scholarly journals Observation and confirmation of nine strong-lensing systems in Dark Energy Survey Year 1 data

2020 ◽  
Vol 494 (1) ◽  
pp. 1308-1322
Author(s):  
B Nord ◽  
E Buckley-Geer ◽  
H Lin ◽  
N Kuropatkin ◽  
T Collett ◽  
...  
Keyword(s):  
Dark Energy ◽  
Surface Brightness ◽  
Spectroscopic Properties ◽  
Source Image ◽  
Gravitational Lenses ◽  
Redshift Range ◽  
Photometric Redshift ◽  
Dark Energy Survey ◽  
Energy Survey

ABSTRACT We describe the observation and confirmation of nine new strong gravitational lenses discovered in Year 1 data from the Dark Energy Survey (DES). We created candidate lists based on (i) galaxy group and cluster samples, and (ii) photometrically selected galaxy samples. We selected 46 candidates through visual inspection and then used the Gemini Multi-Object Spectrograph(GMOS) at the Gemini South telescope to acquire a spectroscopic follow-up of 21 of these candidates. Through an analysis of these spectroscopic follow-up data, we confirmed nine new lensing systems and rejected two candidates, and the analysis was inconclusive on 10 candidates. For each of the confirmed systems, our report measured spectroscopic properties, estimated source image–lens separations, and estimated enclosed masses as well. The sources that we targeted have an i-band surface brightness range of $i_{\rm SB} \sim 22\!-\!24\, {\rm mag}\,{\rm arcsec}^{-2}$ and a spectroscopic redshift range of zspec ∼ 0.8−2.6. The lens galaxies have a photometric redshift range of zlens ∼ 0.3−0.7. The lensing systems range in source image–lens separation from 2 to 9 arcsec and in enclosed mass from 1012 to 1013 M⊙.

scholarly journals Spectroscopic confirmation and modelling of two lensed quadruple quasars in the Dark Energy Survey public footprint

2019 ◽  
Vol 485 (4) ◽  
pp. 5086-5095
Author(s):  
C Spiniello ◽  
A V Sergeyev ◽  
L Marchetti ◽  
C Tortora ◽  
N R Napolitano ◽  
...  
Keyword(s):  
Dark Energy ◽  
Velocity Dispersion ◽  
Gravitational Lenses ◽  
Intrinsic Variability ◽  
Apparent Brightness ◽  
Dark Energy Survey ◽  
Stellar Velocity ◽  
Energy Survey

ABSTRACT Quadruply lensed quasars are extremely rare objects, but incredibly powerful cosmological tools. Only few dozen are known in the whole sky. Here we present the spectroscopic confirmation of two new quadruplets WG0214-2105 and WG2100-4452 discovered by Agnello & Spiniello (2018) within the Dark Energy Survey public footprints. We have conducted spectroscopic follow-up of these systems with the Southern African Large Telescope as part of a program that aims at confirming the largest possible number of strong gravitational lenses in the equatorial and Southern hemisphere. For both systems, we present the sources spectra that allowed us to estimate their redshifts and unambiguously confirm their lensing nature. For the brighter deflector (WG2100-4452) we measure the spectroscopic redshift and the stellar velocity dispersion from optical absorption lines in the spectrum. For the other system we infer the lens redshift from photometry, being the quality of the spectra not good enough. We obtain photometry for both lenses, directly from multiband images, isolating the lenses from the quasars. One of the quadruplets, WG0214-2105, was also observed by Pan-STARRS, allowing us to estimate the apparent brightness of each quasar image at two different epochs, and thus to find evidence for flux variability. This result could suggest a microlensing event for the faintest components, although intrinsic variability cannot be excluded with only two epochs. Finally, we present simple lens models for both quadruplets, obtaining Einstein radii, singular isothermal ellipsoid velocity dispersions, ellipticities, and position angles of the lenses, as well as time-delay predictions assuming a concordance cosmological model.

scholarly journals DESAlert: Enabling Real-Time Transient Follow-Up with Dark Energy Survey Data

2016 ◽  
Vol 33 ◽  
Author(s):  
A. Poci ◽  
K. Kuehn ◽  
T. Abbott ◽  
F. B. Abdalla ◽  
S. Allam ◽  
...  
Keyword(s):  
Dark Energy ◽  
Real Time ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Host Galaxies ◽  
Gamma Ray Burst ◽  
Dark Energy Survey ◽  
Data Products ◽  
Energy Survey

