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Sample records for halo mass relation

  1. Halo mass - concentration relation from weak lensing

    CERN Document Server

    Mandelbaum, Rachel; Hirata, Christopher M

    2008-01-01

    We perform a statistical weak lensing analysis of dark matter profiles around tracers of halo mass from galactic- to cluster-size halos. In this analysis we use 170,640 isolated ~L* galaxies split into ellipticals and spirals, 38,236 groups traced by isolated spectroscopic Luminous Red Galaxies (LRGs) and 13,823 MaxBCG clusters from the Sloan Digital Sky Survey (SDSS) covering a wide range of richness. Together these three samples allow a determination of the density profiles of dark matter halos over three orders of magnitude in mass, from 10^{12} M_{sun} to 10^{15} M_{sun}. The resulting lensing signal is consistent with an NFW or Einasto profile on scales outside the central region. We find that the NFW concentration parameter c_{200b} decreases with halo mass, from around 10 for galactic halos to 4 for cluster halos. Assuming its dependence on halo mass in the form of c_{200b} = c_0 [M/(10^{14}M_{sun}/h)]^{\\beta}, we find c_0=4.6 +/- 0.7 (at z=0.22) and \\beta=0.13 +/- 0.07, with very similar results for t...

  2. Bent by baryons: the low mass galaxy-halo relation

    CERN Document Server

    Sawala, Till; Fattahi, Azadeh; Navarro, Julio F; Bower, Richard G; Crain, Robert A; Vecchia, Claudio Dalla; Furlong, Michelle; Jenkins, Adrian; McCarthy, Ian G; Qu, Yan; Schaller, Matthieu; Schaye, Joop; Theuns, Tom

    2014-01-01

    The relation between galaxies and dark matter halos is of vital importance for evaluating theoretical predictions of structure formation and galaxy formation physics. We show that the widely used method of abundance matching based on dark matter only simulations fails at the low mass end because two of its underlying assumptions are broken: only a small fraction of low mass (below 10^9.5 solar masses) halos host a visible galaxy, and halos grow at a lower rate due to the effect of baryons. In this regime, reliance on dark matter only simulations for abundance matching is neither accurate nor self-consistent. We find that the reported discrepancy between observational estimates of the halo masses of dwarf galaxies and the values predicted by abundance matching does not point to a failure of LCDM, but simply to a failure to account for baryonic effects. Our results also imply that the Local Group contains only a few hundred observable galaxies in contrast with the thousands of faint dwarfs that abundance matchi...

  3. A halo mass-concentration relation from weak lensing

    Energy Technology Data Exchange (ETDEWEB)

    Mandelbaum, Rachel [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Seljak, Uros [Institute for Theoretical Physics, University of Zurich, Zurich (Switzerland); Hirata, Christopher M, E-mail: rmandelb@ias.edu, E-mail: seljak@physik.unizh.ch, E-mail: chirata@tapir.caltech.edu [Mail Code 130-33, Caltech, Pasadena, CA 91125 (United States)

    2008-08-15

    We perform a statistical weak lensing analysis of dark matter profiles around tracers of halo mass from galaxy-size to cluster-size halos. In this analysis we use 170 640 isolated {approx}L{sub *} galaxies split into ellipticals and spirals, 38 236 groups traced via isolated spectroscopic luminous red galaxies and 13 823 maxBCG clusters from the Sloan Digital Sky Survey covering a wide range of richness. Together these three samples allow a determination of the density profiles of dark matter halos over three orders of magnitude in mass, from 10{sup 12}M{sub sun} to 10{sup 15}M{sub sun}. The resulting lensing signal is consistent with a Navarro-Frenk-White (NFW) or Einasto profile on scales outside the central region. In the inner regions, uncertainty in modeling of the proper identification of the halo center and inclusion of baryonic effects from the central galaxy make the comparison less reliable. We find that the NFW concentration parameter c{sub 200b} decreases with halo mass, from around 10 for galactic halos to 4 for cluster halos. Assuming its dependence on halo mass in the form of c{sub 200b}=c{sub 0} (M/10{sup 14}h{sup -1} M{sub sun}){sup -{beta}} we find c{sub 0} = 4.6 {+-} 0.7 (at z = 0.22) and {beta} = 0.13 {+-} 0.07, with very similar results for the Einasto profile. The slope ({beta}) is in agreement with theoretical predictions, while the amplitude is about two standard deviations below the predictions for this mass and redshift, but we note that the published values in the literature differ at a level of 10-20% and that for a proper comparison our analysis should be repeated in simulations. We compare our results to other recent determinations, some of which find significantly higher concentrations. We discuss the implications of our results for the baryonic effects on the shear power spectrum: since these are expected to increase the halo concentration, the fact that we see no evidence of high concentrations on scales above 20% of the virial

