Environmental dependence of AGN activity and star formation in galaxy clusters from Magneticum simulations

(Abridged) Cluster environment has a strong impact on the star formation rate and AGN activity in cluster galaxies. In this work, we investigate the behaviour of different galaxy populations in galaxy clusters and their vicinity by means of cosmological hydrodynamical simulations. We studied galaxies with stellar mass $\log M_\ast (M_\odot) > 10.15$ in galaxy clusters with mass $M_{500} > 10^{13} M_\odot$ extracted from box2b (640 comoving Mpc/$h$) of the Magneticum Pathfinder suite of cosmological hydrodynamical simulations at redshifts 0.25 and 0.90. We examined the influence of stellar mass, distance to the nearest neighbouring galaxy, clustercentric radius, substructure membership and large-scale surroundings on the fraction of galaxies hosting an AGN, star formation rate and the ratio between star-forming and quiescent galaxies. We found that in low-mass galaxies, AGN activity and star formation are similarly affected by the environment and decline towards the cluster centre. In massive galaxies, the impact is different; star-formation level increases in the inner regions and peaks between 0.5 and 1 $R_{500}$ with a rapid decline in the centre, whereas AGN activity declines in the inner regions and rapidly rises below $R_{500}$ towards the centre - likely due to stellar mass stripping and the consequent selection of galaxies with more massive black holes. After disentangling the contributions of neighbouring cluster regions, we found an excess of AGN activity in massive galaxies on the cluster outskirts ($\sim 3 R_{500}$). We also found that the local density, substructure membership and stellar mass strongly influence star formation and AGN activity but verified that they cannot fully account for the observed radial trends.Comment: Submitted to A&A, 14 pages, 12 figures, 1 tabl

Microstructure, mechanical and electrical properties of Glass Fiber Reinforced Composites (GFRC)

In this study, the influence of E-glass fiber and mineral filler content on the microstructure, physical, mechanical and dielectric properties of Glass Fiber Reinforced Composites (GFRC) was investigated. Five sets of GFRC, based on polymer resin with varying E-grade glass fibers and CaCO3 mineral filler weight fractions (15/64, 20/59, 25/54, 30/49, 35/44), were commercially prepared. Test specimens were prepared by compression molding. Scanning Electron Microscope images revealed that at higher concentrations, the fibers clustered together, resulting in heterogeneous microstructures. Characterization of the composites showed that glass fiber content and distribution significantly affects the mechanical properties. The flexural strength of the composites decreased with increasing glass fiber content. The dielectric constant ε` decreased with increasing fiber content

Microstructural analysis of Bulk Molding Compounds and correlation with the flexural strength

In this study, the influence of the glass fiber (GF) content on the microstructure and flexural strength of bulk molding compounds (BMCs) is investigated. Three sets of BMCs with different weight fractions of GF (5/10/12.5 wt%) were commercially prepared and compression molded into test specimens. The microstructure of the composites was analysed by scanning electron microscopy and further quantitatively characterized by Voronoi analysis in order to define the degree of the fiber distribution homogeneity. The experimental results were compared to the modelled microstructures. The results revealed that the fiber distribution in the composite with 5 wt% of GF is considered as the most homogeneous. Through the obtained microstructural descriptors, the fiber weight content and their distribution were correlated to the flexural strength of BMCs. The flexural strength was the highest for the composite with 10 wt% of GF

