scholarly journals Optimal Multiwavelength Source Detection: Experience Gained from the WISE Mission

2012 ◽  
Vol 29 (3) ◽  
pp. 269-275 ◽  
Author(s):  
K. A. Marsh ◽  
T. H. Jarrett
Keyword(s):  
Neutral Hydrogen ◽  
Point Sources ◽  
Detection Sensitivity ◽  
Source Spectrum ◽  
Source Detection ◽  
Imaging Data ◽  
Data Cubes ◽  
Hydrogen Emission ◽  
Chi Squared ◽  
Potential Benefits

AbstractWe discuss the optimal detection of point sources from multiwavelength imaging data using an approach, referred to as MDET, which requires no prior knowledge of the source spectrum. MDET may be regarded as a somewhat more general version of the so-called ‘chi-squared’ technique. We describe the theoretical basis of the technique, and show examples of its performance with four-channel infrared broadband imaging data from the WISE mission. We also discuss the potential benefits of applying it to the multifrequency data cubes of the ASKAP surveys, and suggest that it could increase the detection sensitivity of searches for neutral hydrogen emission at moderately high redshifts.

Interstellar Neutral Hydrogen Emission Profile Structure

2004 ◽  
Vol 127 (1) ◽  
pp. 394-407 ◽  
Author(s):  
Gerrit L. Verschuur
Keyword(s):  
Neutral Hydrogen ◽  
Emission Profile ◽  
Hydrogen Emission

scholarly journals Subtraction of Bright Point Sources from Synthesis Images of the Epoch of Reionization

2011 ◽  
Vol 28 (1) ◽  
pp. 46-57 ◽  
Author(s):  
B. Pindor ◽  
J. S. B. Wyithe ◽  
D. A. Mitchell ◽  
S. M. Ord ◽  
R. B. Wayth ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Dynamic Range ◽  
Low Frequency ◽  
Neutral Hydrogen ◽  
Galactic Nuclei ◽  
Point Sources ◽  
Field Of View ◽  
Bright Point ◽  
Line Of Sight ◽  
Diffuse Background

AbstractBright point sources associated with extragalactic active galactic nuclei and radio galaxies are an important foreground for low-frequency radio experiments aimed at detecting the redshifted 21-cm emission from neutral hydrogen during the epoch of reionization. The frequency dependence of the synthesized beam implies that the sidelobes of these sources will move across the field of view as a function of observing frequency, hence frustrating line-of-sight foreground subtraction techniques. We describe a method for subtracting these point sources from dirty maps produced by an instrument such as the MWA. This technique combines matched filters with an iterative centroiding scheme to locate and characterize point sources in the presence of a diffuse background. Simulations show that this technique can improve the dynamic range of epoch-of-reionization maps by 2—3 orders of magnitude.

scholarly journals Estimation of Contaminants for Direct Imaging of Exoplanets: Constraint on the Stellar Distribution Model with both NIR and Deep Imaging Data

2013 ◽  
Vol 8 (S299) ◽  
pp. 42-43
Author(s):  
Mihoko Konishi ◽  
Hiroshi Shibai ◽  
Taro Matsuo ◽  
Kodai Yamamoto ◽  
Jun Sudo ◽  
...  
Keyword(s):  
Point Sources ◽  
Distribution Model ◽  
Model Parameters ◽  
Imaging Data ◽  
Direct Imaging ◽  
Distribution Models ◽  
New Model ◽  
Deep Imaging

AbstractThere are faint contaminants near primary stars in the direct imaging of exoplanets. Our goal is to estimate statistically the ratio of exoplanets in the detected batch of point sources by calculating the fraction of contamination. In this study, we compared the detected number of stars with the number of contaminants predicted by our model. We found that the observed number of faint stars were fewer than the predicted results towards the Pleiades and GOODS-South field when the parameters of the conventional stellar distribution models were employed. We thus estimated new model parameters in correspondence to the results of the observations.

scholarly journals The Large Magellanic Cloud with the Cherenkov Telescope Array

2019 ◽  
Vol 209 ◽  
pp. 01021
Author(s):  
María Isabel Bernardos ◽  
María Benito ◽  
Fabio Iocco ◽  
Salvatore Mangano ◽  
Olga Sergijenko ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Region Of Interest ◽  
Cosmic Ray ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Point Sources ◽  
Detection Sensitivity ◽  
Telescope Array ◽  
Star Forming ◽  
Cherenkov Telescope

