- The paper presents a dual-mode source extraction technique with SExtractor to reliably detect both bright and faint extragalactic sources.
- The methodology employs TFIT template-fitting to achieve accurate photometry across 21 bands from diverse resolution datasets.
- The research validates a catalog of 35,932 sources over 201.7 arcmin², providing a robust foundation for studying galaxy evolution.
Overview of the CANDELS Multiwavelength Catalog in the UDS Field
The paper presents an extensive effort aimed at compiling and analyzing a comprehensive multiwavelength catalog for the UKIDSS Ultra Deep Survey (UDS) field, an integral part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). This initiative capitalizes on the observations from a range of advanced facilities in ultraviolet to mid-infrared wavelengths, including the Hubble Space Telescope (HST), Subaru Telescope, UKIRT Infrared Deep Sky Survey (UKIDSS), Very Large Telescope (VLT), and the Spitzer Space Telescope. The catalog incorporates data from both ground-based and space telescopes, offering unprecedented insights into the properties of extragalactic sources.
Methodology
The process of catalog compilation involves a detailed data collection strategy, ensuring the inclusion of the highest resolution and deepest available observations for each spectral band. The primary data acquisition is from CANDELS, leveraging the HST's Wide Field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS) imaging capabilities. The field also sees contributions from several auxiliary data sources, such as CFHT/Megacam, Subaru/Suprime-Cam, VLT/HAWK-I, and Spitzer/IRAC.
Central to the methodology is the creation of a homogeneous and consistent catalog across all CANDELS fields. For the UDS field, a two-step source extraction technique was adopted using SExtractor, a software designed for source detection and photometry. This process involved running SExtractor in both a cold mode optimized for bright, extended sources and a hot mode aimed at detecting fainter objects, followed by a combination routine that consolidates results from both modes into a single catalog.
Data Analysis Techniques
For photometry, the catalog employs the Template-Fitting technique via TFIT software, which derives reliable flux measurements for sources in lower-resolution data based on position and morphology information from the high-resolution F160W band. This technique allows for accurate photometric measurements even for blended sources in substantially different resolution datasets.
Key Results and Validation
The catalog consists of 35,932 sources identified over an area of 201.7 square arcminutes, with robust photometric data captured across 21 bands. Validation checks ensure data reliability, involving cross-comparisons of magnitudes in similar filters, color checks using stellar models, and mid-infrared color-color analysis for confirming source classification. Photometric redshifts, derived as part of the catalog analysis, further affirm data integrity with detailed redshift distribution revealing the presence of multiple galaxy clusters.
Implications and Future Directions
The availability of this catalog has profound implications for the paper of galaxy evolution, particularly in deep extragalactic fields. The methodological framework laid by this research facilitates future surveys in handling heterogeneous datasets, providing critical improvements in photometric accuracy for multiwavelength studies.
The catalog's integration into archival databases like MAST and the Rainbow Database supports open scientific inquiry, enabling researchers worldwide to explore these rich datasets. The insights gained from this catalog lay the groundwork for ongoing and future spectroscopic campaigns, which will augment current catalogs with more accurate redshift information and further elucidate the dynamics of the early universe.