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1.
The results of a complete UBV photometry in a field of 3.1 square degrees to the limiting magnitude B = 20.0 are given. The number of blue objects (with U — B ≤ — 0.4) per square degree brighter than magnitude B is given by the relation log N = (0.66 ± 0.08) (B — 18) — 0.04±0.07. The percentage of the blue objects is 2% of the total number of stars brighter than magnitude V = 19.5. It is not distinguished between WD and QSO.  相似文献   

2.
A new sample of local, active extragalactic objects has been compiled: a combined sample that is the sum of two samples, of Sy1 galaxies and of quasars from Markarian's survey and quasars from the Bright Quasar Survey. A log N(<B)-B relation is constructed for the new sample of active galaxies, limited to the apparent stellar magnitude B = 15 m .5. It can be represented by a straight line with a slope = 0.60 ± 0.06. It is a good extension, without a noticeable jog, of the analogous relationship for the Hamburg—ESO survey, which has a slope = 0.59 ± 0.04. The combined surface density of bright active galaxies and quasars down to B = 15 m .5 is 0.01 per square degree.  相似文献   

3.
Multicolour VRI photometry and astrometry of one Centaur and seven Edgeworth-Kuiper objects were obtained. One object, 1994 JQ1 may be as red as 5145 Pholus, the reddest minor planet previously known. The Centaur 1995 DW2 has more moderate colour indices, similar to main-belt asteroids. Seven R-magnitudes were obtained for 1994 JS, 1995 FB21, and 1995 GY7. No light variation above the expected noise is evident, apart from a few outliers. A total of 47 astrometric positions were obtained for the eight objects. The four nights of observations with the ESO New Technology Telescope covered 0.52 square degrees. Two previosuly unknown object, 1995 FB21 and 1995 GY7, were discovered. We estimate the density of Edgeworth-Kuiper objects brighter than R = 24 to 5.3 per square degree of sky near the ecliptic.  相似文献   

4.
We study a model of mergers affecting only the progenitors of present E/SO. We adopt the standard scenarios of star formation as prescribed by Guiderdoni & Rocca-Volmerange. The merging process is parametrized under the assumptions of(1) self-similarity of the Schechter MF and(2) mass conservation. Nine models are discussed. The predictions are compared with counts ofB J ,U +,F +,N + bands. E/SO mergers account for the excess of the faintest blue galaxies without causing excess in redder bands. However, as we no longer have enough mergers at brighter magnitudes, a plain E/SO merging model fits less tightly for the redshift and the colour distributions. Detection effect, a steeper slope of LF may be ways to improve. Our models predict acceptable merger frequencies atz = 0.5 although some models predict more interacting galaxies than observation atz = 0.  相似文献   

5.
A sample of ultraviolet excess objects in a 12.56 square degree field near α = 9h40m, δ = +50° (5C1-radio survey) is presented. In addition to starlike or and nearly starlike objects a sample of more diffuse ones is listed, presumably containing many Markarjan-type galaxies. UBV-photometry and first spectroscopic results are communicated; the number magnitude relation and the projected number-density of the objects are shortly discussed.  相似文献   

6.
The Edinburgh-Cape Blue Object Survey is a major survey to discover blue stellar objects brighter than B 18 in the southern sky. It is covering an area of sky of 10,000 square degrees with |b| > 30° and < 0°. The blue stellar objects are selected by automatic techniques from U and B pairs of UK Schmidt Telescope plates scanned with the COSMOS measuring machine. Follow-up photometry and spectroscopy are being obtained with the SAAO telescopes to classify objects brighter than B = 16.5. This paper describes the survey, the techniques used to extract the blue stellar objects, the photometric accuracy, the spectroscopic classification, and the completeness of the survey.  相似文献   

7.
The physical nature of 277 ultraviolet excess objects of the third Asiago field (22 square degrees, 15 ≦ mpg ≦ 18, U–B ≦≦ -0.2) is investigated on the basis of objective prism plates. Most of them are stars, 8% are quasar candidates and 7% compact galaxies. The proportions of different kinds of objects changes with the magnitude and U–B colour index. The surface density of quasars is estimated to be between 0.5 Q/sq. deg. and 1.0 Q/sq. deg. for the UVX A3 objects. The results of the A3 field (located in the Virgo cluster of galaxies) statistically agree with the ones of the A1 field, outside clusters of galaxies.  相似文献   

