Dissecting the RELICS cluster SPT-CLJ0615-5746 through the intracluster light: confirmation of the multiple merging state of the cluster formation

The intracluster light (ICL) fraction, measured at certain specific wavelengths, has been shown to provide a good marker for determining the dynamical stage of galaxy clusters, i.e., merging versus relaxed, for small to intermediate redshifts. Here, we apply it for the first time to a high-redshift system, SPT-CLJ0615-5746 at z=0.97, using its RELICS (Reionization Lensing Cluster Survey) observations in the optical and infrared. We find the ICL fraction signature of merging, with values ranging from 16 to 37%. A careful re-analysis of the X-ray data available for this cluster points to the presence of at least one current merger, and plausibly a second merger. These two results are in contradiction with previous works based on X-ray data, which claimed the relaxed state of SPT-CLJ0615-5746, and confirmed the evidences presented by kinematic analyses. We also found an abnormally high ICL fraction in the rest-frame near ultraviolet wavelengths, which may be attributed to the combination of several phenomena such as an ICL injection during recent mergers of stars with average early-type spectra, the reversed star formation-density relation found at this high redshift in comparison with lower-redshift clusters, and projection effects.Comment: 15 pages, 12 figures, submitted to A&

Two Lensed Star Candidates at z ≃ 4.8 behind the Galaxy Cluster MACS J0647.7+7015

Full list of authors: Meena, Ashish Kumar; Zitrin, Adi; Jimenez-Teja, Yolanda; Zackrisson, Erik; Chen Wenlei; Coe, Dan; Diego, Jose M.; Dimauro, Paola; Furtak, Lukas J.; Kelly, Patrick L.; Oguri, Masamune; Welch, Brian; Abdurro'uf, Abdurro'uf; Andrade-Santos, Felipe; Adamo, Angela; Bhatawdekar, Rachana; Bradac, Marusa; Bradley, Larry D.; Broadhurst, Tom; Conselice, Christopher J.; Dayal, Pratika; Donahue, Megan; Frye, Brenda L.; Fujimoto, Seiji; Hsiao, Tiger Yu-Yang; Kokorev, Vasily; Mahler, Guillaume; Vanzella, Eros; Windhorst, Rogier A.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.We report the discovery of two extremely magnified lensed star candidates behind the galaxy cluster MACS J0647.7+015 using recent multiband James Webb Space Telescope (JWST) NIRCam observations. The star candidates are seen in a previously known, zphot ≃ 4.8 dropout giant arc that straddles the critical curve. The candidates lie near the expected critical curve position, but lack clear counter-images on the other side of it, suggesting these are possibly stars undergoing caustic crossings. We present revised lensing models for the cluster, including multiply imaged galaxies newly identified in the JWST data, and use them to estimate background macro-magnifications of at least ≳90 and ≳50 at the positions of the two candidates, respectively. With these values, we expect effective, caustic-crossing magnifications of ∼[103–105] for the two star candidates. The spectral energy distributions of the two candidates match well the spectra of B-type stars with best-fit surface temperatures of ∼10,000 K, and ∼12,000 K, respectively, and we show that such stars with masses ≳20 M⊙ and ≳50 M⊙, respectively, can become sufficiently magnified to be observable. We briefly discuss other alternative explanations and conclude that these objects are likely lensed stars, but also acknowledge that the less-magnified candidate may alternatively reside in a star cluster. These star candidates constitute the second highest-redshift examples to date after Earendel at zphot ≃ 6.2, establishing further the potential of studying extremely magnified stars at high redshifts with JWST. Planned future observations, including with NIRSpec, will enable a more detailed view of these candidates in the near future. © 2023. The Author(s). Published by the American Astronomical Society.A.K.M., A.Z., and L.J.F. acknowledge support from grant 2020750 from the United States-Israel Binational Science Foundation (BSF) and grant 2109066 from the United States National Science Foundation (NSF), and by the Ministry of Science & Technology, Israel. Y.J.-T. acknowledges financial support from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 898633, the MSCA IF Extensions Program of the Spanish National Research Council (CSIC), and the State Agency for Research of the Spanish MCIU through the Center of Excellence Severo Ochoa award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). E.Z. acknowledges funding from the Swedish National Space Agency. J.M.D. acknowledges the support of projects PGC2018-101814-B-100 and MDM-2017-0765. B.W. acknowledges support from NASA under award No. 80GSFC21M0002. A.A. acknowledges support from the Swedish Research Council (Vetenskapsrådet project grants 2021–05559). R.A.B gratefully acknowledges support from the European Space Agency (ESA) Research Fellowship. M.B. acknowledges support from the Slovenian national research agency ARRS through grant N1-0238. P.D. acknowledges support from the NWO grant 016.VIDI.189.162 ("ODIN") and from the European Commission's and University of Groningen's CO-FUND Rosalind Franklin program. G.M. acknowledges funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. MARACHAS—DLV-896778. R.A.W. acknowledges support from NASA JWST Interdisciplinary Scientist grants NAG5-12460, NNX14AN10G and 80NSSC18K0200 from GSFC.With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).Peer reviewe

