3,983 research outputs found
The Rising Stellar Velocity Dispersion of M87 from Integrated Starlight
We have measured the line-of-sight velocity distribution from integrated
stellar light at two points in the outer halo of M87 (NGC 4486), the
second-rank galaxy in the Virgo Cluster. The data were taken at R = 480" ( kpc) and R = 526" ( kpc) along the SE major axis. The second
moment for a non-parametric estimate of the full velocity distribution is km/s and km/s respectively. There is intriguing evidence
in the velocity profiles for two kinematically distinct stellar components at
the position of our pointing. Under this assumption we employ a two-Gaussian
decomposition and find the primary Gaussian having rest velocities equal to M87
(consistent with zero rotation) and second moments of km/s and
km/s respectively. The asymmetry seen in the velocity profiles
suggests that the stellar halo of M87 is not in a relaxed state and confuses a
clean dynamical interpretation. That said, either measurement (full or two
component model) shows a rising velocity dispersion at large radii, consistent
with previous integrated light measurements, yet significantly higher than
globular cluster measurements at comparable radial positions. These integrated
light measurements at large radii, and the stark contrast they make to the
measurements of other kinematic tracers, highlight the rich kinematic
complexity of environments like the center of the Virgo Cluster and the need
for caution when interpreting kinematic measurements from various dynamical
tracers.Comment: 16 pages, 5 figures; accepted for publication in The Astrophysical
Journa
Galaxy Kinematics With Virus-P: The Dark Matter Halo Of M87
We present two-dimensional stellar kinematics of M87 out to R = 238 '' taken with the integral field spectrograph VIRUS-P. We run a large set of axisymmetric, orbit-based dynamical models and find clear evidence for a massive dark matter halo. While a logarithmic parameterization for the dark matter halo is preferred, we do not constrain the dark matter scale radius for a Navarro-Frenk-White (NFW) profile and therefore cannot rule it out. Our best-fit logarithmic models return an enclosed dark matter fraction of 17.2(-5.0)(+5.0)% within one effective radius (R-e congruent to 100 ''), rising to 49.4(-8.8)(+7.2)% within 2 R-e. Existing SAURON data (R <= 13 ''), and globular cluster (GC) kinematic data covering 145 '' <= R <= 554 '' complete the kinematic coverage to R = 47 kpc (similar to 5R(e)). At this radial distance, the logarithmic dark halo comprises 85.3(-2.4)(+2.5)% of the total enclosed mass of 5.7(-0.9)(+1.3) x 10(12) M-circle dot making M87 one of the most massive galaxies in the local universe. Our best-fit logarithmic dynamical models return a stellar mass-to-light ratio (M/L) of 9.1(-0.2)(+0.2) (V band), a dark halo circular velocity of 800(-25)(+75) km s(-1), and a dark halo scale radius of 36(-3)(+7) kpc. The stellar M/L, assuming an NFW dark halo, is well constrained to 8.20(-0.10)(+0.05) (V band). The stars in M87 are found to be radially anisotropic out to R congruent to 0.5 R-e, then isotropic or slightly tangentially anisotropic to our last stellar data point at R = 2.4 R-e where the anisotropy of the stars and GCs are in excellent agreement. The GCs then become radially anisotropic in the last two modeling bins at R = 3.4 R-e and R = 4.8 R-e. As one of the most massive galaxies in the local universe, constraints on both the mass distribution of M87 and anisotropy of its kinematic components strongly inform our theories of early-type galaxy formation and evolution in dense environments.Astronom
Investigating Fatigue Performance on the Foamed Asphalt Specimens Generated Using Different Foam Properties
An evaluation of fatigue resistance for foamed asphalt mixture is very demanding since the binder is not continuously distributed on the aggregate surface and this mixtures contains water, the content of which dramatically affects the mechanical properties. This paper discusses the results of laboratory fatigue testingon the foamed asphalt mixtures in which the specimens are generated using three different foamed bitumen properties. Foamed bitumen as the binder was produced at three different foaming water content (FWC) at a temperature of 180oC using a 70/100 pen. The aggregates were mechanically mixed with foamed bitumen using a Hobart mixer. The resulting mixtures were then compacted using a gyratory compactor to generatespecimen with diameter of 100 mm. The specimens were fatigue tested at various stress levels at a temperature of 20oC following a curing period of 3 days at 40oC. Overall, fatigue performance of foamed asphalt can be identified based upon both stress and strain for mixtures produced at FWC 1%, 5%, and 10%
Effects of Carbohydrate Mouth Rinsing Plus Ingestion On Cycling Time Trial Performance
Due to limited glycogen stores, carbohydrate (CHO) consumption during exercise is effective at improving performance in endurance events lasting longer than 90 minutes in duration. Recent research has established that CHO mouth rinsing may improve performance over shorter durations, independent of actual consumption. However, research is lacking in determining if an extended period of mouth rinsing has any additive benefit in conjunction with typical CHO beverage consumption over longer competition durations, where CHO ingestion/consumption is likely warranted. PURPOSE: Determine the effects of CHO mouth rinsing combined with consumption compared to CHO consumption alone on cycling performance. METHODS: Following an initial graded exercise test to determine VO2max, 5 male cyclists completed two cycling performance trials in a randomized, double-blind, crossover design. In order to determine any added benefit of an extended CHO mouth rinse period prior to consumption, trials consisted of two drinking conditions: 1) placebo (PLA) mouth rinse plus CHO consumption and 2) CHO mouth rinse plus CHO consumption. For the mouth rinsing, a 25 mL solution (PLA: Gatorade Zero; CHO: Gatorade) was swished for 5 seconds before spitting out. Mouth rinsing was always followed up by actual consumption of 1.5 ml/kg of CHO beverage (Gatorade). Performance trials consisted of an initial 1-hour cycling bout at a workload corresponding to 60% VO2max on an electronically braked cycle ergometer
