Logarithmic Slope Research Articles

Growth and biochemical responses of Skeletonema costatum to petroleum contamination

Clonal populations of the diatom Skeletonema costatum isolated from Lake Pontchartrain (Louisiana, USA) near the 2010 Deepwater Horizon oil release were exposed to uncontaminated f/2 medium or light slop oil emulsified (O-E; 25, 50, 75, 100 % of initial levels) in f/2 during short- (10 day) and long-term (21 day) incubations. During 10-day incubations, inhibition of logarithmic growth slopes occurred in the most severely contaminated populations (75, 100 % O-E f/2). Growth in oil-contaminated populations was reduced during 21-day incubations, and growth rates for all populations converged by ca. day 12. Additionally, total cell lipid contents for populations exposed to uncontaminated and contaminated media differed, and mean values for control populations were ca. 2-fold greater than populations maintained in 100 % O-E f/2 medium. Saturated and unsaturated cellular lipids in uncontaminated populations were greater than in petroleum-contaminated populations. Relative cellular fatty acids abundances and RuBisCO RNA transcript copy numbers, proxies for food storage and cellular stress, and mRNA transcript regulation influencing photosynthesis, respectively, were altered half-way through the long-term incubation; C16:0 and C16:1 fatty acids were greater and less, respectively, and RuBisCO transcript copy numbers were greater within severely contaminated populations (compared to uncontaminated populations). Yet, fatty acid abundances and RuBisCO copy numbers were equivalent among culture populations by the end of the incubation. Oil contaminants within the culture medium were measured; C6–C12 hydrocarbons and arsenic coincided with (initial) growth inhibition and (later) altered cell physiologies, respectively. Relationships among assessed parameters were deemed useful determinants for evaluating phytoplankton inhibition in response to petroleum contamination.

Star formation along the Hubble sequence

The aim of this paper is to characterize the radial structure of the star formation rate (SFR) in galaxies in the nearby Universe as represented by the CALIFA survey. The sample under study contains 416 galaxies observed with IFS, covering a wide range of Hubble types and stellar masses. Spectral synthesis techniques are applied to obtain radial profiles of the intensity of the star formation rate in the recent past, and the local sSFR. To emphasize the behavior of these properties for galaxies that are on and off the main sequence of star formation (MSSF) we stack the individual radial profiles in bins of galaxy morphology and stellar masses. Our main results are: a) The intensity of SFR shows declining profiles that exhibit very little differences between spirals. The dispersion between the profiles is significantly smaller in late type spirals. This confirms that the MSSF is a sequence of galaxies with nearly constant intensity of SFR b) sSFR values scale with Hubble type and increase radially outwards, with a steeper slope in the inner 1 HLR. This behavior suggests that galaxies are quenched inside-out, and that this process is faster in the central, bulge-dominated part than in the disks. c) As a whole, and at all radii, E and S0 are off the MSSF. d) Applying the volume-corrections for the CALIFA sample, we obtain a density of star formation in the local Universe of 0.0105 Msun/yr/Mpc^{-3}. Most of the star formation is occurring in the disks of spirals. e) The volume averaged birthrate parameter, b'=0.39, suggests that the present day Universe is forming stars at 1/3 of its past average rate. E, S0, and the bulge of early type spirals contribute little to the recent SFR of the Universe, which is dominated by the disks of later spirals. f) There is a tight relation between the intensity of the SFR and stellar mass, defining a local MSSF relation with a logarithmic slope of 0.8.

Ubiquity of density slope oscillations in the central regions of galaxy and cluster-sized systems

One usually thinks of a radial density profile as having a monotonically changing logarithmic slope, such as in NFW or Einasto profiles. However, in two different classes of commonly used systems, this is often not the case. These classes exhibit non-monotonic changes in their density profile slopes which we call oscillations for short. We analyze these two unrelated classes separately. Class 1 consists of systems that have density oscillations and that are defined through their distribution function f(E), or differential energy distribution N(E), such as isothermal spheres, King profiles, or DARKexp, a theoretically derived model for relaxed collisionless systems. Systems defined through f(E) or N(E) generally have density slope oscillations. Class 1 system oscillations can be found at small, intermediate, or large radii but we focus on a limited set of Class 1 systems that have oscillations in the central regions, usually at log(r/r−2) ≲ −2, where r−2 is the largest radius where dlog(ρ)/dlog(r) = −2. We show that the shape of their N(E) can roughly predict the amplitude of oscillations. Class 2 systems which are a product of dynamical evolution, consist of observed and simulated galaxies and clusters, and pure dark matter halos. Oscillations in the density profile slope seem pervasive in the central regions of Class 2 systems. We argue that in these systems, slope oscillations are an indication that a system is not fully relaxed. We show that these oscillations can be reproduced by small modifications to N(E) of DARKexp. These affect a small fraction of systems' mass and are confined to log(r/r−2) ≲ 0. The size of these modifications serves as a potential diagnostic for quantifying how far a system is from being relaxed.

