825 research outputs found
z~2: An Epoch of Disk Assembly
We explore the evolution of the internal gas kinematics of star-forming
galaxies from the peak of cosmic star-formation at to today.
Measurements of galaxy rotation velocity , which quantify ordered
motions, and gas velocity dispersion , which quantify disordered
motions, are adopted from the DEEP2 and SIGMA surveys. This sample covers a
continuous baseline in redshift from to , spanning 10 Gyrs. At
low redshift, nearly all sufficiently massive star-forming galaxies are
rotationally supported (). By , the percentage of
galaxies with rotational support has declined to 50 at low stellar mass
() and 70 at high stellar mass
(). For , the percentage
drops below 35 for all masses. From to now, galaxies exhibit
remarkably smooth kinematic evolution on average. All galaxies tend towards
rotational support with time, and it is reached earlier in higher mass systems.
This is mostly due to an average decline in by a factor of 3 since a
redshift of 2, which is independent of mass. Over the same time period,
increases by a factor of 1.5 for low mass systems, but does not
evolve for high mass systems. These trends in and with
time are at a fixed stellar mass and should not be interpreted as evolutionary
tracks for galaxy populations. When galaxy populations are linked in time with
abundance matching, not only does decline with time as before, but
strongly increases with time for all galaxy masses. This enhances the
evolution in . These results indicate that is a
period of disk assembly, during which the strong rotational support present in
today's massive disk galaxies is only just beginning to emerge.Comment: 12 pages, 8 figures, submitted to Ap
Interactions between environmental contaminants and gastrointestinal parasites: novel insights from an integrative approach in a marine predator
Environmental contaminants and parasites are ubiquitous stressors that can affect animal physiology and derive from similar dietary sources (co-exposure). To unravel their interactions in wildlife, it is thus essential to quantify their concurring drivers. Here, the relationship between blood contaminant residues (11 trace elements and 17 perfluoroalkyl substances) and nonlethally quantified gastrointestinal parasite loads was tested while accounting for intrinsic (sex, age, and mass) and extrinsic factors (trophic ecology inferred from stable isotope analyses and biologging) in European shags Phalacrocorax aristotelis. Shags had high mercury (range 0.65–3.21 μg g–1 wet weight, ww) and extremely high perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) residues (3.46–53 and 4.48–44 ng g–1 ww, respectively). Males had higher concentrations of arsenic, mercury, PFOA, and PFNA than females, while the opposite was true for selenium, perfluorododecanoic acid (PFDoA), and perfluooctane sulfonic acid (PFOS). Individual parasite loads (Contracaecum rudolphii) were higher in males than in females. Females targeted pelagic-feeding prey, while males relied on both pelagic- and benthic-feeding organisms. Parasite loads were not related to trophic ecology in either sex, suggesting no substantial dietary co-exposure with contaminants. In females, parasite loads increased strongly with decreasing selenium:mercury molar ratios. Females may be more susceptible to the interactive effects of contaminants and parasites on physiology, with potential fitness consequences
Investigating the Effect of Galaxy Interactions on Star Formation at 0.5<z<3.0
Observations and simulations of interacting galaxies and mergers in the local
universe have shown that interactions can significantly enhance the star
formation rates (SFR) and fueling of Active Galactic Nuclei (AGN). However, at
higher redshift, some simulations suggest that the level of star formation
enhancement induced by interactions is lower due to the higher gas fractions
and already increased SFRs in these galaxies. To test this, we measure the SFR
enhancement in a total of 2351 (1327) massive () major
() spectroscopic galaxy pairs at 0.5<z<3.0 with
km s (1000 km s) and projected separation <150 kpc selected from
the extensive spectroscopic coverage in the COSMOS and CANDELS fields. We find
that the highest level of SFR enhancement is a factor of 1.23
in the closest projected separation bin (<25 kpc) relative to a stellar mass-,
redshift-, and environment-matched control sample of isolated galaxies. We find
that the level of SFR enhancement is a factor of higher at 0.5<z<1
than at 1<z<3 in the closest projected separation bin. Among a sample of
visually identified mergers, we find an enhancement of a factor of
1.86 for coalesced systems. For this visually identified
sample, we see a clear trend of increased SFR enhancement with decreasing
projected separation (2.40 vs.\ 1.58 for
0.5<z<1.6 and 1.6<z<3.0, respectively). The SFR enhancement seen in our
interactions and mergers are all lower than the level seen in local samples at
the same separation, suggesting that the level of interaction-induced star
formation evolves significantly over this time period.Comment: 23 pages, 13 figures, Accepted for publication in Ap
Extremely Red Galaxies at z = 5-9 with MIRI and NIRSpec:Dusty Galaxies or Obscured Active Galactic Nuclei?
