- ID:
- ivo://CDS.VizieR/J/AJ/155/104
- Title:
- MEGaSaURA. I. The sample and the spectra
- Short Name:
- J/AJ/155/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We introduce Project MEGaSaURA: the Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas. MEGaSaURA comprises medium-resolution, rest-frame ultraviolet spectroscopy of N=15 bright gravitationally lensed galaxies at redshifts of 1.68<z<3.6, obtained with the MagE spectrograph on the Magellan telescopes. The spectra cover the observed-frame wavelength range 3200<{lambda}_o_<8280{AA}; the average spectral resolving power is R=3300. The median spectrum has a signal-to- noise ratio (S/N)=21 per resolution element at 5000{AA}. As such, the MEGaSaURA spectra have superior S/N and wavelength coverage compared to what COS/HST provides for starburst galaxies in the local universe. This paper describes the sample, the observations, and the data reduction. We compare the measured redshifts for the stars, the ionized gas as traced by nebular lines, and the neutral gas as traced by absorption lines; we find the expected bulk outflow of the neutral gas, and no systemic offset between the redshifts measured from nebular lines and the redshifts measured from the stellar continuum.
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- ID:
- ivo://CDS.VizieR/J/A+A/630/A108
- Title:
- MG B2016+112 radio images
- Short Name:
- J/A+A/630/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we exploit the gravitational lensing effect to detect proper motion in the highly magnified gravitationally lensed source MG B2016+112. We find positional shifts up to 6mas in the lensed images by comparing two very long baseline interferometric (VLBI) radio observations at 1.7GHz that are separated by 14.359 years, and provide an astrometric accuracy of the order of tens of as. From lens modelling, we exclude a shift in the lensing galaxy as the cause of the positional change of the lensed images, and we assign it to the background source. The source consists of four sub-components, separated by 175 pc, with proper motion of the order of tens {mu}as/yr for the two components at highest magnification ({mu}~350) and of the order of a few mas/yr for the two components at lower magnification ({mu}~2). We propose single Active Galactic Nuclei (AGN) and dual AGN scenarios to explain the source plane. Although, the latter interpretation is supported by the archival multi-wavelength properties of the object. In this case, MG B2016+112 would represent the highest redshift dual radio-loud AGN system discovered thus far, and would support the merger interpretation for such systems. Also, given the low probability (~10^-5^) of detecting a dual AGN system that is also gravitationally lensed, if confirmed, this would suggest that such dual AGN systems must be more abundant in the early Universe than currently thought.
- ID:
- ivo://CDS.VizieR/J/ApJS/249/16
- Title:
- Microlensing event in the OGLE-IV GVS survey
- Short Name:
- J/ApJS/249/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Searches for gravitational microlensing events are traditionally concentrated on the central regions of the Galactic bulge but many microlensing events are expected to occur in the Galactic plane, far from the Galactic Center. Owing to the difficulty in conducting high-cadence observations of the Galactic plane over its vast area, which are necessary for the detection of microlensing events, their global properties were hitherto unknown. Here, we present results of the first comprehensive search for microlensing events in the Galactic plane. We searched an area of almost 3000 square degrees along the Galactic plane (|b|<7{deg}, 0{deg}<l<50{deg}, 190{deg}<l<360{deg}) observed by the Optical Gravitational Lensing Experiment (OGLE) during 2013-2019 and detected 630 events. We demonstrate that the mean Einstein timescales of Galactic plane microlensing events are on average three times longer than those of Galactic bulge events, with little dependence on the Galactic longitude. We also measure the microlensing optical depth and event rate as a function of Galactic longitude and demonstrate that they exponentially decrease with the angular distance from the Galactic Center (with the characteristic angular scale length of 32{deg}). The average optical depth decreases from 0.5x10^-6^ at l=10{deg} to 1.5x10^-8^ in the Galactic anticenter. We also find that the optical depth in the longitude range 240{deg}<l<330{deg} is asymmetric about the Galactic equator, which we interpret as a signature of the Galactic warp.
