Thursday. Monday.
1403.4599
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Signs of neutrino mass in current cosmological datasets
Beutler, Saito, … Percival, Ross, Ross, Samushia, Seo, Tinker, et al
Investigate the cosmological implications of the growth of structure measurements from BOSS CMASS DR11 with particular focus on the sum of neutrino masses. Examine the robustness of the cosmological constraints from BAO scale, the Alcock-Paczynski effect and redshift-space distortions (D_v/r_s, F_AP, f*sigma_8), when introducing a neutrino mass in the PS template. Any shift in the CMASS constraints is below 0.5 sigma when changing Sum m_nu from 0eV to 0.4 eV, which roughly represents the currently allowed range for this parameter. Then discuss how the neutrino mass relaxes discrepancies between the CMB and other low-z measurements within LCDM. Combining cosmo constraints with WMAP9 yields Sum m_nu=0.36pm0.14 eV, which represents a 2.6 sigma preference for neutrino mass. The significance can be increase to 3.3 sigma when including WL results and other BAO constraints, yielding Sum m_nu=0.35pm0.10 eV. However, combining CMASS with Planck reduces the preference for neutrino mass to ~2 sigma. When removing the CMB lensing effect in the Planck temperature PS (by marginalizing over A_L), see shifts of ~1 sigma in sigma_8 and Omega_m, which have a significant effect on the neutrino mass constraints. In case of CMASS plus Planck without the A_L-lensing signal, find a preference for a neutrino mass of Sum m_nu=0.34pm0.14 eV, in excellent agreement with the WMAP9+CMASS value. The constraint can be tightened to 3.4 sigma yielding Sigma m_nu=0.36pm0.10eV when WL data and other BAO constraints are included.
1403.5265
Temporal self-organization in galaxy formation
CenFind a relation between the number of SF peaks per unit time and the size of the temporal smoothing window function. This relation holds over the range of Delta t = 10 to 1000 Myr that can be reliably computed, using a large sample of galaxies obtained from cosmo hydro sims. This means that the temporal distribution of SF peaks in galaxies as a population is fractal. This reveals that the superficially chaotic process of galaxy formation is underlined by a temporal self-orgainziattion up to at least 1 Gyr. Given the known existence of spatial fractals (such as the power-law 2pt function of galaxies), there is a joint spatio-temporal self-organization in galaxy formation. From an observational perspective, it will be urgent to devise diagnostics to probe SF histories of galaxies with good temporal resolution to facilitate a test of this prediction. If confirmed, it would provide unambiguous evidence for a new picture of galaxy formation that is interaction driven, cooperative and coherent in and between time and space. Unravelling its origin may hold the key to understanding galaxy formation.
1403.5269
Bulge mass is king: the dominant role of the bulge in determining the fraction of passive galaxies in the Sloan digital sky survey
Bluck, … Moreno, et al
Investigate the origin of galaxy bimodality by quantifying the relative role of intrinsic and environmental drivers to the cessation (or `quenching') of star formation in over half a million local SDSS galaxies. Sample contains a wide variety of galaxies at z=0.02-0.2, with stellar masses of 8<log(M*/Msun)<12, spanning the entire morphological range from pure disks to spheroids, and over four orders of magnitude in local galaxy density and halo mass. Utilize published SFRs and add to this the recent GIM2D photometric and stellar mass bulge+disk decompositions from the group. Find that the passive fraction of galaxies increases steeply with stellar mass, halo mass, and bulge mass, with a less steep dependence on local galaxy density and bulge-to-total stellar mass ratio (B/T). At fixed internal properties, find that central and satellite galaxies have different passive fraction relationships. For centrals, conclude that there is less variation in the passive fraction at a fixed bulge mass, than for any other variable, including total staler mass, halo mass, and B/T. This implies that the quenching mechanism must be most tightly coupled to the bulge. Argue that radio mode AGN feedback offers the most plausible explanation of the observed trends.
