Weak lensing study of low mass groups: implications for Ωm

2005 ◽  
Vol 201 ◽  
pp. 340-343
Author(s):  
H. Hoekstra ◽  
M. Franx ◽  
K. Kuijken ◽  
R. G. Carlberg ◽  
H. K. C. Yee
Keyword(s):  
Dynamical Analysis ◽  
Observational Cosmology ◽  
Weak Lensing ◽  
Closed Universe ◽  
Average Mass ◽  
Galaxy Groups ◽  
Low Mass ◽  
Redshift Survey ◽  
Intermediate Redshifts ◽  
Good Agreement

We report on the first measurement of the average mass and mass-to-light ratio of galaxy groups by analysing the weak lensing signal induced by these systems. The Canadian Network for Observational Cosmology Field Galaxy Redshift Survey (CNOC2) allows the identification of a large number of groups at intermediate redshifts. For our analysis we use a sample of 50 groups which are selected on the basis of a careful dynamical analysis of group candidates. We detect a signal at the 99% confidence limit. The best fit singular isothermal sphere model yields an Einstein radius rE = 0″.72 ± 0″.29. This corresponds to a velocity dispersion of 〈σ2〉1/2 = 274±+48-59 km/s, which is in good agreement with the dynamical estimate. Under the assumption that the light traces the mass, we find an average mass-to-light ratio of 191 ± 83 h in the restframe B band. Unlike dynamical estimates, this result is insensitive to problems associated with determining group membership. We use the observed mass-to-light ratio to estimate the matter density of the universe, for which we find Ωm = 0.19 ± 0.10 (ΩΛ = 0), in good agreement with other recent estimates. For a closed universe (Ωm + ΩΛ = 1), we obtain Ωm = 0.13 ± 0.07.

scholarly journals Direct Shear Mapping: Prospects for Weak Lensing Studies of Individual Galaxy–Galaxy Lensing Systems

2015 ◽  
Vol 32 ◽  
Author(s):  
C. O. de Burgh-Day ◽  
E. N. Taylor ◽  
R. L. Webster ◽  
A. M. Hopkins
Keyword(s):  
Weak Lensing ◽  
Mapping Technique ◽  
Direct Shear ◽  
Redshift Galaxy ◽  
The Galaxy ◽  
Redshift Survey ◽  
Mass Assembly ◽  
Using Data ◽  
Spectrally Resolved ◽  
Good Agreement

AbstractUsing both a theoretical and an empirical approach, we have investigated the frequency of low redshift galaxy-galaxy lensing systems in which the signature of 3D weak lensing might be directly detectable. We find good agreement between these two approaches. Using data from the Galaxy and Mass Assembly redshift survey we estimate the frequency of detectable weak lensing at low redshift. We find that below a redshift of z ~ 0.6, the probability of a galaxy being weakly lensed by γ ⩾ 0.02 is ~ 0.01. We have also investigated the feasibility of measuring the scatter in the M* − Mh relation using shear statistics. We estimate that for a shear measurement error of Δγ = 0.02 (consistent with the sensitivity of the Direct Shear Mapping technique), with a sample of ~$50,000 spatially and spectrally resolved galaxies, the scatter in the M* − Mh relation could be measured. While there are currently no existing IFU surveys of this size, there are upcoming surveys that will provide this data (e.g The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), surveys with Hector, and the Square Kilometre Array (SKA)).

scholarly journals Weak-lensing analysis of galaxy pairs using CS82 data

2019 ◽  
Vol 621 ◽  
pp. A90 ◽  
Author(s):  
Elizabeth Johana Gonzalez ◽  
Facundo Rodriguez ◽  
Diego García Lambas ◽  
Martín Makler ◽  
Valeria Mesa ◽  
...  
Keyword(s):  
Total Sample ◽  
Elliptical Galaxies ◽  
The Other ◽  
Weak Lensing ◽  
Dynamical Friction ◽  
Dynamical Mass ◽  
Average Mass ◽  
Single Mass ◽  
Halo Masses ◽  
Good Agreement

Here we analyze a sample of close galaxy pairs (relative projected separation < 25 h−1 kpc and relative radial velocities < 350 km s−1) using a weak-lensing analysis based on the Canada-France-Hawaii Telescope Stripe 82 Survey (CS82). We determine halo masses for the total sample of pairs as well as for interacting, red, and higher-luminosity pair subsamples with ∼3σ confidence. The derived lensing signal for the total sample can be fitted either by a Singular Isothermal Sphere (SIS) with σV = 223 ± 24 km s−1 or a Navarro–Frenk–White (NFW) profile with R200 = 0.30 ± 0.03 h−1 Mpc. The pair total masses and total r band luminosities imply an average mass-to-light ratio of ∼200 h M⊙/L⊙. On the other hand, red pairs which include a larger fraction of elliptical galaxies, show a larger mass-to-light ratio of ∼345 h M⊙/L⊙. Derived lensing masses were compared to a proxy of the dynamical mass, obtaining a good correlation. However, there is a large discrepancy between lensing masses and the dynamical mass estimates, which could be accounted for by astrophysical processes such as dynamical friction, by the inclusion of unbound pairs, and by significant deviations of the density distribution from SIS and NFW profiles in the inner regions. We also compared lensing masses with group mass estimates, finding very good agreement with the sample of groups with two members. Red and blue pairs show large differences between group and lensing masses, which is likely due to the single mass-to-light ratio adopted to compute the group masses.

