Rm DM Research Articles

Four phases of angular-momentum buildup in high-z galaxies: from cosmic-web streams through an extended ring to disc and bulge

We study the angular-momentum (AM) buildup in high-$z$ massive galaxies using high-resolution cosmological simulations. The AM originates in co-planar streams of cold gas and merging galaxies tracing cosmic-web filaments, and it undergoes four phases of evolution. (I) Outside the halo virial radius ($R_{\rm v}\!\sim\!100\,{\rm kpc}$), the elongated streams gain AM by tidal torques with a specific AM (sAM) $\sim\!1.7$ times the dark-matter (DM) spin due to the gas' higher quadrupole moment. This AM is expressed as stream impact parameters, from $\sim\!0.3R_{\rm v}$ to counter rotation. (II) In the outer halo, while the incoming DM mixes with the existing halo of lower sAM to a spin $\lambda_{\rm dm}\!\sim\!0.04$, the cold streams transport the AM to the inner halo such that their spin in the halo is $\sim\!3\lambda_{\rm dm}$. (III) Near pericenter, the streams dissipate into an irregular rotating ring extending to $\sim\!0.3R_{\rm v}$ and tilted relative to the inner disc. Torques exerted partly by the disc make the ring gas lose AM, spiral in, and settle into the disc within one orbit. The ring is observable with 30\% probability as a damped Lyman-$\alpha$ absorber. (IV) Within the disc, $<\!0.1R_{\rm v}$, torques associated with violent disc instability drive AM out and baryons into a central bulge, while outflows remove low-spin gas, introducing certain sensitivity to feedback strength. Despite the different AM histories of gas and DM, the disc spin is comparable to the DM-halo spin. Counter rotation can strongly affect disc evolution.

Dark matter–dark energy interaction for a time-dependent EoS parameter

In this work we investigate the interaction between dark matter and dark energy for a coupling that obeys the Wang-Meng decaying law, $\rho_{{\rm DM}}\propto (1+z)^{3-\epsilon}$, and the Barboza-Alcaniz dark energy parametric model, $w=w_0+w'_0z(1+z)/(1+z^2)$. Theoretically, we show that the coupling constant, $\epsilon$, should satisfy the physical constraint $\epsilon\ge0$. We use the most recent data of type Ia supernovae, baryon acoustic oscillations, cosmic microwave background and the Hubble expansion rate function to constrain the free parameters of the model. From a purely observational point of view, we show that is not possible to discard values of the coupling constant in the unphysical region $\epsilon<0$. We show that the uncoupled case, $\epsilon=0$, is in better agreement with the data than any of coupled models in the physical region. We also find that all physically acceptable interaction in dark sector lies in the narrow range $0<\epsilon\le0.034$ ($95\%$ CL).

DISCOVERY OF A STRONG LENSING GALAXY EMBEDDED IN A CLUSTER AT z = 1.62

We identify a strong lensing galaxy in the cluster IRC 0218 (also known as XMM-LSS J02182$-$05102) that is spectroscopically confirmed to be at $z=1.62$, making it the highest-redshift strong lens galaxy known. The lens is one of the two brightest cluster galaxies and lenses a background source galaxy into an arc and a counterimage. With Hubble Space Telescope (HST) grism and Keck/LRIS spectroscopy, we measure the source redshift to be $z_{\rm S}=2.26$. Using HST imaging in ACS/F475W, ACS/F814W, WFC3/F125W, and WFC3/F160W, we model the lens mass distribution with an elliptical power-law profile and account for the effects of the cluster halo and nearby galaxies. The Einstein radius is $\theta_{\rm E}=0.38^{+0.02}_{-0.01}$" ($3.2_{-0.1}^{+0.2}$ kpc) and the total enclosed mass is M$_{\rm tot} (< \theta_{\rm E})=1.8^{+0.2}_{-0.1}\times10^{11}~{\rm M}_{\odot}$. We estimate that the cluster environment contributes $\sim10$% of this total mass. Assuming a Chabrier IMF, the dark matter fraction within $\theta_{{\rm E}}$ is $f_{\rm DM}^{{\rm Chab}} = 0.3_{-0.3}^{+0.1}$, while a Salpeter IMF is marginally inconsistent with the enclosed mass ($f_{\rm DM}^{{\rm Salp}} = -0.3_{-0.5}^{+0.2}$). The total magnification of the source is $\mu_{\rm tot}=2.1_{-0.3}^{+0.4}$. The source has at least one bright compact region offset from the source center. Emission from Ly$\alpha$ and [O III] are likely to probe different regions in the source.

