165 research outputs found
A COMPARISON OF THE PERFECT PUSH-UPâą TO TRADITIONAL PUSH-UP
The push-up has traditionally been used to help improve arm and shoulder girdle strength and endurance (ASGSE) (Baumgartner, Oh, Chung, and Hales, 2002). The Perfect Push-Upâą was designed to help improve the work-out that could be obtained while performing push-ups. While the claims from the manufacturer seem appealing there is little to no research to support their claims. The purpose of the current study is to examine the muscle activity and arm kinematics while using the Perfect Push-Upâą compared to traditional push-ups, thus addressing the claims of an improved work-out
A dark siren measurement of the Hubble constant with the LIGO/Virgo gravitational wave event GW190412 and DESI galaxies
We present a measurement of the Hubble Constant using the gravitational
wave event GW190412, an asymmetric binary black hole merger detected by
LIGO/Virgo, as a dark standard siren. This event does not have an
electromagnetic counterpart, so we use the statistical standard siren method
and marginalize over potential host galaxies from the Dark Energy Spectroscopic
Instrument (DESI) survey. GW190412 is well-localized to 12 deg (90%
credible interval), so it is promising for a dark siren analysis. The dark
siren value for km/s/Mpc, with a posterior shape
that is consistent with redshift overdensities. When combined with the bright
standard siren measurement from GW170817 we recover
km/s/Mpc, consistent with both early and late-time Universe measurements of
. This work represents the first standard siren analysis performed with
DESI data, and includes the most complete spectroscopic sample used in a dark
siren analysis to date.Comment: Submitted to RNAA
Synthetic light-cone catalogues of modern redshift and weak lensing surveys waith abacussummit
The joint analysis of different cosmological probes, such as galaxy clustering and weak lensing, can potentially yield invaluable insights into the nature of the primordial Universe, dark energy, and dark matter. However, the development of high-fidelity theoretical models is a necessary stepping stone. Here, we present public high-resolution weak lensing maps on the light-cone, generated using the N-body simulation suite abacussummit, and accompanying weak lensing mock catalogues, tuned to the Early Data Release small-scale clustering measurements of the Dark Energy Spectroscopic Instrument. Available in this release are maps of the cosmic shear, deflection angle, and convergence fields at source redshifts ranging from z = 0.15 to 2.45 as well as cosmic microwave background convergence maps for each of the 25 base-resolution simulations (and Npart = 69123) as well as for the two huge simulations (and Npart = 86403) at the fiducial abacussummit cosmology. The pixel resolution of each map is 0.21 arcmin, corresponding to a healpix Nside of 16 384. The sky coverage of the base simulations is an octant until z â 0.8 (decreasing to about 1800 deg2 at z â 2.4), whereas the huge simulations offer full-sky coverage until z â 2.2. Mock lensing source catalogues are sampled matching the ensemble properties of the Kilo-Degree Survey, Dark Energy Survey, and Hyper Suprime-Cam data sets. The mock catalogues are validated against theoretical predictions for various clustering and lensing statistics, such as correlation multipoles, galaxy-shear, and shear-shear, showing excellent agreement. All products can be downloaded via a Globus endpoint (see Data Availability section)
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
Validation of semi-analytical, semi-empirical covariance matrices for two-point correlation function for early DESI data
We present an extended validation of semi-analytical, semi-empirical covariance matrices for the two-point correlation function (2PCF) on simulated catalogs representative of luminous red galaxies (LRGs) data collected during the initial 2 months of operations of the Stage-IV ground-based Dark Energy Spectroscopic Instrument (DESI). We run the pipeline on multiple effective Zel'dovich (EZ) mock galaxy catalogs with the corresponding cuts applied and compare the results with the mock sample covariance to assess the accuracy and its fluctuations. We propose an extension of the previously developed formalism for catalogs processed with standard reconstruction algorithms. We consider methods for comparing covariance matrices in detail, highlighting their interpretation and statistical properties caused by sample variance, in particular, non-trivial expectation values of certain metrics even when the external covariance estimate is perfect. With improved mocks and validation techniques, we confirm a good agreement between our predictions and sample covariance. This allows one to generate covariance matrices for comparable data sets without the need to create numerous mock galaxy catalogs with matching clustering, only requiring 2PCF measurements from the data itself. The code used in this paper is publicly available at https://github.com/oliverphilcox/RascalC
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
Mock data sets for the Eboss and DESI Lyman- forest surveys
{We present a publicly-available code to generate mock Lyman- (\lya)
forest data sets. The code is based on the Fluctuating Gunn-Peterson
Approximation (FGPA) applied to Gaussian random fields and on the use of fast
Fourier transforms (FFT). The output includes spectra of lya transmitted flux
fraction, , a quasar catalog, and a catalog of high-column-density systems.
While these three elements have realistic correlations, additional code is then
used to generate realistic quasar spectra, to add absorption by
high-column-density systems and metals, and to simulate instrumental effects.
