functions,those z～0.35galaxies with linear extents greater than～10kpc should have all been excluded on the basis of their angular size.These and similar arguments made by other authors(Theuns&Warren1997;M′e ndez et al.1997),imply that contamination from background sources is probably not signi?cant in our survey.
The?nal luminosity functions for our3?elds are plotted in Figure2.For comparison,a sample of suspected intracluster PN’s from M87’s inner halo(Ciardullo et al.1998)are also plotted.
3.The Distribution of Intracluster Stars
The most obvious feature displayed in Figure2is the dramatically di?erent numbers of IPN in Fields1&2.Although the survey depths of the three regions di?er(due to di?erences in sky transparency and seeing),it is clear that the density of intracluster objects in Field1at the center of subclump A is much larger than that in Field2.After accounting for the di?erent depths,the PN density in Field3,near M87,is smaller by a factor of at least two,and the number of PN in Field2,which is near the edge of the6degree Virgo Cluster core in subclump B,is down by a factor of～4.This behavior is quite intriguing.
The fact that subclump B has fewer PN than subclump A can probably be attributed
to cluster environment.It is well known that subclump B has fewer early-type galaxies than subclump A(Binggeli,Tammann,&Sandage1987).If ellipticals and intracluster stars have a related formation mechanism(i.e.,galaxy interactions),then a direct correlation between galaxy type and stellar density in the intergalactic environment might be expected.
What is harder to understand is the high IPN density in Field1.Although galaxy isopleths place the Virgo Cluster center in Field1(Binggeli,Tammann,&Sandage1987),X-ray data clearly demonstrate that the true center of the cluster is at M87(B¨o hringer et al.1994).The reason for the o?set is a subcluster of galaxies associated with M86.Kinematic data(Binggeli,Popescu,& Tammann1993)and ROSAT X-ray measurements(B¨o hringer et al.1994)both show that the center of Virgo subclump A is contaminated by a separate group of galaxies which is falling in from the far side of the cluster.This interpretation is con?rmed via direct distance measurements using the planetary nebula luminosity function(Jacoby,Ciardullo,&Ford1990)and surface
brightness?uctuation method(Ciardullo,Jacoby,&Tonry1993;Tonry et al.1997):both place M86～0.3mag behind M87.At this distance,the PN associated with M86and its surroundings should be beyond the completeness limit of our survey,and should not be contributing to our PN counts.The observed IPN density of Field1should therefore be smaller than that measured near M87,not greater.
A second feature of Figure2is the slow fall-o?of the bright-end of Field3’s planetary nebula luminosity function(PNLF).Observations in～30elliptical,spiral,and irregular galaxies have demonstrated that a system of stars at a common distance will have a PNLF of the form:
N(M)∝e0.307M[1?e3(M??M)](2)
where M?≈?4.5(Jacoby et al.1992).In no isolated galaxy has the PNLF ever deviated from this form.However,in a cluster environment such as Virgo,the?nite depth of the cluster can distort the PNLF,as PN at many di?erent distances contribute to the observed luminosity function.Due to the lack of survey depth in Field1,and small number of PN in Field2,we cannot determine whether the PNLFs of these?elds di?er from the empirical function.However the PNLF of Field3 is clearly distorted,in the manner identical to that found by Ciardullo et al.(1998)in their survey of the envelope of M87.
Figure3illustrates this e?ect in more detail.In the?gure,we?rst compare the observed PNLF of Field3to the most likely empirical curve(solid line)as found via the method of maximum likelihood(Ciardullo et al.1989a).The?t is extremely poor,and a Kolmogorov-Smirnov test rejects the empirical law at the93%con?dence level.The reason for the poor?t is simple: the presence of bright,“overluminous”objects forces the maximum-likelihood technique to?nd solutions which severely overpredict the total number of bright PN in the?eld.
There is only one plausible hypothesis for the distorted PNLF and the overabundance of bright PN—the presence of intracluster objects.An instrumental problem is ruled out,since the bright-end distortion has also been seen in data taken of M87’s envelope two years earlier with a di?erent?lter and under di?erent observing conditions(Ciardullo et al.1998).Similarly, extreme changes in metallicity cannot explain the discrepancy.Unless the bulk of the intracluster stars are super metal-rich([O/H]>～0.5),abundance shifts can only decrease the luminosity of the[O III]λ5007line,not increase it(Dopita,Jacoby,&Vassiliadis1992;Ciardullo&Jacoby 1992).Finally,neither population age nor the existence of dust is a likely scenario:the former requires an unreasonably young(<0.5Gyr)age for M87’s stellar envelope(Dopita,Jacoby,& Vassiliadis1992;M′e ndez et al.1993;Han,Podsiadlowski,&Eggleton1994),and the latter implies a signi?cant gradient in foreground extinction between2and7e?ective radii from M87’s center.
Thus,one is left with the hypothesis,?rst presented by Jacoby(1996)and Ciardullo et al. (1998),that intracluster PN are responsible for the distorted PNLF.From our own study,and that of others(Arnaboldi et al.1995;M′e ndez et al.1997;Ferguson,Tanvir,&von Hippel1998),it is clear that a signi?cant fraction of intracluster stars exist in Virgo,and some of these stars should be positioned in front of M87along the line-of-sight.The existence of foreground PN naturally
explains the existence of“overluminous”PN,and is supported by the fact that the brightest PN in Field3are of comparable magnitude to the brightest objects found in the Ciardullo et al.(1998) survey of M87.
The distorted PNLF gives us a way to estimate a lower limit to the number of IPN in Field3. To do this,we plot a dashed line in Figure3,which represents the expected luminosity function of M87planetaries using the observed PNLF distance modulus of the inner part of the galaxy (m?M=30.87;Ciardullo et al.1998).To normalize this curve,we assume that all the PN at m5007=26.9belong to the galaxy.As is illustrated,there is an excess of bright objects compared to that expected from M87alone:these are objects at the bright end of the intracluster planetary nebula population.If we statistically subtract the M87luminosity function from the Field3data, we arrive at the conclusion that at least10±2planetaries with m5007brighter than26.5are intracluster in nature,where the uncertainty is solely due to the uncertainty in the normalization value.
Note that this estimate is a bare minimum for the number of intracluster PN.For all reasonable planetary nebula luminosity functions,there are many more faint PN than bright PN. Thus,our assumption that all m5007=26.9PN are galactic is clearly wrong.However,without some model for the distribution of intracluster stars,the shape of the intracluster PNLF cannot be determined.This makes it impossible to photometrically distinguish faint intracluster PN from PN that are bound to M87.For the moment,we therefore conservatively claim that at least 10±2intracluster planetaries are present in Field3.In the future,it should be possible to re?ne this estimate with improved observations of the precise shape of the PNLF,and with the use of dynamical information obtained from PN radial velocity measurements.
A?nal feature of Figure2,and perhaps the most remarkable,deals with distance.Even
a cursory inspection of Figure2shows that the IPN of Field1are signi?cantly brighter than those of Field2.If we?t the two distributions to the PNLF of equation(2)via the technique of maximum likelihood(Ciardullo et al.1989a),then the most likely distance to the PN of Field1 is11.8±0.7Mpc,while that for Field2is14.7±1.5Mpc.The fact that Field2is more distant is not surprising,since both Yasuda,Fukugita,&Okamura(1997)and Federspiel,Tammann,
&Sandage(1997)place the galaxies of subclump B～0.4mag behind those of subclump A. What is surprising is the relatively small distance to the IPN of Field1.Most modern distance determinations,including the analysis of Cepheids in spirals by van den Bergh(1996)and the measurement of the planetary nebula luminosity function and surface brightness?uctuations in ellipticals(Jacoby,Ciardullo,&Ford1990;Tonry et al.1997),place the core of the Virgo Cluster at a distance of between14and17Mpc.No modern measurement to Virgo gives a distance smaller than～14Mpc,and11.8Mpc is certainly not a reasonable value for the distance to the cluster.
The reason for the～3Mpc discrepancy is that the PNLF law has an extremely sharp cuto?at the bright end of the luminosity function.As a result,our PN detections are severely biased
towards objects on the front edge of the cluster,and our distance estimates carry the same bias. Our derived value of11.8Mpc therefore represents the distance to the front edge of the Virgo Cluster,not the distance to the galaxies in the Virgo Cluster core.
