J/MNRAS/483/3060 Candidate massive galaxies at z∼4 in the DES (Guarnieri+, 2019)
Candidate massive galaxies at z ∼ 4 in the Dark Energy Survey.
Guarnieri P., Maraston C., Thomas D., Pforr J., Gonzalez-Perez V.,
Etherington J., Carlsen J., Morice-Atkinson X., Conselice C.J.,
Gschwend J., Carrasco Kind M., Abbott T., Allam S., Brooks D., Burke D.,
Carnero Rosell A., Carretero J., Cunha C., D'Andrea C., da Costa L.,
De Vincente J., DePoy D., Diehl H.T., Doel P., Frieman J.,
Garcia-Bellido J., Gruen D., Gutierrez G., Hanley D., Hollowood D.,
Honscheid K., James D., Jeltema T., Kuehn K., Lima M., Maia M.A.G.,
Marshall J., Martini P., Melchior P., Menanteau F., Miquel R.,
Plazas Malagon A., Richardson S., Romer K., Sanchez E., Scarpine V.,
Schindler R., Sevilla I., Smith M., Soares-Santos M., Sobreira F.,
Suchyta E., Tarle G., Walker A., Wester W.
<Mon. Not. R. Astron. Soc., 483, 3060-3081 (2019)>
=2019MNRAS.483.3060G 2019MNRAS.483.3060G (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Redshifts ; Photometry, SDSS ; Photometry, infrared
Keywords: galaxies: evolution - galaxies: high-redshift
Abstract:
Using stellar population models, we predicted that the Dark Energy
Survey (DES) - due to its special combination of area (5000deg2) and
depth (i=24.3) - would be in the position to detect massive
(≳1011M☉) galaxies at z∼4. We confront those theoretical
calculations with the first ∼150deg2 of DES data reaching nominal
depth. From a catalogue containing ∼5 million sources, ∼26000 were
found to have observed-frame g-r versus r-i colours within the locus
predicted for z∼4 massive galaxies. We further removed contamination
by stars and artefacts, obtaining 606 galaxies lining up by the model
selection box. We obtained their photometric redshifts and physical
properties by fitting model templates spanning a wide range of star
formation histories, reddening and redshift. Key to constrain the
models is the addition, to the optical DES bands g, r, i, z, and Y, of
near-IR J, H, Ks data from the Vista Hemisphere Survey. We further
applied several quality cuts to the fitting results, including
goodness of fit and a unimodal redshift probability distribution. We
finally select 233 candidates whose photometric redshift probability
distribution function peaks around z∼4, have high stellar masses
[log(M*/M☉)∼11.7 for a Salpeter IMF] and ages around 0.1Gyr,
i.e. formation redshift around 5. These properties match those of the
progenitors of the most massive galaxies in the local Universe. This
is an ideal sample for spectroscopic follow-up to select the fraction
of galaxies which are truly at high redshift. These initial results
and those at the survey completion, which we shall push to higher
redshifts, will set unprecedented constraints on galaxy formation,
evolution, and the re-ionization epoch.
Description:
Our aim is to identify the most likely high-redshift (z∼4) massive
galaxy candidates within a data set of ∼4.9 million objects. Starting
from the simulations performed by Davies et al. (2013MNRAS.434..296D 2013MNRAS.434..296D,
hereafter D13), we proceed using real DES (The Dark Energy Survey
Collaboration 2005astro.ph.10346T 2005astro.ph.10346T; Rossetto et al.
2011AJ....141..185R 2011AJ....141..185R) data in this context for the first time. In this
paper, we focused on the z∼4 case in order to maximize the chance to
find objects in the small area covered by the Science Verification
(SV) data.
We used photometric data in the g, r, i, z, and Y bands from the DES
Y3 Gold 2.0 release, which contains the latest, highest quality
photometry for DES. Among the magnitude options, we use MAG_DETMODEL
photometry (in the AB system), as it refers to the same physical
aperture hence it is optimal for template fitting. As described in
Melchior et al. (2015MNRAS.449.2219M 2015MNRAS.449.2219M), magnitudes are measured by
SExtractor in each filter using a model fit to the surface brightness
of the source in each image. The detection image for each object was
created by the DES pipeline by linearly combining the r, i, and z
images (Abbott et al. 2018ApJS..239...18A 2018ApJS..239...18A, Cat. II/357).
In order to strengthen the reliability of our photometric fitting
procedure, as mentioned in the previous sections, we looked for
additional bands for the sources within the colour-colour map. We were
able to cross-match the DES optical data with the VHS survey (McMahon
2012sngi.confE..37M), thereby extending our photometric catalogue to
the near-infrared bands J, H, and Ks.
We then analyse in detail the fitting results for all candidates and
conservatively retain only those obeying several quality criteria,
including a unimodal probability distribution function (PDF) in
redshift, a good Χ2r and other model parameters.
At the end of the procedure, we select 233 individual galaxies, of
which some are selected with both reddening options. We find 109 using
the SMC reddening law and 203 using the Calzetti law. For these, we
examine their properties (including mass, age, SFR, SFH) and draw
initial conclusions on galaxy evolution, using also galaxy formation
simulations as a comparison.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 70 54 Properties of the Straatman et al.
