X-ray properties of NGC 300 I. Global properties of X-ray point sources and their optical c
多尺度特征融合的脊柱X线图像分割方法
脊柱侧凸是一种脊柱三维结构的畸形疾病，全球有1%~4%的青少年受到此疾病的影响[1]。
该疾病的诊断主要参考患者的脊柱侧凸角度，目前X线成像方式是诊断脊柱侧凸的首选，在X线图像中分割脊柱是后续测量、配准以及三维重建的基础。
近期出现了不少脊柱X线图像分割方法。
Anitha等人[2-3]提出了使用自定义的滤波器自动提取椎体终板以及自动获取轮廓的形态学算子的方法，但这些方法存在一定的观察者间的误差。
Sardjono等人[4]提出基于带电粒子模型的物理方法来提取脊柱轮廓，实现过程复杂且实用性不高。
叶伟等人[5]提出了一种基于模糊C均值聚类分割算法，该方法过程繁琐且实用性欠佳。
以上方法都只对椎体进行了分割，却无法实现对脊柱的整体轮廓分割。
深度学习在图像分割的领域有很多应用。
Long等人提出了全卷积网络[6]（Full Convolutional Network，FCN），将卷积神经网络的最后一层全连接层替换为卷积层，得到特征图后再经过反卷积来获得像素级的分类结果。
通过对FCN结构改进，Ronneberger等人提出了一种编码-解码的网络结构U-Net[7]解决图像分割问题。
Wu等人提出了BoostNet[8]来对脊柱X线图像进行目标检测以及一个基于多视角的相关网络[9]来完成对脊柱框架的定位。
上述方法并未直接对脊柱图像进行分割，仅提取了关键点的特征并由定位的特征来获取脊柱的整体轮廓。
Fang等人[10]采用FCN对脊柱的CT切片图像进行分割并进行三维重建，但分割精度相对较低。
Horng等人[11]将脊柱X线图像进行切割后使用残差U-Net 来对单个椎骨进行分割，再合成完整的脊柱图像，从而导致分割过程过于繁琐。
Tan等人[12]和Grigorieva等人[13]采用U-Net来对脊柱X线图像进行分割并实现对Cobb角的测量或三维重建，但存在分割精度不高的问题。
以上研究方法虽然在一定程度上完成脊柱分割，但仍存在两个问题：（1）只涉及椎体的定位和计算脊柱侧凸角度，却没有对图像进行完整的脊柱分割。
显微镜光学配置图说明书
Supplementary MethodsOptical configuration:A diagram of the optical configuration used for the photobleaching experiments is shown insupplemental figure 1 below.Supplemental Figure 1. Diagram of the optical configuration of the side-port for photobleaching.e. he d or the YFP bleaching experiment shown in figure 1, the microscope filter cube used for bleaching rom 0DCSXscanning mirrorsView is from above, and the scanning mirrors are at the rear of a Nikon TE-300 inverted microscop The dichroic mirror near the tube lens is a long-pass extended reflection mirror (650 DCXRU). The light from an argon-ion laser (Coherent Sabre) was coupled into an optical fiber and connected to the side-port at the connector shown at the right side of the figure. To preview the fluorescence and select cells, an in-house developed fiber-optic coupled high-power blue light emitting diode (LED) source (patent pending) was connected in place of the laser coupling fiber. Depending on the experiment a band-pass filter was sometimes included before coupling the LED emission to the fiber. In some experiments an additional dichroic mirror, 440 nm long-pass (440DCLP), was included between t fiber-optic coupler and the divergence-correcting lens to allow the additional coupling of a liquid-fille light guide (Oriel) to permit the use of a xenon arc lamp (Cairn).F contained a 545nm long-pass dichroic (545DCLP) and a 540-600nm band-pass emission filter(HQ570/30). A portion of the YFP emission could be monitored visually while scattered light f the 514.5 nm laser excitation was blocked. For bleaching experiments using laser lines shorter than 514.5, a filter cube containing a 510 long pass dichroic and a 510-560 band-pass emission filter (510DCLP and HQ535/50 respectively) was used. The filter cube for the 2-photon excitationcontained a 700 nm short-pass, UV reflecting, dichroic and a 710 short pass emission filter (70and E710SP respectively).YFP photoconversion revisited: confirmation of the CFP-like speciesMichael T Kirber, Kai Chen & John F Keaney JrIn experiments to check if the fluorescent decay product was visible with arc lamp illumination, a filter experiments to check if bleaching using arc lamp illumination produced the fluorescent decay ht , and en rlabs. ther than observing that the fluorescent decay product of YFP could be excited using a configuration ell culture and plasmid transfection: cube containing a 405-445 band-pass excitation filter, a 455 long-pass, extended reflection dichroic, and a 460-500 nm band-pass emission filter (D425/40X, 455DCXRU, and D480/40M respectively) was used. Infrared light was removed from the arc lamp output using a short wavelength visible and UV reflecting cold mirror (Thorlabs).In product, the fiber coupler was removed from the side port and the output from the liquid-filled lig guide and a collimating lens were coupled directly in place of the fiber-optic coupler. The 440DCLP dichroic was left in place. The filter cube used for bleaching contained, a 460-500nm band passemission filter inserted in reverse direction in the excitation position, a 510 nm long-pass dichroic a 510-560 nm band-pass emission filter ( HQ480/40M, 510DCLP, and HQ535/50M respectively) Bleaching YFP about 50% took 2 hours and when the 440DCLP mirror was removed and the CFP filter cube (D425/40X, 455DCXRU, and D480/40M) selected, the fluorescent decay product was se with the arc lamp illumination. All filters and dichroic mirrors were purchased from ChromaTechnology. Optical fiber, lenses, and optomechanical components were purchased from ThoO appropriate for exciting CFP using single photon (arc lamp) or 2-photon excitation, we did not try to determine the excitation spectrum of this byproduct. Such experiments might well be worthwhile but we are not presently set up to carry them out.Cvitrogen) and transfection with overexpression plasmids was ) was age acquisition and display:COS-7 cells were cultured in DMEM (In carried out using Fugene 6 (Roche) in cells at 70% confluency according to the manufacturer’sinstructions. PTP1B trapping mutant expression vector pcDNA6.2/YFP-PTP1B (D181A/Q262A constructed by using PCR subcloning technique with pcDNA6.2/N-YFP vector (Invitrogen) and pJ3H-PTP1B (D181A/Q262A)(kindly provided by Dr. Zhong-Yin Zhang, Indiana University). Cells were grown on glass cover slides and fixed with 4% paraformaldehyde.Imas designed and built in-house in collaboration with the laboratory of inal irror d between the number of counted photons and the brightness of the display.The 2-photon microscope used w Dr. Peter So at the Massachusetts Institute of Technology. The optical microscope portion of the system was a Nikon TE300 and the objective used was a 100X, 1.3 NA, oil-immersion type. Orig images obtained with 2-photon excitation (800 or 916 nm excitation) were 384x384 pixels with each pixel imaging 130 by 130 nm in the sample, which is beyond the resolution capability of the system. The dwell time at each pixel was 2 ms. Images shown in figure 1 are cropped from the originals and are 280 by 280 pixels. The fluorescence at each channel was measured with photon counting photomultiplier tubes (Hamamatsu R4700P-01 for the green channel and R4700P for the bluechannel). The green channel was separated from the red using an extended reflection dichroic m 565 nm long-pass (565DCXR) and the blue and green channels were separated using a 500nm long-pass extended reflection dichroic mirror (500DCXR). The pass-bands of the filters are given in the body of the text. The number of counts at each location in the sample was stored as a 16 bit unsigne integer. Images were imported into ImageJ as raw data. The colors for images in figure 1a-f were chosen to approximate the actual color of the fluorescence. The scale bars indicate the relationshipColocalization:In quantitatively assessing the degree of colocalization of two distinctly fluorescently labeled (or the different colored images each as a sample of a e or expressed) compounds in a cell, it is useful to treat random process which accurately represents it statistically (ergodicity). The normalized covarianc correlation coefficient between 2 sets of data, which in this case are images E and F which are N i x N j in size and contain elements e ij and f ij respectively, can be written as}Where E{ } denotes the “expected value” and E ¯ is the arithmetic mean of the pixel values in image E nd F ¯ is the mean of image F. This calculation has been applied to quantitatively assess colocalization E ()()ij ij e E f F ρ−−a (Vereb et al .). Because expectation is a linear operator, this expression can be rearranged so that the contribution at each pixel pair to the correlation coefficient is clear.