J/ApJ/850/94 Spectroscopy of the fields of gravitational lenses (Wilson+, 2017)
A spectroscopic survey of the fields of 28 strong gravitational lenses:
implications for H0.
Wilson M.L., Zabludoff A.I., Keeton C.R., Wong K.C., Williams K.A.,
French K.D., Momcheva I.G.
<Astrophys. J., 850, 94 (2017)>
=2017ApJ...850...94W 2017ApJ...850...94W
ADC_Keywords: Gravitational lensing; Spectra, optical; Redshifts;
Velocity dispersion
Keywords: galaxies: groups: general ; gravitational lensing: strong
Abstract:
Strong gravitational lensing provides an independent measurement of
the Hubble parameter (H0). One remaining systematic is a bias from
the additional mass due to a galaxy group at the lens redshift or
along the sightline. We quantify this bias for more than 20 strong
lenses that have well-sampled sightline mass distributions, focusing
on the convergence κ and shear γ. In 23% of these fields,
a lens group contributes ≥1% convergence bias; in 57%, there is a
similarly significant line-of-sight group. For the nine time-delay
lens systems, H0 is overestimated by 11-2+3% on average when
groups are ignored. In 67% of fields with total κ≥0.01,
line-of-sight groups contribute ≳2x more convergence than do lens
groups, indicating that the lens group is not the only important mass.
Lens environment affects the ratio of four (quad) to two (double)
image systems; all seven quads have lens groups while only 3 of 10
doubles do, and the highest convergences due to lens groups are in
quads. We calibrate the γ-κ relation:
log(κtot)=(1.94±0.34)log(γtot)+(1.31±0.49) with an
rms scatter of 0.34dex. Although shear can be measured directly from
lensed images, unlike convergence, it can be a poor predictor of
convergence; for 19% of our fields, κ is ≳2γ. Thus,
accurate cosmology using strong gravitational lenses requires precise
measurement and correction for all significant structures in each lens
field.
Description:
The lens sample selection is described in Momcheva+ (2015, J/ApJS/219/29).
For 26 of the 28 fields with the most complete spectroscopic data,
Wilson+ (2016, J/ApJ/833/194) created a group catalog including any
groups projected along the sightline to the lens as well as groups in
which the lens galaxy is itself a member. The properties of these 26
fields are listed in Table 1.
The Mosaic-1 imager on the Kitt Peak National Observatory Mayall 4m
telescope and the Mosaic II imager on the Cerro Tololo Inter-American
Observatory Blanco 4m telescope were used to collect images through
the "nearly Mould" I-band filter and either the Harris V filter or the
Harris R filter (depending on the redshift of the lens galaxy).
The spectra were obtained using Hectospec on the MMT 6.5m telescope
and LDSS-2, LDSS-3, and IMACS on the Magellan 6.5m telescopes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 94 26 Lens systems
table3.dat 136 328 Lensing properties of groups
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See also:
J/AJ/112/407 : The FIRST bright QSO survey (Gregg+, 1996)
J/ApJ/496/39 : Properties of poor groups of galaxies. I. (Zabludoff+ 1998)
J/A+A/358/77 : Hamburg/ESO survey for bright QSOs. III. (Wisotzki+, 2000)
J/ApJ/641/169 : Spectroscopy in lens fields (Momcheva+, 2006)
J/ApJ/730/119 : HST/WFC3 obs. of Cepheids in SN Ia hosts (Riess+, 2011)
J/ApJ/781/2 : Redshifts of 1151 galaxies from SDSS (Ammons+, 2014)
J/ApJS/219/29 : Spectrosc. redshifts in strong lens fields (Momcheva+, 2015)
J/ApJ/833/194 : Group of gal. in gravitational lens fields (Wilson+, 2016)
J/MNRAS/465/4914 : R-band light curves of HE 0435-1223 (Bonvin+, 2017)
http://www.cfa.harvard.edu/castles : The gravitational lens data base
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Field Field designation
