a r X i v :a s t r o -p h /0107269v 1 16 J u l 2001
Astronomy &Astrophysics manuscript no.(will be inserted by hand later)
Carbon Monoxide in type II supernovae ?
J.Spyromilio,B.Leibundgut and R.Gilmozzi
European Southern Observatory,Karl-Schwarzschild-Strasse 2,Garching,D-85748,Germany e-mail:jspyromi@https://www.doczj.com/doc/738862614.html,,bleibundgut@https://www.doczj.com/doc/738862614.html,,rgilmozz@https://www.doczj.com/doc/738862614.html, Received ;accepted
Abstract.Infrared spectra of two type II supernovae 6months after explosion are presented.The spectra exhibit a strong similarity to the observations of SN 1987A and other type II SNe at comparable epochs.The continuum can be ?tted with a cool black body and the hydrogen lines have emissivities that are approximately those of a Case B recombination spectrum.The data extend far enough into the thermal region to detect emission by the ?rst overtone of carbon monoxide.The molecular emission is modeled and compared with that in the spectra of SN 1987A.It is found that the ?ux in the CO ?rst overtone is comparable to that found in SN 1987A.We argue that Carbon Monoxide forms in the ejecta of all type II SNe during the ?rst year after explosion.Key words.molecular processes -Supernovae:individual:SN 1998dl ;SN 1999em
1.Introduction
The presence of molecular emission in the spectra of super-novae while not new remains rarely detected.First detec-tion of carbon monoxide in a supernova was in the spec-tra of SN 1987A (Catchpole &Glass 1987,McGregor &Hyland 1987,Ames Research Center 1987,Oliva et al.1987,Spyromilio et al.1988).In SN 1987A observations of the ?rst overtone of CO at 2.3-μm were complemented by observations at 4.6-μm of the fundamental bands.In addition to carbon monoxide,the spectra of SN 1987A re-vealed bands of SiO (Meikle et al.1993;Roche et al.1991)and CS (Meikle et al.1993).The presence of H +3is also claimed in the spectra of SN 1987A (Miller et al.1992)although alternative atomic species can also explain the identi?ed features.Spyromilio &Leibundgut (1996)re-ported the detection of CO ?rst overtone emission in the spectra of the type II supernova 1995ad while Gerardy et al.(2000)and Fassia et al.(2000)reported the presence of CO in SN 1998S.
The formation of molecules in the ejecta of supernovae,even CO -the most stable of diatomic molecules with a dissociation energy of 11.09eV (Douglas &M?ller 1955),is not trivial.The high UV ?eld due to recombinations and the energetic electrons from the radioactive decays of 56
Ni and its daughter 56Co create an inhospitable environ-ment with multiple dissociation paths (see Lepp,Dalgarno &McCray 1990).The presence therefore of molecules
in
2J.Spyromilio,B.Leibundgut and R.Gilmozzi:CO in type II SNe
lines in early optical spectra classifying the object as a type II supernova.
SN1998dl was observed at the ESO 3.58-m New Technology Telescope on La Silla,on1999January1,at an age of approximately150days.The near-infrared cam-era and spectrograph SofI(Moorwood et al.1999)was used for these observations.The red low-resolution grism was used for the H and K band spectra.While the grism does cover the region between1.8and1.92μm the atmo-spheric transparency is very low and no useful data are available in this region.A1arcsecond slit was used which gives a resolution ofλ/?λof650and a wavelength cov-erage from1.5μm to2.5-μm.The spectroscopic standard BS2290(Allen&Cragg1983)was used to remove atmo-spheric features and to correct for the spectral response of the instrument.The conditions were not photometric and therefore the absolute?uxing of the spectrum is arbitrary. The slit projects to3pixels on the detector oversampling the data.Narrow features,of order3pixels(e.g.the par-ticularly prominent feature at2μm),in the spectra are not real but result from incomplete corrections for atmo-spheric features.
