Access to Astronomical Catalogues

II/258              Hubble Ultra Deep Field Catalog (UDF)     (STScI, 2004)
The Hubble Ultra Deep Field Catalog
     Beckwith S.V.W.
    <Space Telescope Science Institute (2004)>
ADC_Keywords: Photometry, HST ; Surveys ; Galaxy catalogs

Mission_Name: HST


Description:
    The Hubble Ultra Deep Field (PI: Steven V. W. Beckwith) is a 400-orbit
    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
     ---------------------------------------------------------------

    More details are found in the "intro.txt" file, or from the
    UDF home page.

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
intro.txt         68      419   Introduction
udf-i.dat        213    10179   The Ultra-Deep Field Catalog from F775W image
udf-z.dat        213     7016   The Ultra-Deep Field Catalog from F850LP image


See also:
   II/253 : Chandra Deep Field South: multi-colour data (Wolf+, 2004)
   http://cadcwww.hia.nrc.ca/udf/ : Ultra Deep Field High-Level Science Products
   http://www.stsci.edu/hst/udf : Ultra Deep Field Home Page


Byte-by-byte Description of file: udf-i.dat udf-z.dat

   Bytes Format Units   Label     Explanations

   3-  7  I5    ---     UDF       Running number (G1)
  11- 17  F7.2  pix     Xpos      Position of the source (toward East)
  20- 26  F7.2  pix     Ypos      Position of the source (toward North)
  29- 39  F11.7 deg     RAdeg     Right Ascension (J2000)
  42- 52  F11.7 deg     DEdeg     Declination (J2000)
  56- 60  F5.1  deg     Theta     [-90,+90] source orientation "Theta"
                               (counterclockwise from the X-axis = PA-90)
  64- 68  F5.3  ---     ell       Ellipticity (1-b/a)
  74- 80  F7.2  pix     R50       Half-light radius
  83- 88  F6.2  pix     FWHM      FWHM of a Gaussian fit to each source
  93- 96  F4.2  ---     Sty       Stellarity (1 for point sources,
                                     0 for fully resolved sources)
 105-111  F7.4  mag     Bmag      ?=99.00 AB magnitude in F435W filter (2)
 113-119  F7.4  mag     e_Bmag    ?=99.00 Formal error on Bmag
 122-127  F6.1  ---     Bs/n      Signal to Noise ratio in F435W filter
 132-138  F7.4  mag     Vmag      ?=99.00 AB magnitude in F606W filter (2)
 140-146  F7.4  mag     e_Vmag    ?=99.00 Formal error on Vmag
 149-154  F6.1  ---     Vs/n      Signal to Noise ratio in F606W filter
 159-165  F7.4  mag     imag      ?=99.00 AB magnitude in F775W filter (2)
 167-173  F7.4  mag     e_imag    ?=99.00 Formal error on imag
 176-181  F6.1  ---     is/n      Signal to Noise ratio in F775W filter
 186-192  F7.4  mag     zmag      ?=99.00 AB magnitude in F850LP filter (2)
 194-200  F7.4  mag     e_zmag    ?=99.00 Formal error on zmag
 203-208  F6.1  ---     zs/n      Signal to Noise ratio in F850LP filter
 212-213  I2    ---     Flags     SExtractor flags (1)

Note (1): combination of binary flags with 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.
Note (2): magnitude isophotally matched.



Global Notes:

Note (G1): Nomenclature note:
     Objects in udf-i.dat file are identified as UDF NNNNN in Simbad.
     Objects in udf-z.dat file are identified as UDF 3NNNN in Simbad,
     (i.e, in udf-z.dat file, "Seq = 1" is "UDF 30001" in Simbad).


History:
    From http://cadcwww.hia.nrc.ca/udf/acs-wfc/
(End)                                   Francois Ochsenbein [CDS]    07-May-2005