1403.5271
CMB polarization can constrain cosmology better than CMB temperature
Galli, et al
Demonstrate that for a cosmic variance limited experiment, CMB E polarization alone places stronger constraints on cosmo params than CMB temperature. Show that EE can constrain parameters better than TT by a factor of 2.8 when a multipole range of ell=30-2500 is considered. Expose the physical effects at play behind this result and study how it depends on the multipole range included in the analysis. In most relevant cases. TE or EE surpass the TT based cosmological constraints. This result is important as the small scale astrophysical FGs are expected to have much reduced impact on polarization, thus opening the possibility of building cleaner and more stringent constraints of the LCDM model. This is relevant specially for proposed future CMB satellite missions, such as CORE or PRISM, that are resigned to be cosmic variance limited in polarization till very large multipoles. Perform the same analysis for a Planck-like experiment, and conclude that even in this case TE alone should determine the constrain on Omega_c h^2 better than TT by 15%, while determining Omega_b h^2, n_s and theta with comparable accuracy. Explore a few classical extensions of the LCDM model and show again that CMB polarization alone provides more stringent constraints than CMB temperature in case of a cosmic variance limited experiment.
1403.5274
Frequent spin reorientation of galaxies due to local interactions
Cen
Study the evolution of angular momenta of M*=1e10-12 Msun galaxies utilizing large-scale ultra-high resolution cosmological hydro sims and find that spin of the stellar component changes direction frequently, caused by major mergers, minor mergers, significant gas inflows and toques by nearby systems. The rate and nature of change of spin direction can not be accounted for by large-scale tidal torques, because the latter fall short in rates by orders of magnitude and because the apparent random swings of the spin direction are inconsistent with alignment by linear density field. The implications for galaxy formation as well as intrinsic alignment of galaxies are profound. Assuming the large-scale tidal field is the sole alignment agent, a new picture emerging is that intrinsic alignment of galaxies would be a balance between slow large-scale coherent torquing and fast spin reorientation by local interactions. What is still open is whether other processes, such as feeding galaxies with gas and stars along filaments or sheets, introduce coherence for spin directions of galaxies along the respective structures.
1403.5466
New observations of z~7 galaxies: evidence for a patchy reioinzation
Pentericci et al
New results from z~7 galaxy search from deep spectra observations of candidate z-dropouts in the CANDELS fields. Despite the extremely low flux limits achieved by the observations, only 2 galaxies have robust redshift identifications, one from Lya emission at z=6.65, the other from its Lyman-break, consistent with z=6.42, but with no emission line. In addition, for 23 galaxies, present deep limits in the Lya EW derived from the non detections in ultra-deep observations. Using this new data as well as previous samples, assemble a total of 68 candidate z~7 galaxies with deep spectroscopic observations, of which 12 have a line detection. With this much enlarged sample, can place solid constraints on the declining fraction of Lya emission in z~7 Lyman break galaxies compared to z~6, both for bright and faint galaxies. Applying a simple analytical model, show that the present data favor a patchy reionization process rather than a smooth one.
1403.5499
A universal density profile for cosmic voids
Hamaus, Sutter, Wandelt
Present a simple empirical function for the average density profile of cosmic voids, identified via the LCDM N-body sims. This function is universal across void size and z, accurately describing the entire radial range of scales around void centers with only two free parameters. In analogy to halo density profiles, these parameters describe the scale radius and the central density of voids. Initially start with a more general 4-parameter model, find two of its parameters to be redundant, as they follow linear trends with the scale radius in two distinct regimes of the void sample, separated by its compensation scale. Assuming linear theory, derive an analytic formula for the velocity profile of voids and find an excellent agreement with the numerical data as well. In the companion paper, the presented density profile is shown to be universal even across tracer type, properly describing voids defined in halo- and galaxy distributions of varying sparsity, allowing to relate various void populations by simple rescalings. This provides a powerful framework to match theory and simulations with observational data, opening up promising perspectives to constrain competing models of cosmology and gravity.
*** Galaxy-galaxy lensing review section ***
9503073
Measuring galaxy masses using galaxy-galaxy gravitational lensing
Brainerd, Blandford, Smail
Detection of weak, tangential distortion of the images of cosmologically distant, faint galaxies due to gravitational lensing by FG galaxies. A mean image polarization of <p>=0.011pm0.006 is measured for 3203 pairs of source galaxies with 23<r<=24 and lens galaxies with magnitudes 20<=r<=23. The signal remains strong for lens-source separations <90", consistent with quasi-isothermal galaxy haloes extending to large radii (100 kpc/h). Observations thus provide the first evidence from WL of large scale dark haloes associated with individual galaxies. The observed polarization is also consistent with the signal expected on the basis of simulations incorporating measured properties of local galaxies and modest extrapolations of the observed z distribution of faint galaxies. From the simulations, derive a best-fit halo circular velocity of V~220 km/s and characteristic radial extant of s~100 kpc/h on the order of 1e12 Msun/h, in good agreement with recent dynamical estimate of the masses of local spiral galaxies. This is particularly encouraging as the lensing and dynamical mass estimators rely on different sets of assumptions. Contamination of the gravitational lensing signal by a population of tidally distorted satellite galaxies can be ruled out with reasonable confidence. The prospects for corroborating and improving this measurement seem good, especially using deep HST archival data.