Supernova1999em in NGC1637(recession velocity 717kms?1)was discovered by Li(1999)from observations made,on1999October29,at the KAIT.Jha et al.(1999) and Deng et al.(1999)classi?ed the object as a type II supernova based on spectroscopic observations.
SN1999em was observed,on2000April24,at an age of approximately170days with the same instrumental con-?guration as1998dl.The spectroscopic standard used in this case was HIP27855(Perryman et al.1997).The ac-curate removal of atmospheric features requires that the standard and the target are observed using the same re-solving power.The usage of a narrow slit in both observa-tions of the standard and the target implies that a sepa-rate photometric calibration of the data needs to be made to recover absolute?uxes.The imaging mode of SofI was used for this purpose and the NICMOS standard S121-E (Persson et al.1998)was used for the calibration.The de-rived K s magnitude of the supernova was15.1.The mean ?ux of the observed spectrum was corrected to the this magnitude.
3.Discussion
The spectra of SN1998dl and SN1999em are displayed in Figs.1and2,respectively.The data are shown at their observed wavelengths without correction for the recession velocity of the parent galaxies.The spectra are character-ized by a strong continuum upon which emission lines are superimposed.The strong Brackettγline(rest wavelength 2.1655μm)is evident.In the SN1999em data the shorter wavelength transitions of the Brackett series can also be seen.Long-wards of the Brγline,at2.21μm,a broad fea-ture identi?ed by Meikle et al.(1989)in the spectra of SN1987A as emission by the2.207μm Na I4s2S–4p2P o multiplet is evident1.Starting at2.3μm and extending to the end of our spectral converage a broad feature is evi-dent in the data.This broad feature we attribute to carbon monoxide?rst overtone transitions(?v=2).The much weaker second overtone(?v=3)is expected to start at 1.5μm.Its contribution is expected to be only1.4%of the strength of the?rst overtone(Bouanich&Brodbeck 1974)and is therefore not detectable in our spectra.In much higher signal to noise data as would possibly be ob-tained at the VLT with ISAAC it might be possible to detect such emission.The fundamental(?v=1)band at4.6μm is very much stronger than the?rst overtone observed here but also in an extremely unfavourable at-mospheric window.This fundamental band,as mentioned in the introduction,almost dominates the cooling of the ejecta for some time and observation would be of great in-terest.Unfortunately they are probably limited to a com-bination of the very biggest telescopes and the very nearest supernovae.
A strong emission feature is observed at2μm.As noted above the narrow spike superimposed on the broad emis-sion is instrumental.In SN1987A,a broad feature at the same wavelength was identi?ed by Meikle et al.as emission by the Ca I4p3P o–3d3D multiplet and the[Fe I]a5F5–a3F4 multiplet.Assuming a contribution to the2μm by[Fe I] in the spectrum of SN1998dl,the strong line at1.51μm could be identi?ed as emission by the[Fe I]a5D?2–a5F4 multiplet.Alternatively Mg I also has a strong transition at1.5031μm.The lower recession velocity of the parent galaxy of SN1999em prevents us from detecting the same line in that spectrum.
At2.06μm both in SN1998dl and SN1999em a small absorption is present.This we identify as the P-Cygni trough of the He I2s1S–2p1P o 2.058μm transition.We note that this region is one of poor atmospheric transmis-sion with a strong telluric CO2feature at2.06μm.While we believe that we have correctly compensated for this it is possible that the feature we identify as due to He I is due to poor cancellation by of aforementioned atmospheric feature.He I is expected to be very weak but its presence would be signi?cant as highly excited He is a tracer for the presence of energetic electrons from the radioactive decay(Graham1988;Fassia&Meikle1999).The singlet transition observed here would need to develop su?cient optical depth to exhibit a P-Cygni trough.While transi-tions from2s1S to the ground state of He I are forbidden, depopulation of this energy level can occur via two photon decay with a low transition probability(A=51s?1).Given the age of the supernovae at the time of observation even this process would have de-populated the ground state of the2.058μm line.Recombinations are the obvious source of electrons which,as the transitions from the1P o states to the ground are expected to be saturated,will naturally cascade down to the2s1S level.Given the high ionization potential of He(24.587eV)the presence of the2.058μm
J.Spyromilio,B.Leibundgut and R.Gilmozzi:CO in type II SNe
3 Fig.1.Spectrum of
1998dl.