Another way of looking at the data is to consider the brightest IPN in Fields1and3.If we assume that these bright objects are indeed part of the Virgo Cluster and have an absolute magnitude near M?,then their apparent magnitudes yield an immediate upper limit to the front edge of each?eld.The result is that the brightest IPN of Fields1and3have distances of no more than11.7Mpc,i.e.,they are～3Mpc in front of the cluster core,as de?ned by the original PNLF measurements of Jacoby,Ciardullo,&Ford(1990).The same conclusion was reached by Ciardullo et al.(1998)using the sample of PN around M87’s inner halo.This distance is signi?cantly larger than the size of the cluster projected on the sky:at a distance of～15Mpc,the classical6degree core of Virgo translates to a linear extent of only～1.5Mpc.Although it is unclear how our measurement of cluster depth quantitatively compares to the classical angular estimate of the core (Shapley&Ames1926;see the discussion in de Vaucouleurs&de Vaucouleurs1973),our data does suggest that Virgo is elongated along our line-of-sight,perhaps by as much as a factor of two.
It is worth repeating here that the planetary nebula luminosity function is extremely insensitive to the details of its parent population,and those dependences that do exist cannot explain the bright apparent magnitudes seen in the IPN population.The problem is more fully discussed in Ciardullo et al.(1998),but,in summary,there is no reasonable explanation for the existence of these bright[O III]λ5007sources other than that their location is in the foreground of the Virgo Cluster.We note that many authors have suggested that the Virgo Cluster has substantial depth(for example,see the galaxy measurements of Pierce&Tully1988;Tonry,Ajhar, &Luppino1990;Yasuda,Fukugita,&Okamura1997),but this direct measurement is still quite surprising.
4.The Stellar Population and Total Number of Intracluster Stars
Renzini&Buzzoni(1986)have shown that bolometric-luminosity speci?c stellar evolutionary ?ux of non-star-forming stellar populations should be～2×10?11stars-yr?1-L?1⊙,nearly independent of population age or initial mass function.If the lifetime of the planetary nebula stage is～25,000yr,then every stellar system should haveα～50×10?8PN-L?1⊙.Observations in elliptical galaxies and spiral bulges have shown that no galaxy has a value ofαgreater than this number,butαcan be a up to a factor of?ve smaller(Ciardullo1995).Nevertheless,the direct relation between number of planetary nebulae and parent system luminosity does provide us with a tool with which to estimate the number of stars in Virgo’s intergalactic environment.
In order for us to estimate the density of intracluster stars in Virgo,we must?rst?t the observed PNLF with a model which represents the distribution of planetary nebulae along the line-of-sight.Such a model is a necessary step in the analysis:as seen above,Virgo’s intracluster
component extends～0.5mag in front of its core,and thus our sample of PN is severely biased towards objects on the near side of the cluster.To investigate the e?ect of this bias,we considered two extreme models for the distribution of Virgo’s intracluster stars:a single component model, in which all the PN are at a common distance,and a radially symmetric model,in which the intracluster stars are distributed isotropically throughout a sphere of radius3Mpc.The symmetric model was then adjusted to deliver a“best?t”to the observed PNLF at the assumed cluster distance of15Mpc(Jacoby,Ciardullo,&Ford1990).For the single component models,we adopted the distances derived in§3.The most likely value for the underlying population’s stellar luminosity was then calculated using the method of maximum likelihood(Ciardullo et al.1989a) and an assumed value ofα2.5=20×10?9,which is an average value for elliptical galaxies(α2.5is the number of PN within2.5mag of M?per unit bolometric luminosity).Because of our limited knowledge of the luminosity function of Field3,we used single component models only for this ?eld,assuming that?eld contains10IPN within our completeness limit.In addition,because of the very large uncertainties in the above models,we also computed a single component model usingα2.5=50×10?9PN-L?1⊙;this last model represents the minimum amount of intracluster starlight necessary to be consistent with our data.The results of our models are summarized in columns1-4in Table2.
The total amount of intracluster starlight found is quite large,at least6.8×109L⊙in the768 square arcminutes we surveyed,and probably much more.As expected,the density of intracluster stars varies signi?cantly between the?elds.For Fields1and2,the choice of cluster model changes the amount of derived intracluster light dramatically.In the single component model,most of the PN can be on the near side of the cluster,where we can see objects relatively far down the luminosity function.In this scenario,the size of the IPN’s parent population is relatively small, as is the amount of intracluster light.In contrast,the symmetric model places a large number of stars on the back side of the cluster,where they contribute light,but do not populate the bright end of the PN luminosity function.The intracluster luminosity in this picture is correspondingly larger.
How likely is it that the intracluster stars are distributed symmetrically in the cluster?There is strong evidence to suggest that neither the galaxies nor the intracluster stars are in virial equilibrium.Based on the distribution and kinematics of galaxies,Binggeli,Tammann,&Sandage (1987)and Bingelli,Popescu,&Tammann(1993)concluded that the core of Virgo exhibits a signi?cant amount of substructure.Similarly,Ciardullo et al.(1998)showed that the PNLF of intracluster stars near M87is incompatible with that of a relaxed system.Although these analyses do not formally exclude all symmetric distributions,they do suggest that a symmetric distribution is unlikely.
Although our limited amount of photometric data do not allow us to address the question of Virgo’s structure directly,we can gain some insight into the state of the intracluster stars by speculating about their likely origin.To do this,we?rst focus on the metallicity of the observed IPN.Many of the planetary nebulae detected in our survey are extremely bright:some are more
than0.6mag brighter than m?at the center of the cluster.In§3,we interpreted this brightness in terms of distance,and were thus able to place the IPN～3Mpc in front of M87.This argument, however,assumes that M?,the absolute magnitude of the PNLF cuto?,is well known.For most stellar populations,this is a good assumption,as evidenced by the agreement between PNLF distances and distances determined from other methods(cf.Jacoby et al.1992;Ciardullo,Jacoby, &Tonry1993;Feldmeier,Ciardullo,&Jacoby1997).However,in extremely metal poor systems, the decreased number of oxygen atoms present in a PN’s nebula does have an a?ect.Speci?cally, PN from a population whose metallicity is one-tenth solar are expected to have a value of M?that is fainter than the nominal value by more than0.25mag(Ciardullo&Jacoby1992;Dopita, Jacoby,&Vassiliadis1992;Richer1994).This increase in M?translates directly into an error in distance.For example,if the intracluster environment of Virgo were?lled with stars with one-tenth solar abundance,our derived distance to the front of the cluster would be overestimated by～11%,and our value for the distance between the front of the cluster and the Virgo core galaxies would be underestimated by almost50%.Note,however,that we already measure a Virgo Cluster depth that is～2times that of its projected size;lowering the metallicity of the stars would only increase this ratio.It therefore seems likely that the PN detected in our survey are of moderate metallicity.
Similarly,the mere fact that we do see a large number of IPN suggests that most of the intergalactic stars are not extremely old.In their[O III]λ5007survey of Galactic globular clusters, Jacoby et al.(1997)found a factor of～4fewer PN than expected from stellar evolution theory. Jacoby et al.attribute this small number to the extreme age of the stars.Observations in the Galaxy suggest that stars with turno?masses of～0.8M⊙produce post asymptotic giant branch stars with extremely small cores,M c<0.55M⊙(Weidemann&Koester1983).Objects such as these evolve to the planetary nebula phase very slowly:so slowly,in fact,that their nebulae can di?use into space before the stars become hot enough to produce a signi?cant number of ionizing photons.If this scenario is correct,then the fact that we see large numbers of IPN indicates that the intracluster stars of Virgo cannot be as old as the globular cluster stars of the Galaxy.
If the intracluster stars of Virgo are,indeed,of moderate age and metallicity,then they must have been stripped out of their parent galaxies at a relatively recent epoch.One likely way of doing this is through“galaxy harassment”whereby high-speed encounters between galaxies rip o?long tails of matter which lead and follow the galaxy(Moore et al.1996).Although this tidal debris will eventually dissolve into the intracluster environment,it is possible that the increased energy of these stars may cause them to linger in the outer parts of the cluster for a long time. It is therefore possible that the intergalactic environment of Virgo is not a homogeneous region, but is instead clumpy,and?lled with?laments.It may be that the bright PN present in Field1 belong to one such structure that happens to be in the front side of the cluster.If this is correct, the symmetric model for Field1should be a gross overestimate of the true amount of intracluster starlight.
