scholarly journals The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2016 follow-up campaign. II. New quasar lenses from double component fitting.

2018 ◽  
Author(s):  
T Anguita ◽  
P L Schechter ◽  
N Kuropatkin ◽  
N D Morgan ◽  
F Ostrovski ◽  
...  
Keyword(s):  
Dark Energy ◽  
Dark Energy Survey ◽  
Strong Lensing ◽  
Energy Survey

scholarly journals The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2017/2018 follow-up campaign: discovery of 10 lensed quasars and 10 quasar pairs

2020 ◽  
Vol 494 (3) ◽  
pp. 3491-3511 ◽  
Author(s):  
C Lemon ◽  
M W Auger ◽  
R McMahon ◽  
T Anguita ◽  
Y Apostolovski ◽  
...  
Keyword(s):  
Dark Energy ◽  
Near Infrared ◽  
Infrared Camera ◽  
Variable Component ◽  
Star Forming ◽  
Dark Energy Survey ◽  
Faint Object ◽  
Strong Lensing ◽  
Energy Survey

ABSTRACT We report the results of the STRong lensing Insights into the Dark Energy Survey (STRIDES) follow-up campaign of the late 2017/early 2018 season. We obtained spectra of 65 lensed quasar candidates with ESO Faint Object Spectrograph and Camera 2 on the NTT and Echellette Spectrograph and Imager on Keck, confirming 10 new lensed quasars and 10 quasar pairs. Eight lensed quasars are doubly imaged with source redshifts between 0.99 and 2.90, one is triply imaged (DESJ0345−2545, z = 1.68), and one is quadruply imaged (quad: DESJ0053−2012, z = 3.8). Singular isothermal ellipsoid models for the doubles, based on high-resolution imaging from SAMI on Southern Astrophysical Research Telescope or Near InfraRed Camera 2 on Keck, give total magnifications between 3.2 and 5.6, and Einstein radii between 0.49 and 1.97 arcsec. After spectroscopic follow-up, we extract multi-epoch grizY photometry of confirmed lensed quasars and contaminant quasar + star pairs from DES data using parametric multiband modelling, and compare variability in each system’s components. By measuring the reduced χ2 associated with fitting all epochs to the same magnitude, we find a simple cut on the less variable component that retains all confirmed lensed quasars, while removing 94 per cent of contaminant systems. Based on our spectroscopic follow-up, this variability information improves selection of lensed quasars and quasar pairs from 34-45 per cent to 51–70 per cent, with most remaining contaminants being star-forming galaxies. Using mock lensed quasar light curves we demonstrate that selection based only on variability will over-represent the quad fraction by 10 per cent over a complete DES magnitude-limited sample, explained by the magnification bias and hence lower luminosity/more variable sources in quads.

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 On building a cluster watchlist for identifying strongly lensed supernovae, gravitational waves and kilonovae

2020 ◽  
Vol 495 (2) ◽  
pp. 1666-1671 ◽  
Author(s):  
Dan Ryczanowski ◽  
Graham P Smith ◽  
Matteo Bianconi ◽  
Richard Massey ◽  
Andrew Robertson ◽  
...  
Keyword(s):  
Dark Energy ◽  
Gravitational Waves ◽  
Lower Limit ◽  
High Redshift ◽  
Early Data ◽  
Source Plane ◽  
Dark Energy Survey ◽  
Strong Lensing ◽  
Cluster Properties ◽  
Energy Survey

ABSTRACT Motivated by discovering strongly lensed supernovae, gravitational waves, and kilonovae in the 2020s, we investigate whether to build a watchlist of clusters based on observed cluster properties (i.e. lens-plane selection) or on the detectability of strongly lensed background galaxies (i.e. source-plane selection). First, we estimate the fraction of high-redshift transient progenitors that reside in galaxies that are themselves too faint to be detected as being strongly lensed. We find ∼15–50 per cent of transient progenitors reside in z = 1 − 2 galaxies too faint to be detected in surveys that reach AB ≃ 23, such as the Dark Energy Survey. This falls to ≲10 per cent at depths that will be probed by early data releases of LSST (AB ≃ 25). Secondly, we estimate a conservative lower limit on the fraction of strong-lensing clusters that will be missed by magnitude-limited searches for multiply imaged galaxies and giant arcs due to the faintness of such images. We find that DES-like surveys will miss ∼75 per cent of 1015 M⊙ strong-lensing clusters, rising to ∼100 per cent of 1014 M⊙ clusters. Deeper surveys, such as LSST, will miss ∼40 per cent at 1015 M⊙ and ∼95 per cent at 1014 M⊙. Our results motivate building a cluster watchlist for strongly lensed transients that includes those found by the lens-plane selection.

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 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.

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