J/MNRAS/498/3241 Lenses DES J0408-5354 and WGD 2038-4008 (Buckley-Geer+, 2020)
STRIDES: Spectroscopic and photometric characterization of the environment and
effects of mass along the line of sight to the gravitational lenses
DES J0408-5354 and WGD 2038-4008.
Buckley-Geer E.J., Lin H., Rusu C.E., Poh J., Palmese A., Agnello A.,
Christensen L., Frieman J., Shajib A.J., Treu T., Collett T., Birrer S.,
Anguita T., Fassnacht C.D., Meylan G., Mukherjee S., Wong K.C., Aguena M.,
Allam S., Avila S., Bertin E., Bhargava S., Brooks D., Carnero Rosell A.,
Carrasco Kind M., Carretero J., Castander F.J., Costanzi M., da Costa L.N.,
De Vicente J., Desai S., Diehl H.T., Doel P., Eifler T.F., Everett S.,
Flaugher B., Fosalba P., Garcia-Bellido J., Gaztanaga E., Gruen D.,
Gruendl R.A., Gschwend J., Gutierrez G., Hinton S.R., Honscheid K.,
James D.J., Kuehn K., Kuropatkin N., Maia M.A.G., Marshall J.L.,
Melchior P., Menanteau F., Miquel R., Ogando R.L.C., Paz-Chinchon F.,
Plazas A.A., Sanchez E., Scarpine V., Schubnell M., Serrano S.,
Sevilla-Noarbe I., Smith M., Soares-Santos M., Suchyta E., Swanson M.E.C.,
Tarle G., Tucker D.L., Varga T.N., (The DES Collaboration)
<Mon. Not. R. Astron. Soc., 498, 3241-3274 (2020)>
=2020MNRAS.498.3241B 2020MNRAS.498.3241B (SIMBAD/NED BibCode)
ADC_Keywords: Gravitational lensing ; Galaxies, group ; Positional data ;
Redshifts ; Velocity dispersion ; Photometry ; Spectroscopy ;
Optical
Keywords: gravitational lensing: strong - galaxies: groups: general -
quasars: individual: DES J0408-5354, WGD 2038-4008
Abstract:
tn time-delay cosmography, three of the key ingredients are
(1) determining the velocity dispersion of the lensing galaxy,
(2) identifying galaxies and groups along the line of sight with
sufficient proximity and mass to be included in the mass model, and
(3) estimating the external convergence κext from less massive
structures that are not included in the mass model. We present results
on all three of these ingredients for two time-delay lensed quad
quasar systems, DES J0408-5354 and WGD 2038-4008 . We use the Gemini,
Magellan, and VLT telescopes to obtain spectra to both measure the
stellar velocity dispersions of the main lensing galaxies and to
identify the line-of-sight galaxies in these systems. Next, we
identify 10 groups in DES J0408-5354 and two groups in WGD 2038-4008
using a group-finding algorithm. We then identify the most significant
galaxy and galaxy-group perturbers using the 'flexion shift'
criterion. We determine the probability distribution function of the
external convergence κext for both of these systems based on
our spectroscopy and on the DES-only multiband wide-field
observations. Using weighted galaxy counts, calibrated based on the
Millennium Simulation, we find that DES J0408-5354 is located in a
significantly underdense environment, leading to a tight (width ∼3 per
cent), negative-value κext distribution. On the other hand,
WGD 2038-4008 is located in an environment of close to unit density,
and its low source redshift results in a much tighter κext of
∼1 per cent, as long as no external shear constraints are imposed.
Description:
The DES is a deep sky survey that was carried out using the Dark
Energy Camera (DECam; Flaugher et al. 2015AJ....150..150F 2015AJ....150..150F) located on
the Blanco 4m telescope at the Cerro Tololo Inter-American Observatory
in the Chilean Andes. The survey ran from 2013 to 2019 and covered
∼5100deg2 of the southern sky in five optical filters (grizY). The
DES data are processed by the DES Data Management team (DESDM;
Morganson et al. 2018PASP..130g4501M 2018PASP..130g4501M) to produce annual data releases
that consist of coadded images and object catalogues. We have used two
data sets for the work described here, the first year of DES data
which is referred to as DES Year 1 (Y1) and the first three years
known as DES Year 3 (Y3).
