Context. The extragalactic background light (EBL) contains information about the evolution of galaxies from very early times up to the present. The spectral energy distribution is not known ...accurately, especially in the near- and mid-infrared range. Upper limits and absolute measurements come from direct observations which might be be polluted by foreground emission, while indirect upper limits can also be set by observations of high energy gamma-ray sources. Galaxy number counts integrations of observable galaxies, missing possible faint sources, give strict lower limits. Aims. A model is constructed, which reproduces the EBL lower limit flux. This model can be used for a guaranteed minimum correction of observed spectra of extragalactic gamma-ray sources for extragalactic absorption. Methods. A forward evolution model for the metagalactic radiation field is used to fit recent observations of satelites like Spitzer, ISO, Hubble and GALEX. The model is applied to calculate the Fazio-Stecker relation, and to compute the absorption factor at different redshifts and corrected blazar spectra. Results. A strict lower-limit flux for the evolving extragalactic background light (and in particular the cosmic infrared background) has been calculated up to a redshift of five. The computed flux is below the existing upper limits from direct observations, and agrees with all existing limits derived from very-high energy gamma-ray observations. The corrected spectra still agree with simple theoretical predictions. The derived strict lower-limit EBL flux is very close to the upper limits from gamma-ray observations. This is true for the present day EBL, but also for the diffuse flux at higher redshift. Conclusions. If future detections of high redshift gamma-ray sources require a lower EBL flux than derived here, the physics assumptions used to derive the upper limits have to be revised. The lower-limit EBL model is not only needed for absorption features in active galactic nuclei and other gamma-ray sources, but is also essential when alternative particle processes are tested, which could prevent the high energy gamma-rays from being absorbed. It can also be used for a guaranteed interaction of cosmic-ray particles. The model is available online.
Context.
According to the current paradigm of galaxy formation, the first galaxies likely formed within large dark matter haloes. The fragmentation of these massive haloes led to the formation of ...galaxy protoclusters, which are usually composed of one to a few bright objects, surrounded by numerous fainter (and less massive) galaxies. These early structures could have played a major role in reionising the neutral hydrogen within the first billion years of the Universe, especially if their number density is significant.
Aims.
Taking advantage of the unprecedented sensitivity reached by the
James Webb
Space Telescope (JWST), galaxy protoclusters can now be identified and studied in increasing numbers beyond
z
≥ 6. Characterising their contribution to the UV photon budget could supply new insights into the reionisation process.
Methods.
We analysed the first JWST dataset behind SMACS0723−7327 to search for protoclusters at
z
≥ 6, combining the available spectroscopic and photometric data. We then compared our findings with semi-analytical models and simulations.
Results.
In addition to two bright galaxies (≤26.5 AB in
F
277
W
), separated by ∼11″and spectroscopically confirmed at
z
spec
= 7.66, we identify six additional galaxies with similar colours within a
θ
∼ 20″ radius (corresponding to
R
∼ 60 − 90 kpc in the source plane). Using several methods, we estimate the mass of the dark matter halo of this protocluster as ∼3.3 × 10
11
M
⊙
, accounting for magnification, consistent with various predictions. The physical properties of all protocluster members are also in excellent agreement with what has been previously found at lower redshifts: star formation main sequence and protocluster size. This detection adds to just a few protoclusters currently known in the first billion years of the universe. These
z
≥ 7 galaxy protoclusters may play an important role in cosmic reionisation.