Linear relation between H i circular velocity and stellar velocity dispersion in early-type galaxies, and slope of the density profiles

We report a tight linear relation between the HI circular velocity measured at 6 $R_{\rm e}$ and the stellar velocity dispersion measured within 1 $R_{\rm e}$ for a sample of 16 early-type galaxies with stellar mass between $10^{10}$ and $10^{11}$ $\mathrm{M}_\odot$. The key difference from previous studies is that we only use spatially resolved $v_\mathrm{circ}$(HI) measurements obtained at large radius for a sizeable sample of objects. We can therefore link a kinematical tracer of the gravitational potential in the dark-matter dominated outer regions of galaxies with one in the inner regions, where baryons control the distribution of mass. We find that $v_\mathrm{circ}$(HI) = 1.33 $\sigma_\mathrm{e}$ with an observed scatter of just 12 percent. This indicates a strong coupling between luminous and dark matter from the inner- to the outer regions of early-type galaxies, analogous to the situation in spirals and dwarf irregulars. The $v_\mathrm{circ}$(HI)-$\sigma_\mathrm{e}$ relation is shallower than those based on $v_\mathrm{circ}$ measurements obtained from stellar kinematics and modelling at smaller radius, implying that \vcirc\ declines with radius -- as in bulge-dominated spirals. Indeed, the value of $v_\mathrm{circ}$(HI) is typically 25 percent lower than the maximum $v_\mathrm{circ}$ derived at $\sim0.2\ R_\mathrm{e}$ from dynamical models. Under the assumption of power-law total density profiles $\rho \propto r^{-\gamma}$, our data imply an average logarithmic slope $\langle\gamma\rangle=2.18\pm0.03$ across the sample, with a scatter of 0.11 around this value. The average slope and scatter agree with recent results obtained from stellar kinematics alone for a different sample of early-type galaxies.

Comparison of turbulent boundary layers over smooth and rough surfaces up to high Reynolds numbers

Turbulent boundary layer measurements above a smooth wall and sandpaper roughness are presented across a wide range of friction Reynolds numbers, ${\it\delta}_{99}^{+}$, and equivalent sand grain roughness Reynolds numbers, $k_{s}^{+}$ (smooth wall: $2020\leqslant {\it\delta}_{99}^{+}\leqslant 21\,430$, rough wall: $2890\leqslant {\it\delta}_{99}^{+}\leqslant 29\,900$; $22\leqslant k_{s}^{+}\leqslant 155$; and $28\leqslant {\it\delta}_{99}^{+}/k_{s}^{+}\leqslant 199$). For the rough-wall measurements, the mean wall shear stress is determined using a floating element drag balance. All smooth- and rough-wall data exhibit, over an inertial sublayer, regions of logarithmic dependence in the mean velocity and streamwise velocity variance. These logarithmic slopes are apparently the same between smooth and rough walls, indicating similar dynamics are present in this region. The streamwise mean velocity defect and skewness profiles each show convincing collapse in the outer region of the flow, suggesting that Townsend’s (The Structure of Turbulent Shear Flow, vol. 1, 1956, Cambridge University Press.) wall-similarity hypothesis is a good approximation for these statistics even at these finite friction Reynolds numbers. Outer-layer collapse is also observed in the rough-wall streamwise velocity variance, but only for flows with ${\it\delta}_{99}^{+}\gtrsim 14\,000$. At Reynolds numbers lower than this, profile invariance is only apparent when the flow is fully rough. In transitionally rough flows at low ${\it\delta}_{99}^{+}$, the outer region of the inner-normalised streamwise velocity variance indicates a dependence on $k_{s}^{+}$ for the present rough surface.