CANUCS: An Updated Mass and Magnification Model of Abell 370 with JWST

We report an updated mass and magnification model of galaxy cluster Abell 370 using new NIRCam and NIRISS data from the CAnadian NIRISS Unbiased Cluster Survey (CANUCS). Using Lenstool and a combination of archival HST and MUSE data with new JWST data as constraints, we derive an improved gravitational lensing model and extract magnifications of background galaxies with uncertainties. Using our best fit model, we perform a search for new multiply imaged systems via predicted positions. We report no new multiply imaged systems with identifiable redshifts, likely due to already very deep HST and Spitzer data, but confirm a $z\sim8$ multiply imaged system by measuring its redshift with NIRISS and NIRSpec spectra. We find that the overall shape of the critical curve for a source at $z = 9.0$ is similar to previous models of Abell 370, with small changes. We investigate the $z\sim8$ galaxy with two images observable with an apparent magnitude in the F125W band of $26.0\pm0.2$ and $25.6\pm0.1$. After correcting for the magnifications of the images, 7.2$^{+0.2}_{-1.2}$ and 8.7$^{+0.4}_{-0.4}$, we use SED fitting to find an intrinsic stellar mass of log($M^*/M_{\odot})$ = 7.35$^{+0.04}_{-0.05}$, intrinsic SFR of 3.5$^{+2.2}_{-1.4}$ M$_{\odot}$/yr, and $M_{UV}$ of -21.3$^{+0.2}_{-0.2}$, which is close to the knee of the luminosity function at that redshift. Our model, and corresponding magnification, shear, and convergence maps are available on request and will be made publicly available on MAST in a CANUCS data release (DOI: 10.17909/ph4n-6n76).Comment: 15 page

Λ\LambdaCDM not dead yet: massive high-z Balmer break galaxies are less common than previously reported

Early JWST observations that targeted so-called double-break sources (attributed to Lyman and Balmer breaks at $z>7$), reported a previously unknown population of very massive, evolved high-redshift galaxies. This surprising discovery led to a flurry of attempts to explain these objects' unexpected existence including invoking alternatives to the standard $\Lambda$CDM cosmological paradigm. To test these early results, we adopted the same double-break candidate galaxy selection criteria to search for such objects in the JWST images of the CAnadian NIRISS Unbiased Cluster Survey (CANUCS), and found a sample of 19 sources over five independent CANUCS fields that cover a total effective area of $\sim60\,$arcmin$^2$ at $z\sim8$. However, (1) our SED fits do not yield exceptionally high stellar masses for our candidates, while (2) spectroscopy of five of the candidates shows that while all five are at high redshifts, their red colours are due to high-EW emission lines in star-forming galaxies rather than Balmer breaks in massive, evolved systems. Additionally, (3) field-to-field variance leads to differences of $\sim 1.5$ dex in the maximum stellar masses measured in the different fields, suggesting that the early single-field JWST observations may have suffered from cosmic variance and/or sample bias. Finally, (4) we show that the presence of even a single massive outlier can dominate conclusions from small samples such as those in early JWST observations. In conclusion, we find that the double-break sources in CANUCS are not sufficiently massive or numerous to warrant questioning the standard $\Lambda$CDM paradigm.Comment: V2: correction of display problem of Fig.1 in Chrome browser. Submitted to MNRAS, 10 pages (+4 in Appendix), 5 figures (+4), 1 table (+1

A Steep Decline in the Galaxy Space Density Beyond Redshift 9 in the CANUCS UV Luminosity Function

We present a new sample of 158 galaxies at redshift $z>7.5$ selected from deep \jwst\ NIRCam imaging of five widely-separated sightlines in the CANUCS survey. Two-thirds of the pointings and 80\% of the galaxies are covered by 12 to 14 NIRCam filters, including seven to nine medium bands, providing accurate photometric redshifts and robustness against low redshift interlopers. A sample of 28 galaxies at $z>7.5$ with spectroscopic redshifts shows a low systematic offset and scatter in the difference between photometric and spectroscopic redshifts. We derive the galaxy UV luminosity function at redshifts 8 to 12, finding a slightly higher normalization than previously seen with \hst\ at redshifts 8 to 10. We observe a steeper decline in the galaxy space density from $z=8$ to $12$ than found by most \jwst\ Cycle 1 studies. In particular, we find only eight galaxies at $z>10$ and none at $z>12.5$, with no $z>10$ galaxies brighter than F277W AB=28 or $M_{\rm UV}=-20$ in our unmasked, delensed survey area of 53.4 square arcminutes. We attribute the lack of bright $z>10$ galaxies in CANUCS compared to GLASS and CEERS to intrinsic variance in the galaxy density along different sightlines. The evolution in the CANUCS luminosity function between $z=8$ and $12$ is comparable to that predicted by simulations that assume a standard star formation efficiency, without invoking any special adjustments.Comment: 30 pages, 12 figures, ApJ, in pres