J/A+A/363/517 Redshift from UBRI photometry method (Mobasher+, 2000)
The effect of dust on photometric redshift measurement:
a self-consistent technique.
Mobasher B., Mazzei P.
<Astron. Astrophys. 363, 517 (2000)>
=2000A&A...363..517M 2000A&A...363..517M
ADC_Keywords: Galaxies, photometry ; Photometry, UBVRI ; Redshifts
Keywords: galaxies: evolution - galaxies: formation - galaxies: photometry -
galaxies: starburst - cosmology: observations
Abstract:
A new method is developed for estimating photometric redshifts, using
realistic template Spectral Energy Distributions (SEDs), extending
over four decades in wavelength (i.e. from 0.05µm to 1mm). The
template SEDs are constructed for four different spectral types of
galaxies (elliptical, spiral, irregular and starburst), satisfying the
following characteristics: a) they are normalised to produce the
observed colours of galaxies at z∼0; b) incorporate the
chemo-photometric spectral evolution of galaxies of different types,
in agreement with the observations; c) allow treatment of dust
contribution and its evolution with redshift, consistent with the
spectral evolution models; d) include absorption and re-emission of
radiation by dust and hence, realistic estimates of the far-infrared
radiation; e) include correction for inter-galactic absorption by
Lyman continuum and Lyman forest. Using these template SEDs, the
photometric redshifts are estimated to an accuracy of Δz=0.11.
The simultaneous and self-consistent modelling of both the photometric
and chemical evolution of galaxies and the effect of dust, makes this
technique particularly useful for high redshift galaxies. The effects
on the estimated photometric redshifts, due to assumptions in the
evolutionary population synthesis models, are investigated and
discussed. Also, the degeneracy in the predicted photometric redshifts
and spectral types are examined, using a simulated galaxy catalogue.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 78 73 The calibrating sample
table1.tex 90 212 LaTeX version of table 1
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See also:
J/ApJ/513/34 : HDF photometric redshifts catalog (Fernandez-Soto+, 1999)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name HDF designation
15- 17 A3 --- n_Name Individual notes (1)
19- 20 I2 h RAh Right ascension (J2000)
22- 23 I2 min RAm Right ascension (J2000)
25- 29 F5.2 s RAs Right ascension (J2000)
31 A1 --- DE- Declination sign (J2000)
32- 33 I2 deg DEd Declination (J2000)
35- 36 I2 arcmin DEm Declination (J2000)
38- 42 F5.2 arcsec DEs Declination (J2000)
44- 48 F5.2 mag Imag I-band aperture magnitude in AB system
50- 54 F5.2 mag Rmag R-band aperture magnitude in AB system
56- 60 F5.2 mag Bmag B-band aperture magnitude in AB system
62- 66 F5.2 mag Umag U-band aperture magnitude in AB system
68- 72 F5.3 --- zspect Spectral redshift
74- 78 F5.3 --- zphot Photometric redshift
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Note (1): Individual notes:
1: This galaxy is close to HDF3646+1408 (zspec=0.13). An aperture
of 1.2" diameter is used for this object.
2: This galaxy is within 3" of another object (Lanzetta et al.,
1997AJ....114.1337L 1997AJ....114.1337L). An aperture of 1.2" is used for this galaxy.
3: A spectroscopic redshift of 0.13 is found for this galaxy (Cowie,
1997ApJ...481L...9C 1997ApJ...481L...9C). However, this object is close to
another galaxy (HDF3646+1405) with zspec=0.96 and lies within
1" of a brighter source. It is likely that the spectroscopic
redshift of this galaxy is in error. Lanzetta et al.
(1997AJ....114.1337L 1997AJ....114.1337L) estimate a photometric redshift of 1.2 for
this object compared to our value of 0.675 (when using 1.2"
aperture diameter).
4: This galaxy lies within 1" of a slightly brighter galaxy with no
available redshift. Lanzetta et al. (1997AJ....114.1337L 1997AJ....114.1337L)
estimate a photometric redshift of 0.76 for this object compared
to our estimate of 0.925. It is likely that the spectroscopic
redshift of this object is in error due to confusion with an
overlapping source.
5: This galaxy is undetected in the U-band and shows a very red B-I
colour. It is likely that intervening absorbers have affected its SED.
6: This object shows a very complex morphology with a disk galaxy a
few arcsec to its southwest (Lowenthal et al., 1997ApJ...481..673L 1997ApJ...481..673L).
An aperture of 1.2" diameter is used for this galaxy.
7: An aperture of 1.2" diameter is used for this galaxy due to
close companions.
8: These objects are identified as UV `drop-outs' in Lowenthal et al.
(1997ApJ...481..673L 1997ApJ...481..673L). We assume U=28.01mag. An effective
aperture of 1.2" diameter is used.
9: This galaxy had been given a wrong spectroscopic redshift of
2.845. Its spectroscopic redshift was subsequently measured to be
2.008 (Lanzetta et al., 1997AJ....114.1337L 1997AJ....114.1337L; Dickinson, 1998, in
The Hubble Deep Field. Cambridge University Press. Cambridge. p. 219.).
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Acknowledgements: Bahram Mobasher
(End) Patricia Bauer [CDS] 05-Dec-2000