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 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 6000Å and 9500Å 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 10500Å with
a resolution of R∼100, covering ∼11arcmin2. 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 2004ApJ...600L.163R)
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 83 1308 Representative Catalog
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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
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Bytes Format Units Label Explanations
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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
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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 2003MNRAS.344.1000B) stellar
population synthesis models assuming an exponential star formation
history. SpT is defined on the value of τ, the e-folding time in
the exponential function, as follows:
1 = τ=0Gyr
2 = τ=1Gyr
3 = τ=2Gyr
4 = τ=3Gyr
5 = τ=5Gyr
6 = τ=25Gyr
7 = τ=30Gyr
8 = τ=∞
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 30-Jan-2009