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1.
In Paper I we compared the surface density of QSOs in the Bright Quasar Survey (BQS) and in the First Byurakan Survey (FBS) and concluded that the completeness of the BQS is of the order of 70% rather than 30-50% as suggested by several authors. A number of new observations recently became available, allowing a reevaluation of this completeness. We now obtain a surface density of QSOs brighter than B = 16.16 in a subarea of the FBS covering 2250 deg2, equal to 0.012 deg-2 (26 QSOs), implying a completeness of 53 ± 10%.  相似文献   

2.
The Australian SKA Pathfinder (ASKAP) is a new radio-telescope being built in Western Australia. One of the key surveys for which it is being built is EMU (Evolutionary Map of the Universe), which will make a deep (∼10 μJy/bm rms) radio continuum survey covering the entire sky as far North as +30°. EMU may be compared to the NRAO VLA Sky Survey (NVSS), except that it will have about 45 times the sensitivity, and five times the resolution. EMU will also have much better sensitivity to diffuse emission than previous large surveys, and is expected to produce a large catalogue of relics, tailed galaxies, and halos, and will increase the number of known clusters by a significant factor. Here we describe the EMU project and its impact on the astrophysics of clusters.  相似文献   

3.
We present a method for the photometric selection of candidate quasars in multiband surveys. The method makes use of a priori knowledge derived from a subsample of spectroscopic confirmed quasi-stellar objects (QSOs) to map the parameter space. The disentanglement of QSOs candidates and stars is performed in the colour space through the combined use of two algorithms, the probabilistic principal surfaces and the negative entropy clustering, which are for the first time used in an astronomical context. Both methods have been implemented in the voneural package on the Astrogrid Virtual Observatory platform. Even though they belong to the class of the unsupervised clustering tools, the performances of the method are optimized by using the available sample of confirmed quasars and it is therefore possible to learn from any improvement in the available 'base of knowledge'. The method has been applied and tested on both optical and optical plus near-infrared data extracted from the visible Sloan Digital Sky Survey (SDSS) and infrared United Kingdom Infrared Deep Sky Survey-Large Area Survey public data bases. In all cases, the experiments lead to high values of both efficiency and completeness, comparable if not better than the methods already known in the literature. A catalogue of optical candidate QSOs extracted from the SDSS Data Release 7 Legacy photometric data set has been produced and is publicly available at the URL http://voneural.na.infn.it/qso.html .  相似文献   

4.
The colours of high-redshift Type II quasi-stellar objects (QSOs) are synthesized from observations of moderate-redshift systems. It is shown that Type II QSOs are comparable to starbursts at matching the colours of z 850-dropouts and i 775-drops in the Hubble UltraDeep Field , and more naturally account for the bluest objects detected. Type II QSOs may also account for some of the i 775-drops detected in the Great Observatories Origins Deep Survey (GOODS) fields. It is shown that by combining imaging data from the Hubble Space Telescope and the James Webb Space Telescope , it will be possible to clearly separate Type II QSOs from Type I QSOs and starbursts based on their colours. Similarly, it is shown that the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) ZYJ filters may be used to discriminate high-redshift Type II QSOs from other objects. If Type II QSOs are prevalent at high redshifts, then active galactic nuclei (AGNs) may be major contributors to the re-ionization of the intergalactic medium.  相似文献   

5.
The 2MASS observation of the infrared quasars (IR QSOs) known so far is presented in this paper. Compared with the optical selected quasars, infrared quasars are more dust-enshrouded and have redder colors and steeper spectral indices in the near infrared. In consequence, they are much younger than the optical selected quasars. The result may be helpful to the suggestion that the evolution links could be the ULIRGs - > the IR QSOs - > the optical selected quasars. This publication makes use of data products from the Two Micron All Sky Survey (2MASS), which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center, funded by the National Aeronautics and Space Administration and the National Science Foundation of the United States.  相似文献   

6.
A systematic search for disclike edge-on-galaxies with a diameter larger than a = 40 arcsec and a major-to-minor axis ratio a/b ≥ 7 has been carried out by means of the Palomar Observatory Sky Survey and the ESO/SERC survey. As a result, we present a new catalogue of flat galaxies (FGC) containing 4455 objects and covering about 56% of the whole sky for the first time. The catalogue is assigned to study large-scale cosmic streamings and other problems of observational cosmology.  相似文献   