We study a new population of extremely red objects (EROs) recently discovered by the James Webb Space Telescope (JWST) based on their NIRCam colors F277W − F444W > 1.5 mag. We find 37 EROs in the Cosmic Evolution Early Release Science Survey (CEERS) field with F444W < 28 mag and photometric redshifts between 5 < z < 7, with median z = 6.9 − 1.6 + 1.0 . Surprisingly, despite their red long-wavelength colors, these EROs have blue short-wavelength colors (F150W − F200W ∼ 0 mag) indicative of bimodal spectral energy distributions (SEDs) with a red, steep slope in the rest-frame optical, and a blue, flat slope in the rest-frame UV. Moreover, all these EROs are unresolved, point-like sources in all NIRCam bands. We analyze the SEDs of eight of them with MIRI and NIRSpec observations using stellar population models and active galactic nucleus (AGN) templates. We find that dusty galaxies or obscured AGNs provide similarly good SED fits but different stellar properties: massive and dusty, log M ⋆ / M ⊙ ∼ 10 and A V ≳ 3 mag, or low mass and obscured, log M ⋆ / M ⊙ ∼ 7.5 and A V ∼ 0 mag, hosting an obscured quasi-stellar object (QSO). SED modeling does not favor either scenario, but their unresolved sizes are more suggestive of AGNs. If any EROs are confirmed to have log M ⋆ / M ⊙ ≳ 10.5, it would increase the pre-JWST number density at z > 7 by up to a factor ∼60. Similarly, if they are QSOs with luminosities in the L bol > 1045-46 erg s−1 range, their number would exceed that of bright blue QSOs by more than three orders of magnitude. Additional photometry at mid-infrared wavelengths will reveal the true nature of the red continuum emission in these EROs and will place this puzzling population in the right context of galaxy evolution.</p
First Look at z > 1 Bars in the Rest-Frame Near-Infrared with JWST Early CEERS Imaging
Stellar bars are key drivers of secular evolution in galaxies and can be
effectively studied using rest-frame near-infrared (NIR) images, which trace
the underlying stellar mass and are less impacted by dust and star formation
than rest-frame UV or optical images. We leverage the power of {\it{JWST}}
CEERS NIRCam images to present the first quantitative identification and
characterization of stellar bars at based on rest-frame NIR F444W images
of high resolution (~1.3 kpc at z ~ 1-3). We identify stellar bars in these
images using quantitative criteria based on ellipse fits. For this pilot study,
we present six examples of robustly identified bars at with spectroscopic
redshifts, including the two highest redshift bars at ~2.136 and 2.312
quantitatively identified and characterized to date. The stellar bars at ~
1.1-2.3 presented in our study have projected semi-major axes of ~2.9-4.3 kpc
and projected ellipticities of ~0.41-0.53 in the rest-frame NIR. The barred
host galaxies have stellar masses ~ to
, star formation rates of ~ 21-295 yr, and
several have potential nearby companions. Our finding of bars at ~1.1-2.3
demonstrates the early onset of such instabilities and supports simulations
where bars form early in massive dynamically cold disks. It also suggests that
if these bars at lookback times of 8-10 Gyr survive out to present epochs,
bar-driven secular processes may operate over a long time and have a
significant impact on some galaxies by z ~ 0.Comment: 16 pages, 5 figures. Accepted for Publication in Astrophysical
Journal Letter
CEERS: Diversity of Lyman-Alpha Emitters during the Epoch of Reionization
We analyze rest-frame ultraviolet to optical spectra of three -
galaxies whose Ly-emission lines were previously detected with
Keck/MOSFIRE observations, using the JWST/NIRSpec observations from the Cosmic
Evolution Early Release Science (CEERS) survey. From NIRSpec data, we confirm
the systemic redshifts of these Ly emitters, and emission-line ratio
diagnostics indicate these galaxies were highly ionized and metal poor. We
investigate Ly line properties, including the line flux, velocity
offset, and spatial extension. For the one galaxy where we have both NIRSpec
and MOSFIRE measurements, we find a significant offset in their flux
measurements ( greater in MOSFIRE) and a marginal difference in
the velocity shifts. The simplest interpretation is that the Ly
emission is extended and not entirely encompassed by the NIRSpec slit. The
cross-dispersion profiles in NIRSpec reveal that Ly in one galaxy is