  4. The Mass-Concentration-Redshift Relation of Cold Dark Matter Halos

    CERN Document Server

    Ludlow, Aaron D; Angulo, Raul E; Boylan-Kolchin, Michael; Springel, Volker; Frenk, Carlos; White, Simon D M

    2013-01-01

    We use the Millennium Simulation series to investigate the mass and redshift dependence of the concentration of equilibrium cold dark matter (CDM) halos. We extend earlier work on the relation between halo mass profiles and assembly histories to show how the latter may be used to predict concentrations for halos of all masses and at any redshift. Our results clarify the link between concentration and the ``collapse redshift'' of a halo as well as why concentration depends on mass and redshift solely through the dimensionless ``peak height'' mass parameter, $\

  5. Organized Chaos: Scatter in the relation between stellar mass and halo mass in small galaxies

    CERN Document Server

    Garrison-Kimmel, Shea; Boylan-Kolchin, Michael; Bardwell, Emma

    2016-01-01

    We use Local Group galaxy counts together with the ELVIS N-body simulations to jointly constrain the scatter and slope in the stellar mass vs. halo mass relation at low masses, $M_\\star \\simeq 10^5 - 10^8 M_\\odot$. Assuming log-normal scatter about a median relation of the form $M_\\star \\propto M_{\\rm halo}^\\alpha$, the preferred log-slope steepens from $\\alpha \\simeq 1.8$ in the limit of zero scatter to $\\alpha \\simeq 2.6$ in the case of 2 dex of scatter in $M_\\star$ at fixed halo mass. We provide fitting functions for the best-fit relations as a function of scatter, including cases where the relation becomes increasingly stochastic with decreasing mass. We show that if the scatter at fixed halo mass is large enough ($\\gtrsim 1$ dex) and if the median relation is steep enough ($\\alpha \\gtrsim 2$), then the "too-big-to-fail" problem seen in the Local Group can be self-consistently eliminated in about $\\sim 5-10\\%$ of realizations. This scenario requires that the most massive subhalos host unobservable ultra-f...

  6. The origin of scatter in the stellar mass-halo mass relation of central galaxies in the EAGLE simulation

    Science.gov (United States)

    Matthee, Jorryt; Schaye, Joop; Crain, Robert A.; Schaller, Matthieu; Bower, Richard; Theuns, Tom

    2017-02-01

    We use the hydrodynamical EAGLE simulation to study the magnitude and origin of the scatter in the stellar mass-halo mass relation for central galaxies. We separate cause and effect by correlating stellar masses in the baryonic simulation with halo properties in a matched dark matter only (DMO) simulation. The scatter in stellar mass increases with redshift and decreases with halo mass. At z = 0.1, it declines from 0.25 dex at M200, DMO ≈ 1011 M⊙ to 0.12 dex at M200, DMO ≈ 1013 M⊙, but the trend is weak above 1012 M⊙. For M200, DMO halo concentration. At fixed halo mass, a larger stellar mass corresponds to a more concentrated halo. This is likely because higher concentrations imply earlier formation times and hence more time for accretion and star formation, and/or because feedback is less efficient in haloes with higher binding energies. The maximum circular velocity, Vmax, DMO, and binding energy are therefore more fundamental properties than halo mass, meaning that they are more accurate predictors of stellar mass, and we provide fitting formulae for their relations with stellar mass. However, concentration alone cannot explain the total scatter in the M_star - M_{200, DMO} relation, and it does not explain the scatter in Mstar-Vmax, DMO. Halo spin, sphericity, triaxiality, substructure and environment are also not responsible for the remaining scatter, which thus could be due to more complex halo properties or non-linear/stochastic baryonic effects.

  7. The Tully$-$Fisher and Mass$-$Size Relations from Halo Abundance Matching

    CERN Document Server

    Desmond, Harry

    2015-01-01

    The Tully$-$Fisher relation (TFR) expresses the connection between rotating galaxies and the dark matter haloes they inhabit, and therefore contains a wealth of information about galaxy formation. We construct a general framework to investigate whether models based on halo abundance matching are able to reproduce the observed stellar mass TFR and mass$-$size relation (MSR), and use the data to constrain galaxy formation parameters. Our model tests a range of plausible scenarios, differing in the response of haloes to disc formation, the relative angular momentum of baryons and dark matter, the impact of selection effects, and the abundance matching parameters. We show that agreement with the observed TFR puts an upper limit on the scatter between galaxy and halo properties, requires weak or reversed halo contraction, and favours selection effects that preferentially eliminate fast-rotating galaxies. The MSR constrains the ratio of the disc to halo specific angular momentum to be approximately in the range 0.6...

