arXiv subjects

Adi Zitrin

Publications and source records attributed to Adi Zitrin.

At least 199 records · Page 11Linked to original sources

arXiv2018

A Candidate $z\sim10$ Galaxy Strongly Lensed into a Spatially Resolved Arc

The most distant galaxies known are at z~10-11, observed 400-500 Myr after the Big Bang. The few z~10-11 candidates discovered to date have been exceptionally small- barely resolved, if at all, by the Hubble Space Telescope. Here we present the discovery of SPT0615-JD, a fortuitous z~10 (z_phot=9.9+/-0.6) galaxy candidate stretched into an arc over ~2.5" by the effects of strong gravitational lensing. Discovered in the Reionization Lensing Cluster Survey (RELICS) Hubble Treasury program and companion S-RELICS Spitzer program, this candidate has a lensed H-band magnitude of 25.7+/-0.1 AB mag. With a magnification of μ~4-7 estimated from our lens models, the de-lensed intrinsic magnitude is 27.6+/-0.3 AB mag, and the half-light radius is r_e<0.8 kpc, both consistent with other z>9 candidates. The inferred stellar mass (log [M* /M_Sun]=9.7^{+0.7}_{-0.5}) and star formation rate (\log [SFR/M_Sun yr^{-1}]=1.3^{+0.2}_{-0.3}) indicate that this candidate is a typical star-forming galaxy on the z>6 SFR-M* relation. We note that three independent lens models predict two counterimages, at least one of which should be of a similar magnitude to the arc, but these counterimages are not yet detected. Counterimages would not be expected if the arc were at lower redshift. However, the only spectral energy distributions capable of fitting the Hubble and Spitzer photometry well at lower redshifts require unphysical combinations of z~2 galaxy properties. The unprecedented lensed size of this z~10 candidate offers the potential for the James Webb Space Telescope to study the geometric and kinematic properties of a galaxy observed 500 Myr after the Big Bang.

astro-ph.GA↗

arXiv2018

MUSE spectroscopy and deep observations of a unique compact JWST target, lensing cluster CLIO

We present the results of a VLT MUSE/FORS2 and Spitzer survey of a unique compact lensing cluster CLIO at z = 0.42, discovered through the GAMA survey using spectroscopic redshifts. Compact and massive clusters such as this are understudied, but provide a unique prospective on dark matter distributions and for finding background lensed high-z galaxies. The CLIO cluster was identified for follow up observations due to its almost unique combination of high mass and dark matter halo concentration, as well as having observed lensing arcs from ground based images. Using dual band optical and infra-red imaging from FORS2 and Spitzer, in combination with MUSE optical spectroscopy we identify 89 cluster members and find background sources out to z = 6.49. We describe the physical state of this cluster, finding a strong correlation between environment and galaxy spectral type. Under the assumption of a NFW profile, we measure the total mass of CLIO to be M$_{200} = (4.49 \pm 0.25) \times 10^{14}$ M$_\odot$. We build and present an initial strong-lensing model for this cluster, and measure a relatively low intracluster light (ICL) fraction of 7.21 $\pm$ 1.53% through galaxy profile fitting. Due to its strong potential for lensing background galaxies and its low ICL, the CLIO cluster will be a target for our 110 hour JWST 'Webb Medium-Deep Field' (WMDF) GTO program.