If we assume that the intracluster stars come from an old stellar population,similar to that
found in M87with a B?V color of1.0(de Vaucouleurs et al.1991),a bolometric correction of ?0.85(Jacoby,Ciardullo,&Ford1990),and a mean distance of15Mpc,then the luminosities implied by our PN observations can be expressed in terms of B-band surface brightnesses. Although the values are position and model dependent(cf.Table2,column5),the result is quite interesting.Our PN observations imply that the surface brightness in the Virgo Cluster core varies between B～26and B～30mag per sq.arcsec.These values are in excellent agreement with other PN-derived surface brightness values in Virgo(M′e ndez et al.1997)and Fornax(Theuns& Warren1997).They are,however,signi?cantly larger than the value of B～31.2implied from red star counts on HST frames(Ferguson,Tanvir,&von Hippel1998).One possible explanation for this discrepancy lies in the locations of the?elds:the HST?eld is50′east of M87,whereas Fields1and2are in denser regions of the cluster.If intracluster stars are concentrated towards the cores of the subclumps of Virgo,then the low number of red stars observed by HST may be attributable to the?eld’s location.Under this assumption,and using the same stellar population model used by Ferguson,Tanvir&von Hippel(1998),we would expect only～5IPN brighter than m5007=27.0in a16′×16′?eld centered on the HST position.
On the other hand,our?elds may,indeed,be typical locations in the Virgo Cluster.As described above,the high galaxy density in Field1is due,in part,to objects on the far side of the cluster which do not contribute to the observed sample of planetaries.Similarly,the shape of the PNLF of Field3suggests that much of the intracluster luminosity in that region is not associated with the physical core of Virgo,but is only present in the?eld through projection.
If our survey regions are typical of Virgo in general,then we can use our observations to estimate the total fraction of Virgo’s starlight which is between the galaxies.By?tting the surface distribution of Virgo galaxies in subclump A to a King model with core radius1?.7,Binggeli, Tammann,&Sandage(1987)derived a central luminosity density of the cluster of1×1011L⊙per square degree.If we scale this galactic luminosity density,which we denote as L galaxies(cf.Table2, column6),to the sizes and locations of Fields1and3,we can directly determine the importance of intracluster starlight.Due to its irregularity,Binggeli,Tammann,&Sandage(1987)did not?t an analytical model to subclump B.However,the luminosity density in Field2is certainly not greater than that for Field1.We therefore use Field1’s value to set a lower limit on the fraction of intracluster starlight in Field2.The results are given in column7of Table2.
Depending on the model and the?eld,the fraction of intracluster light varies from12%to 88%of the cluster’s total luminosity.To set a lower limit to the relative importance of intracluster starlight,we average the results from our three?elds,using the smallest fraction found for each ?eld.We?nd an average fraction of22%.Similarly,to?nd the upper limit to the intracluster fraction,we average the largest fractions determined.In this case,we?nd an average fraction of 61%.This range is in rough agreement with the results derived from other PN observations in Virgo(M′e ndez et al.1997)and Fornax(Theuns&Warren1997).They also agree with the direct measurement of intracluster light in Coma(Bernstein et al.1995).
We stress that these results are very uncertain,due to our lack of knowledge about the true distribution of intracluster stars,and the possible variation ofα2.5.In addition,it is also probable that we have missed a small fraction of the IPN present in our?elds due to the?nite width of our interference?lter.If the IPN velocity dispersion follows that of the galaxies,then～8%of the IPN will be Doppler shifted out of the bandpass of our44?A full-width half-maximum?lter. However,since the true kinematics of the IPN are unknown,this fraction cannot be determined precisely.Nevertheless,regardless of the particular model,a large fraction of intracluster stars are present in the Virgo Cluster.
The large amount of intracluster starlight found by this and other studies places new constraints on models of the formation and evolution of galaxy clusters.If,as we have suggested, the intracluster stars are of moderate age and metallicity,they must not have been formed in the intracluster environment,but instead have been removed from their parent galaxies during encounters.Therefore,the number and distribution of intracluster stars could be a powerful tool for discovering the history of individual galaxy clusters.Furthermore,since intracluster stars are already free of the potential wells of galaxies,they may contribute a signi?cant fraction of metals and dust to the intracluster medium.
The large amount of intracluster stars is also an unrecognized source of baryonic matter that must be taken into account in studies of galaxy clusters.Though not enough to account for all of the dark matter,intracluster stars do increase the fraction of matter that is in baryonic form.This has potentially serious consequences for cosmological models.From their calculation of the baryon fraction in the Coma Cluster,White et al.(1993)found that their derived value was too large for the universe to simultaneously have?0=1and also be in accord with calculations of cosmic nucleosynthesis.This result,sometimes called the“baryon catastrophe,”has been con?rmed in several other galaxy clusters(White&Fabian1995;Ettori,Fabian,&White1997).Although the exact amount of intracluster starlight is currently very uncertain,the presence of a large number of intracluster stars can only increase the baryon discrepancy already found.More observations will be necessary to establish how much intracluster starlight adds to the observed baryon fraction of galaxy clusters.
5.Conclusion
We report the results of a search in three?elds in the Virgo Cluster for intracluster planetary nebulae,and have detected a total of95intracluster candidates.From analysis of the numbers of the planetaries,we?nd that the amount of intracluster light in Virgo is large(at least22%of the cluster’s total luminosity),distributed non-uniformly,and varies between subclump A and B. By using the planetary nebulae luminosity function,we derive an upper limit of～12Mpc for the distance to the front edge of the Virgo Cluster and use this to show that the cluster must be elongated along our line of sight.We also use the properties of planetary nebulae to suggest that the intracluster stars of Virgo have moderate age and metallicity.The large fraction of intracluster
stars found has potentially serious consequences for models of cluster formation and evolution, and for cosmological models.Finally,we note that this survey included less than0.2%of the traditional6degree core of the Virgo Cluster.Many more intracluster planetary nebulae wait to be discovered.
We thank Allen Shafter for some additional o?-band observations and Ed Carder at NOAO, for his measurements of our on-band?lter so that we could begin our observations on time.We would also like to thank the referee,R.Corradi,for several suggestions that improved the quality of this paper.Figure1was extracted from the Digitized Sky Survey,which was produced at the Space Telescope Science Institute under https://www.doczj.com/doc/e83001011.html,ernment grant NAGW-2166.This work was supported in part by NASA grant NAGW-3159and NSF grant AST95-29270.
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Fig.1.—A2?.5by5?.7region of the Virgo Cluster,drawn from the Digitized Sky Survey.North is up,and east is to the left.Our three?elds are indicated by the large squares of side16′.Other detections of intracluster stars are also displayed including the intracluster planetary nebulae in front of M86(Arnaboldi et al.1996)and M87(Ciardullo et al.1998),intracluster red giant and asymptotic giant branch stars detected by the Hubble Space Telescope(Ferguson,Tanvir,&von Hippel1998),and the intracluster planetary nebulae detected in the4′radius circular?eld of M′e ndez et al.(1997).The position of NGC4472is shown for reference.
Fig.2.—The planetary nebula luminosity functions for the three intracluster?elds,plus a sample of suspected intracluster planetaries from M87(Ciardullo et al.1998),binned into0.2mag intervals. The solid circles represent objects in our statistical IPN samples;the open circles indicate objects fainter than the completeness limit.Note that the numbers of intracluster planetaries vary from
?eld to?eld,and that Field2appears to have a fainter cuto?than Fields1and3.
Fig. 3.—The planetary nebula luminosity functions for Field3,binned into0.2mag intervals. The solid circles represent objects in the statistical sample;the open circles indicate objects fainter than the completeness limit.The solid line shows the empirical planetary nebulae luminosity function shifted to the most likely distance modulus—it is excluded at the93%con?dence level. The dashed line is the planetary nebulae luminosity function placed at the best-?tting distance to M87(Ciardullo et al.1998),convolved with the photometric error function,and normalized to go through the point at m5007=26.9.The excess of～10planetaries at the bright end of the
luminosity function demonstrates the presence of intracluster stars.
