scholarly journals Synthetic data products for future H i galaxy surveys: a tool for characterizing source confusion in spectral line stacking experiments

2016 ◽  
Vol 460 (4) ◽  
pp. 4366-4381 ◽  
Author(s):  
E. C. Elson ◽  
S. L. Blyth ◽  
A. J. Baker
Keyword(s):  
Spectral Line ◽  
Synthetic Data ◽  
Galaxy Surveys ◽  
Data Products ◽  
Source Confusion

scholarly journals Computing three-point correlation function randoms counts without the randoms catalogue

2019 ◽  
Vol 486 (1) ◽  
pp. L105-L109 ◽  
Author(s):  
David W Pearson ◽  
Lado Samushia
Keyword(s):  
Cosmological Parameters ◽  
Synthetic Data ◽  
Function Estimation ◽  
Point Function ◽  
Simple Method ◽  
Galaxy Surveys ◽  
Counting Algorithms ◽  
Data Points ◽  
Point Correlation ◽  
Point Correlation Function

ABSTRACT As we move towards future galaxy surveys, the three-point statistics will be increasingly leveraged to enhance the constraining power of the data on cosmological parameters. An essential part of the three-point function estimation is performing triplet counts of synthetic data points in random catalogues. Since triplet counting algorithms scale at best as $\mathcal {O}(N^2\log N)$ with the number of particles and the random catalogues are typically at least 50 times denser than the data; this tends to be by far the most time-consuming part of the measurements. Here, we present a simple method of computing the necessary triplet counts involving uniform random distributions through simple one-dimensional integrals. The method speeds up the computation of the three-point function by orders of magnitude, eliminating the need for random catalogues, with the simultaneous pair and triplet counting of the data points alone being sufficient.

scholarly journals Contrast sensitivities in the Gaia Data Release 2

2019 ◽  
Vol 621 ◽  
pp. A86 ◽  
Author(s):  
Alexis Brandeker ◽  
Gianni Cataldi
Keyword(s):  
Contrast Sensitivity ◽  
Angular Separation ◽  
Detection Sensitivity ◽  
Source Detection ◽  
Source Density ◽  
Data Release ◽  
Data Products ◽  
Source Confusion ◽  
Photometric Monitoring ◽  
Bright Source

The source detection sensitivity of Gaia is reduced near sources. To characterise this contrast sensitivity is important for understanding the completeness of the Gaia data products, in particular when evaluating source confusion in lower resolution surveys such as photometric monitoring for transits. Here, we statistically evaluate the catalogue source density to determine the Gaia Data Release 2 source detection sensitivity as a function of angular separation and brightness ratio from a bright source. The contrast sensitivity from ∼0.4″ out to 12″ ranges in ΔG = 0–14 mag. We find the derived contrast sensitivity to be robust with respect to target brightness, colour, source density, and Gaia scan coverage.

scholarly journals Archival of Radio Source Catalogues: Present Status and Prospects

1992 ◽  
Vol 9 ◽  
pp. 731-733
Author(s):  
Heinz Andernach
Keyword(s):  
Spectral Line ◽  
Radio Source ◽  
Data Base ◽  
Present Status ◽  
Source Data ◽  
Data Products

AbstractRecent proliferation of large radioastronomical source surveys and resulting data products are reviewed, and attention is drawn to their poor archival status. First practical steps are proposed to establish a radio source data base from published source catalogues, proceeding with time from the bigger and recent ones to the smaller and older ones. At later stages the data base could assimilate unpublished data, spectral-line data and also images.

scholarly journals Overview on Spectral Line Source Finding and Visualisation

2012 ◽  
Vol 29 (3) ◽  
pp. 359-370 ◽  
Author(s):  
B. S. Koribalski
Keyword(s):  
Spectral Line ◽  
Galaxy Formation ◽  
Line Source ◽  
Large Scale ◽  
Cosmological Parameters ◽  
Large Data ◽  
Sky Survey ◽  
Source Confusion ◽  
Extragalactic Surveys ◽  
One Year

AbstractHere I will outline successes and challenges for finding spectral line sources in large data cubes that are dominated by noise. This is a 3D challenge as the sources we wish to catalog are spread over several spatial pixels and spectral channels. While 2D searches can be applied, e.g. channel by channel, optimal searches take into account the 3-dimensional nature of the sources. In this overview I will focus on Hi 21-cm spectral line source detection in extragalactic surveys, in particular HIPASS, the Hi Parkes All-Sky Survey and WALLABY, the ASKAP Hi All-Sky Survey. I use the original HIPASS data to highlight the diversity of spectral signatures of galaxies and gaseous clouds, both in emission and absorption. Among others, I report the discovery of a 680 km s−1 wide Hi absorption trough in the megamaser galaxy NGC 5793. Issues such as source confusion and baseline ripples, typically encountered in single-dish Hi surveys, are much reduced in interferometric Hi surveys. Several large Hi emission and absorption surveys are planned for the Australian Square Kilometre Array Pathfinder (ASKAP): here we focus on WALLABY, the 21-cm survey of the sky (δ < + 30°; z < 0.26) which will take about one year of observing time with ASKAP. Novel phased array feeds (‘radio cameras’) will provide 30 deg2 instantaneous field-of-view. WALLABY is expected to detect more than 500 000 galaxies, unveil their large-scale structures and cosmological parameters, detect their extended, low-surface-brightness disks as well as gas streams and filaments between galaxies. It is a precursor for future Hi surveys with SKA Phase I and II, exploring galaxy formation and evolution. The compilation of highly reliable and complete source catalogs will require sophisticated source-finding algorithms as well as accurate source parametrisation.

On the Inhomogeneity of Chemical Composition over the Surface of 21 Per

1976 ◽  
Vol 32 ◽  
pp. 343-349
Author(s):  
Yu.V. Glagolevsky ◽  
K.I. Kozlova ◽  
V.S. Lebedev ◽  
N.S. Polosukhina
Keyword(s):  
Chemical Composition ◽  
Spectral Line ◽  
Variable Star ◽  
Radial Velocities ◽  
Crimean Astrophysical Observatory ◽  
Line Intensities ◽  
Magnetic Variable

SummaryThe magnetic variable star 21 Per has been studied from 4 and 8 Å/mm spectra obtained with the 2.6 - meter reflector of the Crimean Astrophysical Observatory. Spectral line intensities (Wλ) and radial velocities (Vr) have been measured.

Sign in / Sign up

Export Citation Format

Share Document