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arXiv2017

A spectroscopic search for AGN activity in the reionization era

The ubiquity of Lyman alpha (Ly$α$) emission in a sample of four bright [O III]-strong star-forming galaxies with redshifts above 7 has led to the suggestion that such luminous sources represent a distinct population compared to their fainter, more numerous, counterparts. The presence of Ly$α$ emission within the reionization era could indicate that these sources created early ionized bubbles due to their unusually strong radiation, possibly due to the presence of active galactic nuclei. To test this hypothesis we have secured long integration spectra with XSHOOTER on the VLT for three $z\simeq$7 sources selected to have similar luminosities and prominent excess fluxes in the IRAC 3.6 or 4.5$μ$m band, usually attributed to strong [O III] emission. We secured additional spectroscopy for one of these galaxies at $z$=7.15 using MOSFIRE at the Keck telescope. For this, the most well-studied source in our sample with the strongest IRAC excess, we detect prominent nebular emission from He II and NV indicative of a non-thermal source. For the other two sources at $z$=6.81 and $z$=6.85, for which no previous optical/near infrared spectroscopy was initially available, Ly$α$ is seen in one and CIII] emission in the other. Although a modest sample, our results further support the hypothesis that the phenomenon of intense [O III] emission is associated preferentially with sources lying in early ionized bubbles. However, even though one of our sources at $z$=7.15 clearly indicates the presence of non-thermal radiation, such ionized bubbles may not uniquely arise in this manner. We discuss the unique advantages of extending such challenging diagnostic studies with JWST.

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arXiv2017

Strong Lensing Analysis of the Powerful Lensing Cluster MACS J2135.2-0102 ($z$=0.33)

We present a light-traces-mass (LTM) strong-lensing model of the massive lensing cluster MACS J2135.2-0102 ($z$=0.33; hereafter MACS2135), known in part for hosting the Cosmic Eye galaxy lens. MACS2135 is also known to multiply-lens a $z=$2.3 sub-mm galaxy near the Brightest Cluster Galaxy (BCG), as well as a prominent, triply-imaged system at a large radius of $\sim$37" south of the BCG. We use the latest available Hubble imaging to construct an accurate lensing model for this cluster, identifying six new multiply-imaged systems with the guidance of our LTM method, so that we have roughly quadrupled the number of lensing constraints. We determine that MACS2135 is amongst the top lensing clusters known, comparable in size to the Hubble Frontier Fields. For a source at $z_{s}=2.32$, we find an effective Einstein radius of $θ_{e}=27\pm3$", enclosing $1.12 \pm0.16 \times10^{14}$ $M_{\odot}$. We make our lens model, including mass and magnification maps, publicly available, in anticipation of searches for high-$z$ galaxies with the James Webb Space Telescope for which this cluster is a compelling target.

astro-ph.CO↗

arXiv2017

Strong Lensing Analysis of the Galaxy Cluster MACS J1319.9+7003 and the Discovery of a Shell Galaxy

We present a strong-lensing (SL) analysis of the galaxy cluster MACS J1319.9+7003 ($z=0.33$, also known as Abell 1722), as part of our ongoing effort to analyze massive clusters with archival {\it HST} imaging. We spectroscopically measured with Keck/MOSFIRE two galaxies multiply-imaged by the cluster. Our analysis reveals a modest lens, with an effective Einstein radius of $θ_{e}(z=2)=12\pm1$", enclosing $2.1\pm0.3\times10^{13}$ $M_{\odot}$. We briefly discuss the SL properties of the cluster, using two different modeling techniques, and make the mass models publicly-available\footnote{ftp://wise-ftp.tau.ac.il/pub/adiz/MACS1319/}. Independently, we identified a noteworthy, young Shell Galaxy (SG) system forming around two likely interacting cluster members, 20" north of the BCG. SGs are rare in galaxy clusters, and indeed, a simple estimate yields that they are only expected in roughly one in several dozen, to several hundred, massive galaxy clusters (the estimate can easily change by an order-of-magnitude within a reasonable range of characteristic values relevant for the calculation). Taking advantage of our lens model best-fit, mass-to-light scaling relation for cluster members, we infer that the total mass of the SG system is $\sim1.3\times10^{11}$ M$_{\odot}$, with a host-to-companion mass ratio of about 10:1. Despite being rare in high density environments, the SG constitutes an example to how stars of cluster galaxies are being efficiently redistributed to the Intra Cluster Medium. Dedicated numerical simulations for the observed shell configuration, perhaps aided by the mass model, might cast interesting insight on the interaction history and properties of the two galaxies. An archival HST search in galaxy cluster images can reveal more such systems.