Table1.Record of Observations
Total Exposure Mean Mean m5007completeness Fieldα(2000)δ(2000)Time(s)Transparency Seeing limit
Table2.Model Results
Implied
α2.5Luminosity L galaxies
Field Model[10?9PN-L?1⊙][×109L⊙per?eld]μB[×109L⊙per?eld]Fraction
常用整流二极管 型号VRM/Io IFSM/ VF /Ir 封装用途说明1A5 600V/1.0A 25A/1.1V/5uA[T25] D2.6X3.2d0.65 1A6 800V/1.0A 25A/1.1V/5uA[T25] D2.6X3.2d0.65 6A8 800V/6.0A 400A/1.1V/10uA[T60] D9.1X9.1d1.3 1N4002 100V/1.0A 30A/1.1V/5uA[T75] D2.7X5.2d0.9 1N4004 400V/1.0A 30A/1.1V/5uA[T75] D2.7X5.2d0.9 1N4006 800V/1.0A 30A/1.1V/5uA[T75] D2.7X5.2d0.9 1N4007 1000V/1.0A 30A/1.1V/5uA[T75] D2.7X5.2d0.9 1N5398 800V/1.5A 50A/1.4V/5uA[T70] D3.6X7.6d0.9 1N5399 1000V/1.5A 50A/1.4V/5uA[T70] D3.6X7.6d0.9 1N5402 200V/3.0A 200A/1.1V/5uA[T105] D5.6X9.5d1.3 1N5406 600V/3.0A 200A/1.1V/5uA[T105] D5.6X9.5d1.3 1N5407 800V/3.0A 200A/1.1V/5uA[T105] D5.6X9.5d1.3 1N5408 1000V/3.0A 200A/1.1V/5uA[T105] D5.6X9.5d1.3 RL153 200V/1.5A 60A/1.1V/5uA[T75] D3.6X7.6d0.9 RL155 600V/1.5A 60A/1.1V/5uA[T75] D3.6X7.6d0.9 RL156 800V/1.5A 60A/1.1V/5uA[T75] D3.6X7.6d0.9 RL203 200V/2.0A 70A/1.1V/5uA[T75] D3.6X7.6d0.9 RL205 600V/2.0A 70A/1.1V/5uA[T75] D3.6X7.6d0.9 RL206 800V/2.0A 70A/1.1V/5uA[T75] D3.6X7.6d0.9 RL207 1000V/2.0A 70A/1.1V/5uA[T75] D3.6X7.6d0.9 RM11C 1000V/1.2A 100A/0.92V/10uA D4.0X7.2d0.78 MR750 50V/6.0A 400A/1.25V/25uA D8.7x6.3d1.35 MR751 100V/6.0A 400A/1.25V/25uA D8.7x6.3d1.35 MR752 200V/6.0A 400A/1.25V/25uA D8.7x6.3d1.35 MR754 400V/6.0A 400A/1.25V/25uA D8.7x6.3d1.35 MR756 600V/6.0A 400A/1.25V/25uA D8.7x6.3d1.35 MR760 1000V/6.0A 400A/1.25V/25uA D8.7x6.3d1.35 常用整流二极管(全桥） 型号VRM/Io IFSM/ VF /Ir 封装用途说明RBV-406 600V/*4A 80A/1.10V/10uA 25X15X3.6 RBV-606 600V/*6A 150A/1.05V/10uA 30X20X3.6 RBV-1306 600V/*13A 80A/1.20V/10uA 30X20X3.6 RBV-1506 600V/*15A 200A/1.05V/50uA 30X20X3.6 RBV-2506 600V/*25A 350A/1.05V/50uA 30X20X3.6 常用肖特基整流二极管SBD 型号VRM/Io IFSM/ VF Trr1/Trr2 封装用途说明EK06 60V/0.7A 10A/0.62V 100nS D2.7X5.0d0.6 SK/高速 EK14 40V/1.5A 40A/0.55V 200nS D4.0X7.2d0.78 SK/低速 D3S6M 60V/3.0A 80A/0.58V 130p SB340 40V/3.0A 80A/0.74V 180p SB360 60V/3.0A 80A/0.74V 180p SR260 60V/2.0A 50A/0.70V 170p MBR1645 45V/16A 150A/0.65V <10nS TO220 超高速
常用二极管参数 2008-10-22 11:48 05Z6.2Y 硅稳压二极管 Vz=6~6.35V, Pzm=500mW, 05Z7.5Y 硅稳压二极管 Vz=7.34~7.70V, Pzm=500mW, 05Z13X 硅稳压二极管 Vz=12.4~13.1V, Pzm=500mW, 05Z15Y 硅稳压二极管 Vz=14.4~15.15V, Pzm=500mW, 05Z18Y 硅稳压二极管 Vz=17.55~18.45V, Pzm=500mW, 1N4001 硅整流二极管 50V, 1A,(Ir=5uA, Vf=1V, Ifs=50A) 1N4002 硅整流二极管 100V, 1A, 1N4003 硅整流二极管 200V, 1A, 1N4004 硅整流二极管 400V, 1A, 1N4005 硅整流二极管 600V, 1A, 1N4006 硅整流二极管 800V, 1A, 1N4007 硅整流二极管 1000V, 1A, 1N4148 二极管 75V, 4PF, Ir=25nA, Vf=1V, 1N5391 硅整流二极管 50V, 1.5A,(Ir=10uA, Vf=1.4V, Ifs=50A) 1N5392 硅整流二极管 100V, 1.5A, 1N5393 硅整流二极管 200V, 1.5A, 1N5394 硅整流二极管 300V, 1.5A, 1N5395 硅整流二极管 400V, 1.5A, 1N5396 硅整流二极管 500V, 1.5A, 1N5397 硅整流二极管 600V, 1.5A, 1N5398 硅整流二极管 800V, 1.5A, 1N5399 硅整流二极管 1000V, 1.5A, 1N5400 硅整流二极管 50V, 3A,(Ir=5uA, Vf=1V, Ifs=150A) 1N5401 硅整流二极管 100V, 3A, 1N5402 硅整流二极管 200V, 3A, 1N5403 硅整流二极管 300V, 3A, 1N5404 硅整流二极管 400V, 3A, 1N5405 硅整流二极管 500V, 3A, 1N5406 硅整流二极管 600V, 3A, 1N5407 硅整流二极管 800V, 3A, 1N5408 硅整流二极管 1000V, 3A, 1S1553 硅开关二极管 70V, 100mA, 300mW, 3.5PF, 300ma, 1S1554 硅开关二极管 55V, 100mA, 300mW, 3.5PF, 300ma, 1S1555 硅开关二极管 35V, 100mA, 300mW, 3.5PF, 300ma, 1S2076 硅开关二极管 35V, 150mA, 250mW, 8nS, 3PF, 450ma, Ir≤1uA, Vf≤0.8V,≤1.8PF, 1S2076A 硅开关二极管 70V, 150mA, 250mW, 8nS, 3PF, 450ma, 60V, Ir≤1uA, Vf≤0.8V,≤1.8PF, 1S2471 硅开关二极管80V, Ir≤0.5uA, Vf≤1.2V,≤2PF, 1S2471B 硅开关二极管 90V, 150mA, 250mW, 3nS, 3PF, 450ma, 1S2471V 硅开关二极管 90V, 130mA, 300mW, 4nS, 2PF, 400ma, 1S2472 硅开关二极管50V, Ir≤0.5uA, Vf≤1.2V,≤2PF, 1S2473 硅开关二极管35V, Ir≤0.5uA, Vf≤1.2V,≤3PF,
Join In剑桥小学英语(改编版)入门阶段Unit 1Hello,hello第1单元嗨,嗨 and mime. 1 听,模仿 Stand up Say 'hello' Slap hands Sit down 站起来说"嗨" 拍手坐下来 Good. Let's do up Say 'hello' Slap hands Sit down 好. 我们来再做一遍.站起来说"嗨"拍手坐下来 the pictures. 2 再听一遍给图画编号. up "hello" hands down 1 站起来 2 说"嗨" 3 拍手 4 坐下来说 3. A ,what's yourname 3 一首歌嗨,你叫什么名字 Hello. , what's yourname Hello. Hello. 嗨. 嗨. 嗨, 你叫什么名字嗨,嗨. Hello, what's yourname I'm Toby. I'm Toby. Hello,hello,hello.嗨, 你叫什么名字我叫托比. 我叫托比 . 嗨,嗨,嗨. I'm Toby. I'm Toby. Hello,hello, let's go! 我是托比. 我是托比. 嗨,嗨, 我们一起! Hello. , what's yourname I'm 'm Toby. 嗨.嗨.嗨, 你叫什么名字我叫托比.我叫托比. Hello,hello,hello. I'm 'm Toby. Hello,hello,let's go! 嗨,嗨,嗨.我是托比. 我是托比. 嗨,嗨,我们一起! 4 Listen and stick 4 听和指 What's your name I'm Bob. 你叫什么名字我叫鲍勃. What's your name I'm Rita. What's your name I'm Nick. 你叫什么名字我叫丽塔. 你叫什么名字我叫尼克. What's your name I'm Lisa. 你叫什么名字我叫利萨. 5. A story-Pit'sskateboard. 5 一个故事-彼德的滑板. Pa:Hello,Pit. Pa:好,彼德. Pi:Hello,:What's this Pi:嗨,帕特.Pa:这是什么 Pi:My new :Look!Pi:Goodbye,Pat! Pi:这是我的新滑板.Pi:看!Pi:再见,帕特! Pa:Bye-bye,Pit!Pi:Help!Help!pi:Bye-bye,skateboard! Pa:再见,彼德!Pi:救命!救命!Pi:再见,滑板! Unit 16. Let's learnand act 第1单元6 我们来边学边表演.
