Two families of graphs that are Cayley on nonisomorphic groups

A number of authors have studied the question of when a graph can be represented as a Cayley graph on more than one nonisomorphic group. The work to date has focussed on a few special situations: when the groups are $p$-groups; when the groups have order $pq$; when the Cayley graphs are normal; or when the groups are both abelian. In this paper, we construct two infinite families of graphs, each of which is Cayley on an abelian group and a nonabelian group. These families include the smallest examples of such graphs that had not appeared in other results.Comment: 6 page

Two families of graphs that are Cayley on nonisomorphic groups

A number of authors have studied the question of when a graph can be represented as a Cayley graph on more than one nonisomorphic group. The work to date has focussed on a few special situations: when the groups are $p$-groups; when the groups have order $pq$; when the Cayley graphs are normal; or when the groups are both abelian. In this paper, we construct two infinite families of graphs, each of which is Cayley on an abelian group and a nonabelian group. These families include the smallest examples of such graphs that had not appeared in other results

The clustering and bias of radio-selected AGN and star-forming galaxies in the COSMOS field

Dark matter haloes in which galaxies reside are likely to have a significant impact on their evolution. We investigate the link between dark matter haloes and their constituent galaxies by measuring the angular two-point correlation function of radio sources, using recently released 3 GHz imaging over $\sim 2 \ \mathrm{deg}^2$of the COSMOS field. We split the radio source population into Star Forming Galaxies (SFGs) and Active Galactic Nuclei (AGN), and further separate the AGN into radiatively efficient and inefficient accreters. Restricting our analysis to$z<1$, we find SFGs have a bias,$b = 1.5 ^{+0.1}_{-0.2}$, at a median redshift of$z=0.62$. On the other hand, AGN are significantly more strongly clustered with$b = 2.1\pm 0.2$at a median redshift of 0.7. This supports the idea that AGN are hosted by more massive haloes than SFGs. We also find low-accretion rate AGN are more clustered ($b = 2.9 \pm 0.3$) than high-accretion rate AGN ($b = 1.8^{+0.4}_{-0.5}$) at the same redshift ($z \sim 0.7$), suggesting that low-accretion rate AGN reside in higher mass haloes. This supports previous evidence that the relatively hot gas that inhabits the most massive haloes is unable to be easily accreted by the central AGN, causing them to be inefficient. We also find evidence that low-accretion rate AGN appear to reside in halo masses of$M_{h} \sim 3-4 \times 10^{13}h^{-1}$M$_{\odot}$at all redshifts. On the other hand, the efficient accreters reside in haloes of$M_{h} \sim 1-2 \times 10^{13}h^{-1}$M$_{\odot}$at low redshift but can reside in relatively lower mass haloes at higher redshifts. This could be due to the increased prevalence of cold gas in lower mass haloes at$z \ge 1$compared to$z<1$.Comment: 20 pages, 10 figures, 1 table, accepted by MNRA

The faint radio population in the VLA-COSMOS Survey: Star forming galaxies and active galactic nuclei

The composition of the faint -- submillijansky -- radio population, that has been a matter of strong debate in the past, is explored by performing observations at 1.4~GHz (20~cm) radio continuum of the 2\sqdeg\ COSMOS field providing a large statistically significant sample, and by developing a method that uses a minimal number of parameters to efficiently discriminate between the two main populations in extragalactic radio surveys: active galactic nuclei (AGN) and star forming galaxies. This method bears the potential to be successfully applied to similar samples selected at other wavelengths. One of the main findings is that star forming galaxies do not dominate the submillijansky radio population, as often assumed, but form only about $30-40\%$ of it, while the remainder is composed of AGN and quasars. Using this well defined sample of radio-selected star forming galaxies at 1.4~GHz, the cosmic star formation history is derived using radio data, for the first time constraining the dust-unbiased cosmic evolution of star formation rate in the most intensively star forming galaxies ($\gtrsim100$~\Msolyr) since $\sim5$~Gyr after the Big Bang with high precision. In addition, the radio derived cosmic star formation history confirms the validity of the large dust corrections applied at other wavelengths

