J/MNRAS/522/5655 Galaxy pairs identification with PAU/CFHTLens (Gonzalez+, 2023)
The PAU survey close galaxy pairs identification and analysis.
Gonzalez E.J., Rodriguez F., Navarro-girones D., Gaztanaga E., Siudek M.,
Garcia Lambas D., O'Mill A.L., Renard P., Cabayol L., Carretero J.,
Casas R., De Vicente J., Eriksen M., Fernandez E., Garcia-Bellido J.,
Hildebrandt H., Miquel R., Padilla C., Sanchez E., Sevilla-Noarbe I.,
Tallada-Crespi P., Wittje A.
<Mon. Not. R. Astron. Soc. 522, 5655-5668 (2023)>
=2023MNRAS.522.5655G 2023MNRAS.522.5655G (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Galaxies, interacting ; Photometry ; Optical ;
Redshifts ; Combined data
Keywords: Gravitational lensing: weak - Galaxies: groups: general -
Galaxies: haloes
Abstract:
Galaxy pairs constitute the initial building blocks of galaxy
evolution, which is driven through merger events and interactions.
Thus, the analysis of these systems can be valuable in understanding
galaxy evolution and studying structure formation. In this work, we
present a new publicly available catalogue of close galaxy pairs
identified using photometric redshifts provided by the Physics of the
Accelerating Universe Survey (PAUS). To efficiently detect them, we
take advantage of the high-precision photo-z (σ68 < 0.02) and
apply an identification algorithm previously tested using simulated
data. This algorithm considers the projected distance between the
galaxies (rp < 50 kpc), the projected velocity difference (ΔV <
3500 km/s) and an isolation criterion to obtain the pair sample. We
applied this technique to the total sample of galaxies provided by
PAUS and to a subset with high-quality redshift estimates. Finally,
the most relevant result we achieved was determining the mean mass for
several subsets of galaxy pairs selected according to their total
luminosity, colour, and redshift, using galaxy-galaxy lensing
estimates. For pairs selected from the total sample of PAUS with a
mean r-band luminosity 1010.6 h-2 L☉, we obtain a mean mass
of M200 = 1012.2 h-1 M☉, compatible with the
mass-luminosity ratio derived for elliptical galaxies. We also study
the mass-to-light ratio M/L as a function of the luminosity L and find
a lower M/L (or steeper slope with L) for pairs than the one
extrapolated from the measurements in groups and galaxy clusters.
Description:
Identifying galaxy pairs using only photometric information is
difficult given the uncertainty of redshift estimates that leads to
biased catalogues because of projection effects. However, Rodriguez et
al. (2020A&A...634A.123R 2020A&A...634A.123R, R20) presented an algorithm to find close
galaxy pairs using a high-precision photometric redshift catalogue
(σ68 < 0.02), which was assessed using MICE-GC1 simulation The
results demonstrated that this procedure allows to identify these
systems with a purity and a completeness of the sample higher than
0.8, successfully reproducing the distribution of total luminosity and
mass of truly bound galaxy pairs residing in the same dark matter
halo. In addition to the galaxy systems identification, determining
the masses of the dark matter haloes in which they reside provides us
with relevant information for understanding the connection between the
baryonic and the dark matter content in these systems and the
evolution of this relationship. One technique that has been
demonstrated to be very efficient in obtaining the total mass of
galaxy systems is weak gravitational lensing. In particular,
weak-lensing stacking techniques have proved to be a powerful strategy
that allows measuring the mean mass of the galaxy systems that are
combined in the procedure. It was shown that the total mass-luminosity
relation of the identified galaxy pairs can be properly recovered
using this technique in observational data.
