- ID:
- ivo://CDS.VizieR/J/ApJ/740/L34
- Title:
- Chandra monitoring of QSO J2240+0321
- Short Name:
- J/ApJ/740/L34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our long-term Chandra X-ray monitoring data for the gravitationally lensed quasar Q2237+0305 with 20 epochs spanning 10 years. We easily detect microlensing variability between the images in the full (0.2-8keV), soft (0.2-2keV), and hard (2-8keV) bands at very high confidence. We also detect, for the first time, chromatic microlensing differences between the soft and hard X-ray bands. The hard X-ray band is more strongly microlensed than the soft band, suggesting that the corona above the accretion disk thought to generate the X-rays has a non-uniform electron distribution, in which the hotter and more energetic electrons occupy more compact regions surrounding the black holes. Both the hard and soft X-ray bands are more strongly microlensed than the optical (rest-frame UV) emission, indicating that the X-ray emission is more compact than the optical, confirming the microlensing results from other lenses.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/625/633
- Title:
- Chandra sources in B1600+434 and B1608+656 fields
- Short Name:
- J/ApJ/625/633
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed B1600+434 and B1608+656 with Chandra ACIS, detecting both quasar images in B1600+434 and three of four images in B1608+656. We also detected 157 serendipitous X-ray sources in the two Chandra fields and identified the brighter optical counterparts using the Sloan Digital Sky Survey and Palomar Digital Sky Survey.
- ID:
- ivo://CDS.VizieR/J/ApJ/709/447
- Title:
- Chemical composition of OGLE-2007-BLG-514S
- Short Name:
- J/ApJ/709/447
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high-resolution spectrum of a microlensed G dwarf in the Galactic bulge with spectroscopic temperature T_eff_=5600+/-180K. This I~21mag star was magnified by a factor ranging from 1160 to 1300 at the time of observation. Its high metallicity ([Fe/H]=0.33+/-0.15dex) places this star at the upper end of the bulge giant metallicity distribution. Using a Kolmogorov-Smirnov test, we find a 1.6% probability that the published microlensed bulge dwarfs share an underlying distribution with bulge giants, properly accounting for a radial bulge metallicity gradient. We obtain abundance measurements for 15 elements and perform a rigorous error analysis that includes covariances between parameters. This star, like bulge giants with the same metallicity, shows no alpha enhancement. It confirms the chemical abundance trends observed in previously analyzed bulge dwarfs. At supersolar metallicities, we observe a discrepancy between bulge giant and bulge dwarf Na abundances.
- ID:
- ivo://CDS.VizieR/J/ApJ/806/268
- Title:
- Cheshire Cat galaxies: redshifts and magnitudes
- Short Name:
- J/ApJ/806/268
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Cheshire Cat is a relatively poor group of galaxies dominated by two luminous elliptical galaxies surrounded by at least four arcs from gravitationally lensed background galaxies that give the system a humorous appearance. Our combined optical/X-ray study of this system reveals that it is experiencing a line of sight merger between two groups with a roughly equal mass ratio with a relative velocity of ~1350 km/s. One group was most likely a low-mass fossil group, while the other group would have almost fit the classical definition of a fossil group. The collision manifests itself in a bimodal galaxy velocity distribution, an elevated central X-ray temperature and luminosity indicative of a shock, and gravitational arc centers that do not coincide with either large elliptical galaxy. One of the luminous elliptical galaxies has a double nucleus embedded off-center in the stellar halo. The luminous ellipticals should merge in less than a Gyr, after which observers will see a massive 1.2-1.5x10^14^ M_{sun}_ fossil group with an M_r_=-24.0 brightest group galaxy at its center. Thus, the Cheshire Cat offers us the first opportunity to study a fossil group progenitor. We discuss the limitations of the classical definition of a fossil group in terms of magnitude gaps between the member galaxies. We also suggest that if the merging of fossil (or near-fossil) groups is a common avenue for creating present-day fossil groups, the time lag between the final galactic merging of the system and the onset of cooling in the shock-heated core could account for the observed lack of well-developed cool cores in some fossil groups.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A16