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arXiv2017

A Very Large ($θ_{E}\gtrsim40$") Strong Gravitational Lens Selected with the Sunyaev-Zel'dovich Effect: PLCK G287.0+32.9 ($z$ = 0.38)

Since galaxy clusters sit at the high-end of the mass function, the number of galaxy clusters both massive and concentrated enough to yield particularly large Einstein radii poses useful constraints on cosmological and structure formation models. To date, less than a handful of clusters are known to have Einstein radii exceeding $\sim40$" (for a source at $z_{s}\simeq2$, nominally). Here, we report an addition to that list of the Sunyaev-Zel'dovich (SZ) selected cluster, PLCK G287.0+32.9 ($z=0.38$), the second-highest SZ-mass ($M_{500}$) cluster from the Planck catalog. We present the first strong lensing analysis of the cluster, identifying 20 sets of multiply-imaged galaxies and candidates in new \emph{Hubble Space Telescope} data, including a long, $l\sim22$" giant arc, as well as a quadruply-imaged, apparently bright (magnified to J$_{F110W}=$25.3 AB), likely high-redshift dropout galaxy at $z_{phot}=6.90$ [6.13--8.43] (95\% C.I.). Our analysis reveals a very large critical area (1.55 arcmin$^{2}$, $z_{s}\simeq2$), corresponding to an effective Einstein radius of $θ_{E}\sim42$". The model suggests the critical area will expand to 2.58 arcmin$^{2}$ ($θ_{E}\sim54$") for sources at $z_{s}\sim10$. Our work adds to recent efforts to model very massive clusters towards the launch of the James Webb Space Telescope, in order to identify the most useful cosmic lenses for studying the early Universe. Spectroscopic redshifts for the multiply-imaged galaxies and additional HST data will be necessary for refining the lens model and verifying the nature of the $z\sim7$ dropout.

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arXiv2017

CLUMP-3D. Three dimensional lensing and multi-probe analysis of MACS J1206.2-0847, a remarkably regular cluster

Multi-wavelength techniques can probe the distribution and the physical properties of baryons and dark matter in galaxy clusters from the inner regions out to the peripheries. We present a full three-dimensional analysis combining strong and weak lensing, X-ray surface brightness and temperature, and the Sunyaev-Zel'dovich effect. The method is applied to MACS J1206.2-0847, a remarkably regular, face-on, massive, M_{200}=(1.1+-0.2)*10^{15}M_Sun/h, cluster at z=0.44. The measured concentration, c_{200}=6.3+-1.2, and the triaxial shape are common to halos formed in a LCDM scenario. The gas has settled in and follows the shape of the gravitational potential, which is evidence of pressure equilibrium via the shape theorem. There is no evidence for significant non-thermal pressure and the equilibrium is hydrostatic.

astro-ph.CO↗

arXiv2016

Constraints on the Mass, Concentration, and Nonthermal Pressure Support of Six CLASH Clusters from a Joint Analysis of X-ray, SZ, and Lensing Data

We present a joint analysis of Chandra X-ray observations, Bolocam thermal Sunyaev-Zel'dovich (SZ) effect observations, Hubble Space Telescope (HST) strong lensing data, and HST and Subaru Suprime-Cam weak lensing data. The multiwavelength dataset is used to constrain parametric models for the distribution of dark and baryonic matter in a sample of six massive galaxy clusters selected from the Cluster Lensing And Supernova survey with Hubble (CLASH). For five of the six clusters, the multiwavelength dataset is well described by a relatively simple model that assumes spherical symmetry, hydrostatic equilibrium, and entirely thermal pressure support. The joint analysis yields considerably better constraints on the total mass and concentration of the cluster compared to analysis of any one dataset individually. The subsample of five galaxy clusters is used to place an upper limit on the fraction of pressure support in the intracluster medium (ICM) due to nonthermal processes, such as turbulence and bulk flow of the gas. We constrain the nonthermal pressure fraction at r500c to be less than 0.11 at 95 percent confidence. This is in tension with state-of-the-art hydrodynamical simulations, which predict a nonthermal pressure fraction of approximately 0.25 at r500c for clusters of similar mass and redshift. This tension may be explained by the sample selection and/or our assumption of spherical symmetry.