8.
We present spectroscopically confirmed quasars in the 25 sq. degrees A1-field to a limiting magnitude of mB = 18.0. Our estimate of the quasar density of 0.28 ± 0.11 objects per sq. degree based on the “complete” sample of A1-qusars is in agreement with the observed integral number-magnitude relation. However, we consider this value as still a lower limit of the quasar density in the A1-field due to the uncertainties during the colour based selection of objects, especially their brightness dependence, resulting in serious selection effects. Thus, the quasar density of the A1 survey may be underestimated up to 30% and does not contradict the recently estimated incompletness of the BQS survey.  相似文献   

9.
We present CCD VIC photometry in a field 1.9 − 1.3 square arcmin and positioned about 3 arcmin north-east of the centre of M82. More than 100 stars have been identified and measured above the photometric limits V = 23m.5, I = 22m. Most of the objects fainter than V ≈︁ 20m should be members of M82 as expected from the statistics of foreground stars. Starlike as well as 2–3 somewhat diffuse objects - candidates of globular clusters - preferentially occupy yellow colours in the colour-magnitude diagram; extreme blue and red objects are missing. The colour-magnitude diagram indicates continuing star formation in this part of the disk. The absence of blue stars is caused by reddening; no convincing explanation is found for the missing red supergiants. Young stars are distributed throughout the whole field, the youngest being concentrated in associations at the SW edge of the field. To cope with the very irregular background created by the galaxy' s main body and with the low contrast of many of the stars against this background, a modified photometric method is introduced in which the background is estimated using the intensities in a ring drawn very tightly around the star in the wings of the point spread function.  相似文献   

10.
New solar abundances have been derived for Li, Be and B. They are mainly based on high-resolution spectra obtained at the Jungfraujoch Scientific Station (Switzerland). For Li, the abundance results from a discussion of the photospheric and sunspot spectra. Our results, log N Li = 0.42, log N Be = 1.17 and log N B < 2.80 (in the log N H = 12.00 scale), are lower than the previously admitted abundances for these elements. The far UV spectrum ( < 3000 Å) has also been considered in each case. The meaning of our results is discussed from the point of view of the destruction of these elements during the evolution of the sun.This work has been sponsored in part by the Air Force Cambridge Research Laboratories, OAR, through the European Office of Aerospace Research, U.S.A.F., under Contract AF 61 (052)-955, and by the Comité National Belge de la Coopération Géophysique Internationale (C.N.B.C.G.I.).  相似文献   

11.
Identifications of 5CI radio sources with optical objects are given. The identification rates amount to 44 and 30 per cent up to the limiting magnitude of about 21m in R and B, respectively. The objects are to about equal parts galaxies, blue starlike objects, and “unclassified objects” (presumably mostly faint galaxies and less pronounced blue objects). For every proposed identification a reliability and for the identification samples the reliability and the completeness are given. Some inaccuracies in the use of a statistical method, proposed in a previous paper, have been removed; two additional means of statistical treatment have been applied to discuss the data.  相似文献   

12.
A study of four open clusters in the direction of the Galactic anticentre (l = 186°, b = +2°) is presented. In a field of 8.32 square degrees proper motions and B magnitudes for about 79 000 stars down to 19.5 were determined on Tautenburg Schmidt plates. For more than 15 500 of them U magnitudes down to 17.3 could be obtained. Additionally, OCA Schmidt plates were used to determine V, R magnitudes in a larger field of 24.45 square degrees for 271 000 stars down to V = 18.2. For stars brighter than V = 15.5 an accuracy of about 1.5 mas/yr has been estimated for proper motions. The rms errors of stellar magnitudes and colour indices are 0.09 – 0.12 mag. Several open clusters have been already known in this direction of the sky, e.g. NGC 2168 or M 35 (C 0605+243), NGC 2158 (C 0604+241) and IC 2157 (C 0601+240). Inspecting the plates and analysing the colour-magnitude diagrams and published data, we could identify an additional anonymous cluster C 0605+242 with a projection on the sky near the centre of M 35 but at a larger distance from the Sun. The cluster membership determination was carried out using information on spatial and proper motion distributions of stars in the field. The colour-magnitude diagrams were derived down to the limiting stellar magnitude. For each cluster the interstellar extinction Av, the diameters of the core and corona, the ages and spatial velocity components (V,W) relative to the LSR in the Y,Z – Galactic directions were determined. The distances to the clusters of 960 pc, 2 600 pc, 2 520 pc and 3 700 pc were obtained for M 35, IC 2157, C 0605+242 and NGC 2158. They show the loci of the clusters in the Local and Perseus spiral arms and at external border of Perseus arm, respectively.  相似文献   