NEW NEUTRINO MASS BOUNDS FROM SDSS-III DATA RELEASE 8 PHOTOMETRIC LUMINOUS GALAXIES

We present neutrino mass bounds using 900,000 luminous galaxies with photometric redshifts measured from Sloan Digital Sky Survey III Data Release Eight (SDSS DR8). The galaxies have photometric redshifts between $z = 0.45$ and $z = 0.65$, and cover 10,000 square degrees and thus probe a volume of 3$h^{-3}$Gpc$^3$, enabling tight constraints to be derived on the amount of dark matter in the form of massive neutrinos. A new bound on the sum of neutrino masses $\sum m_\nu < 0.26$ eV, at 95% confidence level (CL), is obtained after combining our sample of galaxies, which we call "CMASS", with WMAP 7 year Cosmic Microwave Background (CMB) data and the most recent measurement of the Hubble parameter from the Hubble Space Telescope (HST). This constraint is obtained with a conservative multipole range choice of $30 < \ell < 200$ in order to minimize non-linearities, and a free bias parameter in each of the four redshift bins. We study the impact of assuming this linear galaxy bias model using mock catalogs, and find that this model causes a small ($\sim 1-1.5 \sigma$) bias in $\Omega_{\rm DM} h^2$. For this reason, we also quote neutrino bounds based on a conservative galaxy bias model containing additional, shot noise-like free parameters. In this conservative case, the bounds are significantly weakened, e.g. $\sum m_\nu < 0.36$ eV (95% confidence level) for WMAP+HST+CMASS ($\ell_{\rm max}=200$). We also study the dependence of the neutrino bound on multipole range ($\ell_{\rm max}=150$ vs $\ell_{\rm max}=200$) and on which combination of data sets is included as a prior. The addition of supernova and/or Baryon Acoustic Oscillation data does not significantly improve the neutrino mass bound once the HST prior is included. [abridged]

MODELING OF THE HERMES SUBMILLIMETER SOURCE LENSED BY A DARK MATTER DOMINATED FOREGROUND GROUP OF GALAXIES

We present the results of a gravitational lensing analysis of the bright $\zs=2.957$ sub-millimeter galaxy (SMG), HERMES J105751.1+573027 found in {\it Herschel}/SPIRE Science Demonstration Phase data from the Herschel Multi-tiered Extragalactic Survey (HerMES) project. The high resolution imaging available in optical and Near-IR channels, along with CO emission obtained with the Plateau de Bure Interferometer, allow us to precisely estimate the intrinsic source extension and hence estimate the total lensing magnification to be $\mu=10.9\pm 0.7$. We measure the half-light radius $R_{\rm eff}$ of the source in the rest-frame Near-UV and $V$ bands that characterize the unobscured light coming from stars and find $R_{\rm eff,*}= [2.0 \pm 0.1]$ kpc, in good agreement with recent studies on the Submillimeter Galaxy population. This lens model is also used to estimate the size of the gas distribution ($R_{\rm eff,gas}= [1.1\pm0.5]$) kpc by mapping back in the source plane the CO (J=5-4) transition line emission. The lens modeling yields a relatively large Einstein radius $R_{\rm Ein}= 4\farcs10 \pm 0\farcs02$, corresponding to a deflector velocity dispersion of [$483\pm 16] \,\kms$. This shows that HERMES J105751.1+573027 is lensed by a {\it galaxy group-size} dark matter halo at redshift $\zl\sim 0.6$. The projected dark matter contribution largely dominates the mass budget within the Einstein radius with $f_{\rm dm}(<R_{\rm Ein})\sim 80%$. This fraction reduces to $f_{\rm dm}(<R_{\rm eff,G1}\simeq 4.5\kpc)\sim 47%$ within the effective radius of the main deflecting galaxy of stellar mass $M_{\rm *,G1}=[8.5\pm 1.6] \times 10^{11}\msun$. At this smaller scale the dark matter fraction is consistent with results already found for massive lensing ellipticals at $z\sim0.2$ from the SLACS survey.