AbstractThe Dark Energy Survey is undertaking an observational programme imaging 1/4 of the southern hemisphere sky with unprecedented photometric accuracy. In the process of observing millions of faint stars and galaxies to constrain the parameters of the dark energy equation of state, the Dark Energy Survey will obtain pre-discovery images of the regions surrounding an estimated 100 gamma-ray bursts over 5 yr. Once gamma-ray bursts are detected by, e.g., the Swift satellite, the DES data will be extremely useful for follow-up observations by the transient astronomy community. We describe a recently-commissioned suite of software that listens continuously for automated notices of gamma-ray burst activity, collates information from archival DES data, and disseminates relevant data products back to the community in near-real-time. Of particular importance are the opportunities that non-public DES data provide for relative photometry of the optical counterparts of gamma-ray bursts, as well as for identifying key characteristics (e.g., photometric redshifts) of potential gamma-ray burst host galaxies. We provide the functional details of the DESAlert software, and its data products, and we show sample results from the application of DESAlert to numerous previously detected gamma-ray bursts, including the possible identification of several heretofore unknown gamma-ray burst hosts.

scholarly journals Dark Energy Survey Year 1 results: validation of weak lensing cluster member contamination estimates from P(z) decomposition

2019 ◽  
Vol 489 (2) ◽  
pp. 2511-2524 ◽  
Author(s):  
T N Varga ◽  
J DeRose ◽  
D Gruen ◽  
T McClintock ◽  
S Seitz ◽  
...  
Keyword(s):  
Dark Energy ◽  
Decomposition Method ◽  
Weak Lensing ◽  
Cluster Member ◽  
Photometric Redshift ◽  
Cluster Mass ◽  
Dark Energy Survey ◽  
Mass Calibration ◽  
The Masses ◽  
Energy Survey

ABSTRACT Weak lensing source galaxy catalogues used in estimating the masses of galaxy clusters can be heavily contaminated by cluster members, prohibiting accurate mass calibration. In this study, we test the performance of an estimator for the extent of cluster member contamination based on decomposing the photometric redshift P(z) of source galaxies into contaminating and background components. We perform a full scale mock analysis on a simulated sky survey approximately mirroring the observational properties of the Dark Energy Survey Year One observations (DES Y1), and find excellent agreement between the true number profile of contaminating cluster member galaxies in the simulation and the estimated one. We further apply the method to estimate the cluster member contamination for the DES Y1 redMaPPer cluster mass calibration analysis, and compare the results to an alternative approach based on the angular correlation of weak lensing source galaxies. We find indications that the correlation based estimates are biased by the selection of the weak lensing sources in the cluster vicinity, which does not strongly impact the P(z) decomposition method. Collectively, these benchmarks demonstrate the strength of the P(z) decomposition method in alleviating membership contamination and enabling highly accurate cluster weak lensing studies without broad exclusion of source galaxies, thereby improving the total constraining power of cluster mass calibration via weak lensing.

scholarly journals DESGW Optical Follow-up of BBH LIGO-Virgo Events with DECam

2017 ◽  
Vol 13 (S338) ◽  
pp. 61-64
Author(s):  
Robert E. Butler ◽  
M. Soares-Santos ◽  
J. Annis ◽  
K. Herner ◽  
Keyword(s):  
Black Hole ◽  
Dark Energy ◽  
Neutron Star ◽  
Optical Emission ◽  
Binary Neutron Star ◽  
Dark Energy Survey ◽  
Binary Black Hole ◽  
The Status ◽  
Energy Survey

AbstractThe DESGW program is a collaboration between members of the Dark Energy Survey, the wider astronomical community, and the LIGO-Virgo Collaboration to search for optical counterparts of gravitational wave events, such as those expected from binary neutron star mergers or neutron star-black hole mergers. While binary black hole (BBH) events are not expected to produce an electromagnetic (EM) signature, emission is certainly not impossible. The DESGW program has performed follow-up observations of four BBH events detected by LIGO in order to search for any possible EM counterpart. Failure to find such counterparts is still relevant in that it produces limits on optical emission from such events. This is a review of follow-up results from O1 BBH events and a discussion of the status of ongoing uniform re-analysis of all BBH events that DESGW has followed up to date.