13.
A study of four open clusters on Tautenburg Schmidt plates in the direction to the Galactic Centre (l = 17.0°, b = +0.8°) is presented. In a field of 8.95 square degrees proper motions and B, V magnitudes were determined for about 36 500 stars up to the limiting magnitudes B = 17m.9, V = 16m.8. For stars brighter than B = 16m an accuracy of about 3 mas/year has been estimated for proper motions. The rms errors of stellar magnitudes and (B—V) colours is about 0.1 mag. There are two open clusters already known in this sky area: Trumpler 32 (C 1814-133) and NGC 6611 (C 1816-138). By the inspection of the plates two additional anonymous clusters were identified near the double star ADS 11285 or BD −14°5014 (C 1819-146) and near the star BD −14°5016 (C 1820-146). The cluster membership determination was carried out using information on spatial and proper motion distributions of stars in the field. The colour-magnitude diagrams up to the limiting stellar magnitude were constructed. For each cluster interstellar extinction AV, diameters of the core and corona, ages and spatial velocity components (V, W) relative to the LSR in the Y, Z-galactic directions were derived. The distances to the clusters were obtained to 1720 pc, 2260 pc, 2130 pc and 2130 pc for Trumpler 32, NGC 6611, C 1819-146 and C 1820-146, respectively. All clusters are situated in the Sagittarius-Carina spiral arm. Their spatial location confirms the assumption that galactic spiral arms are close to logarithmic spirals with a characteristic angle of about 20 degrees.  相似文献   

14.
To form the Hubble diagram for quasi-stellar objects (QSOs),we have made use of the recently published data on X-ray fluxes of 159 QSOs observed from the Einstein Observatory. The scatter in the Hubble diagram and the lack of an obvious redshift-flux density correlation for these QSOs have been attributed to the observational selection effect that the intrinsically less luminous QSOs can be detected only in the nearby region of space. When the optical, radio and X-ray selection effects are removed, keeping only the intrinsically brighter sources, we obtain a sample of 16 QSOs having a small dispersion in X-ray luminosities (〈 logL x〉) = 46.12 ± 0.28), a statistically significant linear correlation between (logf x, logcz) pairs and a slopeA =-1.906 ± 0.061 of the linear regression oflog f x on logcz. This slope is consistent, at a confidence level of 95 per cent or greater, with the slope of-2.0 expected theoretically based on the assumption that the redshifts of QSOs are cosmological in nature.  相似文献   

15.
A structural study of the old globular cluster NGC 1806 in the LMC has been carried out by star counts onB- andV-ESO 3.6 m telescope plates with three different limiting magnitude levels. The star density distribution was obtained directly from the surface strip count function with the Plummer formalism and the generalized Schuster law according to Lohmann. This yields beside the central density the structural parametern and the characteristic length parameterR 0 for each individual colour and magnitude level.The results show that the blue stellar content of NGC 1806 — the horizontal branch stars — is more concentrated towards the cluster center than the red giant and subgiant objects. Also such a dynamical mass segregation is observed for the red giants compared with the subgiants.Based on observations collected at the European Southern Observatory, La Silla, Chile.  相似文献   

16.
Measurements of two Tautenburg plates were used for a comparison of the astrometric accuracy of the automatic measuring machines PAM and MAMA. From plate-to plate solutions a positional accuracy of about 1 μm was achieved for stars with 7 < B < 17 for MAMA and with 11 < B < 17 for APM measurements. A rapid decrease in positional accuracy of fainter stars is caused rather by random effects of the photographic emulsion. A magnitude equation between the plates was obtained to be less than 1 μm over the whole magnitude range. Systematic errors with a small period of 2 cm in the APM measurements as well as a non-orthogonality and systematic differences between the MAMA and APM coordinate grids were found. A procedure of classifying all real objects measured into stars, galaxies and merged objets is presented for the MAMA measurements and the results are compared with the routine APM classification. Except for merged objects the MAMA and APM classification show a very good agreement for stars brighter than B = 18.5.  相似文献   

