We perform a comprehensive study of Milky Way (MW) satellite galaxies to constrain the fundamental properties of dark matter (DM). This analysis fully incorporates inhomogeneities in the spatial ...distribution and detectability of MW satellites and marginalizes over uncertainties in the mapping between galaxies and DM halos, the properties of the MW system, and the disruption of subhalos by the MW disk. Our results are consistent with the cold, collisionless DM paradigm and yield the strongest cosmological constraints to date on particle models of warm, interacting, and fuzzy dark matter. At 95% confidence, we report limits on (i) the mass of thermal relic warm DM, m_{WDM}>6.5 keV (free-streaming length, λ_{fs}≲10h^{-1} kpc), (ii) the velocity-independent DM-proton scattering cross section, σ_{0}<8.8×10^{-29} cm^{2} for a 100 MeV DM particle mass DM-proton coupling, c_{p}≲(0.3 GeV)^{-2}, and (iii) the mass of fuzzy DM, m_{ϕ}>2.9×10^{-21} eV (de Broglie wavelength, λ_{dB}≲0.5 kpc). These constraints are complementary to other observational and laboratory constraints on DM properties.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
This overview paper describes the legacy prospect and discovery potential of the Dark Energy Survey (DES) beyond cosmological studies, illustrating it with examples from the DES early data. DES is ...using a wide-field camera (DECam) on the 4 m Blanco Telescope in Chile to image 5000 sq deg of the sky in five filters (grizY). By its completion, the survey is expected to have generated a catalogue of 300 million galaxies with photometric redshifts and 100 million stars. In addition, a time-domain survey search over 27 sq deg is expected to yield a sample of thousands of Type Ia supernovae and other transients. The main goals of DES are to characterize dark energy and dark matter, and to test alternative models of gravity; these goals will be pursued by studying large-scale structure, cluster counts, weak gravitational lensing and Type Ia supernovae. However, DES also provides a rich data set which allows us to study many other aspects of astrophysics. In this paper, we focus on additional science with DES, emphasizing areas where the survey makes a difference with respect to other current surveys. The paper illustrates, using early data (from ‘Science Verification’, and from the first, second and third seasons of observations), what DES can tell us about the Solar system, the Milky Way, galaxy evolution, quasars and other topics. In addition, we show that if the cosmological model is assumed to be Λ+cold dark matter, then important astrophysics can be deduced from the primary DES probes. Highlights from DES early data include the discovery of 34 trans-Neptunian objects, 17 dwarf satellites of the Milky Way, one published z > 6 quasar (and more confirmed) and two published superluminous supernovae (and more confirmed).
ABSTRACT
This work presents the first search for RR Lyrae stars (RRLs) in four of the ultrafaint systems imaged by the Dark Energy Survey using SOAR/Goodman and Blanco/DECam imagers. We have detected ...two RRLs in the field of Grus I, none in Kim 2, one in Phoenix II, and four in Grus II. With the detection of these stars, we accurately determine the distance moduli for these ultrafaint dwarf satellite galaxies; μ0 = 20.51 ± 0.10 mag (D⊙ = 127 ± 6 kpc) for Grus I and μ0 = 20.01 ± 0.10 mag (D⊙ = 100 ± 5 kpc) for Phoenix II. These measurements are larger than previous estimations by Koposov et al. and Bechtol et al., implying larger physical sizes; 5 per cent for Grus I and 33 per cent for Phoenix II. For Grus II, of the four RRLs detected, one is consistent with being a member of the galactic halo (D⊙ = 24 ± 1 kpc, μ0 = 16.86 ± 0.10 mag), another is at D⊙ = 55 ± 2 kpc (μ0 = 18.71 ± 0.10 mag), which we associate with Grus II, and the two remaining at D⊙ = 43 ± 2 kpc (μ0 = 18.17 ± 0.10 mag). Moreover, the appearance of a subtle red horizontal branch in the colour–magnitude diagram of Grus II at the same brightness level of the latter two RRLs, which are at the same distance and in the same region, suggests that a more metal-rich system may be located in front of Grus II. The most plausible scenario is the association of these stars with the Chenab/Orphan Stream. Finally, we performed a comprehensive and updated analysis of the number of RRLs in dwarf galaxies. This allows us to predict that the method of finding new ultrafaint dwarf galaxies using two or more clumped RRLs will work only for systems brighter than MV ∼ −6 mag.