scholarly journals On the weak lensing masses of a new sample of galaxy groups

2021 ◽  
Author(s):  
Elizabeth J Gonzalez ◽  
Facundo Rodriguez ◽  
Manuel Merchán ◽  
Diego García Lambas ◽  
Martín Makler ◽  
...  
Keyword(s):  
Mass Range ◽  
Dark Matter Halo ◽  
Weak Lensing ◽  
Galaxy Groups ◽  
The Galaxy ◽  
Low Mass ◽  
Characteristic Group ◽  
Halo Masses ◽  
The Masses ◽  
Matching Techniques

Abstract Galaxy group masses are important to relate these systems with the dark matter halo hosts. However, deriving accurate mass estimates is particularly challenging for low-mass galaxy groups. Moreover, calibration of observational mass-proxies using weak-lensing estimates have been mainly focused on massive clusters. We present here a study of halo masses for a sample of galaxy groups identified according to a spectroscopic catalogue, spanning a wide mass range. The main motivation of our analysis is to assess mass estimates provided by the galaxy group catalogue derived through an abundance matching luminosity technique. We derive total halo mass estimates according to a stacking weak-lensing analysis. Our study allows to test the accuracy of mass estimates based on this technique as a proxy for the halo masses of large group samples. Lensing profiles are computed combining the groups in different bins of abundance matching mass, richness and redshift. Fitted lensing masses correlate with the masses obtained from abundance matching. However, when considering groups in the low- and intermediate-mass ranges, masses computed according to the characteristic group luminosity tend to predict higher values than the determined by the weak-lensing analysis. The agreement improves for the low-mass range if the groups selected have a central early-type galaxy. Presented results validate the use of mass estimates based on abundance matching techniques which provide good proxies to the halo host mass in a wide mass range.

Weak-Lensing Study of Low-Mass Galaxy Groups: Implications for Ω[TINF][ITAL]m[/ITAL][/TINF]

2001 ◽  
Vol 548 (1) ◽  
pp. L5-L8 ◽  
Author(s):  
H. Hoekstra ◽  
M. Franx ◽  
K. Kuijken ◽  
R. G. Carlberg ◽  
H. K. C. Yee ◽  
...  
Keyword(s):  
Weak Lensing ◽  
Galaxy Groups ◽  
Low Mass

scholarly journals Dynamics of Star Clusters: Comparison of Theory with Observations and Simulations

1975 ◽  
Vol 69 ◽  
pp. 119-131 ◽  
Author(s):  
R. Wielen
Keyword(s):  
Monte Carlo ◽  
Density Distribution ◽  
Age Distribution ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Open Clusters ◽  
Average Mass ◽  
Low Mass ◽  
Good Agreement

Stellar dynamical theories for collisional systems are tested by numerical N-body simulations of isolated star clusters with N up to 500. For the dynamical evolution of the density distribution in star clusters, good agreement is found between Monte Carlo results and N-body models. There remains a discrepancy between theory and simulations in the rate of stellar escape from clusters and/or in the mechanism by which escapers are produced. Simulations of non-isolated star clusters are compared with observations of open clusters. The observed age distribution of open clusters can be explained by the dynamical dissolution of clusters. Stars of low mass do not escape relatively more frequently than stars of average mass.

scholarly journals THE DEEP2 GALAXY REDSHIFT SURVEY: THE VORONOI-DELAUNAY METHOD CATALOG OF GALAXY GROUPS

2012 ◽  
Vol 751 (1) ◽  
pp. 50 ◽  
Author(s):  
Brian F. Gerke ◽  
Jeffrey A. Newman ◽  
Marc Davis ◽  
Alison L. Coil ◽  
Michael C. Cooper ◽  
...  
Keyword(s):  
Galaxy Groups ◽  
Redshift Survey ◽  
Galaxy Redshift ◽  
Deep2 Galaxy Redshift Survey

scholarly journals ISOCAM and DENIS Survey of 0.5 square degrees in the Bar of the LMC. Detection of the whole TP-AGB Star Population

