- ID:
- ivo://CDS.VizieR/J/ApJ/839/L11
- Title:
- HST strong lensing analysis of PLCKG287.0+32.9
- Short Name:
- J/ApJ/839/L11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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 ~40" (for a source at z_s_~2, nominally). Here, we report an addition to that list of the Sunyaev-Zel'dovich (SZ) selected cluster, PLCKG287.0+32.9 (z=0.38), the second-highest SZ-mass (M500) 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 Hubble Space Telescope (HST) data, including a long, l~22" 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 (1.55arcmin^2^, z_s_~2), corresponding to an effective Einstein radius of {theta}_E_~42". The model suggests the critical area will expand to 2.58arcmin^2^ ({theta}_E_~54") for sources at z_s_~10. Our work adds to recent efforts to model very massive clusters toward 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~7 dropout.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/800/18
- Title:
- HST/WFC3 observations of z~7-8 galaxies in A2744
- Short Name:
- J/ApJ/800/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Exploiting the power of gravitational lensing, the Hubble Frontier Fields (HFF) program aims at observing six massive galaxy clusters to explore the distant universe far beyond the limits of blank field surveys. Using the complete Hubble Space Telescope observations of the first HFF cluster A2744, we report the detection of 50 galaxy candidates at z~7 and eight candidates at z~8 in a total survey area of 0.96arcmin^2^ in the source plane. Three of these galaxies are multiply imaged by the lensing cluster. Using an updated model of the mass distribution in the cluster we were able to calculate the magnification factor and the effective survey volume for each galaxy in order to compute the ultraviolet galaxy luminosity function (LF) at both redshifts 7 and 8. Our new measurements reliably extend the z~7 UV LF down to an absolute magnitude of M_UV_~-15.5. We find a characteristic magnitude of M_UV_^*^=-20.90_-0.73_^+0.90^mag and a faint-end slope {alpha}=-2.01_-0.28_^+0.20^, close to previous determinations in blank fields. We show here for the first time that this slope remains steep down to very faint luminosities of 0.01L^*^. Although prone to large uncertainties, our results at z~8 also seem to confirm a steep faint-end slope below 0.1L^*^. The HFF program is therefore providing an extremely efficient way to study the faintest galaxy populations at z>7 that would otherwise be inaccessible with current instrumentation. The full sample of six galaxy clusters will provide even better constraints on the buildup of galaxies at early epochs and their contribution to cosmic reionization.
- ID:
- ivo://CDS.VizieR/J/AJ/161/126
- Title:
- I-band LC of the microlensing event KMT-2017-BLG-2820
- Short Name:
- J/AJ/161/126
- Date:
- 10 Dec 2021
- Publisher:
- CDS
- Description:
- We report a new free-floating planet (FFP) candidate, KMT-2017-BLG-2820, with Einstein radius {theta}E~6{mu}as, lens-source relative proper motion {mu}rel~8mas/yr, and Einstein timescale t_E_=6.5hr. It is the third FFP candidate found in an ongoing study of giant-source finite-source point-lens (FSPL) events in the KMTNet database and the sixth FSPL FFP candidate overall. We find no significant evidence for a host. Based on their timescale distributions and detection rates, we argue that five of these six FSPL FFP candidates are drawn from the same population as the six point-source point-lens (PSPL) FFP candidates found by Mroz et al. in the OGLE-IV database. The {theta}E distribution of the FSPL FFPs implies that they are either sub- Jovian planets in the bulge or super-Earths in the disk. However, the apparent "Einstein desert" (10<~{theta}E/{mu}as<~30) would argue for the latter. Whether each of the 12 (six FSPL and six PSPL) FFP candidates is truly an FFP or simply a very wide-separation planet can be determined at first adaptive optics (AO) light on 30m telescopes, and earlier for some. If the latter, a second epoch of AO observations could measure the projected planet- host separation with a precision of O(10au). At the present time, the balance of evidence favors the unbound-planet hypothesis.
