- ID:
- ivo://CDS.VizieR/J/A+A/567/A111
- Title:
- Multi-color detection of gravitational arcs
- Short Name:
- J/A+A/567/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Strong gravitational lensing provides fundamental insights into the understanding of the dark matter distribution in massive galaxies, galaxy clusters and the background cosmology. Despite their importance, the number of gravitational arcs discovered so far is small. The urge for more complete, large samples and unbiased methods of selecting candidates is rising. A number of methods for the automatic detection of arcs have been proposed in the literature, but large amounts of spurious detections retrieved by these methods forces observers to visually inspect thousands of candidates per square degree in order to clean the samples. This approach is largely subjective and requires a huge amount of eye-ball checking, especially considering the actual and upcoming wide field surveys, which will cover thousands of square degrees. In this paper we study the statistical properties of colours of gravitational arcs detected in the 37deg^2^ of the CARS survey.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/621/53
- Title:
- Multiple arc systems in A1689
- Short Name:
- J/ApJ/621/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze deep multicolor Advanced Camera images of the largest known gravitational lens, A1689. Radial and tangential arcs delineate the critical curves in unprecedented detail, and many small counterimages are found near the center of mass.
- ID:
- ivo://CDS.VizieR/J/ApJ/749/97
- Title:
- Multiple lensed images in MCS J1206.2-0847
- Short Name:
- J/ApJ/749/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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 dlog{Sigma}/dlog{theta}=~-0.55+/-0.1 (in the range [1",53"], or 5kpc<~r<~300kpc), 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 {theta}_E_=28"+/-3", and a projected mass of (1.34+/-0.15)x10^14^M_{sun}_. 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 {Lambda}CDM paradigm.
- ID:
- ivo://CDS.VizieR/J/ApJ/817/60
- Title:
- Multiply imaged supernova Refsdal
- Short Name:
- J/ApJ/817/60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Supernova "Refsdal", multiply imaged by cluster MACS1149.5+2223, represents a rare opportunity to make a true blind test of model predictions in extragalactic astronomy, on a timescale that is short compared to a human lifetime. In order to take advantage of this event, we produced seven gravitational lens models with five independent methods, based on Hubble Space Telescope (HST) Hubble Frontier Field images, along with extensive spectroscopic follow-up observations by HST, the Very Large and the Keck Telescopes. We compare the model predictions and show that they agree reasonably well with the measured time delays and magnification ratios between the known images, even though these quantities were not used as input. This agreement is encouraging, considering that the models only provide statistical uncertainties, and do not include additional sources of uncertainties such as structure along the line of sight, cosmology, and the mass sheet degeneracy. We then present the model predictions for the other appearances of supernova "Refsdal". A future image will reach its peak in the first half of 2016, while another image appeared between 1994 and 2004. The past image would have been too faint to be detected in existing archival images. The future image should be approximately one-third as bright as the brightest known image (i.e., H_AB_~25.7mag at peak and H_AB_~26.7mag six months before peak), and thus detectable in single-orbit HST images. We will find out soon whether our predictions are correct.
- ID:
- ivo://CDS.VizieR/J/ApJ/825/25
- Title:
- Narrow absorption lines of lensed QSO J1029+2623
- Short Name:
- J/ApJ/825/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We exploit the widely separated images of the lensed quasar SDSSJ1029+2623 (z_em_=2.197, {theta}=22.5") to observe its outflowing wind through two different sightlines. We present an analysis of three observations, including two with the Subaru telescope in 2010 February and 2014 April, separated by four years, and one with the Very Large Telescope, separated from the second Subaru observation by ~2 months. We detect 66 narrow absorption lines (NALs), of which 24 are classified as intrinsic NALs that are physically associated with the quasar based on partial coverage analysis. The velocities of intrinsic NALs appear to cluster around values of {nu}_ej_~59000, 43000, and 29000km/s, which is reminiscent of filamentary structures obtained by numerical simulations. There are no common intrinsic NALs at the same redshift along the two sightlines, implying that the transverse size of the NAL absorbers should be smaller than the sightline distance between two lensed images. In addition to the NALs with large ejection velocities of {nu}_ej_>1000km/s, we also detect broader proximity absorption lines (PALs) at z_abs_~z_em_. The PALs are likely to arise in outflowing gas at a distance of r<=620pc from the central black hole with an electron density of n_e_>=8.7x10^3^/cm^3^. These limits are based on the assumption that the variability of the lines is due to recombination. We discuss the implications of these results on the three-dimensional structure of the outflow.
