31 research outputs found
Early results from GLASS-JWST XVI: Discovering a bluer z~4-7 Universe through UV slopes
We use the GLASS-JWST Early Release Science NIRCam parallel observations to
provide a first view of the UV continuum properties of NIRCam/F444W selected
galaxies at 4<z<7. By combining multiwavelength NIRCam observations, we
constrain the UV continuum slope for a sample of 401 galaxies with stringent
quality controls. We find that >99% of the galaxies are blue star-forming
galaxies with very low levels of dust (Avbeta~0.01+/-0.33). We find no
statistically significant correlation for UV slope with redshift or UV
magnitude. However, we find that in general galaxies at higher redshifts and
fainter UV magnitudes have steeper UV slopes. We find a statistically
significant correlation for UV slope with stellar mass, with galaxies with
higher stellar mass showing shallower UV slopes. Individual fits to some of our
galaxies reach the bluest UV slopes of beta~-3.1 allowed by stellar population
models used in this analysis. Therefore, it is likely that stellar population
models with higher amount of Lyman continuum leakage, AGN effects, and/or
Population III contributions are required to accurately reproduce the rest-UV
and optical properties of some of our bluest galaxies. This dust-free early
view confirms that our current cosmological understanding of gradual mass +
dust buildup of galaxies with cosmic time is largely accurate to describe the
~0.7-1.5 Gyr age window of the Universe. The abundance of a large population of
UV faint dust-poor systems may point to a dominance of low-mass galaxies at z>6
playing a vital role in cosmic reionization.Comment: Accepted in ApJ
The stellar metallicities of massive quiescent galaxies at 1.0 < z < 1.3 from KMOS+VANDELS
We present a rest-frame UV-optical stacked spectrum representative of massive
quiescent galaxies at . The stack
is constructed using VANDELS survey data, combined with new KMOS observations.
We apply two independent full-spectral-fitting approaches, measuring a total
metallicity, [Z/H]= with Bagpipes, and [Z/H]= with
Alf, a fall of dex compared with the local Universe. We also
measure an iron abundance, [Fe/H] =, a fall of dex
compared with the the local Universe. We measure the alpha enhancement via the
magnesium abundance, obtaining [Mg/Fe]=0.12, consistent with
similar-mass galaxies in the local Universe, indicating no evolution in the
average alpha enhancement of log quiescent galaxies over
the last Gyr. This suggests the very high alpha enhancements recently
reported for several bright quiescent galaxies are due to their
extreme masses, log, rather than being typical
of the population. The metallicity evolution we observe with
redshift (falling [Z/H], [Fe/H], constant [Mg/Fe]) is consistent with recent
studies. We recover a mean stellar age of Gyr,
corresponding to a formation redshift, z_\rm{form}=2.4^{+0.6}_{-0.3}. Recent
studies have obtained varying average formation redshifts for
massive quiescent galaxies, and, as these studies report consistent
metallicities, we identify different star-formation-history models as the most
likely cause. Larger spectroscopic samples from upcoming ground-based
instruments will provide precise constraints on ages and metallicities at
. Combining these with precise JWST quiescent-galaxy
stellar-mass functions will provide an independent test of formation redshifts
derived from spectral fitting.Comment: 16 pages, 3 figures, accepted for publication in Ap
Early Results from GLASS-JWST. XXI: Rapid assembly of a galaxy at z=6.23 revealed by its C/O abundance
The abundance of carbon relative to oxygen (C/O) is a promising probe of star
formation history in the early universe, as the ratio changes with time due to
production of these elements by different nucleosynthesis pathways. We present
a measurement of (stat) (sys)
in a galaxy observed as part of the GLASS-JWST Early Release Science
Program. Notably, we achieve good precision thanks to the detection of the
rest-frame ultraviolet O III], C III], and C IV emission lines delivered by
JWST/NIRSpec. The C/O abundance is 0.8 dex lower than the solar value and
is consistent with the expected yield from core-collapse supernovae, indicating
that longer-lived intermediate mass stars have not fully contributed to carbon
enrichment. This in turn implies rapid buildup of a young stellar population
with age Myr in a galaxy seen 900 million years after the
Big Bang. Our chemical abundance analysis is consistent with spectral energy
distribution modeling of JWST/NIRCam photometric data, which indicates a
current stellar mass and specific star formation rate sSFR
Gyr. These results showcase the value of chemical abundances and C/O in
particular to study the earliest stages of galaxy assembly.Comment: 16 pages, 4 figures, 2 tables. Accepted for publication in ApJ
Early results from GLASS-JWST. III: Galaxy candidates at z9-15
We present the results of a first search for galaxy candidates at
z9--15 on deep seven-bands NIRCam imaging acquired as part of the
GLASS-JWST Early Release Science Program on a flanking field of the Frontier
Fields cluster A2744. Candidates are selected via two different renditions of
the Lyman-break technique, isolating objects at z9-11, and z9-15,
respectively, supplemented by photometric redshifts obtained with two
independent codes. We find six color-selected candidates at z9, plus one
additional candidate with photometric redshift z9. In particular,
we identify two bright candidates at that are
unambiguously placed at and , respectively. The
total number of galaxies discovered at is in line with the predictions of
a non-evolving LF. The two bright ones at are unexpected given the
survey volume, although cosmic variance and small number statistics limits
general conclusions. This first search demonstrates the unique power of JWST to
discover galaxies at the high redshift frontier. The candidates are ideal
targets for spectroscopic follow-up in cycle.Comment: Submitted to ApJL, 9 pages, 4 figure
Early results from GLASS-JWST. XX: Unveiling a population of "red-excess'' galaxies in Abell2744 and in the coeval field
We combine JWST/NIRCam imaging and MUSE data to characterize the properties
of galaxies in different environmental conditions in the cluster Abell2744
() and in its immediate surroundings. We investigate how galaxy
colors, morphology and star forming fractions depend on wavelength and on
different parameterizations of environment. Our most striking result is the
discovery of a ``red-excess'' population in F200WF444W colors both in the
cluster regions and the field. These galaxies have normal F115WF150W colors,
but are up to 0.8 mag redder than red sequence galaxies in F200WF444W. They
also have rather blue rest frame BV colors. {Galaxies in the field and at
the cluster virial radius are overall characterized by redder colors, but
