209 research outputs found
A sociodemographic and neuropsychological characterization of an illiterate population
The objectives of this article are to characterize the performance and to discuss the performance differences between literate and illiterate participants in a well-defined study population. We describe the participant-selection procedure used to investigate this population. Three groups with similar sociocultural backgrounds living in a relatively homogeneous fishing community in southern Portugal were characterized in terms of socioeconomic and sociocultural background variables and compared on a simple neuropsychological test battery; specifically, a literate group with more than 4 years of education (n = 9), a literate group with 4 years of education (n = 26), and an illiterate group (n = 31) were included in this study. We compare and discuss our results with other similar studies on the effects of literacy and illiteracy. The results indicate that naming and identification of real objects, verbal fluency using ecologically relevant semantic criteria, verbal memory, and orientation are not affected by literacy or level of formal education. In contrast, verbal working memory assessed with digit span, verbal abstraction, long-term semantic memory, and calculation (i.e., multiplication) are significantly affected by the level of literacy. We indicate that it is possible, with proper participant-selection procedures, to exclude general cognitive impairment and to control important sociocultural factors that potentially could introduce bias when studying the specific effects of literacy and level of formal education on cognitive brain function
Gravitational Waves From Known Pulsars: Results From The Initial Detector Era
We present the results of searches for gravitational waves from a large selection of pulsars using data from the most recent science runs (S6, VSR2 and VSR4) of the initial generation of interferometric gravitational wave detectors LIGO (Laser Interferometric Gravitational-wave Observatory) and Virgo. We do not see evidence for gravitational wave emission from any of the targeted sources but produce upper limits on the emission amplitude. We highlight the results from seven young pulsars with large spin-down luminosities. We reach within a factor of five of the canonical spin-down limit for all seven of these, whilst for the Crab and Vela pulsars we further surpass their spin-down limits. We present new or updated limits for 172 other pulsars (including both young and millisecond pulsars). Now that the detectors are undergoing major upgrades, and, for completeness, we bring together all of the most up-to-date results from all pulsars searched for during the operations of the first-generation LIGO, Virgo and GEO600 detectors. This gives a total of 195 pulsars including the most recent results described in this paper.United States National Science FoundationScience and Technology Facilities Council of the United KingdomMax-Planck-SocietyState of Niedersachsen/GermanyAustralian Research CouncilInternational Science Linkages program of the Commonwealth of AustraliaCouncil of Scientific and Industrial Research of IndiaIstituto Nazionale di Fisica Nucleare of ItalySpanish Ministerio de Economia y CompetitividadConselleria d'Economia Hisenda i Innovacio of the Govern de les Illes BalearsNetherlands Organisation for Scientific ResearchPolish Ministry of Science and Higher EducationFOCUS Programme of Foundation for Polish ScienceRoyal SocietyScottish Funding CouncilScottish Universities Physics AllianceNational Aeronautics and Space AdministrationOTKA of HungaryLyon Institute of Origins (LIO)National Research Foundation of KoreaIndustry CanadaProvince of Ontario through the Ministry of Economic Development and InnovationNational Science and Engineering Research Council CanadaCarnegie TrustLeverhulme TrustDavid and Lucile Packard FoundationResearch CorporationAlfred P. Sloan FoundationAstronom
DESI Survey Validation Spectra Reveal an Increasing Fraction of Recently Quenched Galaxies at
We utilize bright Luminous Red Galaxies (LRGs) from the novel
Dark Energy Spectroscopic Instrument Survey Validation spectroscopic sample,
leveraging its deep ( hour/galaxy exposure time) spectra to
characterize the contribution of recently quenched galaxies to the massive