- ID:
- ivo://CDS.VizieR/J/A+A/592/A75
- Title:
- New lens candidates in CFHTLS
- Short Name:
- J/A+A/592/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a new search for galaxy-scale strong lensing systems in CFHTLS Wide. Our lens-finding technique involves a preselection of potential lens galaxies, applying simple cuts in size and magnitude. We then perform a Principal Component Analysis of the galaxy images, ensuring a clean removal of the light profile. Lensed features are searched for in the residual images using the clustering topometric algorithm DBSCAN. We find 1098 lens candidates that we inspect visually, leading to a cleaned sample of 109 new lens candidates. Using realistic image simulations we estimate the completeness of our sample and show that it is independent of source surface brightness, Einstein ring size (image separation) or lens redshift. We compare the properties of our sample to previous lens searches in CFHTLS. Including the present search, the total number of lenses found in CFHTLS amounts to 678, which corresponds to ~4 lenses per square degree down to i(AB)=24.8. This is equivalent to ~60.000 lenses in total in a survey as wide as Euclid, but at the CFHTLS resolution and depth.
- ID:
- ivo://CDS.VizieR/J/A+A/300/323
- Title:
- NOT GL survey of multiply imaged quasars
- Short Name:
- J/A+A/300/323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A gravitational lens (GL)-search program, initiated in 1990 at the Nordic Optcal Telescope (NOT), has revealed several possible GL-candidates among a sample of 168 quasars (QSOs), chosen from three lists compiled by C. Hazard, D. Reimers and J. Surdej, respectively. Some of these candidates, selected for having close companions (within 5 arcseconds), were imaged in several filters and their colours compared. Low dispersion spectra of the most promising candidates were also obtained at the NOT and ESO New Technology Telescope (NTT). None of these has proved to be strong candidates of gravitational lensing effects. We present this new sample of QSOs and combine it with previously published optical QSO samples in a statistical analysis to yield constraints on flat cosmologies and galaxy velocity dispersions.
- ID:
- ivo://CDS.VizieR/J/ApJ/903/L11
- Title:
- OGLE and KMTNet light curve of OGLE-2016-BLG-1928
- Short Name:
- J/ApJ/903/L11
- Date:
- 21 Mar 2022 06:18:03
- Publisher:
- CDS
- Description:
- Some low-mass planets are expected to be ejected from their parent planetary systems during early stages of planetary system formation. According to planet formation theories, such as the core accretion theory, typical masses of ejected planets should be between 0.3 and 1.0M{Earth}. Although in practice such objects do not emit any light, they may be detected using gravitational microlensing via their light-bending gravity. Microlensing events due to terrestrial-mass rogue planets are expected to have extremely small angular Einstein radii (<~1{mu}as) and extremely short timescales (<~0.1day). Here, we present the discovery of the shortest-timescale microlensing event, OGLE-2016-BLG-1928, identified to date (t_E_~0.0288day=41.5min. Thanks to the detection of finite-source effects in the light curve of the event, we were able to measure the angular Einstein radius of the lens {theta}_E_=0.842{+/-}0.064{mu}as, making the event the most extreme short-timescale microlens discovered to date. Depending on its unknown distance, the lens may be a Mars- to Earth-mass object, with the former possibility favored by the Gaia proper motion measurement of the source. The planet may be orbiting a star but we rule out the presence of stellar companions up to the projected distance of ~8.0au from the planet. Our discovery demonstrates that terrestrial-mass free-floating planets can be detected and characterized using microlensing.
- ID:
- ivo://CDS.VizieR/J/ApJ/711/L48
- Title:
- 2008 OGLE Bulge microlensing alerts
- Short Name:
- J/ApJ/711/L48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study a sample of 16 microlensed Galactic bulge main-sequence turnoff region stars for which high-dispersion spectra have been obtained with detailed abundance analyses. We demonstrate that there is a very strong and highly statistically significant correlation between the maximum magnification of the microlensed bulge star and the value of the [Fe/H] deduced from the high resolution spectrum of each object.
- ID:
- ivo://CDS.VizieR/J/AcA/50/421
- Title:
- OGLE-II DIA BUL_SC1 field
- Short Name:
- J/AcA/50/421
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an implementation of the difference image photometry based on the Alard and Lupton optimal PSF matching algorithm. The most important feature distinguishing this method from the ones using Fourier divisions is that equations are solved in real space and the knowledge of each PSF is not required for determination of the convolution kernel. We evaluate the method and software on 380G B of OGLE-II bulge microlensing data obtained in 1997-1999 observing seasons. The error distribution is Gaussian to better than 99% with the amplitude only 17% above the photon noise limit for faint stars. Over the entire range of the observed magnitudes the resulting scatter is improved by a factor of 2-3 compared to DoPhot photometry, currently a standard tool for massive stellar photometry in microlensing searches. For testing purposes the photometry of approx 4600 candidate variable stars and sample difference image data are provided for BUL_SC1 field. In the candidate selection process, very few assumptions have been made about the specific types of flux variations, which makes this data set well suited for general variability studies, including the development of the classification schemes.
