Following a number of conflicting studies of M87's mass profile, we undertake a dynamical analysis of multiple tracer populations to constrain its mass over a large radius range. We combine stellar ...kinematics in the central regions with the dynamics of 612 globular clusters out to 200 kpc and satellite galaxies extending to scales comparable with the virial radius. Using a spherical Jeans analysis, we are able to disentangle the mass contributions from the dark and baryonic components and set constraints on the structure of each. Assuming isotropy, we explore four different models for the dark matter halo and find that a centrally cored dark matter distribution is preferred. We infer a stellar mass-to-light ratio ϒ⋆, v
= 6.9 ± 0.1 – consistent with a Salpeter-like initial mass function (IMF) – and a core radius r
c
= 67 ± 20 kpc. We then introduce anisotropy and find that, while the halo remains clearly cored, the radial stellar anisotropy has a strong impact on both ϒ⋆, v
and the core's radius; here we find
$\Upsilon _{\star ,v} = 3.50_{-0.36}^{+0.32}$
– consistent with a Chabrier-like IMF – and
$r_c = 19.00_{-8.34}^{+8.38}$
kpc. Thus, the presence of a core at the centre of the dark halo is robust against anisotropy assumptions, while the stellar mass and core size are not. We are able to reconcile previously discrepant studies by showing that modelling the globular cluster data alone leads to the very different inference of a super-NFW cusp, thus highlighting the value of multiple-population modelling, and we point to the possible role of M87's AGN and the cluster environment in forming the central dark matter core.
Movement responses to environment Jonsen, I. D.; McMahon, C. R.; Patterson, T. A. ...
Ecology (Durham),
01/2019, Letnik:
100, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Like many species, movement patterns of southern elephant seals (Mirounga leonina) are being influenced by long-term environmental change. These seals migrate up to 4,000 km from their breeding ...colonies, foraging for months in a variety of Southern Ocean habitats. Understanding how movement patterns vary with environmental features and how these relationships differ among individuals employing different foraging strategies can provide insight into foraging performance at a population level. We apply new fast-estimation tools to fit mixed effects within a random walk movement model, rapidly inferring among-individual variability in southern elephant seal environment–movement relationships. We found that seals making foraging trips to the sea ice on or near the Antarctic continental shelf consistently reduced speed and directionality (move persistence) with increasing sea-ice coverage but had variable responses to chlorophyll a concentration, whereas seals foraging in the open ocean reduced move persistence in regions where circumpolar deep water shoaled. Given future climate scenarios, open-ocean foragers may encounter more productive habitat but sea-ice foragers may see reduced habitat availability. Our approach is scalable to large telemetry data sets and allows flexible combinations of mixed effects to be evaluated via model selection, thereby illuminating the ecological context of animal movements that underlie habitat usage.
We present the results of a search for galaxy substructures in a sample of 11 gravitational lens galaxies from the Sloan Lens ACS Survey by Bolton et al. 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
lens〉 ∼ 0.2 and an average velocity dispersion 〈σeff〉 ∼ 270 km s−1. We perform a Bayesian inference on the substructure mass function, within a median region of about 32 kpc2 around the Einstein radius (〈R
ein〉 ∼ 4.2 kpc). We infer a mean projected substructure mass fraction f =
$0.0076_{-0.0052}^{+0.0208}$
at the 68 per cent confidence level and a substructure mass function slope α < 2.93 at the 95 per cent confidence level for a uniform prior probability density on α. For a Gaussian prior based on cold dark matter (CDM) simulations, we infer f =
$0.0064^{+0.0080}_{-0.0042}$
and a slope of α =
$1.90^{+0.098}_{-0.098}$
at the 68 per cent 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 per cent confidence level.
The mass function of dwarf satellite galaxies that are observed around Local Group galaxies differs substantially from simulations based on cold dark matter: the simulations predict many more dwarf ...galaxies than are seen. The Local Group, however, may be anomalous in this regard. A massive dark satellite in an early-type lens galaxy at a redshift of 0.222 was recently found using a method based on gravitational lensing, suggesting that the mass fraction contained in substructure could be higher than is predicted from simulations. The lack of very low-mass detections, however, prohibited any constraint on their mass function. Here we report the presence of a (1.9 ± 0.1) × 10(8) M dark satellite galaxy in the Einstein ring system JVAS B1938+666 (ref. 11) at a redshift of 0.881, where M denotes the solar mass. This satellite galaxy has a mass similar to that of the Sagittarius galaxy, which is a satellite of the Milky Way. We determine the logarithmic slope of the mass function for substructure beyond the local Universe to be 1.1(+0.6)(-0.4), with an average mass fraction of 3.3(+3.6)(-1.8) per cent, by combining data on both of these recently discovered galaxies. Our results are consistent with the predictions from cold dark matter simulations at the 95 per cent confidence level, and therefore agree with the view that galaxies formed hierarchically in a Universe composed of cold dark matter.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
ABSTRACT
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 of 106–109 M⊙. 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 $f_{\rm sub} = 0.012^{+0.007}_{-0.004}$ (68 per cent confidence limits), which is in agreement with the predictions from CDM hydrodynamical simulations to within 1σ. 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 mth > 5.58 keV (95 per cent confidence limits), which is consistent with a value of mth > 5.3 keV from the recent analysis of the Ly α 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.