Sample of cataclysmic variables detected in the 400d X-ray survey

We present a sample of cataclysmic variables (CVs) identified among the X-ray sources from the 400 square degree X-ray survey based on ROSAT pointing data (400d). The procedure of the CV selection among the X-ray sources using additional optical and infrared data from Sloan Digital Sky Survey and WISE survey is described. The results of the optical observations of the selected objects carried out mainly with the Russian-Turkish 1.5-m telescope (RTT-150) and the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (BTA) are presented. Some observations have also been performed with the Sayan Observatory 1.6-m AZT-33IK telescope. Currently we selected eight CVs, four of which were found for the first time in our work. Based on this sample, we have obtained preliminary constraints on the CV X-ray luminosity function in the solar neighborhood in the low luminosity range, L_X ~ 10^29-10^30 erg s^-1 (0.5-2 keV). We show that the logarithmic slope of the CV X-ray luminosity function in this luminosity range is less steep than at L_X > 10^31 erg s^-1. From our CV X-ray luminosity function estimates it follows that few thousand CVs will be detected in theSpectrum-Roentgen-Gamma (SRG) observatory all-sky X-ray survey at high Galactic latitudes, which will allow to obtain much more accurate measurements of CV X-ray luminosity function in the luminosity range L_X < 10^30-10^31 erg s^-1.

Zipf's law from scale-free geometry.

The spatial distribution of people exhibits clustering across a wide range of scales, from household (∼10(-2) km) to continental (∼10(4) km) scales. Empirical data indicate simple power-law scalings for the size distribution of cities (known as Zipf's law) and the population density fluctuations as a function of scale. Using techniques from random field theory and statistical physics, we show that these power laws are fundamentally a consequence of the scale-free spatial clustering of human populations and the fact that humans inhabit a two-dimensional surface. In this sense, the symmetries of scale invariance in two spatial dimensions are intimately connected to urban sociology. We test our theory by empirically measuring the power spectrum of population density fluctuations and show that the logarithmic slope α=2.04 ± 0.09, in excellent agreement with our theoretical prediction α=2. The model enables the analytic computation of many new predictions by importing the mathematical formalism of random fields.

Exploring the connection between stellar halo profiles and accretion histories in L* galaxies

AbstractI use a library of controlled minor merger N-body simulations, a particle tagging technique and Monte Carlo generated ΛCDM accretion histories to study the highly stochastic process of stellar deposition onto the accreted stellar halos (ASHs) of L* galaxies. I explore the main physical mechanisms that drive the connection between the accretion history and the density profile of the ASH. I find that: i) through dynamical friction, more massive satellites are more effective at delivering their stars deeper into the host; ii) as a consequence, ASHs feature a negative gradient between radius and the local mass-weighed virial satellite-to-host mass ratio; iii) in L* galaxies, most ASHs feature a density profile that steepens towards sharper logarithmic slopes at increasing radii, though with significant halo-to-halo scatter; iv) the ASHs with the largest total ex-situ mass are such because of the chance accretion of a small number of massive satellites (rather than of a large number of low-mass ones).

Global distribution of vertical wavenumber spectra in the lower stratosphere observed using high-vertical-resolution temperature profiles from COSMIC GPS radio occultation

Abstract. We retrieved temperature (T) profiles with a high vertical resolution using the full spectrum inversion (FSI) method from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) GPS radio occultation (GPS-RO) data from January 2007 to December 2009. We studied the characteristics of temperature perturbations in the stratosphere at 20–27 km altitude. This height range does not include a sharp jump in the background Brunt–Väisälä frequency squared (N2) near the tropopause, and it was reasonably stable regardless of season and latitude. We analyzed the vertical wavenumber spectra of gravity waves (GWs) with vertical wavelengths ranging from 0.5 to 3.5 km, and we integrated the (total) potential energy EpT. Another integration of the spectra from 0.5 to 1.75 km was defined as EpS for short vertical wavelength GWs, which was not studied with the conventional geometrical optics (GO) retrievals. We also estimated the logarithmic spectral slope (p) for the saturated portion of spectra with a linear regression fitting from 0.5 to 1.75 km.Latitude and time variations in the spectral parameters were investigated in two longitudinal regions: (a) 90–150° E, where the topography was more complicated, and (b) 170–230° E, which is dominated by oceans. We compared EpT, EpS, and p, with the mean zonal winds (U) and outgoing longwave radiation (OLR). We also show a ratio of EpS to EpT and discuss the generation source of EpS. EpT and p clearly showed an annual cycle, with their maximum values in winter at 30–50° N in region (a), and 50–70° N in region (b), which was related to the topography. At 30–50° N in region (b), EpT and p exhibited some irregular variations in addition to an annual cycle. In the Southern Hemisphere, we also found an annual oscillation in EpT and p, but it showed a time lag of about 2 months relative to U. Characteristics of EpTand p in the tropical region seem to be related to convective activity. The ratio of EpT to the theoretical model value, assuming saturated GWs, became larger in the equatorial region and over mountainous regions.