1.塑封整流二极管 序号型号IF VRRM VF Trr 外形 A V V μs 1 1A1-1A7 1A 50-1000V 1.1 R-1 2 1N4001-1N4007 1A 50-1000V 1.1 DO-41 3 1N5391-1N5399 1.5A 50-1000V 1.1 DO-15 4 2A01-2A07 2A 50-1000V 1.0 DO-15 5 1N5400-1N5408 3A 50-1000V 0.95 DO-201AD 6 6A05-6A10 6A 50-1000V 0.95 R-6 7 TS750-TS758 6A 50-800V 1.25 R-6 8 RL10-RL60 1A-6A 50-1000V 1.0 9 2CZ81-2CZ87 0.05A-3A 50-1000V 1.0 DO-41 10 2CP21-2CP29 0.3A 100-1000V 1.0 DO-41 11 2DZ14-2DZ15 0.5A-1A 200-1000V 1.0 DO-41 12 2DP3-2DP5 0.3A-1A 200-1000V 1.0 DO-41 13 BYW27 1A 200-1300V 1.0 DO-41 14 DR202-DR210 2A 200-1000V 1.0 DO-15 15 BY251-BY254 3A 200-800V 1.1 DO-201AD 16 BY550-200～1000 5A 200-1000V 1.1 R-5 17 PX10A02-PX10A13 10A 200-1300V 1.1 PX 18 PX12A02-PX12A13 12A 200-1300V 1.1 PX 19 PX15A02-PX15A13 15A 200-1300V 1.1 PX 20 ERA15-02～13 1A 200-1300V 1.0 R-1 21 ERB12-02～13 1A 200-1300V 1.0 DO-15 22 ERC05-02～13 1.2A 200-1300V 1.0 DO-15 23 ERC04-02～13 1.5A 200-1300V 1.0 DO-15 24 ERD03-02～13 3A 200-1300V 1.0 DO-201AD 25 EM1-EM2 1A-1.2A 200-1000V 0.97 DO-15 26 RM1Z-RM1C 1A 200-1000V 0.95 DO-15 27 RM2Z-RM2C 1.2A 200-1000V 0.95 DO-15 28 RM11Z-RM11C 1.5A 200-1000V 0.95 DO-15 29 RM3Z-RM3C 2.5A 200-1000V 0.97 DO-201AD 30 RM4Z-RM4C 3A 200-1000V 0.97 DO-201AD 2.快恢复塑封整流二极管 序号型号IF VRRM VF Trr 外形 A V V μs （1）快恢复塑封整流二极管 1 1F1-1F7 1A 50-1000V 1.3 0.15-0.5 R-1 2 FR10-FR60 1A-6A 50-1000V 1. 3 0.15-0.5 3 1N4933-1N4937 1A 50-600V 1.2 0.2 DO-41 4 1N4942-1N4948 1A 200-1000V 1.3 0.15-0. 5 DO-41 5 BA157-BA159 1A 400-1000V 1.3 0.15-0.25 DO-41 6 MR850-MR858 3A 100-800V 1.3 0.2 DO-201AD
常用稳压管型号对照——（朋友发的） 美标稳压二极管型号 1N4727 3V0 1N4728 3V3 1N4729 3V6 1N4730 3V9 1N4731 4V3 1N4732 4V7 1N4733 5V1 1N4734 5V6 1N4735 6V2 1N4736 6V8 1N4737 7V5 1N4738 8V2 1N4739 9V1 1N4740 10V 1N4741 11V 1N4742 12V 1N4743 13V 1N4744 15V 1N4745 16V 1N4746 18V 1N4747 20V 1N4748 22V 1N4749 24V 1N4750 27V 1N4751 30V 1N4752 33V 1N4753 36V 1N4754 39V 1N4755 43V 1N4756 47V 1N4757 51V 需要规格书请到以下地址下载， 经常看到很多板子上有M记的铁壳封装的稳压管，都是以美标的1N系列型号标识的，没有具体的电压值，刚才翻手册查了以下3V至51V的型号与电压的对 照值，希望对大家有用 1N4727 3V0 1N4728 3V3 1N4729 3V6 1N4730 3V9
1N4733 5V1 1N4734 5V6 1N4735 6V2 1N4736 6V8 1N4737 7V5 1N4738 8V2 1N4739 9V1 1N4740 10V 1N4741 11V 1N4742 12V 1N4743 13V 1N4744 15V 1N4745 16V 1N4746 18V 1N4747 20V 1N4748 22V 1N4749 24V 1N4750 27V 1N4751 30V 1N4752 33V 1N4753 36V 1N4754 39V 1N4755 43V 1N4756 47V 1N4757 51V DZ是稳压管的电器编号，是和1N4148和相近的，其实1N4148就是一个0.6V的稳压管，下面是稳压管上的编号对应的稳压值，有些小的稳压管也会在管体 上直接标稳压电压，如5V6就是5.6V的稳压管。 1N4728A 3.3 1N4729A 3.6 1N4730A 3.9 1N4731A 4.3 1N4732A 4.7 1N4733A 5.1 1N4734A 5.6 1N4735A 6.2 1N4736A 6.8 1N4737A 7.5 1N4738A 8.2 1N4739A 9.1 1N4740A 10 1N4741A 11 1N4742A 12 1N4743A 13
Join In剑桥小学英语(改编版)入门阶段 Unit 1Hello,hello第1单元嗨,嗨 1.Listen and mime. 1 听,模仿 Stand up Say 'hello' Slap hands Sit down 站起来说"嗨" 拍手坐下来 Good. Let's do itagain.Stand up Say 'hello' Slap hands Sit down 好. 我们来再做一遍.站起来说"嗨"拍手坐下来 2.listen again.Number the pictures. 2 再听一遍给图画编号. 1.Stand up 2.Say "hello" 3.Slap hands 4.Sit down 1 站起来 2 说"嗨" 3 拍手 4 坐下来说 3. A song.Hello,what's yourname? 3 一首歌嗨,你叫什么名字? Hello. Hello.Hello, what's yourname? Hello. Hello. 嗨. 嗨. 嗨, 你叫什么名字? 嗨,嗨. Hello, what's yourname? I'm Toby. I'm Toby. Hello,hello,hello. 嗨, 你叫什么名字? 我叫托比. 我叫托比 . 嗨,嗨,嗨. I'm Toby. I'm Toby. Hello,hello, let's go! 我是托比. 我是托比. 嗨,嗨, 我们一起! Hello. Hello.Hello, what's yourname? I'm Toby.I'm Toby. 嗨.嗨.嗨, 你叫什么名字? 我叫托比.我叫托比. Hello,hello,hello. I'm Toby.I'm Toby. Hello,hello,let's go! 嗨,嗨,嗨.我是托比. 我是托比. 嗨,嗨,我们一起! 4 Listen and stick 4 听和指 What's your name? I'm Bob. 你叫什么名字? 我叫鲍勃. What's your name ? I'm Rita. What's your name ? I'm Nick. 你叫什么名字? 我叫丽塔. 你叫什么名字? 我叫尼克. What's your name ? I'm Lisa. 你叫什么名字? 我叫利萨. 5. A story-Pit'sskateboard. 5 一个故事-彼德的滑板. Pa:Hello,Pit. Pa:好,彼德. Pi:Hello,Pat.Pa:What's this? Pi:嗨,帕特.Pa:这是什么? Pi:My new skateboard.Pi:Look!Pi:Goodbye,Pat! Pi:这是我的新滑板.Pi:看!Pi:再见,帕特! Pa:Bye-bye,Pit!Pi:Help!Help!pi:Bye-bye,skateboard! Pa:再见,彼德!Pi:救命!救命!Pi:再见,滑板! Unit 16. Let's learnand act 第1单元6 我们来边学边表演.