galaxy population at . We use Prospector to infer non-parametric
star formation histories and identify a significant population of
post-starburst galaxies that have joined the quiescent population within the
past Gyr. The highest redshift subset (277 at ) of our sample of
recently quenched galaxies represents the largest spectroscopic sample of
post-starburst galaxies at that epoch. At , we measure the number
density of quiescent LRGs, finding that recently quenched galaxies constitute a
growing fraction of the massive galaxy population with increasing lookback
time. Finally, we quantify the importance of this population amongst massive
() LRGs by measuring the fraction of
stellar mass each galaxy formed in the Gyr before observation, . Although galaxies with are rare at
( of the population), by they constitute
of massive galaxies. Relaxing this threshold, we find that galaxies with
constitute of the massive galaxy population
at . We also identify a small but significant sample of galaxies at
that formed with , implying that they may
be analogues to high-redshift quiescent galaxies that formed on similar
timescales. Future analysis of this unprecedented sample promises to illuminate
the physical mechanisms that drive the quenching of massive galaxies after
cosmic noon.Comment: Submitted to ApJ Letters after DESI Collaboration Review. 14 pages, 5
figures, comments welcome
Changing-look Active Galactic Nuclei from the Dark Energy Spectroscopic Instrument. I. Sample from the Early Data
\ua9 2024. The Author(s). Published by the American Astronomical Society.Changing-look active galactic nuclei (CL AGNs) can be generally confirmed by the emergence (turn-on) or disappearance (turn-off) of broad emission lines (BELs), associated with a transient timescale (about 100 ⌠5000 days) that is much shorter than predicted by traditional accretion disk models. We carry out a systematic CL AGN search by crossmatching the spectra coming from the Dark Energy Spectroscopic Instrument and the Sloan Digital Sky Survey. Following previous studies, we identify CL AGNs based on Hα, HÎČ, and Mg ii at z †0.75 and Mg ii, C iii], and C iv at z > 0.75. We present 56 CL AGNs based on visual inspection and three selection criteria, including 2 Hα, 34 HÎČ, 9 Mg ii, 18 C iii], and 1 C iv CL AGN. Eight cases show simultaneous appearances/disappearances of two BELs. We also present 44 CL AGN candidates with significant flux variation of BELs, but remaining strong broad components. In the confirmed CL AGNs, 10 cases show additional CL candidate features for different lines. In this paper, we find: (1) a 24:32 ratio of turn-on to turn-off CL AGNs; (2) an upper-limit transition timescale ranging from 330 to 5762 days in the rest frame; and (3) the majority of CL AGNs follow the bluer-when-brighter trend. Our results greatly increase the current CL census (âŒ30%) and would be conducive to exploring the underlying physical mechanism
PROVABGS: The Probabilistic Stellar Mass Function of the BGS One-Percent Survey
We present the probabilistic stellar mass function (pSMF) of galaxies in the
DESI Bright Galaxy Survey (BGS), observed during the One-Percent Survey. The
One-Percent Survey was one of DESI's survey validation programs conducted from
April to May 2021, before the start of the main survey. It used the same target
selection and similar observing strategy as the main survey and successfully
observed the spectra and redshifts of 143,017 galaxies in the
magnitude-limited BGS Bright sample and 95,499 galaxies in the fainter surface
brightness and color selected BGS Faint sample over . We derive pSMFs
from posteriors of stellar mass, , inferred from DESI photometry and
spectroscopy using the Hahn et al. (2022a; arXiv:2202.01809) PRObabilistic
Value-Added BGS (PROVABGS) Bayesian SED modeling framework. We use a
hierarchical population inference framework that statistically and rigorously
propagates the uncertainties. Furthermore, we include correction weights
that account for the selection effects and incompleteness of the BGS
observations. We present the redshift evolution of the pSMF in BGS as well as
the pSMFs of star-forming and quiescent galaxies classified using average
specific star formation rates from PROVABGS. Overall, the pSMFs show good
agreement with previous stellar mass function measurements in the literature.