- Title:
- Chromatic variations in microlensing events
- Short Name:
- J/A+A/657/A16
- Date:
- 16 Mar 2022 00:52:23
- Publisher:
- CDS
- Description:
- To a first approximation, the microlensing phenomenon is achromatic and great advancements have been achieved with regard to the interpretation of the achromatic signals, leading to the discovery and characterization of well above 100 new exoplanets. At a higher order accuracy in the observations, microlensing has a chromatic component (a color term) that has thus far been explored to a much lesser extent. Here, we analyze the chromatic microlensing effect of four different physical phenomena, which have the potential to contribute key knowledge of the stellar properties that is not easily achievable with other methods of observation. Our simulation is limited to the case of main-sequence source stars. Microlensing is particularly sensitive to giant and sub-giant stars near the Galactic center. While this population can be studied in short snapshots by the largest telescopes in the world, a general monitoring and characterization of the population can be achieved by use of more accessible medium-sized telescopes with specialized equipment via dual-color monitoring from observatories at sites with excellent seeing. We limit the results of this study to what will be achievable from the Danish 1.54m telescope at La Silla observatory based on the use of the existing dual-color lucky imaging camera. Such potential monitoring programs of the bulge population from medium-sized telescopes include the characterization of starspots, limb-darkening, the frequency of close-in giant planet companions, and gravity darkening for blended source stars. We conclude our simulations with quantifying the likelihood of detecting these different phenomena per object where they are present to be ~60 and ~30% for the above-mentioned phenomena when monitored during both high-magnification and caustic crossings, respectively.
- ID:
- ivo://CDS.VizieR/J/ApJ/814/L6
- Title:
- CIII] emission in near & far star-forming galaxies
- Short Name:
- J/ApJ/814/L6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure [C III] 1907, C III] 1909{AA} emission lines in 11 gravitationally lensed star-forming galaxies at z~1.6-3, finding much lower equivalent widths than previously reported for fainter lensed galaxies. While it is not yet clear what causes some galaxies to be strong C III] emitters, C III] emission is not a universal property of distant star-forming galaxies. We also examine C III] emission in 46 star-forming galaxies in the local universe, using archival spectra from GHRS, FOS, and STIS on HST and IUE. Twenty percent of these local galaxies show strong C III] emission, with equivalent widths <-5{AA}. Three nearby galaxies show C III] emission equivalent widths as large as the most extreme emitters yet observed in the distant universe; all three are Wolf-Rayet galaxies. At all redshifts, strong C III] emission may pick out low-metallicity galaxies experiencing intense bursts of star formation. Such local C iii] emitters may shed light on the conditions of star formation in certain extreme high-redshift galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/762/L30
- Title:
- CLASH: MCS J0416.1-2403 strong lensing analysis
- Short Name:
- J/ApJ/762/L30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform a strong lensing analysis of the merging galaxy cluster MACS J0416.1-2403 (M0416; z=0.42) in recent CLASH/HST observations. We identify 70 new multiple images and candidates of 23 background sources in the range 0.7<~z_phot_<~6.14 including two probable high-redshift dropouts, revealing a highly elongated lens with axis ratio =~5:1, and a major axis of ~100" (z_s_~2). Compared to other well-studied clusters, M0416 shows an enhanced lensing efficiency. Although the critical area is not particularly large (=~0.6{squ}'; z_s_~2), the number of multiple images, per critical area, is anomalously high. We calculate that the observed elongation boosts the number of multiple images, per critical area, by a factor of ~2.5x, due to the increased ratio of the caustic area relative to the critical area. Additionally, we find that the observed separation between the two main mass components enlarges the critical area by a factor of ~2. These geometrical effects can account for the high number (density) of multiple images observed. We find in numerical simulations that only ~4% of the clusters (with M_vir_>=6x10^14^h^-1^M_{sun}_) exhibit critical curves as elongated as in M0416.