Fig.2.Spectrum of1999em.
transition suggests that the excitation by energetic elec-
trons argued by Graham and Fassia&Meikle is occuring
also in these two SNe.
We have used simple line models to make
?ts to the
data.These?ts are shown in Figs.3and4.The ingredients
of the models are described below.
The continuum in the models is a black-body with
a temperature of3300K for SN1998dl and2000K
for SN1999em.The?ux observed in the spectrum of
SN1999em at this temperature corresponds to a surface
of last scattering expanding at500kms?1for170days at
a distance of7.8Mpc(Sohn&Davidge1998).
For the carbon monoxide a simple LTE(Boltzmann
distribution)model of the populations of the rotational-
vibrational energy levels in the ground state electronic
level1Σof12C16O(CO)was used.This model has been
described before in Spyromilio et al.(1988).Brie?y,the
energy levels for a given rotational level J and a given
vibrational level v can be determined using:
E=ω(v+1
2
)2+ωy(v+1
3hg J
(T M)2(2)
whereνis the transition frequency,g J=2J+1and
TM is the transition matrix from vibrational level v to v′.
TM for?J of±1is given by Chackerian&Tipping(1983)
The lowest15vibrational levels were included and within
each110rotational level populations were calculated.
As has been shown in the spectra of SN1987A
(Spyromilio et al.1988)the CO band heads are sensitive to
the excitation temperature.Higher temperature in the CO
model increase the contribution of higher vibrational pairs
and increase the emission long-wards of the v=2to v′=0
band-head.The quality of the data is not good enough
to reliably distinguish between small changes in the tem-
perature.The SN1998dl data indicate a slightly higher
temperature than the SN1999em.The?ts use2500K for
SN1998dl and2000K for SN1999em.The uncertainty in
these values is of order a few hundred degrees K.The dif-
ference in the temperatures leads to a signi?cantly di?er-
ent appearance of the?rst overtone emission.The2000K
temperature for the SN1999em spectrum is based on the
assumption that the drop in?ux long-wards of2.35μm
is real.The SN1998dl spectra appear to show a much
smoother decline towards longer wavelengths.
The velocity at which the CO is expanding can be used
to constrain the mass of the progenitor(Gerardy et al.
2000).In SN1998S Gerardy et al.derive a high expansion
velocity(v≈3000kms?1)based on the smooth rise of the
2-0R-branch band head and a progenitor mass in excess of
25M⊙.Fassia et al.(2000)do not detect such a steep rise
and argue for a lower velocity.In addition their modeling
of the ejecta favours a lower mass progenitor.We argue
below in favour of the low range of velocities although we,
like Gerardy et al.,have a smooth rise of the2-0R-branch
band head.
In the spectra of SN1987A a rigorous?tting of the ex-
pansion velocity could be made(Spyromilio et al.1988)
based on the appearance of the R-branch emission from
each pair of energy states.Both Gerardy et al.(2000)and
Fassia et al.(2000)use the lack of clear separation of the
R-branch band heads to place lower limits on the expan-
sion velocity in the observations of SN1998S.This same
e?ect can be used by us to place a weak lower limit of
1000kms?1on the expansion velocity.