7.
The optical identification programme is presented for a complete sample of 867 radio sources that were observed with the Very Large Array (VLA) within 4.22 deg2 to S 1.4 GHz ≥ 0.135 mJy (5 σ). The area covered by the VLA survey is part of the regions of the sky that have been surveyed in the mid and far Infrared over the wavelength range 6.7–175 μmwith ISO as part of the European Large Area ISO Survey (ELAIS). Optical identifications are made using the Automatic Plate-measuring Machine (APM) optical catalogue in E (∼ R) and O (∼ B) bands with approximate limiting magnitudes of ∼ 20.0 and 21.5 mag, respectively. For 220 out of the 867 radio sources, likely identifications are proposed with an a posteriori identification percentage of 25%. The sample of identification has a reliability of 96% and a completeness of 80%. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

8.
We simulated both the matter and light (galaxy) distributions in a wedge of the Universe and calculated the gravitational lensing magnification caused by the mass along the line-of-sight of galaxies and galaxy groups identified in sky surveys. A large volume redshift cone containing cold dark matter particles mimics the expected cosmological matter distribution in a flat universe with low matter density and a cosmological constant. We generate a mock galaxy catalogue from the matter distribution and identify thousands of galaxy groups in the luminous sky projection. We calculate the expected magnification around galaxies and galaxy groups and then the induced quasi-stellar object (QSO)–lens angular correlation due to magnification bias. This correlation is observable and can be used both to estimate the average mass of the lens population and to make cosmological inferences. We also use analytical calculations and various analyses to compare the observational results with theoretical expectations for the cross-correlation between faint QSOs from the 2dF Survey and nearby galaxies and groups from the Automated Plate Measurement and Sloan Digital Sky Survey Early Data Release. The observed QSO–lens anticorrelations are stronger than the predictions for the cosmological model used. This suggests that there could be unknown systematic errors in the observations and data reduction, or that the model used is not adequate. If the observed signal is assumed to be solely due to gravitational lensing, then the lensing is stronger than expected, due to more massive galactic structures or more efficient lensing than simulated.  相似文献   

9.
We describe technical aspects of an astrometric and photometric survey of the North Celestial Cap (NCC), from the Pole (δ=90°) to δ=80°, in support of the TAUVEX mission. This region, at galactic latitudes from ∼17° to ∼37°, has poor coverage in modern CCD-based surveys. The observations are performed with the Wise Observatory one-meter reflector and with a new mosaic CCD camera (LAIWO) that images in the Johnson–Cousins R and I bands a one-square-degree field with sub-arcsec pixels. The images are treated using IRAF and SExtractor to produce a final catalogue of sources. The astrometry, based on the USNO-A2.0 catalogue, is good to ∼1 arcsec and the photometry is good to ∼0.1 mag for point sources brighter than R=20.0 or I=19.1 mag. The limiting magnitudes of the survey, defined at photometric errors smaller than 0.15 mag, are 20.6 mag (R) and 19.6 (I). We separate stars from non-stellar objects based on the object shapes in the R and I bands, attempting to reproduce the SDSS star/galaxy dichotomy. The completeness test indicates that the catalogue is complete to the limiting magnitudes.  相似文献   

10.
Part five of optically identified point sources from the IRAS Point Source Catalog (PSC) contains data on 19 late-type stars. The identifications were based on the Digitized Sky Survey (DSS), the First Byurakan Survey (FBS), blue and red maps of the Palomar survey (POSS), and infrared fluxes at 12, 25, 60, and 100 mm in the region of +61° ≤ δ ≤ +65° and 05 h 30 m ≤ α ≤ 18 h 35 m with an area of 357 sq. deg. Of the 76 objects given in the IRAS PSC as unidentified sources of infrared radiation, 51 are associated with known stars in existing catalogs, 6 are objects from the FBS of late-type stars, and 19 sources remained unknown in the optical range. For the identified stars we determined the optical coordinates, their departures from the IR coordinates, the Vstellar magnitudes, the color indices CI,and the preliminary spectral subtypes. The objects have optical magnitudes in the range of 8 m −16 m .Gas-dust shells are assumed to exist around four of the sources. Finder charts from the DSS are given for 19 of the objects. Translated from Astrofizika, Vol. 42, No. 1, pp. 53–59, January–March, 1999.  相似文献   