  8. Organized chaos: scatter in the relation between stellar mass and halo mass in small galaxies

    Science.gov (United States)

    Garrison-Kimmel, Shea; Bullock, James S.; Boylan-Kolchin, Michael; Bardwell, Emma

    2017-01-01

    We use Local Group galaxy counts together with the ELVIS N-body simulations to explore the relationship between the scatter and slope in the stellar mass versus halo mass relation at low masses, M⋆ ≃ 105-108 M⊙. Assuming models with lognormal scatter about a median relation of the form M_star ∝ M_halo^α, the preferred log-slope steepens from α ≃ 1.8 in the limit of zero scatter to α ≃ 2.6 in the case of 2 dex of scatter in M⋆ at fixed halo mass. We provide fitting functions for the best-fitting relations as a function of scatter, including cases where the relation becomes increasingly stochastic with decreasing mass. We show that if the scatter at fixed halo mass is large enough (≳ 1 dex) and if the median relation is steep enough (α ≳ 2), then the `too-big-to-fail' problem seen in the Local Group can be self-consistently eliminated in about ˜5-10 per cent of realizations. This scenario requires that the most massive subhaloes host unobservable ultra-faint dwarfs fairly often; we discuss potentially observable signatures of these systems. Finally, we compare our derived constraints to recent high-resolution simulations of dwarf galaxy formation in the literature. Though simulation-to-simulation scatter in M⋆ at fixed Mhalo is large among different authors (˜2 dex), individual codes produce relations with much less scatter and usually give relations that would overproduce local galaxy counts.

  9. DO NOT FORGET THE FOREST FOR THE TREES: THE STELLAR-MASS HALO-MASS RELATION IN DIFFERENT ENVIRONMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Tonnesen, Stephanie [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Cen, Renyue, E-mail: stonnes@gmail.com, E-mail: cen@astro.princeton.edu [Department of Astrophysics, Princeton University, Peyton Hall, Princeton, NJ 08544 (United States)

    2015-10-20

    The connection between dark matter halos and galactic baryons is often not well constrained nor well resolved in cosmological hydrodynamical simulations. Thus, halo occupation distribution models that assign galaxies to halos based on halo mass are frequently used to interpret clustering observations, even though it is well known that the assembly history of dark matter halos is related to their clustering. In this paper we use high-resolution hydrodynamical cosmological simulations to compare the halo and stellar mass growth of galaxies in a large-scale overdensity to those in a large-scale underdensity (on scales of about 20 Mpc). The simulation reproduces assembly bias, in which halos have earlier formation times in overdense environments than in underdense regions. We find that the ratio of stellar mass to halo mass is larger in overdense regions in central galaxies residing in halos with masses between 10{sup 11} and 10{sup 12.9} M{sub ⊙}. When we force the local density (within 2 Mpc) at z = 0 to be the same for galaxies in the large-scale over- and underdensities, we find the same results. We posit that this difference can be explained by a combination of earlier formation times, more interactions at early times with neighbors, and more filaments feeding galaxies in overdense regions. This result puts the standard practice of assigning stellar mass to halos based only on their mass, rather than considering their larger environment, into question.

  10. The stellar-to-halo mass relation for Local Group galaxies

    CERN Document Server

    Brook, C B; Knebe, A; Gottlöber, S; Hoffman, Y; Yepes, G

    2013-01-01

    We contend that a single power law halo mass distribution is appropriate for direct matching to the stellar masses of observed Local Group dwarf galaxies, allowing the determination of the slope of the stellar mass-halo mass relation for low mass galaxies. Errors in halo masses are well defined as the Poisson noise of simulated local group realisations, which we determine using constrained local universe simulations (CLUES). For the stellar mass range 10$^7$mass-halo mass relation follows a power law with slope of 3.1, significantly steeper than most values in the literature. The steep relation between stellar and halo masses indicates that Local Group dwarf galaxies are hosted by dark matter halos with a small range of mass. Our methodology is robust down to the stellar mass to which the census of observed Local Group galaxies is complete, highlighting the importance of pushing the completenes...

  11. Don't Forget the Forest for the Trees: The Stellar-Mass Halo-Mass Relation in Different Environments

    CERN Document Server

    Tonnesen, Stephanie

    2015-01-01

    The connection between dark matter halos and galactic baryons is often not well-constrained nor well-resolved in cosmological hydrodynamical simulations. Thus, Halo Occupation Distribution (HOD) models that assign galaxies to halos based on halo mass are frequently used to interpret clustering observations, even though it is well-known that the assembly history of dark matter halos is related to their clustering. In this paper we use high-resolution hydrodynamical cosmological simulations to compare the halo and stellar mass growth of galaxies in a large-scale overdensity to those in a large-scale underdensity (on scales of about 20 Mpc). The simulation reproduces assembly bias, that halos have earlier formation times in overdense environments than in underdense regions. We find that the stellar mass to halo mass ratio is larger in overdense regions in central galaxies residing in halos with masses between 10$^{11}$-10$^{12.9}$ M$_{\\odot}$. When we force the local density (within 2 Mpc) at z=0 to be the same ...