Rupture characteristics of major and great (Mw ≥ 7.0) megathrust earthquakes from 1990 to 2015: 2. Depth dependence

AbstractDepth‐varying characteristics of high‐frequency seismic radiation for megathrust earthquakes have been inferred from several recent giant earthquakes and large tsunami earthquakes. To quantify any depth dependence more extensively, we analyzed 114 Mw ≥ 7.0 thrust‐faulting earthquakes with centroid depths from 5 to 55 km on circum‐Pacific megathrusts using teleseismic body wave finite‐fault inversions and source spectrum determinations. Large tsunami earthquakes and some other shallow events at depths less than about 18 km have unusually long source durations, and low values of static stress drop (ΔσE), Vr3ΔσE, and apparent stress, with relatively depleted high‐frequency radiation. Deeper events have no clear global trend with source depth for moment‐normalized centroid time or total duration, static stress drop, moment‐scaled radiated energy, apparent stress, or radiation efficiency. Regional behavior among the 17 sampled subduction zones generally conforms to the global composite. The source spectra have high‐frequency logarithmic spectral decay slopes averaging ~ −1.6. There is relative enrichment in high‐frequency spectral levels with increasing source depth manifested in reduced high‐frequency spectral decay slope. The ratio of high‐frequency (0.3–1 Hz) radiated energy to total energy increases correspondingly. These observations suggest that overall dynamic rupture processes are relatively insensitive to source depth, but varying scale lengths of megathrust heterogeneity may contribute to modest enrichment of high‐frequency seismic radiation for events deeper on the megathrust. A weak correlation of higher estimated average megathrust temperature at 30 km depth with higher spectral decay rate indicates that the depth‐varying pattern may in part result from frictional properties being influenced by temperature variations or by systematic reduction of average attenuation with increasing depth along the megathrust.

STRUCTURE OF THE ACCRETION DISK IN THE LENSED QUASAR Q2237+0305 FROM MULTI-EPOCH AND MULTI-WAVELENGTH NARROWBAND PHOTOMETRY

ABSTRACT We present estimates for the size and the logarithmic slope of the disk temperature profile of the lensed quasar Q2237+0305, independent of the component velocities. These estimates are based on six epochs of multi-wavelength narrowband images from the Nordic Optical Telescope. For each pair of lensed images and each photometric band, we determine the microlensing amplitude and chromaticity using pre-existing mid-IR photometry to define the baseline for no microlensing magnification. A statistical comparison of the combined microlensing data (6 epochs × 5 narrow bands × 6 image pairs) with simulations based on microlensing magnification maps gives Bayesian estimates for the half-light radius of R 1 / 2 = 8.5 &minus; 4.0 &plus; 7.5 &lang; M &rang; / 0.3 M &CircleDot; ?> lt-day, and p = 0.95 ± 0.33 for the exponent of the logarithmic temperature profile T &prop; R &minus; 1 / p ?> . This size estimate is in good agreement with most recent studies. Other works based on the study of single microlensing events predict smaller sizes, but could be statistically biased by focusing on high-magnification events.

Velocity and doubling time of prostate-specific antigen: mathematics can matter

Changes in prostate-specific antigen (PSA) values are often reported as velocity or doubling time. We compared the association of these two calculations—at the time of PSA failure after primary treatment...