Abstract
We present a blind time-delay strong lensing (TDSL) cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 . We combine the relative time delay between the quasar images, Hubble ...Space Telescope imaging, the Keck stellar velocity dispersion of the lensing galaxy, and wide-field photometric and spectroscopic data of the field to constrain two angular diameter distance relations. The combined analysis is performed by forward modelling the individual data sets through a Bayesian hierarchical framework, and it is kept blind until the very end to prevent experimenter bias. After unblinding, the inferred distances imply a Hubble constant H0 = 68.8$^{+5.4}_{-5.1}$ km s−1 Mpc−1, assuming a flat Λ cold dark matter cosmology with uniform prior on Ωm in 0.05, 0.5. The precision of our cosmographic measurement with the doubly imaged quasar SDSS 1206+4332 is comparable with those of quadruply imaged quasars and opens the path to perform on selected doubles the same analysis as anticipated for quads. Our analysis is based on a completely independent lensing code than our previous three H0LiCOW systems and the new measurement is fully consistent with those. We provide the analysis scripts paired with the publicly available software to facilitate independent analysis (footnote with link to www.h0licow.org). The consistency between blind measurements with independent codes provides an important sanity check on lens modelling systematics. By combining the likelihoods of the four systems under the same prior, we obtain H0 = 72.5$^{+2.1}_{-2.3}$ km s−1 Mpc−1. This measurement is independent of the distance ladder and other cosmological probes.
Strong gravitational lenses can be used to detect low-mass subhaloes, based on deviations in image fluxes and positions from what can be achieved with a smooth mass distribution. So far, this method ...has been limited by the small number of (radio-loud, microlensing-free) systems which can be analysed for the presence of substructure. Using the gravitational lens B1422+231, we demonstrate that adaptive optics integral field spectroscopy can also be used to detect dark substructures. We analyse data obtained with OH Suppressing Infra-Red Imaging Spectrograph on the Keck i Telescope, using a Bayesian method that accounts for uncertainties relating to the point spread function and image positions in the separate exposures. The narrow-line O iii fluxes measured for the lensed images are consistent with those measured in the radio, and show a significant deviation from what would be expected in a smooth mass distribution, consistent with the presence of a perturbing low-mass halo. Detailed lens modelling shows that image fluxes and positions are fitted significantly better when the lens is modelled as a system containing a single perturbing subhalo in addition to the main halo, rather than by the main halo on its own, indicating the significant detection of substructure. The inferred mass of the subhalo depends on the subhalo mass density profile: the 68 per cent confidence intervals for the perturber mass within 600 pc are 8.2
$^{+0.6}_{-0.8}$
, 8.2
$^{+0.6}_{-1}$
and 7.6 ± 0.3 log10M
sub/M⊙, respectively, for a singular isothermal sphere, a pseudo-Jaffe and a Navarro–Frenk–White mass profile. This method can extend the study of flux ratio anomalies to virtually all quadruply imaged quasars, and therefore offers great potential to improve the determination of the subhalo mass function in the near future.
Xylosandrus crassiusculus
is an invasive ambrosia beetle comprising two differentiated genetic lineages, named cluster 1 and cluster 2. These lineages invaded different parts of the world at ...different periods of time. We tested whether they exhibited different climatic niches using Schoener’s D and Hellinger’s I indices and modeled their current potential geographical ranges using the Maxent algorithm. The resulting models were projected according to future and recent past climate datasets for Europe and the Mediterranean region. The future projections were performed for the periods 2041–2070 and 2071–2100 using 3 SSPs and 5 GCMs. The genetic lineages exhibited different climate niches. Parts of Europe, the Americas, Sub-Saharan Africa, Asia, and Oceania were evaluated as suitable for cluster 1. Parts of Europe, South America, Central and South Africa, Asia, and Oceania were considered as suitable for cluster 2. Models projection under future climate scenarios indicated a decrease in climate suitability in Southern Europe and an increase in North Eastern Europe in 2071–2100. Most of Southern and Western Europe was evaluated as already suitable for both clusters in the early twentieth century. Our results show that large climatically suitable regions still remain uncolonized and that climate change will affect the geographical distribution of climatically suitable areas. Climate conditions in Europe were favorable in the twentieth century, suggesting that the recent colonization of Europe is rather due to an increase in propagule pressure via international trade than to recent environmental changes.
