Star formation (SF) in the galaxy populations of local massive clusters is reduced with respect to field galaxies, and tends to be suppressed in the core region. Indications of a reversal of the ...SF-density relation have been observed in a few z > 1.4 clusters. Using deep imaging from 100-500 μm from Photodetector Array Camera and Spectrometer (PACS) and Spectral and Photometric Imaging REceiver (SPIRE) onboard Herschel, we investigate infrared properties of spectroscopic and photo-z cluster members, and of Hα emitters in XMMU J2235.3−2557, one of the most massive, distant, X-ray selected clusters known. Our analysis is based mostly on fitting of the galaxies spectral energy distribution (SED) in the rest-frame 8-1000 μm. We measure total IR luminosity, deriving star formation rates (SFRs) ranging from 89 to 463 M yr−1 for 13 galaxies individually detected by Herschel, all located beyond the core region (r >250 kpc). We perform a stacking analysis of nine star-forming members not detected by PACS, yielding a detection with SFR = 48 ± 16 M yr−1. Using a colour criterion based on a star-forming galaxy SED at the cluster redshift, we select 41 PACS sources as candidate star-forming cluster members. We characterize a population of highly obscured SF galaxies in the outskirts of XMMU J2235.3−2557. We do not find evidence for a reversal of the SF-density relation in this massive, distant cluster.
The ALMA Frontier Fields Survey Muñoz Arancibia, A. M.; González-López, J.; Ibar, E. ...
Astronomy and astrophysics (Berlin),
12/2018, Letnik:
620
Journal Article
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Context. Characterizing the number counts of faint (i.e., sub-mJy and especially sub-100 μJy), dusty star-forming galaxies is currently a challenge even for deep, high-resolution observations in the ...FIR-to-mm regime. They are predicted to account for approximately half of the total extragalactic background light at those wavelengths. Searching for dusty star-forming galaxies behind massive galaxy clusters benefits from strong lensing, enhancing their measured emission while increasing spatial resolution. Derived number counts depend, however, on mass reconstruction models that properly constrain these clusters. Aims. We aim to estimate the 1.1 mm number counts along the line of sight of three galaxy clusters, Abell 2744, MACS J0416.1–2403, and MACS J1149.5+2223, which are part of the ALMA Frontier Fields Survey. We have performed detailed simulations to correct these counts for lensing effects, probing down to the sub-mJy flux density level. Methods. We created a source catalog based on ALMA 1.1 mm continuum detections. We used several publicly available lensing models for the galaxy clusters to derive the intrinsic flux densities of these sources. We performed Monte Carlo simulations of the number counts for a detailed treatment of the uncertainties in the magnifications and adopted source redshifts. Results. We estimate lensing-corrected number counts at 1.1 mm using source detections down to S/N = 4.5. In each cluster field, we find an overall agreement among the number counts derived for the different lens models, despite their systematic variations regarding source magnifications and effective areas. Combining all cluster fields, our number counts span ∼2.5 dex in demagnified flux density, from several mJy down to tens of μJy. Both our differential and cumulative number counts are consistent with recent estimates from deep ALMA observations at a 3σ level. Below ≈0.1 mJy, however, our cumulative counts are lower by ≈1 dex, suggesting a flattening in the number counts. Conclusions. We derive 1.1 mm number counts around three well-studied galaxy clusters following a statistical approach. In our deepest ALMA mosaic, we estimate number counts for intrinsic flux densities ≈4 times fainter than the rms level. This highlights the potential of probing the sub-10 μJy population in larger samples of galaxy cluster fields with deeper ALMA observations.
We present a multi-wavelength study of galaxy populations in the core of the massive, X-ray luminous cluster XMMU J2235 at z = 1.39, based on high quality VLT and HST photometry at optical and ...near-infrared wavelengths. We derive luminosity functions in the z, H, and Ks bands, approximately corresponding to restframe U, R and z band. These show a faint-end slope consistent with being flat, and a characteristic magnitude M∗ close to passive evolution predictions of M∗ of local massive clusters, with a formation redshift z > 2. The color − magnitude and color-mass diagrams show evidence of a tight red sequence (intrinsic scatter ≲ 0.08) of massive galaxies already in place, with overall old stellar populations and generally early-type morphology. Beside the red colors, these massive (>6 × 1010 M⊙) galaxies typically show early-type spectral features, and rest-frame far-UV emission consistent with very low star formation rates (SFR < 0.2 M⊙ yr-1). Star forming spectroscopic members, with SFR of up to ~100 M⊙/yr, are all located at clustercentric distances ≳ 250 kpc, with the central cluster region already appearing effectively quenched. Most part of the cluster galaxies more massive than 6 × 1010 M⊙ within the studied area do not appear to host significant levels of star formation. The high-mass end of the galaxy populations in the core of this cluster appears to be in a very advanced evolutionary stage, not only in terms of formation of the stellar populations, but also of the assembly of the stellar mass. The high-mass end of the galaxy stellar mass function is essentially already in place. The stellar mass fraction estimated within r500 (~1%, Kroupa IMF) is already similar to that of local massive clusters. On the other hand, surface brightness distribution modeling of the massive red sequence galaxies may suggest that their size is often smaller than expected based on the local stellar mass vs. size relation. An evolution of the stellar mass vs. size relation might imply that, in spite of the overall early assembly of these sources, their evolution is not complete, and processes like minor (and likely dry) merging might still shape the structural properties of these objects to resemble those of their local counterparts, without substantially affecting their stellar mass or host stellar populations. Nonetheless, a definite conclusion on the actual relevance of size evolution for the studied early-type sample is precluded by possible systematics and biases.