9711341
Galaxy-galaxy lensing in the Hubble deep field: the halo Tully-Fisher relation at intermediate redshift
Hudson, Gwyn, Dahle, Kaiser
A tangential distortion of background source galaxies around foreground lens galaxies in the HDF is detected at 88.3% CL. An important element of the analysis is the use of photometric redshifts to determine distances of lens and source galaxies and rest-frame B-band luminosities of the lens galaxies. The lens galaxy haloes obey a TF relation between halo circular velocity and luminosity; the typical lens galaxy, at z=0.6, has a circular velocity of 210pm40 km/s at M_B=-18.5, if q_0=0.5. Control tests, in which lens and source positions and source ellipticities are randomized, confirm the significance level of the detection quoted above. Furthermore, a marginal signal is also detected from an independent, fainter sample of source galaxies without photo-z. Potential systematic effects, such as contamination by aligned satellite galaxies, the distortion of source shapes by the light of the FG galaxies, PSF anisotropies, and contributions from mass distributed on the scale of galaxy groups are shown to be negligible. A comparison of the result with the local TF relation indicates that intermediate-z galaxies are fainter than local spirals by 1pm0.6 B mag at a fixed circular velocity. This is consistent with some spectroscopic studies of the rotation curves of intermediate-z galaxies. This result suggest that the strong increase in the global luminosity density with z is dominated by evolution in the galaxy number density.
9912119
Weak lensing with SDSS commissioning data: the galaxy-mass correlation function to 1/h Mpc
SDSS Collaboration, Fischer, et al
Present measurements of gg lensing from early commissioning imaging data from SDSS. Measure a mean tangential shear around a stacked sample of FG galaxies in 3 bandpasses out to angular radii of 600", detecting the shear signal at very high statistical significance. The shear profile is well described by a power-law. A variety of rigorous tests demonstrate the reality of the gravitational lensing signal and confirm the uncertainty estimates. Interpret results by modeling the mass distributions of the FG galaxies as approximately isothermal spheres characterized by a velocity dispersion and truncation radius. The velocity dispersion is constrained to be 150-190 km/s at 95% confidence (145-195 km/s including systematic uncertainties), consistent with previous determinations but with smaller error bars. Detection of shear at large angular radii sets a 95% confidence lower limit s>140", corresponding to a physical radius of 260 kpc/h, implying that galaxy haloes extend to very large radii. However, it is likely that this is being biased high by diffuse matter in the haloes of groups and clusters. Also present a preliminary determination of the galaxy-mass correlation function finding a correlation length similar to the galaxy autocorrelation function and consistency with a low matter density universe with modest bias. The full SDSS will cover an area 44 times larger and provide spectroscopic z for the FG galaxies, making it possible to greatly improve the precision of these constraints, measure additional parameters such as halo shape, and measure the properties of DM haloes separately for many different classes of galaxies.
0108013
Galaxy mass and luminosity scaling laws determined by weak gravitational lensing
McKay, Sheldon, … Fischer, Seljak, et al
New measurements of scaling laws relating the luminosity of galaxies to the amplitude and shape of their dark matter haloes. Early imaging and spectroscopic data from SDSS are used to make WL measurements of the surface mass density contrast Delta Sigma_+ around classes of lens objects. This surface mass density contrast as a function of radius is a measure of the galaxy-mass correlation function (GMCF). Because spectroscopic z are available for all lens objects, the mass and distance scales are well constrained. The GMCF measured around ~31,000 lenses is well fit by a power law of the form Delta Sigma_+=.24 (R/1 Mpc)^-0.8 h Msun / pc^2. Compare this GMCF to galaxy luminosity, type, and environment, and find that it varies strongly with all three. Quantify these variations by comparing the normalization of a fit to the inner 260 kpc/h M_260, to the galaxy luminosity. While M_260 is not strongly related to luminosity in bluest band u', there is a simple, linear relation between M_260 and luminosity in redder bands (g', r', i' and z'). Test the universality of these M/L scalings by independently measuring them for spiral and elliptical galaxies, and for galaxies in a variety of environments. Find remarkable consistency in these determinations in the red bands, especially i' and z'. This consistency across a wide range of systems suggests that the measured scaling represents an excellent cosmic average, and that the integrated SFH of galaxies is strongly related to the dark matter environments in which they form.