- ID:
- ivo://CDS.VizieR/J/AJ/159/98
- Title:
- I-band LC of the microlensing event KMT-2016-BLG-1836
- Short Name:
- J/AJ/159/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a super-Jovian planet in the microlensing event KMT-2016-BLG-1836, which was found by the Korea Microlensing Telescope Network (KMTNet) high-cadence observations ({Gamma}~4/hr). The planet-host mass ratio q~0.004. A Bayesian analysis indicates that the planetary system is composed of a super-Jovian M_planet_=2.2_-1.1_^+1.9^M_J_ planet orbiting an M or K dwarf, M_host_=0.49_-0.25_^+0.38^M_{sun}_, at a distance of D_L_=7.1_-2.4_^+0.8^kpc. The projected planet-host separation is 3.5_-0.9_^+1.1^au, implying that the planet is located beyond the snow line of the host star. Future high-resolution images can potentially strongly constrain the lens brightness and thus the mass and distance of the planetary system. Without considering detailed detection efficiency, selection, or publication biases, we find a potential mass-ratio desert at -3.7<~logq<~-3.0 for the 31 published KMTNet planets.
- ID:
- ivo://CDS.VizieR/J/AJ/162/96
- Title:
- I-band light curve of KMT-2016-BLG-2605 with KMTNet
- Short Name:
- J/AJ/162/96
- Date:
- 11 Mar 2022 14:37:06
- Publisher:
- CDS
- Description:
- With a planet-host mass ratio q=0.012{+/-}0.001, KMT-2016-BLG-2605 has the shortest Einstein timescale, tE=3.41{+/-}0.13days, of any planetary microlensing event to date. This prompts us to examine the full sample of seven short (tE<7days) planetary events with good q measurements. We find that six have clustered Einstein radii {theta}E=115{+/-}20{mu}as and lens-source relative proper motions {mu}rel~9.5{+/-}2.5mas/yr. For the seventh, these two quantities could not be measured. These distributions are consistent with a Galactic bulge population of very low mass (VLM) hosts near the hydrogen-burning limit. This conjecture could be verified by imaging at first adaptive optics light on next-generation (30m) telescopes. Based on a preliminary assessment of the sample, "planetary" companions (i.e., below the deuterium-burning limit) are divided into "genuine planets," formed in their disks by core accretion, and VLM brown dwarfs, which form like stars. We discuss techniques for expanding the sample, which include taking account of the peculiar "anomaly-dominated" morphology of the KMT-2016-BLG-2605 light curve.
- ID:
- ivo://CDS.VizieR/J/AJ/162/267
- Title:
- I-band light curve of OGLE-2019-BLG-1058 with KMTNet
- Short Name:
- J/AJ/162/267
- Date:
- 25 Mar 2022 06:06:33
- Publisher:
- CDS
- Description:
- We show that because the conditions for producing terrestrial microlens parallax (TPRX; i.e., a nearby disk lens) will also tend to produce a large lens-source relative proper motion ({mu}rel), source proper motion ({mu}S) measurements in general provide a strong test of TPRX signals, which Gould & Yee (2013) showed were an important probe of free-floating planet (FFP) candidates. As a case study, we report a single-lens/single-source microlensing event designated as OGLE-2019-BLG-1058. For this event, the short timescale (~2.5days) and very fast {mu}rel (~17.6mas/yr) suggest that this isolated lens is an FFP candidate located in the disk of our Galaxy. For this event, we find a TPRX signal consistent with a disk FFP, but at low significance. A direct measurement of the {mu}S shows that the large {mu}rel is due to an extreme {mu}S, and thus, the lens is consistent with being a very-low-mass star in the bulge and the TPRX measurement is likely spurious. By contrast, we show how a precise measurement of {mu}S with the mean properties of the bulge proper motion distribution would have given the opposite result; i.e., provided supporting evidence for an FFP in the disk and the TPRX measurement.
- ID:
- ivo://CDS.VizieR/J/AJ/159/116
- Title:
- I-band light curves of OGLE-2015-BLG-1771Lb
- Short Name:
- J/AJ/159/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery and the analysis of the short (t_E_<5days) planetary microlensing event, OGLE-2015-BLG-1771. The event was discovered by the Optical Gravitational Lensing Experiment, and the planetary anomaly (at I~19) was captured by The Korea Microlensing Telescope Network. The event has three surviving planetary models that explain the observed light curves, with planet-host mass ratio q~5.4x10^-3^, 4.5x10^-3^ and 4.5x10^-2^, respectively. The first model is the best-fit model, while the second model is disfavored by {Delta}_{chi}^2^_~3. The last model is strongly disfavored by {Delta}_{chi}^2^_~15 but not ruled out. A Bayesian analysis using a Galactic model indicates that the first two models are probably composed of a Saturn-mass planet orbiting a late M dwarf, while the third one could consist of a super-Jovian planet and a mid-mass brown dwarf. The source-lens relative proper motion is {mu}_rel_~9mas/yr, so the source and lens could be resolved by current adaptive-optics instruments in 2020 if the lens is luminous.
