Elinor Medezinski - Profile on Academia.edu (original) (raw)

Papers by Elinor Medezinski

The Astrophysical Journal

We derive an accurate mass distribution of the galaxy cluster MACS J1206.2-0847 (z=0.439) from a ... more We derive an accurate mass distribution of the galaxy cluster MACS J1206.2-0847 (z=0.439) from a combined weak-lensing distortion, magnification, and strong-lensing analysis of wide-field Subaru BVRIz' imaging and our recent 16-band Hubble Space Telescope observations taken as part of the Cluster Lensing And Supernova survey with Hubble (CLASH) program. We find good agreement in the regions of overlap between several weak and strong lensing mass reconstructions using a wide variety of modeling methods, ensuring consistency. The Subaru data reveal the presence of a surrounding large scale structure with the major axis running approximately north-west south-east (NW-SE), aligned with the cluster and its brightest galaxy shapes, showing elongation with a \sim 2:1 axis ratio in the plane of the sky. Our full-lensing mass profile exhibits a shallow profile slope dln\Sigma/dlnR\sim -1 at cluster outskirts (R>1Mpc/h), whereas the mass distribution excluding the NW-SE excess regions ...

The Concentration-Mass Relation from CLASH clusters using galaxy dynamics

ABSTRACT Galaxy clusters play a key role in testing cosmological models and in constraining the p... more ABSTRACT Galaxy clusters play a key role in testing cosmological models and in constraining the properties of dark matter. One of these key tests is the mass density profile of clusters - the concentration-mass relation. There is a reported tension between the observed concentration-mass relation and the one theoretically expected using simulated galaxy clusters, where the observed clusters appear to have higher concentration than simulated clusters of similar total mass. In The Cluster Lensing And Supernova survey with Hubble (CLASH), we use different and independent techniques to estimate the mass distribution in clusters. The comparison between different techniques offers an observational test of the techniques and understanding of the systematics. In this work, we estimate the concentration-mass relation for about 8 (at the 0.2< z &;lt; 0.6 redshift range) of the 20 X-ray selected CLASH clusters using galaxy dynamics. We use a unique spectroscopic data set with more than about 300 cluster members per cluster. Finally, we compare our results to the theoretical expected ones and to the estimations derived using the lensing technique.

The Astrophysical Journal, 2015

We utilize the CLASH (Cluster Lensing And Supernova survey with Hubble) observations of 25 cluste... more We utilize the CLASH (Cluster Lensing And Supernova survey with Hubble) observations of 25 clusters to search for extreme emission-line galaxies (EELGs). The selections are carried out in two central bands: F105W (Y 105 ) and F125W (J 125 ), as the flux of the central bands could be enhanced by the presence of [O III] λλ4959, 5007 at redshift of ∼ 0.93 − 1.14 and 1.57 − 1.79, respectively. The multi-band observations help to constrain the equivalent widths of emission lines. Thanks to cluster lensing, we are able to identify 52 candidates down to an intrinsic limiting magnitude of 28.5 and to a rest-frame [O III] λλ4959, 5007 equivalent width of 3737Å. Our samples include a number of EELGs at lower luminosities that are missed in other surveys, and the extremely high equivalent width can be only found in such faint galaxies. These EELGs can mimic the dropout feature similar to that of high redshift galaxies and contaminate the color-color selection of high redshift galaxies when the S/N ratio is limited or the band coverage is incomplete. We predict that the fraction of EELGs in the future high redshift galaxy selections cannot be neglected.