- ID:
- ivo://CDS.VizieR/J/ApJ/778/150
- Title:
- Microlensing events toward the Bulge from MOA-II
- Short Name:
- J/ApJ/778/150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the microlensing optical depth and event rate toward the Galactic Bulge (GB) based on two years of the MOA-II survey. This sample contains ~1000 microlensing events, with an Einstein radius crossing time of t_E_<=200 days in 22 bulge fields covering ~42deg^2^ between -5{deg}<l<10{deg} and -7{deg}<b<-1{deg}. Our event rate and optical depth analysis uses 474 events with well-defined microlensing parameters. In the central fields with |l|<5{deg}, we find an event rate of {Gamma}=[2.39+/-1.1]e^[0.60+/-0.05](3-|b|)^x10^-5^/star/yr and an optical depth (for events with t_E_<=200days) of {tau}_200_=[2.35+/-0.18]e^[0.51+/-0.07](3-|b|)^x10^-6^ for the 427 events, using all sources brighter than I_s_<=20mag. The distribution of observed fields is centered at (l,b)=(0.{deg}38, -3.{deg}72). We find that the event rate is maximized at low latitudes and a longitude of l{approx}1{deg}. For the 111 events in 3.2deg^2^ of the central GB at |b|<=3.{deg}0 and 0.{deg}0<=l<=2.{deg}0, centered at (l,b)=(0.{deg}97, -2.{deg}26), we find {Gamma}=4.57_-0.46_^+0.51^x10^-5^/star/yr and {tau}_200_=3.64_-0.45_^+0.51^x10^-6^. We also consider a red clump giant (RCG) star sample with I_s_<17.5, and we find that the event rate for the RCG sample is slightly lower than but consistent with the all-source event rate. The main difference is the lack of long duration events in the RCG sample due to a known selection effect. Our results are consistent with previous optical depth measurements, but they are somewhat lower than previous all-source measurements, and slightly higher than previous RCG optical depth measurements. This suggests that the previously observed difference in optical depth measurements between all-source and RCG samples may largely be due to statistical fluctuations. These event rate measurements toward the central GB are necessary to predict the microlensing event rate and to optimize the survey fields in future space missions such as Wide Field Infrared Space Telescope.
- ID:
- ivo://CDS.VizieR/J/ApJS/244/29
- Title:
- Microlensing events toward the Galactic bulge
- Short Name:
- J/ApJS/244/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The number and properties of observed gravitational microlensing events depend on the distribution and kinematics of stars and other compact objects along the line of sight. In particular, precise measurements of the microlensing optical depth and event rate toward the Galactic bulge enable strict tests of competing models of the Milky Way. Previous estimates, based on samples of up to a few hundred events, gave larger values than expected from the Galactic models and were difficult to reconcile with other constraints on the Galactic structure. Here we used long-term photometric observations of the Galactic bulge by the Optical Gravitational Lensing Experiment (OGLE) to select a homogeneous sample of 8000 gravitational microlensing events. We created the largest and most accurate microlensing optical depth and event rate maps of the Galactic bulge. The new maps ease the tension between the previous measurements and Galactic models. They are consistent with some earlier calculations based on bright stars and are systematically ~30% smaller than the other estimates based on "all-source" samples of microlensing events. The difference is caused by the careful estimation of the source star population. The new maps agree well with predictions based on the Besancon model of the Galaxy. Apart from testing the Milky Way models, our maps may have numerous other applications, such as the measurement of the initial mass function or constraining the dark matter content in the Milky Way center. The new maps will also inform the planning of future space-based microlensing experiments by revising the expected number of events.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A53
- Title:
- Microlensing maps for a cusp configuration
- Short Name:
- J/A+A/553/A53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We provide the microlensing maps generated to study microlensing in the mid-infrared range for a cusp-configuration lensed AGN. The maps provided correspond to images which are respectively saddle-point and minimum of the arrival time surface. We also provide simulated images of sources with a disc-like brightness profile or a ring-like brightness profile corresponding to an accretion disc or a torus brightness distribution. These source profiles should be convolved with microlensing maps of the same spatial resolution to simulate microlensing of the corresponding source and generate probability density function (PDF) of microlensing similar to those shown in Figures 3,4,5,8. These maps can also be used to generate synthetic microlensing lightcurves (Figure 9) or derive PDF for the Rcusp relation (Figure 10).