The ALHAMBRA survey: Bayesian photometric redshifts with 23 bands for 3 deg2

The Advance Large Homogeneous Area Medium-Band Redshift Astronomical (ALHAMBRA) survey has observed eight different regions of the sky, including sections of the Cosmic Evolution Survey (COSMOS), DEEP2, European Large-Area Infrared Space Observatory Survey (ELAIS), Great Observatories Origins Deep Survey North (GOODS-N), Sloan Digital Sky Survey (SDSS) and Groth fields using a new photometric system with 20 optical, contiguous ~300-Å filters plus the JHKs bands. The filter system is designed to optimize the effective photometric redshift depth of the survey, while having enough wavelength resolution for the identification of faint emission lines. The observations, carried out with the Calar Alto 3.5-m telescope using the wide-field optical camera Large Area Imager for Calar Alto (LAICA) and the near-infrared (NIR) instrument Omega-2000, represent a total of ~700 h of on-target science images. Here we present multicolour point-spread function (PSF) corrected photometry and photometric redshifts for ~438 000 galaxies, detected in synthetic F814W images. The catalogues are complete down to a magnitude I~24.5AB and cover an effective area of 2.79 deg2. Photometric zero-points were calibrated using stellar transformation equations and refined internally, using a new technique based on the highly robust photometric redshifts measured for emission-line galaxies. We calculate Bayesian photometric redshifts with the Bayesian Photometric Redshift (BPZ)2.0 code, obtaining a precision of δz/(1+zs)=1 per cent for I<22.5 and δz/(1+zs)=1.4 per cent for 22.5<I<24.5. The global n(z) distribution shows a mean redshift 〈z〉=0.56 for I<22.5 AB and 〈z〉=0.86 for I<24.5 AB. Given its depth and small cosmic variance, ALHAMBRA is a unique data set for galaxy evolution studies

J-PLUS: analysis of the intracluster light in the Coma cluster

The intracluster light (ICL) is a luminous component of galaxy clusters composed of stars that are gravitationally bound to the cluster potential but do not belong to the individual galaxies. Previous studies of the ICL have shown that its formation and evolution are intimately linked to the evolutionary stage of the cluster. Thus, the analysis of the ICL in the Coma cluster will give insights into the main processes driving the dynamics in this highly complex system. Using a recently developed technique, we measure the ICL fraction in Coma at several wavelengths, using the J-PLUS unique filter system. The combination of narrow- and broadband filters provides valuable information on the dynamical state of the cluster, the ICL stellar types, and the morphology of the diffuse light. We use the Chebyshev-Fourier Intracluster Light Estimator (CICLE) to disentangle the ICL from the light of the galaxies, and to robustly measure the ICL fraction in seven J-PLUS filters. We obtain the ICL fraction distribution of the Coma cluster at different optical wavelengths, which varies from $\sim 7\%-21\%$, showing the highest values in the narrowband filters J0395, J0410, and J0430. This ICL fraction excess is distinctive pattern recently observed in dynamically active clusters (mergers), indicating a higher amount of bluer stars in the ICL compared to the cluster galaxies. Both the high ICL fractions and the excess in the bluer filters are indicative of a merging state. The presence of younger/lower-metallicity stars the ICL suggests that the main mechanism of ICL formation for the Coma cluster is the stripping of the stars in the outskirts of infalling galaxies and, possibly, the disruption of dwarf galaxies during past/ongoing mergers.Comment: 10 pages, 3 figures, 1 table. Accepted for publication in A&

The ALHAMBRA survey: Accurate merger fractions by PDF analysis of photometric close pairs

Our goal is to develop and test a novel methodology to compute accurate close pair fractions with photometric redshifts. We improve the current methodologies to estimate the merger fraction f_m from photometric redshifts by (i) using the full probability distribution functions (PDFs) of the sources in redshift space, (ii) including the variation in the luminosity of the sources with z in both the selection of the samples and in the luminosity ratio constrain, and (iii) splitting individual PDFs into red and blue spectral templates to deal robustly with colour selections. We test the performance of our new methodology with the PDFs provided by the ALHAMBRA photometric survey. The merger fractions and rates from the ALHAMBRA survey are in excellent agreement with those from spectroscopic work, both for the general population and for red and blue galaxies. With the merger rate of bright (M_B <= -20 - 1.1z) galaxies evolving as (1+z)^n, the power-law index n is larger for blue galaxies (n = 2.7 +- 0.5) than for red galaxies (n = 1.3 +- 0.4), confirming previous results. Integrating the merger rate over cosmic time, we find that the average number of mergers per galaxy since z = 1 is N_m = 0.57 +- 0.05 for red galaxies and N_m = 0.26 +- 0.02 for blue galaxies. Our new methodology exploits statistically all the available information provided by photometric redshift codes and provides accurate measurements of the merger fraction by close pairs only using photometric redshifts. Current and future photometric surveys will benefit of this new methodology.Comment: Submitted to A&A, 15 pages, 15 figures, 6 tables. Comments are welcome. Close pair systems available at https://cloud.iaa.csic.es/alhambra/catalogues/ClosePairs