The comparison of SN1998S with SN1987A(see
Gerardy et al.Fig.6)shows that another line is possi-
bly blended with the CO band head at2.28μm.This fea-
ture,which at the recession velocity of SN1987A is ob-
served at2.26μm,is discussed later but remains uniden-
ti?ed.The2.26μm feature is very strong in the spectra of
4J.Spyromilio,B.Leibundgut and R.Gilmozzi:CO in type II SNe
SN 1999em and weakly present in our data on SN 1998dl.The same feature was
present in the spectra of SN 1995ad (Spyromilio &Leibundgut 1996).We cannot account for the lack of detection of this in the data of Fassia et al.(2000).The blending of this feature into the band head implies that models that do not take this into account will underestimate the true sharpness of the band head rise and derive higher than expected expansion velocities.The best estimate of the velocity of the CO,we believe,comes from the comparison of the observed spectra with those of SN 1987A (see Figs.5and 6).The good matching of the rise of the 2-0band head suggests that the veloc-ity observed in SN 1987A (1800–2000kms ?1;Spyromilio et al.1988)is representative of the velocity of the CO in SN 1998dl and SN 1999em.Clearly in the absence of the blended line we would agree with Gerardy et al.(2000)and also derive a much higher expansion velocity for the CO.Each CO line in our models was convolved with a Gaussian line pro?le of FWHM 2000kms ?1.
The Brackett series line strengths in the model as-sume a case-B recombination spectrum at a temperature of 3000K and electron density of 105(Hummer &Storey 1987).The Br γand 9→4transitions are well ?t using these parameters.The Br δline lies at the very edge of the atmospheric window and the cancellation of the at-mospheric features there is poor.While the norm would be not to display the spectra in this region due to the large uncertainties in the data we include them here.The data show that the spectra are consistent with the model.We do not derive any further information from the region around 1.92mu m.Unfortunately the Br ?transition lies in the gap between the two atmospheric windows and is not observable from the ground.The FWHM of the Gaussian line pro?le computed was 3000kms ?1.As has been the case in the other SNe in which CO was detected,the ve-locity of the hydrogen lines is higher than that of the CO.The individual lines identi?ed earlier as Na I ,Ca I and [Fe I ]have not been included in the displayed ?ts as the individual contributions of the species would be arbitrary.As already discussed with respect to the expansion ve-locity,the observations presented here can be compared with the observations of SN 1987A (data from Meikle et al.1989).Fig.5shows the data from SN 1987A taken at an age of 192days superimposed on the spectra of SN 1998dl.The SN 1987A data have been scaled to match the ?ux in the CO feature and red-shifted to the recession velocity of NGC1084.The continuum underlying the SN 1987A data has been arti?cially adjusted to match the average con-tinuum level in the SN 1998dl data.The SN 1998dl con-tinuum is much bluer than that of SN 1987A at the epoch at which the comparison data are taken.The poor correla-tion at 2.25μm is partially due to this e?ect and partially due to the di?erence in the strength of the 2.26μm feature.Given the quality of the SN 1998dl data,this comparison,adds plausibility to the identi?cation of CO in the spec-tra.Also as mentioned above it allows a more accurate determination of the velocity structure of CO than can be achieved from the models.A similar comparison is made
Fig.3.Spectrum of 1998dl and model.Features discussed in the text are identi?ed in the ?gure.
Fig.4.Spectrum of 1999em and model.Features dis-cussed in the text are identi?ed in the ?gure.
in Fig.6for SN 1999em using SN 1987A data obtained at an age of 255days.
The ?ux within the CO emission band for SN 1999em is 5.5×10?11ergs/s/cm 2which at the distance of NGC 1637(7.8Mpc;Sohn &Davidge 1998)is 20%lower than that of SN 1987A at a comparable epoch.
The mass that corresponds to this emission depends critically on the emission model.Our LTE model gives masses of order 10?4M ⊙.Liu &Dalgarno 1995predict a much higher mass (～10?3M ⊙)for the same emission at this age and argue that the conditions within the ejecta favour the formation of this amount of CO.In fact it is expected that signi?cantly more CO formed during the youth of the supernova (≈100days after explosion)but has been destroyed.Gearhart,Wheeler &Swartz 1999favour the formation of much less CO than Liu &Dalgarno and more in line with our mass estimates.Both Gerardy
J.Spyromilio,B.Leibundgut and R.Gilmozzi:CO in type II SNe
5
Fig.5.Spectrum of 1998dl in the K band with spectrum of SN1987A
superimposed.