Scientific Opinion on the substantiation of health claims related to lutein and maintenance of vision (ID 1603, 1604, 1931) pursuant to Article 13(1) of Regulation (EC) No 1924/2006

Scientific Opinion on the substantiation of health claims related to lutein and maintenance of vision (ID 1603, 1604, 1931) pursuant to Article 13(1) of Regulation (EC) No 1924/2006

Kinetics and Equilibria for Complex Formation between Palladium(II) and Chloroacetate

Kinetics and equilibria for the formation of a 1:1 complex between palladium(II) and chloroacetate were studied by spectrophotometric measurements in 1.00 mol\(\cdot {\rm dm}^{-3}\) HClO4 at 298.2 K. The equilibrium constant, K, of the reaction $$ {\rm Pd}^{2 + } + {\rm HL}^{K} {\rm PdL}^+ +{\rm H}^+ $$ was determined from multi-wavelength absorbance measurements of equilibrated solutions at variable temperatures as log\(_{10} \, K (298.2\,K) = 0.492 \pm \) 0.006 with \(\Delta H^{\circ}=-15.{6}\pm 1.{9} \,{\rm kJ} \cdot {\rm mol}^{-1}\) and \(\Delta^{\circ}=-43.{0}\pm 6.{3} {\rm J} \cdot {\rm K}^{-1} \cdot {\rm mol}^{-1}\), and spectra of individual species were calculated. Variable-temperature kinetic measurements gave rate constants for the forward and backward reactions at 298.2 K and ionic strength 1.00 mol\( \cdot\,{\rm dm}^{-3}\) as \(k_{1}=6.46\pm 0.08 {\rm dm}^{3} \cdot {\rm mol}^{-1} \cdot {\rm s}^{-1}\) and \(k_{-1}=2.91\pm 0.03 {\rm s}^{-1}\), with activation parameters \(\smash{\Delta H_1^{\ne} = 56.55 \pm 0.75 } {\rm kJ} \cdot {\rm mol}^{-1}, \smash{\Delta S_1^{\ne} = - 40.0 \pm 2.5} {\rm J}\cdot {\rm K}^{-1} \cdot {\rm mol}^{-1}, \smash{\Delta H_{ - 1}^{\ne} = 64.42 \pm 0.50 } {\rm kJ} \cdot {\rm mol}^{-1}\) and \(\smash{\Delta S_{ - 1}^{\ne} = - 20.3 \pm 1.7} {\rm J} \cdot {\rm K}^{-1} \cdot {\rm mol}^{-1}\), respectively. From the kinetics of the forward and reverse processes, \(\log _{10} \,K = 0.346 \pm 0.007, \Delta H^{\circ}=-7.9\pm 0.9 {\rm kJ} \cdot {\rm mol}^{-1}\) and \(\Delta^{\circ}=-19.{8}\pm 3.{0} {\rm J}\cdot {\rm K}^{-1} \cdot {\rm mol}^{-1}\) were derived in good agreement with the results of the equilibrium measurements. Specific Ion Interaction Theory was employed for determination of thermodynamic equilibrium constants for the protonation of chloroacetate (\(\log _{10} \,K^\circ _ {\rm p} = 2.857 \pm 0.016 \)) and formation of the PdL+ complex (\(\log _{10} K^\circ = 1.002 \pm 0.046, \log _{10} \beta^\circ = 3.859 \pm 0.048\)). Specific ion interaction coefficients \(\varepsilon({\rm L}^{-},{\rm Na}^{+})=0.04{2}\pm 0.02{2} {\rm kg}\cdot {\rm mol}^{-1}, \varepsilon({\rm L}^{-},{\rm K}^{+})=0.08{1}\pm 0.02{1} {\rm kg}\cdot {\rm mol}^{-1}, \varepsilon ({\rm PdL}^+ ,{\rm ClO}_4^-) = 0.92 \pm 0.21 {\rm kg}\cdot {\rm mol}^{-1}\) were derived.