(Wahoo Kickr). During this 1-hour segment, a 30-second sprint was performed every 10 minutes, for a total of 6 sprint efforts. The mouth rinsing/consumption protocol was performed prior to each sprint interval. Following the 1-hour bout with intermittent sprints, a 20 km time trial was performed using the simulation mode setting on the cycle ergometer. The same mouth rinsing/consumption protocol was performed every 4 km during the time trial. A two-way (condition x time) repeated measures ANOVA was used to determine effects on sprint power output and rating of perceived exertion (RPE) during the 1-hour segment as well as 20 km time trial performance. RESULTS: There were no main effects for condition or interactions for any of the performance variables measured. Averages values ± SD for the 6 sprint segments during the 1-hour bout were as follows: sprint power (watts, CHO: 425 ± 80, PLA: 437 ± 48), heart rate (bpm, CHO: 157 ± 12, PLA: 157 ± 8), RPE (CHO: 16.7 ± 3.3, PLA: 17.3 ± 2.4). Further, 20 km time trial performance did not differ between conditions (CHO: 43.1 ± 3.8 min, PLA: 42.8 ± 3.6 min). CONCLUSION: In this limited sample, it does not appear that an extended CHO mouth rinsing period has any additive benefit to typical CHO consumption. This would suggest that any receptors thought to be stimulated through mouth rinsing are already stimulated adequately with normal CHO beverage consumption
Dynamical Measurements of Black Hole Masses in Four Brightest Cluster Galaxies at 100 Mpc
We present stellar kinematics and orbit superposition models for the central
regions of four Brightest Cluster Galaxies (BCGs), based upon integral-field
spectroscopy at Gemini, Keck, and McDonald Observatories. Our integral-field
data span radii from < 100 pc to tens of kpc. We report black hole masses,
M_BH, of 2.1 +/- 1.6 x 10^10 M_Sun for NGC 4889, 9.7 + 3.0 - 2.6 x 10^9 M_Sun
for NGC 3842, and 1.3 + 0.5 - 0.4 x 10^9 M_Sun for NGC 7768. For NGC 2832 we
report an upper limit of M_BH < 9 x 10^9 M_Sun. Stellar orbits near the center
of each galaxy are tangentially biased, on comparable spatial scales to the
galaxies' photometric cores. We find possible photometric and kinematic
evidence for an eccentric torus of stars in NGC 4889, with a radius of nearly 1
kpc. We compare our measurements of M_BH to the predicted black hole masses
from various fits to the relations between M_BH and stellar velocity
dispersion, luminosity, or stellar mass. The black holes in NGC 4889 and NGC
3842 are significantly more massive than all dispersion-based predictions and
most luminosity-based predictions. The black hole in NGC 7768 is consistent
with a broader range of predictions.Comment: 24 pages, 18 figures. Accepted for publication in Ap
Phenotypic plasticity for life-history traits in Drosophila melanogaster. III. Effect of the environment on genetic parameters
We estimated genetic and environmental variance components for developmental time and dry weight at eclosion in Drosophila melanogaster raised in ten different environments (all combinations of 22, 25 and 28°C and 0·5, 1 and 4% yeast concentration, and 0·25% yeast at 25°C). We used six homozygous lines derived from a natural population for complete diallel crosses in each environment. Additive genetic variances were consistently low for both traits (h2 around 10%). The additive genetic variance of developmental time was larger at lower yeast concentrations, but the heritability did not increase because other components were also larger. The additive genetic effects of the six parental lines changed ranks across environments, suggesting a mechanism for the maintenance of genetic variation in heterogenous environments. The variance due to non-directional dominance was small in most environments. However, there was directional dominance in the form of inbreeding depression for both traits. It was pronounced at high yeast levels and temperatures but disappeared when yeast or temperature were decreased. This meant that the heterozygous flies were more sensitive to environmental differences than homozygous flies. Because dominance effects are not heritable, this suggests that the evolution of plasticity can be constrained when dominance effects are important as a mechanism for plasticit
American Indian Women and Sexual Assault: Challenges and New Opportunities
This article informs social workers about sexual violence against American Indian and Alaskan Native (AI/AN) women and the policy reforms in the 2010 Tribal Law and Order Act (TLOA). It describes the unmet needs of AI/AN survivors, reviews the TLOA reforms on sexual assault in relation to social work and public health principles, discusses the complementary roles for social workers and public health practitioners in reform efforts, and offers guidance for professional participation that emphasizes tribal sovereignty, indigenous capacity, and cultural competence
The Stellar Halos of Massive Elliptical Galaxies II: Detailed Abundance Ratios at Large Radius
We study the radial dependence in stellar populations of 33 nearby early-type
galaxies with central stellar velocity dispersions sigma* > 150 km/s. We
measure stellar population properties in composite spectra, and use ratios of
these composites to highlight the largest spectral changes as a function of
radius. Based on stellar population modeling, the typical star at 2 R_e is old
(~10 Gyr), relatively metal poor ([Fe/H] -0.5), and alpha-enhanced
([Mg/Fe]~0.3). The stars were made rapidly at z~1.5-2 in shallow potential
wells. Declining radial gradients in [C/Fe], which follow [Fe/H], also arise
from rapid star formation timescales due to declining carbon yields from
low-metallicity massive stars. In contrast, [N/Fe] remains high at large
radius. Stars at large radius have different abundance ratio patterns from
stars in the center of any present-day galaxy, but are similar to Milky Way
thick disk stars. Our observations are thus consistent with a picture in which
the stellar outskirts are built up through minor mergers with disky galaxies
whose star formation is truncated early (z~1.5-2).Comment: ApJ in press, 12 pages, 6 figure
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