Spectroscopic observations were carried out using three instruments:
(1) the Gemini Multi-Object Spectrograph (GMOS-S) on the Gemini South
telescope; (2) the Low Dispersion Survey Spectrograph (LDSS-3) on the
Magellan Clay telescope; and (3) the Multi-Unit Spectroscopic Explorer
(MUSE) on the European Southern Observatory (ESO) Very Large Telescope
(VLT) Unit Telescope 4 (UT4).
Objects:
---------------------------------------------------------------
RA (ICRS) DE Designation(s)
---------------------------------------------------------------
04 08 21.69 -53 53 59.5 DES J0408-5354 = DES J0408-5354
20 38 02.64 -40 08 14.6 DES J2038-4008 = DES J2038-4008
---------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 82 16 Spectroscopic observations for the
DES J0408-5354 and WGD 2038-4008 systems
table2.dat 51 10 Velocity dispersion results for the main lensing
galaxies in the DES J0408-5354 and WGD 2038-4008
systems
table3.dat 127 12 Group properties in the field of view of
DES J0408-5354 and WGD 2038-4008
table4.dat 130 20 Properties of the 10 galaxies with the largest
flexion shifts in the field of DES J0408-5354
and WGD 2038-4008
tablea1.dat 129 252 Properties of all 199 galaxies in spectroscopic
survey of the field of DES J0408-5354 and 54
galaxies in the spectroscopic survey of the
field of WGD 2038-4008
tablea2.dat 81 114 Properties of galaxies in each trial group
tablea3.dat 76 2 Properties of redmapper clusters in the field
of view of WGD 2038-4008
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- System Name of the observed system
(DES J0408-5354 or WGD 2038-4008)
16- 28 A13 --- Telescope Telescope used for the observation
30- 35 A6 --- Instrument Instrument used for the observation
37- 52 A16 --- Mask Name of the mask
54- 60 A7 --- Grism Grating/Grism
62- 75 A14 --- UTdate Date of the observation
77- 82 A6 s ExpTime Exposure time
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- System Name of the observed system
(DES J0408-5354 or WGD 2038-4008)
16- 25 A10 --- Mask Name of the mask (1)
27- 29 I3 km/s sigma Velocity dispersion
31- 32 I2 km/s e_sigma Error on sigma
34- 37 F4.2 arcsec Slit Slit width
39- 41 F3.1 arcsec Window Extraction window
43- 46 F4.2 arcsec Seeing Seeing FWHM
48- 51 F4.2 --- beta Moffat index
--------------------------------------------------------------------------------
Note (1): The main lensing galaxy G1 in DES J0408-5354 was measured from four
independently observed spectra: two from Magellan LDSS-3, one from
Gemini South GMOS-S, and one from VLT MUSE. G1 was targeted on two of
the four Magellan LDSS-3 masks listed in Table 1, 'des0408a' and
'des0408b'; hereafter these two masks will be denoted 'Magellan a'
and 'Magellan b'. G1 was targeted on one of the Gemini South GMOS-S
masks in Table 1, 'DESJ0408-5354_A2' (R400 grating), hereafter denoted
'Gemini A2'.