10- 17 F8.4 deg RAdeg [12.4/328.1] Lens right ascension (J2000)
19- 26 F8.4 deg DEdeg [-47.4/53] Lens declination (J2000)
28 A1 --- f_pos Flag on coordinates (1)
30- 35 F6.4 --- zL Lens redshift
36 A1 --- f_zL Flag on zL (1)
38- 42 F5.3 --- zS ? Redshift of the source
43 A1 --- f_zS Flag on zS (1)
45- 50 F6.4 --- zS2 ? Second source redshift
51 A1 --- f_zS2 Flag on zS2 (1)
53- 55 A3 --- Img Image number and type from CASTLES (2)
57- 60 F4.2 arcsec Size [0.7/3.8] Size estimates of twice the average
Einstein radius from CASTLES
62 I1 --- n_Size [0/3]? Size type from CASTLES (3)
64- 65 I2 --- Ngr [6/55]? Number of group member
from Wilson+ (2016, J/ApJ/833/194)
67- 72 F6.4 --- zGr [0.2/0.7]? Lens group redshift
from Wilson+ (2016, J/ApJ/833/194)
74- 77 F4.2 arcmin R [0.1/6]? Projected angular distance between the
lens and the group centroid
from Wilson+ (2016, J/ApJ/833/194)
79- 81 I3 km/s Sig [110/800]? Lens group velocity dispersion
from Wilson+ (2016, J/ApJ/833/194)
83- 85 I3 km/s e_Sig [20/530]? Sig negative uncertainty
87- 89 I3 km/s E_Sig [20/140]? Sig positive uncertainty
91- 94 F4.2 --- rVir [0.2/1.6]? Lens group virial radius
from Wilson+ (2016, J/ApJ/833/194)
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Note (1): Flag as follows:
f = Photometric redshift from Kneib+ (1998A&A...339L..65K 1998A&A...339L..65K).
g = From CASTLES (http://www.cfa.harvard.edu/castles/).
h = Photometric redshift from CASTLES.
i = Photometric redshift from Kochanek+ (2000ApJ...535..692K 2000ApJ...535..692K).
j = Spectroscopic redshift from Chavushyan+ (1997A&A...318L..67C 1997A&A...318L..67C).
k = Spectroscopic redshift from Auger+ (2008ApJ...673..778A 2008ApJ...673..778A).
Note (2): From CASTLES (http://www.cfa.harvard.edu/castles/):
Number = Number of images, R = Einstein ring, and E = Extended.
Note (3): Type as follows:
0 = Literature estimate,
1 = Maximum image pair separation,
2 = Twice average distance from lens center to images,
3 = Twice an SIS model's critical radius plus external shear.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Field Field identifier
10- 44 A35 --- Group Group identifier (1)
46- 46 A1 --- f_Group [ef*] Flag on Group (2)
48- 50 I3 --- Nm [3/230]? Number of members (3)
52- 57 F6.4 --- zGr [0.02/0.8]? Group redshift (3)
59- 64 F6.4 --- E_zGr [0/0.003]? Upper uncertainty in zgrp
66- 71 F6.4 --- e_zGr [0/0.002]? Lower uncertainty in zgrp
73- 76 I4 km/s Sig [20/1200]? Group velocity dispersion
78- 80 I3 km/s E_Sig [10/710]? Upper uncertainty in sigmagrp
82- 84 I3 km/s e_Sig [0.2/570]? Lower uncertainty in sigmagrp
86- 89 F4.1 arcmin R [0.001/18]? Projected distance (4)
91- 95 F5.3 --- kappaeff [0/0.5]? Effective convergence κeff
97-102 F6.4 --- E_kappaeff [0/0.3]? Upper uncertainty in kappaeff
104-109 F6.4 --- e_kappaeff [0/0.2]? Lower uncertainty in kappaeff
111-115 F5.3 --- gammaeff [0.001/0.3]? Effective shear γeff
117-122 F6.4 --- E_gammaeff [0.0002/0.09]? Upper uncertainty in gammaeff
124-131 F8.6 --- e_gammaeff [0/0.06]? Lower uncertainty in gammaeff
133-136 I4 deg theta [-177/180]? Position angle (5)
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Note (1): Numbering as in Wilson+ (2016, J/ApJ/833/194).
Note (2): Flag as follows:
e = Supergroup;
f = Main substructures of the supergroup.
* = lens group
Note (3): From Wilson+ (2016, J/ApJ/833/194). Uncertainties in group properties
other than number of member galaxies are provided for groups with at
least four members.
Note (4): Projected distance between the group projected spatial centroid
and the lens from Wilson+ (2016, J/ApJ/833/194).
Note (5): Measured north through east between the group projected
spatial centroid and the lens.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 27-Jun-2018