17.
We have detected new HD absorption systems at high redshifts, z abs = 2.626 and z abs = 1.777, identified in the spectra of the quasars J0812+3208 and Q1331+170, respectively. Each of these systems consists of two subsystems. The HD column densities have been determined: log N HDA = 15.70 ± 0.07 for z A = 2.626443(2) and log N HDB = 12.98 ± 0.22 for z B = 2.626276(2) in the spectrum of J0812+3208 and log N HDC = 14.83 ± 0.15 for z C = 1.77637(2) and log N HDD = 14.61 ± 0.20 for z D = 1.77670(3) in the spectrum of Q1331+170. The measured HD/H2 ratio for three of these subsystems has been found to be considerably higher than its values typical of clouds in our Galaxy.We discuss the problem of determining the primordial deuterium abundance, which is most sensitive to the baryon density of the Universe Ωb. Using a well-known model for the chemistry of a molecular cloud, we have estimated the isotopic ratio D/H=HD/2H2 = (2.97 ± 0.55) × 10−5 and the corresponding baryon density Ωb h 2 = 0.0205−0.0020+0.0025. This value is in good agreement with Ωb h 2 = 0.0226−0.00060.0006 obtained by analyzing the cosmic microwave background radiation anisotropy. However, in high-redshift clouds, under conditions of low metallicity and low dust content, hydrogen may be incompletely molecularized even in the case of self-shielding. In this situation, the HD/2H2 ratio may not correspond to the actual D/H isotopic ratio. We have estimated the cloud molecularization dynamics and the influence of cosmological evolutionary effects on it.  相似文献   

18.
Photometry of more than 1000 bright stars of 20 associations and some fields in its vicinity is made, usingUBV plates taken with a 2-m Ritchey-Chrétien telescope of the National Observatory at the Bulgarian Academy of Sciences with limited magnitudes of about 20.6 inU andV, 21.6 inB. The colour-magnitudes of about 20.6 inU andV, 21.6 inB. The colour-magnitude and colour-colour diagrams of 12 associations and 8 fields are constructed and the brightest blue and red stars colour excesses, ages, and integrated luminosities of the associations are determined. The composite diagrams for all association and nonassociation measured stars are constructed too. Inside associations bright stars as well as non-stellar objects occur more often than outside. The brightest stars in S5 are withM v7 and do not differ considerably from the brightest ones in the spiral arm S4 of M31. Approximately the same are the absolute magnitudes of the brightest stars in our Galaxy and M33. A small difference between the brightest stars of the latter galaxy with those of M31 is possible because the stars in M33 are younger. This is in agreement with the concept that Sc galaxies (for example M33) are younger than Sb ones (for example M31). The same could be the reason for the smaller ratio of blue to red supergiants in M33 than in M31. The age estimations of the associations in S5 together with those in S4 in M31 show that they are older than the associations in M33 which is in agreement with the above mentioned concept.  相似文献   

19.
In an area of nearly 23.1 square degrees centered at α(1950) = 23h57m and δ(1950) = + 59δ48' magnitudes, colors, and spectral classes were determined for 1419 stars brighter than mpg = 13m.00. Star counts were made in this area for all objects brighter than mpg = mpv = 15m.5. Altogether 50585 stars were included in the pv counts. The original photographic data have been transformed to the B, V system. From star counts the ratio of total-to-selective extinction was derived to be R ≉ 4.0 ± 0.2. It depends on the distance to the stars under consideration as well as on the surface density of the objects inside the considered region. In einem Gebiet von annähernd 23.1 Quadratgrad mit den Mittelpunktskoordinaten α(1950) = 23h57m und δ(1950) = 59°48' werden für 1419 Sterne heller als mpg = 13m.00 Helligkeiten, Farben und Spektraltypen bestimmt. Sternzählungen in Helligkeitsintervallen mpg und mpv wurden für alle Objekte heller als mpg = mpv = 15m.5 durchgeführt. Für diese 50585 Sterne wurden die gemessenen photographischen und photovisuellen Helligkeiten in das B, V-System transformiert. Im Ergebnis dieser Sternzählungen wurde ein Wert von R ≉ 4.0 ± 0.2 abgeleitet. Er hängt sowohl von der Entfernung der betrachteten Objektgruppen als auch von der Flächendichte der Sterne innerhalb der Region ab.  相似文献   

20.
QSO objective prism survey was done for the field centered at 10h40m + 00°00. For the 348 objects selected, we present in this paper their positions,B J magnitudes, spectra, and finding charts. Based on the sample containing 163 QSO candidates with higher reliabilities (F 3), the surface density of QSO candidates withB J 20 is estimated to be about 4.5 per square degree.Work based on UKST plates.  相似文献   

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