Strong gravitational lens systems with measured time delays between the multiple images provide a method for measuring the 'time-delay distance' to the lens, and thus the Hubble constant. We present ...a Bayesian analysis of the strong gravitational lens system B1608+656, incorporating (1) new, deep Hubble Space Telescope (HST) observations, (2) a new velocity-dispersion measurement of 260 +- 15 km s{sup -1} for the primary lens galaxy, and (3) an updated study of the lens' environment. Our analysis of the HST images takes into account the extended source surface brightness, and the dust extinction and optical emission by the interacting lens galaxies. When modeling the stellar dynamics of the primary lens galaxy, the lensing effect, and the environment of the lens, we explicitly include the total mass distribution profile logarithmic slope gamma' and the external convergence kappa{sub ext}; we marginalize over these parameters, assigning well-motivated priors for them, and so turn the major systematic errors into statistical ones. The HST images provide one such prior, constraining the lens mass density profile logarithmic slope to be gamma' = 2.08 +- 0.03; a combination of numerical simulations and photometric observations of the B1608+656 field provides an estimate of the prior for kappa{sub ext}: 0.10{sup +0.08}{sub -0.05}. This latter distribution dominates the final uncertainty on H{sub 0}. Fixing the cosmological parameters at OMEGA{sub m} = 0.3, OMEGA{sub L}AMBDA = 0.7, and w = -1 in order to compare with previous work on this system, we find H{sub 0} = 70.6{sup +3.1}{sub -3.1} km s{sup -1} Mpc{sup -1}. The new data provide an increase in precision of more than a factor of 2, even including the marginalization over kappa{sub ext}. Relaxing the prior probability density function for the cosmological parameters to that derived from the Wilkinson Microwave Anisotropy Probe (WMAP) five-year data set, we find that the B1608+656 data set breaks the degeneracy between OMEGA{sub m} and OMEGA{sub L}AMBDA at w = -1 and constrains the curvature parameter to be -0.031 < OMEGA{sub k} < 0.009 (95% CL), a level of precision comparable to that afforded by the current Type Ia SNe sample. Asserting a flat spatial geometry, we find that, in combination with WMAP, H{sub 0} = 69.7{sup +4.9}{sub -5.0} km s{sup -1} Mpc{sup -1} and w = -0.94{sup +0.17}{sub -0.19} (68% CL), suggesting that the observations of B1608+656 constrain w as tightly as the current Baryon Acoustic Oscillation data do.
Based on 58 SLACS strong-lens early-type galaxies (ETGs) with direct total-mass and stellar-velocity dispersion measurements, we find that inside one effective radius massive elliptical galaxies with ...M {sub eff} {approx}> 3 x 10{sup 10} M {sub sun} are well approximated by a power-law ellipsoid, with an average logarithmic density slope of ({gamma}'{sub LD}) ident to -dlog(rho{sub tot})/dlog(r) = 2.085{sup +0.025} {sub -0.018} (random error on mean) for isotropic orbits with {beta} {sub r} = 0, +-0.1 (syst.) and {sigma}{sub {gamma}{sup '}}{approx}<0.20{sup +0.04}{sub -0.02} intrinsic scatter (all errors indicate the 68% CL). We find no correlation of {gamma}'{sub LD} with galaxy mass (M {sub eff}), rescaled radius (i.e., R {sub einst}/R {sub eff}) or redshift, despite intrinsic differences in density-slope between galaxies. Based on scaling relations, the average logarithmic density slope can be derived in an alternative manner, fully independent from dynamics, yielding ({gamma}'{sub SR}) = 1.959 +- 0.077. Agreement between the two values is reached for ({beta} {sub r}) = 0.45 +- 0.25, consistent with mild radial anisotropy. This agreement supports the robustness of our results, despite the increase in mass-to-light ratio with total galaxy mass: M {sub eff} propor to L {sup 1.363+}-{sup 0.056} {sub V,eff}. We conclude that massive ETGs are structurally close to homologous with close to isothermal total density profiles ({approx}<10% intrinsic scatter) and have at most some mild radial anisotropy. Our results provide new observational limits on galaxy formation and evolution scenarios, covering 4 Gyr look-back time.
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