CHANG-ES – VI. Probing Supernova energy deposition in spiral galaxies through multiwavelength relationships

How a galaxy regulates its SNe energy into different interstellar/circumgalactic medium components strongly affects galaxy evolution. Based on the JVLA D-configuration C- (6 GHz) and L-band (1.6 GHz) continuum observations, we perform statistical analysis comparing multi-wavelength properties of the CHANG-ES galaxies. The high-quality JVLA data and edge-on orientation enable us for the first time to include the halo into the energy budget for a complete radio-flux-limited sample. We find tight correlations of $L_{\rm radio}$ with the mid-IR-based SFR. The normalization of our $I_{\rm 1.6GHz}/{\rm W~Hz^{-1}}-{\rm SFR}$ relation is $\sim$2-3 times of those obtained for face-on galaxies, probably a result of enhanced IR extinction at high inclination. We also find tight correlations between $L_{\rm radio}$ and the SNe energy injection rate $\dot{E}_{\rm SN(Ia+CC)}$, indicating the energy loss via synchrotron radio continuum accounts for $\sim0.1\%$ of $\dot{E}_{\rm SN}$, comparable to the energy contained in CR electrons. The integrated C-to-L-band spectral index is $\alpha\sim0.5-1.1$ for non-AGN galaxies, indicating a dominance by the diffuse synchrotron component. The low-scatter $L_{\rm radio}-{\rm SFR}$/$L_{\rm radio}-\dot{E}_{\rm SN (Ia+CC)}$ relationships have super-linear logarithmic slopes at $\sim2~\sigma$ in L-band ($1.132\pm0.067$/$1.175\pm0.102$) while consistent with linear in C-band ($1.057\pm0.075$/$1.100\pm0.123$). The super-linearity could be naturally reproduced with non-calorimeter models for galaxy disks. Using Chandra halo X-ray measurements, we find sub-linear $L_{\rm X}-L_{\rm radio}$ relations. These results indicate that the observed radio halo of a starburst galaxy is close to electron calorimeter, and a galaxy with higher SFR tends to distribute an increased fraction of SNe energy into radio emission (than X-ray).

MATCHING THE DARK MATTER PROFILES OF dSph GALAXIES WITH THOSE OF SIMULATED SATELLITES: A TWO-PARAMETER COMPARISON

We compare the dark matter halos' structural parameters derived for four Milky Way dwarf spheroidal galaxies to those of subhalos found in cosmological $N$-body simulations. We confirm that estimates of the mass at a single fixed radius are fully consistent with the observations. However, when a second structural parameter such as the logarithmic slope of the dark halo density profile measured close to the half-light radius is included in the comparison, we find little to no overlap between the satellites and the subhalos. Typically the right mass subhalos have steeper profiles at these radii than measurements of the dSph suggest. Using energy arguments we explore if it is possible to solve this discrepancy by invoking baryonic effects. Assuming that feedback from supernovae can lead to a reshaping of the halos, we compute the required efficiency and find entirely plausible values for a significant fraction of the subhalos and even as low as 0.1%. This implies that care must be taken not to exaggerate the effect of supernovae feedback as this could make the halos too shallow. These results could be used to calibrate and possibly constrain feedback recipes in hydrodynamical simulations.

Large-Reynolds-number asymptotics of the streamwise normal stress in zero-pressure-gradient turbulent boundary layers

