We have started a systematic search of strong lens candidates in the ESO
public survey KiDS based on the visual inspection of massive galaxies in the
redshift range $0.1<z<0.5$. As a pilot program we have inspected 100 sq. deg.,
which overlap with SDSS and where there are known lenses to use as a control
sample. Taking advantage of the superb image quality of VST/OmegaCAM, the
colour information and accurate model subtracted images, we have found 18 new
lens candidates, for which spectroscopic confirmation will be needed to confirm
their lensing nature and study the mass profile of the lensing galaxies.Comment: 4 pages, 1 figure, to appear on the refereed Proceeding of the "The
  Universe of Digital Sky Surveys" conference held at the INAF--OAC, Naples, on
  25th-28th november 2014, to be published on Astrophysics and Space Science
  Proceedings, edited by Longo, Napolitano, Marconi, Paolillo, Iodic

A.A. Dutton

A.S. Bolton

B. Moore

C. Alard

C. Tortora

F. Barbera La

J.B. Hyde

J.F. Navarro

J.T.A. Jong de

K.H. Chae

M. Oguri

O.Y. Gnedin

R. Gavazzi

R.S. Remus

English

arXiv

N. R. Napolitano

G. Covone

N. Roy

F. La Barbera

M. Radovich

F. Getman

M. Capaccioli

A. Colonna

M. Paolillo

G. A. Verdoes Kleijn

L. V. E. Koopmans

null null

Crossref

Strong Lens Search in the ESO Public Survey KiDS

We have started a systematic search for strong lens candidates in the ESO public survey KiDS based on the visual inspection of massive galaxies in the redshift range 0. 1 &lt; z &lt; 0. 5. As a pilot program we have inspected 100 deg2, which overlap with SDSS and where there are known lenses to use as a control sample. Taking advantage of the superb image quality of VST/OmegaCAM, the colour information and accurate model subtracted images, we have found 18 new lens candidates, for which spectroscopic confirmation will be needed to confirm their lensing nature and study the mass profile of the lensing galaxies

Napolitano, N. R.

Covone, G.

Roy, N.

Tortora, C.

Barbera, F. La

Radovich, M.

Getman, F.

Capaccioli, M.

Colonna, A.

Paolillo, M.

Kleijn, G. A. Verdoes

Koopmans, L. V. E.

ARTS repository - University of Groningen

Strong lens search in the ESO public Survey KiDS

Valentijn, E

University of Groningen Research Database

University of Groningen

We have started a systematic search for strong lens candidates in the ESO public survey KiDS based on the visual inspection of massive galaxies in the redshift range 0. 1 2, which overlap with SDSS and where there are known lenses to use as a control sample. Taking advantage of the superb image quality of VST/OmegaCAM, the colour information and accurate model subtracted images, we have found 18 new lens candidates, for which spectroscopic confirmation will be needed to confirm their lensing nature and study the mass profile of the lensing galaxies

NAPOLITANO, NICOLA ROSARIO

TORTORA, CRESCENZO

LA BARBERA, Francesco

RADOVICH, MARIO

GETMAN, FEDOR

Paolillo, Maurizio

Verdoes Kleijn, G. A.