  12. The core-halo mass relation of ultra-light axion dark matter from merger history

    CERN Document Server

    Du, Xiaolong; Niemeyer, Jens C; Schwabe, Bodo

    2016-01-01

    In the context of structure formation with ultra-light axion dark matter, we offer an alternative explanation for the mass relation of solitonic cores and their host halos observed in numerical simulations. Our argument is based entirely on the mass gain that occurs during major mergers of binary cores and largely independent of the initial core-halo mass relation assigned to hosts that have just collapsed. We find a relation between the halo mass $M_h$ and corresponding core mass $M_c$, $M_c\\propto M_h^{2\\beta-1}$, where $(1-\\beta)$ is the core mass loss fraction. Following the evolution of core masses in stochastic merger trees, we find empirical evidence for our model. Our results are useful for statistically modeling the effects of dark matter cores on the properties of galaxies and their substructures in axion dark matter cosmologies.

  13. The Mass-Concentration-Redshift Relation of Cold and Warm Dark Matter Halos

    CERN Document Server

    Ludlow, Aaron D; Angulo, Raúl E; Wang, Lan; Hellwing, Wojciech A; Navarro, Julio F; Cole, Shaun; Frenk, Carlos S

    2016-01-01

    We use a suite of cosmological simulations to study the mass-concentration-redshift relation, $c({\\rm M},z)$, of dark matter halos assembled hierarchically. Our runs include both standard $\\Lambda$-cold dark matter (CDM) models, as well as several additional simulations with sharply truncated density fluctuation power spectra, such as those expected in a thermal warm dark matter (WDM) scenario. As in earlier work, we find that the mass profiles of CDM and WDM halos are self-similar and well approximated by the Navarro-Frenk-White (NFW) profile. The $c({\\rm M},z)$ relation of CDM halos is monotonic: concentrations decrease with increasing virial mass at fixed redshift, and decrease with increasing redshift at fixed mass. The main-progenitor mass accretion histories (MAHs) of CDM halos are also scale-free, a result that has been used to infer halo concentrations directly from MAHs. These results do not apply to WDM halos: their MAHs are not scale-free because of the characteristic scale imposed by the power-spe...

  14. The origin of scatter in the stellar mass - halo mass relation of central galaxies in the EAGLE simulation

    CERN Document Server

    Matthee, Jorryt; Crain, Robert A; Schaller, Matthieu; Bower, Richard; Theuns, Tom

    2016-01-01

    We use the hydrodynamical EAGLE simulation to study the magnitude and origin of the scatter in the stellar mass - halo mass relation for central galaxies. We separate cause and effect by correlating stellar masses in the baryonic simulation with halo properties in a matched dark matter only (DMO) simulation. The scatter in stellar mass increases with redshift and decreases with halo mass. At $z = 0.1$ it declines from 0.25 dex at $M_{200, \\rm DMO} \\approx 10^{11}$ M$_{\\odot}$ to 0.12 dex at $M_{200, \\rm DMO} \\approx 10^{13}$ M$_{\\odot}$, but the trend is weak above $10^{12}$ M$_{\\odot}$. For $M_{200, \\rm DMO} < 10^{12.5}$ M$_{\\odot}$ up to 0.04 dex of the scatter is due to scatter in the halo concentration. At fixed halo mass, a larger stellar mass corresponds to a more concentrated halo. This is likely because higher concentrations imply earlier formation times and hence more time for accretion and star formation, and/or because feedback is less efficient in haloes with higher binding energies. The maximu...

  15. The stellar-to-halo mass relations of local galaxies segregated by color

    CERN Document Server

    Rodriguez-Puebla, A; Yang, X; Foucaud, S; Drory, N; Jing, Y P

    2014-01-01

    We derive the stellar-to-halo mass relations, SHMR, of local blue and red central galaxies separately, as well as the fraction of halos hosting blue/red central galaxies. We find that: 1) the SHMR of central galaxies is segregated by color, with blue centrals having a SHMR above the one of red centrals; at logMh~12, the Ms/Mh ratio of the blue centrals is ~0.05, which is ~1.7 times larger than the value of red centrals. 2) The intrinsic scatters of the SHMRs of red and blue centrals are ~0.14 and ~0.11dex, respectively. The intrinsic scatter of the average SHMR of all central galaxies changes from ~0.20dex to ~0.14dex in the 11.3halos hosting blue centrals at Mh=1E11Msun is 87%, but at 2x1E12Msun decays to ~20%, approaching to a few per cents at higher masses. The characteristic mass at which this fraction is the same for blue and red galaxies is Mh~7x1E11Msun. Our results suggest that the SHMR of central galaxies at large masses is shaped by halo mass quenching (like...