Algorithms for Analytic Combinatorics in Several Variables

Given a multivariate rational generating function we are interested in computing asymptotic formulas for the sequences encoded by the coefficients. In this thesis we apply the theory of analytic combinatorics in several variables (ACSV) to this problem and build algorithms which seek to compute asymptotic formulas automatically, and to aid in understanding of the theory. Under certain assumptions on a given rational multivariate generating series, we demonstrate two algorithms which compute an asymptotic formula for the coefficients. The first algorithm applies numerical methods for polynomial system solving to compute minimal points which are essential to asymptotics, while the second algorithm leverages the geometry of a so-called height map in two variables to compute asymptotics even in the absence of minimal points. We also provide software for computing gradient flows on the height maps of rational generating functions. These flows are useful for understanding the deformations of integral contours which are present in the analysis of rational generating functions

Extended X-ray emission from non-thermal sources in the COSMOS field: A detailed study of a large radio galaxy at z=1.168

X-ray selected galaxy group samples are usually generated by searching for extended X- ray sources that reflect the thermal radiation of the intragroup medium. On the other hand, large radio galaxies that regularly occupy galaxy groups also emit in the X-ray window, and their contribution to X-ray selected group samples is still not well understood. In order to investigate their relative importance, we have carried out a systematic search for non-thermal extended X-ray sources in the COSMOS field. Based on the morphological coincidence of X-ray and radio extensions, out of 60 radio galaxies, and \sim 300 extended X-ray sources, we find only one candidate where the observed extended X-ray emission arises from non- thermal processes related to radio galaxies. We present a detailed analysis of this source, and its environment. Our results yield that external Inverse Compton emission of the lobes is the dominant process that generates the observed X-ray emission of our extended X-ray candidate, with a minor contribution from the gas of the galaxy group hosting the radio galaxy. Finally, we show that finding only one potential candidate in the COSMOS field (in a redshift range 0 < z < 6 and with radio luminosity between 1025 and 1030 W/Hz) is consistent with expected X-ray-counts arising from synchrotron lobes. This implies that these sources are not a prominent source of contamination in samples of X-ray selected clusters/groups, but they could potentially dominate the z > 1 cluster counts at the bright end (S_X > 7 \cdot 10^-15 erg s^-1 cm^2).Comment: 11 pages, 10 figures, 2 tables, accepted for publication in MNRA

Validation of methods performance for routine biochemistry analytes at Cobas 6000 analyzer series module c501

Introduction: Cobas 6000 (Roche, Germany) is biochemistry analyzer for spectrophotometric, immu-noturbidimetric and ion-selective determination of biochemical analytes. Hereby we present analytical validation with emphasis on method performance judgment for routine operation. Materials and methods: Validation was made for 30 analytes (metabolites, enzymes, trace ele-ments, specific proteins and electrolytes). Research included determination of within-run (N = 20) and between-run imprecision (N = 30), inaccuracy (N = 30) and method comparison with routine analyzer (Beckman Coulter AU640) (N = 50). For validation of complete analytical process we calculated total error (TE). Results were judged according to quality specification criteria given by European Working Group. Results: Within-run imprecision CVs were all below 5% except for cholesterol, triglycerides, IgA and IgM. Between-run CVs for all analytes were below 10%. Analytes that did not meet the required speci-fications for imprecision were: total protein, albumin, calcium, sodium, chloride, immunoglobulins and HDL cholesterol. Analytes that did not fulfill requirements for inaccuracy were: total protein, calcium, sodium and chloride. Analytes that deviated from quality specifications for total error were: total pro-tein, albumin, calcium, sodium, chloride and IgM. Passing-Bablok regression analysis provided linear equation and 95% confidence interval for intercept and slope. Complete accordance with routine ana-lyzer Beckman Coulter AU640 showed small number of analytes. Other analytes showed small pro-portional and/or small constant difference and therefore need to be adjusted for routine operation. Conclusions: Regarding low CV values, tested analyzer has satisfactory accuracy and precision and is extremely stable. Except for analytes that are coherent on both analyzers, some analytes require adjustments of slope and intercept for complete accordance