In this work, we identify close pairs of galaxies using the photo-z
provided by PAUS. We apply the identification algorithm assessed in
R20 to obtain the pair catalogue and then we determine the mean masses
for several subsets of the identified systems using weak-lensing
stacking techniques. Finally, we also describe some characteristics of
the close pairs of galaxies and the dependence of their mass on some
of their properties, in particular we inspect the mass-luminosity
ratio obtained for the analysed pair subsets. PAUS is a narrow-band
photometric wide-field galaxy survey conducted at the William Herschel
Telescope. The survey is carried out using the PAU camera an 18 CCDs
camera that covers about 1 square degree of the sky, and reaches a
limiting i-band magnitude of ∼23. The novelty of PAUCam resides in its
set of 40 narrow-band filters spanning the range 4500-8500Å with a
width of 13Å and equally spaced at 100Å. The target, the CFHTLS
W1, W3, and W4 fields and GAMA G09 field that overlaps the KiDS
survey. CFHTLenS and KiDS catalogues are references from which PAUS
forced photometry is performed. Since they are deeper than PAUS, it
ensures the completeness in the identification. The broad-band
magnitudes provided by these catalogues are also used in the photo-z
computation. In particular, in this work, we use the data from the W1
and W3 regions. More, the photometric redshifts for the objects
identified in each of these fields are computed via the code BCNz2
which is a template-based photometric redshift code. Pair
identification results are presented in pau.dat for 3400 pairs.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
pau.dat 104 3400 *The close galaxy pairs identified using
CFHTLens photometry and PAUS BCNz2 photometric
redshifts including the fields W1 and W3
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Note on pau.dat: As described in cosmo hub website
(https://cosmohub.pic.es/catalogs/309), the pairs are identified
using the galaxies in PAUS catalogue after removing objects considered as
stars and bad quality objects within a redshift range between 0.2 and 0.6
(total sample). Besides, we consider a galaxy subset with a higher quality
in the redshift estimates, named as the gold sample, obtained by applying an
extra cut that considers the photo-z quality (according to Qz), selecting the
25% of the objects with better photometric redshifts. The identification is
performed by linking galaxies that are close according to the projected
distance, rp (< 50kpc), and with a limiting velocity difference,
δV (< 3500km/s), computed according to PAUS photometric redshifts.
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See also:
J/MNRAS/513/439 : GAMA DR4 spectrum catalog (Driver+, 2022)
J/MNRAS/483/529 : Star-galaxy multi narrow-band classification
(Cabayol+, 2019)
J/A+A/622/A103 : Python Code Investigating GALaxy Emission
(Boquien+, 2019)
J/ApJ/569/720 : Mass-to-light ratio of galaxy systems (Girardi+, 2002)
J/AJ/132/926 : Galaxies in the Hubble Ultra Deep Field (Coe+, 2006)
J/AJ/129/682 : Structural properties of S+S galaxies
(Hernandez-Toledo+, 2005)
J/other/AstBu/73.310 : Isolated galaxy pair limited to M≤-18.5 (Nottale+,2018)
Byte-by-byte Description of file: pau.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 I8 --- ID Pair id number (pair_id)
10- 19 F10.6 deg RAdeg Right ascenction of the brightest pair
component (J2000) (ra_1)
21- 29 F9.6 deg DEdeg Declination of the brightest pair component
(J2000) (dec_1)
31- 35 F5.3 --- zph1 Photometric redshift of the brightest component
(zphot_1)
37- 45 F9.6 mag i1mag i-band apparent magnitude for the brightest
component (magi1)
47- 55 F9.6 mag r1mag r-band apparent magnitude for the brightest
component (magr1)
57- 66 F10.6 deg RA2deg Right ascenction of the faintest pair component
(J2000) (ra_2)
68- 76 F9.6 deg DE2deg Declination of the faintest pair component
(J2000) (dec_2)
78- 82 F5.3 --- zph2 Photometric redshift of the faintest component
(zphot_2)
84- 92 F9.6 mag i2mag i-band apparent magnitude for the brightest
component (magi2)
94-102 F9.6 mag r2mag r-band apparent magnitude for the brightest
component (magr2)
104 I1 --- f_ID Galaxy sample from which the pairs were
identified as 0 for Total 2283 times and 1 for
Gold 1117 times (sample)
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History:
From electronic version of the journal
From website https://cosmohub.pic.es/catalogs/309
License: CC-BY-4.0
(End) Luc Trabelsi [CDS] 16-Jul-2026