  16. Reproducing the Stellar Mass/Halo Mass Relation in Simulated LCDM Galaxies: Theory vs Observational Estimates

    CERN Document Server

    Munshi, Ferah; Brooks, A M; Christensen, C; Shen, S; Loebman, S; Moster, B; Quinn, T; Wadsley, J

    2012-01-01

    We examine the present-day total stellar-to-halo mass (SHM) ratio as a function of halo mass for a new sample of simulated field galaxies using fully cosmological, LCDM, high resolution SPH + N-Body simulations.These simulations include an explicit treatment of metal line cooling, dust and self-shielding, H2 based star formation and supernova driven gas outflows. The 18 simulated halos have masses ranging from a few times 10^8 to nearly 10^12 solar masses. At z=0 our simulated galaxies have a baryon content and morphology typical of field galaxies. Over a stellar mass range of 2.2 x 10^3 to 4.5 x 10^10 solar masses, we find extremely good agreement between the SHM ratio in simulations and the present-day predictions from the statistical Abundance Matching Technique presented in Moster et al. (2012). This improvement over past simulations is due to a number systematic factors, each decreasing the SHM ratios: 1) gas outflows that reduce the overall SF efficiency but allow for the formation of a cold gas compone...

  17. The Halo Occupation Distribution Towards an Empirical Determination of the Relation Between Galaxies and Mass

    CERN Document Server

    Berlind, Andreas A; Berlind, Andreas A.; Weinberg, David H.

    2002-01-01

    We investigate galaxy bias in the framework of the ``Halo Occupation Distribution'' (HOD), which defines the bias of a population of galaxies by the conditional probability P(N|M) that a dark matter halo of virial mass M contains N galaxies, together with prescriptions that specify the relative spatial and velocity distributions of galaxies and dark matter within halos. By populating the halos of a cosmological N-body simulation using a variety of HOD models, we examine the sensitivity of different galaxy clustering statistics to properties of the HOD. The galaxy correlation function responds to different aspects of P(N|M) on different scales. Obtaining the observed power-law form of xi(r) requires rather specific combinations of HOD parameters, implying a strong constraint on the physics of galaxy formation; the success of numerical and semi-analytic models in reproducing this form is entirely non-trivial. Other clustering statistics such as the galaxy-mass correlation function, the bispectrum, the void prob...

  18. THE STELLAR MASS–HALO MASS RELATION FOR LOW-MASS X-RAY GROUPS AT 0.5< z< 1 IN THE CDFS WITH CSI

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Shannon G.; Kelson, Daniel D.; Williams, Rik J.; Mulchaey, John S.; Dressler, Alan; McCarthy, Patrick J.; Shectman, Stephen A., E-mail: patel@obs.carnegiescience.edu [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2015-01-30

    Since z∼1, the stellar mass density locked in low-mass groups and clusters has grown by a factor of ∼8. Here, we make the first statistical measurements of the stellar mass content of low-mass X-ray groups at 0.5halo mass scales for wide-field optical and infrared surveys. Groups are selected from combined Chandra and XMM-Newton X-ray observations in the Chandra Deep Field South. These ultra-deep observations allow us to identify bona fide low-mass groups at high redshift and enable measurements of their total halo masses. We compute aggregate stellar masses for these halos using galaxies from the Carnegie-Spitzer-IMACS (CSI) spectroscopic redshift survey. Stars comprise ∼3%–4% of the total mass of group halos with masses 10{sup 12.8}mass of Fornax and one-fiftieth the mass of Virgo). Complementing our sample with higher mass halos at these redshifts, we find that the stellar-to-halo mass ratio decreases toward higher halo masses, consistent with other work in the local and high redshift universe. The observed scatter about the stellar–halo mass relation is σ∼0.25 dex, which is relatively small and suggests that total group stellar mass can serve as a rough proxy for halo mass. We find no evidence for any significant evolution in the stellar–halo mass relation since z≲1. Quantifying the stellar content in groups since this epoch is critical given that hierarchical assembly leads to such halos growing in number density and hosting increasing shares of quiescent galaxies.