ρ==We can then display an image G* with pixel values g*ij , the sum of all the pixels being the correlationoefficient. c*ij ij ij e f E F N N g −=or simplicity we normalize this so that we display images where the mean of all of the pixels, G ¯, is e correlation coefficient.F thij g =ll of the values can be easily calculated using ImageJ (Wayne Rasband, NIH).this manner we can easily compare different size sets of images and not lose the quantitative ove comparing the degree of colocalization under different experimental conditions some caution is oth ference:atko J, Vamosi G, Ibrahim SM, Magyar E, Varga S, Szollosi J, Jenei A, Gaspar R Jr, AIn information. Areas where the normalized covariance image is positive indicate colocalization ab that predicted by random uniform distributions of the 2 fluorescent species. Additionally, there are generally some regions where the pixels have a negative value. These regions correspond to areas where the colocalization of the 2 labeled compounds is less than would be predicted by a uniform random distribution.In needed. For example the regions for which the computation is performed should be similar under b sets of conditions (i.e. ratio of area of background to area of cell interior).re Vereb G, M Waldmann TA, Damjanovich S. Proc Natl Acad Sci U S A. 2000 May 23;97(11):6013-8.。
The X-ray spectrum of NGC 7213 and the Seyfert--LINER connection
width (full width at zero intensity ∼ 13000 km s−1, Phillips 1979). A variety of optical emission lines are observed in this galaxy with velocities ranging from 200 to 2000 km s−1 FWHM (Filippenko & Halpern 1984, hereafter FH84). FH84 argue that photoionisation of clouds spanning a range of densities and velocities by a non-stellar continuum is likely to be the mechanism creating the optical line emission. By invoking high density rather than high temperature clouds, FH84 eliminate the need for shock heating.
Accepted . Received ; in original form
ABSTRACT
We present an XMM-Newton observation of the Seyfert-LINER galaxy NGC 7213. The
RGS soft X-ray spectrum is well fitted with a power law plus soft X-ray collisionally
Since its discovery as a low luminosity X-ray source (Marshall et al. 1978) NGC 7213 has been observed with several X-ray missions. The presence of a soft X-ray excess in NGC 7213 was implied by the results of an EXOSAT spectral survey of AGN (Turner & Pounds 1989) when the measured absorbing column for a single power law fit was found to be significantly lower than the Galactic value. In addition, the UV flux measured by Wu, Boggess & Gull (1983) was higher than would be expected from an extrapolation of the optical flux indicating that NGC 7213 may have a big blue bump (BBB), although weak compared to most Seyfert galaxies. The BBB is often interpreted as thermal emission from an accretion disc; if accretion discs are present in LINERs it is important to determine their properties if we are to understand the underlying emission mechanisms.
A large Wolf-Rayet population in NGC300 uncovered by VLT-FORS2
a r X i v :a s t r o -p h /0209259v 1 13 S e p 2002Astronomy &Astrophysics manuscript no.(will be inserted by hand later)A large Wolf-Rayet population in NGC 300uncovered byVLT-FORS2⋆H.Schild 1,P.A.Crowther 2,J.B.Abbott 2,and W.Schmutz 31Institut f¨u r Astronomie,ETH-Zentrum,CH 8092Z¨u rich,Switzerland2Dept of Physics and Astronomy,University College London,Gower St,London WC1E 6BT,United Kingdom 3Physikalisch-Meteorologisches Observatorium,CH-7260Davos,SwitzerlandReceived /AcceptedAbstract.We have detected 58Wolf-Rayet candidates in the central region of the nearby spiral galaxy NGC 300,based on deep VLT-FORS2narrow-band imaging.Our survey is close to complete except for heavily reddened WR stars.Of the objects in our list,16stars were already spectroscopically confirmed as WR stars by Schild &Testor and Breysacher et al.,to which 4stars are added using low resolution FORS2datasets.The WR population of NGC 300now totals 60,a threefold increase over previous surveys,with WC/WN ≥1/3,in reasonable agreement with Local Group galaxies for a moderately sub-solar metallicity.We also discuss the WR surface density in the central region of NGC 300.Finally,analyses are presented for two apparently single WC stars –#29(alias WR3,WC5)and #48(alias WR13,WC4)located close to the nucleus,and at a deprojected radius of 2.5kpc,respectively.These are among the first models of WR stars in galaxies beyond the Local Group,and are compared with early WC stars in our Galaxy and LMC.Key words.galaxies:NGC 300–stars:Wolf-Rayet –stars:fundamental parameters1.IntroductionOver 500Wolf-Rayet stars have been identified in Local Group galaxies,principally the Milky Way,M31and M33.These stars beautifully trace young stellar populations,and their number and distribution reacts sensitively to metallicity,which varies by an order of magnitude from the Small Magellanic Cloud (SMC)to M31.Detailed stud-ies of individual WR stars in Local Group stars have been carried out (e.g.Smartt et al.2001;Crowther 2000;Crowther et al.2002)using 2–4m class telescopes.The availability of 8–10m class telescopes permits the discovery and study of individual stars at greater dis-tances,spanning a greater range of metallicities.As a first application,we present here VLT imaging and spec-troscopy of WR stars in NGC 300,located in the Sculptor group at a distance of 2Mpc (Freedman et al.2001).It’s metallicity is bracketed by the Milky Way and Large Magellanic Cloud (LMC)and therefore we expect a sim-ilarly large number of WR stars in NGC 300.Previous surveys have however failed to identify them.A large pop-ulation might also be anticipated since NGC 300is a late type spiral,reminiscent of M33,which harbours at least2Schild et al.:WR stars in NGC300Fig.1.Finding chart for WR stars/candidates in NGC300.Left:nuclear region,right:area northwest of the nucleus. The horizontal bar represents10′′.North to the top,East to the left.ized by oxygen content.Although there have not beenany recent studies of the NGC300metallicity gradient,Deharveng et al.