二极管封装大全 篇一：贴片二极管型号、参数 贴片二极管型号.参数查询 1、肖特基二极管SMA（DO214AC） 2010-2-2 16:39:35 标准封装： SMA 2010 SMB 2114 SMC 3220 SOD123 1206 SOD323 0805 SOD523 0603 IN4001的封装是1812 IN4148的封装是1206 篇二：常见贴片二极管三极管的封装 常见贴片二极管/三极管的封装 常见贴片二极管/三极管的封装 二极管： 名称尺寸及焊盘间距其他尺寸相近的封装名称 SMC SMB SMA SOD-106 SC-77A SC-76/SC-90A SC-79 三极管： LDPAK
DPAK SC-63 SOT-223 SC-73 TO-243/SC-62/UPAK/MPT3 SC-59A/SOT-346/MPAK/SMT3 SOT-323 SC-70/CMPAK/UMT3 SOT-523 SC-75A/EMT3 SOT-623 SC-89/MFPAK SOT-723 SOT-923 VMT3 篇三：常用二极管的识别及ic封装技术 常用晶体二极管的识别 晶体二极管在电路中常用“D”加数字表示，如： D5表示编号为5的二极管。 1、作用：二极管的主要特性是单向导电性，也就是在正向电压的作用下，导通电阻很小;而在反向电压作用下导通电阻极大或无穷大。正因为二极管具有上述特性，无绳电话机中常把它用在整流、隔离、稳压、极性保护、编码控制、调频调制和静噪等电路中。 电话机里使用的晶体二极管按作用可分为：整流二极管(如1N4004)、隔离二极管(如1N4148)、肖特基二极管(如BAT85)、发光二极管、稳压二极管等。 2、识别方法：二极管的识别很简单，小功率二极管的N极(负极)，在二极管外表大多采用一种色圈标出来，有些二极管也用二极管专用符号来表示P极(正极)或N极(负极)，也有采用符号标志为“P”、“N”来确定二极管极性的。发光二极管的正负极可从引脚长短来识别，长
1N 系列常用整流二极管的主要参数
反向工作 峰值电压 URM/V 额定正向 整流电流 整流电流 IF/A 正向不重 复浪涌峰 值电流 IFSM/A 正向 压降 UF/V 反向 电流 IR/uA 工作 频率 f/KHZ 外形 封装
型 号
1N4000 1N4001 1N4002 1N4003 1N4004 1N4005 1N4006 1N4007 1N5100 1N5101 1N5102 1N5103 1N5104 1N5105 1N5106 1N5107 1N5108 1N5200 1N5201 1N5202 1N5203 1N5204 1N5205 1N5206 1N5207 1N5208 1N5400 1N5401 1N5402 1N5403 1N5404 1N5405 1N5406 1N5407 1N5408
25 50 100 200 400 600 800 1000 50 100 200 300 400 500 600 800 1000 50 100 200 300 400 500 600 800 1000 50 100 200 300 400 500 600 800 1000
1
30
≤1
＜5
3
DO-41
1．5
75
≤1
＜5
3
DO-15
2
100
≤1
＜10
3
3
150
≤0.8
＜10
3
DO-27
常用二极管参数： 05Z6.2Y 硅稳压二极管 Vz=6~6.35V,Pzm=500mW,
公司登记（备案）申请书 注：请仔细阅读本申请书《填写说明》，按要求填写。 □基本信息 名称 名称预先核准文号/ 注册号/统一 社会信用代码 住所 省（市/自治区）市（地区/盟/自治州）县（自治县/旗/自治旗/市/区）乡（民族乡/镇/街道）村（路/社区）号 生产经营地 省（市/自治区）市（地区/盟/自治州）县（自治县/旗/自治旗/市/区）乡（民族乡/镇/街道）村（路/社区）号 联系电话邮政编码 □设立 法定代表人 姓名 职务□董事长□执行董事□经理注册资本万元公司类型 设立方式 （股份公司填写） □发起设立□募集设立经营范围 经营期限□年□长期申请执照副本数量个
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《剑桥小学英语Join In ——Book 3 下学期》教材教法分析2012-03-12 18:50:43| 分类：JOIN IN 教案| 标签：|字号大中小订阅. 一、学情分析： 作为毕业班的学生，六年级的孩子在英语学习上具有非常显著的特点： 1、因为教材的编排体系和课时不足，某些知识学生已遗忘，知识回生的现象很突出。 2、有的学生因受学习习惯及学习能力的制约，有些知识掌握较差，学生学习个体的差异性，学习情况参差不齐、两级分化的情况明显，对英语感兴趣的孩子很喜欢英语，不喜欢英语的孩子很难学进去了。 3、六年级的孩子已经进入青春前期，他们跟三、四、五年级的孩子相比已经有了很大的不同。他们自尊心强，好胜心强，集体荣誉感也强，有自己的评判标准和思想，对知识的学习趋于理性化，更有自主学习的欲望和探索的要求。 六年级学生在英语学习上的两极分化已经给教师的教学带来很大的挑战，在教学中教师要注意引导学生调整学习方式： 1、注重培养学生自主学习的态度 如何抓住学习课堂上的学习注意力，吸引他们的视线，保持他们高涨的学习激情，注重过程的趣味化和学习内容的简易化。 2、给予学生独立思考的空间。 3、鼓励学生坚持课前预习、课后复习的好习惯。 六年级教材中的单词、句子量比较多，难点也比较多，学生课前回家预习，不懂的地方查英汉词典或者其它资料，上课可以达到事半功倍的效果，课后复习也可以很好的消化课堂上的内容。 4、注意培养学生合作学习的习惯。 5、重在培养学生探究的能力：学习内容以问题的方式呈现、留给学生更多的发展空间。 二、教材分析： （一）.教材特点： 1．以学生为主体，全面提高学生的素质。
1N系列稳压管
快恢复整流二极管
常用整流二极管型号和参数 05Z6.2Y 硅稳压二极管 Vz=6~6.35V,Pzm=500mW, 05Z7.5Y 硅稳压二极管 Vz=7.34~7.70V,Pzm=500mW, 05Z13X硅稳压二极管 Vz=12.4~13.1V,Pzm=500mW, 05Z15Y硅稳压二极管 Vz=14.4~15.15V,Pzm=500mW, 05Z18Y硅稳压二极管 Vz=17.55~18.45V,Pzm=500mW, 1N4001硅整流二极管 50V, 1A,(Ir=5uA,Vf=1V,Ifs=50A) 1N4002硅整流二极管 100V, 1A, 1N4003硅整流二极管 200V, 1A, 1N4004硅整流二极管 400V, 1A, 1N4005硅整流二极管 600V, 1A, 1N4006硅整流二极管 800V, 1A, 1N4007硅整流二极管 1000V, 1A, 1N4148二极管 75V, 4PF,Ir=25nA,Vf=1V, 1N5391硅整流二极管 50V, 1.5A,(Ir=10uA,Vf=1.4V,Ifs=50A) 1N5392硅整流二极管 100V,1.5A, 1N5393硅整流二极管 200V,1.5A, 1N5394硅整流二极管 300V,1.5A, 1N5395硅整流二极管 400V,1.5A, 1N5396硅整流二极管 500V,1.5A, 1N5397硅整流二极管 600V,1.5A, 1N5398硅整流二极管 800V,1.5A, 1N5399硅整流二极管 1000V,1.5A, 1N5400硅整流二极管 50V, 3A,(Ir=5uA,Vf=1V,Ifs=150A) 1N5401硅整流二极管 100V,3A, 1N5402硅整流二极管 200V,3A, 1N5403硅整流二极管 300V,3A, 1N5404硅整流二极管 400V,3A,