11.
We present the final spectroscopic QSO catalogue from the 2dF-SDSS LRG (luminous red galaxy) and QSO (2SLAQ) survey. This is a deep,  18 < g < 21.85  (extinction corrected), sample aimed at probing in detail the faint end of the broad line active galactic nuclei luminosity distribution at   z ≲ 2.6  . The candidate QSOs were selected from SDSS photometry and observed spectroscopically with the 2dF spectrograph on the Anglo-Australian Telescope. This sample covers an area of 191.9 deg2 and contains new spectra of 16 326 objects, of which 8764 are QSOs and 7623 are newly discovered [the remainder were previously identified by the 2dF QSO Redshift Survey (2QZ) and SDSS]. The full QSO sample (including objects previously observed in the SDSS and 2QZ surveys) contains 12 702 QSOs. The new 2SLAQ spectroscopic data set also contains 2343 Galactic stars, including 362 white dwarfs, and 2924 narrow emission-line galaxies with a median redshift of   z = 0.22  .
We present detailed completeness estimates for the survey, based on modelling of QSO colours, including host-galaxy contributions. This calculation shows that at   g ≃ 21.85  QSO colours are significantly affected by the presence of a host galaxy up to redshift   z ∼ 1  in the SDSS ugriz bands. In particular, we see a significant reddening of the objects in   g − i   towards the fainter g -band magnitudes. This reddening is consistent with the QSO host galaxies being dominated by a stellar population of age at least 2–3 Gyr.
The full catalogue, including completeness estimates, is available on-line at http://www.2slaq.info/ .  相似文献   

12.
A sample of 2712 radio-luminous galaxies is defined from the second data release of the Sloan Digital Sky Survey (SDSS) by cross-comparing the main spectroscopic galaxy sample with two radio surveys: the National Radio Astronomy Observatories (NRAO) Very Large Array (VLA) Sky Survey (NVSS) and the Faint Images of the Radio Sky at Twenty centimeters (FIRST) survey. The comparison is carried out in a multistage process and makes optimal use of both radio surveys by exploiting the sensitivity of the NVSS to extended and multicomponent radio sources in addition to the high angular resolution of the FIRST images. A radio source sample with 95 per cent completeness and 98.9 per cent reliability is achieved, far better than would be possible for this sample if only one of the surveys was used. The radio source sample is then divided into two classes: radio-loud active galactic nuclei (AGN) and galaxies in which the radio emission is dominated by star formation. The division is based on the location of a galaxy in the plane of 4000-Å break strength versus radio luminosity per unit stellar mass and provides a sample of 2215 radio-loud AGN and 497 star-forming galaxies brighter than 5 mJy at 1.4 GHz. A full catalogue of positions and radio properties is provided for these sources. The local radio luminosity function is then derived both for radio-loud AGN and for star-forming galaxies and is found to be in agreement with previous studies. By using the radio to far-infrared (FIR) correlation, the radio luminosity function of star-forming galaxies is also compared to the luminosity function derived in the FIR. It is found to agree well at high luminosities but less so at lower luminosities, confirming that the linearity of the radio to FIR correlation breaks down below about 1022 W Hz−1 at 1.4 GHz.  相似文献   

13.
A catalog of 995 C and late M type stars is compiled from the First Byurakan Survey of the sky (FBS). The question of effectively separating giants and dwarfs among the stars of spectral class M is examined using data from this catalog, the 2MASS survey, and a number of other catalogs. This has made it possible to determine the luminosity class of 846 class M stars from the FBS survey. In the sample of FBS late M stars, 187 are dwarfs and 659 are giants. The sample of FBS late M stars is compared statistically with the set of known samples of type M stars. The subsample of FBS M-giants is proved to be similar to Stephenson’s standard sample of M-giants. A detailed statistical analysis of these two samples is carried out. __________ Translated from Astrofizika, Vol. 50, No. 4, pp. 589–602 (November 2007).  相似文献   

14.
The results of the very-low frequency sky survey of discrete sources made with the UTR-2 radio telescope within the declination zone 41° to 52° are presented. The UTR-2 radio source catalogue contains the estimates of the coordinates and flux densities of 432 sources measured at a number of the lowest frequencies used in contemporary radio astronomy within the range from 10 at 25 MHz. The questions of establishing the UTR-2 sky survey sensitivity, completeness and reliability of the resulting catalogue are considered. The coordinates of the sources measured at very low frequencies have been compared with respective data obtained in the 4C survey at 178 MHz.  相似文献   

15.
The Effelsberg‐Bonn H I survey (EBHIS) comprises an all‐sky survey north of Dec = –5° of the Milky Way and the local volume out to a red‐shift of z ≃ 0.07. Using state of the art Field Programmable Gate Array (FPGA) spectrometers it is feasible to cover the 100 MHz bandwidth with 16.384 spectral channels. High speed storage of H I spectra allows us to minimize the degradation by Radio Frequency Interference (RFI) signals. Regular EBHIS survey observations started during the winter season 2008/2009 after extensive system evaluation and verification tests. Until today, we surveyed about 8000 square degrees, focusing during the first all‐sky coverage of the Sloan‐Digital Sky Survey (SDSS) area and the northern extension of the Magellanic stream. The first whole sky coverage will be finished in 2011. Already this first coverage will reach the same sensitivity level as the Parkes Milky Way (GASS) and extragalactic surveys (HIPASS). EBHIS data will be calibrated, stray‐radiation corrected and freely accessible for the scientific community via a webinterface. In this paper we demonstrate the scientific data quality and explore the expected harvest of this new all‐sky survey (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