0211633
Lensing bay galaxies in CNOC2 fields
Hoekstra, Franx, Kuijken, Carlberg, Yee
Observed two blank fields of approximate 30'x23'; the fields have been studied as part of the CNOC2 survey, and spec-zs are available for 1125 galaxies in the two fields. Measured the leaning signal caused by large scale structure, and found the the result is consistent with current, more accurate measurements. Study the gg lensing signal of 3 overlapping samples of lenses, and detect a significant signal in all cases. The estimates for the velocity dispersion of an L* galaxy agree well for the various samples. The best fit singular isothermal sphere model to the ensemble averaged tangential distortion around the galaxies with redshifts yields a velocity dispersion of sigma_*=130km/s, in agreement with other studies. Use a maximum likelihood analysis, where a parameterized mass model is compared to the data, to study the extent of galaxy DM haloes. Making use of all available data, find sigma*=111 km/s (68.3% CL) for a truncated isothermal sphere model in which all galaxies have the same M/L ratio. The value of the truncation parameter is not constrained that well, and find s*=260 kpc/h (68.3% CL). The gg lensing analysis allows estimation of the average M/L ratio of the field, which can be used to estimate Omega_m. The current result, however, depends strongly on the assumed scaling relation for s.
0312036
The galaxy-mass correlation function measured from weak lensing in the SDSS
Sheldon, Johnston, Frieman, Scranton, McKay, Connolly, Budavari, Zehavi, Bahcall, Brinkmann, Fukugita
Present gg lensing measurements over scales 0.025 to 10 Mpc/h in the SDSS. Using a flux-limited sample of 127k lens galaxies with spec-z and mean luminosity <L>=L* and 9M source galaxies with photo-z, invert the lensing signal to obtain the galaxy-mass correlation function xi_{gm}. Find xi_{gm} is consistent with a power-law, xi_gm=(r/r0)^-gamma, with best-fit parameters gamma=1.79pm0.06 and r0=5.4pm0.7(0.27/Omega_m)^{1/gamma} Mpc/h. At fixed separation, the ratio xi_gg/xi_gm= b/r where b is the bias and r is the correlation coefficient. Comparing to the galaxy auto-correlation function for a similarly selected sample of SDSS galaxies, find that b/r is approximately scale independent over scales 0.2-6.7 Mpc/h, with mean <b/r>=1.3 (Omega_m/0.27). Also find no scale dependence in b/r for a volume limited sample of luminous galaxies (-23<Mr<-21.5). The mean b/r for this sample is <b/r>_{Vlim}=2(Omega_m/0.27). Split the lens galaxy sample in to subsets based on luminosity, color, spectral type, and velocity dispersion, and see clear trends of the lensing signal with each of these parameters. The amplitude and logarithmic slope of xi_gm increases with galaxy luminosity. For high luminosities (L~5L*), xi_gm deviates significantly from a power law. These trends with luminosity also appear in the subsample of red galaxies, which are more strongly clustered than blue galaxies.
0403698
Large scale bias and stochasticity of halos and dark matter
Seljak, Warren
On large scales galaxies and their haloes are usually assumed to trace the dark matter with a constant bias and DM is assumed to trace the linear density field. Test these assumption using several large N-body sims with 384^3-1024^3 part ices and box sizes between 100-1000 h/Mpc, which can both resolve the small galactic size haloes and sample the large scale fluctuations. Explore the average halo bias relation as a function of halo mass and show that existing fitting formulae overestimate the halo bias by up to 20% in the regime just below the NL mass. Propose a new expression that fits simulations well. Find that the halo bias is nearly constant, b~0.65-0.7, for masses below 1/10th of the NL mass. Explore next the relation between the initial and final DM in individual Fourier modes and show that there are significant fluctuations in their ratio, ranging from 10% rms at k~0.03 h/Mpc to 50% rms at k~0.1 h/Mpc. Argue that these large fluctuations are caused by perturbative effects beyond the linear theory, which are dominated by long wavelength modes with large random fluctuations. Similar or larger fluctuations exist between halos and DM and between haloes of different mass. While these fluctuations are small compared to the sampling variance, they are significant for attempts to determine the bias by relating directly the maps of galaxies and DM or the maps of different galaxy populations, which would otherwise be immune to sampling variance.