有限合伙企业登记注册操作指南 风险控制部 20xx年x月xx日
目录 一、合伙企业的概念 (4) 二、有限合伙企业应具备的条件 (4) 三、有限合伙企业设立具备的条件 (4) 四、注册有限合伙企业程序 (5) 五、申请合伙企业登记注册应提交文件、证件 (6) （一）合伙企业设立登记应提交的文件、证件： (6) （二）合伙企业变更登记应提交的文件、证件： (7) （三）合伙企业注销登记应提交的文件、证件： (8) （四）合伙企业申请备案应提交的文件、证件： (9) （五）其他登记应提交的文件、证件： (9) 六、申请合伙企业分支机构登记注册应提交的文件、证件 (9) （一）合伙企业分支机构设立登记应提交的文件、证件 (10) （二）合伙企业分支机构变更登记应提交的文件、证件： (10) （三）合伙企业分支机构注销登记应提交的文件、证件： (11) （四）其他登记应提交的文件、证件： (12) 七、收费标准 (12) 八、办事流程图 (12) （一）有限合伙企业创办总体流程图（不含专业性前置审批） (12) （二）、工商局注册程序 (15)
（三）、工商局具体办理程序（引入网上预审核、电话预约方式） (16) 九、有限合伙企业与有限责任公司的区别 (16) （一）、设立依据 (16) （二）、出资人数 (16) （三）、出资方式 (17) （四）、注册资本 (17) （五）、组织机构 (18) （六）、出资流转 (18) （七）、对外投资 (19) （八）、税收缴纳 (20) （九）、利润分配 (20) （十）、债务承担 (21) 十、常见问题解答与指导 (21)
常用稳压二极管技术参数及老型号代换 型号最大功耗 (mW) 稳定电压(V) 电流(mA) 代换型号国产稳压管日立稳压管 HZ4B2 500 3.8 4.0 5 2CW102 2CW21 4B2 HZ4C1 500 4.0 4.2 5 2CW102 2CW21 4C1 HZ6 500 5.5 5.8 5 2CW103 2CW21A 6B1 HZ6A 500 5.2 5.7 5 2CW103 2CW21A HZ6C3 500 6 6.4 5 2CW104 2CW21B 6C3 HZ7 500 6.9 7.2 5 2CW105 2CW21C HZ7A 500 6.3 6.9 5 2CW105 2CW21C HZ7B 500 6.7 7.3 5 2CW105 2CW21C HZ9A 500 7.7 8.5 5 2CW106 2CW21D HZ9CTA 500 8.9 9.7 5 2CW107 2CW21E HZ11 500 9.5 11.9 5 2CW109 2CW21G HZ12 500 11.6 14.3 5 2CW111 2CW21H HZ12B 500 12.4 13.4 5 2CW111 2CW21H HZ12B2 500 12.6 13.1 5 2CW111 2CW21H 12B2 HZ18Y 500 16.5 18.5 5 2CW113 2CW21J HZ20-1 500 18.86 19.44 2 2CW114 2CW21K HZ27 500 27.2 28.6 2 2CW117 2CW21L 27-3 HZT33-02 400 31 33.5 5 2CW119 2CW21M RD2.0E(B) 500 1.88 2.12 20 2CW100 2CW21P 2B1 RD2.7E 400 2.5 2.93 20 2CW101 2CW21S RD3.9EL1 500 3.7 4 20 2CW102 2CW21 4B2 RD5.6EN1 500 5.2 5.5 20 2CW103 2CW21A 6A1 RD5.6EN3 500 5.6 5.9 20 2CW104 2CW21B 6B2 RD5.6EL2 500 5.5 5.7 20 2CW103 2CW21A 6B1 RD6.2E(B) 500 5.88 6.6 20 2CW104 2CW21B RD7.5E(B) 500 7.0 7.9 20 2CW105 2CW21C RD10EN3 500 9.7 10.0 20 2CW108 2CW21F 11A2 RD11E(B) 500 10.1 11.8 15 2CW109 2CW21G RD12E 500 11.74 12.35 10 2CW110 2CW21H 12A1 RD12F 1000 11.19 11.77 20 2CW109 2CW21G RD13EN1 500 12 12.7 10 2CW110 2CW21H 12A3 RD15EL2 500 13.8 14.6 15 2CW112 2CW21J 12C3 RD24E 400 22 25 10 2CW116 2CW21H 24-1
五 年 级 英 语 测 试 卷 学校 班级 姓名 听力部分（共20分） 一、Listen and colour . 听数字，涂颜色。（5分） 二、 Listen and tick . 听录音，在相应的格子里打“√”。 （6分） 三、Listen and number.听录音，标序号。（9分） pig fox lion cow snake duck
sheep 笔试部分（共80分） 一、Write the questions.将完整的句子写在下面的横线上。(10分) got it Has eyes on a farm it live sheep a it other animals eat it it Is 二、Look and choose.看看它们是谁，将字母填入括号内。(8分) A. B. C. D.
E. F. G. H. ( ) pig ( ) fox ( ) sheep ( ) cat ( ) snake ( ) lion ( ) mouse ( ) elephant 三、Look at the pictures and write the questions.看图片，根据答语写出相应的问题。(10分) No,it doesn’t. Yes,it is.
Yes,it does. Yes,it has. Yes,it does. 四、Choose the right answer.选择正确的答案。(18分) 1、it live on a farm？ 2. it fly？
3. it a cow？ 4. it eat chicken？ 5. you swim？ 6. you all right？ 五、Fill in the numbers.对话排序。(6分) Goodbye. Two apples , please. 45P , please. Thank you.