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arXiv2016

Geometric Corroboration of the Earliest Lensed Galaxy at z~10.8 from Robust Free-Form Modelling

A multiply-lensed galaxy, MACS0647-JD, with a probable photometric redshift of $z\simeq 10.7^{+0.6}_{-0.4}$ is claimed to constitute one of the very earliest known galaxies, formed well before reionization was completed. However, spectral evidence that MACS0647-JD lies at high redshift has proven infeasible and so here we seek an independent lensing based "geometric redshift" derived from the angles between the three lensed images of MACS0647-JD, using our free-form mass model (WSLAP+) for the lensing cluster MACSJ0647.7+7015 (at $z=0.591$). Our lens model uses the 9 sets of multiple images, including those of MACS0647-JD, identified by the CLASH survey towards this cluster. We convincingly exclude the low redshift regime of $z<3$, for which convoluted critical curves are generated by our method, as the solution bends to accommodate the wide angles of MACS0647-JD for this low redshift. Instead, a best fit to all sets of lensed galaxy positions and redshifts provides a geometric redshift of $z\simeq 10.8^{+0.3}_{-0.4}$ for MACS0647-JD, strongly supporting the higher photometric redshift solution. Importantly, we find a tight linear relation between the relative brightnesses of all 9 sets of multiply lensed images and their relative magnifications as predicted by our model. This agreement provides a benchmark for the quality of the lens model, and establishes the robustness of our free-form lensing method for measuring model-independent geometric source distances and for deriving objective central cluster mass distributions. After correcting for its magnification the luminosity of MACS0647-JD remains relatively high at $M_{UV}=-19.4$, which is within a factor of a few in flux of some surprisingly luminous $z\simeq 10$--$11$ candidates discovered recently in Hubble black field surveys.

astro-ph.CO↗

arXiv2016

A Multiply-Imaged z $\sim$ 6.3 Lyman Alpha Emitter candidate behind Abell 2261

While the Lyman-$α$ ($\mathrm{Ly}α$) emission line serves as an important tool in the study of galaxies at $z\lesssim 6$, finding Ly$α$ emitters (LAE) at significantly higher redshifts has been more challenging, probably because of the increasing neutrality of the intergalactic medium above $z\sim6$. Galaxies with extremely high rest-frame Ly$α$ equivalent widths, EW(Ly$α$) $\gtrsim 150$ Å, at $z>6$ are good candidates for Ly$α$ follow-up observations, and can stand out in multiband imaging surveys because of their unusual colors. We have conducted a photometric search for such objects in the Cluster Lensing And Supernova survey with Hubble (CLASH), and report here the identification of three likely gravitationally-lensed images of a single LAE candidate at $z\sim6.3$, behind the galaxy cluster Abell 2261($z = 0.225$). In the process, we also measured with Keck/MOSFIRE the first spectroscopic redshift of a multiply-imaged galaxy behind Abell 2261, at $z = 3.337$. This allows us to calibrate the lensing model, which in turn is used to study the properties of the candidate LAE. Population III galaxy spectral energy distribution (SED) model fits to the CLASH broadband photometry of the possible LAE provide a slightly better fit than Population I/II models. The best fitted model suggests intrinsic EW(Ly$α$) $\approx 160$ Å after absorption in the interstellar and intergalactic medium. Future spectroscopic observations will examine this prediction as well as shed more light on the morphology of this object, which indicates it may be a merger of two smaller galaxies.