  19. Projection Of The Stellar To Halo Mass Relation Into The Scaling Relations Of A Disc Galaxy Population

    Science.gov (United States)

    Mancillas, Brisa; Ávila-Reese, Vladimir; Rodríguez-Puebla, Aldo; Valls-Gabaud, David

    2017-06-01

    Several pieces of evidence suggest that disk formation is the generic process of assembly of galaxies, while the spheroidal component arises from the merging/interactions of disks as well as from their secular evolution. To understand galaxy formation and evolution, a cosmological framework is required. The current cosmological paradigm is summarized in the so-called Λ-cold dark matter model (ΛCDM). The statistical connection between the masses of the observed galaxies and those of the simulated CDM halos in large volumes leads us to the galaxy-halo mass relation, which summarizes the main astrophysical processes of galaxy formation and evolution (gas heating and cooling, SF, SN- and AGN-driven feedback, etc.). An important question is how this relation constrained by semi-empirical methods (e.g., Rodriguez-Puebla et al. 2014) is "projected" into the disk galaxy scaling relations and other galaxy correlations. To explore this question, we generate a synthetic catalog of thousands of disk/halo systems by means of an extended Mo, Mao & White (1998) model, and by using as input the baryonic-to-halo mass relation, fbar(Mh), of local disk galaxy as recently constrained by Calette et al. (2015).

  20. Constraining the H i–Halo Mass Relation from Galaxy Clustering

    Science.gov (United States)

    Guo, Hong; Li, Cheng; Zheng, Zheng; Mo, H. J.; Jing, Y. P.; Zu, Ying; Lim, S. H.; Xu, Haojie

    2017-09-01

    We study the dependence of galaxy clustering on H i mass using ∼16,000 galaxies with redshift in the range of 0.0025 {10}8 {M}ȯ , drawn from the 70% complete sample of the Arecibo Legacy Fast ALFA survey. We construct subsamples of galaxies with {M}{{H}{{I}}} above different thresholds and make volume-limited clustering measurements in terms of three statistics: the projected two-point correlation function, the projected cross-correlation function with respect to a reference sample, and the redshift-space monopole moment. In contrast to previous studies, which found no/weak H i mass dependence, we find both the clustering amplitudes on scales above a few megaparsecs and the bias factors to increase significantly with increasing H i mass for {M}{{H}{{I}}}> {10}9 {M}ȯ . For H i mass thresholds below ∼ {10}9 {M}ȯ , the inferred galaxy bias factors are systematically lower than the minimum halo bias from mass-selected halo samples. We extend the simple halo model, in which the galaxy content is only determined by halo mass, by including the halo formation time as an additional parameter. A model that puts H i-rich galaxies into halos that formed late can reproduce the clustering measurements reasonably well. We present the implications of our best-fitting model on the correlation of H i mass with halo mass and formation time, as well as the halo occupation distributions and H i mass functions for central and satellite galaxies. These results are compared with the predictions from semianalytic galaxy formation models and hydrodynamic galaxy formation simulations.

  1. The accretion history of dark matter haloes - III. A physical model for the concentration-mass relation

    Science.gov (United States)

    Correa, Camila A.; Wyithe, J. Stuart B.; Schaye, Joop; Duffy, Alan R.

    2015-09-01

    We present a semi-analytic, physically motivated model for dark matter halo concentration as a function of halo mass and redshift. The semi-analytic model combines an analytic model for the halo mass accretion history (MAH), based on extended Press-Schechter (EPS) theory, with an empirical relation between concentration and formation time obtained through fits to the results of numerical simulations. Because the semi-analytic model is based on EPS theory, it can be applied to wide ranges in mass, redshift and cosmology. The resulting concentration-mass (c-M) relations are found to agree with the simulations, and because the model applies only to relaxed haloes, they do not exhibit the upturn at high masses or high redshifts found by some recent works. We predict a change of slope in the z ˜ 0 c-M relation at a mass-scale of 1011 M⊙. We find that this is due to the change in the functional form of the halo MAH, which goes from being dominated by an exponential (for high-mass haloes) to a power law (for low-mass haloes). During the latter phase, the core radius remains approximately constant, and the concentration grows due to the drop of the background density. We also analyse how the c-M relation predicted by this work affects the power produced by dark matter annihilation, finding that at z = 0 the power is two orders of magnitude lower than that obtained from extrapolating best-fitting c-M relations. We provide fits to the c-M relations as well as numerical routines to compute concentrations and MAHs.†

  2. Reionization histories of Milky Way mass halos

    Energy Technology Data Exchange (ETDEWEB)

    Li, Tony Y.; Wechsler, Risa H.; Abel, Tom [Kavli Institute for Particle Astrophysics and Cosmology, Physics Department, Stanford University, Stanford, CA 94305 (United States); Alvarez, Marcelo A., E-mail: tonyyli@stanford.edu, E-mail: rwechsler@stanford.edu, E-mail: tabel@stanford.edu, E-mail: malvarez@cita.utoronto.ca [CITA, University of Toronto, Toronto, Ontario M5S 3H8 (Canada)