A more poetic long title could be ‘A voyage from the shifting grounds of existing data on zero-pressure-gradient (abbreviated ZPG) turbulent boundary layers (abbreviated TBLs) to infinite Reynolds number’. Aided by the requirement of consistency with the Reynolds-averaged momentum equation, the ‘shifting grounds’ are sufficiently consolidated to allow some firm conclusions on the asymptotic expansion of the streamwise normal stress $\langle uu\rangle ^{+}$, where the $^{+}$ indicates normalization with the friction velocity $u_{{\it\tau}}$ squared. A detailed analysis of direct numerical simulation data very close to the wall reveals that its inner near-wall asymptotic expansion must be of the form $f_{0}(y^{+})-f_{1}(y^{+})/U_{\infty }^{+}+\mathit{O}(U_{\infty }^{+})^{-2}$, where $U_{\infty }^{+}=U_{\infty }/u_{{\it\tau}}$, $y^{+}=yu_{{\it\tau}}/{\it\nu}$ and $f_{0}$, $f_{1}$ are $\mathit{O}(1)$ functions fitted to data in this paper. This means, in particular, that the inner peak of $\langle uu\rangle ^{+}$ does not increase indefinitely as the logarithm of the Reynolds number but reaches a finite limit. The outer expansion of $\langle uu\rangle ^{+}$, on the other hand, is constructed by fitting a large number of data from various sources. This exercise, aided by estimates of turbulence production and dissipation, reveals that the overlap region between inner and outer expansions of $\langle uu\rangle ^{+}$ is its plateau or second maximum, extending to $y_{\mathit{break}}^{+}=\mathit{O}(U_{\infty }^{+})$, where the outer logarithmic decrease towards the boundary layer edge starts. The common part of the two expansions of $\langle uu\rangle ^{+}$, i.e. the height of the plateau or second maximum, is of the form $\,A_{\infty }-B_{\infty }/U_{\infty }^{+}+\cdots \,$with $A_{\infty }$ and $B_{\infty }$ constant. As a consequence, the logarithmic slope of the outer $\langle uu\rangle ^{+}$ cannot be independent of the Reynolds number as suggested by ‘attached eddy’ models but must slowly decrease as $(1/U_{\infty }^{+})$. A speculative explanation is proposed for the puzzling finding that the overlap region of $\langle uu\rangle ^{+}$ is centred near the lower edge of the mean velocity overlap, itself centred at $y^{+}=\mathit{O}(\mathit{Re}_{{\it\delta}_{\ast }}^{1/2})$ with $\mathit{Re}_{{\it\delta}_{\ast }}$ the Reynolds number based on free stream velocity and displacement thickness. Finally, similarities and differences between $\langle uu\rangle ^{+}$ in ZPG TBLs and in pipe flow are briefly discussed.

SHARDS: A GLOBAL VIEW OF THE STAR FORMATION ACTIVITY ATz∼ 0.84 andz∼ 1.23

In this paper, we present a comprehensive analysis of star-forming galaxies (SFGs) at intermediate redshifts (z~1). We combine the ultra-deep optical spectro-photometric data from the Survey for High-z Absorption Red and Dead Sources (SHARDS) with deep UV-to-FIR observations in the GOODS-N field. Exploiting two of the 25 SHARDS medium-band filters, F687W17 and F823W17, we select [OII] emission line galaxies at z~0.84 and z~1.23 and characterize their physical properties. Their rest-frame equivalent widths (EW$_{\mathrm{rf}}$([OII])), line fluxes, luminosities, star formation rates (SFRs) and dust attenuation properties are investigated. The evolution of the EW$_{\mathrm{rf}}$([OII]) closely follows the SFR density evolution of the universe, with a trend of EW$_{\mathrm{rf}}$([OII])$\propto$(1+z)$^3$ up to redshift z~1, followed by a possible flattening. The SF properties of the galaxies selected on the basis of their [OII] emission are compared with complementary samples of SFGs selected by their MIR and FIR emission, and also with a general mass-selected sample of galaxies at the same redshifts. We demonstrate observationally that the UVJ diagram (or, similarly, a cut in the specific SFR) is only partially able to distinguish the quiescent galaxies from the SFGs. The SFR-M$_*$ relation is investigated for the different samples, yelding a logarithmic slope ~1, in good agreement with previous results. The dust attenuations derived from different SFR indicators (UV(1600), UV(2800), [OII], IR) are compared and show clear trends with respect to both the stellar mass and total SFR, with more massive and highly star-forming galaxies being affected by stronger dust attenuation.

DECONSTRUCTING THERMAL SUNYAEV–ZEL’DOVICH—GRAVITATIONAL LENSING CROSS-CORRELATIONS: IMPLICATIONS FOR THE INTRACLUSTER MEDIUM

Recent first detections of the cross-correlation of the thermal Sunyaev-Zel'dovich (tSZ) signal in Planck cosmic microwave background (CMB) temperature maps with gravitational lensing maps inferred from the Planck CMB data and the CFHTLenS galaxy survey provide new probes of the relationship between baryons and dark matter. Using cosmological hydrodynamics simulations, we show that these cross-correlation signals are dominated by contributions from hot gas in the intracluster medium (ICM), rather than diffuse, unbound gas located beyond the virial radius (the "missing baryons"). Thus, these cross-correlations offer a tool with which to study the ICM over a wide range of halo masses and redshifts. In particular, we show that the tSZ - CMB lensing cross-correlation is more sensitive to gas in lower-mass, higher-redshift halos and gas at larger cluster-centric radii than the tSZ - galaxy lensing cross-correlation. Combining these measurements with primary CMB data will constrain feedback models through their signatures in the ICM pressure profile. We forecast the ability of ongoing and future experiments to constrain such ICM parameters, including the mean amplitude of the pressure - mass relation, the redshift evolution of this amplitude, and the mean outer logarithmic slope of the pressure profile. The results are promising, with $\approx 5-20$% precision constraints achievable with upcoming experiments, even after marginalizing over cosmological parameters.