OA@INAF - Istituto Nazionale di Astrofisica

2016Publication Year2021-01-07T16:05:47ZAcceptance in OA@INAFStrong Lens Search in the ESO Public Survey KiDSTitleNAPOLITANO, NICOLA ROSARIO; Covone, G.; Roy, N.; TORTORA, CRESCENZO; LA BARBERA, Francesco; et al.Authors10.1007/978-3-319-19330-4_20DOIhttp://hdl.handle.net/20.500.12386/29583HandleASTROPHYSICS AND SPACE SCIENCE PROCEEDINGSSeries42NumberChapter 20Strong Lens Search in the ESO Public SurveyKiDSN.R. Napolitano, G. Covone, N. Roy, C. Tortora, F. La Barbera, M. Radovich,F. Getman, M. Capaccioli, A. Colonna, M. Paolillo, G.A. Verdoes Kleijn,L.V.E. Koopmans, and the KiDS collaborationAbstract We have started a systematic search for strong lens candidates in the ESOpublic survey KiDS based on the visual inspection of massive galaxies in the redshiftrange 0:1 < z < 0:5. As a pilot program we have inspected 100 deg2, which overlapwith SDSS and where there are known lenses to use as a control sample. Takingadvantage of the superb image quality of VST/OmegaCAM, the colour informationand accurate model subtracted images, we have found 18 new lens candidates, forwhich spectroscopic confirmation will be needed to confirm their lensing nature andstudy the mass profile of the lensing galaxies.20.1 Dark Matter in Galaxy CoresThe dominant role of cold dark matter (CDM) in shaping structures in the Universeis now very well constrained and understood on the largest scales, but less on thescales of individual galaxy haloes. The assembly and evolution of CDM haloes canbe studied in detail with N-body simulations, which predict that the CDM densityprofile, CDM.r/, are well described by the so-called NFW profile with CDM.r/ /r3 in the outer regions, and CDM.r/ / r˛ , in the centre (with ˛ D 1, [15];N.R. Napolitano () • C. Tortora • F. La Barbera • F. GetmanINAF – Osservatorio Astronomico di Capodimonte, Salita Moiariello, 16, 80131, Napoli, Italye-mail: napolita@na.astro.itG. Covone • N. Roy • M. Capaccioli • A. Colonna • M. PaolilloDepartment of Physics “Ettore Pancini”, University “Federico II” of Naples, ItalyM. RadovichINAF – Osservatorio Astronomico di Padova-vicolo Osservatorio 5, 35122 Padova, ItalyG.A. Verdoes Kleijn • L.V.E. KoopmansKapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen,The NetherlandsKiDS collaboration: http://kids.strw.leidenuniv.nl/team.php© Springer International Publishing Switzerland 2016N.R. Napolitano et al. (eds.), The Universe of Digital Sky Surveys, Astrophysicsand Space Science Proceedings 42, DOI 10.1007/978-3-319-19330-4_20129130 N.R. Napolitano et al.˛ D 1:5 [14]). However, N-body simulations only follow the evolution of CDMparticles, not including the complex physics of gas and stars, which can alter theCDM profiles (e.g., via adiabatic contraction, [10] ).The study of the CDM profile in the inner regions of ETGs has received muchinterest, due to the large amount of available data samples (e.g., [11, 19]). However,it is made difficult by the degeneracy between the shape of the CDM profile and thatof the stellar Initial Mass Function (IMF; [7, 20].)20.2 Strong Lensing to Study the Mass Density of GalaxiesStrong lensing (SL hereafter) is an ideal tool to perform accurate studies of the CDMdistribution of intermediate and massive galaxies (e.g. with velocity dispersions,v > 180 km s1) independently of the dynamical status of the mass within thearc features. SL studies, often in combination with stellar dynamics in the galaxycentral regions, have found that the light and halo profiles conspire to have a totalmass density profile which is nearly isothermal [2, 3, 5, 12, 16], i.e. a total-massdensity slope of ˛  2. This “conspiracy”, once thought to be universal, has beenrecently found not to be so, as lower mass galaxies might have steeper ˛ [8, 21].The physical reasons for this systematic variation of the observed slope resides in theway baryons and CDM are mixed, after having been assembled over time [17]. Suchdetailed studies have been performed over samples of nearby early-type galaxies anda similar systematic study is ongoing at higher-z SL systems (e.g., by SLACS, [4];SL2S, [18]), where SL is much more effective than standard dynamical studies. Forthis reason it is becoming of fundamental importance to enlarge the sample of SLsystems both in the galaxy parameter space (e.g. toward less massive systems, likesub-L) and in redshift space.20.3 Why Galaxy-Galaxy SL in the ESO Public SurveyKiDS?The ESO public survey KiDS (Kilo Degree Survey, [6]) is a multi-band (ugri)imaging survey, designed to take advantage of the superb seeing of Paranal andhigh image quality of the VST/OmegaCAM. Its primary usage is weak lensingmeasurements over 1,500 deg2 of the sky.As such, KiDS is particularly suitable for a systematic census of lensing galaxiesbased on the identification of arc-like structure from intermediate to massivegalaxies (i.e., with velocity dispersion of the order of 200 km s1 or larger), togalaxy groups and galaxy clusters, thus covering a wide range of lens masses.Indeed, the Einstein ring writes easily as a function of the velocity dispersion as20 Strong Lens Search in the ESO Public Survey KiDS 131Fig. 20.1 Results from the visual inspection of SL candidates. Top rows show two high-confidencecandidates, bottom is a a less secure one. At each row we show: (1) RGB colour image, (2) rbandimage; (3) model subtracted image; (4) 2DPHOT galaxy model. In the top row, an Einstein ring