scholarly journals QSO Color Selection in the SDSS

1998 ◽  
Vol 179 ◽  
pp. 291-292
Author(s):  
H. J. Newberg ◽  
B. Yanny
Keyword(s):  
Critical Path ◽  
Color Space ◽  
Sloan Digital Sky Survey ◽  
Radio Sources ◽  
Color Selection ◽  
The North ◽  
Point Spread ◽  
Sky Survey ◽  
Spread Function ◽  
North Galactic

The Sloan Digital Sky Survey (SDSS) will image 10,000 square degrees in the north galactic cap in five filters. We hope to identify and obtain spectra for about 100,000 quasars brighter than 20th magnitude in this area. The selection will be primarily on the basis of point spread function and colors, but we will also identify quasars from a catalog of FIRST radio sources. The selection areas in color space must be determined during the testing period prior to the official start of the survey. This task may determine the length of the test period. In anticipation of this becoming the critical path, we have written a body of software that will allow us to quickly analyze a set of multicolor data and make a first cut at the selection limits.

scholarly journals The Extremely Luminous Quasar Survey in the Sloan Digital Sky Survey Footprint. II. The North Galactic Cap Sample

2018 ◽  
Vol 863 (2) ◽  
pp. 144 ◽  
Author(s):  
Jan-Torge Schindler ◽  
Xiaohui Fan ◽  
Ian D. McGreer ◽  
Jinyi Yang ◽  
Feige Wang ◽  
...  
Keyword(s):  
Sloan Digital Sky Survey ◽  
The North ◽  
Sky Survey ◽  
North Galactic

scholarly journals Point-Spread Function (PSF) Photometric Analysis of Open Clusters: Melotte 72 & NGC 2158

2015 ◽  
Vol 12 (4) ◽  
Author(s):  
Muhammad Mirza ◽  
Zain Rahim
Keyword(s):  
Point Spread Function ◽  
Stellar System ◽  
Open Clusters ◽  
Sloan Digital Sky Survey ◽  
Physical Parameters ◽  
Open Star Clusters ◽  
Open Star ◽  
Point Spread ◽  
Sky Survey ◽  
Spread Function

Point Spread Function (PSF) photometry of open star clusters Melotte 72 and NGC 2158 was performed using g and r band data from the Sloan digital Sky Survey (SDSS) Data Release 7. Instrumental magnitudes of stars in both bands were transformed into calibrated magnitudes using standard equation. Color-Magnitude (CM) diagrams were produced and compared with the SDSS isochrones for AB stellar system for different ages and/or metallicities. The objective of this study was to determine the physical parameters (age, distance, metallicity, reddening) of open clusters from CM diagrams. The best fit isochrones were used to estimate cluster parameters. The observed parameters were then compared with the WEBDA data base. KEYWORDS: PSF Photometry, Melotte 72, SDSS, NGC 2158, Isochrone Fitting, IRAF

scholarly journals Identification of a Complete Sample of Northern Rosat All-Sky Survey X-Ray Sources

1998 ◽  
Vol 179 ◽  
pp. 449-449
Author(s):  
J. Krautter ◽  
I. Thiering ◽  
F.-J Zickgraf ◽  
I. Appenzeller ◽  
R. Kneer ◽  
...  
Keyword(s):  
Optical Observations ◽  
Limited Sample ◽  
Ccd Imaging ◽  
X Ray ◽  
The North ◽  
Cluster Of Galaxies ◽  
Faint Object ◽  
Sky Survey ◽  
Faint Object Spectrograph ◽  
North Galactic