(1988)used data from Pagel et al.(1979)and Webster&Smith(1983),to imply a range betweenlog(O/H)+12=8.9in its nucleus and8.3in its outer spi-ral arms.Similar conclusions were obtained by Zaritskyet al.(1994)from a recalibration of previous results.Onewould expect a WC/WN ratio of∼1/2from comparisonwith Local Group galaxies,yet the census of WR stars inNGC300indicates WC/WN∼2.Consequently,we mightexpect that the WR population of NGC300is highly in-complete,particularly amongst WN stars.In this paper we present results from a new imag-ing survey of the central region of NGC300with theVery Large Telescope(VLT).New WR candidates areidentified,some of which are spectroscopically confirmed.Spectral types of the latter are discussed,with particularreference to the WC/WN ratio of the inner galaxy.Ananalysis of two apparently single WC stars is presented,one located close to its nucleus,the other at∼50%of theHolmberg radius,ρparisons are made with recentcomparable studies of WC stars in a variety of metallicityenvironments.2.ObservationsWe observed NGC300with the VLT UT2(Kueyen)and Focal Reduced/Low Dispersion Spectrograph#2(FORS2)during2000September2–3.The conditions werephotometric but the seeing was highly variable,changingfrom0.6to3.5′′and we used the instrument accordinglyin imaging and spectroscopic mode.2.1.ImagingWhile the seeing was good(typically0.8′′)we obtainedimages through two interferencefilters with central wave-lengths at4684˚A and4781˚A and band widths of66˚Aand68˚A,respectively.The formerfilter is well matchedto the strong WR emission feature containing the N iiiλ4640,C iiiλ4650,C ivλ4658and He iiλ4686emissionlines.The wavelength range of the latterfilter falls intoa spectral region that is free from emission lines.We col-lected two images in eachfilter with exposure times of600sec.These frames were centred atα:0h54m59.0sandδ:–37◦40′59′′(2000).At mediocre seeing condi-tions short exposures through Bessel B and Vfilters werealso collected.Only one of the V frames was of sufficientquality,but it was slightly offset such that only V-bandmagnitudes of WR candidates with RA larger than00h54m46.7s could be measured.The standard collimator was used,providing afield-of-view of6.8′×6.8′with an image scale of0.2′′/pixel.The detector was a2048×2048Tektronix CCD with24µmpixels.The data were de-biased andflatfielded with framestaken in the following morning twilight.We used theDAOPHOT software package to get relative photometry.These were converted into absolutefluxes with the pho-tometric standard stars in thefield of NGC300listed inPietrzi´n ski et al.(2002a).2.2.SpectroscopyFORS2was used in long slit mode(LSS)to obtainspectroscopy for selected Wolf-Rayet stars and candi-dates.This mode was selected since narrow-band im-Schild et al.:WR stars in NGC3003 Table1.List of Wolf-Rayet stars and candidates in the central regions of NGC300.Two other WR stars are known outside the presentfield–WR8(WN)in Deh30from Schild&Testor(1992)and a WC in Deh24from D’Odorico et al.(1983).Deprojected galactocentric distances are expressed as a fraction of the Holmberg radius(ρ0=9.75′≃5.75 kpc).ST1)Brey2)Remark5) 205442.37-37437.318.93 1.02out0.3353b WC4405442.78-37431.817.880.25out0.3253c WN605444.75-374240.019.030.13out0.26WN115) 1005450.21-374029.719.680.5220.040.1076aWR9I-11205450.53-373826.720.87 1.5722.120.36771405450.62-374021.720.39 1.4921.640.1176b WC4-65) 2305453.11-374347.319.720.0819.710.38882405453.80-374347.220.00 1.5521.340.3890WC5WR22905456.76-374044.019.71 2.5821.610.0898WC4-55) 310550.65-373851.520.74 1.6822.140.31II-134055 3.34-374242.020.36 1.9721.870.35WC5-636055 3.64-374320.018.060.1317.970.4237055 3.75-374251.6blend 2.018.560.3738055 4.09-374318.919.070.6419.530.43WN9-10WR6410559.98-374212.521.640.9522.440.434305512.07-374121.919.840.1219.830.42137d4405512.19-374119.717.710.1917.800.42137d4505512.21-374120.418.550.4018.790.42137dV-14705512.41-374129.019.68 2.9521.190.43137b WC5-6WR13IV-3 4905512.58-374139.518.460.3118.850.45137a WN75305513.23-374139.820.63 1.1221.540.46WN4-65505513.47-374146.320.64 1.8722.300.47WN4-54Schild et al.:WR stars in NGC300Fig.2.Finding chart for WR stars/candidates in the southern spiral arm.The saturated object is the galactic fore-ground star CD−38◦301.The horizontal bar represents10′′.North to the top,East to theleft.Fig.3.Finding chart for WR stars/candidates in the northeast of the nucleus.Some vignetting occurred in the upper left corner(northeast).The horizontal bar represents10′′.North to the top,East to the left.ages were not obtained in advance of the observing run. The300V grating,GG435filter and 1.0′′slit width provided spectroscopy coveringλλ3500–8970at a dis-persion of1.7˚A/pixel,corresponding to a resolution of R=∆λ/λ∼440at5900˚A.Eight targets were observed with this configuration using1800sec exposures,and will be discussed in Sect.4.Generally,two WR stars were ob-served in each observation via a suitable choice of posi-tion angle using the FORS Instrument Mask Simulator (FIMS)software.Relativeflux calibration was achieved using short exposures for standard stars Feige110and LTT1788.Absolute calibration required convolution with b and v(Smith1968)narrow-bandfilters,which were ap-proximated to our m4781photometry.For three stars,higher resolution600R grating obser-vations were obtained,using the GG435filter,coveringSchild et al.:WR stars in NGC3005Fig.4.Finding chart for WR stars/candidates east of the nucleus(top right)and int he H ii regions Deh137(top left),Deh118/119(bottom left)and Deh77/79(bottom right).The horizontal bars represent10′′.North to the top, East to the left.λλ5330–7540,at a dispersion of0.7˚A/pixel,correspond-ing to a resolution of R∼1000at6300˚A.Two1800sec ex-posures were taken before seeing conditions deteriorated.Identicalflux standards were again used with this con-figuration.For all datasets a standard data reduction wascarried out using FIGARO1i.e.,bias subtraction,flatfieldcorrection,extraction,wavelength andflux calibration.6Schild et al.:WR stars in NGC300detected obviously depends on the signal/noise ratio.In this case the signal is theflux difference between on-offframes.Wefirst identified theλ4684emission objects on the difference image.The selection criteria were a stellar appearance and a peak intensity of at least6σ.The prob-ability for any of the listed objects of having indeed a WR excess is therefore very high.For these objects we sub-sequently picked the V,emission(λ4684)and continuum (λ4781)magnitudes from the(rather long)DAOPHOT photometric list.It should be noted that photometry is hampered by a variable background due to unresolved galaxy emission and heavy crowding,which can be particularly severe in OB associations.It follows that while the identification as aλ4684emission object is rather reliable,the quantitative measurement of a WR excess is less certain.Our narrow-band images are complete down to23.7mag while the3σdetection limit was at24.7mag.We present a catalogue of the58WR stars/candidates identified in our images in Table1.We include spectral types taken from the literature,updated in case of revi-sions from our new spectroscopy(see Sect.4),plus as-sociated H ii regions from Deharveng et al.