isevident and shows up clearly in the residual image. In the middle row a blue arc is also evident inthe colour image and nicely spotted into the residual image. In the bottom row a faint blue arc isseen in the colour image in the bottom edge of the redder central galaxy, which shows up slightlyclearer in the model subtracted image. Estimated RE are 6–8 arcsecRE  100  .v=220 km s1/2, and for a typical FWHM  0:700 in r-band, we canexpect to observe lensing arcs of gravitational structures of v > 180 km s1.The search for SL in KiDS is expected to provide up to thousands galaxy rings(e.g. by extrapolating CFHT-LS numbers, [16]). This can be performed only with(semi-)automated techniques [1, 9], as potential candidates in KiDS can be ofthe order of thousands per square degree, making visual inspection inapplicable.However, lensing finding techniques still suffer from a number of issues yet to besolved, affecting the completeness and reliability of their catalogs and need to betrained over visually-inspected samples.20.4 Selection of SL Candidates via Visual InspectionDue to the yet limited extension of the area (150 deg2) included in the KiDS ESO-Data Release 2 (ESO-DR2), we have decided to start a visual search based onsimple criteria: (1) sources with SDSS spectroscopic redshifts between z D 0:1132 N.R. Napolitano et al.and z D 0:5 and (2) sources brighter than r D 20, which together maximisethe SL probability for the depth allowed by KiDS images. These criteria wererestrictive and biased toward larger RE easier to spot by visual inspection. In orderto quantify the performance of our search, we decided to start on some controlfields, overlapping with the SDSS, and selected 600 lens candidates in 100 deg2,including a ten of SLACS lenses.The visual inspection (performed by six observers) was based on (a) the galaxyrband image (rband is chosen as reference since it is the deepest and highestquality among KiDS wavebands), (b) a three-colour combined image to find agradient in colour between the candidate lens galaxy and the arc, (c) the 2DPHOTmodel [13] subtracted image to detect residual arc features. Examples of lenscandidates are in Fig. 20.1). Following this procedure, we ended up with a list of18 new potential lens candidates, half of which have high significance. We alsore-identified three SLACS lensing galaxies, while the other seven could not befound because arcs were too close to the galaxy centre to be uncovered. Due tothe peculiarity of the SLACS selection procedure (i.e. very compact Einstein radiifalling into the size of the SDSS spectra fiber, R  1:500) the fraction of the recoveredSLACS systems (i.e. 30 %) is a lower limit of the completeness of our selection.The spectroscopic follow-up will provide us with the confirmation of the lensingnature of the lens candidates and the independent kinematic information to constrainthe mass profile of the lensing galaxies.References1. Alard, C.: Gravitational arcs as a perturbation of the perfect ring. MNRAS 382, L58 (2007)2. Auger, M.W., Treu, T., Bolton, A.S., et al.: The Sloan Lens ACS Survey. X. Stellar, dynamical,and total mass correlations of massive early-type galaxies. ApJ 724, 511 (2010)3. Bolton, A.S., Burles, S., Koopmans, L.V.E., Treu, T., Moustakas, L.A.: Spectroscopicallyselected sample of massive early-type lens galaxies. ApJ 638, 703 (2006)4. Bolton, A.S., Burles, S., Koopmans, L.V.E., et al.: The Sloan Lens ACS Survey. V. The fullACS strong-lens sample. ApJ 682, 964 (2008)5. Chae, K.H., Bernardi, M., Kravtsov, A.V.: Modelling mass distribution in elliptical galaxies:mass profiles and their correlation with velocity dispersion profiles. MNRAS 437, 3670 (2014)6. de Jong, J.T.A., Kuijken, K., Applegate, D., et al.: The Kilo-Degree Survey. The Messenger154, 44 (2013)7. Dutton, A.A., Mendel, J.T., Simard, L.: Evidence for a non-universal stellar initial massfunction in low-redshift high-density early-type galaxies. MNRAS 422, L33 (2012)8. Dutton, A.A., Treu, T.: Elliptical galaxies: implications for the stellar initial mass function andhalo response to Baryonic processes. MNRAS 438, 3594 (2014)9. Gavazzi, R., Marshall, P.J., Treu, T., Sonnenfeld, A.: RINGFINDER: automated detectionof galaxy-scale gravitational lenses in ground-based multi-filter imaging data. ApJ 785, 144(2014)10. Gnedin, O.Y., Kravtsov, A.V., Klypin, A.A., Nagai, D.: Response of dark matter halos tocondensation of Baryons: cosmological simulations and improved adiabatic contraction model.ApJ 616, 16 (2004)11. Hyde, J.B., Bernardi, M.: The luminosity and stellar mass fundamental plane of early-typegalaxies. MNRAS 396, 1171 (2009)20 Strong Lens Search in the ESO Public Survey KiDS 13312. Koopmans, L.V.E., Treu, T., Bolton, A.S., Burles, S., Moustakas, L.A.: The Sloan Lens ACSSurvey. III. The structure and formation of early-type galaxies and their evolution since z  1.ApJ 649, 599 (2006)13. La Barbera, F., de Carvalho, R.R., Kohl-Moreira, J.L., et al.: 2DPHOT: a multi-purposeenvironment for the two-dimensional analysis of wide-field images. PASP 120, 681 (2008)14. Moore, B., Governato, F., Quinn, T., Stadel, J., Lake, G.: Resolving the structure of cold darkmatter halos. ApJl 499, L5 (1998)15. Navarro, J.F., Frenk, C.S., White, S.D.M.: The structure of cold dark matter halos. 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Strong lens search in the ESO public Survey KiDS

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