We present results of the optical identification of a spatially complete, flux limited sample of about 700 ROSAT All-Sky X-ray sources contained in 6 study areas north of δ = −9° with |bII|> 20° (including one region near the North Galactic pole (NGP), another one near the North Ecliptic pole (NEP)). Countrate limits are 0.01 cts s–1 near the NEP and 0.03 cts s–1 for the other areas. The optical observations were performed at the 2.15-m telescope of the Guillermo Haro Observatory, Mexico, using the Landessterwarte Faint Object Spectrograph Camera which allows to carry out direct CCD imaging and multi-object spectroscopy. The limiting magnitude is about 19m for spectroscopy and about 23m for B and R direct imaging. Our analysis shows a dependency of the ratio of ‘extragalactic’ (e.g., AGN, cluster of galaxies) to ‘stellar’ (e.g., coronal emitters, active binaries) counterparts on NH. In the area near the NGP (low NH) ‘extragalactic’ counterparts dominate, while in the area with the highest NH ‘stellar’ counterparts dominate.

scholarly journals The Performance of Neural Networks in Astronomical Image Classification

1994 ◽  
Vol 161 ◽  
pp. 235-241
Author(s):  
S.C. Odewahn
Keyword(s):  
Neural Network ◽  
Image Classification ◽  
Sky Surveys ◽  
Pattern Recognition Techniques ◽  
The North ◽  
Astronomical Image ◽  
Sky Survey ◽  
Network Pattern ◽  
North Galactic

The use of neural network pattern recognition techniques in the field of astronomy is reviewed. In assessing the quality of image recognition derived from this method particular attention is given to the problem of star/galaxy discrimination in large digital sky surveys. A two color survey of 9 fields of the first epoch Palomar Sky Survey, centered on the North Galactic Pole, has been performed with the Minnesota Automated Plate Scanner. A set of neural network image classifiers are used to automatically perform star/galaxy discrimination. We assess the efficiency of image classification and sample completeness through comparisons with a variety of independent studies of the NGP area.

scholarly journals First Results from the VLA FIRST Survey

1996 ◽  
Vol 175 ◽  
pp. 499-502
Author(s):  
R.H. Becker ◽  
M.D. Gregg ◽  
D.J. Helfand ◽  
C.M. Cress ◽  
R. Mcmahon ◽  
...  
Keyword(s):  
Correlation Function ◽  
Radio Sources ◽  
Optical Identification ◽  
X Ray ◽  
The North ◽  
First Results ◽  
Angular Correlation Function ◽  
Second Year ◽  
North Galactic ◽  
Followup Studies

The VLA FIRST survey is now in its second year. We have completed mapping over 1500 deg2 of the North Galactic Cap and present here the catalog of the 138,000 radio sources detected therein. We discuss the statistics of this new catalog including the two-point angular correlation function for all radio emitters, present our optical identification of 24,000 sources using the APM catalog, and report followup studies on radio variability, X-ray source identification, and our bright quasar sample.

scholarly journals A VO study of SDSS AGNs with X-ray emission from ROSAT-PSPC pointed observations

2006 ◽  
Vol 2 (14) ◽  
pp. 581-581
Author(s):  
Robert J. Hanisch ◽  
Anatoly A. Suchkov ◽  
Timothy M. Heckman ◽  
Wolfgang H. Voges
Keyword(s):  
Survey Data ◽  
Sloan Digital Sky Survey ◽  
Radio Sources ◽  
X Ray ◽  
Sky Survey ◽  
Data Release

We use VO facilities to study AGNs with X-ray emission. We present a sample of 1744 of Type 1 AGNs from the Sloan Digital Sky Survey Data Release 4 (SDSS DR4) spectroscopic catalog with X-ray counterparts in the White-Giommi-Angelini catalogue (WGACAT) of ROSAT-pspc pointed observations. Of 1744 X-ray sources, 1410 (80.9%) are new AGN identifications. Of 4,574 SDSS DR4 AGNs for which we found radio matches in the catalogue of radio sources from the Faint Images of the Radio Sky at Twenty (FIRST) cm survey, 224 turned up in our sample of SDSS X-ray AGN.