A numerical analysis was conducted to investigate the effect of varying the Oxygen Index (OI) of the oxidizer stream between 21 and 35% on soot production and thermal radiation emitted by laminar ...axisymmetric propane diffusion flames at atmospheric pressure. The extended enthalpy defect flamelet model, an acetylene/benzene-based two-equation semi-empirical soot production model, and the Full-Spectrum correlated-k radiative property model were used in the numerical simulations. The focus of this study is to demonstrate that it is important to account for the soot aging effect to correctly predict how increasing OI affects the predicted soot production. Three soot surface growth rate models were considered. The first model neglects the soot aging effect and assumes the soot surface growth rate is linearly dependent on soot surface area. The second and third models account for the soot aging effect by assuming the soot surface growth rate is proportional to the square-root of soot surface area and assuming a particle size-dependent sublinear soot surface area, respectively. The predicted flame height, soot volume fraction, radially integrated soot volume fraction and radiant fraction were compared to available experimental data. The first soot model predicted a much higher soot loading increase with increasing OI than observed experimentally. The second and third soot models improve considerably the predicted general behavior of soot loading increase with OI. Soot and combustion gases make comparable contribution to flame radiation under the conditions studied. When the soot aging effect is properly taken into account, the relatively efficient numerical code assessed in this study becomes a suitable tool for predicting soot production and thermal radiation in laminar propane diffusion flames at different OI conditions. Moreover, increasing OI of the oxidizer stream is a remarkable way to enhance the flame radiation where the correct estimation of soot production is essential to predict the radiant fraction of the flame.
Purpose This study's purpose was to determine the effectiveness of adding a preoperative interscalene brachial plexus block to standard postoperative management, including oral narcotics and a ...subacromial bupivacaine infusion pump, after arthroscopic shoulder surgery. Methods After performing a prospective power analysis and obtaining institutional board approval, we conducted a randomized placebo-controlled trial of 53 patients separated into a preoperative interscalene brachial plexus group and a control group. Group 1 received an interscalene block with 30 mL of 0.5% ropivacaine. Group 2 received a placebo with 10 mL of saline solution. All patients postoperatively received an arthroscopically placed subacromial infusion pump catheter for 72 hours and oral narcotics. Pain scores on a visual analog scale (VAS) and narcotic pill use were recorded at 6, 12, 20, 32, 40, 52, 60, 72, and 80 hours. Results Preoperative pain scores between groups were not significant ( P > .05). A statistically significant difference was found for decreased pain scores at 6 hours after discharge in patients receiving an interscalene block ( P = .001) (VAS of 30.9 in group 1 v 61.8 in group 2). There was also a decrease in the number of narcotic pills taken at the 6-hour time interval ( P = .1) (0.6 pills v 1.1 pills). Group 1 had a rebound phenomenon 20 hours after discharge. Pain scores spiked as the effects of the block wore off ( P = .08) (net change in VAS score increase, 25.0 v 10.3). No other statistical or clinical differences were observed. Conclusions The addition of a preoperative interscalene block to a postoperative subacromial infusion pump provided significant improvement of pain control only at 6 hours after discharge. Twelve hours after discharge, this benefit had disappeared. A rebound phenomenon of increased pain at 20 hours was seen after the interscalene block had worn off. After 20 hours, no statistically significant or clinically applicable differences were found. Level of Evidence Level I, randomized controlled trial.
We present a weak-lensing analysis of the z 1.4 galaxy cluster XMMU J2235.3 - 2557, based on deep Advanced Camera for Surveys images. Despite the observational challenge set by the high redshift of ...the lens, we detect a substantial lensing signal at the 8 Delta *s level. This clear detection is enabled in part by the high mass of the cluster, which is verified by our both parametric and non-parametric estimation of the cluster mass. Assuming that the cluster follows a Navarro-Frenk-White mass profile, we estimate that the projected mass of the cluster within r = 1 Mpc is (8.5 +/- 1.7) X 1014 M, where the error bar includes the statistical uncertainty of the shear profile, the effect of possible interloping background structures, the scatter in concentration parameter, and the error in our estimation of the mean redshift of the background galaxies. The high X-ray temperature 8.6+1.3 -1.2 keV of the cluster recently measured with Chandra is consistent with this high lensing mass. When we adopt the 1 Delta *s lower limit as a mass threshold and use the cosmological parameters favored by the Wilkinson Microwave Anisotropy Probe 5-year (WMAP5) result, the expected number of similarly massive clusters at z 1.4 in the 11 square degree survey is N ~ 5 X 10-3. Therefore, the discovery of the cluster within the survey volume is a rare event with a probability 1% and may open new scenarios in our current understanding of cluster formation within the standard cosmological model.