- ID:
- ivo://CDS.VizieR/J/ApJ/827/139
- Title:
- Microlensing optical depth & event rates from MOA-II
- Short Name:
- J/ApJ/827/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We find that significant incompleteness in stellar number counts results in a significant overestimate of the microlensing optical depth {tau} and event rate per star per year {Gamma} toward the Galactic bulge from the first two years of the MOA-II survey. We find that the completeness in red clump giant (RCG) counts f_RC_ decreases proportional to the galactic latitude b, as f_RC_=(0.63+/-0.11)-(0.052+/-0.028)xb, ranging between 1 and 0.7 at b=-6{deg}~-1.5{deg}. The previous measurements using all sources by difference image analysis (DIA) by MACHO and MOA-I suffer the same bias. On the other hand, the measurements using an RCG sample by OGLE-II, MACHO, and EROS were free from this bias because they selected only the events associated with the resolved stars. Thus, the incompleteness both in the number of events and stellar number count cancel out. We estimate {tau} and {Gamma} by correcting this incompleteness. In the central fields with |l|<5{deg}, we find {Gamma}=[18.74+/-0.91]x10^-6^exp[(0.53+/-0.05)(3-|b|)]/star/yr and {tau}_200_=[1.84+/-0.14]x10^-6^exp[(0.44+/-0.07)(3-|b|)] for the 427 events with t_E_<=200 days using all sources brighter than I_s_<=20mag. Our revised all-source {tau} measurements are about 2{sigma} smaller than the other all-source measurements and are consistent with the RCG measurements within 1{sigma}. We conclude that the long-standing problem on discrepancy between the high {tau} with all-source samples by DIA and low {tau} with RCG samples can probably be explained by the incompleteness of the stellar number count. A model fit to these measurements predicts {Gamma}=4.60+/-0.25x10^-5^/star/yr at |b|~-1.4{deg} and -2.25{deg}<l<3.75{deg} for sources with I<=20, where the future space mission, Wide Field Infrared Space Telescope, will observe.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/5104
- Title:
- Model selection with strong-lensing systems
- Short Name:
- J/MNRAS/478/5104
- Date:
- 10 Dec 2021 13:55:35
- Publisher:
- CDS
- Description:
- In this paper, we use an unprecedentedly large sample (158) of confirmed strong lens systems for model selection, comparing five well-studied Friedmann-Robertson-Walker cosmologies: {Lambda}CDM, wCDM (the standard model with a variable dark-energy equation of state), the R_h_=ct universe, the (empty) Milne cosmology, and the classical Einstein-de Sitter (matter-dominated) universe. We first use these sources to optimize the parameters in the standard model and show that they are consistent with Planck, though the quality of the best fit is not satisfactory. We demonstrate that this is likely due to underreported errors, or to errors yet to be included in this kind of analysis. We suggest that the missing dispersion may be due to scatter about a pure single isothermal sphere (SIS) model that is often assumed for the mass distribution in these lenses. We then use the Bayes information criterion, with the inclusion of a suggested SIS dispersion, to calculate the relative likelihoods and ranking of these models, showing that Milne and Einstein-de Sitter are completely ruled out, while R_h_=ct is preferred over {Lambda}CDM/wCDM with a relative probability of ~73 percent versus ~24 percent. The recently reported sample of new strong lens candidates by the Dark Energy Survey, if confirmed, may be able to demonstrate which of these two models is favoured over the other at a level exceeding 3{sigma}.
- ID:
- ivo://CDS.VizieR/J/ApJ/873/117
- Title:
- Monitoring of the double quasar SDSS J1442+4055
- Short Name:
- J/ApJ/873/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present r-band photometric monitoring of the two images, A and B, of the gravitationally lensed quasar SDSS J1442+4055 using the Liverpool Telescope (LT). From the LT light curves between 2015 December and 2018 August, we derive at once a time delay of 25.0+/-1.5d (1{sigma} confidence interval; A is leading) and microlensing magnification gradients below 10^-4^mag/d. The delay interval is not expected to be affected by an appreciable microlensing-induced bias, so it can be used to estimate cosmological parameters. This paper also focuses on new Gran Telescopio Canarias (GTC) and LT spectroscopic observations of the lens system. We determine the redshift of two bright galaxies around the doubly imaged quasar using LT spectroscopy, while GTC data lead to low-noise individual spectra of A, B, and the main lensing galaxy, G1. The G1 spectral shape is accurately matched to an early-type galaxy template at z=0.284, and it has potential for further relevant studies. Additionally, the quasar spectra show absorption by metal-rich gas at z~2. This dusty absorber is responsible for an extinction bump at a rest-frame wavelength of 2209+/-2{AA}, which has strengths of ~0.47 and 0.76mag/{mu}m for A and B, respectively. In such an intervening system, the dust-to-gas ratio, gas-phase metallicity indicator [Zn/H], and dust depletion level [Fe/Zn] are relatively high.
- ID:
- ivo://CDS.VizieR/J/ApJ/897/180
- Title:
- Multiband photometry of microlensing event Kojima-1
- Short Name:
- J/ApJ/897/180
- Date:
- 16 Mar 2022 00:48:14
- Publisher:
- CDS
- Description:
- We report the lens mass and distance measurements of the nearby microlensing event TCPJ05074264+2447555 (Kojima-1). We measure the microlens parallax vector {pi}_E_ using Spitzer and ground-based light curves with constraints on the direction of lens-source relative proper motion derived from Very Large Telescope Interferometer (VLTI) GRAVITY observations. Combining this {pi}_E_ determination with the angular Einstein radius {theta}_E_ measured by VLTI-GRAVITY observations, we find that the lens is a star with mass M_L_=0.495{+/-}0.063M{odot} at a distance DL=429{+/-}21pc. We find that the blended light basically all comes from the lens. The lens-source proper motion is {mu}_rel,hel_=26.55{+/-}0.36mas/yr, so with currently available adaptive-optics instruments, the lens and source can be resolved in 2021. This is the first microlensing event whose lens mass is unambiguously measured by interferometry+satellite-parallax observations, which opens a new window for mass measurements of isolated objects such as stellar-mass black holes.