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arXiv2016

Absorption Line Spectroscopy of Gravitationally-Lensed Galaxies: Further Constraints on the Escape Fraction of Ionizing Photons at High Redshift

The fraction of ionizing photons escaping from high-redshift star-forming galaxies remains a key obstacle in evaluating whether galaxies were the primary agents of cosmic reionization. We previously proposed using the covering fraction of low-ionization gas, measured via deep absorption line spectroscopy, as a proxy. We now present a significant update, sampling seven gravitationally-lensed sources at $4<z<5$. We show that the absorbing gas in our sources is spatially inhomogeneous with a median covering fraction of 66\%. Correcting for reddening according to a dust-in-cloud model, this implies an estimated absolute escape fraction of $\simeq19\pm6$\%. With possible biases and uncertainties, collectively we find the average escape fraction could be reduced to no less than 11\%, excluding the effect of spatial variations. For one of our lensed sources, we have sufficient signal/noise to demonstrate the presence of such spatial variations and scatter in its dependence on the Ly$α$ equivalent width, consistent with recent simulations. If this source is typical, our lower limit to the escape fraction could be reduced by a further factor $\simeq$2. Across our sample, we find a modest anti-correlation between the inferred escape fraction and the local star formation rate, consistent with a time delay between a burst and leaking Lyman continuum photons. Our analysis demonstrates considerable variations in the escape fraction consistent with being governed by the small-scale behavior of star-forming regions, whose activities fluctuate over short timescales. This supports the suggestion that the escape fraction may increase toward the reionization era when star formation becomes more energetic and burst-like.

astro-ph.GA↗

arXiv2016

Lyman-alpha and CIII] Emission in z=7-9 Galaxies: Accelerated Reionization Around Luminous Star Forming Systems?

We discuss new Keck/MOSFIRE spectroscopic observations of four luminous galaxies at z~7-9 selected to have intense optical line emission by Roberts-Borsani et al. (2016). Previous follow-up has revealed Lyman-alpha in two of the four galaxies. Our new MOSFIRE observations confirm that Lyman-alpha is present in the entire sample. We detect Lyman-alpha emission in COS-zs7-1, confirming its redshift as z=7.154, and we detect Lyman-alpha in EGS-zs8-2 at z=7.477, verifying a tentative detection presented in an earlier study. The ubiquity of Lyman-alpha in this sample is puzzling given that the IGM is likely significantly neutral over 7 7 is expected to be strongly luminosity-dependent, with the most effective transmission occurring in systems with intense star formation.

astro-ph.GA↗

arXiv2016

CLASH: Joint Analysis of Strong-Lensing, Weak-Lensing Shear and Magnification Data for 20 Galaxy Clusters

We present a comprehensive analysis of strong-lensing, weak-lensing shear and magnification data for a sample of 16 X-ray-regular and 4 high-magnification galaxy clusters selected from the CLASH survey. Our analysis combines constraints from 16-band HST observations and wide-field multi-color imaging taken primarily with Subaru/Suprime-Cam. We reconstruct surface mass density profiles of individual clusters from a joint analysis of the full lensing constraints, and determine masses and concentrations for all clusters. We find internal consistency of the ensemble mass calibration to be $\le 5\% \pm 6\%$ by comparison with the CLASH weak-lensing-only measurements of Umetsu et al. For the X-ray-selected subsample, we examine the concentration-mass relation and its intrinsic scatter using a Bayesian regression approach. Our model yields a mean concentration of $c|_{z=0.34} = 3.95 \pm 0.35$ at $M_{200c} \simeq 14\times 10^{14}M_\odot$ and an intrinsic scatter of $σ(\ln c_{200c}) = 0.13 \pm 0.06$, in excellent agreement with LCDM predictions when the CLASH selection function based on X-ray morphological regularity and the projection effects are taken into account. We also derive an ensemble-averaged surface mass density profile for the X-ray-selected subsample by stacking their individual profiles. The stacked mass profile is well described by a family of density profiles predicted for cuspy dark-matter-dominated halos, namely, the NFW, Einasto, and DARKexp models, whereas the single power-law, cored isothermal and Burkert density profiles are disfavored by the data. We show that cuspy halo models that include the two-halo term provide improved agreement with the data. For the NFW halo model, we measure a mean concentration of $c_{200c} = 3.79^{+0.30}_{-0.28}$ at $M_{200c} = 14.1^{+1.0}_{-1.0}\times 10^{14}M_\odot$, demonstrating consistency between complementary analysis methods.