scholarly journals Constraints on the Physical Properties of GW190814 through Simulations Based on DECam Follow-up Observations by the Dark Energy Survey

2020 ◽  
Vol 901 (1) ◽  
pp. 83 ◽  
Author(s):  
R. Morgan ◽  
M. Soares-Santos ◽  
J. Annis ◽  
K. Herner ◽  
A. Garcia ◽  
...  
Keyword(s):  
Dark Energy ◽  
Physical Properties ◽  
Dark Energy Survey ◽  
Energy Survey

scholarly journals Deep SOAR follow-up photometry of two Milky Way outer-halo companions discovered with Dark Energy Survey

2018 ◽  
Vol 478 (2) ◽  
pp. 2006-2018 ◽  
Author(s):  
E Luque ◽  
B Santiago ◽  
A Pieres ◽  
J L Marshall ◽  
A B Pace ◽  
...  
Keyword(s):  
Dark Energy ◽  
Milky Way ◽  
Dark Energy Survey ◽  
Energy Survey

scholarly journals Quasar lenses in the south: searches over the DES public footprint

2019 ◽  
Vol 489 (2) ◽  
pp. 2525-2535 ◽  
Author(s):  
Adriano Agnello ◽  
Chiara Spiniello
Keyword(s):  
Dark Energy ◽  
Selection Criteria ◽  
High Grade ◽  
X Ray ◽  
Dark Energy Survey ◽  
Public Data ◽  
Data Release ◽  
Energy Survey ◽  
Selection Of

ABSTRACT We have scanned 5000 deg2 of Southern Sky to search for strongly lensed quasars with five methods, all source oriented, but based on different assumptions and selection criteria. We present a list of high-grade candidates from each method (totalling 98 unique, new candidates), to facilitate follow-up spectroscopic campaigns, including two previously unknown quadruplets, WG 210014.9-445206.4 and WG 021416.37-210535.3. We analyse morphological searches based on Gaia multiplet detection and astrometric offsets, fibre-spectroscopic pre-selection, and X-ray and radio pre-selection. The performance and complementarity of the methods are evaluated on a common sample of known lenses in the Dark Energy Survey public Data Release 1 (DR1) footprint. We recovered in total 13 known lenses, of which 8 are quadruplets. Morphological and colour selection of objects, from the WISE andGaia-DR2 surveys, recovers most of those known lenses, but searches in the radio and X-ray cover regimes that are beyond the completeness of Gaia. Given the footprint, pre-selection, and depth limits, the current number of quads indicates that the union of these searches is complete, and the expected purity on high-grade candidates is ${\approx}60{{\ \rm per\ cent}}$. Ongoing, spectroscopic campaigns confirm this estimate.

scholarly journals The Evolutionary Map of the Universe pilot survey

2021 ◽  
Vol 38 ◽  
Author(s):  
Ray P. Norris ◽  
Joshua Marvil ◽  
J. D. Collier ◽  
Anna D. Kapińska ◽  
Andrew N. O’Brien ◽  
...  
Keyword(s):  
Dark Energy ◽  
Surface Brightness ◽  
High Sensitivity ◽  
Single Component ◽  
Pilot Survey ◽  
Dark Energy Survey ◽  
Low Surface Brightness ◽  
Energy Survey ◽  
The Universe ◽  
Initial Results

Abstract We present the data and initial results from the first pilot survey of the Evolutionary Map of the Universe (EMU), observed at 944 MHz with the Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The survey covers $270 \,\mathrm{deg}^2$ of an area covered by the Dark Energy Survey, reaching a depth of 25–30 $\mu\mathrm{Jy\ beam}^{-1}$ rms at a spatial resolution of $\sim$ 11–18 arcsec, resulting in a catalogue of $\sim$ 220 000 sources, of which $\sim$ 180 000 are single-component sources. Here we present the catalogue of single-component sources, together with (where available) optical and infrared cross-identifications, classifications, and redshifts. This survey explores a new region of parameter space compared to previous surveys. Specifically, the EMU Pilot Survey has a high density of sources, and also a high sensitivity to low surface brightness emission. These properties result in the detection of types of sources that were rarely seen in or absent from previous surveys. We present some of these new results here.

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