The main lensing galaxy G in WGD 2038-4008 was measured from one
spectrum observed using Gemini South GMOS-S, specifically on mask
'DESJ2038-4008_A' in Table 1 (B600 grating), hereafter denoted
'Gemini A' for simplicity.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- System Name of the observed system
(DES J0408-5354 or WGD 2038-4008)
16- 17 I2 --- ID Group identifier
19 A1 --- f_ID [*] Flag on ID (1)
21- 25 F5.3 --- z Group redshift
27- 28 I2 --- N Number of spectroscopically identified
galaxies
30- 32 I3 km/s sigmarest Group rest-frame velocity dispersion
(rounded to the nearest 10km/s)
34- 35 I2 km/s E_sigmarest Upper error on sigmarest
37- 38 I2 km/s e_sigmarest Lower error on sigmarest
40 A1 --- l_sigmaint Limit flag on sigmaint
42- 44 I3 km/s sigmaint Group intrinsic velocity dispersion
(rounded to the nearest 10km/s)
46- 48 I3 km/s E_sigmaint ? Upper error on sigmaint
50- 52 I3 km/s e_sigmaint ? Lower error on sigmaint
54- 57 F4.2 Mpc R200 Group R200 radius
59- 62 F4.2 Mpc E_R200 Upper error on R200
64- 67 F4.2 Mpc e_R200 Lower error on R200
69- 78 F10.6 deg RAdeg Right ascension (J2000) of the group
centroid
80- 89 F10.6 deg DEdeg Declination (J2000) of the group centroid
91- 94 F4.2 arcmin e_RAdeg Error on RAdeg
96- 99 F4.2 arcmin e_DEdeg Error on DEdeg
101- 103 I3 arcsec Dtheta Projected distance of the centroid to the
lens
105- 106 I2 arcsec E_Dtheta Upper error on Dtheta
108- 109 I2 arcsec e_Dtheta Lower error on Dtheta
111 A1 --- l_logD3x Limit flag on logD3x
113- 117 F5.2 [arcsec] logD3x Logarithm of the median flexion shift
(see Section 6.1 of the article)
119- 122 F4.2 [arcsec] E_logD3x ? Upper error on logD3x
124- 127 F4.2 [arcsec] e_logD3x ? Lower error on logD3x
--------------------------------------------------------------------------------
Note (1): Flag as follows:
* = Group contains the lens galaxy
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- System Name of the observed system
(DES J0408-5354 or WGD 2038-4008)
16- 24 A9 --- ID DES Y3 object identifier
26- 27 A2 --- f_ID Flag on ID (1)
29- 33 A5 --- OName Alternative identifier
35- 44 F10.6 deg RAdeg Right ascension (J2000)
46- 55 F10.6 deg DEdeg Declination (J2000)
57- 63 F7.5 --- z Redshift
65- 69 F5.3 --- e_z ? Error on z (2)
71- 76 F6.3 mag imag DES i-band magnitude
78- 82 F5.2 [Msun] logM* Logarith of the stellar mass (3)
84- 87 F4.2 [Msun] E_logM* Upper error on logM* (3)
89- 92 F4.2 [Msun] e_logM* Lower error on logM* (3)
94- 98 F5.1 arcsec Dtheta Projected distance to the lensing galaxy
100- 104 F5.2 [arcsec] logD3xZ Logarithm of the flexion shifts calculated
using the scaling relations by
Zahid et al. (2016ApJ...832..203Z 2016ApJ...832..203Z) (4)
106- 109 F4.2 [arcsec] E_logD3xZ Upper error on logD3xZ
111- 114 F4.2 [arcsec] e_logD3xZ Lower error on logD3xZ
116- 120 F5.2 [arcsec] logD3xA Logarithm of the flexion shifts calculated
using the scaling relations by
Auger et al. (2011MNRAS.411L...6A 2011MNRAS.411L...6A) (4)
122- 125 F4.2 [arcsec] E_logD3xA Upper error on logD3xA
127- 130 F4.2 [arcsec] e_logD3xA Lower error on logD3xA
--------------------------------------------------------------------------------
Note (1): Flag as follows:
* = Galaxy is not in the spectroscopy survey; stellar masses and flexion
shift estimates are from photometric redshifts
** = Galaxy has spurious MOF photometry. For these galaxies, we use
MAGAUTOCORRECTED photometry to calculate stellar masses instead
Note (2): Spectroscopic redshift uncertainties are about 100km/s, or 0.00033 in
redshift
Note (3): Stellar masses and corresponding uncertainties were calculated using
the Le PHARE galaxy template fitting code and DES Y3 photometry
