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HUBBLEUDF - Hubble Ultra Deep Field Catalog

HEASARC
Archive

Overview

The Hubble Ultra Deep Field (UDF, Principle Investigator: Steven V. W. Beckwith) is a 400-orbit Hubble Space Telescope (HST) Cycle 12 program to image a single field of the Wide Field Camera (WFC) of the Advanced Camera for Surveys (ACS) in four filters: F435W (B), F606W (V), F775W (i), and F850LP (z). The observations took place over 4 months from September 2003 to January 2004 under two program IDs: 9978 and 10086.

The observations consist of half-orbit exposures, cycling through each of the filters in a 4-point dither pattern to provide sub-pixel sampling, as well as a larger-scale 3-point line pattern to cover the 2 second of arc gap between the two ACS/WFC chips. The total exposure times are summarized below, with typical exposure times of 1200s for individual images. The AB magnitude zero-points for ACS are current as of March 2004.

                   Number of   Number of   Total Exp.    AB mag.
                   Orbits      Exposures   Time (s)      zero-point
     B (F435W):       56          112       134880        25.673
     V (F606W):       56          112       135320        26.486
     i (F775W):      144          288       347110        25.654
     z (F850LP):     144          288       346620        24.862
This HEASARC Browse table contains the list of sources found in the deepest UDF image, the i-band image. The formal i-band catalog contains a total of 10,040 sources. A visual inspection of all the sources revealed an additional 5 spurious sources (which do not form part of the catalog). Moreover, the deblending algorithms in SExtractor caused an additional 100 sources to be missed, owing to their proximity to brighter sources. These sources were identified manually, and formally added by doing another SExtractor run with considerably different deblending parameters, in order to detect them all. An initial list of 208 sources was produced, which was then reduced to a total of 100 sources after visual inspection and rejection of sources that were clearly part of previously identified sources. These additional sources are denoted by ID numbers 20001 - 20208.

Although the i-band image is the deepest image, there remain additional sources that were not detected in i-band, even though they may be detected in one of the other bands. Therefore, the authors produced a second catalog based on detection in the z-band image (not part of the present table), and an additional 39 sources are included from this catalog that were detected at > 10 sigma in the z-band image, but were not in the catalog that was run using the i-band image for detection. These additional sources are denoted by ID numbers above 30000. More details are found in the file ftp://cdsarc.u-strasbg.fr/pub/cats/II/258/intro.txt or from the UDF home page at http://www.stsci.edu/hst/udf/.


Catalog Bibcode

<II/258>

References

The Hubble Ultra Deep Field Catalog
    <Space Telescope Science Institute (2004)>
Beckwith, S.V.W.  et al. (2004), in preparation.

Provenance

This table was created by the HEASARC in May 2005 based on CDS table II/258/udf-i.dat.

Parameters

Name
The Hubble Ultra Deep Field name of the object, using the recommended UDF prefix and a running identication number.

X_Pos
The x-position of the source in pixels, where x increases towards the East direction, and 1 pixel = 0.03 arcseconds.

Y_Pos
The y-position of the source in pixels, where y increases towards the North direction, and 1 pixel = 0.03 arcseconds.

RA
The Right Ascension of the source in the selected equinox. This was given in J2000 equatorial coordinates and to a precision of 10-7 degrees in the original table.

Dec
The Declination of the source in the selected equinox. This was given in J2000 equatorial coordinates and to a precision of 10-7 degrees in the original table.

LII
The Galactic Longitude of the source.

BII
The Galactic Latitude of the source.

Orientation
[-90,+90] The source orientation angle "Theta", in degrees, measured counterclockwise from the x-axis = PA-90, with values from -90 to +90 degrees.

Ellipticity
The ellipticity of the source, defined as (1-b/a) where a is the semi-major axis and b is the semi-minor axis.

Half_Light_Radius
The half-light radius of the source, in pixels.

Gaussian_FWHM
The full-width half-maximum (FWHM) of the Gaussian fit to the source, in pixels.

Stellarity
The stellarity of the source (1 for point sources, 0 for fully resolved sources).

Bmag
The AB magnitude of the source in the F435W filter (pivot wavelength of 4311.80 Angstroms), isophotally matched. A value of +99.0 is used to indicate a non-detection in this filter.

Bmag_Error
The formal error in Bmag, from the rms map plus Poisson statistics.

Bmag_SNR
The Signal to Noise Ratio (SNR) of the source in the F435W filter, obtained by dividing the measured flux by the rms, which includes all the information from the inverse variance weight map.

Vmag
The AB magnitude of the source in the F606W filter (pivot wavelength of 5915.38 Angstroms), isophotally matched. A value of +99.0 is used to indicate a non-detection in this filter.

Vmag_Error
The formal error in Vmag, from the rms map plus Poisson statistics.

Vmag_SNR
The Signal to Noise Ratio (SNR) of the source in the F606W filter, obtained by dividing the measured flux by the rms, which includes all the information from the inverse variance weight map.

Imag
The AB magnitude of the source in the F775W filter (pivot wavelength of 7697.34 Angstroms), isophotally matched. A value of +99.0 is used to indicate a non-detection in this filter.

Imag_Error
The formal error in imag, from the rms map plus Poisson statistics.

Imag_SNR
The Signal to Noise Ratio (SNR) of the source in the F775W filter, obtained by dividing the measured flux by the rms, which includes all the information from the inverse variance weight map.

Zmag
The AB magnitude of the source in the F850LP filter (pivot wavelength of 9103.29 Angstroms), isophotally matched. A value of +99.0 is used to indicate a non-detection in this filter.

Zmag_Error
The formal error in zmag, from the rms map plus Poisson statistics.

Zmag_SNR
The Signal to Noise Ratio (SNR) of the source in the F850LP filter, obtained by dividing the measured flux by the rms, which includes all the information from the inverse variance weight map.

Sextractor_Flags
The SExtractor flags for the source, being the combination of binary flags having the following meaning:

     1 = The object has neighbors, bright and close enough to
         significantly bias the photometry, or bad pixels
     2 = The object was originally blended with another one.
     4 = At least one pixel of the object is saturated (or very close to).
     8 = The object is truncated (too close to an image boundary).
    16 = Object's aperture data are incomplete or corrupted.
  

Contact Person

Questions regarding the HUBBLEUDF database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 13-May-2010