The Large Magellanic Cloud (LMC) is a spiral galaxy, satellite of the Milky way with a high star formation activity. It represents a unique laboratory for studying an extended and spatially resolved star-forming galaxy through gamma-ray observatories. Therefore, the LMC survey is one of the key science projects for the Cherenkov Telescope Array (CTA), the next-generation ground-based gamma-ray observatory. In this document we present the work performed over the last year by the CTA working group dedicated to the LMC, in order to offer a first characterization of the LMC at TeV energies. We have performed detectability forecasts based on the expected CTA performance for all sources in the region of interest of the LMC with known emission at GeV energies and above. Based on previous observations made by Fermi-LAT and H.E.S.S. we have characterized all point sources, extended sources and diffuse emission produced by cosmic-ray propagation, extrapolating their spectra to CTA energies. Finally, we have characterized the signal expected by different annihilation mechanisms of dark matter (DM) particles within the LMC, computing the detection sensitivity curve for this target in the cross-section-to-mass plane.

scholarly journals LSST and the Epoch of Reionization Experiments

2017 ◽  
Vol 12 (S333) ◽  
pp. 222-227
Author(s):  
Željko Ivezić
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Time Domain ◽  
Point Sources ◽  
Field Of View ◽  
Next Generation ◽  
Imaging Data ◽  
Primary Mirror ◽  
Scientific Investigations ◽  
Near Earth Asteroids

AbstractThe Large Synoptic Survey Telescope (LSST), a next generation astronomical survey, sited on Cerro Pachon in Chile, will provide an unprecedented amount of imaging data for studies of the faint optical sky. The LSST system includes an 8.4m (6.7m effective) primary mirror and a 3.2 Gigapixel camera with a 9.6 sq. deg. field of view. This system will enable about 10,000 sq. deg. of sky to be covered twice per night, every three to four nights on average, with typical 5-sigma depth for point sources ofr= 24.5 (AB). With over 800 observations in theugrizybands over a 10-year period, these data will enable coadded images reachingr= 27.5 (about 5 magnitudes deeper than SDSS) as well as studies of faint time-domain astronomy. The measured properties of newly discovered and known astrometric and photometric transients will be publicly reported within 60 sec after closing the shutter. The resulting hundreds of petabytes of imaging data for about 40 billion objects will be used for scientific investigations ranging from the properties of near-Earth asteroids to characterizations of dark matter and dark energy. For example, simulations estimate that LSST will discover about 1,000 quasars at redshifts exceeding 7; this sample will place tight constraints on the cosmic environment at the end of the reionization epoch. In addition to a brief introduction to LSST, I review the value of LSST data in support of epoch of reionization experiments and discuss how international participants can join LSST.

A deep search for 21 CM neutral hydrogen emission in the tightly bound globular cluster NGC 6388

1989 ◽  
Vol 97 ◽  
pp. 1708 ◽  
Author(s):  
David K. Lynch ◽  
Phillip F. Bowers ◽  
John B. Whiteoak
Keyword(s):  
Globular Cluster ◽  
Neutral Hydrogen ◽  
Hydrogen Emission

scholarly journals Extracting Point Source Spectra / Recovering Extended Object Spectra Using Richardson-Lucy Restoration

2003 ◽  
Vol 209 ◽  
pp. 412-412
Author(s):  
J. R. Walsh ◽  
L. B. Lucy
Keyword(s):  
Point Source ◽  
A Priori ◽  
Central Star ◽  
Spectral Element ◽  
Point Sources ◽  
Source Spectrum ◽  
Extended Source ◽  
Extended Object ◽  
Source Signal ◽  
Source Spectra

Long slit spectra of astronomical objects either contain point sources, characterized by a known Point Spread Function (PSF), which is often wavelength dependent, and extended sources, such as nebulae, whose spatial extent is not a priori known. The analysis of long slit spectra consists in separating the spectrum into either: the point source(s), free of the background (“extraction”); or the extended source(s), free of contaminating point source spectra. Depending on the scientific aim, one or both of these data are of interest, such as the spectrum of the central star of a planetary nebula AND the line and continuum spectrum of the nebula with the star removed. In the simple case of a point source with a background gradient, the spectrum of the point source can be simply extracted by subtracting a background fit by a low order function and summing (perhaps with weights, as in optimal extraction) the point source signal at each spectral element in the cross-dispersion direction. When the background is complex or there are many point sources, there is no guide as to how to fit the extended source spectrum beneath the point sources. Simple methods can give a poor estimate of the spectra of point sources and the spectrum of the background in the vicinity of the stars. The application of image restoration algorithms to the spatial component of long slit spectra offers a potential solution.

Sign in / Sign up

Export Citation Format

Share Document