J/ApJS/242/8 DESI photz and stellar masses galaxies (Zou+, 2019)
Photometric redshifts and stellar masses for galaxies from the
DESI legacy imaging surveys.
Zou H., Gao J., Zhou X., Kong X.
<Astrophys. J. Suppl. Ser., 242, 8 (2019)>
=2019ApJS..242....8Z 2019ApJS..242....8Z (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Galaxies, photometry ; Redshifts ;
Photometry, infrared ; Photometry ; Optical
Keywords: galaxies: clusters: general - galaxies: distances and redshifts -
galaxies: photometry
Abstract:
We present a catalog of photometric redshifts and stellar masses for
galaxies from imaging surveys serving the Dark Energy Spectroscopic
Instrument project. The imaging footprints cover an area of over
14000-deg2. This catalog contains about 0.17 billion morphologically
classified galaxies with r<23mag. It covers the redshift range of z<1
and the mass range of 8.4<log(M*)<11.9. A total of five photometric
bands are used, including three optical filters (g, r, and z) and two
infrared filters (Wide-field Infrared Survey Explorer W1 and W2). We
use k-nearest neighbors and local linear regression algorithms to
estimate photometric redshifts. Based on a spectroscopic sample of
about 2.2 million galaxies, we achieve a redshift bias of
Δznorm=2.4x10-4, accuracy of σΔznorm=0.017,
and outlier rate of about 5.1%. The stellar mass and other physical
parameters are derived by stellar population synthesis model fitting
based on our photometric redshifts. The differences in log(M*) derived
using spectroscopic and photometric redshifts present a 1σ
dispersion of 0.09dex.
Description:
DESI is an international project that will construct a 5000 fiber
multiobject spectrograph for the Mayall 4 m telescope at Kitt Peak
National Observatory (DESI Collaboration et al., 2016,
arXiv:1611.00036). The DESI survey will obtain optical spectra of
about 34 million galaxies and quasars over a five-year period between
2019 and 2024 in order to measure the expansion history and structure
growth of the universe. The spectroscopic targets contain the bright
galaxy sample (0.05<z<0.4), luminous red galaxies (0.4<z<1.0),
emission-line galaxies (0.6<z<1.6), and quasars (z≲3.5). These four
target types are selected using a combination of optical imaging data
in the g, r, and z bands and near-infrared data in the WISE W1 and W2
bands.
We present a catalog of photometric redshifts, stellar masses, and
other inferred physical properties for galaxies from the DESI legacy
imaging surveys. The catalog will be continuously updated for future
data releases of the legacy surveys. This catalog contains 0.17
billion galaxies with r<23.0. The photometric data include three
optical bands (g, r, and z) from three new optical imaging surveys and
two infrared bands (W1 and W2) from latest observations of WISE. The
total area is over 14000-deg2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
photoz.dat 685 303379640 photo-z and stellar mass catalog for galaxies
in DESI imaging surveys (2020/09/11 version)
photoz.fits 2880 26967087 Fits version of the catalog (2020/09/11 version)
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See also:
https://www.legacysurvey.org : DESI Legacy Imaging Surveys Home Page
http://batc.bao.ac.cn/~zouhu/online-data/desi_photoz : DESI Home Page
Byte-by-byte Description of file: photoz.dat
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Bytes Format Units Label Explanations
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1- 16 I16 --- ID Unique object ID
18- 35 F18.14 deg RAdeg Right ascension (J2000)
37- 56 F20.16 deg DEdeg Declination (J2000)
58- 66 F9.6 mag gmag g-band magnitude
