42 research outputs found
Mitochondrial membrane lipidome defines yeast longevity
Our studies revealed that lithocholic acid (LCA), a bile acid, is a potent antiâaging natural compound that in yeast
cultured under longevityâextending caloric restriction (CR) conditions acts in synergy with CR to enable a significant further increase in chronological lifespan. Here, we investigate a mechanism underlying this robust longevityâextending effect of LCA under CR. We found that exogenously added LCA enters yeast cells, is sorted to mitochondria, resides mainly in the inner mitochondrial membrane, and also associates with the outer mitochondrial membrane. LCA elicits an ageârelated remodeling of glycerophospholipid synthesis and movement within both mitochondrial membranes, thereby causing substantial changes in mitochondrial membrane lipidome and triggering major changes in mitochondrial size, number and morphology. In synergy, these changes in the membrane lipidome and morphology of mitochondria alter the ageârelated chronology of mitochondrial respiration, membrane potential, ATP synthesis and reactive oxygen species homeostasis. The
LCAâdriven alterations in the ageârelated dynamics of these vital mitochondrial processes extend yeast longevity. In sum, our findings suggest a mechanism underlying the ability of LCA to delay chronological aging in yeast by accumulating in both mitochondrial membranes and altering their glycerophospholipid compositions. We concluded that mitochondrial membrane lipidome plays an essential role in defining yeast longevity
The Many Manifestations of Downsizing: Hierarchical Galaxy Formation Models confront Observations
[abridged] It has been widely claimed that several lines of observational
evidence point towards a "downsizing" (DS) of the process of galaxy formation
over cosmic time. This behavior is sometimes termed "anti-hierarchical", and
contrasted with the "bottom-up" assembly of the dark matter structures in Cold
Dark Matter models. In this paper we address three different kinds of
observational evidence that have been described as DS: the stellar mass
assembly, star formation rate and the ages of the stellar populations in local
galaxies. We compare a broad compilation of available data-sets with the
predictions of three different semi-analytic models of galaxy formation within
the Lambda-CDM framework. In the data, we see only weak evidence at best of DS
in stellar mass and in star formation rate. We find that, when observational
errors on stellar mass and SFR are taken into account, the models acceptably
reproduce the evolution of massive galaxies, over the entire redshift range
that we consider. However, lower mass galaxies are formed too early in the
models and are too passive at late times. Thus, the models do not correctly
reproduce the DS trend in stellar mass or the archaeological DS, while they
qualitatively reproduce the mass-dependent evolution of the SFR. We demonstrate
that these discrepancies are not solely due to a poor treatment of satellite
galaxies but are mainly connected to the excessively efficient formation of
central galaxies in high-redshift haloes with circular velocities ~100-200
km/s. [abridged]Comment: MNRAS accepted, 16 pages, 10 figure
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
DUALZ: Deep UNCOVER-ALMA Legacy High-Z Survey
We present the survey design and initial results of the ALMA Cycle 9 program
of DUALZ, which aims to establish a joint ALMA and JWST public legacy field
targeting the massive galaxy cluster Abell 2744. DUALZ features a contiguous
ALMA 30-GHz-wide mosaic in Band 6, covering areas of down
to a sensitivity of Jy. Through a blind search, we identified
69 dust continuum sources at S/N with median redshift and
intrinsic 1.2-mm flux of and ~mJy. Of
these, 27 have been spectroscopically confirmed, leveraged by the latest
NIRSpec observations, while photometric redshift estimates are constrained by
the comprehensive HST, NIRCam, and ALMA data for the remaining sources. With
priors, we further identify a [CII]158 m line emitter at
, confirmed by the latest NIRSpec spectroscopy. The NIRCam
counterparts of the 1.2-mm continuum exhibit undisturbed morphologies, denoted
either by disk or spheroid, implying the triggers for the faint mm emission are
less catastrophic than mergers. We have identified 8 HST-dark galaxies
(F150W27mag, F150WF444W2.3) and 2 JWST-dark (F444W30mag) galaxy
candidates among the ALMA continuum sources. The former includes face-on disk
galaxies, hinting that substantial dust obscuration does not always result from
inclination. We also detect a marginal dust emission from an X-ray-detected
galaxy at , suggesting an active co-evolution of the
central black hole and its host. We assess the infrared luminosity function up
to and find it consistent with predictions from galaxy formation
models. To foster diverse scientific outcomes from the community, we publicly
release reduced ALMA mosaic maps, cubes, and the source catalog.Comment: 33 pages, 16 figures, and 5 tables. Submitted to ApJS. The ALMA
products are fully available from here:
https://jwst-uncover.github.io/DR2.html#DUAL
The JWST UNCOVER Treasury survey: Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of Reionization
In this paper we describe the survey design for the Ultradeep NIRSpec and
NIRCam ObserVations before the Epoch of Reionization (UNCOVER) Cycle 1 JWST
Treasury program, which executed its early imaging component in November 2022.
The UNCOVER survey includes ultradeep () imaging of
45 arcmin on and around the well-studied Abell 2744 galaxy cluster at
and will follow-up galaxies with extremely deep
low-resolution spectroscopy with the NIRSpec/PRISM during the summer of 2023.