(1988).De-projected galactocentric distances were calculated using parameters from Table1of Deharveng et al.(1988).In Figs.1to4we givefinding charts for the WR candidates. In all of them a horizontal bar is plotted that represents 10′′.The orientation is as usual:North to the top and East to the left.Allfinding charts are from ourλ4684 narrow-bandfilter images.3.2.Nature of candidates39out of our58WR candidates with aλ4684excess are newly identified in this study.We compare theλ4781con-tinuum magnitudes with theλ4684excess in Fig.5.Stars with previous(or new)spectroscopic confirmation are in-dicated,as shown in the key.We include estimates of the absolute magnitudes atλ4781,assuming a distance mod-ulus of26.53mag to NGC300(Freedman et al.2001) and Aλ4781=0.36mag,corresponding to E B−V=0.10mag which is the mean interstellar reddening towards H ii re-gions of NGC300withinρ/ρ0=0.5derived by Deharveng et al.(1988).Fig.5clearly separates the largeλ4684excesses of the visually faint WC and early-type WN stars,from the small excesses of the visually bright late-type WN stars and WR binaries.Approximate line equivalent widths(in˚A)are also presented in thefigure,as estimated from stars in which optical spectroscopy is available(see also Fig.4of Massey&Johnson1998).Such comparisons would repre-sent the sole means by which WR populations might be identified in galaxies which are too distant(or reddened) for confirmatory spectroscopy to be obtained,even with large8–10m telescopes.Previously known WR stars tend to have largeλ4684 excesses of>∼1mag,corresponding to emission parison between theλ4781continuum mag-nitudes of the WR candidates in NGC300and theλ4684 excess(stars).Spectroscopically confirmed WR stars are presented in the key.Approximate absolute magnitudes and line equivalent widths are indicated,as discussed in the text.Three WR stars are not shown in thisfigure–#1(located at the edge of the image surveyed–Fig.1), #37and#51(both are severely blended).lent widths of>∼100˚A.Exceptions include those WR stars which lie in well surveyed OB associations.Wefind six more WR candidates with such a large WR excess(#3, #5,#22,#30,#31and#37).They are rather faint with m4684>20.5mag,which is presumably why they escaped earlier detection.From this sample,#22and#30were observed spectroscopically,such that both were confirmed as WR stars–see Sect4.Single,early-type WC stars haveλ4650–4686emission equivalent widths of>∼1000˚A,and are visually rather faint. Consequently only three WC stars,with an excess of≥2.5 mag are likely to be single,namely#29,#47and#48. Two of these stars are discussed in detail in Sect.5.Other WC stars are almost certainly multiple,or suffer contami-nation from stars along the same line-of-sight.Early-type WN stars possess He iiλ4684emission equivalent widths of100–400˚A,corresponding to excesses of1–2mag.From Fig.5,it is likely that#28and#55are single,whilst others are probably multiple.For those remaining WR candidates with excesses greater than1mag,#5is a strong WC+O candidate,whilst the remainder are prob-able WN+OB systems.There are also a handful of new WR candidates with an excess in the range0.3to1mag(#9,#10,#41,#42, #51,#52and#54),corresponding to emission equivalent widths in the range∼30–100˚A.Their relatively small line strengths suggests that if they are visually bright,with M4781<−6,they are WR binaries(e.g.#11)or single WN7–9stars(e.g.#38).If they are visually faint,they are probably weak-lined single WN stars(e.g.#41).From this group,#9was observed spectroscopically and confirmed as a WN star–see Sect.4.Numbers51and54lie in theSchild etgiant H ii region Deh137while#10is another WRin the nuclear area of NGC300(Fig.1).25WR candidates have aλ4684excessmag.It is possible that some of these stars areline WR/Of stars.Except in one case,they arebright,with M4781<−6,as expected for a WRsingle late WN star,or an extreme O-typestrong He iiλ4686emission(i.e.an Of star).was independently found by Bresolin et al.classified as a WN11star.Ourλ4684excess ofis in close agreement with the spectroscopy ofal.(2002b).This indicates that a He ii excess of∼can be reliably measured with thishence also that Of stars and very late WN starsbe detected.Most candidates from the presentprobably WR rather than Of since,since byHe iiλ4686equivalent widths of the latter do not∼12˚A(Bohannan&Crowther1999).pleteness,Surface Density and the WC/WNRatioIn addition to verifying the likely-hood of whether ourcandidates are genuine WR stars,how complete is oursurvey?The continuumfilter centred at4781˚A lies mid-way between the usual Smith(1968)WR narrow-band b(4270˚A)and v(5160˚A)filters.Typical intrinsic coloursof WC and WNE stars are(b−v)0∼−0.2±0.1,such thatone would expect b−v∼−0.1±0.1mag for WR starsin NGC300,given typical extinctions of E(b−v)∼0.1mag(equivalent to E(B−V)=0.12mag).Consequently,continuumfilter measurements should correspond closely(within∼0.1mag)to b or v magnitudes.i.e.a complete-ness to v=23.7mag will be equivalent to M v∼−3.2mag.According to Table28from van der Hucht(2001),94%of the227known Galactic WR stars are brighterthan M v=−3.5mag,so our census of the central regionof NGC300should be reasonably complete,except thosesuffering from high visual extinction.In Fig.6we plot the WR surface density versus thegalactocentric distance.The WR distribution in the nu-clear region is particularly interesting.While the very cen-tre is apparently free of WR stars wefind a sharp in-crease of the surface density at a galactocentric distance ofabout0.4kpc.Further outside it dropsfirst to a minimumat around1kpc and rises again outwards.Qualitatively,a similar behaviour is observed in our galaxy(van derHucht2001)but in NGC300the drop is much shallower,about−0.3dex between0.5and2kpc instead of−1.5inthe galaxy.The highest surface density in NGC300oc-curs in the Deh137H ii region,alias OB association AS102which contains15WR stars in an area that spans0.3×0.3kpc implying a WR density of about150WRstars/kpc2.Massey&Johnson(1998)compare WR sur-face densities of other Local Group galaxies,such that WRsurface densities range from1/kpc2in the SMC,to2inthe LMC and∼4in M33.the nucleus.Fig.7.The relative number of WC and WN stars in LocalGroup galaxies versus metallicity(Massey2003),supple-mented by NGC300(solid)from the present work.TheWC/WN ratio for IC10is probably an overestimate.As discussed in the introduction,the WC/WN ratio forNGC300prior to the present study,i.e.