significantly more extended than the non-resonant emission lines. We also
compute the expected sizes of ionized bubbles that can be generated by the
Ly sources, discussing viable scenarios for the creation of sizable
ionized bubbles (1 physical Mpc). The source with the highest-ionization
condition is possibly capable of ionizing its own bubble, while the other two
do not appear to be capable of ionizing such a large region, requiring
additional sources of ionizing photons. Therefore, the fact that we detect
Ly from these galaxies suggests diverse scenarios on escape of
Ly during the epoch of reionization. High spectral resolution spectra
with JWST/NIRSpec will be extremely useful for constraining the physics of
patchy reionization.Comment: Submitted to ApJ (18 pages, 7 figures, 2 tables
First Look at z > 1 Bars in the Rest-frame Near-infrared with JWST Early CEERS Imaging
Stellar bars are key drivers of secular evolution in galaxies and can be effectively studied using rest-frame near-infrared (NIR) images, which trace the underlying stellar mass and are less impacted by dust and star formation than rest-frame UV or optical images. We leverage the power of JWST CEERS NIRCam images to present the first quantitative identification and characterization of stellar bars at z > 1 based on rest-frame NIR F444W images of high resolution (∼1.3 kpc at z ∼ 1-3). We identify stellar bars in these images using quantitative criteria based on ellipse fits. For this pilot study, we present six examples of robustly identified bars at z > 1 with spectroscopic redshifts, including the two highest-redshift bars at z ∼ 2.136 and 2.312 quantitatively identified and characterized to date. The stellar bars at z ∼ 1.1-2.3 presented in our study have projected semimajor axes of ∼2.9-4.3 kpc and projected ellipticities of ∼0.41-0.53 in the rest-frame NIR. The barred host galaxies have stellar masses ∼1 × 10 10 to 2 × 10 11 M ⊙ and star formation rates of ∼21-295 M ⊙ yr −1, and several have potential nearby companions. Our finding of bars at z ∼ 1.1-2.3 demonstrates the early onset of such instabilities and supports simulations where bars form early in massive dynamically cold disks. It also suggests that if these bars at lookback times of 8-11 Gyr survive out to present epochs, bar-driven secular processes may operate over a long time and have a significant impact on some galaxies by z ∼ 0.</p
Evidence for a Shallow Evolution in the Volume Densities of Massive Galaxies at to from CEERS
We analyze the evolution of massive (log [] )
galaxies at 4--8 selected from the JWST Cosmic Evolution Early Release
Science (CEERS) survey. We infer the physical properties of all galaxies in the
CEERS NIRCam imaging through spectral energy distribution (SED) fitting with
dense basis to select a sample of high redshift massive galaxies. Where
available we include constraints from additional CEERS observing modes,
including 18 sources with MIRI photometric coverage, and 28 sources with
spectroscopic confirmations from NIRSpec or NIRCam wide-field slitless
spectroscopy. We sample the recovered posteriors in stellar mass from SED
fitting to infer the volume densities of massive galaxies across cosmic time,
taking into consideration the potential for sample contamination by active
galactic nuclei (AGN). We find that the evolving abundance of massive galaxies
tracks expectations based on a constant baryon conversion efficiency in dark
matter halos for 1--4. At higher redshifts, we observe an excess
abundance of massive galaxies relative to this simple model. These higher
abundances can be explained by modest changes to star formation physics and/or
the efficiencies with which star formation occurs in massive dark matter halos,
and are not in tension with modern cosmology.Comment: 20 pages, 10 figure
The past, present, and future of the brain imaging data structure (BIDS)
The Brain Imaging Data Structure (BIDS) is a community-driven standard for the organization of data and metadata from a growing range of neuroscience modalities. This paper is meant as a history of how the standard has developed and grown over time. We outline the principles behind the project, the mechanisms by which it has been extended, and some of the challenges being addressed as it evolves. We also discuss the lessons learned through the project, with the aim of enabling researchers in other domains to learn from the success of BIDS
- …