astro-ph.CO↗

arXiv2016

A Keck Survey of Gravitationally-Lensed Star-Forming Galaxies: High Spatial Resolution Studies of Kinematics and Metallicity Gradients

We discuss spatially resolved emission line spectroscopy secured for a total sample of 15 gravitationally lensed star-forming galaxies at a mean redshift of $z\simeq2$ based on Keck laser-assisted adaptive optics observations undertaken with the recently-improved OSIRIS integral field unit (IFU) spectrograph. By exploiting gravitationally lensed sources drawn primarily from the CASSOWARY survey, we sample these sub-L$^{\ast}$ galaxies with source-plane resolutions of a few hundred parsecs ensuring well-sampled 2-D velocity data and resolved variations in the gas-phase metallicity. Such high spatial resolution data offers a critical check on the structural properties of larger samples derived with coarser sampling using multiple-IFU instruments. We demonstrate how kinematic complexities essential to understanding the maturity of an early star-forming galaxy can often only be revealed with better sampled data. Although we include four sources from our earlier work, the present study provides a more representative sample unbiased with respect to emission line strength. Contrary to earlier suggestions, our data indicates a more diverse range of kinematic and metal gradient behavior inconsistent with a simple picture of well-ordered rotation developing concurrently with established steep metal gradients in all but merging systems. Comparing our observations with the predictions of hydrodynamical simulations suggests that gas and metals have been mixed by outflows or other strong feedback processes, flattening the metal gradients in early star-forming galaxies.

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arXiv2016

The Structure of the Strongly Lensed Gamma-ray Source B2 0218+35

Strong gravitational lensing is a powerful tool for resolving the high energy universe. We combine the temporal resolution of Fermi-LAT, the angular resolution of radio telescopes, and the independently and precisely known Hubble constant from Planck, to resolve the spatial origin of gamma-ray flares in the strongly lensed source B2 0218+35. The lensing model achieves 1 milliarcsecond spatial resolution of the source at gamma-ray energies. The data imply that the gamma-ray flaring sites are separate from the radio core: the bright gamma-ray flare (MJD: 56160 - 56280) occurred $51\pm8$ pc from the 15 GHz radio core, toward the central engine. This displacement is significant at the $\sim3σ$ level, and is limited primarily by the precision of the Hubble constant. B2 0218+35 is the first source where the position of the gamma-ray emitting region relative to the radio core can be resolved. We discuss the potential of an ensemble of strongly lensed high energy sources for elucidating the physics of distant variable sources based on data from Chandra and SKA.

astro-ph.HE↗

arXiv2016

The Morphologies and Alignments of Gas, Mass, and the Central Galaxies of CLASH Clusters of Galaxies

