Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userVersion 1 of the Hubble Source Catalog
70
0
0.0
(
0
)
Authors
Bradley C. Whitmore
Ask ChatGPT about the research
No Arabic abstract
The Hubble Source Catalog is designed to help optimize science from the Hubble Space Telescope by combining the tens of thousands of visit-based source lists in the Hubble Legacy Archive into a single master catalog. Version 1 of the Hubble Source Catalog includes WFPC2, ACS/WFC, WFC3/UVIS, and WFC3/IR photometric data generated using SExtractor software to produce the individual source lists. The catalog includes roughly 80 million detections of 30 million objects involving 112 different detector/filter combinations, and about 160 thousand HST exposures. Source lists from Data Release 8 of the Hubble Legacy Archive are matched using an algorithm developed by Budavari & Lubow (2012). The mean photometric accuracy for the catalog as a whole is better than 0.10 mag, with relative accuracy as good as 0.02 mag in certain circumstances (e.g., bright isolated stars). The relative astrometric residuals are typically within 10 mas, with a value for the mode (i.e., most common value) of 2.3 mas. The absolute astrometric accuracy is better than $sim$0.1 arcsec for most sources, but can be much larger for a fraction of fields that could not be matched to the PanSTARRS, SDSS, or 2MASS reference systems. In this paper we describe the database design with emphasis on those aspects that enable the users to fully exploit the catalog while avoiding common misunderstandings and potential pitfalls. We provide usage examples to illustrate some of the science capabilities and data quality characteristics, and briefly discuss plans for future improvements to the Hubble Source Catalog.
rate research
Read More
The Hubble Catalog of Variables (HCV) is a 3 year ESA funded project that aims to develop a set of algorithms to identify variables among the sources included in the Hubble Source Catalog (HSC) and produce the HCV. We will process all HSC sources with more than a predefined number of measurements in a single filter/instrument combination and compute a range of lightcurve features to determine the variability status of each source. At the end of the project, the first release of the Hubble Catalog of Variables will be made available at the Mikulski Archive for Space Telescopes (MAST) and the ESA Science Archives. The variability detection pipeline will be implemented at the Space Telescope Science Institute (STScI) so that updat
The Hubble Catalog of Variables (HCV) project aims to identify the variable sources in the Hubble Source Catalog (HSC), which includes about 92 million objects with over 300 million measurements detected by the WFPC2, ACS and WFC3 cameras on board of the Hubble Space Telescope (HST), by using an automated pipeline containing a set of detection and validation algorithms. All the HSC sources with more than a predefined number of measurements in a single filter/instrument combination are pre-processed to correct systematic effect and to remove the bad measurements. The corrected data are used to compute a number of variability indexes to determine the variability status of each source. The final variable source catalog will contain variables stars, active galactic nuclei (AGNs), supernovae (SNs) or even new types of variables, reaching an unprecedented depth (V$leq$27 mag). At the end of the project, the first release of the HCV will be available at the Mikulski Archive for Space Telescopes (MAST) and the ESA Hubble Science Archives. The HCV pipeline will be deployed at the Space Telescope Science Institute (STScI) so that an updated HCV may be generated following future releases of HSC.
The Hubble Source Catalog (HSC) combines lists of sources detected on images obtained with the WFPC2, ACS and WFC3 instruments aboard the Hubble Space Telescope (HST) available in the Hubble Legacy Archive. The catalog contains time-domain information with about two million of its sources detected with the same instrument and filter in at least five HST visits. The Hubble Catalog of Variables (HCV) project aims to identify HSC sources showing significant brightness variations. A magnitude-dependent threshold in the median absolute deviation of photometric measurements (an outlier-resistant measure of lightcurve scatter) is adopted as the variability-detection statistic. It is supplemented with a cut in $chi_{rm red}^2$ that removes sources with large photometric errors. A pre-processing procedure involving bad image identification, outlier rejection and computation of local magnitude zero-point corrections is applied to HSC lightcurves before computing the variability detection statistic. About 52000 HSC sources are identified as candidate variables, among which 7800 show variability in more than one filter. Visual inspection suggests that $sim 70%$ of the candidates detected in multiple filters are true variables while the remaining $sim 30%$ are sources with aperture photometry corrupted by blending, imaging artifacts or image processing anomalies. The candidate variables have AB magnitudes in the range 15-27$^{m}$ with the median 22$^{m}$. Among them are the stars in our own and nearby galaxies as well as active galactic nuclei.
We aim to construct an exceptionally deep (V ~< 27) catalog of variable objects in selected Galactic and extragalactic fields visited multiple times by the Hubble Space Telescope (HST). While HST observations of some of these fields were searched for specific types of variables before (most notably, the extragalactic Cepheids), we attempt a systematic study of the population of variable objects of all types at the magnitude range not easily accessible with ground-based telescopes. The variability timescales that can be probed range from hours to years depending on how often a particular field has been visited. For source extraction and cross-matching of sources between visits we rely on the Hubble Source Catalog which includes 10^7 objects detected with WFPC2, ACS, and WFC3 HST instruments. The lightcurves extracted from the HSC are corrected for systematic effects by applying local zero-point corrections and are screened for bad measurements. For each lightcurve we compute variability indices sensitive to a broad range of variability types. The indices characterize the overall lightcurve scatter and smoothness. Candidate variables are selected as having variability index values significantly higher than expected for objects of similar brightness in the given set of observations. The Hubble Catalog of Variables will be released in 2018.
A new version of the Optical Characteristics of Astrometric Radio Sources (OCARS) catalog is presented. This compiled catalog includes radio sources observed in different VLBI programs and experiments that result in source position determination, their redshift, and photometry in the visible and near-infrared bands. A cross-identification table between the OCARS and other catalogs is also provided. The status of the catalog as of 2018 September 7 is described in this paper. The OCARS catalog currently contains 6432 sources, of which 3895 have redshift data and 5479 have photometric data. Compared with the previous version, the current version has been enriched with extended redshift and photometry information, and cross-identification with several catalogs in radio, optical, infrared, ultraviolet, X-ray, and gamma-ray bands. The OCARS catalog is updated every few weeks on average to incorporate new data that appear in the NASA/IPAC Extragalactic Database (NED), SIMBAD database, and in the literature.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
