A Census of Baryons in Galaxy Clusters and Groups Gonzalez, Anthony H; Zaritsky, Dennis; Zabludoff, Ann I
Astrophysical journal/The Astrophysical journal,
09/2007, Letnik:
666, Številka:
1
Journal Article
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We determine the contribution of stars in galaxies, intracluster stars, and the intracluster medium to the total baryon budget in nearby galaxy clusters and groups. We find that the baryon mass ...fraction (f sub(b) = Omega sub(b)/ Omega sub(m)) within r sub(500) is constant for systems with M sub(500) between 6 x 10 super(13) and 1 x 10 super(15) M unk. Although f sub(b) is lower than the WMAP value, the shortfall is on the order of both the observational systematic uncertainties and the depletion of baryons within r sub(500) that is predicted by simulations. The data therefore provide no compelling evidence for undetected baryonic components, particularly any that would be expected to vary in importance with cluster mass. A unique feature of the current analysis is direct inclusion of the contribution of intracluster light (ICL) in the baryon budget. With the addition of the ICL to the stellar mass in galaxies, the increase in X-ray gas mass fraction with increasing total mass is entirely accounted for by a decrease in the total stellar mass fraction, supporting the argument that the behavior of both the stellar and X-ray gas components is dominated by a decrease in star formation efficiency in more massive environments. Within just the stellar component, the fraction of the total stellar luminosity in the central, giant brightest cluster galaxy (BCG) and ICL (hereafter the BCG+ICL component) decreases as velocity dispersion ( sigma ) increases for systems with 145 km s super(-1) less than or equal to sigma less than or equal to 1026 km s super(-1), suggesting that the BCG+ICL component, and in particular the dominant ICL component, grows less efficiently in higher mass environments. The degree to which this behavior arises from our sample selection, which favored systems with central, giant elliptical galaxies, remains unclear. A more robust result is the identification of low-mass groups with large BCG+ICL components, demonstrating that the creation of "intracluster" stars does not require a massive cluster environment. Within r sub(500) and r sub(200), the BCG+ICL contributes on average 40% and 33% of the total stellar light, respectively, for the clusters and groups in our sample. Because these fractions are functions of both enclosed radius and system mass, care should be exercised when comparing these values with other studies and simulations.
Robust methods for predicting thermal stabilities of collagen triple helices are critical for understanding natural structure and stability in the collagen family of proteins and also for designing ...synthetic peptides mimicking these essential proteins. In this work, we determine the relative stability imparted on the collagen triple helix by single amino acids and interactions between amino acid pairs. Using this analysis, we create a comprehensive algorithm, SCEPTTr, for predicting melting temperatures of synthetic triple helices. Critically, our algorithm is compatible with every natural amino acid, can evaluate both homotrimers and heterotrimers, and accounts for all possible helix compositions and registers, including non-canonically staggered helices. We test and optimize our algorithm against 431 published collagen triple helices to demonstrate the quality of our predictive system. Finally, we use this algorithm to successfully guide the design of an ABC heterotrimer possessing high assembly specificity.
We study the stellar, brightest cluster galaxy (BCG) and intracluster medium (ICM) masses of 14 South Pole Telescope (SPT) selected galaxy clusters with median redshift z = 0.9 and mass M
...500 = 6 × 1014 M⊙. We estimate stellar masses for each cluster and BCG using six photometric bands, the ICM mass using X-ray observations and the virial masses using the SPT Sunyaev–Zel'dovich effect signature. At z = 0.9, the BCG mass
$M_{\star }^{\mathrm{BCG}}$
constitutes 0.12 ± 0.01 per cent of the halo mass for a 6 × 1014 M⊙ cluster, and this fraction falls as
$M_{500}^{-0.58\pm 0.07}$
. The cluster stellar mass function has a characteristic mass M
0 = 1011.0 ± 0.1 M⊙, and the number of galaxies per unit mass in clusters is larger than in the field by a factor of 1.65 ± 0.20. We combine our SPT sample with previously published samples at low redshift and correct to a common initial mass function and for systematic virial mass differences. We then explore mass and redshift trends in the stellar fraction f
⋆, the ICM fraction f
ICM, the collapsed baryon fraction f
c and the baryon fraction f
b. At a pivot mass of 6 × 1014 M⊙ and redshift z = 0.9, the characteristic values are f
⋆ = 1.1 ± 0.1 per cent, f
ICM = 9.6 ± 0.5 per cent, f
c = 10.7 ± 1.1 per cent and f
b = 10.7 ± 0.6 per cent. These fractions all vary with cluster mass at high significance, with higher mass clusters having lower f
⋆ and f
c and higher f
ICM and f
b. When accounting for a 15 per cent systematic virial mass uncertainty, there is no statistically significant redshift trend at fixed mass. Our results support the scenario where clusters grow through accretion from subclusters (higher f
⋆, lower f
ICM) and the field (lower f
⋆, higher f
ICM), balancing to keep f
⋆ and f
ICM approximately constant since z ∼ 0.9.
