Lens Galaxy Properties of SBS1520+530: Insights from Keck Spectroscopy and AO Imaging

We report on an investigation of the SBS 1520+530 gravitational lens system and its environment using archival HST imaging, Keck spectroscopic data, and Keck adaptive-optics imaging. The AO imaging has allowed us to fix the lens galaxy properties with a high degree of precision when performing the lens modeling, and the data indicate that the lens has an elliptical morphology and perhaps a disk. The new spectroscopic data suggest that previous determinations of the lens redshift may be incorrect, and we report an updated, though inconclusive, value z_lens = 0.761. We have also spectroscopically confirmed the existence of several galaxy groups at approximately the redshift of the lens system. We create new models of the lens system that explicitly account for the environment of the lens, and we also include improved constraints on the lensing galaxy from our adaptive-optics imaging. Lens models created with these new data can be well-fit with a steeper than isothermal mass slope (alpha = 2.29, with the density proportional to r^-alpha) if H_0 is fixed at 72 km/s/Mpc; isothermal models require H_0 ~ 50 km/s/Mpc. The steepened profile may indicate that the lens is in a transient perturbed state caused by interactions with a nearby galaxy.Comment: 12 pages, 10 figures, submitted to Ap

ÉTATS A GRAND NOMBRE DE QUASI-PARTICULE DANS LES ISOTOPES PAIRS DE PLOMB

Une étude par distribution spectrale dans les sous-espaces définis par leur nombre de quasi-particules a été effectuée dans les isotopes pairs de plomb. La comparaison avec des résultats obtenus dans les isotopes d'étain montre que le recouvrement entre les différents sous-espaces est fortement lié à l'interaction résiduelle utilisée. En particulier des états à grand nombre de quasi-particules sont présents à basse énergie. Le problème des états spurieux inhérent à cette méthode, qui sont responsables d'une surestimation du couplage, est abordé et différentes corrections sont proposées aussi bien sur les dimensions, les centroïdes et les largeurs des sous-espaces

Inference of the Cold Dark Matter substructure mass function at z=0.2 using strong gravitational lenses

We present the results of a search for galaxy substructures in a sample of 11 gravitational lens galaxies from the Sloan Lens ACS Survey. We find no significant detection of mass clumps, except for a luminous satellite in the system SDSS J0956+5110. We use these non-detections, in combination with a previous detection in the system SDSS J0946+1006, to derive constraints on the substructure mass function in massive early-type host galaxies with an average redshift z ~ 0.2 and an average velocity dispersion of 270 km/s. We perform a Bayesian inference on the substructure mass function, within a median region of about 32 kpc squared around the Einstein radius (~4.2 kpc). We infer a mean projected substructure mass fraction $f = 0.0076^{+0.0208}_{-0.0052}$ at the 68 percent confidence level and a substructure mass function slope $\alpha$ < 2.93 at the 95 percent confidence level for a uniform prior probability density on alpha. For a Gaussian prior based on Cold Dark Matter (CDM) simulations, we infer $f = 0 .0064^{+0.0080}_{-0.0042}$ and a slope of $\alpha$ = 1.90$^{+0.098}_{-0.098}$ at the 68 percent confidence level. Since only one substructure was detected in the full sample, we have little information on the mass function slope, which is therefore poorly constrained (i.e. the Bayes factor shows no positive preference for any of the two models).The inferred fraction is consistent with the expectations from CDM simulations and with inference from flux ratio anomalies at the 68 percent confidence level.Comment: Accepted for publication on MNRAS, some typos corrected and some important references adde

Prospects for GMRT to Observe Radio Waves from UHE Particles Interacting with the Moon

Ultra high energy (UHE) particles of cosmic origin impact the lunar regolith and produce radio signals through Askaryan effect, signals that can be detected by Earth based radio telescopes. We calculate the expected sensitivity for observation of such events at the Giant Metrewave Radio Telescope (GMRT), both for UHE cosmic rays (CR) and UHE neutrino interactions. We find that for 30 days of observation time a significant number of detectable events is expected above $10^{20}$ eV for UHECR or neutrino fluxes close to the current limits. Null detection over a period of 30 days will lower the experimental bounds on UHE particle fluxes by magnitudes competitive to both present and future experiments at the very highest energies.Comment: 21 pages, 9 figure

Global Production Increased by Spatial Heterogeneity in a Population Dynamics Model

Spatial and temporal heterogeneity are often described as important factors having a strong impact on biodiversity. The effect of heterogeneity is in most cases analyzed by the response of biotic interactions such as competition of predation. It may also modify intrinsic population properties such as growth rate. Most of the studies are theoretic since it is often difficult to manipulate spatial heterogeneity in practice. Despite the large number of studies dealing with this topics, it is still difficult to understand how the heterogeneity affects populations dynamics. On the basis of a very simple model, this paper aims to explicitly provide a simple mechanism which can explain why spatial heterogeneity may be a favorable factor for production.We consider a two patch model and a logistic growth is assumed on each patch. A general condition on the migration rates and the local subpopulation growth rates is provided under which the total carrying capacity is higher than the sum of the local carrying capacities, which is not intuitive. As we illustrate, this result is robust under stochastic perturbations

The SWELLS Survey. I. A large spectroscopically selected sample of edge-on late-type lens galaxies