Exploring AGN Activity over Cosmic Time with the SKA

In this Chapter we present the motivation for undertaking both a wide and deep survey with the SKA in the context of studying AGN activity across cosmic time. With an rms down to 1 $\mu$Jy/beam at 1 GHz over 1,000 - 5,000 deg$^2$ in 1 year (wide tier band 1/2) and an rms down to 200 nJy/beam over 10 - 30 deg$^2$ in 2000 hours (deep tier band 1/2), these surveys will directly detect faint radio-loud and radio-quiet AGN (down to a 1 GHz radio luminosity of about $2\times10^{23}$ W/Hz at $z=6$). For the first time, this will enable us to conduct detailed studies of the cosmic evolution of radio AGN activity to the cosmic dawn ($z\gtrsim6$), covering all environmental densities.Comment: 17 pages, 7 figures, to appear as part of 'Continuum Science' in Proceedings 'Advancing Astrophysics with the SKA (AASKA14)

Extragalactic Very-High-Energy gamma-ray background

We study the origin of the extragalactic diffuse gamma-ray background using the data from the Fermi telescope. To estimate the background level, we count photons at high Galactic latitudes |b|>60 degrees. Subtracting photons associated to known sources and the residual cosmic ray and Galactic diffuse backgrounds, we estimate the Extragalactic Gamma-ray Background (EGB) flux. We find that the spectrum of EGB in the very-high-energy (VHE) band above 30 GeV follows the stacked spectrum of BL Lacs. LAT data reveal the positive (1+z)^k, 1<k<4 cosmological evolution of the BL Lac source population consistent with that of their parent population, FR I radio galaxies. We show that EGB at E>30 GeV could be completely explained by emission from unresolved BL Lacs if k~3.Comment: 8 pages, 6 figures, accepted to Astrophysics Journa

ALMA Imaging of Gas and Dust in a Galaxy Protocluster at Redshift 5.3: [CII] Emission in "Typical" Galaxies and Dusty Starbursts ~1 Billion Years after the Big Bang

We report interferometric imaging of [CII] and OH emission toward the center of the galaxy protocluster associated with the z=5.3 submillimeter galaxy (SMG) AzTEC-3, using the Atacama Large (sub)Millimeter Array (ALMA). We detect strong [CII], OH, and rest-frame 157.7 um continuum emission toward the SMG. The [CII] emission is distributed over a scale of 3.9 kpc, implying a dynamical mass of 9.7 x 10^10 Msun, and a star formation rate (SFR) surface density of Sigma_SFR = 530 Msun/yr/kpc2. This suggests that AzTEC-3 forms stars at Sigma_SFR approaching the Eddington limit for radiation pressure supported disks. We find that the OH emission is slightly blueshifted relative to the [CII] line, which may indicate a molecular outflow associated with the peak phase of the starburst. We also detect and dynamically resolve [CII] emission over a scale of 7.5 kpc toward a triplet of Lyman-break galaxies with moderate UV-based SFRs in the protocluster at ~95kpc projected distance from the SMG. These galaxies are not detected in the continuum, suggesting far-infrared SFRs of <18-54 Msun/yr, consistent with a UV-based estimate of 22 Msun/yr. The spectral energy distribution of these galaxies is inconsistent with nearby spiral and starburst galaxies, but resembles those of dwarf galaxies. This is consistent with expectations for young starbursts without significant older stellar populations. This suggests that these galaxies are significantly metal-enriched, but not heavily dust-obscured, "normal" star-forming galaxies at z>5, showing that ALMA can detect the interstellar medium in "typical" galaxies in the very early universe.Comment: 15 pages, 12 figures, 4 tables, to appear in ApJ (accepted October 15, 2014