Our pSMFs showcase the potential and statistical power of BGS, which in its
main survey will observe >100 more galaxies. Moreover, we present the
statistical framework for subsequent population statistics measurements using
BGS, which will characterize the global galaxy population and scaling relations
at low redshifts with unprecedented precision.Comment: 25 pages, 12 figures; data used to generate figures is available at
https://doi.org/10.5281/zenodo.8018936; submitted to Ap
PROVABGS: The Probabilistic Stellar Mass Function of the BGS One-percent Survey
We present the probabilistic stellar mass function (pSMF) of galaxies in the DESI Bright Galaxy Survey (BGS), observed during the One-percent Survey. The One-percent Survey was one of DESIâs survey validation programs conducted from 2021 April to May, before the start of the main survey. It used the same target selection and similar observing strategy as the main survey and successfully observed the spectra and redshifts of 143,017 galaxies in the r 100 Ă more galaxies. Moreover, we present the statistical framework for subsequent population statistics measurements using BGS, which will characterize the global galaxy population and scaling relations at low redshifts with unprecedented precision
The frequency of metal enrichment of cool helium-atmosphere white dwarfs using the DESI early data release
There is an overwhelming evidence that white dwarfs host planetary systems; revealed by the presence, disruption, and accretion of planetary bodies. A lower limit on the frequency of white dwarfs that host planetary material has been estimated to be ââ25â50 perâcent; inferred from the ongoing or recent accretion of metals on to both hydrogen-atmosphere and warm helium-atmosphere white dwarfs. Now with the unbiased sample of white dwarfs observed by the Dark Energy Spectroscopic Instrument (DESI) survey in their Early Data Release (EDR), we have determined the frequency of metal enrichment around cool-helium atmosphere white dwarfs as 21 ± 3 perâcent using a sample of 234 systems. This value is in good agreement with values determined from previous studies. With the current samples we cannot distinguish whether the frequency of planetary accretion varies with system age or host-star mass, but the DESI data release 1 will contain roughly an order of magnitude more white dwarfs than DESI EDR and will allow these parameters to be investigated
Mitigating the noise of DESI mocks using analytic control variates
In order to address fundamental questions related to the expansion history of
the Universe and its primordial nature with the next generation of galaxy
experiments, we need to model reliably large-scale structure observables such
as the correlation function and the power spectrum. Cosmological -body
simulations provide a reference through which we can test our models, but their
output suffers from sample variance on large scales. Fortunately, this is the
regime where accurate analytic approximations exist. To reduce the variance,
which is key to making optimal use of these simulations, we can leverage the
accuracy and precision of such analytic descriptions using Control Variates
(CV). We apply two control variate formulations to mock catalogs generated in
anticipation of upcoming data from the Dark Energy Spectroscopic Instrument
(DESI) to test the robustness of its analysis pipeline. Our CV-reduced
measurements, of the power spectrum and correlation function, both pre- and
post-reconstruction, offer a factor of 5-10 improvement in the measurement
error compared with the raw measurements from the DESI mock catalogs. We
explore the relevant properties of the galaxy samples that dictate this
reduction and comment on the improvements we find on some of the derived
quantities relevant to Baryon Acoustic Oscillation (BAO) analysis. We also
provide an optimized package for computing the power spectra and other
two-point statistics of an arbitrary galaxy catalog as well as a pipeline for
obtaining CV-reduced measurements on any of the AbacusSummit cubic box outputs.
We make our scripts, notebooks, and benchmark tests against existing software
publicly available and report a speed improvement of a factor of 10 for a
grid size of compared with .Comment: 15 pages, 9 figures, public package (for power spectrum and control
variates estimation
A striking relationship between dust extinction and radio detection in DESI QSOs: evidence for a dusty blow-out phase in red QSOs
We present the first eight months of data from our secondary target programme within the ongoing Dark Energy Spectroscopic Instrument (DESI) survey. Our programme uses a mid-infrared and optical colour selection to preferentially target dust-reddened quasi-stellar objects (QSOs) that would have otherwise been missed by the nominal DESI QSO selection. So far, we have obtained optical spectra for 3038 candidates, of which âŒ70 per cent of the high-quality objects (those with robust redshifts) are visually confirmed to be Type 1 QSOs, consistent with the expected fraction from the main DESI QSO survey. By fitting a dust-reddened blue QSO composite to the QSO spectra, we find they are well-fitted by a normal QSO with up to AV âŒ4 mag of line-of-sight dust extinction. Utilizing radio data from the LOFAR Two-metre Sky Survey (LoTSS) DR2, we identify a striking positive relationship between the amount of line-of-sight dust extinction towards a QSO and the radio detection fraction, that is not driven by radio-loud systems, redshift and/or luminosity effects. This demonstrates an intrinsic connection between dust reddening and the production of radio emission in QSOs, whereby the radio emission is most likely due to low-powered jets or winds/outflows causing shocks in a dusty environment. On the basis of this evidence, we suggest that red QSOs may represent a transitional 'blow-out' phase in the evolution of QSOs, where winds and outflows evacuate the dust and gas to reveal an unobscured blue QSO
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