0605476
Density profiles of galaxy groups and clusters from SDSS galaxy-galaxy weak lensing
Mandelbaum, Seljak, Cool, Blanton, Hirata, Brinkmann
Present results of a measurement of the shape of the density profile of galaxy groups and clusters traced by 43k LRGs with spec-z from SDSS. The galaxies are selected such that they are the brightest within a cylindrical aperture, split into two luminosity samples, and modeled as the sum of stellar and DM components. Present a detailed investigation of many possible systematic effects that could contaminate the signal and develop methods to remove them, including a detected intrinsic alignment of galaxies within 100 kpc/h of LRGs which is removed using photo-z information. The resulting lensing signal is consistent with NFW profile DM haloes; the SIS profile is ruled out at the 96 (conservatively) and 99.96% CL for the fainter and brighter lens samples (respectively) when they are fit using lensing data between 40 kpc/h and 2Mpc/h with total S/N of 19 and 25 for the two lens maples. The lensing signal amplitude suggests that the faint and bright sample galaxies typically reside in haloes of mass 2.9e13 Msun/h and 6.7e13 Msun/h respectively, in good agreement with predictions based on halo spatial density with normalization lower that the 'concordance' sigma_8=0.9. When fitting for the concentration parameter in the NFW profile, find c=5.0 and 5.6 for the faint and bright samples, consistent with LCDM simulations. Also split the bright sample further to determine masses and concentrations for cluster-mass haloes, finding mass 1.3e14 Msun/h for the sample f LRGs brighter than -22.6 in r.
2006A&A…544..441K
Weak lensing measurements of dark matter haloes of galaxies from COMBO-17
Kleineinrich, Schneider, Rix, Erben, Wolf, Schirmer, Meisenheimer, Borch, Dye, Kovacs, Wisotzki
Present mass estimates for DM haloes around galaxies from the COBMO-17 survey using weak gravitational lensing. COMBO-17, with photometry in 17 optical filters, provides precise photometric redshifts and spectral classification for objects with R<24. This permits to select and sort lens and source galaxies by their redshifts and lens luminosity or color, which bypasses many uncertainties in other WL analysis arising from broadly estimated source and lens redshifts. Study the shear created by DM haloes around 12k galaxy lenses at 0.2<z<0.7 by fitting the mass normalization of either singular isothermal spheres (SIS) or NFW profiles to BG source orientations around the whole lens sample. Also consider haloes around blue and red subsamples separately and constrain the scaling of halo mass with light. For the NFW model, find virial masses M*_vir=3.9e11 Msun/h for blue and 7.1e11 Msun/h for red galaxies of L*=1e10 Lsun/h^2, respectively. The 1 sigma uncertainty on log M*vir for the whole lens sample is about 0.2. Compare results to those obtained from RCS and SDSS. Taking differences in the actual modeling into account, find very good agreement with these surveys.
0707.1698
The masses and shapes of dark matter halos from galaxy-galaxy lensing in the CFHTLS
Parker, Hoekstra, Hudson, Van Waerbeke, Mellier
Present the first gg WL results using early data from CFHTLS. These results are based on ~22 sq deg of i' data. From this data, estimate the average velocity dispersion for an L* galaxy at z~0.2 to be 137 km/s, with virial mass M200 of 1.1e12 Msun/h and a rest frame R-band M/L ratio of 173 h Msun/Lsun. Also investigate various possible sources of systematic error in detail. Additionally, separate lens sample into two sub-samples, divided by apparent magnitude, thus average redshift. From this early data, do not detect significant evolution in galaxy DM halo M/L ratios in 0.45<z<0.27. Finally, test for non-spherical galaxy dark matter haloes. Results favor a DM halo with an ellipticity of ~0.3 at the 2 sigma level when averaged over all galaxies. If the sample of FG lens galaxies is selected to favor ellipticals, the mean halo ellipticity and significant of this result increase.