The role of nitric oxide in mitochondria. Focus on “Modulation of mitochondrial Ca2+ by nitric oxide in cultured bovine vascular endothelial cells”

nitric oxide (NO) plays an important role in intracellular signaling, and stole the limelight in 1992 by winning science's equivalent of an “Oscar”: Science magazine's “Molecule of the Year.” Subsequently, the importance and versatility of its known roles has expanded. Furthermore, this

Can the clustered dark matter and the smooth dark energy arise from the same scalar field?

Cosmological observations suggest the existence of two different kinds of energy densities dominating at small ($ \lesssim 500$ Mpc) and large ($\gtrsim 1000 $ Mpc) scales. The dark matter component, which dominates at small scales, contributes $\Omega_m \approx 0.35$ and has an equation of state $p=0$ while the dark energy component, which dominates at large scales, contributes $\Omega_V \approx 0.65$ and has an equation of state $p\simeq -\rho$. It is usual to postulate wimps for the first component and some form of scalar field or cosmological constant for the second component. We explore the possibility of a scalar field with a Lagrangian $L =- V(\phi) \sqrt{1 - \del^i \phi \del_i \phi}$ acting as {\it both} clustered dark matter and smoother dark energy and having a scale dependent equation of state. This model predicts a relation between the ratio $ r = \rho_V/\rho_{\rm DM}$ of the energy densities of the two dark components and expansion rate $n$ of the universe (with $a(t) \propto t^n$) in the form $n = (2/3) (1+r) $. For $r \approx 2$, we get $n \approx 2$ which is consistent with observations.

Dynamics of ternary complex formation in the reaction of diaquoanthranilato-N, N-diacetatonickelate(II) with 2,2?-bipyridine and 1,10-phenanthroline

Dynamics of ternary complex formation in the reaction of diaquoanthranilato-N, N-diacetatonickelate(II) with 2,2′-bipyridine and 1,10-phenanthroline. $\rm Ni(ada)(H_2O)_2^{-}$ $+$ $L\rightleftharpoons Ni(ada)(L)^{-}$ $+$ $2 H_20;$ $- {{d[Ni(ada)^{-}]}\over{dt}}$ $=$ $k_f[Ni(ada)^{-}][L]+k_d\ [Ni(ada)(L)];$ $\ ada^{3-}=$anthranilate-N, N-diacetate; and L=bipy or phen. The kinetics of formation of ternary complexes by diaquoanthranilato-N, N-diacetatonickelate(II). [Ni(ada)(H2O)]− with 2,2′-bipyridine (bipy) and 1,10-phenanthroline (phen) have been studied under pseudo-first-order conditions containing excess bipy or phen by stopped-flow spectrophotometry in the pH range 7.1–7.8 at 25°C and λ = 0.1 mol dm−3. In each case, the reaction is first-order with respect to both Ni(ada)− and the entering ligand (ie., bipy, phen). The reactions are reversible. The forward rate constants are: $k^{\rm Ni(ada)}_{\rm Ni(ada)(bipy)}=0.87\times10^3{\rm dm}^3 {\rm mol}^{-1}{\rm s}^{-1}$,. $k^{\rm Ni(ada)}_{\rm Ni(ada)(phen)}=1.87\times10^3{\rm dm}^3 {\rm mol}^{-1}{\rm s}^{-1}$; and the reverse rate constants are: $k^{\rm Ni(ada)(bipy)}_{\rm Ni(ada)}=1.0{\rm s}^{-1}$ and $k^{\rm Ni(ada)(phen)}_{\rm Ni(ada)}=2.0{\rm s}^{-1}$. The corresponding stability constants of ternary complex formation are: and , . The observed rate constants and huge drops in stability constants in ternary complex formation agree well with the mechanism in which dissociation of an acetate arm of the coordinated ada3− prior to chelation by the aromatic ligand occurs. The observations have been compared with the kinetics of ternary complex formation in the reaction Ni(ada)− - glycine in which the kinetics involves a singly bonded intermediate, N(ada)((SINGLE BOND)O(SINGLE BOND)N)2− in rapid equilibrium with the reactants followed by a sluggish ring closure step. The reaction with the aromatic ligands conforms to a steady-state mechanism, while for glycine it gets shifted to an equilibrium mechanism. The cause of this difference in mechanistic pathways has been explained. © 1996 John Wiley & Sons, Inc.