1999 ◽  
Vol 191 ◽  
pp. 561-566
Author(s):  
C. Loup ◽  
E. Josselin ◽  
M.-R. Cioni ◽  
H.J. Habing ◽  
J.A.D.L. Blommaert ◽  
...  
Keyword(s):  
Mass Loss ◽  
High Mass ◽  
Evolutionary Models ◽  
Agb Stars ◽  
Complete Sample ◽  
High Mass Loss ◽  
Low Mass ◽  
The One ◽  
Good Agreement ◽  
Loss Rates

We surveyed 0.5 square degrees in the Bar of the LMC with ISOCAM at 4.5 and 12 μm, and with DENIS in the I, J, and Ks bands. Our goal was to build a complete sample of Thermally-Pulsing AGB stars. Here we present the first analysis of 0.14 square degrees. In total we find about 300 TP-AGB stars. Among these TP-AGB stars, 9% are obscured AGB stars (high mass-loss rates); 9 of them were detected by IRAS, and only 1 was previously identified. Their luminosities range from 2 500 to 14 000 L⊙, with a distribution very similar to the one of optical TP-AGB stars (i.e. those with low mass-loss rates). Such a luminosity distribution, as well as the percentage of obscured stars among TP-AGB stars, is in very good agreement with the evolutionary models of Vassiliadis & Wood (1993) if most of the TP-AGB stars that we find have initial masses smaller than 1.5 to 2 M⊙.

scholarly journals Testing Pre-Main Sequence Models with Young Binaries

2001 ◽  
Vol 200 ◽  
pp. 472-482
Author(s):  
Francesco Palla
Keyword(s):  
Binary System ◽  
Binary Systems ◽  
Main Sequence ◽  
Young Stars ◽  
System A ◽  
Spectroscopic Binary ◽  
Low Mass ◽  
Good Agreement

I will discuss several tests to gauge the accuracy of pre–main-sequence (PMS) models. Methods to determine the mass of young stars are overviewed, with emphasis on the information provided by double-lined, spectroscopic binary systems. A comparison of the dynamically determined masses with those estimated using the PMS models of Palla & Stahler (1999) is presented. Good agreement between empirical and theoretical masses is found. The analysis of the inferred ages from the isochrones shows a remarkable coevality within each binary system. A complete assessment of the accuracy of PMS tracks needs the identification of eclipsing systems of low-mass.

Recent changes of McCall Glacier, Alaska

1995 ◽  
Vol 21 ◽  
pp. 231-239 ◽  
Author(s):  
Bernhard Rabus ◽  
Keith Echelmeyer ◽  
Dennis Trabant ◽  
Carl Benson
Keyword(s):  
Climate Change ◽  
Exchange Rate ◽  
Mass Balance ◽  
Volume Loss ◽  
Average Mass ◽  
Ice Surface ◽  
Low Mass ◽  
The Mean ◽  
Alaskan Arctic ◽  
Drop Rate

Detailed surveys of McCall Glacier in the Alaskan Arctic reveal changes from 1972 to 1993. The ice surface dropped everywhere, by amounts ranging from about 3 m in the highest cirques tq more than 42 m near the present terminus. The total volume loss was 3.5+ 0.2 x 10' m(, resulting in an average mass balance of 0.33 + 0.01 in a . l he terminus has retreated by about 285 m at a rale of 12_.5 ma \ Results from photogrammetry for an earlier period, 1958-71, were I.16x 10'm3 and 0.13 ma for volume change and mass balance, respectively; the mean terminus retreat rate was then 5.7 m a . The changes have to be seen in the context of McCall Glacier’s low mass-exchange rate; annual accumulation and ablation, averaged over the years 1969 72 were only +0.16 and 0.3 m a '. Cross-profiles in the ablation area, surveyed at intervals of a few years, show an increased drop rate since the late 1970s. 7 he volume-ehange data suggest a climate warming in the early 1970s. Enhanced thinning of the lower ablation region and accelerated terminus retreat seem to lag this climate change by not more than 10 years, This indicates a reaction time of McCall Glacier that is considerably shorter than its theoretic response time of about 50 70 years.

scholarly journals The Frequency of YY Orionis Objects among the T Tauri Stars

1977 ◽  
Vol 42 ◽  
pp. 80-87 ◽  
Author(s):  
I. Appenzeller
Keyword(s):  
Statistical Analysis ◽  
Present Theory ◽  
T Tauri Stars ◽  
Early Evolution ◽  
Low Mass Stars ◽  
T Tauri ◽  
Uv Excess ◽  
Low Mass ◽  
Good Agreement

A list of 24 T Tauri stars belonging to the YY Orionis subclass is presented. From a statistical analysis it is estimated that at least 75% (and possibly all) UV-excess T Tauri stars are YY Orionis stars. Since about 50% of all known T Tauri stars show a strong UV-excess, the percentage of YY Orionis stars among the T Tauri stars is estimated to be 40 - 50%. This relative high percentage is in good agreement with the present theory of the formation and early evolution of low mass stars.

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