Morphology is often used to infer the state of relaxation of galaxy clusters. The regularity, symmetry, and degree to which a cluster is centrally concentrated inform quantitative measures of cluster morphology. The Cluster Lensing and Supernova survey with Hubble Space Telescope (CLASH) used weak and strong lensing to measure the distribution of matter within a sample of 25 clusters, 20 of which were deemed to be relaxed based on their X-ray morphology and alignment of the X-ray emission with the BCG. Towards a quantitative characterization of this important sample of clusters, we present uniformly estimated X-ray morphological statistics for all 25 CLASH clusters. We compare X-ray morphologies of CLASH clusters with those identically measured for a large sample of simulated clusters from the MUSIC-2 simulations, selected by mass. We confirm a threshold in X-ray surface brightness concentration of C>0.4 for cool-core clusters, where C is the ratio of X-ray emission inside 100 kpc/h70 compared to inside 500 kpc/h70. We report and compare morphologies of these clusters inferred from Sunyaev-Zeldovich Effect (SZE) maps of the hot gas and in from projected mass maps based on strong and weak lensing. We find a strong agreement in alignments of the orientation of major axes for the lensing, X-ray, and SZE maps of nearly all of the CLASH clusters at radii of 500 kpc (approximately 0.5R500 for these clusters). We also find a striking alignment of clusters shapes at the 500 kpc scale, as measured with X-ray, SZE, and lensing, with that of the near-infrared stellar light at 10 kpc scales for the 20 "relaxed" clusters. This strong alignment indicates a powerful coupling between the cluster- and galaxy-scale galaxy formation processes.

astro-ph.CO↗

arXiv2015

A Free-Form Prediction for the Reappearance of Supernova Refsdal in the Hubble Frontier Fields Cluster MACSJ1149.5+2223

The massive cluster MACSJ1149.5+2223(z=0.544) displays five very large lensed images of a well resolved spiral galaxy at $z_{\rm spect}=1.491$. It is within one of these images that the first example of a multiply-lensed supernova has been detected recently as part of the Grism Lens-Amplified Survey from Space. The depth of this data also reveals many HII regions within the lensed spiral galaxy which we identify between the five counter-images. Here we expand the capability of our free-form method to incorporate these HII regions locally, with other reliable lensed galaxies added for a global solution. This improved accuracy allows us to estimate when the Refsdal supernova will appear within the other lensed images of the spiral galaxy to an accuracy of $\sim$ 7\%. We predict this supernova will reappear in one of the counter-images (RA=11:49:36.025, DEC=+22:23:48.11, J2000) and on November 1$^{st}$ 2015 (with an estimated error of $\pm$ 25 days) it will be at the same phase as it was when it was originally discovered, offering a unique opportunity to study the early phases of this supernova and to examine the consistency of the mass model and the cosmological model that have an impact on the time delay prediction.

astro-ph.CO↗

arXiv2015

The Detection and Statistics of Giant Arcs Behind CLASH Clusters

We developed an algorithm to find and characterize gravitationally lensed galaxies (arcs) to perform a comparison of the observed and simulated arc abundance. Observations are from the Cluster Lensing And Supernova survey with Hubble (CLASH). Simulated CLASH images are created using the MOKA package and also clusters selected from the high resolution, hydrodynamical simulations, MUSIC, over the same mass and redshift range as the CLASH sample. The algorithm' s arc elongation accuracy, completeness and false positive rate are determined and used to compute an estimate of the true arc abundance. We derive a lensing efficiency of $4 \pm 1$ arcs (with length $\ge 6"$ and length-to-width ratio $\ge 7$) per cluster for the X-ray selected CLASH sample, $4 \pm 1$ arcs per cluster for the MOKA simulated sample and $3 \pm 1$ arcs per cluster for the MUSIC simulated sample. The observed and simulated arc statistics are in full agreement. We measure the photometric redshifts of all detected arcs and find a median redshift $z_s = 1.9$ with 33% of the detected arcs having $z_s > 3$. We find that the arc abundance does not depend strongly on the source redshift distribution but is sensitive to the mass distribution of the dark matter halos (e.g. the $c-M$ relation). Our results show that consistency between the observed and simulated distributions of lensed arc sizes and axial ratios can be achieved by using cluster-lensing simulations that are carefully matched to the selection criteria used in the observations.

astro-ph.CO↗