→客户提供：场所证明租赁协议身份证委托书三张一寸相片 →需准备材料：办理税务登记证时需要会计师资格证与财务人员劳动合同 →提交名称预审通知书→公司法定代表人签署的《公司设立登记申请书》→全体股东签署的《指定代表或者公共委托代理人的证明》（申请人填写股东姓名）→全体股东签署的公司章程（需得到工商局办事人员的认可）→股东身份证复印件→验资报告（需到计师事务所办理：需要材料有名称预审通知书复印件公司章程股东身份证复印件银行开具验资账户进账单原件银行开具询证函租赁合同及场所证明法人身份证原件公司开设临时存款账户的复印件）→任职文件（法人任职文件及股东董事会决议）→住所证明（房屋租赁合同）→工商局（办证大厅）提交所有材料→公司营业执照办理结束 →需带材料→公司营业执照正副本原件及复印件→法人身份证原件→代理人身份证→公章→办理人开具银行收据交款元工本费→填写申请书→组织机构代码证办
理结束 →需带材料→工商营业执照正副本复印件原件→组织机构正副本原件及复印件→公章→公司法定代表人签署的《公司设立登记申请书》→公司章程→股东注册资金情况表→验资报告书复印件→场所证明（租赁合同）→法人身份证复印件原件→会计师资格证（劳动合同）→税务登记证办理结束 →需带材料→工商营业执照正副本复印件原件→组织机构正副本原件及复印件→税务登记证原件及复印件→公章→法人身份证原件及复印件→代理人身份证原件及复印件→法人私章→公司验资账户→注以上复印件需四份→办理时间个工作日→办理结束 →需带材料→工商营业执照正副本复印件原件→组织机构正副本原件及复印件→公章→公司法定代表人签署的《公司设立登记申请书》→公司章程→股东注册资金情况表→验资报告书复印件→场所证明（租赁合同）→法人身份证复印件原件→会计师资格证（劳动合同）→会计制度→银行办理的开户许可证复印件→税务登记证备案办理结束
常用稳压管型号参数对照 3V到51V 1W稳压管型号对照表1N4727 3V0 1N4728 3V3 1N4729 3V6 1N4730 3V9 1N4731 4V3 1N4732 4V7 1N4733 5V1 1N4734 5V6 1N4735 6V2 1N4736 6V8 1N4737 7V5
1N4739 9V1 1N4740 10V 1N4741 11V 1N4742 12V 1N4743 13V 1N4744 15V 1N4745 16V 1N4746 18V 1N4747 20V 1N4748 22V 1N4749 24V 1N4750 27V 1N4751 30V
1N4753 36V 1N4754 39V 1N4755 43V 1N4756 47V 1N4757 51V 摩托罗拉IN47系列1W稳压管IN4728 3.3v IN4729 3.6v IN4730 3.9v IN4731 4.3 IN4732 4.7 IN4733 5.1
IN4735 6.2 IN4736 6.8 IN4737 7.5 IN4738 8.2 IN4739 9.1 IN4740 10 IN4741 11 IN4742 12 IN4743 13 IN4744 15 IN4745 16 IN4746 18 IN4747 20
IN4749 24 IN4750 27 IN4751 30 IN4752 33 IN4753 34 IN4754 35 IN4755 36 IN4756 47 IN4757 51 摩托罗拉IN52系列 0.5w精密稳压管IN5226 3.3v IN5227 3.6v
2011-2012 学年度上学期六年级复习题（Unit2-Unit3 ） 一、听力部分 1、听录音排序 ( ) () ()() () 2、听录音，找出与你所听到的单词属同一类的单词 （） 1. A. spaceman B. pond C . tiger （） 2. A.mascots B. potato C . jeans （） 3. A. door B. behind C . golden （） 4. A. sometimes B. shop C . prince （） 5. A. chair B. who C . sell 3、听录音，将下面人物与他的梦连线 Sarah Tim Juliet Jenny Peter 4、听短文，请在属于Mr. Brown的物品下面打√ ( ) ( ) ( ) ( ) ( ) ( ) ( ) 5、听问句选答句 （） 1. A. Yes, I am B. Yes, I have C . Yes, you do （） 2. A.Pink B. A friendship band C . Yes. （） 3. A. OK B. Bye-bye. C . Thanks, too. （） 4. A. Monday. B. Some juice. C . Kitty. （） 5. A. I ’ve got a shookbag. B. I ’m a student. C . It has got a round face. 6、听短文，选择正确答案 （） 1. Where is Xiaoqing from? She is from . A.Hebei B. Hubei C . Hunan （） 2. She goes to school at . A.7:00 B.7:30 C . 7:15 （） 3. How many classes in the afternoon? classes. A. four B. three C . two （） 4. Where is Xiaoqing at twelve o ’clock? She is . A. at home B. at school C .in the park （） 5. What does she do from seven to half past eight? She . A.watches TV B. reads the book C. does homework
G ENERAL PURPOSE RECTIFIERS – P LASTIC P ASSIVATED J UNCTION 1.0 M1 M2 M3 M4 M5 M6 M7 SMA/DO-214AC G ENERAL PURPOSE RECTIFIERS – G LASS P ASSIVATED J UNCTION S M 1.0 GS1A GS1B GS1D GS1G GS1J GS1K GS1M SMA/DO-214AC 1.0 S1A S1B S1D S1G S1J S1K S1M SMB/DO-214AA 2.0 S2A S2B S2D S2G S2J S2K S2M SMB/DO-214AA 3.0 S3A S3B S3D S3G S3J S3K S3M SMC/DO-214AB F AST RECOVERY RECTIFIERS – P LASTIC P ASSIVATED J UNCTION MERITEK ELECTRONICS CORPORATION
U LTRA FAST RECOVERY RECTIFIERS – G LASS P ASSIVATED J UNCTION
S CHOTTKY B ARRIER R ECTIFIERS
S WITCHING D IODES Power Dissipation Max Avg Rectified Current Peak Reverse Voltage Continuous Reverse Current Forward Voltage Reverse Recovery Time Package Part Number P a (mW) I o (mA) V RRM (V) I R @ V R (V) V F @ I F (mA) t rr (ns) Bulk Reel Outline 200mW 1N4148WS 200 150 100 2500 @ 75 1.0 @ 50 4 5000 SOD-323 1N4448WS 200 150 100 2500 @ 7 5 0.72/1.0 @ 5.0/100 4 5000 SOD-323 BAV16WS 200 250 100 1000 @ 7 5 0.8 6 @ 10 6 5000 SOD-323 BAV19WS 200 250 120 100 @ 100 1.0 @ 100 50 5000 SOD-323 BAV20WS 200 250 200 100 @ 150 1.0 @ 100 50 5000 SOD-323 BAV21WS 200 250 250 100 @ 200 1.0 @ 100 50 5000 SOD-323 MMBD4148W 200 150 100 2500 @ 75 1.0 @ 50 4 3000 SOT-323-1 MMBD4448W 200 150 100 2500 @ 7 5 0.72/1.0 @ 5.0/100 4 3000 SOT-323-1 BAS16W 200 250 100 1000 @ 7 5 0.8 6 @ 10 6 3000 SOT-323-1 BAS19W 200 250 120 100 @ 100 1.0 @ 100 50 3000 SOT-323-1 BAS20W 200 250 200 100 @ 150 1.0 @ 100 50 3000 SOT-323-1 BAS21W 200 250 250 100 @ 200 1.0 @ 100 50 3000 SOT-323-1 BAW56W 200 150 100 2500 @ 75 1.0 @ 50 4 3000 SOT-323-2 BAV70W 200 150 100 2500 @ 75 1.0 @ 50 4 3000 SOT-323-3 BAV99W 200 150 100 2500 @ 75 1.0 @ 50 4 3000 SOT-323-4 BAL99W 200 150 100 2500 @ 75 1.0 @ 50 4 3000 SOT-323- 5 350mW MMBD4148 350 200 100 5000 @ 75 1.0 @ 10 4 3000 SOT-23-1 MMBD4448 350 200 100 5000 @ 75 1.0 @ 10 4 3000 SOT-23-1 BAS16 350 200 100 1000 @ 75 1.0 @ 50 6 3000 SOT-23-1 BAS19 350 200 120 100 @ 120 1.0 @ 100 50 3000 SOT-23-1 BAS20 350 200 200 100 @ 150 1.0 @ 100 50 3000 SOT-23-1 BAS21 350 200 250 100 @ 200 1.0 @ 100 50 3000 SOT-23-1 BAW56 350 200 100 2500 @ 70 1.0 @ 50 4 3000 SOT-23-2 BAV70 350 200 100 5000 @ 70 1.0 @ 50 4 3000 SOT-23-3 BAV99 350 200 100 2500 @ 70 1.0 @ 50 4 3000 SOT-23-4 BAL99 350 200 100 2500 @ 70 1.0 @ 50 4 3000 SOT-23-5 BAV16W 350 200 100 1000 @ 75 0.86 @ 10 6 3000 SOD-123 410-500mW BAV19W 410 200 120 100 @ 100 1.0 @ 100 50 3000 SOD-123 BAV20W 410 200 200 100 @ 150 1.0 @ 100 50 3000 SOD-123 BAV21W 410 200 250 100 @ 200 1.0 @ 100 50 3000 SOD-123 1N4148W 410 150 100 2500 @ 75 1.0 @ 50 4 3000 SOD-123 1N4150W 410 200 50 100 @ 50 0.72/1.0 @ 5.0/100 4 3000 SOD-123 1N4448W 500 150 100 2500 @ 7 5 1.0 @ 200 4 3000 SOD-123 1N4151W 500 150 75 50 @ 50 1.0 @ 10 2 3000 SOD-123 1N914 500 200 100 25 @ 20 1.0 @ 10 4 1000 10000 DO-35 1N4148 500 200 100 25 @ 20 1.0 @ 10 4 1000 10000 DO-35 LL4148 500 150 100 25 @ 20 1.0 @ 10 4 2500 Mini-Melf SOT23-1 SOT23-2 SOT23-3 SOT23-4 SOT23-5 SOT323-1 SOT323-2 SOT323-3 SOT323-4 SOT323-5