The ALHAMBRA Survey: Bayesian Photometric Redshifts with 23 bands for 3 squared degrees

The ALHAMBRA (Advance Large Homogeneous Area Medium Band Redshift Astronomical) survey has observed 8 different regions of the sky, including sections of the COSMOS, DEEP2, ELAIS, GOODS-N, SDSS and Groth fields using a new photometric system with 20 contiguous ~ $300\AA$ filters covering the optical range, combining them with deep $JHKs$ imaging. The observations, carried out with the Calar Alto 3.5m telescope using the wide field (0.25 sq. deg FOV) optical camera LAICA and the NIR instrument Omega-2000, correspond to ~700hrs on-target science images. The photometric system was designed to maximize the effective depth of the survey in terms of accurate spectral-type and photo-zs estimation along with the capability of identification of relatively faint emission lines. Here we present multicolor photometry and photo-zs for ~438k galaxies, detected in synthetic F814W images, complete down to I~24.5 AB, taking into account realistic noise estimates, and correcting by PSF and aperture effects with the ColorPro software. The photometric ZP have been calibrated using stellar transformation equations and refined internally, using a new technique based on the highly robust photometric redshifts measured for emission line galaxies. We calculate photometric redshifts with the BPZ2 code, which includes new empirically calibrated templates and priors. Our photo-zs have a precision of $dz/(1+z_s)=1$ for I<22.5 and 1.4% for 22.5<I<24.5. Precisions of less than 0.5% are reached for the brighter spectroscopic sample, showing the potential of medium-band photometric surveys. The global $P(z)$ shows a mean redshift =0.56 for I=0.86 for I<24.5 AB. The data presented here covers an effective area of 2.79 sq. deg, split into 14 strips of 58.5'x15.5' and represents ~32 hrs of on-target.Comment: The catalog data and a full resolution version of this paper is available at https://cloud.iaa.csic.es/alhambra

The Cluster Lensing and Supernova Survey with Hubble (CLASH): Strong Lensing Analysis of Abell 383 from 16-Band HST WFC3/ACS Imaging

We examine the inner mass distribution of the relaxed galaxy cluster Abell 383 in deep 16-band HST/ACS+WFC3 imaging taken as part of the CLASH multi-cycle treasury program. Our program is designed to study the dark matter distribution in 25 massive clusters, and balances depth with a wide wavelength coverage to better identify lensed systems and generate precise photometric redshifts. This information together with the predictive strength of our strong-lensing analysis method identifies 13 new multiply-lensed images and candidates, so that a total of 27 multiple-images of 9 systems are used to tightly constrain the inner mass profile, $d\log \Sigma/d\log r\simeq -0.6\pm 0.1$ (r<160 kpc). We find consistency with the standard distance-redshift relation for the full range spanned by the lensed images, 1.01<z<6.03, with the higher redshift sources deflected through larger angles as expected. The inner mass profile derived here is consistent with the results of our independent weak-lensing analysis of wide-field Subaru images, with good agreement in the region of overlap. The overall mass profile is well fitted by an NFW profile with M_{vir}=(5.37^{+0.70}_{-0.63}\pm 0.26) x 10^{14}M_{\odot}/h and a relatively high concentration, c_{vir}=8.77^{+0.44}_{-0.42}\pm 0.23, which lies above the standard c-M relation similar to other well-studied clusters. The critical radius of Abell 383 is modest by the standards of other lensing clusters, r_{E}\simeq16\pm2\arcsec (for z_s=2.55), so the relatively large number of lensed images uncovered here with precise photometric redshifts validates our imaging strategy for the CLASH survey. In total we aim to provide similarly high-quality lensing data for 25 clusters, 20 of which are X-ray selected relaxed clusters, enabling a precise determination of the representative mass profile free from lensing bias. (ABRIDGED)Comment: 15 pages, 14 figures, 2 tabels; V3 matches the submitted version later published in Ap

Geodetic Research on Deception Island and its Environment (South Shetland Islands, Bransfield Sea and Antarctic Peninsula) During Spanish Antarctic Campaigns (1987-2007)

Since 1987, Spain has been continuously developing several scientific projects, mainly based on Earth Sciences, in Geodesy, Geochemistry, Geology or Volcanology. The need of a geodetic reference frame when doing hydrographic and topographic mapping meant the organization of the earlier campaigns with the main goals of updating the existing cartography and of making new maps of the area. During this period of time, new techniques arose in Space Geodesy improving the classical methodology and making possible its applications to other different fields such as tectonic or volcanism. Spanish Antarctic Geodetic activities from the 1987/1988 to 2006/2007 campaigns are described as well as a geodetic and a levelling network are presented. The first network, RGAE, was designed and established to define a reference frame in the region formed by the South Shetlands Islands, the Bransfield Sea and the Antarctic Peninsula whereas the second one, REGID, was planned to control the volcanic activity in Deception Island. Finally, the horizontal and vertical deformation models are described too, as well as the strategy which has been followed when computing an experimental geoid