The
Planck
satellite has identified more than 2000 protocluster candidates with extreme star formation rates (SFRs). Here, we present the spectroscopic identification of a
Planck
-selected ...protocluster located in the Cosmos field, PHz G237.01+42.50. PHz G237.01+42.50 contains a galaxy overdensity of 31 spectroscopically identified galaxies at
z
≃ 2.16 (significant at 5.4
σ
) in a 10′ × 11′ region. The overdensity contains two substructures or protoclusters at ⟨
z
⟩ ≃ 2.16 and 2.195 with estimated halo masses at
z
= 0 of ∼5–6 × 10
14
M
⊙
, roughly consistent with Virgo-type clusters. The overdensity total SFR, ∼4000
M
⊙
yr
−1
, is higher than predicted by simulations but much smaller than the SFR derived from the
Planck
data (i.e., 10 173
M
⊙
yr
−1
). The analysis of the
Herschel
data in the field, in combination with the available ancillary data, shows that such a difference is due to an effect of source alignment along the line of sight that produces a 5
σ
overdensity of red
Herschel
sources in the field. We analyze the members’ ultraviolet (UV) spectra and UV-far-infrared spectral energy distributions to derive their SFR, stellar mass, and metallicity. Galaxy members include blue star-forming galaxies and Active galactic nuclei (AGN) with SFRs and stellar masses consistent with the main sequence. Active galactic nuclei, identified through optical spectroscopy or X-ray data, represent a significant fraction (20 ± 10%) of all members of the protocluster at
z
= 2.16, and they are powerful enough to produce radiative feedback. The core of this protocluster, besides being denser, includes members that are, on average, more massive and star-forming and contains a larger fraction of AGN and
Herschel
-detected galaxies than the full sample, suggesting an environmental effect on galaxy growth. A comparison between PHz G237.01+42.50 and other protoclusters in the literature at similar redshifts reveals some common traits and differences that reflect both observational biases and a diversity in intrinsic properties that is not yet fully understood.
Aims. We aim to place stronger lower limits on the cosmic infrared background (CIB) brightness at 24 μm, 70 μm and 160 μm and measure the extragalactic number counts at these wavelengths in a ...homogeneous way from various surveys. Methods. Using Spitzer legacy data over 53.6 deg2 of various depths, we build catalogs with the same extraction method at each wavelength. Completeness and photometric accuracy are estimated with Monte-Carlo simulations. Number count uncertainties are estimated with a counts-in-cells moment method to take galaxy clustering into account. Furthermore, we use a stacking analysis to estimate number counts of sources not detected at 70 μm and 160 μm. This method is validated by simulations. The integration of the number counts gives new CIB lower limits. Results. Number counts reach 35 μJy, 3.5 mJy and 40 mJy at 24 μm, 70 μm, and 160 μm, respectively. We reach deeper flux densities of 0.38 mJy at 70, and 3.1 at 160 μm with a stacking analysis. We confirm the number count turnover at 24 μm and 70 μm, and observe it for the first time at 160 μm at about 20 mJy, together with a power-law behavior below 10 mJy. These mid- and far-infrared counts: 1) are homogeneously built by combining fields of different depths and sizes, providing a legacy over about three orders of magnitude in flux density; 2) are the deepest to date at 70 μm and 160 μm; 3) agree with previously published results in the common measured flux density range; 4) globally agree with the Lagache et al. (2004) model, except at 160 μm, where the model slightly overestimates the counts around 20 and 200 mJy. Conclusions. These counts are integrated to estimate new CIB firm lower limits of $2.29_{-0.09}^{+0.09}$ nW m-2 sr-1, $5.4_{-0.4}^{+0.4}$ nW m-2 sr-1, and $8.9_{-1.1}^{+1.1}$ nW m-2 sr-1 at 24 μm, 70 μm, and 160 μm, respectively, and extrapolated to give new estimates of the CIB due to galaxies of $2.86_{-0.16}^{+0.19}$ nW m-2 sr-1, $6.6_{-0.6}^{+0.7}$ nW m-2 sr-1, and $14.6_{-2.9}^{+7.1}$ nW m-2 sr-1, respectively. Products (point spread function, counts, CIB contributions, software) are publicly available for download at http://www.ias.u-psud.fr/irgalaxies/
The COVID-19 pandemic necessitated a change in our practice in the management of pediatric soft-tissue injuries. Patients were managed conservatively whenever possible. Our aim in this study was to ...see whether this more conservative approach adversely affected clinical, and patient-reported outcomes, including scarring. A prospective record of children presenting to the plastic surgery “Early Bird” clinic for pediatric trauma between 01.04.2020 and 30.06.2020 was kept. Electronic patient records were reviewed. An outpatient telephone clinic was scheduled for all patients. Parents were asked about complications and what they thought about the scar and to rate it as either: “poor,” “satisfactory,” “good,” or “excellent.” There were 240 patients, including 136 (57%) males and 104 (43%) females. The most frequent type of injury was a facial laceration in 123 patients (51.3%), followed by hand lacerations in 43 (17.9%), fingertip injuries in 31 (12.9%), and others. Ninety out of 240 (37.5%) were offered surgery. Follow-up times ranged from 17 to 20 months. Most parents (86.2%) were happy with the scarring and reported it as “good” or “excellent.” The proportion rating the scar “excellent” or “good” was similar in the non-operated cohort (i.e., 85.5%) versus the operated cohort (88.5%) (p-value 0.16). The overall complication rate of patients seen during this time was 5.9%; 7.4% in the conservatively managed and 4.9% of those who went to the theater. Despite managing more wounds, including some dog bites, conservatively, patients and parents reported low complication rates and high levels of satisfaction with the final scarring.