•An analytical method for view factor between the flame and radiometer is proposed.•Flame height and mass loss evolution with the time decreases with the moisture content.•Radiant fraction emitted ...decreases with the moisture content of wildland fuels.•Flame radiations correlations for all moisture content and wildland fuels are given.
This work addresses the effect of wildland fuel moisture content on flame radiation. A wildland fuel layer composed of Pinus radiata needles was experimentally studied using a specially designed burner, which produced small bench-scale laminar, non-premixed flames. These flames were suitable for the study of their emitted radiation providing stable, repeatable and axisymmetric flames. Pine needles were dried and then rehydrated to obtain four different moisture contents. The radiant fraction was estimated as the ratio between the radiant emission from the flame and its heat release rate. The radiant emission was determined with measurements from a radiometer and image analysis of the flame shape in order to estimate the view factor between the flame and the radiometer. The mass loss rate was measured to determine the heat release rate from the flame. This study confirms the decrease in radiant emission by increasing fuel moisture content. Also, the results indicate a small variation in the radiant fraction, despite the clear variations observed in flame shape and mass loss. Additionally, correlations between results were determined with the purpose of characterizing the effect of moisture content on the radiant fraction.
The ALMA Frontier Fields Survey Carvajal, R; Bauer, F E; Bouwens, R J ...
Astronomy and astrophysics (Berlin),
01/2020, Letnik:
633
Journal Article
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Context. The Hubble Frontier Fields offer an exceptionally deep window into the high-redshift universe, covering a substantially larger area than the Hubble Ultra-Deep field at low magnification and ...probing 1–2 mag deeper in exceptional high-magnification regions. This unique parameter space, coupled with the exceptional multi-wavelength ancillary data, can facilitate for useful insights into distant galaxy populations. Aims. We aim to leverage Atacama Large Millimetre Array (ALMA) band 6 (≈263 GHz) mosaics in the central portions of five Frontier Fields to characterize the infrared (IR) properties of 1582 ultraviolet (UV)-selected Lyman-Break Galaxies (LBGs) at redshifts of z ∼ 2–8. We investigated individual and stacked fluxes and IR excess (IRX) values of the LBG sample as functions of stellar mass (M⋆), redshift, UV luminosity and slope β, and lensing magnification. Methods. LBG samples were derived from color-selection and photometric redshift estimation with Hubble Space Telescope photometry. Spectral energy distributions -templates were fit to obtain luminosities, stellar masses, and star formation rates for the LBG candidates. We obtained individual IR flux and IRX estimates, as well as stacked averages, using both ALMA images and u–v visibilities. Results. Two (2) LBG candidates were individually detected above a significance of 4.1-σ, while stacked samples of the remaining LBG candidates yielded no significant detections. We investigated our detections and upper limits in the context of the IRX–M⋆ and IRX–β relations, probing at least one dex lower in stellar mass than past studies have done. Our upper limits exclude substantial portions of parameter space and they are sufficiently deep in a handful of cases to create mild tension with the typically assumed attenuation and consensus relations. We observe a clear and smooth trend between M⋆ and β, which extends to low masses and blue (low) β values, consistent with expectations from previous works.
ABSTRACT
Minor mergers have been proposed as the driving mechanism for the size growth of quiescent galaxies with decreasing redshift. The process whereby large star-forming galaxies quench and join ...the quiescent population at the large size end has also been suggested as an explanation for this size growth. Given the clear association of quenching with clusters, we explore this mechanism by studying the structural properties of 23 spectroscopically identified recently quenched (or ‘post-starburst’ (PSB)) cluster galaxies at z ∼ 1. Despite clear PSB spectral signatures implying rapid and violent quenching, 87 per cent of these galaxies have symmetric, undisturbed morphologies in the stellar continuum. Remarkably, they follow a mass–size relation lying midway between the star-forming and quiescent field relations, with sizes 0.1 dex smaller than z ∼ 1 star-forming galaxies at log(M*/M⊙) = 10.5. This implies a rapid change in the light profile without directly effecting the stellar distribution, suggesting changes in the mass-to-light ratio gradients across the galaxy are responsible. We develop fading toy models to explore how star-forming galaxies move across the mass–size plane as their stellar populations fade to match those of the PSBs. ‘Outside-in’ fading has the potential to reproduce the contraction in size and increase in bulge-dominance observed between star-forming and PSB cluster galaxies. Since cluster PSBs lie on the large size end of the quiescent mass–size relation, and our previous work shows cluster galaxies are smaller than field galaxies, the sizes of quiescent galaxies must grow both from the quenching of star-forming galaxies and dry minor mergers.
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