The Astrophysical Journal, 2009

We present a multiwavelength analysis of a sample of four hot (T X > 8 keV) X-ray galaxy clusters... more We present a multiwavelength analysis of a sample of four hot (T X > 8 keV) X-ray galaxy clusters (A1689, A2261, A2142, and A2390) using joint AMiBA Sunyaev-Zel'dovich effect (SZE) and Subaru weak lensing observations, combined with published X-ray temperatures, to examine the distribution of mass and the intracluster medium (ICM) in massive cluster environments. Our observations show that A2261 is very similar to A1689 in terms of lensing properties. Many tangential arcs are visible around A2261, with an effective Einstein radius ∼ 40 ′′ (at z ∼ 1.5), which when combined with our weak lensing measurements implies a mass profile well fitted by an NFW model with a high concentration c vir ∼ 10, similar to A1689 and to other massive clusters. The cluster A2142 shows complex mass substructure, and displays a shallower profile (c vir ∼ 5), consistent with detailed X-ray observations which imply recent interaction. The AMiBA map of A2142 exhibits an SZE feature associated with mass substructure lying ahead of the sharp north-west edge of the X-ray core suggesting a pressure increase in the ICM. For A2390 we obtain highly elliptical mass and ICM distributions at all radii, consistent with other X-ray and strong lensing work. Our cluster gas fraction measurements, free from the hydrostatic equilibrium assumption, are overall in good agreement with published X-ray and SZE observations, with the sample-averaged gas fraction of f gas (< r 200 ) = 0.133 ± 0.027, for our sample with M vir = (1.2 ± 0.1) × 10 15 M ⊙ h −1 . When compared to the cosmic baryon fraction f b = Ω b /Ω m constrained by the WMAP 5-year data, this indicates f gas,200 / f b = 0.78 ± 0.16, i.e., (22 ± 16)% of the baryons are missing from the hot phase of clusters.

We directly construct model-independent mass profiles of galaxy clusters from combined weak-lensi... more We directly construct model-independent mass profiles of galaxy clusters from combined weak-lensing distortion and magnification measurements within a Bayesian statistical framework,which allows for a full parameter-space extraction of the underlying signal. This method applies to the full range of radius outside the Einstein radius, and recovers the absolute mass normalization. We apply our method to deep Subaru imaging of five

Astronomy & Astrophysics, 2014

Context. The study of the galaxy stellar mass function (SMF) in relation to the galaxy environmen... more Context. The study of the galaxy stellar mass function (SMF) in relation to the galaxy environment and the stellar mass density profile, ρ ⋆ (r),is a powerful tool to constrain models of galaxy evolution. Aims. We determine the SMF of the z=0.44 cluster of galaxies MACS J1206.2-0847 separately for passive and star-forming (SF) galaxies, in different regions of the cluster, from the center out to approximately 2 virial radii. We also determine ρ ⋆ (r) to compare it to the number density and total mass density profiles. Methods. We use the dataset from the CLASH-VLT survey. Stellar masses are obtained by spectral energy distribution fitting with the MAGPHYS technique on 5-band photometric data obtained at the Subaru telescope. We identify 1363 cluster members down to a stellar mass of 10 9.5 M ⊙ , selected on the basis of their spectroscopic (∼ 1/3 of the total) and photometric redshifts. We correct our sample for incompleteness and contamination by non members. Cluster member environments are defined using either the clustercentric radius or the local galaxy number density. Results. The whole cluster SMF is well fitted by a double Schechter function, which is the sum of the two Schechter functions that provide good fits to the SMFs of, separately, the passive and SF cluster populations. The SMF of SF galaxies is significantly steeper than the SMF of passive galaxies at the faint end. The SMF of the SF cluster galaxies does not depend on the environment. The SMF of the passive cluster galaxies has a significantly smaller slope (in absolute value) in the innermost (≤ 0.50 Mpc, i.e., ∼ 0.25 virial radii), and in the highest density cluster region than in more external, lower density regions. The number ratio of giant/subgiant galaxies is maximum in this innermost region and minimum in the adjacent region, but then gently increases again toward the cluster outskirts. This is also reflected in a decreasing radial trend of the average stellar mass per cluster galaxy. On the other hand, the stellar mass fraction, i.e., the ratio of stellar to total cluster mass, does not show any significant radial trend. Conclusions. Our results appear consistent with a scenario in which SF galaxies evolve into passive galaxies due to density-dependent environmental processes, and eventually get destroyed very near the cluster center to become part of a diffuse intracluster medium. Dynamical friction, on the other hand, does not seem to play an important role. Future investigations of other clusters of the CLASH-VLT sample will allow us to confirm our interpretation.