Fig.6.Spectrum of 1999em in the K band with spectrum of SN1987A superimposed.Note that the feature marked as CO +is much weaker in 87A than in 99em.
et al.(2000)and Fassia et al.(2000)employ non-LTE and optically thick models to estimate the mass of CO emitting and derive high masses.These models base their input on assumptions and parameters that cannot be derived from our limited observations and even in the case of SN 1998S are based on assumed ?lling factors.Moreover Gerardy et al.argue that their comparisons are more a proof of prin-ciple rather than true models.We restrict ourselves there-fore to our comparison with SN https://www.doczj.com/doc/738862614.html,plications due to clumping and asphericity are beyond the scope of this work to address but it is worth noting that polarization has been detected in the spectra of SN 1999em (Leonard,Filippenko &Chornock 1999;Wang et al.1999).
Sollerman et al.(2001)detected no sign of dust in spec-troscopic observations of SN 1999em obtained at an age of 450days.While the formation of molecules may provide
the cold sites for dust formation in the ejecta of type II su-pernovae and therefore may be a necessary precondition,it is clearly not su?cient.
The feature at 2.26-μm short-wards of the CO v =2→0band head remains unidenti?ed.The formation of su?-cient CO +,whose ?rst overtone v =2→0band head co-incides with this feature,is excluded by both Gearhart et al.and Liu &Dalgarno.Note,however,that Petuchowski et al.1989have argued that CO +could form in su?-cient quantities.The feature was reported by and iden-ti?ed as CO +by Spyromilio et al.(1988)and reported by Spyromilio &Leibundgut in the spectra of SN 1995ad.It is also observed by Gerardy et al.(2000)in SN 1998S.Fassia et al.(2000)did not detect the emission in their spectra of SN 1998S.While theoretical models fail to pre-dict the necessary amounts of CO +the identi?cation of this feature remains insecure.
4.Conclusions
The spectra presented in this paper combined with the ob-servations presented by Spyromilio &Leibundgut (1996),Gerardy et al.(2000)and Fassia et al.(2000)suggest that the formation of CO in the ejecta of type II supernovae is ubiquitous at an age of 3to 6months.
The mass of CO present in the ejecta is di?cult to es-timate accurately.Our LTE models while simplistic rely on few assumptions with respect to the distribution and excitation of the CO.While for well studied supernovae such as SN 1987A the much more detailed models of Lepp,Dalgarno and McCray (1990)are well justi?ed,it is ar-guable whether the input parameters for such models are well enough constrained in the case of the objects de-scribed here.We therefore argue that since the absolute ?uxes argee for SN 1987A and SN 1999em so,to ?rst ap-proximation,will the emitting masses.
The expansion velocity of the CO is not accurately determined.By comparison with SN 1987A we argue that velocities around 2000kms ?1are consistent with our data.We also argue that the blending of the ubiquitous (in our data)feature at 2.26μm with the 2-0R branch band head has to be taken into account when using this pro?le for velocity determinations.
We note that comparing the spectra of the four other supernovae with CO emission with those of SN 1987A it is consistently the case that the spectral signature of the emission resembles that of SN 1987A at a later age than that at which the other SNe are observed.
The other aspects of our data indicate that the spectra of type II SNe in the near IR are very similar and that recombination continues to play a major role even 5to 6months after explosion.
A better understanding of the physical conditions in the ejecta of supernovae can be achieved with higher qual-ity infrared data as would be obtained with ISAAC at the VLT.Very high quality data may even constrain the iso-topic ratios of carbon and oxygen as the wavelengths of the band heads to shift depending on the exact isotopes.