0805.3459
Relative clustering and the joint halo occupation distribution of red-sequence and blue-cloud galaxies in COMBO-17
Simon, Hetterscheidt, Wolf, Meisenheimer, Hildebrandt, Schneider, Schirmer, Erben
Study the relative spatial distribution of red-sequence and blue-cloud galaxies, and their relation to the dark matter distribution in the COMBO-17 survey as function of scale down to z~1. Measure the 2nd order auto-and cross-correlation functions of galaxy clustering and express the relative biasing by using aperture statistics. Also estimated is the relation between the galaxies and the DM distribution exploiting GGL. All observables are further interpreted interns of a halo mode. To fully explain the galaxy clustering cross-correlation function with a halo model, need to introduce a new parameter, R, that describes the statistical relation between numbers of red and blue galaxies within the same halo. Find that red and blue galaxies are clearly differently clustered. A significant evolution of the relative clustering with redshift was not found. There is evidence for a scale-dependence of relative biasing. The relative clustering, the GGL and, with some tension, the galaxy numbers can be explained consistently within a halo model. For the cross-correlation function one requires a HOD variance that becomes Poisson even for relatively small occupancy numbers. For the sample, this rules out with high confidence a "Poisson satellite" scenario as found in SAM. Red galaxies have to be concentrated towards the halo center, either by a central red galaxy or bay a concentration parameter above that for DM. The value of R depends on the presence or absence of central galaxies: if no central galaxies or only red central galaxies are allowed, R is consistent with zero, whereas a positive correlation R=0.5pm0.2 is needed if both blue and red galaxies can have central galaxies.
1104.0928
New constraints on the evolution of the stellar-to-dark matter connection: a combined analysis of galaxy-galaxy lensing, clustering, and stellar mass functions from z=0.2 to z=1
Leauthaud et al
Using data from COSMO, perform the first joint analysis of gg WL, galaxy spatial clustering, and galaxy number densities. Carefully accounting for sample variance and for scatter between stellar and halo mass, model all 3 observables simultaneously using a novel and self-consistent theoretical framework. Results provide strong constraints on the shape and z evolution of the stellar-to-halo mass relation (SHMR) from z=0.2 to 1. At low stellar mass, find that halo mass scales with Mh ~ M*^0.46 and that this scaling does not evolve significantly with redshift to z=1. Show that the dark-to-stellar ratio, Mh/M*, varies from low to high masses, reaching a minimum of Mh/M*~27 at M*=4.5e10 Msun and Mh=1.2e12 Msun. This minimum is important for models of galaxy formation because it marks the mass at which the accumulated stellar growth of the central galaxy has been the most efficient. Describe the SHMR at this minimum in terms of the "pivot stellar mass", M*piv, the "pivot halo mass", Mhpiv, and the "pivot ratio", (Mh/M*) piv. Thanks to a homogeneous analysis of a single data set, report the first detection of mass downsizing trends for both Mhpiv and M*piv. The pivot stellar mass decreases from M*piv=5.75e10 Msun at z=0.88 to M*piv=3.55e10Msun at z=0.37. Intriguingly, however, the corresponding evolution of Mhpiv leaves the pivot ratio constant with redshift at (Mh/M*)piv~27. Use simple arguments to show how this result raises the possibility that SF quenching may ultimately depend on Mh/M* and not simply Mh, as is commonly assumed. Show that simple models with such a dependence naturally lead to downsizing in the sites of SF. Finally, discuss the implications of realists in the context of popular quenching models, including disk instabilities and AGN feedback.
