90 research outputs found
Signatures of Self-Interacting Dark Matter in the Matter Power Spectrum and the CMB
We consider a self-interacting dark matter model in which the massive dark
photon mediating the self-interaction decays to light dark fermions to avoid
over-closing the universe. We find that if the model is constrained to explain
the dark matter halos inferred for spiral galaxies and galaxy clusters
simultaneously, there is a strong indication that dark matter is produced
asymmetrically in the early universe. It also implies the presence of dark
radiation, late kinetic decoupling for dark matter, and a suppressed linear
power spectrum due to dark acoustic damping. The Lyman- forest power
spectrum measurements put a strong upper limit on the damping scale and the
model has little room to reduce the abundances of satellite galaxies. Future
observations in the matter power spectrum and the CMB, in tandem with the
impact of self-interactions in galactic halos, makes it possible to measure the
gauge coupling and masses of the dark sector particles even when signals in
conventional dark matter searches are absent.Comment: 5 pages, 7 figures, published version in PL
Design and fabrication of robust broadband extreme ultraviolet multilayers
The random layer thickness variations can induce a great deformation of the
experimental reflection of broadband extreme ultraviolet multilayer. In order
to reduce this influence of random layer thickness fluctuations, the
multiobjective genetic algorithm has been improved and used in the robust
design of multilayer with a broad angular bandpass. The robust multilayer with
a lower sensitivity to random thickness errors have been obtained and the
corresponding multilayer mirrors were fabricated. The experimental results of
robust Mo/Si multilayer with a wide angular band were presented and analyzed,
and the advantage of robust multilayer design was demonstrated
The Flare and Warp of the Young Stellar Disk traced with LAMOST DR5 OB-type stars
We present analysis of the spatial density structure for the outer disk from
814 \,kpc with the LAMOST DR5 13534 OB-type stars and observe similar
flaring on north and south sides of the disk implying that the flaring
structure is symmetrical about the Galactic plane, for which the scale height
at different Galactocentric distance is from 0.14 to 0.5 \,kpc. By using the
average slope to characterize the flaring strength we find that the thickness
of the OB stellar disk is similar but flaring is slightly stronger compared to
the thin disk as traced by red giant branch stars, possibly implying that
secular evolution is not the main contributor to the flaring but perturbation
scenarios such as interactions with passing dwarf galaxies should be more
possible. When comparing the scale height of OB stellar disk of the north and
south sides with the gas disk, the former one is slightly thicker than the
later one by 33 and 9 \,pc, meaning that one could tentatively use
young OB-type stars to trace the gas properties. Meanwhile, we unravel that the
radial scale length of the young OB stellar disk is 1.17 0.05 \,kpc,
which is shorter than that of the gas disk, confirming that the gas disk is
more extended than stellar disk. What is more, by considering the mid-plane
displacements () in our density model we find that almost all of
are within 100 \,pc with the increasing trend as Galactocentric distance
increases.Comment: 14 pages and 8 figures, Accepted by APJ for publicatio
The LAMOST Survey of Background Quasars in the Vicinity of the Andromeda and Triangulum Galaxies -- II. Results from the Commissioning Observations and the Pilot Surveys
We present new quasars discovered in the vicinity of the Andromeda and
Triangulum galaxies with the LAMOST during the 2010 and 2011 observational
seasons. Quasar candidates are selected based on the available SDSS, KPNO 4 m
telescope, XSTPS optical, and WISE near infrared photometric data. We present
509 new quasars discovered in a stripe of ~135 sq. deg from M31 to M33 along
the Giant Stellar Stream in the 2011 pilot survey datasets, and also 17 new
quasars discovered in an area of ~100 sq. deg that covers the central region
and the southeastern halo of M31 in the 2010 commissioning datasets. These 526
new quasars have i magnitudes ranging from 15.5 to 20.0, redshifts from 0.1 to
3.2. They represent a significant increase of the number of identified quasars
in the vicinity of M31 and M33. There are now 26, 62 and 139 known quasars in
this region of the sky with i magnitudes brighter than 17.0, 17.5 and 18.0
respectively, of which 5, 20 and 75 are newly-discovered. These bright quasars
provide an invaluable collection with which to probe the kinematics and
chemistry of the ISM/IGM in the Local Group of galaxies. A total of 93 quasars
are now known with locations within 2.5 deg of M31, of which 73 are newly
discovered. Tens of quasars are now known to be located behind the Giant
Stellar Stream, and hundreds behind the extended halo and its associated
substructures of M31. The much enlarged sample of known quasars in the vicinity
of M31 and M33 can potentially be utilized to construct a perfect astrometric
reference frame to measure the minute PMs of M31 and M33, along with the PMs of
substructures associated with the Local Group of galaxies. Those PMs are some
of the most fundamental properties of the Local Group.Comment: 26 pages, 6 figures, AJ accepte
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Refining the accuracy of validated target identification through coding variant fine-mapping in type 2 diabetes.
We aggregated coding variant data for 81,412 type 2 diabetes cases and 370,832 controls of diverse ancestry, identifying 40 coding variant association signals (P < 2.2 × 10-7); of these, 16 map outside known risk-associated loci. We make two important observations. First, only five of these signals are driven by low-frequency variants: even for these, effect sizes are modest (odds ratio ≤1.29). Second, when we used large-scale genome-wide association data to fine-map the associated variants in their regional context, accounting for the global enrichment of complex trait associations in coding sequence, compelling evidence for coding variant causality was obtained for only 16 signals. At 13 others, the associated coding variants clearly represent 'false leads' with potential to generate erroneous mechanistic inference. Coding variant associations offer a direct route to biological insight for complex diseases and identification of validated therapeutic targets; however, appropriate mechanistic inference requires careful specification of their causal contribution to disease predisposition
Large-Scale Comparative Analyses of Tick Genomes Elucidate Their Genetic Diversity and Vector Capacities
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