- ID:
- ivo://CDS.VizieR/J/ApJ/845/157
- Title:
- IMF in 3 low-redshift strong lenses from SNELLS
- Short Name:
- J/ApJ/845/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new observations of the three nearest early-type galaxy (ETG) strong lenses discovered in the SINFONI Nearby Elliptical Lens Locator Survey (SNELLS). Based on their lensing masses, these ETGs were inferred to have a stellar initial mass function (IMF) consistent with that of the Milky Way, not the bottom-heavy IMF that has been reported as typical for high-{sigma} ETGs based on lensing, dynamical, and stellar population synthesis techniques. We use these unique systems to test the consistency of IMF estimates derived from different methods. We first estimate the stellar M*/L using lensing and stellar dynamics. We then fit high-quality optical spectra of the lenses using an updated version of the stellar population synthesis models developed by Conroy & van Dokkum. When examined individually, we find good agreement among these methods for one galaxy. The other two galaxies show 2-3{sigma} tension with lensing estimates, depending on the dark matter contribution, when considering IMFs that extend to 0.08M_{sun}_. Allowing a variable low-mass cutoff or a nonparametric form of the IMF reduces the tension among the IMF estimates to <2{sigma}. There is moderate evidence for a reduced number of low-mass stars in the SNELLS spectra, but no such evidence in a composite spectrum of matched-{sigma} ETGs drawn from the SDSS. Such variation in the form of the IMF at low stellar masses (m<~0.3M_{sun}_), if present, could reconcile lensing/dynamical and spectroscopic IMF estimates for the SNELLS lenses and account for their lighter M*/L relative to the mean matched-{sigma} ETG. We provide the spectra used in this study to facilitate future comparisons.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A56
- Title:
- KiDS-BEXGO catalog
- Short Name:
- J/A+A/632/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Within a Kilo-Degree Survey (KiDS) Strongly lensed QUAsar Detection project (KiDS-SQuaD), we built a catalogue of bright extragalactic objects from the KiDS DR4, with the main objective to select the reliable gravitationally lensed quasar candidates. We used machine learning algorithm, trained on Sloan Digital Sky Survey DR14 data, to classify sources from subsample (r<22mag) of KiDS DR4 on three classes: stars, quasars and galaxies. Resulting KiDS Bright EXtraGalactic Objects catalogue (KiDS-BEXGO) contains ~6M galaxies and ~0.2M quasars. KiDS-BEXGO represents the first comprehensive identification of bright extragalactic objects in the KiDS DR4 data.
- ID:
- ivo://CDS.VizieR/J/A+A/649/A90
- Title:
- KMT-2018-BLG-1025Lb I light curve
- Short Name:
- J/A+A/649/A90
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We aim to find missing microlensing planets hidden in the unanalyzed lensing events of previous survey data. For this purpose, we conduct a systematic inspection of high-magnification microlensing events, with peak magnifications Apeak>~30, in the data collected from high-cadence surveys in and before the 2018 season. From this investigation, we identify an anomaly in the lensing light curve of the event KMT-2018-BLG-1025. The analysis of the light curve indicates that the anomaly is caused by a very low mass-ratio companion to the lens. We identify three degenerate solutions, in which the ambiguity between a pair of solutions (solutions B) is caused by the previously known close-wide degeneracy, and the degeneracy between these and the other solution (solution A) is a new type that has not been reported before. The estimated mass ratio between the planet and host is q~0.8x10^-4^ for the solution A and q~1.6x10^-4^ for the solutions B. From the Bayesian analysis conducted with measured observables, we estimate that the masses of the planet and host and the distance to the lens are (Mp, Mh, DL)~(6.1M_{sun}_, 0.22M_Earth_, 6.7kpc) for the solution A and ~(4.4M_{sun}_, 0.08M_Earth_, 7.5kpc) for the solutions B. The planet mass is in the category of a super-Earth regardless of the solutions, making the planet the eleventh super-Earth planet, with masses lying between those of Earth and the Solar system's ice giants, discovered by microlensing.