galaxies with the largest color deviations are found in the field and in the
cluster core. Several results} suggest that mechanisms taking place in these
regions might be more effective in producing these colors. Looking at their
morphology, many cluster galaxies show signatures consistent with ram pressure
stripping, while field galaxies have features resembling interactions and
mergers. Our hypothesis is that these galaxies are characterized by dust
enshrouded star formation: a JWST/NIRSpec spectrum for one of the galaxies is
dominated by a strong PAH at 3.3, suggestive of dust obscured star
formation. Larger spectroscopic samples are needed to understand if the color
excess is due exclusively to dust-obscured star formation, and the role of
environment in triggering it.Comment: ApJL in pres
Final CONNECT Architecture
Interoperability remains a fundamental challenge when connecting heterogeneous systems which encounter and spontaneously communicate with one another in pervasive computing environments. This challenge is exasperated by the highly heterogeneous technologies employed by each of the interacting parties, i.e., in terms of hardware, operating system, middleware protocols, and application protocols. The key aim of the CONNECT project is to drop this heterogeneity barrier and achieve universal interoperability. Here we report on the revised CONNECT architecture, highlighting the integration of the work carried out to integrate the CONNECT enablers developed by the different partners; in particular, we present the progress of this work towards a finalised concrete architecture. In the third year this architecture has been enhanced to: i) produce concrete CONNECTors, ii) match networked systems based upon their goals and intent, and iii) use learning technologies to find the affordance of a system. We also report on the application of the CONNECT approach to streaming based systems, further considering exploitation of CONNECT in the mobile environment
Finalised dependability framework and evaluation results
The ambitious aim of CONNECT is to achieve universal interoperability between heterogeneous Networked Systems by means of on-the-fly synthesis of the CONNECTors through which they communicate. The goal of WP5 within CONNECT is to ensure that the non-functional properties required at each side of the connection going to be established are fulfilled, including dependability, performance, security and trust, or, in one overarching term, CONNECTability. To model such properties, we have introduced the CPMM meta-model which establishes the relevant concepts and their relations, and also includes a Complex Event language to express the behaviour associated with the specified properties. Along the four years of project duration, we have developed approaches for assuring CONNECTability both at synthesis time and at run-time. Within CONNECT architecture, these approaches are supported via the following enablers: the Dependability and Performance analysis Enabler, which is implemented in a modular architecture supporting stochastic verification and state-based analysis. Dependability and performance analysis also relies on approaches for incremental verification to adjust CONNECTor parameters at run-time; the Security Enabler, which implements a Security-by-Contract-with-Trust framework to guarantee the expected security policies and enforce them accordingly to the level of trust; the Trust Manager that implements a model-based approach to mediate between different trust models and ensure interoperable trust management. The enablers have been integrated within the CONNECT architecture, and in particular can interact with the CONNECT event-based monitoring enabler (GLIMPSE Enabler released within WP4) for run-time analysis and verification. To support a Model-driven approach in the interaction with the monitor, we have developed a CPMM editor and a translator from CPMM to the GLIMPSE native language (Drools). In this document that is the final deliverable from WP5 we first present the latest advances in the fourth year concerning CPMM, Dependability&Performance Analysis, Incremental Verification and Security. Then, we make an overall summary of main achievements for the whole project lifecycle. In appendix we also include some relevant articles specifically focussing on CONNECTability that have been prepared in the last period
Revised CONNECT Architecture
Interoperability remains a fundamental challenge when connecting heterogeneous systems which encounter and spontaneously communicate with one another in pervasive computing environments. This challenge is exasperated by the highly heterogeneous technologies employed by each of the interacting parties, i.e., in terms of hardware, operating system, middleware protocols, and application protocols. The key aim of the CONNECT project is to drop this heterogeneity barrier and achieve universal interoperability. Here we report on the revised CONNECT architecture, highlighting the integration of the work carried out to integrate the CONNECT enablers developed by the different partners; in particular, we present the progress of this work towards a finalised concrete architecture. In the third year this architecture has been enhanced to: i) produce concrete CONNECTors, ii) match networked systems based upon their goals and intent, and iii) use learning technologies to find the affordance of a system. We also report on the application of the CONNECT approach to streaming based systems, further considering exploitation of CONNECT in the mobile environment
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
Design of Approaches for Dependability and Initial Prototypes
The aim of CONNECT is to achieve universal interoperability between heterogeneous Networked Systems. For this, the non-functional properties required at each side of the connection going to be established must be fulfilled. By the one inclusive term "CONNECTability" we comprehend properties belonging to all four non-functional concerns of interest for CONNECT, namely dependability, performance, security and trust. We model such properties in conformance with a meta-model which establishes the relevant concepts and their relations. Then, building on the conceptual models proposed in the first year in Deliverable D5.1, in this document we present the approaches developed for assuring CONNECTability both at synthesis time and at runtime. The contributions include: the Dependability&Performance analysis Enabler, for which we release a modular architecture supporting stochastic verification and state-based analysis; incremental verification and event-based monitoring for runtime analysis; a model-based approach to interoperable trust management; the Security-by-Contract-with-Trust framework, which guarantees and enforces the expected trust levels and security policies