We describe the science goals, survey design, target selection, and planned
data releases. We also present and characterize the depths of the first NIRCam
imaging mosaic, highlighting previously unparalleled resolved and ultradeep 2-4
micron imaging of known objects in the field. The UNCOVER primary NIRCam mosaic
spans 28.8 arcmin in seven filters (F115W, F150W, F200W, F277W, F356W,
F410M, F444W) and 16.8 arcmin in our NIRISS parallel (F115W, F150W, F200W,
F356W, and F444W). To maximize early community use of the Treasury data set, we
publicly release full reduced mosaics of public JWST imaging including 45
arcmin NIRCam and 17 arcmin NIRISS mosaics on and around the Abell 2744
cluster, including the Hubble Frontier Field primary and parallel footprints.Comment: 17 pages, 8 figures, 4 tables, submitted to ApJ, comments welcome (v2
with full author list in metadata
The Physical Conditions of Emission-Line Galaxies at Cosmic Dawn from JWST/NIRSpec Spectroscopy in the SMACS 0723 Early Release Observations
We present rest-frame optical emission-line flux ratio measurements for five
galaxies observed by the JWST Near-Infared Spectrograph (NIRSpec) in the
SMACS 0723 Early Release Observations. We add several quality-control and
post-processing steps to the NIRSpec pipeline reduction products in order to
ensure reliable relative flux calibration of emission lines that are closely
separated in wavelength, despite the uncertain \textit{absolute}
spectrophotometry of the current version of the reductions. Compared to
galaxies in the literature, the galaxies have similar
[OIII]5008/H ratios, similar [OIII]4364/H
ratios, and higher (0.5 dex) [NeIII]3870/[OII]3728
ratios. We compare the observations to MAPPINGS V photoionization models and
find that the measured [NeIII]3870/[OII]3728,
[OIII]4364/H, and [OIII]5008/H emission-line
ratios are consistent with an interstellar medium that has very high ionization
(, units of cm~s), low metallicity (), and very high pressure (, units of
cm). The combination of [OIII]4364/H and
[OIII](4960+5008)/H line ratios indicate very high electron
temperatures of , further implying metallicities of
with the application of low-redshift calibrations for
``-based'' metallicities. These observations represent a tantalizing new
view of the physical conditions of the interstellar medium in galaxies at
cosmic dawn.Comment: Accepted for publication in AAS Journals. 14 pages, 6 figures, 3
table
CANDELS: The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey
The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS)
is designed to document the first third of galactic evolution, over the
approximate redshift (z) range 8--1.5. It will image >250,000 distant galaxies
using three separate cameras on the Hubble Space Telescope, from the
mid-ultraviolet to the near-infrared, and will find and measure Type Ia
supernovae at z>1.5 to test their accuracy as standardizable candles for
cosmology. Five premier multi-wavelength sky regions are selected, each with
extensive ancillary data. The use of five widely separated fields mitigates
cosmic variance and yields statistically robust and complete samples of
galaxies down to a stellar mass of 10^9 M_\odot to z \approx 2, reaching the
knee of the ultraviolet luminosity function (UVLF) of galaxies to z \approx 8.
The survey covers approximately 800 arcmin^2 and is divided into two parts. The
CANDELS/Deep survey (5\sigma\ point-source limit H=27.7 mag) covers \sim 125
arcmin^2 within GOODS-N and GOODS-S. The CANDELS/Wide survey includes GOODS and
three additional fields (EGS, COSMOS, and UDS) and covers the full area to a
5\sigma\ point-source limit of H \gtrsim 27.0 mag. Together with the Hubble
Ultra Deep Fields, the strategy creates a three-tiered "wedding cake" approach
that has proven efficient for extragalactic surveys. Data from the survey are
nonproprietary and are useful for a wide variety of science investigations. In
this paper, we describe the basic motivations for the survey, the CANDELS team
science goals and the resulting observational requirements, the field selection
and geometry, and the observing design. The Hubble data processing and products
are described in a companion paper.Comment: Submitted to Astrophysical Journal Supplement Series; Revised
version, subsequent to referee repor
Patterns of leisure-time physical activity participation in a British birth cohort at early old age.
Using data from a nationally representative British birth cohort we characterized the type and diversity of leisure-time physical activity that 2,188 participants (age 60â64 years) engaged in throughout the year by gender and obesity. Participants most commonly reported walking (71%), swimming (33%), floor exercises (24%) and cycling (15%). Sixty-two percent of participants reported $2 activities in the past year and 40% reported diversity on a regular basis. Regular engagement in different types of activity (cardio-respiratory, balance/flexibility and strength) was reported by 67%, 19% and 11% of participants, respectively. We found gender differences, as well as differences by obesity status, in the activities reported, the levels of activity diversity and activity type. Non-obese participants had greater activity diversity, and more often reported activities beneficial for cardio-respiratory health and balance/flexibility than obese participants. These findings may be used to inform the development of trials of physical activity interventions targeting older adults, and those older adults with high body mass index
Childhood socioeconomic position and adult leisure-time physical activity: A systematic review
Regular leisure-time physical activity (LTPA) benefits health and is thought to be less prevalent in lower socioeconomic groups. Evidence suggests that childhood socioeconomic circumstances can impact on adult health and behaviour however, it is unclear if this includes an influence on adult LTPA. This review tested the hypothesis that a lower childhood socioeconomic position (SEP) is associated with less frequent LTPA during adulthood. Studies were located through a systematic search of MEDLINE, Embase, PsycINFO, CINAHL and SPORTDiscus and by searching reference lists. Eligible studies were English-language publications testing the association between any indicator of childhood SEP and an LTPA outcome measured during adulthood. Forty-five papers from 36 studies, most of which were European, were included. In most samples, childhood SEP and LTPA were self-reported in midlife. Twenty-two studies found evidence to support the reviewâs hypothesis and thirteen studies found no association. Accounting for own adult SEP partly attenuated associations. There was more evidence of an association in British compared with Scandinavian cohorts and in women compared with men. Results did not vary by childhood SEP indicator or age at assessment of LTPA. This review found evidence of an association between less advantaged childhood SEP and less frequent LTPA during adulthood. Understanding how associations vary by gender and place could provide insights into underlying pathways