6J.Spyromilio,B.Leibundgut and R.Gilmozzi:CO in type II SNe Acknowledgements.We thank the sta?at the NTT for their
excellent support over many years of observing.We thank
David Silva for outNEDing NED.This research has made use of
the NASA/IPAC Extragalactic Database(NED)which is op-
erated by the Jet Propulsion Laboratory,California Institute
of Technology,under contract with the National Aeronautics
and Space Administration.
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数据管理系统企业级数据可视化项目Html5 应用实践 项目经理：李雪莉 组员：申欣邹丽丹陈广宇陈思 班级：大数据&数字新媒体 一、项目背景 随着大数据、云计算和移动互联网技术的不断发展，企业用户对数据可视化的需求日益迫切。用户希望能够随时随地简单直观的了解企业生产经营、绩效考核、关键业务、分支机构的运行情况，即时掌握突发性事件的详细信息，快速反应并作出决策。随着企业信息化的不断推进，企业不断的积累基础信息、生产运行、经营管理、绩效考核、经营分析等以不同形式分布在多个系统或个人电脑文档内的业务数据。如何将大量的数据进行分析整理，以简单、直观、高效的形式提供给管理者作为经营决策的依据是当前企业数据应用的迫切需求。传统的企业数据可视化方案多基于Java Applet、Flash、Silverlight 等浏览器插件技术进行开发，在当前互联网和移动互联网技术高速发展的背景下，Web技术标准也随之高速发展，用户对互联网技术安全性和使用体验的要求越来越高。Java Applet、Flash、Silverlight 等浏览器插件技术因为落后和封闭的技术架构，以及高功耗、高系统资源占用，已经被微软、谷歌、苹果、火狐等主流操作系统和浏览器厂商逐步放弃，转而不断支持和完善基于HTML5的新一代Web技术标
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图书管理系统数据流程图 2009-04-14 17:20 1.1 系统分析 1.1.1 图书馆管理信息系统的基本任务 该“图书馆管理信息系统”是一个具有万人以上的员工，并地理位置分布在大型企的图 书馆理系统，图书馆藏书 100 多万册，每天的借阅量近万册。在手工操作方式下，图书的编目和借阅等的工作量大，准确性低且不易修改维护，读者借书只能到图书馆手工方式查找书目，不能满足借阅需求。需要建立一套网络化的电子图书馆信息系统。 该图书馆管理信息系统服务对象有两部分人：注册用户和一般读者。一般读者经注册后成为注册用户，注册用户可以在图书馆借阅图书，其他人员只可查阅图书目录，但不能借阅图书。系统同时考虑提供电子读物服务，目前只提供电子读物的目录查询服务，不久的将来将提供电子读物全文服务。用户可通过网络方式访问读图书馆管理信息系统。 1.1.2 系统内部人员结构、组织及用户情况分析 为了对系统有一个全貌性的了解，首先要对系统内部人员结构、组织及用户情况有所了 解。图书馆系统的组织结构如图 1 － 1 所示。 图 1 － 1 图书馆管理信息系统的组织结构 图书馆由馆长负责全面工作，下设办公室、财务室、采编室、学术论文室、图书借阅室、电子阅览室、期刊阅览室和技术支持室。各部门的业务职责如下。