1107.4093
Galaxy-galaxy lensing constraints on the relation between baryon and dark matter in galaxies in the red sequence cluster survey 2
van Uitert, Hoekstra, Velander, Glibank, Gladders, Yee
Present the results of a study of WL by galaxies using image data that were obtained as part of RCS2. In order to compare to the baryonic properties of the lenses, focus on the ~300 sq deg that overlap with DR7 of SDSS. The depth and image quality of the RCS2 enables significantly to improve upon earlier work for luminous galaxies at z>=0.3. Comparison with dynamical masses from the SDSS shows a good correlation with the lensing mass for early-type galaxies. For low luminosity (stellar mass) early-type galaxies, find a satellite fraction of ~40% which rapidly decreases to <10% with increasing luminosity (stellar mass). The satellite fraction of the late-types has a value in the range 0-15%. Find that early-types in the range 1e10<L_r<1e11.5 Lsun have virial masses that are about five times higher than those of late-type galaxies and that the mass scales as M_200 ~ L^2.34. Also measure the viral M/L ratio, and find for L_200<1e11 Lsun a value of M200/L200=42 for early types, which increases for higher luminosities to values that are consistent with those observed for groups and clusters of galaxies. For late-type galaxies, find a lower value of M200/L200=17. Measurements also show that early- and late-type galaxies have comparable halo masses for stellar masses M*<1e11 Msun, whereas the virial masses of early-type galaxies are higher for higher stellar masses. Finally, determine the efficiency with which baryons have been converted into stars. Results for early-type galaxies suggest a variation in efficiency with a minimum of ~10% for a stellar mass M*,200=1e12 Msun. The results for the late-type galaxies are not well constrained, but do suggest a larger value.
1207.1120
Cosmological parameter constraints from galaxy-galaxy lensing and galaxy clustering with the SDSS DR7
Mandelbaum, Slosar, Baldauf, Seljak, Hirata, Nakajima, Reyes, Smith
Studies have show that the cross-correlation coefficient between galaxies and DM is very close to unity on scales outside a few virial radii of galaxy haloes, independent of the details of how galaxies populate DM haloes. The finding makes it possible to determine the DM clustering from measurements of GG WL and galaxy clustering. Present new cosmological parameter constraints banished on large-scale measurements of spectroscopic galaxy samples from SDSS DR7. Generalise the approach of Baldauf+2010 to remove small scale information (<2 and 4 Mpc/h for lensing and clustering measurements, respectively), where the cross-correlation coefficient differs from unity. Derive constraints for 3 galaxy samples covering 7131 sq deg, containing 69k, 62k, and 35k galaxies with mean z of 0.11, 0.28, 0.40. Clearly detect scale-dependent galaxy bias for the more luminous galaxy samples, at a level consistent with theoretical expectations. When vary both sigma_8 and Omega_m (and marginalize over NL galaxy bias) in a flat LCDM model, the best-constrained quantity is sigma_8(Omega_m/0.25)^0.57=0.80 (1sigma, stat+sys), where statistical and systematic errors have comparable contributions, and n_s=0.96 and h=0.7 are fixed. These strong constraints on the matter clustering suggest that this method is competitive with cosmic shear in current data, while having very complementary and in some ways less serous systematics. Therefore expect that this method will play a prominent role in future WL surveys. When combine these data with WMAP7 CMB data, constraints on sigma_8, Omega_m, H0, w_de and Sum m_nu become 30-80% tighter than with CMB data alone, since WL data break several parameter degeneracies.
1304.4265
CFHTLenS: the relation between galaxy dark matter haloes and baryons from weak gravitational lensing
Velander et al
Present a study of the relation between DM halo mass and the baryonic content of host galaxies, quantified via luminosity and stellar mass. Investigation uses 154 deg2 of CFHTLenS lensing and photometric data. Employ a gg lensing halo model which allows constraining the halo mass and satellite fraction. Analysis is limited to lenses at 0.2<z<0.4. Express the relationship between halo mass and baryonic observable as a power law. For the luminosity-halo mass relation, find a slope of 1.32pm0.06 and a normalization of 1.19pm0.06e13 Msun/h70 for red galaxies, while for blue galaxies the best-fit slope is 1.09pm0.15 and the normalization if 0.18pm0.04e13 Msun/h70. Similarly, find a best-fit slope of 1.36 and a normalization of 1.43pm0.1e13 Msun/h70 for the stellar mass-halo mass relation of red galaxies, while for blue galaxies the corresponding values are 0.98pm0.07 and 0.84pm0.2e13 Msun/h70. For red lenses, the fraction which are satellites tend to decrease with luminosity and stellar mass, with the sample being nearly all satellites for a stellar mass of 2e9 Msun/h70^2. The satellite fractions are generally close to zero for blue lenses, irrespective of luminosity of stellar mass. This, together with the shallower relation between halo mass and baryonic tracer, is a direct confirmation from gg lensing that blue galaxies reside in less clustered environments than red galaxies. Also find that the halo model, while matching the lensing signal around red lenses well, is prone to over-predicting the large-scale signal for faint and less massive blue lenses. This could be a further indication that these galaxies tend to be more isolated than assumed.
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