The Cluster Lensing And Supernova survey with Hubble (CLASH) is a 524-orbit multi-cycle treasury ... more The Cluster Lensing And Supernova survey with Hubble (CLASH) is a 524-orbit multi-cycle treasury program to use the gravitational lensing properties of 25 galaxy clusters to accurately constrain their mass distributions. The survey, described in detail in this paper, will definitively establish the degree of concentration of dark matter in the cluster cores, a key prediction of CDM. The CLASH

The Astrophysical Journal, 2014

We present the supernova (SN) sample and Type-Ia SN (SN Ia) rates from the Cluster Lensing And Su... more We present the supernova (SN) sample and Type-Ia SN (SN Ia) rates from the Cluster Lensing And Supernova survey with Hubble (CLASH). Using the Advanced Camera for Surveys and the Wide Field Camera 3 on the Hubble Space Telescope (HST), we have imaged 25 galaxy-cluster fields and parallel fields of non-cluster galaxies. We report a sample of 27 SNe discovered in the parallel fields. Of these SNe, ∼ 13 are classified as SN Ia candidates, including four SN Ia candidates at redshifts z > 1.2. We measure volumetric SN Ia rates to redshift 1.8 and add the first upper limit on the SN Ia rate in the range 1.8 < z < 2.4. The results are consistent with the rates measured by the HST/GOODS and Subaru Deep Field SN surveys. We model these results together with previous measurements at z < 1 from the literature. The best-fitting SN Ia delay-time distribution (DTD; the distribution of times that elapse between a short burst of star formation and subsequent SN Ia explosions) is a power law with an index of −1.00 +0.06(0.09) −0.06(0.10) (statistical) +0.12 −0.08 (systematic), where the statistical uncertainty is a result of the 68% and 95% (in parentheses) statistical uncertainties reported for the various SN Ia rates (from this work and from the literature), and the systematic uncertainty reflects the range of possible cosmic star-formation histories. We also test DTD models produced by an assortment of published binary population synthesis (BPS) simulations. The shapes of all BPS double-degenerate DTDs are consistent with the volumetric SN Ia measurements, when the DTD models are scaled up by factors of 3-9. In contrast, all BPS single-degenerate DTDs are ruled out by the measurements at > 99% significance level.

The Astrophysical Journal, 2012

We present a strong-lensing analysis of the galaxy cluster MACS J1206.2-0847 (z=0.44) using UV, O... more We present a strong-lensing analysis of the galaxy cluster MACS J1206.2-0847 (z=0.44) using UV, Optical, and IR, HST/ACS/WFC3 data taken as part of the CLASH multi-cycle treasury program, with VLT/VIMOS spectroscopy for some of the multiply-lensed arcs. The CLASH observations, combined with our mass-model, allow us to identify 47 new multiply-lensed images of 12 distant sources. These images, along with the previously known arc, span the redshift range 1 z 5.5, and thus enable us to derive a detailed mass distribution and to accurately constrain, for the first time, the inner mass-profile of this cluster. We find an inner profile slope of d log Σ/d log θ −0.55 ± 0.1 (in the range [1 ,53 ], or 5 r 300 kpc), as commonly found for relaxed and well-concentrated clusters. Using the many systems uncovered here we derive credible critical curves and Einstein radii for different source redshifts. For a source at z s 2.5, the critical curve encloses a large area with an effective Einstein radius of θ E = 28 ± 3 , and a projected mass of 1.34 ± 0.15 × 10 14 M . From the current understanding of structure formation in concordance cosmology, these values are relatively high for clusters at z ∼ 0.5, so that detailed studies of the inner mass distribution of clusters such as MACS J1206.2-0847 can provide stringent tests of the ΛCDM paradigm.