We present deep XMM–Newton European Photon Imaging Camera observations of the Wolf–Rayet (WR) bubble NGC 6888 around the star WR 136. The complete X-ray mapping of the nebula confirms the ...distribution of the hot gas in three maxima spatially associated with the caps and north-west blowout hinted at by previous Chandra observations. The global X-ray emission is well described by a two-temperature optically thin plasma model (T
1 = 1.4 × 106 K, T
2 = 8.2 × 106 K) with a luminosity of L
X = 7.8 × 1033 erg s−1 in the 0.3–1.5 keV energy range. The rms electron density of the X-ray-emitting gas is estimated to be n
e = 0.4 cm−3. The high-quality observations presented here reveal spectral variations within different regions in NGC 6888, which allowed us for the first time to detect temperature and/or nitrogen abundance inhomogeneities in the hot gas inside a WR nebula. One possible explanation for such spectral variations is that the mixing of material from the outer nebula into the hot bubble is less efficient around the caps than in other nebular regions.
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.
Small temperature anisotropies in the cosmic microwave background (CMB) can be sourced by density perturbations via the late-time integrated Sachs-Wolfe (ISW) effect. Large voids and superclusters ...are excellent environments to make a localized measurement of this tiny imprint. In some cases excess signals have been reported. We probed these claims with an independent data set, using the first year data of the Dark Energy Survey (DES) in a different footprint, and using a different superstructure finding strategy. We identified 52 large voids and 102 superclusters at redshifts 0.2 < z < 0.65. We used the Jubilee simulation to a priori evaluate the optimal ISW measurement configuration for our compensated top-hat filtering technique, and then performed a stacking measurement of the CMB temperature field based on the DES data. For optimal configurations, we detected a cumulative cold imprint of voids with ... -5.0 plus or minus 3.7 mu K and a hot imprint of superclusters ... 5.1 plus or minus 3.2 mu K; this is ~1.2s higher than the expected ... 0.6 mu K imprint of such superstructures in ... cold dark matter (...CDM). If we instead use an a posteriori selected filter size (R/Rv = 0.6), we can find a temperature decrement as large as ... -9.8 plus or minus 4.7 mu K for voids, which is ~2s above ...CDM expectations and is comparable to previous measurements made using Sloan Digital Sky Survey superstructure data. (ProQuest: ... denotes formulae/symbols omitted.)
We measure the correlation of galaxy lensing and cosmic microwave background lensing with a set of galaxies expected to trace the matter density field. The measurements are performed using pre-survey ...Dark Energy Survey (DES) Science Verification optical imaging data and millimetre-wave data from the 2500 sq. deg. South Pole Telescope Sunyaev–Zel'dovich (SPT-SZ) survey. The two lensing–galaxy correlations are jointly fit to extract constraints on cosmological parameters, constraints on the redshift distribution of the lens galaxies, and constraints on the absolute shear calibration of DES galaxy-lensing measurements. We show that an attractive feature of these fits is that they are fairly insensitive to the clustering bias of the galaxies used as matter tracers. The measurement presented in this work confirms that DES and SPT data are consistent with each other and with the currently favoured Λ cold dark matter cosmological model. It also demonstrates that joint lensing–galaxy correlation measurement considered here contains a wealth of information that can be extracted using current and future surveys.