(2014ApJ...783L..14S 2014ApJ...783L..14S) sample of quiescent
galaxies compared to the values we obtain using
our fitting set-up and those bands matching our
DES+VHS photometry
tablea1.dat 94 109 Properties of the best candidates for the SMC
law case
tablea2.dat 94 203 Properties of the best candidates for the
Calzetti-type reddening
tableb1.dat 151 233 Photometry for all galaxies matching the best
candidate criteria
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See also:
II/371 : The Dark Energy Survey (DES): Data Release 2 (Abott+, 2021)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- ID Galaxy name from Straatman et al.
(2014ApJ...783L..14S 2014ApJ...783L..14S) (S14),
[SLS2014] ID in Simbad
17- 21 F5.3 --- zS14 ? Photometric redshift from S14
23- 26 F4.2 --- e_zS14 ? Error on zS14
28 A1 --- f_zS14 [*] Flag on zS14 (1)
30- 33 F4.2 --- zus ? Photometric redshift from this work
35- 39 F5.2 [Msun] MstarS14 ? Stellar mass from S14 (2)
41- 45 F5.2 [Msun] Mstarus ? Stellar mass from this work (2)
47- 50 F4.2 [Gyr] AgeS14 ? Galaxy age from S14
52- 55 F4.2 [Gyr] Ageus ? Galaxy age from this work
57- 64 A8 --- Reddening Reddening option (3)
66- 70 F5.3 --- Chir2 ? Reduced chi-squared for each reddening
option
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Note (1): Flag as follows:
* = zS14 for this source is a spectroscopic redshift
Note (2): Note that the Straatman et al. (2014ApJ...783L..14S 2014ApJ...783L..14S) stellar masses
refer to a Chabrier IMF, while ours to a Salpeter IMF. The latter are
∼0.2dex larger, hence the Straatman et al. (2014ApJ...783L..14S 2014ApJ...783L..14S)
values should be increased by +0.20dex to ensure a meaningful
comparison with our derived values.
Note (3): For each object, we obtain two results according to the assumed
reddening option: the so-called SMC law (Prevot et al.
1984A&A...132..389P 1984A&A...132..389P; Bouchet et al. 1985A&A...149..330B 1985A&A...149..330B) and the
well-known Calzetti law (Calzetti et al. 2000ApJ...533..682C 2000ApJ...533..682C).
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Byte-by-byte Description of file: tablea1.dat tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- ID Object ID (G1)
11- 14 F4.2 --- zphot Photometric redshift
16- 19 F4.2 --- E_zphot Upper error on zphot (1)
21- 24 F4.2 --- e_zphot Lower error on zphot (1)
26- 30 F5.3 --- Chir2 Reduced chi-squared of the fit
32- 36 F5.2 [Msun] logMstar Log of stellar mass
38- 41 F4.2 [Msun] E_logMstar Upper error on logMstar (1)
43- 46 F4.2 [Msun] e_logMstar Lower error on logMstar (1)
48- 53 F6.2 mag iMag Absolute magnitude
55- 58 F4.2 Gyr Age Age
60- 69 A10 --- SFH Stellar formation history
71- 73 A3 Sun [Z/H] Metallicity
75- 79 F5.2 --- sigAGN The number of σ used to estimate
potential AGN contamination (2)
81- 84 F4.2 --- zDES Photometric redshift found by fitting DES
only bands
86- 89 F4.2 --- zBPZ Redshift from the DES pipeline
91- 94 F4.2 mag E(B-V) Extinction
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Note (1): Errors refer to the 99 per cent confidence level
Note (2): For all our best candidates, we have evaluated a parameter, dubbed
σAGN, which is meant to quantify the difference between the
magnitude of the object over an extended aperture and its PSF
magnitude. For a pure AGN, these two quantities are the same. We
define σAGN as σAGN=|(i-iPSF)/sqrt(ierr2+iPSFerr2)|,
where i and iPSF are an object extended and PSF i-band magnitudes.
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Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- ID Object ID (G1)
11- 20 F10.6 deg RAdeg Right ascension (J2000)
22- 31 F10.6 deg DEdeg Declination (J2000)
33- 39 F7.4 mag gmag g-band magnitude
41- 46 F6.4 mag e_gmag Error on gmag
48- 54 F7.4 mag rmag r-band magnitude
56- 61 F6.4 mag e_rmag Error on rmag
63- 69 F7.4 mag imag i-band magnitude
71- 76 F6.4 mag e_imag Error on imag
78- 84 F7.4 mag zmag z-band magnitude
86- 91 F6.4 mag e_zmag Error on zmag
93- 99 F7.4 mag Ymag Y-band magnitude
101-106 F6.4 mag e_Ymag Error on Ymag
108-114 F7.4 mag Jmag ? J-band magnitude
116-121 F6.4 mag e_Jmag ? Error on Jmag
123-129 F7.4 mag Hmag ? H-band magnitude
131-136 F6.4 mag e_Hmag ? Error on Hmag
138-144 F7.4 mag Ksmag ? Ks-band magnitude
146-151 F6.4 mag e_Ksmag ? Error on Ksmag
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Global notes:
Note (G1): ID is the CoadID identifier of DES DR1 catalog (Abbott et al.,
2018ApJS..239...18A 2018ApJS..239...18A, Cat. II/357).
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 22-Jul-2022