Haloes light and dark: dynamical models of the stellar halo and constraints on the mass of the Galaxy

We develop a flexible set of action-based distribution functions (DFs) for stellar haloes. The DFs have five free parameters, controlling the inner and outer density slope, break radius, flattening and anisotropy respectively. The DFs generate flattened stellar haloes with a rapidly varying logarithmic slope in density, as well as a spherically aligned velocity ellipsoid with a long axis that points towards the Galactic centre - all attributes possessed by the stellar halo of the Milky Way. We use our action-based distribution function to model the blue horizontal branch stars extracted from the Sloan Digital Sky Survey as stellar halo tracers in a spherical Galactic potential. As the selection function is hard to model, we fix the density law from earlier studies and solve for the anisotropy and gravitational potential parameters. Our best fit model has a velocity anisotropy that becomes more radially anisotropic on moving outwards. It changes from $\beta \approx 0.4$ at Galactocentric radius of 15 kpc to $\approx 0.7$ at 60 kpc. This is a gentler increase than is typically found in simulations of stellar haloes built from the mutiple accretion of smaller systems. We find the potential corresponds to an almost flat rotation curve with amplitude of $\approx 200$ kms$^{-1}$ at these distances. This implies an enclosed mass of $\approx 4.5 \times 10^{11} M_\odot$ within a spherical shell of radius 50 kpc.

NON-UNIVERSALITY OF DARK-MATTER HALOS: CUSPS, CORES, AND THE CENTRAL POTENTIAL

Dark-matter halos grown in cosmological simulations appear to have central NFW-like density cusps with mean values of $d\log\rho/d\log r \approx -1$, and some dispersion, which is generally parametrized by the varying index $\alpha$ in the Einasto density profile fitting function. Non-universality in profile shapes is also seen in observed galaxy clusters and possibly dwarf galaxies. Here we show that non-universality, at any given mass scale, is an intrinsic property of DARKexp, a theoretically derived model for collisionless self-gravitating systems. We demonstrate that DARKexp - which has only one shape parameter, $\phi_0$ - fits the dispersion in profile shapes of massive simulated halos as well as observed clusters very well. DARKexp also allows for cored dark-matter profiles, such as those found for dwarf spheroidal galaxies. We provide approximate analytical relations between DARKexp $\phi_0$, Einasto $\alpha$, or the central logarithmic slope in the Dehnen-Tremaine analytical $\gamma$-models. The range in halo parameters reflects a substantial variation in the binding energies per unit mass of dark-matter halos.

Gravitational, lensing, and stability properties of Bose-Einstein condensate dark matter halos

The possibility that dark matter, whose existence is inferred from the study of the galactic rotation curves, and from the mass deficit in galaxy clusters, can be in a form of a Bose-Einstein Condensate, has been extensively investigated lately. In the present work, we consider a detailed analysis of the astrophysical properties of the Bose-Einstein Condensate dark matter halos that could provide clear observational signatures that help discriminate between different dark matter models. In the Bose-Einstein condensation model dark matter can be described as a non-relativistic, gravitationally confined Newtonian gas, whose density and pressure are related by a polytropic equation of state with index $n=1$. The mass and gravitational properties of the condensate halos are obtained in a systematic form, including the mean logarithmic slopes of the density and of the tangential velocity. The lensing properties of the condensate dark matter are investigated in detail. In particular, a general analytical formula for the surface density, an important quantity that defines the lensing properties of a dark matter halos, is obtained in the form of series expansions. This enables arbitrary-precision calculations of the surface mass density, deflection angle, deflection potential, and of the magnification factor, thus giving the possibility of the comparison of the predicted lensing properties of the condensate dark matter halos with observations. The stability properties of the condensate halos are also investigated by using the scalar and the tensor virial theorems, respectively, and the virial perturbation equation for condensate dark matter halos is derived.