- ID:
- ivo://CDS.VizieR/J/ApJ/755/31
- Title:
- Compilation of 122 strong gravitational lenses
- Short Name:
- J/ApJ/755/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the redshift distribution of two samples of early-type gravitational lenses, extracted from a larger collection of 122 systems, to constrain the cosmological constant in the {Lambda}CDM model and the parameters of a set of alternative dark energy models (XCDM, Dvali-Gabadadze-Porrati, and Ricci dark energy models), in a spatially flat universe. The likelihood is maximized for {Omega}_{Lambda}_=0.70+/-0.09 when considering the sample excluding the Sloan Lens ACS systems (known to be biased toward large image-separation lenses) and no-evolution, and {Omega}_{Lambda}_=0.81+/-0.05 when limiting to gravitational lenses with image separation {Delta}{theta}>2" and no-evolution. In both cases, results accounting for galaxy evolution are consistent within 1{sigma}. The present test supports the accelerated expansion, by excluding the null hypothesis (i.e., {Omega}_{Lambda}_=0) at more than 4{sigma}, regardless of the chosen sample and assumptions on the galaxy evolution. A comparison between competitive world models is performed by means of the Bayesian information criterion. This shows that the simplest cosmological constant model--that has only one free parameter--is still preferred by the available data on the redshift distribution of gravitational lenses. We perform an analysis of the possible systematic effects, finding that the systematic errors due to sample incompleteness, galaxy evolution, and model uncertainties approximately equal the statistical errors, with present-day data. We find that the largest sources of systemic errors are the dynamical normalization and the high-velocity cutoff factor, followed by the faint-end slope of the velocity dispersion function.
- ID:
- ivo://CDS.VizieR/J/ApJ/890/148
- Title:
- Concentration-mass relation for XXL clusters
- Short Name:
- J/ApJ/890/148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a weak-lensing analysis of X-ray galaxy groups and clusters selected from the XMM-XXL survey using the first-year data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program. Our joint weak-lensing and X-ray analysis focuses on 136 spectroscopically confirmed X-ray-selected systems at 0.031<=z<=1.033 detected in the 25deg^2^ XXL-N region, which largely overlaps with the HSC-XMM field. With high-quality HSC weak-lensing data, we characterize the mass distributions of individual clusters and establish the concentration-mass (c-M) relation for the XXL sample, by accounting for selection bias and statistical effects and marginalizing over the remaining mass calibration uncertainty. We find the mass-trend parameter of the c-M relation to be {beta}=-0.07+/-0.28 and the normalization to be c_200_=4.8+/-1.0(stat)+/-0.8(syst) at M_200_=10^14^h^-1^M_{sun}_ and z=0.3. We find no statistical evidence for redshift evolution. Our weak-lensing results are in excellent agreement with dark-matter-only c-M relations calibrated for recent {Lambda}CDM cosmologies. The level of intrinsic scatter in c200 is constrained as {sigma}(lnc_200_)<24% (99.7% CL), which is smaller than predicted for the full population of {Lambda}CDM halos. This is likely caused in part by the X-ray selection bias in terms of the cool-core or relaxation state. We determine the temperature-mass (T_X_-M_500_) relation for a subset of 105 XXL clusters that have both measured HSC lensing masses and X-ray temperatures. The resulting TX-M500 relation is consistent with the self-similar prediction. Our TX-M500 relation agrees with the XXL DR1 results at group scales but has a slightly steeper mass trend, implying a smaller mass scale in the cluster regime. The overall offset in the TX-M500 relation is at the ~1.5{sigma} level, corresponding to a mean mass offset of 34%+/-20%. We also provide bias-corrected, weak-lensing-calibrated M200 and M500 mass estimates of individual XXL clusters based on their measured X-ray temperatures.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A40
- Title:
- Cosmic Horseshoe (J1148+1930) Ha and OIII spectra
- Short Name:
- J/A+A/631/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed analysis of the inner mass structure of the Cosmic Horseshoe (J1148+1930) strong gravitational lens system observed with the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3). In addition to the spectacular Einstein ring, this systems shows a radial arc. We obtained the redshift of the radial arc counter image z_s,r_=1.961+/-0.001 from Gemini observations. To disentangle the dark and luminous matter, we consider three different profiles for the dark matter distribution: a power-law profile, the NFW, and a generalized version of the NFW profile. For the luminous matter distribution, we base it on the observed light distribution that is fitted with three components: a point mass for the central light component resembling an active galactic nucleus, and the remaining two extended light components scaled by a constant M/L. To constrain the model further, we include published velocity dispersion measurements of the lens galaxy and perform a self-consistent lensing and axisymmetric Jeans dynamical modeling. Our model fits well to the observations including the radial arc, independent of the dark matter profile. Depending on the dark matter profile, we get a dark matter fraction between 60% and 70%. With our composite mass model we find that the radial arc helps to constrain the inner dark matter distribution of the Cosmic Horseshoe independently of the dark matter profile.