办公室：办公室协助馆长负责日常工作，了解客户需求，制定采购计划。 财务室：财务室负责财务方面的工作。 采编室：采编室负责图书的采购，入库和图书编目，编目后的图书粘贴标签，并送图书借阅室上架。 学术论文室：负责学术论文的收集整理。 图书借阅室：提供对读者的书目查询服务和图书借阅服务。 电子阅览室：收集整理电子读物，准备提供电子读物的借阅服务，目前可以提供目录查询和借阅。 期刊阅览室：负责情况的收集整理和借阅。 技术支持室：负责对图书馆的网络和计算机系统提供技术支持。 1.1.3 系统业务流程分析 系统的业务室系统要达到的业务目标，业务流程分析是系统分析的基础环节。图书馆管 理信息系统的业务流程如图 1 － 2 所示。
软件产品开发需求模型(DFD 和DD) 数据字典是关于数据的信息的集合，对数据流程图中的各个元素做完整的定义与说明，是 数据流程图的补充工具。数据流图和数据字典共同构成系统的逻辑模型。 数据字典由下列六类元素的定义组成： （1）数据流 （2）数据项：是“不可再分”的数据单位，是数据的最小组成单位。 （3）数据结构 （4）数据存储：数据存储是数据结构停留或保存的场所。 （5）处理逻辑 （6）外部实体 在第一层和第二层数据流图的定义之后，我们都已经详细定义了数据字典的各元素。 对于各数据项的详细符号描述，见实验二的《软件概要设计说明》中的“软件数据结构设计”。 一、 数据流图： 1． 网上购书电子商务系统数据流程图（第一层） DBMS1.1暂存订单 DBMS1.2书籍库存 DBMS1.3采购订单 DBMS1.4销售历史DBMS1.6应付款明细帐DBMS1.5应收款明细帐DBMS1.7总帐
数据流图说明：（DD） 1．1 E：外部项 1．2 P：处理逻辑 1．3 F：数据流 共有FBMS1.1～FBMS1.10这10个数据流，分别描述如下：（1）数据流名称：FBMS1.1 数据流说明：用户登入 （2）数据流名称：FBMS1.2 数据流说明：密码修改 （3）数据流名称：FBMS1.3 数据流说明：顾客的订单
（4）数据流名称：FBMS1.4 （5）数据流名称：FBMS1.5 （6）数据流名称：FBMS1.6 数据流说明：送货人给顾客的收据（发货票） （7）数据流名称：FBMS1.7
（8）数据流名称：FBMS1.8 （9）数据流名称：FBMS1.9 （10）数据流名称：FBMS1.10 1．4 D：数据存储 描述如下： （1）数据存储代号：DBMS1.1 数据存储名称：暂存订单
信息技术（选修4） 数据管理技术复习提纲 概要： 信息技术学科模块4——《数据管理技术》，全书以应用数据管理技术解决问题为主线，按照“分析问题——设计数据库——建立数据库——使用数据库——管理数据库”这一线索呈现学习容。全书分五章，下面介绍第一章至第五章的主要容： 第一章 认识数据管理技术 一、数据管理基本知识 1、数据管理技术的基本概念 数据：是人类社会的一种重要信息资源，是对现实世界中客观事物的符号。计算机中的数 据分为数值型数据与非数值型数据。 例题：如商品价格、销售数量等数据是（ ） A 、数值数据 B 、非数值数据 说明：数据是信息的符号表示或称为载体。即为了表达信息（抽象概念），必须使用某种符号，这些符号就叫数据，如字符、图表、图形、图像、声音、视频等都可以称为数据。信息依赖数据来表达，是数据的涵，是对数据语义的解释。 数据管理：是指对数据的收集、分类、组织、编码、存储、查询和维护等活动。 数据管理技术：指与数据管理活动有关的技术。 数据库（DB ）：是指按照某种模型组织起来的，可以被用户或应用程序共享的数据的集合。 数据库系统（DBS ）：是指采用的数据库技术的完整的计算机系统。 数据库管理系统（DBMS ）：是能够建立数据库、维护数据库及管理数据库的一个开发平台。 数据库应用系统：是应用了数据库的信息系统。 说明：数据库系统的核心为数据库管理系统，数据库管理系统的核心为数据库（或数据） 例题：下列软件中，不属于数据库应用系统的是（ ） A 、学籍管理系统 B 、中考成绩查询系统 C 、Linux 操作系统 D 、网络售票系统 例题：数据库管理系统英文简写是（ ） A 、D B B 、DBS C 、DBMS D 、Access 系统软件 应用软件 数据库系统结构示意图