Comparison of the distributions of galactic y-radiation and radio synchrotron radiation

1981 ◽  
Vol 301 (1462) ◽  
pp. 573-575 ◽  
Keyword(s):  
Radio Emission ◽  
Full Width Half Maximum ◽  
Detailed Comparison ◽  
Full Width ◽  
Half Maximum ◽  
Brightness Temperatures ◽  
Point Spread ◽  
Sky Survey ◽  
Spread Function ◽  
Continuum Radio

We have used the new all-sky survey of continuum radio emission at 408 MHz of Haslam et al. (1981 a, b ) to compare the distribution of radio emission in a band along the galactic equator for [ b ] < 20° with the COS-B y-ray distribution of Mayer-Hasselwander et al. (1980). The radio survey has resolution with full width half-maximum (f.w.h.m.) of 51 arc min and the data are brightness temperatures at 20' intervals in galactic coordinates. Such comparisons have been made before (see, for example, Jakel et al. 1975; Paul et al. 1976; Higdon 1979) with earlier y-ray data but this is the first in which the radio data have been in a form allowing a detailed comparison after convolution with the point spread function of the y-ray detector.

scholarly journals An Updated Multi-Wavelength Radio and Optical Catalog of Quasars and Radio Galaxies

2013 ◽  
Vol 9 (S304) ◽  
pp. 238-239 ◽  
Author(s):  
Amy E. Kimball ◽  
Željko Ivezić
Keyword(s):  
Spectral Index ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Large Area ◽  
Sky Surveys ◽  
The North ◽  
Multi Wavelength ◽  
Optical Surveys ◽  
Quasars And Radio Galaxies ◽  
North Galactic

AbstractWe present a catalog of millions of radio sources, created by consolidating large-area radio and optical surveys GB6 (6cm), FIRST (20cm), NVSS (20cm), WENSS (92cm), VLSS (4m), and SDSS DR9 (optical). The region where all surveys overlap covers 3269 deg2 in the North Galactic Cap, and contains >160,000 20-cm sources, with about 12,000 detected in all five radio surveys and over one-third detected optically. Combining parameters from the sky surveys allows easy and efficient classification by radio and optical morphology and radio spectral index. The catalog is available at http://www.atnf.csiro.au/people/Amy.Kimball/radiocat.shtml.

scholarly journals The In-orbit Performance of SEVIRI From Observations of Mercury and Venus

2021 ◽  
Author(s):  
Martin Burgdorf ◽  
Stefan Buehler ◽  
Viju John ◽  
Thomas Müller
Keyword(s):  
Finite Impulse Response ◽  
Field Of View ◽  
Promising Alternative ◽  
Narrow Channels ◽  
Vicarious Calibration ◽  
The North ◽  
Point Spread ◽  
Spread Function ◽  
The Stability ◽  
Calibration Coefficients

<p>We investigated various aspects of the in-orbit performance of SEVIRI on Meteosat-10 (launch: 05 Jul 2012) and -11 (launch: 15 Jul 2015) with images, where Mercury or Venus appeared in a corner. These objects are of similar or smaller size than the instantaneous field of view, and therefore they are well suited for checks of geometric requirements. From comparing the position of Venus in different channels we conclude that the North-South distance between the two focal planes is shorter than the nominal value by 0.66 km at SSP (Sub-Satellite Point) with Meteosat-10 and longer by 1.44 km at SSP with Meteosat-11. The tilt of the detector array against the equator is less than 0.0037° for SEVIRI on Metosat-10. The sampling with narrow channels is 3.0016 km, with a one-sigma uncertainty of 30 cm at sub-satellite point. The tests we carried out to check the geometric performance of the instrument confirmed that SEVIRI is compliant with the requirements. The Point Spread Function as determined from the image of a planet agrees well with the expectations based on its combination with the finite impulse response. Finally we determined the stability of the calibration coefficients from the counts obtained on the planetary targets and found the reproducibility of the measurements of planetary fluxes similar to those of vicarious calibration targets. Hence planets are a promising alternative to established methods of in-flight characterisation and validation of imagers.</p>

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