J/ApJ/668/839  Spectrophotometric redshifts for 1308 HUDF galaxies (Ryan+, 2007)
================================================================================
The galaxy luminosity function at z=~1 in the HUDF:
probing the dwarf population.
    Ryan R.E Jr, Hathi N.P., Cohen S.H., Malhotra S., Rhoads J.,
    Windhorst R.A., Budavari T., Pirzkal N., Xu C., Panagia N., Moustakas L.A.,
    Di Serego Alighieri S., Yan H.
   <Astrophys. J., 668, 839-845 (2007)>
   =2007ApJ...668..839R
================================================================================
ADC_Keywords: Surveys ; Galaxies, photometry ; Redshifts
Keywords: catalogs - galaxies: high-redshift - surveys

Abstract:
    We present a catalog of spectrophotometric redshifts for 1308 galaxies
    from the Grism ACS Program for Extragalactic Science (GRAPES)
    observations with the Hubble Space Telescope. These low-resolution
    spectra between 6000{AA} and 9500{AA} are supplemented with U, J, H,
    and Ks data from various facilities, resulting in redshifts computed
    with ~40 spectral bins per galaxy. For 75 galaxies in the range
    0.5<z<1.5 with spectroscopic redshifts, the standard deviation in the
    fractional error in 1+z is 0.037. With this catalog, we compute the
    B-band luminosity function in this redshift range from 72 galaxies.
    Due to the depth of the GRAPES survey, we are able to accurately
    constrain the faint-end slope by going to MB~-18mag at z=1.0+/-0.2,
    nearly 2mag fainter than previous studies. The faint-end slope is
    alpha=-1.32+/-0.07. When compared to numerous published values at
    various redshifts, we find strong evidence for a steepening of the
    faint-end slope with redshift, which is expected in the hierarchical
    formation scenario of galaxies.

Description:
    The Grism ACS Program for Extragalactic Science (GRAPES) data consist
    of 40 orbits' worth of observations with the Hubble Space Telescope
    (HST) of the Hubble Ultra Deep Field (HUDF) during Cycle 12. These
    slitless spectroscopic data were taken with the Advanced Camera for
    Surveys (ACS) in the G800L mode and range from ~5500 to 10500{AA} with
    a resolution of R~100, covering ~11arcmin^2^. The GRAPES observations
    were taken over four epochs, each with a different position angle in
    order to minimize the contamination from nearby objects. These data
    were supplemented with the existing grism observations of Riess et al.
    (2004ApJ...600L.163R)

File Summary:
--------------------------------------------------------------------------------
 FileName   Lrecl  Records   Explanations
--------------------------------------------------------------------------------
ReadMe         80        .   This file
table2.dat     83     1308   Representative Catalog
--------------------------------------------------------------------------------

See also:
   II/258 : Hubble Ultra Deep Field Catalog (UDF) (STScI, 2004)
   J/AJ/132/1729 : Hubble Ultra Deep Field BVI-dropout sources (Beckwith+, 2006)

Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
   Bytes Format Units   Label     Explanations
--------------------------------------------------------------------------------
   1-  5  I5    ---     UDF       Hubble Ultra Deep Field identification (1)
   7- 13  F7.2  pix     Xpos      The X pixel coordinate
  15- 21  F7.2  pix     Ypos      The Y pixel coordinate
      23  I1    h       RAh       Hour of Right Ascension (J2000)
  25- 26  I2    min     RAm       Minute of Right Ascension (J2000)
  28- 31  F4.1  s       RAs       Second of Right Ascension (J2000)
      33  A1    ---     DE-       Sign of the Declination (J2000)
  34- 35  I2    deg     DEd       Degree of Declination (J2000)
  37- 38  I2    arcmin  DEm       Arcminute of Declination (J2000)
  40- 43  F4.1  arcsec  DEs       Arcsecond of Declination (J2000)
  45- 50  F6.3  mag     i'mag     The i' band AB magnitude
  52- 56  F5.3  mag   e_i'mag     The error in i'mag
  58- 62  F5.2  ---     beta      The aperture correction (2)
  64- 67  F4.2  ---     zph       Photometric redshift
      69  I1    ---     SpT       [1/8] HyperZ template type (3)
  71- 76  F6.3  Gyr     Age       Estimated Age
  78- 83  F6.2  mag     BMAG      Absolute B band AB magnitude
--------------------------------------------------------------------------------
Note (1): Identification as in Beckwith et al. (2006, Cat. J/AJ/132/1729).

Note (2): The aperture correction betq is defined as
          beta=10Exp[-0.4(i'_HUDF_-i'_GRAPES_)]
     where i'_HUDF_ and i'_GRAPES_ are the the i'-band magnitudes measured
     from the ACS imaging and the GRAPES spectra, respectively.

Note (3): From the Bruzual and Charlot (2003MNRAS.344.1000B) stellar
     population synthesis models assuming an exponential star formation
     history. SpT is defined on the value of {tau}, the e-folding time in
     the exponential function, as follows:
      1 = {tau}=0Gyr
      2 = {tau}=1Gyr
      3 = {tau}=2Gyr
      4 = {tau}=3Gyr
      5 = {tau}=5Gyr
      6 = {tau}=25Gyr
      7 = {tau}=30Gyr
      8 = {tau}={infinity}
--------------------------------------------------------------------------------

History:
    From electronic version of the journal
================================================================================
(End)                  Greg Schwarz [AAS], Patricia Vannier [CDS]    30-Jan-2009