The relative contribution of baryons and dark matter to the inner regions of spiral galaxies provides critical clues to their formation and evolution, but it is generally difficult to determine. For spiral galaxies that are strong gravitational lenses, however, the combination of lensing and kinematic observations can be used to break the disk-halo degeneracy. In turn, such data constrain fundamental parameters such as i) the mass density profile slope and axis ratio of the dark matter halo, and by comparison with dark matter-only numerical simulations the modifications imposed by baryons; ii) the mass in stars and therefore the overall star formation efficiency, and the amount of feedback; iii) by comparison with stellar population synthesis models, the normalization of the stellar initial mass function. In this first paper of a series, we present a sample of 16 secure, 1 probable, and 6 possible strong lensing spiral galaxies, for which multi-band high-resolution images and rotation curves were obtained using the Hubble Space Telescope and Keck-II Telescope as part of the Sloan WFC Edge-on Late-type Lens Survey (SWELLS). The sample includes 8 newly discovered secure systems. [abridged] We find that the SWELLS sample of secure lenses spans a broad range of morphologies (from lenticular to late-type spiral), spectral types (quantified by Halpha emission), and bulge to total stellar mass ratio (0.22-0.85), while being limited to M_*>10^{10.5} M_sun. The SWELLS sample is thus well-suited for exploring the relationship between dark and luminous matter in a broad range of galaxies. We find that the deflector galaxies obey the same size-mass relation as that of a comparison sample of elongated non-lens galaxies selected from the SDSS survey. We conclude that the SWELLS sample is consistent with being representative of the overall population of high-mass high-inclination disky galaxies.Comment: 21 pages, 6 figures, MNRAS, in pres

The fundamental plane of evolving red nuggets

We present an exploration of the mass structure of a sample of 12 strongly lensed massive, compact early-type galaxies at redshifts $z\sim0.6$ to provide further possible evidence for their inside-out growth. We obtain new ESI/Keck spectroscopy and infer the kinematics of both lens and source galaxies, and combine these with existing photometry to construct (a) the fundamental plane (FP) of the source galaxies and (b) physical models for their dark and luminous mass structure. We find their FP to be tilted towards the virial plane relative to the local FP, and attribute this to their unusual compactness, which causes their kinematics to be totally dominated by the stellar mass as opposed to their dark matter; that their FP is nevertheless still inconsistent with the virial plane implies that both the stellar and dark structure of early-type galaxies is non-homologous. We also find the intrinsic scatter of their FP to be comparable to the local value, indicating that variations in the stellar mass structure outweight variations in the dark halo in the central regions of early-type galaxies. Finally, we show that inference on the dark halo structure -- and, in turn, the underlying physics -- is sensitive to assumptions about the stellar initial mass function (IMF), but that physically-motivated assumptions about the IMF imply haloes with sub-NFW inner density slopes, and may present further evidence for the inside-out growth of compact early-type galaxies via minor mergers and accretion.Comment: 10 pages, 3 figures, 3 tables; submitted to MNRA

Noisy Optimization: Convergence with a Fixed Number of Resamplings

It is known that evolution strategies in continuous domains might not converge in the presence of noise. It is also known that, under mild assumptions, and using an increasing number of resamplings, one can mitigate the effect of additive noise and recover convergence. We show new sufficient conditions for the convergence of an evolutionary algorithm with constant number of resamplings; in particular, we get fast rates (log-linear convergence) provided that the variance decreases around the optimum slightly faster than in the so-called multiplicative noise model. Keywords: Noisy optimization, evolutionary algorithm, theory.Comment: EvoStar (2014

Galactic cold dark matter as a Bose-Einstein condensate of WISPs

We propose here the dark matter content of galaxies as a cold bosonic fluid composed of Weakly Interacting Slim Particles (WISPs), represented by spin-0 axion-like particles and spin-1 hidden bosons, thermalized in the Bose-Einstein condensation state and bounded by their self-gravitational potential. We analyze two zero-momentum configurations: the polar phases in which spin alignment of two neighbouring particles is anti-parallel and the ferromagnetic phases in which every particle spin is aligned in the same direction. Using the mean field approximation we derive the Gross-Pitaevskii equations for both cases, and, supposing the dark matter to be a polytropic fluid, we describe the particles density profile as Thomas-Fermi distributions characterized by the halo radii and in terms of the scattering lengths and mass of each particle. By comparing this model with data obtained from 42 spiral galaxies and 19 Low Surface Brightness (LSB) galaxies, we constrain the dark matter particle mass to the range $10^{-6}-10^{-4} eV$ and we find the lower bound for the scattering length to be of the order $10^{-14} fm$.Comment: 13 pages; 6 figures; references added; v.3: typo corrected in the abstract, published in JCA

SHARP -- VII. New constraints on the dark matter free-streaming properties and substructure abundance from gravitationally lensed quasars

We present an analysis of seven strongly gravitationally lensed quasars and the corresponding constraints on the properties of dark matter. Our results are derived by modelling the lensed image positions and flux-ratios using a combination of smooth macro models and a population of low-mass haloes within the mass range 10^6 to 10^9 Msun. Our lens models explicitly include higher-order complexity in the form of stellar discs and luminous satellites, as well as low-mass haloes located along the observed lines of sight for the first time. Assuming a Cold Dark Matter (CDM) cosmology, we infer an average total mass fraction in substructure of f_sub = 0.012^{+0.007}_{-0.004} (68 per cent confidence limits), which is in agreement with the predictions from CDM hydrodynamical simulations to within 1 sigma. This result is closer to the predictions than those from previous studies that did not include line-of-sight haloes. Under the assumption of a thermal relic dark matter model, we derive a lower limit on the particle relic mass of m th > 5.58 keV (95 per cent confidence limits), which is consistent with a value of m_th > 5.3 keV from the recent analysis of the Ly-alpha forest. We also identify two main sources of possible systematic errors and conclude that deeper investigations in the complex structure of lens galaxies as well as the size of the background sources should be a priority for this field.Comment: 14 pages, 7 figures, accepted for publication in MNRA