Abstract
Observational investigations of the abundance of massive precursors of local galaxy clusters (‘proto-clusters’) allow us to test the growth of density perturbations, to constrain ...cosmological parameters that control it, to test the theory of non-linear collapse and how the galaxy formation takes place in dense environments. The Planck collaboration has recently published a catalogue of ≳2000 cold extragalactic sub-millimeter sources, i.e. with colours indicative of z ≳ 2, almost all of which appear to be overdensities of star-forming galaxies. They are thus considered as proto-cluster candidates. Their number densities (or their flux densities) are far in excess of expectations from the standard scenario for the evolution of large-scale structure. Simulations based on a physically motivated galaxy evolution model show that essentially all cold peaks brighter than S
545GHz = 500 mJy found in Planck maps after having removed the Galactic dust emission can be interpreted as positive Poisson fluctuations of the number of high-z dusty proto-clusters within the same Planck beam, rather then being individual clumps of physically bound galaxies. This conclusion does not change if an empirical fit to the luminosity function of dusty galaxies is used instead of the physical model. The simulations accurately reproduce the statistic of the Planck detections and yield distributions of sizes and ellipticities in qualitative agreement with observations. The redshift distribution of the brightest proto-clusters contributing to the cold peaks has a broad maximum at 1.5 ≤ z ≤ 3. Therefore follow-up of Planck proto-cluster candidates will provide key information on the high-z evolution of large scale structure.
There is a lack of large samples of spectroscopically confirmed clusters and protoclusters at high redshifts, z > 1.5. Discovering and characterizing distant (proto-)clusters is important for ...yielding insights into the formation of large-scale structure and on the physical processes responsible for regulating star-formation in galaxies in dense environments. The Spitzer Planck Herschel Infrared Cluster (SPHerIC) survey was initiated to identify these characteristically faint and dust-reddened sources during the epoch of their early assembly. We present Spitzer/IRAC observations of 82 galaxy (proto-)cluster candidates at 1.3 < zp < 3.0 that were vetted in a two step process: (1) using Planck to select by color those sources with the highest star-formation rates, and (2) using Herschel at higher resolution to separate out the individual red sources. The addition of the Spitzer data enables efficient detection of the central and massive brightest red cluster galaxies (BRCGs). We find that BRCGs are associated with highly significant, extended and crowded regions of IRAC sources which are more overdense than the field. This result corroborates our hypothesis that BRCGs within the Planck–Herschel sources trace some of the densest and actively star-forming proto-clusters in the early Universe. On the basis of a richness-mass proxy relation, we obtain an estimate of their mean masses which suggests our sample consists of some of the most massive clusters at z ≈ 2 and are the likely progenitors of the most massive clusters observed today.