68- 76 F9.6 mag rmag r-band magnitude
78- 86 F9.6 mag zmag z-band magnitude
88- 96 F9.6 mag W1mag W1-band magnitude
98-106 F9.6 mag W2mag W2-band magnitude
108-120 E13.6 mag e_gmag g-band magnitude error
122-133 F12.10 mag e_rmag r-band magnitude error
135-147 E13.6 mag e_zmag z-band magnitude error
149-161 E13.6 mag e_W1mag W1-band magnitude error
163-175 E13.6 mag e_W2mag W2-band magnitude error
177-185 F9.6 mag GalDepth-g Galaxy depth in g band
187-195 F9.6 mag GalDepth-r Galaxy depth in r band
197-205 F9.6 mag GalDepth-z Galaxy depth in z band
207-210 A4 --- Type Tractor Type
212-223 F12.8 arcsec ShapedeV-R Half-light radius of de Vaucouleurs model
225-237 F13.10 --- ShapedeV-E1 de Vaucouleurs ellipticity component 1
239-251 F13.10 --- ShapedeV-E2 de Vaucouleurs ellipticity component 2
253-264 F12.8 arcsec ShapeExp-R Half-light radius of exponential model
266-279 F14.11 --- ShapeExp-E1 Exponential ellipticity component 1
281-294 F14.11 --- ShapeExp-E2 Exponential ellipticity component 2
296-298 F3.1 --- Fracdev [0/1] Fraction of model in deVauc
300-302 I3 --- Nneighbour Number of neighbours used for photo-z
estimation
304 I1 --- Nfilter [1/5] Number of filters used
306-317 F12.9 --- photoz Estimated photometric redshift
319-330 F12.10 --- e_photoz Estimated photometric redshift error
332-339 F8.4 --- specz ?=-10 Spectroscopic redshift if available
(if not, set -10)
341-351 F11.9 --- meanz Mean spectroscopic redshift of k nearest
neighbours
353-363 F11.9 --- sigmaz redshift RMS of k nearest neighbours
365-378 F14.12 --- nearestz Mean Euclidean distance in the color space
of neighbours
380-390 F11.9 --- meandist Mean Euclidean distance in the color space
of neighbours
392-404 F13.7 --- chiBest Chi square of the best BC03 model fitting
406-407 I2 --- ModBest ID of the best-fitted BC03 model
409-411 F3.1 mag E(B-V)Best Best estimated E(B-V) in three values of
0, 0.5, and 1.0mag
413-425 E13.6 --- ScaleBest Scaling factor between observed SED and
model SED
427-433 F7.3 mag gMAG g-band absolute magnitude
435-441 F7.3 mag rMAG r-band absolute magnitude
443-449 F7.3 mag zMAG z-band absolute magnitude
451-457 F7.3 mag W1MAG W1-band absolute magnitude
459-465 F7.3 mag W2MAG W2-band absolute magnitude
467-479 F13.1 yr AgeBest Best estimated age
481-494 F14.1 yr AgeInf ?=-99 Lower limit of age with
68% confidence level
496-509 F14.1 yr AgeMed ?=-99 Median age
511-522 E12.6 yr AgeSup ?=-99 Upper limit of age with
68% confidence level
524-531 F8.5 [Msun] logMassBest ?=-9 Best estimated log stellar mass
533-541 F9.5 [Msun] logMassInf ?=-99 Lower limit of log stellar mass with
68% confidence level
543-551 F9.5 [Msun] logMassMed ?=-99 Median log stellar mass
553-561 F9.5 [Msun] logMassSup ?=-99 Upper limit of log stellar mass with
68% confidence level
563-575 F13.9 Msun/yr SFRBest ?=-99 Best estimated SFR
577-588 F12.8 Msun/yr SFRInf ?=-99 Lower limit of SFR with
68% confidence level
590-601 F12.8 Msun/yr SFRMed ?=-99 Median SFR
603-614 F12.8 Msun/yr SFRSup ?=-99 Upper limit of SFR with
68% confidence level
616-625 F10.5 1/yr sSFRBest Best estimated sSFR
627-635 F9.5 1/yr sSFRInf ?=-99 Lower limit of sSFR with
68% confidence level
637-645 F9.5 1/yr sSFRMed ?=-99 Median sSFR
647-655 F9.5 1/yr sSFRSup ?=-99 Upper limit of sSFR with
68% confidence level
657-665 F9.5 [Lsun] logLNUVBest Best estimated log NUV luminosity
667-675 F9.5 [Lsun] logLRBest Best estimated log R-band luminosity
677-685 F9.5 [Lsun] logLKBest Best estimated log K-band luminosity
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Acknowledgements:
Zou Hu, zouhu(at)bao.ac.cn
(End) Patricia Vannier [CDS] 11-Sep-2020