16.
A third list of point sources from the IRAS Point Source Catalog (PSC), optically identified with late-type stars, is given. The list contains data on 34 objects. The identification was based on the Digitized Sky Survey (DSS), the First Byurakan Survey (FBS). blue and red maps of the Palomar Observatory Sky Survey, and infrared fluxes at wavelengths of 12, 25, 60, and 100 mm in the regions of +61° ≤ δ ≤ +65°, 06h45m ≤ α ≤ 17h28m and +69° ≤ δ ≤ +73°, 03h50m ≤ α ≤ 18h10m. Of 34 objects given in the IRAS PSC as unidentified sources of infrared radiation, 11 are associated with known stars in existing catalogs, 6 are objects from the FBS survey of late-type stars, and 17 sources remained unknown in the optical range, 3 of them also being sources in the IRAS Serendipitous Survey Catalog (SSC). The optical coordinates, their departures from the 1R coordinates, the V magnitudes, the color indices CI, and the preliminary spectral subtypes were determined. The objects have optical magnitudes in the range of 7h.6-13m.6. Finder charts from the DSS are given for 23 objects. Translated from Astrofizika, Vol. 43, No. 1, pp. 77-84, January–March, 2000.  相似文献   

17.
We present a catalogue of galaxy clusters detected in the Planck all-sky Compton parameter maps and identified using data from the WISE and SDSS surveys. The catalogue comprises about 3000 clusters in the SDSS fields. We expect the completeness of this catalogue to be high for clusters with masses larger than M 500 ≈ 3 × 1014 M ⊙, located at redshifts z < 0.7. At redshifts above z ≈ 0.4, the catalogue contains approximately an order of magnitude more clusters than the 2nd Planck Catalogue of Sunyaev-Zeldovich sources in the same fields of the sky. This catalogue can be used for identification of massive galaxy clusters in future large cluster surveys, such as the SRG/eROSITA all-sky X-ray survey.  相似文献   

18.
A fourth list of optically identified point sources from the IRAS Point Source Catalog, containing 34 nonstellar objects, is given. The identifications were made on the basis of the Digitized Sky Survey (DSS), the First Byurakan Survey, blue and red maps from the Palomar Sky Survey (FBS), and infrared fluxes at 12, 25, 60, and 100 μm in the region of +61° ≤ δ ≤ 65° and 11h15m ≤ α ≤ 18h35m with an area of 200 sq. deg. For the identified objects we determined their optical coordinates, their departures from the IR coordinates, their stellar V magnitudes, color indices CI, and preliminary types. The optical magnitudes of the objects are in the range 12m.5-27m. The identified galaxies include Seyfert candidates, interacting pairs, galaxies with companions, superassociations, etc. The galaxies are encountered in groups in many cases, and the IR emission may be due to heating of intergalactic matter within a group. Finder charts from the DDS are given for these objects. Translated from Astrofizika, Vol. 41, No. 3, pp. 359–366, July–September, 1998.  相似文献   

19.
The acquisition of H  i Parkes All Sky Survey (HIPASS) southern sky data commenced at the Australia Telescope National Facility's Parkes 64-m telescope in 1997 February, and was completed in 2000 March. HIPASS is the deepest H  i survey yet of the sky south of declination +2°, and is sensitive to emission out to 170 h75−1 Mpc. The characteristic root mean square noise in the survey images is 13.3 mJy. This paper describes the survey observations, which comprise 23 020 eight-degree scans of 9-min duration, and details the techniques used to calibrate and image the data. The processing algorithms are successfully designed to be statistically robust to the presence of interference signals, and are particular to imaging point (or nearly point) sources. Specifically, a major improvement in image quality is obtained by designing a median-gridding algorithm which uses the median estimator in place of the mean estimator.  相似文献   

20.
Precise pointing and stabilization of the T-170M telescope (World Space Observatory Ultraviolet, WSO-UV project) is provided by the Fine Guidance System (FGS) that uses a guide star catalogue (Master Catalogue). To verify the photometric system of the Master Catalogue we have carried out ground based observations with a CCD-camera in a spectral band, close to that of FGS. We have found, that the photometric quality of the Master Catalogue is sufficient for FGS operations. The mean photometric error in the range of 14–17 mag is ±0.23 mag; its variation over the sky does not exceed the factor of two. 2% of stars from the Master Catalogue have photometric errors higher than 2 mag. We have also found a correlation between large photometric errors and the Master Catalogue flags.  相似文献   

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