Redshift space distortions (RSD) are implemented by including the large-scale
velocity-gradient field in the FGPA resulting in a correlation function of
that can be accurately predicted. One hundred realizations have been produced
over the 14,000 deg Dark Energy Spectroscopy Instrument (DESI) survey
footprint with 100 quasars per deg, and they are being used for the
Extended Baryon Oscillation Survey (eBOSS) and DESI surveys. The analysis of
these realizations shows that the correlation of follows the prediction
within the accuracy of eBOSS survey. The most time-consuming part of the
production occurs before application of the FGPA, and the existing pre-FGPA
forests can be used to easily produce new mock sets with modified
redshift-dependent bias parameters or observational conditions.Comment: to be submitted ot JCA
The DESI One-Percent Survey: Constructing Galaxy-Halo Connections for ELGs and LRGs Using Auto and Cross Correlations
In the current Dark Energy Spectroscopic Instrument (DESI) survey, emission line galaxies (ELGs) and luminous red galaxies (LRGs) are essential for mapping the dark matter distribution at N M . We measure the auto and cross correlation functions of ELGs and LRGs at 108.0 M â from the DESI One-Percent survey. Following Gao et al., we construct the galaxy-halo connections for ELGs and LRGs simultaneously. With the stellar-halo mass relation for the whole galaxy population (i.e., normal galaxies), LRGs can be selected directly by stellar mass, while ELGs can also be selected randomly based on the observed number density of each stellar mass, once the probability z ⌠0.2 of a satellite galaxy becoming an ELG is determined. We demonstrate that the observed small scale clustering prefers a halo mass-dependent z ⌠0.2 model rather than a constant. With this model, we can well reproduce the auto correlations of LRGs and the cross correlations between LRGs and ELGs at z ⌠0.7 z ⌠1. We can also reproduce the auto correlations of ELGs at deg2 z ⌠1 (0.6 < z < 1.6 z ⌠1) in real (redshift) space. Although our model has only seven parameters, we show that it can be extended to higher redshifts and reproduces the observed auto correlations of ELGs in the whole range of âŒ1012 M â, which enables us to generate a lightcone ELG mock for DESI. With the above model, we further derive halo occupation distributions for ELGs, which can be used to produce ELG mocks in coarse simulations without resolving subhalos
A Large Sample of Extremely Metal-poor Galaxies at Identified from the DESI Early Data
Extremely metal-poor galaxies (XMPGs) at relatively low redshift are
excellent laboratories for studying galaxy formation and evolution in the early
universe. Much effort has been spent on identifying them from large-scale
spectroscopic surveys or spectroscopic follow-up observations. Previous work
has identified a few hundred XMPGs. In this work, we obtain a large sample of
223 XMPGs at from the early data of the Dark Energy Spectroscopic
Instrument (DESI). The oxygen abundance is determined using the direct method based on the detection of the [O III]4363 line. The sample
includes 95 confirmed XMPGs based on the oxygen abundance uncertainty;
remaining 128 galaxies are regarded as XMPG candidates. These XMPGs are only
0.01% of the total DESI observed galaxies. Their coordinates and other
proprieties are provided in the paper. The most XMPG has an oxygen abundance of
, stellar mass of about and star
formation rate of 0.22 yr. The two most XMPGs present
distinct morphologies suggesting different formation mechanisms. The local
environmental investigation shows that XMPGs preferentially reside in
relatively low-density regions. Many of them fall below the stellar
mass-metallicity relations (MZRs) of normal star-forming galaxies. From a
comparison of the MZR with theoretical simulations, it appears that XMPGs are
good analogs to high-redshift star-forming galaxies. The nature of these XMPG
populations will be further investigated in detail with larger and more
complete samples from the on-going DESI survey.Comment: accepted for publication in Ap
The DESI One-Percent Survey: Modelling the clustering and halo occupation of all four DESI tracers with Uchuu
We present results from a set of high-fidelity simulated lightcones for the
DESI One-Percent Survey, created from the Uchuu simulation. This 8 (Gpc/h)^3
N-body simulation comprises 2.1 trillion particles and provides high-resolution
dark matter (sub)haloes in the framework of the Planck base-LCDM cosmology.
Employing the subhalo abundance matching (SHAM) technique, we populate the
Uchuu (sub)haloes with all four DESI tracers (BGS, LRG, ELG and QSO) to z =
2.1. Our method accounts for redshift evolution as well as the clustering
dependence on luminosity and stellar mass. The two-point clustering statistics
of the DESI One-Percent Survey align reasonably well with our predictions from
Uchuu across scales ranging from 0.1 Mpc/h to 100 Mpc/h. Some discrepancies
arise due to cosmic variance, incompleteness in the massive end of the stellar
mass function, and a simplified galaxy-halo connection model. We find that the
Uchuu BGS and LRG samples are adequately described using the standard
5-parameter halo occupation distribution model, while the ELGs and QSOs show
agreement with an adopted Gaussian distribution for central halos with a power
law for satellites. We observe a fair agreement in the large-scale bias
measurements between data and mock samples, although the data exhibits smaller
bias values, likely due to cosmic variance. The bias dependence on absolute
magnitude, stellar mass and redshift aligns with that of previous surveys.
These results improve simulated lightcone construction from cosmological models
and enhance our understanding of the galaxy-halo connection, with pivotal
insights from the first DESI data for the success of the final survey.Comment: 23 pages, 15 figures, 5 tables, submitted to MNRAS. The Uchuu-DESI
lightcones will be available at https://data.desi.lbl.go
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