(see Section 3.3 of the article)
Note (4): See Section 6.1 of the article for more details
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- System Name of the observed system
(DES J0408-5354 or WGD 2038-4008)
16- 25 A10 --- ID DES Y3 or DES Y1 object identifier (1)
27- 28 A2 --- f_ID [**] Flag on ID (2)
30- 35 A6 --- OName Alternative identifier
37- 46 F10.6 deg RAdeg Right ascension (J2000)
48- 57 F10.6 deg DEdeg Declination (J2000)
59- 66 F8.5 --- z Redshift (3)
68- 73 F6.3 mag imag ? DES i-band magnitude
75- 79 F5.2 [Msun] logM* ? Logarith of the stellar mass (4)
81- 84 F4.2 [Msun] E_logM* ? Upper error on logM* (4)
86- 89 F4.2 [Msun] e_logM* ? Lower error on logM* (4)
91- 95 F5.1 arcsec Dtheta Projected distance to the lensing galaxy
97- 102 F6.2 [arcsec] logD3xZ ? Logarithm of the flexion shifts
calculated using the scaling relations by
Zahid et al. (2016ApJ...832..203Z 2016ApJ...832..203Z) (5)
104- 107 F4.2 [arcsec] E_logD3xZ ? Upper error on logD3xZ
109- 112 F4.2 [arcsec] e_logD3xZ ? Lower error on logD3xZ
114- 119 F6.2 [arcsec] logD3xA ? Logarithm of the flexion shifts
calculated using the scaling relations by
Auger et al. (2011MNRAS.411L...6A 2011MNRAS.411L...6A) (5)
121- 124 F4.2 [arcsec] E_logD3xA ? Upper error on logD3xA
126- 129 F4.2 [arcsec] e_logD3xA ? Lower error on logD3xA
--------------------------------------------------------------------------------
Note (1): DES Y3 galaxies have 9-digit IDs, DES Y1 galaxies have 10-digit IDs
Note (2): Flag as follows:
** = Galaxy has spurious MOF photometry. For these galaxies, we use
MAGAUTOCORRECTED photometry to calculate stellar masses instead
Note (3): Spectroscopic redshift uncertainties are about 100km/s, or 0.00033 in
redshift
Note (4): Stellar masses and corresponding uncertainties were calculated using
the Le PHARE galaxy template fitting code and DES Y3 photometry
(see Section 3.3 of the article)
Note (5): See Section 6.1 of the article for more details
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- System Name of the observed system
(DES J0408-5354 or WGD 2038-4008)
16- 23 A8 --- Group Galaxy group
25- 34 F10.6 deg RAdeg Right ascension (J2000)
36- 45 F10.6 deg DEdeg Declination (J2000)
47- 53 F7.5 --- z Redshift (1)
55- 60 F6.3 mag imag ? DES i-band magnitude
62- 75 A14 --- ID Galaxy identifier (2)
77- 81 A5 --- Memb Indicates whether that galaxy passes the
iterative group membership algorithm described
in Section 5.1
--------------------------------------------------------------------------------
Note (1): Spectroscopic redshift uncertainties are about 100km/s, or 0.00033 in
redshift
Note (2): Galaxies with DES Y3 IDs have 9 digits, while galaxies with DES Y1 IDs
have 10 digits. The lens galaxy is indicated as such, and galaxies
with spectroscopic redshifts from MUSE have IDs that begin with 'MUSE'
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- ID Cluster identifier
8- 12 F5.3 --- z Redshift
14- 18 F5.3 --- e_z Error on z
20- 23 F4.1 --- lambda Richness
25- 27 F3.1 --- e_lambda Error on lambda
29- 31 I3 km/s sigma Velocity dispersion
(rounded to the nearest 10km/s)
33- 34 I2 km/s E_sigma Upper error on sigma
36- 37 I2 km/s e_sigma Lower error on sigma
39- 47 F9.5 deg RAdeg Right ascension (J2000) of the group
centroid
49- 57 F9.5 deg DEdeg Declination (J2000) of the group centroid
59- 63 F5.1 arcsec Dtheta Projected distance of the centroid to the
lens
65- 68 F4.1 [arcsec] logD3x Logarithm of the flexion shift
(see Section 6.1 of the article)
70- 72 F3.1 [arcsec] E_logD3x Upper error on logD3x
74- 76 F3.1 [arcsec] e_logD3x Lower error on logD3x
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 07-Aug-2023