Abstract
We present a detailed abundance analysis of the three brightest member stars at the top of the giant branch of the ultrafaint dwarf (UFD) galaxy Grus II. All stars exhibit a higher than ...expected Mg/Ca ratio compared to metal-poor stars in other UFD galaxies and in the Milky Way (MW) halo. Nucleosynthesis in high-mass (
20
M
⊙
) core-collapse supernovae has been shown to create this signature. The abundances of this small sample (three) stars suggests the chemical enrichment of Grus II could have occurred through substantial high-mass stellar evolution, and is consistent with the framework of a top-heavy initial mass function. However, with only three stars it cannot be ruled out that the abundance pattern is the result of a stochastic chemical enrichment at early times in the galaxy. The most metal-rich of the three stars also possesses a small enhancement in rapid neutron-capture (
r
-process) elements. The abundance pattern of the
r
-process elements in this star matches the scaled
r
-process pattern of the solar system and
r
-process enhanced stars in other dwarf galaxies and in the MW halo, hinting at a common origin for these elements across a range of environments. All current proposed astrophysical sites of
r
-process element production are associated with high-mass stars, thus the possible top-heavy initial mass function of Grus II would increase the likelihood of any of these events occurring. The time delay between the
α
and
r
-process element enrichment of the galaxy favors a neutron star merger as the origin of the
r
-process elements in Grus II.
ABSTRACT
We present an improved measurement of the Hubble constant (H0) using the ‘inverse distance ladder’ method, which adds the information from 207 Type Ia supernovae (SNe Ia) from the Dark ...Energy Survey (DES) at redshift 0.018 < z < 0.85 to existing distance measurements of 122 low-redshift (z < 0.07) SNe Ia (Low-z) and measurements of Baryon Acoustic Oscillations (BAOs). Whereas traditional measurements of H0 with SNe Ia use a distance ladder of parallax and Cepheid variable stars, the inverse distance ladder relies on absolute distance measurements from the BAOs to calibrate the intrinsic magnitude of the SNe Ia. We find H0 = 67.8 ± 1.3 km s−1 Mpc−1 (statistical and systematic uncertainties, 68 per cent confidence). Our measurement makes minimal assumptions about the underlying cosmological model, and our analysis was blinded to reduce confirmation bias. We examine possible systematic uncertainties and all are below the statistical uncertainties. Our H0 value is consistent with estimates derived from the Cosmic Microwave Background assuming a ΛCDM universe.
The Dark Energy Survey Data Release 2 Abbott, T. M. C.; Amon, A.; Avila, S. ...
The Astrophysical journal. Supplement series,
08/2021, Volume:
255, Issue:
2
Journal Article
Peer reviewed
Open access
Abstract
We present the second public data release of the Dark Energy Survey, DES DR2, based on optical/near-infrared imaging by the Dark Energy Camera mounted on the 4 m Blanco telescope at Cerro ...Tololo Inter-American Observatory in Chile. DES DR2 consists of reduced single-epoch and coadded images, a source catalog derived from coadded images, and associated data products assembled from 6 yr of DES science operations. This release includes data from the DES wide-area survey covering ∼5000 deg
2
of the southern Galactic cap in five broad photometric bands,
grizY
. DES DR2 has a median delivered point-spread function FWHM of
g
= 1.11″,
r
= 0.95″,
i
= 0.88″,
z
= 0.83″, and
Y
= 0.″90, photometric uniformity with a standard deviation of < 3 mmag with respect to Gaia DR2
G
band, a photometric accuracy of ∼11 mmag, and a median internal astrometric precision of ∼27 mas. The median coadded catalog depth for a 1.″95 diameter aperture at signal-to-noise ratio = 10 is
g
= 24.7,
r
= 24.4,
i
= 23.8,
z
= 23.1, and
Y
= 21.7 mag. DES DR2 includes ∼691 million distinct astronomical objects detected in 10,169 coadded image tiles of size 0.534 deg
2
produced from 76,217 single-epoch images. After a basic quality selection, benchmark galaxy and stellar samples contain 543 million and 145 million objects, respectively. These data are accessible through several interfaces, including interactive image visualization tools, web-based query clients, image cutout servers, and Jupyter notebooks. DES DR2 constitutes the largest photometric data set to date at the achieved depth and photometric precision.
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