We present an analysis of CO spectroscopy and infrared-to-millimetre dust photometry of 11 exceptionally bright far-infrared (FIR) and sub-mm sources discovered through a combination of the Planck ...all-sky survey and follow-up Herschel-SPIRE imaging – “Planck’s Dusty Gravitationally Enhanced subMillimetre Sources”. Each source has a secure spectroscopic redshift z = 2.2–3.6 from multiple lines obtained through a blind redshift search with EMIR at the IRAM 30-m telescope. Interferometry was obtained at IRAM and the SMA, and along with optical/near-infrared imaging obtained at the CFHT and the VLT reveal morphologies consistent with strongly gravitationally lensed sources, including several giant arcs. Additional photometry was obtained with JCMT/SCUBA-2 and IRAM/GISMO at 850 μm and 2 mm, respectively. The SEDs of our sources peak near either the 350 μm or 500 μm bands of SPIRE with peak flux densities between 0.35 and 1.14 Jy. All objects are extremely bright isolated point sources in the 18′′ beam of SPIREat 250 μm, with apparent FIR luminosities of up to 3 × 1014 L⊙ (not correcting for the lensing effect). Their morphologies, sizes, CO line widths, CO luminosities, dust temperatures, and FIR luminosities provide additional empirical evidence that these are amongst the brightest strongly gravitationally lensed high-redshift galaxies on the sub-mm sky. Our programme extends the successful wide-area searches for strongly gravitationally lensed high-redshift galaxies (carried out with the South Pole Telescope and Herschel) towards even brighter sources, which are so rare that their systematic identification requires a genuine all-sky survey like Planck. Six sources are above the ≃600 mJy 90% completeness limit of the Planck catalogue of compact sources (PCCS) at 545 and 857 GHz, which implies that these must literally be amongst the brightest high-redshift FIR and sub-mm sources on the extragalactic sky. We discuss their dust masses and temperatures, and use additional WISE 22-μm photometry and template fitting to rule out a significant contribution of AGN heating to the total infrared luminosity. Six sources are detected in FIRST at 1.4 GHz, and the others have sensitive upper limits. Four have flux densities brighter than expected from the local FIR-radio correlation, but in the range previously found for high-z sub-mm galaxies, one has a deficit of FIR emission, and 6 are consistent with the local correlation, although this includes 3 galaxies with upper limits. We attribute this to the turbulent interstellar medium of these galaxies, rather than the presence of radio AGN. The global dust-to-gas ratios and star-formation efficiencies of our sources are predominantly in the range expected from massive, metal-rich, intense, high-redshift starbursts. An extensive multi-wavelength follow-up programme is being carried out to further characterize these sources and the intense star formation within them.
Astrophysical images issued from different instruments and/or spectral bands often require to be processed together, either for fitting or comparison purposes. However each image is affected by an ...instrumental response, also known as point-spread function (PSF), that depends on the characteristics of the instrument as well as the wavelength and the observing strategy. Given the knowledge of the PSF in each band, a straightforward way of processing images is to homogenise them all to a target PSF using convolution kernels, so that they appear as if they had been acquired by the same instrument. We propose an algorithm that generates such PSF-matching kernels, based on Wiener filtering with a tunable regularisation parameter. This method ensures all anisotropic features in the PSFs to be taken into account. We compare our method to existing procedures using measured Herschel/PACS and SPIRE PSFs and simulated JWST/MIRI PSFs. Significant gains up to two orders of magnitude are obtained with respect to the use of kernels computed assuming Gaussian or circularised PSFs. A software to compute these kernels is available at https://github.com/aboucaud/pypher
Display omitted
•Low particle size Ru nanoparticles were deposited on CeO2 interfaced with YSZ.•Both positive and negative polarization showed pronounced effect for C2H4 oxidation.•Electroreduction ...of Ce4+ to Ce3+, caused stronger interaction with Ru.•Partial reduction of Ce4+ was supported by XPS analysis of fresh and spent catalyst.•Showed feasibility of in-situ alteration of MSI of a highly dispersed Ru catalyst.
Small particle size (1.1nm) Ru nanoparticles were supported on a mixed ionic-electronic conductor, CeO2, with a low metal loading (1wt%), interfaced with a YSZ electrolyte. A pronounced enhancement (up to about 2.5 times) of the catalytic rate for the complete oxidation of ethylene was observed for negative polarization. The opposite effect was observed for positive polarization. Apparent Faradaic efficiencies up to 96 were determined, indicating a non-Faradaic effect. The modification of the cerium oxidation state (i.e., reduction from Ce4+ to Ce3+) is proposed to enhance the catalytic performance of the Ru nanoparticles. XPS analysis was performed to confirm this reduction of ceria. The enhancement of catalytic activity is attributed to the presence of more oxygen vacancies in the ceria interlayer causing a stronger metal-support interaction. Results demonstrate the feasibility of in-situ modification of the metal support-interaction between Ru nanoparticles and CeO2 catalytic support by a small current (−2μA) application.
PDF