Monthly Notices of the Royal Astronomical Society, 2009

We present an improved strong-lensing analysis of Cl0024+1654 (z=0.39) using deep HST/ACS/NIC3 im... more We present an improved strong-lensing analysis of Cl0024+1654 (z=0.39) using deep HST/ACS/NIC3 images, based on 33 multiply-lensed images of 11 background galaxies. These are found with a model that assumes mass approximately traces light, with a low order expansion to allow for flexibility on large scales. The model is constrained initially by the well known 5-image system (z=1.675) and refined as new multiply-lensed systems are identified using the model. Photometric redshifts of these new systems are then used to constrain better the mass profile by adopting the standard cosmological relation between redshift and lensing distance. Our model requires only 6 free parameters to describe well all positional and redshift data. The resulting inner mass profile has a slope of d log M/d log r −0.55, consistent with new weaklensing measurements where the data overlap, at r 200 kpc/h 70 . The combined profile is well fitted by a high concentration NFW mass profile, C vir ∼ 8.6 ± 1.6, similar to other well studied clusters, but larger than predicted with standard ΛCDM. A well defined radial critical curve is generated by the model and is clearly observed at r 12 , outlined by elongated images pointing towards the centre of mass. The relative fluxes of the multiply-lensed images are found to agree well with the modelled magnifications, providing an independent consistency check.

Monthly Notices of the Royal Astronomical Society, 2010

Weak lensing work can be badly compromised by unlensed foreground and cluster members which dilut... more Weak lensing work can be badly compromised by unlensed foreground and cluster members which dilute the true lensing signal. We show how the lensing amplitude in multi-colour space can be harnessed to securely separate cluster members from the foreground and background populations for three massive clusters, A1703 (z = 0.258), A370 (z = 0.375) and RXJ1347-11 (z = 0.451) imaged with Subaru. The luminosity functions of these clusters when corrected for dilution, show similar faint-end slopes, α ≃ −1.0, with no marked faint-end upturn to our limit of M R ≃ −15.0, and only a mild radial gradient. In each case, the radial profile of the M/L ratio peaks at intermediate radius, ≃ 0.2r vir , at a level of 300 − 500(M/L R ) ⊙ , and then falls steadily towards ∼ 100(M/L R ) ⊙ at the virial radius, similar to the mean field level. This behaviour is likely due to the relative paucity of central late-type galaxies, whereas for the E/S0-sequence only a mild radial decline in M/L is found for each cluster. We discuss this behaviour in the context of detailed simulations where predictions for tidal stripping may now be tested accurately with observations.

USING WEAK-LENSING DILUTION TO MEASURE LIGHT PROPERTIES OF A1689

Modern Physics Letters A, 2008

Weak-lensing induced by clusters of galaxies can probe the total mass distribution out to the vir... more Weak-lensing induced by clusters of galaxies can probe the total mass distribution out to the virial radius of the cluster, regardless of the nature of the mass or its dynamical state. To make a robust analysis, the cluster and background galaxy populations need to be separated. The E/S0 sequence of a cluster defines a boundary redward of which a reliable weak-lensing signal can be obtained from background galaxies, uncontaminated by the cluster. Below this limit, the signal is diluted by the proportion of unlensed cluster members. Employing deep Subaru and HST/ACS images of the massive cluster A1689, we use this dilution effect to carefully separate between the cluster members and the background, and thus derive the cluster light profile and luminosity functions to large radius. The light profile of A1689 is found to decline steadily to the limit of the data, r < 2 h-1Mpc, with a constant slope, d log(L)/d log(r) = -1.12 ± 0.06. We derive a cluster luminosity function with a flat faint-end slope of alpha = -1.05 ± 0.07, nearly independent of radius and with no faint upturn to Mi' < -12. The major advantage of this new approach is that no subtraction of far-field background counts is required.