    2014-04-20

    We investigate the connection between the reionization era and the present-day universe by examining the mass reionization histories of z = 0 dark matter halos. In a 600{sup 3} Mpc{sup 3} volume, we combine a dark matter N-body simulation with a three-dimensional seminumerical reionization model. This tags each particle with a reionization redshift, so that individual present-day halos can be connected to their reionization histories and environments. We find that the vast majority of present-day halos with masses larger than ∼ few × 10{sup 11} M {sub ☉} reionize earlier than the rest of the universe. We also find significant halo-to-halo diversity in mass reionization histories, and find that in realistic inhomogeneous models, the material within a given halo is not expected to reionize at the same time. In particular, the scatter in reionization times within individual halos is typically larger than the scatter among halos. From our fiducial reionization model, we find that the typical 68% scatter in reionization times within halos is ∼115 Myr for 10{sup 12±0.25} M {sub ☉} halos, decreasing slightly to ∼95 Myr for 10{sup 15±0.25} M {sub ☉} halos. We find a mild correlation between reionization history and environment: halos with shorter reionization histories are typically in more clustered environments, with the strongest trend on a scale of ∼20 Mpc. Material in Milky Way mass halos with short reionization histories is preferentially reionized in relatively large H II regions, implying reionization mostly by sources external to the progenitors of the present-day halo. We investigate the impact on our results of varying the reionization model parameters, which span a range of reionization scenarios with varying timing and morphology.

  3. Planck Intermediate Results. XI: The gas content of dark matter halos: the Sunyaev-Zeldovich-stellar mass relation for locally brightest galaxies

    DEFF Research Database (Denmark)

    Planck Collaboration,; Ade, P. A. R.; Aghanim, N.;

    2013-01-01

    gas, and that this gas must be less concentrated than the dark matter in such halos in order to remain consistent with X-ray observations. At the high-mass end, the measured SZ signal is 20% lower than found from observations of X-ray clusters, a difference consistent with Malmquist bias effects......We present the scaling relation between Sunyaev-Zeldovich (SZ) signal and stellar mass for almost 260,000 locally brightest galaxies (LBGs) selected from the Sloan Digital Sky Survey (SDSS). These are predominantly the central galaxies of their dark matter halos. We calibrate the stellar-to-halo...... indication of signal at even lower stellar mass. We derive the scaling relation between SZ signal and halo mass by assigning halo properties from our mock catalogues to the real LBGs and simulating the Planck observation process. This relation shows no evidence for deviation from a power law over a halo mass...

  4. The accretion history of dark matter halos III: A physical model for the concentration-mass relation

    CERN Document Server

    Correa, Camila A; Schaye, Joop; Duffy, Alan R

    2015-01-01

    We present a semi-analytic, physically motivated model for dark matter halo concentration as a function of halo mass and redshift. The semi-analytic model is intimately based on hierarchical structure formation. It uses an analytic model for the halo mass accretion history, based on extended Press Schechter (EPS) theory, and an empirical relation between concentration and an appropriate definition of formation time obtained through fits to the results of numerical simulations. The resulting concentration-mass relations are tested against the simulations and do not exhibit an upturn at high masses or high redshifts as claimed by recent works. Because our semi-analytic model is based on EPS theory, it can be applied to wide ranges in mass, redshift and cosmology. We predict a change of slope in the z=0 concentration-mass relation at a mass scale of $10^{11}\\rm{M}_{\\odot}$, that is caused by the varying power in the density perturbations. We provide best-fitting expressions of the $c-M$ relations as well as nume...

  5. The Stellar Mass - Halo Mass Relation for Low Mass X-ray Groups at 0.5

    CERN Document Server

    Patel, Shannon G; Williams, Rik J; Mulchaey, John S; Dressler, Alan; McCarthy, Patrick J; Shectman, Stephen A

    2015-01-01

    Since z~1, the stellar mass density locked in low mass groups and clusters has grown by a factor of ~8. Here we make the first statistical measurements of the stellar mass content of low mass X-ray groups at 0.5halo mass scales for wide-field optical and infrared surveys. Groups are selected from combined Chandra and XMM-Newton X-ray observations in the Chandra Deep Field South (CDFS). These ultra-deep observations allow us to identify bona fide low mass groups at high redshift and enable measurements of their total halo masses. We compute aggregate stellar masses for these halos using galaxies from the Carnegie-Spitzer-IMACS (CSI) spectroscopic redshift survey. Stars comprise ~3-4% of the total mass of group halos with masses 10^{12.8}mass of Fornax and 1/50th the mass of Virgo). Complementing our sample with higher mass halos at these redshifts, we find that the stellar-to-halo mass ratio decreases toward higher halo ma...