We present a study of the optical properties of the 26 most massive galaxy clusters within the South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) 2500 deg2 survey spanning the redshift range ...0.10 < z < 1.13. We measure the radial profiles, the luminosity functions (LFs), and the halo occupation numbers (HONs) using optical data of typical depth m* + 2. The stacked radial profiles are consistent with a Navarro–Frenk–White profile of concentration
$2.84^{+0.40}_{-0.37}$
for the red sequence (RS) and
$2.36^{+0.38}_{-0.35}$
for the total population. Stacking the data in multiple redshift bins shows slight redshift evolution in the concentration when both the total population is used, and when only RS galaxies are used (at 2.1σ and 2.8σ, respectively). The stacked LF shows a faint end slope
$\alpha = -1.06^{+0.04}_{-0.03}$
for the total and
$\alpha = -0.80^{+0.04}_{-0.03}$
for the RS population. The redshift evolution of m* is consistent with a passively evolving composite stellar population (CSP) model. Adopting the CSP model predictions, we explore the redshift evolution of the Schechter parameters α and ϕ*. We find α for the total population to be consistent with no evolution (0.3σ), and mildly significant evidence of evolution for the red galaxies (1.1–2.1σ). The data show that the density ϕ*/E
2(z) decreases with redshift, in tension with the self-similar expectation at a 2.4σ level for the total population. The measured HON–mass relation has a lower normalization than previous low redshift studies. Finally, our data support HON redshift evolution at a 2.1σ level, with clusters at higher redshift containing fewer galaxies than their low-z counterparts.
We present the detection of very-high-energy gamma-ray emission above 100 TeV from HAWC J2227+610 with the High-Altitude Water Cherenov Gamma-Ray Observatory (HAWC) observatory. Combining our ...observations with previously published results by the Very Energetic Radiation Imaging Telescope Array System (VERTIAS), we interpret the gamma-ray emission from HAWC J2227+610 as emission from protons with a lower limit in their cutoff energy of 800 TeV. The most likely source of the protons is the associated supernova remnant G106.3+2.7, making it a good candidate for a Galactic PeVatron. However, a purely leptonic origin of the observed emission cannot be excluded at this time.
Li-rich antiperovskite (Li
2
Fe)SO with its high specific capacity is an attractive cathode material for Li-ion battery applications. While many battery materials depend on hazardous substances and ...their production is also rarely sustainable, we present an environmentally friendly and sustainable approach for the synthesis of Li-rich (Li
2
Fe)SO using mechanochemistry based on ball milling. This one step process enables preparing a large quantity of phase-pure (Li
2
Fe)SO using low-cost and non-toxic precursors, making it a viable alternative to current solid state synthetic method in terms of simplicity, laboratory safety and scalability. The obtained micro-sized particles are nearly spherical and have a small size distribution. To control the crystallinity and reduce the intrinsic defects of the ball-milled (Li
2
Fe)SO material, a post-heat treatment procedure was tested. Thermodynamic measurements confirmed the high thermal stability of the ball-milled (Li
2
Fe)SO material. Increasing the ball to powder weight ratio was found to be an effective strategy to decrease the milling time required for the synthesis, thus promoting energy saving. Overall, this work provides a practical guide for the green and scalable production of (Li
2
Fe)SO cathode material, as well as a method for particle modification for improved electrochemical properties.
Green and scalable mechanochemical synthesis of antiperovskite (Li
2
Fe)SO cathode.
We present results from daily monitoring of gamma-rays in the energy range from ∼0.5 to ∼100 TeV with the first 17 months of data from the High Altitude Water Cherenkov (HAWC) Observatory. Its wide ...field of view of 2 steradians and duty cycle of % are unique features compared to other TeV observatories that allow us to observe every source that transits over HAWC for up to ∼6 hr each sidereal day. This regular sampling yields unprecedented light curves from unbiased measurements that are independent of seasons or weather conditions. For the Crab Nebula as a reference source, we find no variability in the TeV band. Our main focus is the study of the TeV blazars Markarian (Mrk) 421 and Mrk 501. A spectral fit for Mrk 421 yields a power-law index and an exponential cut-off TeV. For Mrk 501, we find an index and exponential cut-off TeV. The light curves for both sources show clear variability and a Bayesian analysis is applied to identify changes between flux states. The highest per-transit fluxes observed from Mrk 421 exceed the Crab Nebula flux by a factor of approximately five. For Mrk 501, several transits show fluxes in excess of three times the Crab Nebula flux. In a comparison to lower energy gamma-ray and X-ray monitoring data with comparable sampling, we cannot identify clear counterparts for the most significant flaring features observed by HAWC.
We present our study on the spatially resolved H and M* relation for 536 star-forming and 424 quiescent galaxies taken from the MaNGA survey. We show that the star formation rate surface density ( ), ...derived based on the H emissions, is strongly correlated with the M* surface density ( ) on kiloparsec scales for star-forming galaxies and can be directly connected to the global star-forming sequence. This suggests that the global main sequence may be a consequence of a more fundamental relation on small scales. On the other hand, our result suggests that ∼20% of quiescent galaxies in our sample still have star formation activities in the outer region with lower specific star formation rate (SSFR) than typical star-forming galaxies. Meanwhile, we also find a tight correlation between and for LI(N)ER regions, named the resolved "LI(N)ER" sequence, in quiescent galaxies, which is consistent with the scenario that LI(N)ER emissions are primarily powered by the hot, evolved stars as suggested in the literature.
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