∼2,was unusuallyhigh relative to more complete surveys of Local Groupgalaxies.Ideally,one might use additional narrow bandfilters at(C iv)λλ5801-12plus a nearby continuum regionto discriminate between WN and WC stars,as recentlycarried out by Royer et al.(2001)for IC10.In the absenceof suchfilters,we have been able to infer likely WN orWC subtypes for those stars without spectroscopy frominspection of Fig.5.We suggest that at least13WR starsin NGC300are WC stars,i.e.12for which spectroscopyis available,plus#5.A further3may host WC binaries,8Schild et al.:WR stars in NGC300Fig.8.Low dispersion FORS2spectroscopy of four previously identified WR stars in NGC300.Fig.9.Low dispersion FORS2spectroscopy of four newly identified WR stars in NGC 300.namely #12,#31,#33,such that the WC/WN ratio for the central regions of NGC 300is ≥12/46=0.3,or more likely ∼15/43=0.35.This falls close to that observed in comparable regions of M33,according to Massey (2003),as illustrated in Fig.7.4.Spectroscopy of Wolf-Rayet stars 4.1.Previously identified WR starsWe present flux calibrated low dispersion FORS2spec-troscopy of four previously observed NGC 300WC stars in Fig.8.These datasets are superior to previous 4m ob-servations,and so allow us to obtain revised spectral types,using the scheme of Crowther et al.(1998).We revise the original classification for #29,alias WR3(Schild &Testor 1991),from WC4–5to WC5since our dataset reveals weak C iii λ5696,with W λ(λ5696)/W λ(λλ5801-12)∼0.1and O iii-v λ5592weak/absent.This star is probably single,given that its emission line spectrum is comparable in strength (e.g.W λ(λλ5801-12)∼800˚A )to apparently single Galactic and LMC WCE stars.A firm classification is possible for #40,alias WR6(Schild &Testor 1992)for which we also assign WC5(updated from WC4–6)since C iii λ5696is again present,with a similar strength to O iii-v λ5592and W λ(λ5696)/W λ(λλ5801-12)∼0.1.#40is almost certainly multiple,since W λ(λ5801-12)∼230˚A .Testor &Schild (1993)previously assigned a WC5spectral type for #24(their WR11),which we revise to WC4,given that W λ(λ5696)/W λ(λλ5801-12)≤0.05.C iv λ5801–12is again unusually weak,with W λ(λ5801-12)∼200˚A indicating either binarity or a line-of-sight companion.The spectral appearance of #48,alias WR13(Testor &Schild 1993),alias IV-3(Breysacher et al.1997)is in marked contrast to the other WCE stars whose spec-troscopy is presented here,with much broader lines –FWHM(λλ5801-12)∼86˚A versus 36–47˚A .Breysacher et al.(1997)interpreted this large FWHM as an indication of a (rare)WO subtype,which possess strong O vi λλ3811-34emission lines,and assigned a WO4spectral type ,whilst our spectroscopy reveals that O vi is weak/absent in #48.Since C iii λ5696is also absent,a WC4spectral type is appropriate.Willis et al.(1992)discuss problems with us-Schild et al.:WR stars in NGC 3009parison between FWHM(C iv λλ5801-12),in ˚A ,and galactocentric distance for early WC stars in NGC 300(solid)and M 33(open,Willis et al.1992),as a fraction of the Holmberg radius.ing FWHM as indicators of spectral type for WC stars in M33.We suspect that #48is single since W λ(λλ5801-12)∼1500˚A .4.2.Newly identified WR starsWe present optical spectroscopy of four newly identifiedNGC 300WR stars in Fig.9,two WN and two WC stars.The WC stars #1and #22are rather similar.They have lines widths which are higher than #48,with FWHM(λλ5801–12)∼91-100˚A ,and similar line strengths,W λ(λλ5801-12)∼500˚A .WC4subtypes are appropriate forboth stars since there is no evidence of C iii λ5696,with O vi λλ3811-34weak.Both stars are probably binaries.The two WN stars #9and #30are early-type,since N v λλ4603-20is prominent,with N iii λλ4634–41weak (#9)or absent (#30).Following the classification scheme of Smith et al.(1998)one obtains a spectral type of WN4–5for #9(N iv λ4058∼N v λλ4603-20),and WN3–4for #30(the region around N iv λ4058is noisy).One cannot use the (primary)He i-ii classification diagnostics for these stars due to the strong nebular contamination,and weak He i λ5876emission.4.3.WC line widthWillis et al.(1992)identified a correlation between line width (FWHM C iv λλ5801-12)and galactocentric dis-tance for WCE stars in M33in the sense that stars at larger galactocentric distance (i.e.lower metallicity)had broader lines than those in the nucleus (with higher metal-licity).We present our measurements for 6WC stars in NGC 300in Fig.10,supplemented by data from Schild&Testor (1991,1992)for #14(WR1)and #47(WR5),and including data from Willis et al.(1992)and refer-ences therein for M33.For NGC 300,there is a very large scatter in FWHM at ρ/ρ0∼0.4,arguing against a tight correlation in general,although the present results are in favour of a deficit of broad-lined WC stars in the nucleus.Nevertheless,firm conclusions await spectroscopy of larger numbers of WC stars in both galaxies.5.Analysis of WC starsAs discussed above in Sect.4,two WC stars in NGC 300are apparently single,and have sufficient quality observa-tions for detailed analyses to be carried out.Ultimately,large numbers of WR stars need to be studied in galax-ies spanning a wide range metallicities to place adequate constraints on evolutionary models.Recent studies,us-ing identical techniques,have been presented for single WC stars in the Milky Way (e.g.Dessart et al.2000),LMC (Crowther et al.2002),M31(Smartt et al.2001)and M33(Abbott et al.2003).We now proceed to study #29(WC5),located close to the nucleus of NGC 300with a probable metallicity of ∼Z ⊙according to 104O /H =7.5−5.3ρ/ρ0(Deharveng et al.1988),and #48(WC4),located at ρ/ρ0=0.43with ∼0.6Z ⊙.5.1.TechniqueWe employ the non-LTE code of Hillier &Miller (1998),which iteratively solves the transfer equation in the co-moving frame subject to statistical and radiative equilib-ria in an expanding,spherically symmetric and steady-state atmosphere.Specific details of the (extremely com-plex)He,C,O,Ne,Si,P,S,Ar,Fe model atoms used for our quantitative analysis are provided in Crowther et al.