CuTEx and VLFF Service

CuTEx Introduction

CuTEx (Curvature Thresholding Extractor) is a photometric package designed to automatically detect compact sources and extract their fluxes from astronomical images where is present a complex and structure background, like in the case of IR/sub-mm images. The photometric package is divided in two sets of routines dedicated to source detection and flux extraction, respectively.

CuTEx detection is based on the analysis of the second derivative of the image to find the pixel with the highest curvature that are expected to belong to the central emission of a compact source. It provides an estimated guess for the position and the sizes of the compact sources present in the image. CuTEx extraction is a tool for the fitting of multiple elliptical Gaussian function plus a surface representing the local background.

CuTEx package ver 1.0 and its documentation are found at https://vialactea.iaps.inaf.it/vialactea/eng/tools.php

CuTEx service

The Web Service is a tool built to easily run CuTEx on astronomical images. It is composd by a public accessible I/O interface designed to set the input parameters for the photometric package. The outputs delivered to the user are split into two tar file with main and ancillary results, respectively. The main outputs include an ASCII file in IPAC table format with source positions, sizes, fluxes and region files in ds9 format for a quick inspection of the results.

The Web Service inputs are :

Image: The image file in FITS format.

Threshold: a Float number defining the detection threshold in terms of the standard deviation of the second derivative image.

Npixmask: The minimum number of adjactent pixels with curvature above the threshold required to define a source candidate.

PSFPix: The number of pixels that samples the instrumental PSF, i.e. the expected size of a point-like source on the analyzed image.

PSFLim: The variability range of the estimated source size during the fitting process. It is an array of two numbers, in fraction of initial guessed size, i.e. [0.7,1.3] means a variation of 30% with respect to the guessed size.

Warning: since CuTEx search for maximum in curvature it is insensitive to broad sources where the emission varies slowly from one pixel to another. Tests indicate that for Nyquist sampled sources it is able to efficiently detect sources up to 3 times the PSF.

Availability

NEANIAS CuTEx Web Service running on IDL licensed server at OATS-INAF is available at http://ia2-vialactea.oats.inaf.it/ViaLactea-VSH/vshCuTEx.html

VLFF Introduction

VLFF (ViaLactea Filament Finder) is a package aiming to fulfil the requirement of an automatic filament detection tool able to identify and characterize the complex filamentary structure visible in 2D maps with a bright and variable background, like the images of the Galactic plane at IR/Submm wavelengths. VLFF measure the morphological and physical properties of elongated regions with a higher brightness contrast than their surroundings. To such aim, VLFF applies the Hessian operator to the input map and analyzes the the corresponding eigenvalues, looking for the pixels where the emission shows a high curvature along a generic direction. The thresholding of the eigenvalue map provides an initial set of Region of Interests that are analyzed and filtered to produce a list of candidate filamentary regions.

VLFF package ver 1.0 and its documentation are found at https://vialactea.iaps.inaf.it/vialactea/eng/tools.php

VLFF service

Availability

NEANIAS VLFF Web Service running on IDL licensed server at OATS-INAF is available at http://ia2-vialactea.oats.inaf.it/ViaLactea-VSH/vshVLFF.html

Provider

The CuTEx and VLFF Services are provided by INAF-Istituto Nazionale di Astrofisica