(2002).We assume that the wind is clumped with a volume filling factor,f ∼0.1.We parameterise the filling factor so that it approaches unity at small velocities.As usual,a series of models were calculated in which stellar parameters (T ∗,log L/L ⊙,v ∞˙M/√10Schild et al.:WR stars in NGC300 The wind ionization balance is ideally selected onthe basis of isolated optical lines from adjacent ioniza-tion stages of carbon and/or helium,e.g.He iλ5876/He iiλ5412.In practice,this was difficult to achieve because ofthe severe blending,so our derived temperature should betreated as approximate.Detection of He iλ5876appearsto be robust in#29,due to its relatively low wind velocity,whilst there is an ambiguity in this feature for#48,sinceit is possible that the observed feature represents the elec-tron scattering wing of C iv for which we have adoptedthefilling factor,f.We also simultaneously match C iiiλ6740and C ivλ5801,the former selected in preferenceto C iiiλ5696which is very sensitive to the exact ion-ization structure(Hillier&Miller1998;Crowther et al.2002).The standard C/He diagnostic,He iiλ5412/C ivλ5471,was used since their relative strengths are insen-sitive to temperature and mass-loss.Oxygen abundanceswere difficult to constrain,since we relied solely on O iii-vλ5592(Crowther et al.2002).Consequently,caution isadvised when comparing the present O/C determinationswith(Galactic and LMC)WC stars for which the superiorλλ2800–3100diagnostics are available.5.2.Results for NGC300#29(WR3,WC5)Our FORS2spectroscopic data of#29is shown in theupper panel of Fig.11.Overall,the spectrum is reason-ably well reproduced by our modelfit,except that the C iiiλ5696profile is strongly underestimated,whilst C iv λλ5801–12is40%too weak.From our recent experienceit is difficult to simultaneously reproduce the strength of C iiiλ5696feature together with other diagnostics in early WC stars.Wefind T∗∼100kK,log(L/L⊙)=5.5, v∞∼2700km s−1,and˙M∼10−4.6M⊙yr−1.We estimate C/He∼0.08by number from He iiλ5412/C ivλ5471.Theweak O iii-vλ5592feature suggests a low oxygen content of O/He≤0.05by number.5.3.Results for NGC300#48(WR13,WC4)We compare our spectroscopy of#48with our synthetic model in the lower panel of Fig.11.Again,reasonably good agreement is achieved,although the broad emis-sion lines of#48hinder detailed comparisons.The blend comprising principally C iiiλ4647–51,C ivλ4660and He iiλ4686is rather too strong in the synthetic model. Our derived parameters are T∗∼95kK,log(L/L⊙)=5.2, v∞∼3750km s−1,and˙M∼10−4.8M⊙yr−1.We esti-mate C/He∼0.5by number,although this ratio should be treated with caution,given the poor quality of the obser-vations–recall#48has the faintest continuum(v=23.5 mag)of all58WR candidates in NGC300.The O iii-v λ5592feature suggests a high oxygen content of O/He≥0.1 by number.Fig.11.Upper panel:Synthetic spectralfit(dotted)to FORS2observations(solid)of NGC300#29(WR3, WC5),de-reddened by E B−V=0.10mag.Close up views of the C iii-iv-He iiλλ4650–4686and C ivλλ5801-12re-gions are indicated.Lower panel:Same for NGC300#48 (WR13,WC4)for a reddening of E B−V=0.15mag.parison with WC stars in the Galaxy and LMC Crowther et al.(2002)recently contrasted the properties of Solar neighbourhood and LMC WC stars,to which we can now add NGC300#29and#48.The upper panel in Fig.12compares(nuclear)luminosities and(C+O)/He abundances for WC stars in the three galaxies.Nuclear luminosities are derived by taking into account the wind blanketing effects discussed by Heger&Langer(1996).In contrast with the results of Heger&Langer,who indicated revisions of up to0.3dex in luminosity,revised mass-loss rates due to clumping yield rather small corrections,typ-ically0.05dex.Current masses of16.3and11.6M⊙are determined for#29and#48,respectively.Crowther et al. (2002)found that low metallicity(LMC)WC stars possess higher luminosities than those at high metallicity(Milky Way).This can be explained since one would require a higher initial mass cut-off,for a massive star to progress through to the WC stage at low metallicity,because of re-duced mass-loss rates during the main-sequence and post-main sequence evolution.The small sample of NGC300。
trixell 探测器参数
trixell 探测器参数医疗器械2009-06-01 17:22:55 阅读78 评论0 字号：大中小订阅 Pixium 4600X射线发生器名义电压: 40 - 150 kVpX射线曝光剂量: 1.25 - 2.5uGy / 150 - 300uRX射线最大线性剂量: 30uGy / 3500uR象素尺寸: 143um射线感应区域: 水平3001 象素, 429mm, 垂直3001 象素, 429mm射线窗口时间: 1-500 ms特殊曝光模式: 10-4000ms图像读出时间: 1.25秒动态范围: 14位外形尺寸: 533 * 488 * 45mm重量: 20KGPixium 4700像素尺寸：154 μmX-ray sensitive array:（射线感应区域）in overview mode（全视野）381.9 x 294.1 mmin zoom 1 mode （放大模式1）221.7 x 221.7 mmin zoom 2 mode（放大模式2）157.7 x 157.7 mmImage size （图像点阵大小）2 480 x 1 910 pixelsOperating modes and performancesA/D conversion dynamic range （模拟数字转换器）14 bitsPixel grouping feature（点阵组合方式）: 1 x 1, 2 x 2, 4 x 2Maximum frame rate:（最大帧速度）1 x 1 overview mode（1*1全视野）, X-window duration射线窗口≤ 70ms毫秒7.5 fr/sec帧/秒.1 x 1 zoom 1 mode1*1放大模式1, X-window duration射线窗口≤ 25 ms 15 fr/sec.1 x 1 zoom2 mode（1*1放大模式2）, X-window duration（射线窗口）≤ 10 ms 30 fr/sec.2 x 2 overview mode, X-window duration ≤ 13ms 30 fr/sec.2 x 2 overview continuous mode 30 fr/sec.2 x 2 zoom 1 mode, X-window duration ≤ 5 ms 60 fr/sec.2 x 2 zoom 2 mode, X-window duration ≤ 7 ms 60 fr/se c.4 x 2 overview mode, X-window duration ≤ 8 ms 60 fr/sec.X-ray generator voltage range（X射线发生器名义电压）40 to 150 kVpDose range （剂量范围）5 to 4 500 nGy/frMaximum linear dose（最大线性剂量）45 μGy/frSensitivity:（灵敏度）highest gain（最大增益）( 2 x 2 mode（2*2模式）) 6.41 LSB/nGy typ.（6.41SB/nGy标准值） lowest gain （最小增益）0.14 LSB/nGy typ.（0.14SB/nGy标准值）Signal / Electronic noise:（信噪比）@ 5 nGy/fr in highest gain (1) 14 dB min.（在5nGy/fr，最大增益14DB）@ 1μGy/fr in lowest gain (1) 54 dB min.（在1nGy/fr，最小增益54DB）MTF @ 1 lp/mm, RQA5 (2) 60 % min.（MTF值，1线对/mm，60%）MTF @ 2 lp/mm, RQA5 (2) 30 % min.（MTF值，2线对/mm，30%）DQE @ 0 lp/mm, 1μGy/fr,RQA5 (2) 73 % typ.Residual signal (lag & memory effect) after 10 sec. exposure* at 30 fr/sec.:after 1 sec. ≤ 1.1 %after 10 sec. ≤ 0.25 %* Residual signal values in mode 2 gain 7 with 30 fr/sec.Electrical interfaces电源Single DC input voltage 24 V直流24VElectrical power （功率）75 WMechanical characteristicsOverall dimensions（外形尺寸）478 x 366 x 85 mm max.Weight 20 kg typ.(1) 1nGy = 0.115 μR @ RQA(2) RQA5 = 70 kVp, filtration = 2.5 + 21 mm aluminium。
nVent RAYCHEM NGC-40系统说明书
CONNECT AND PROTECT40The nVent RAYCHEM NGC-40 is a multipoint electronic control, monitoring and power distribution system with a uniquesingle-point controller architecture providing the most reliable central control and monitoring solution for your Heat Management System.By taking advantage of innovative modular packaging techniques, the NGC-40 system provides configuration and component flexibility so that it may be optimised for a customer’s project specific needs.CONTROL MODULES: NGC-40-HTC & NGC-40-HTC 3The NGC-40 uses a single controller module per heat-tracing circuit for maximum reliability. The NGC-40 control system can be powered between 100 to 240 Vac, while mechanical contactors (EMRs) or solid-state relays (SSRs) allow circuit switching up to 60 A at 600 Vac.There are dedicated control modules available for single phase (NGC-40-HTC)and three-phase (NGC-40-HTC 3) heat-tracing circuits. The NGC-40 control modules include ground-fault detection and protection. The control modules guarantee precise single phase and three-phase line current measurements. Up to eight (8) temperature sensors (RTDs) can be used for each heat-tracing circuit allowing a variety of temperature control, monitoring, and alarming configurations. The NGC-40 provides alarm outputs and digital inputs. The alarm output can be used to control an external annunciator.The digital input is programmable and may be used for various functions such as forcing outputs on and off or generating alarms, making the system more flexible to match each customer’s specific needs.SIL 2 SAFETY TEMPERATURE LIMITER: NGC-40-SLIMThe NGC-40 has a SIL 2 certified safety temperature limiter module.The module can be used with up to 3 temperature inputs for three phase heat-tracing circuits. The limiter can be associated with a NGC-40 controller and use currentinformation for latching the trip functionality. The front panel of the limiter module has LED indicators for various status conditions. The front panel also provides a button to confirm new set trip point, a reset trip button and a reset alarm button. The module has one output for the contactor and one output for external alarm annunciation. The safety temperature limiter can be reset via the digital input, the user interface nVent RAYCHEM TOUCH 1500 and nVent RAYCHEMSupervisor.Panel mounted advanced modular heat-tracing control systemPRODUCT OVERVIEWIO MODULE: NGC-40-IOIn addition to hardwiring an RTD directly into a Heat Trace Control module, RTDs can bewired to Input/output modules (NGC-40-IO) within the panel and assigned to heat-tracingcircuits through software. This means that a NGC-40 system can be optimised for thespecific application needs. Each IO module accepts up to four additional RTD inputs.RMM2The NGC-40 works with the MONI-RMM2 module. Each RMM2 module installed in thefield can accept up to 8 RTDs. 16 RMM2 Modules can be daisy chained together viaRS-485 for a total of 128 temperature inputs. Since multiple RMM2s can be networkedover a single cable to the NGC-40, the cost of RTD field wiring will be significantlyreduced.COMMUNICATION MODULE: NGC-40-BRIDGEThe NGC-40 system supports multiple communications ports, allowing serial interfaces(RS-485 and RS-232) and network connections (Ethernet) to be used with externaldevices. All communications with the NGC-40 panel are accomplished through theNGC-40-BRIDGE module which acts as the central router for the system, connecting thepanel’s control modules, IO modules, safety limiter modules, RMM2 Modules, as well asupstream devices such as TOUCH 1500 touch screen, Supervisor and Distributed ControlSystem (DCS). Communications to devices external to the NGC-40 panel are done viaModbus® protocol over Ethernet, RS-485 or RS-232.NVENT RAYCHEM TOUCH 1500The nVent RAYCHEM TOUCH 1500 is a panel mounted display used in conjunction withnVent RAYCHEM NGC-20 and NGC-40 Control and Monitoring Systems devices. TheTOUCH 1500 is rated IP 65 (NEMA 4) and can be mounted both indoors and outdoors. TheTOUCH 1500 kit includes all hardware required for mounting in a suitable electrical panel.TOUCH 1500R, a remote version of TOUCH 1500, is also available as a standalone solutionfor applications in which the controllers are not in the same location as the user interface.Make Your Systems Talk!Now more than ever, open communication systems, data integration, easy configurationand real-time monitoring are critical components of running an industrial installation.With the latest TOUCH 1500 software, nVent offers the full data integration of its heattracing systems with process control systems, allowing for the reduction of maintenanceand energy costs and, consequently, increasing process productivity. TOUCH 1500 to DCSmeans “data a la carte.” The heat tracing data you want, in your preferred format for yourDCS system.NVENT RAYCHEM SUPERVISOR SOFTWAREThe nVent RAYCHEM Supervisor software package provides a remote, graphic interfacefor the NGC-40. The software allows the user to configure and monitor various NGCsystems from a central location. It also provides an audible alarm tone, acknowledgesand clears alarms; and contains advanced features such as data logging, trending,implement changes in batches, and other useful functions. Users can access allinformation from anywhere in the world, making Supervisor a powerful management toolfor the entire Heat Management System.GENERAL NVENT RAYCHEM NGC-40 CONTROLLER MODULESApplication type The NGC-40 units shall be installed in non-hazardous areas.Hazardous area approved sensors shall be used when the system is applied toheat-tracing circuits in hazardous areas.or DC voltage. May be user programmable for: not used/force off/force on functions. It can beconfigured to be active open or active closed.Functional safety approvalFunctional safety according to Baseefa 10SR 0109 SIL 2 IEC 61508-1-1998 & IEC 61508-2-2000ETHERNET Type 10/100 BaseT Ethernet network Length 100 m (328 ft)Data rates 10 or 100 MB/s ProtocolConnection terminalsConnection terminalsShielded 8-pin RJ-45connector on front of moduleConnection terminals Spring-type, 0.5 to 2.5 mm2 (24 to 18 AWG). As the current to the modules require up to 2.05A @ 24Vdc (20 modules - see CAN Bus connection diagrams) the minimum wire size to thePART NUMBERSEurope, Middle East, AfricaTel +32.16.213.511Fax +32.16.213.604**********************©2021 nVent. All nVent marks and logos are owned or licensed by nVent Services GmbH or its affiliates. All other trademarks are the property of their respective owners. nVent reserves the right to change specifications without notice.。
波兰企业与监管机构启动小堆磋商
核电厂核反应堆肢三正业与监冒机构后动小堆磋商【世界核新闻网站2〇2〇年1〇月29日报 道】波兰Synthos 绿色能源公司（SGE )近日与 波兰国家原子机构* PAA )就通用电气-日立核 能公司（GEH )的BWRX -300小型模块堆拟议建设项目展开讨论。
根据2000年《波兰核能法》，在提交建设 许可证申请之前，SGE 可要求国家原子能机构就核设施建设和运营所采用的组织和技术方案 提供一般性意见。
SGE 、富腾电力与热力公司(Fortom Power and Heat )、爱克斯龙电力公司 (Exelon Generation )和通用电气-日立共同编制了项目建议书。
通用电气-日立2019年10月与Synthos 集团签署协议，合作开展在波兰建设BWRX -300 的可行性研究-2020年10月初与SGE 签署战 略合作协议，将合作开发和部署BWRX -300。
BWRX -300是在通用电气-日立1520 MWe 的经济简化沸水堆（ESBWR )设计基础上开发 的一种300 MWe 小型模块堆。
Synthos 集团是波兰最大的私营工业集团， 其组建SGE 的目的是为该集团开发零排放电力技术。
(中核战略规划研究总院张焰伍浩松）加政府资助IMSR 小堆研发【世界核新闻网站2020年10月16日报 道】加拿大政府将为特里斯特尔能源公司(Terrestrial Energy)提供 2000 万加兀（1500 万美元）资助，帮助加速推进一体化熔盐堆设计 (IMSR )的商业化。
这笔基金将通过加拿大战略创新基金提供，用于帮助IMSR 通过加拿大核安全委员会(CNSC )的预许可设计评审。
评审分为四个阶 段，IMSR 是四种通过第一阶段评审的小堆设计 之一。
另外三种分别是超安全核公司（USNC )高温气冷堆MMR -5和MMR -10、先进反应堆概念公司（ARC )钠冷堆ARC -100以及霍尔台克 国际公司（Holtec International ) SMR -160。
周坚每日解读一天文图——星系NGC300的精确距离－周坚－广西柳州市周坚的量天博客－强国...
周坚每日解读一天文图——星系NGC300的精确距离－周坚－广西柳州市周坚的量天博客－强国...周坚每日解读一天文图应用《解析宇宙学》探索宇宙!每天发布一张基于《解析宇宙学》理论解读的反映我们迷人宇宙的不同影像或照片，重点给出影像或照片中天体的解析宇宙学参数。
2010年7月5日玉夫座旋涡星系星系NGC300玉夫座旋涡星系NGC 300中的三片区域，VLT/ISAAC对它们进行了深入的近红外J、K波段成像观测。
视场中一共包含了16颗造父变星，周期从6天到83天不等。
说明：位于玉夫星系群中的美丽邻近星系NGC 300，它以正面对着我们。
在1999年-2000年利用拉·西纳（La Silla）2.2米的ESO/MPC望远镜所做的大视场成像巡天之中，研究小组已经发现了超过一百颗造父变星，它们的脉动周期的分布在一个较广的范围内。
去年，研究小组公布了从这些V、I波段的光学图片中得到的NGC 300的距离。
该小组能够以空前的精度测量NGC 300的距离，总不确定性仅为3%左右。
天文学家们发现NGC 300位于613万光年以外。
（影像及说明摘自：天文科普网）现依据星系NGC300的目前最为精确的距离给出如下表所示的《星系NGC300的解析宇宙学参数表》共大家参考。
从星系NGC300的解析宇宙学参数表中我们可以清晰地知道星系NGC300的诸多信息。
比如表中给出了星系NGC300的绝对星等（V 波段）是-18.243等，由此就知道它比银河系暗2.357等，按照星等系统计算，它只是银河系亮度的0.114倍。
又比如表中给出了星系NGC300的真实视向速度是10.401km/s，但现行理论给出的视向速度是143.866km/s，这是现行理论把观测红移全部解释为多普勒红移的结果，诸不知在观测红移中不仅有天体相对观测者的相对运动产生的红移或蓝移，而且同时还有宇宙的系统红移，通常称之为宇宙学红移，要知道，宇宙学红移是系统性的红移，它严格遵循周坚红移定律，而多普勒红移是个体行为，它不存在系统性。
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arXiv:astro-ph/0509383v1 14 Sep 2005
1r Astronomie und Astrophysik, Abteilung Astronomie, Universit¨ at T¨ ubingen, Sand 1, 72076 T¨ ubingen, Germany Department of Physics, University of Warwick, Coventry, CV4 7AL, United Kingdom Institut f¨ ur Astrophysik und Extraterrestrische Forschung, Universit¨ at Bonn, Auf dem H¨ ugel 71, 53121 Bonn, Germany Isaac Newton Group of Telescopes, 38700 Santa Cruz de La Palma, Spain
December and 2001 January. A total of 163 sources were detected in the energy range of 0.3–6 keV. We report on the global properties of the sources detected inside the D25 optical disk, such as the hardness ratio and X-ray fluxes, and on the properties of their optical counterparts found in B, V, and R images from the 2.2 m MPG/ESO telescope. Furthermore, we cross-correlate the X-ray sources with SIMBAD, the USNO-A2.0 catalog, and radio catalogues.
(2001) also identified a highly variable supersoft source and other bright sources coincident with known supernova remnants (SNRs) and H regions. The luminosity of the residual X-ray emission, probably due to unresolved sources and genuine diffuse gas, has been estimated to LX = 1.2 × 1038 erg s−1 (Read & Pietsch 2001). More recently, NGC 300 was observed with XMM-Newton on 2000 December 26 during XMM-Newton ’s revolution 192 and 6 days later during revolution 195. Some previous results of these observations have been presented by Kendziorra et al. (2001) and Carpano et al. (2004). Data on the luminous supersoft X-ray source XMMU J005510.7−373855 in the center of NGC 300 were presented by Kong & Di Stefano (2003). In addition to these X-ray data, observations with the 2.2 m MPG/ESO telescope on La Silla were performed. Here, we use archival images in the broad band B, V, and R filters. In this paper we report a catalog of the NGC 300 X-ray point sources obtained with XMM-Newton data, as well as their optical counterparts. The aim of this work is to present a deeper broad-band catalogue of X-ray selected sources in NGC 300 to facilitate further population studies and searches for counterparts in other wavebands. Detailed studies of selected X-ray sources will be presented elsewhere (Carpano et al., in preparation). The remainder of this work is organized as follows. Sect. 2 describes the observations and data reduction of the X-ray and optical data. In Sect. 3 we describe some global properties of the X-ray point sources detected inside the D25 optical disk as well as of NGC 300’s central diffuse region. The analysis of the optical counterparts of the X-ray sources is
Submitted: 13 October 2004; Accepted: 14 July 2005
Abstract. We present X-ray properties of NGC 300 point sources, extracted from 66 ksec of XMM-Newton data taken in 2000
Astronomy & Astrophysics manuscript no. 2162 (DOI: will be inserted by hand later)
February 5, 2008
X-ray properties of NGC 300⋆.
I. Global properties of X-ray point sources and their optical counterparts
Send offprint requests to: S. Carpano, e-mail: carpano@astro.unituebingen.de ⋆ Tables 1 and 2 are also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/
2
S. Carpano et al.: X-ray properties of NGC 300, I.
presented in Sect. 4. Tables of the X-ray and optical properties are given in Sect. 5. We discuss our results in Sect. 6.
Key words. Galaxies: individual: NGC 300 – X-rays: galaxies
1. Introduction
Studies of the X-ray population of spiral galaxies other than our Galaxy are of importance especially for the understanding of the formation of X-ray binaries and other X-ray emitting sources. NGC 300 is a member of the Sculptor galaxy group. Due to its small distance (∼2.02 Mpc; Freedman et al. 2001), the SA(s)d dwarf galaxy NGC 300 is an ideal target for the study of the entire X-ray population of a typical normal quiescent spiral galaxy. The major axes of the D25 optical disk are 13.3 kpc and 9.4 kpc (22′ × 15′ ; de Vaucouleurs et al. 1991). These studies are even more simplified by the galaxy’s almost face-on orientation and its low Galactic column density (NH = 3.6 × 1020 cm−2 ; Dickey & Lockman 1990). The first X-ray population study of NGC 300 was performed between 1991 and 1997 with a total of five ROSAT pointings (Read & Pietsch 2001). The total exposure time of these data was 46 ksec in the ROSAT Position Sensitive Proportional Counter and 40 ksec in the ROSAT High Resolution Imager, all with a nominal pointing position of αJ2000.0 = 00h 54m 52s.0 and δJ2000.0 = −37◦41′ 24′′ . 0. In these observations, a total of 29 sources was discovered within the D25 disk, the brightest being a black hole candidate with LX = 2.2×1038 erg s−1 in the 0.1–2.4 keV band. Read & Pietsch