  6. The stellar-to-halo mass relation of GAMA galaxies from 100 square degrees of KiDS weak lensing data

    CERN Document Server

    van Uitert, Edo; Hoekstra, Henk; Brouwer, Margot; Sifón, Cristóbal; Viola, Massimo; Baldry, Ivan; Bland-Hawthorn, Joss; Brough, Sarah; Brown, M J I; Choi, Ami; Driver, Simon P; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Joachimi, Benjamin; Kuijken, Konrad; Liske, Jochen; Loveday, Jon; McFarland, John; Miller, Lance; Nakajima, Reiko; Peacock, John; Radovich, Mario; Robotham, A S G; Schneider, Peter; Sikkema, Gert; Taylor, Edward N; Kleijn, Gijs Verdoes

    2016-01-01

    We study the stellar-to-halo mass relation of central galaxies in the range 9.75x10^10 h^-2 M_sun, the stellar mass increases with halo mass as ~M_h^0.25. The ratio of dark matter to stellar mass has a minimum at a halo mass of 8x10^11 h^-1 M_sun with a value of M_h/M_*=56_-10^+16 [h]. We also use the GAMA group catalogue to select centrals and satellites in groups with five or more members, which trace regions in space where the local matter density is higher than average, and determine for the first time the stellar-to-halo mass relation in these denser environments. We find no significant differences compared to the relation from the full sample, which suggests that the stellar-to-halo mass relation does not vary strongly with local density. Furthermore, we find that the stellar-to-halo mass relation of central galaxies can also be obtained by modelling the lensing signal and stellar mass function of satellite galaxies only, which shows that the assumptions to model the satellite contribution in the halo m...

  7. A weak gravitational lensing recalibration of the scaling relations linking the gas properties of dark halos to their mass

    CERN Document Server

    Wang, Wenting; Mandelbaum, Rachel; Henriques, Bruno; Anderson, Michael E; Han, Jiaxin

    2015-01-01

    We use weak gravitational lensing to measure mean mass profiles around Locally Brightest Galaxies (LBGs). These are selected from the SDSS/DR7 spectroscopic and photometric catalogues to be brighter than any neighbour projected within 1.0 Mpc and differing in redshift by $ 83\\%$) are expected to be the central galaxies of their dark matter halos. Previous stacking analyses have used this LBG sample to measure mean Sunyaev-Zeldovich flux and mean X-ray luminosity as a function of LBG stellar mass. In both cases, a simulation of the formation of the galaxy population was used to estimate effective halo mass for LBGs of given stellar mass, allowing the derivation of scaling relations between the gas properties of halos and their mass. By comparing results from a variety of simulations to our lensing data, we show that this procedure has significant model dependence reflecting: (i) the failure of any given simulation to reproduce observed galaxy abundances exactly; (ii) a dependence on the cosmology underlying th...

  8. ON THE INTERMEDIATE-REDSHIFT CENTRAL STELLAR MASS-HALO MASS RELATION, AND IMPLICATIONS FOR THE EVOLUTION OF THE MOST MASSIVE GALAXIES SINCE z ∼ 1

    Energy Technology Data Exchange (ETDEWEB)

    Shankar, Francesco; Buchan, Stewart [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); Guo, Hong; Zheng, Zheng [Department of Physics and Astronomy, University of Utah, UT 84112 (United States); Bouillot, Vincent [Centre for Astrophysics, Cosmology and Gravitation, Department of Mathematics and Applied Mathematics, University of Cape Town, Cape Town 7701 (South Africa); Rettura, Alessandro [Jet Propulsion Laboratory, California Institute of Technology, MS 169-234, Pasadena, CA 91109 (United States); Meert, Alan; Bernardi, Mariangela; Sheth, Ravi; Vikram, Vinu [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Kravtsov, Andrey [Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637 (United States); Marchesini, Danilo [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Behroozi, Peter [Kavli Institute for Particle Astrophysics and Cosmology, Stanford, CA 94305 (United States); Maraston, Claudia; Capozzi, Diego [Institute of Cosmology and Gravitation, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX (United Kingdom); Ascaso, Begoña; Huertas-Company, Marc [GEPI, Observatoire de Paris, CNRS, Univ. Paris Diderot, 5 Place Jules Janssen, F-92195 Meudon (France); Lemaux, Brian C. [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Gal, Roy R. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Lubin, Lori M., E-mail: F.Shankar@soton.ac.uk [University of California, One Shields Avenue, Davis, CA 95616 (United States); and others

    2014-12-20

    The stellar mass-halo mass relation is a key constraint in all semi-analytic, numerical, and semi-empirical models of galaxy formation and evolution. However, its exact shape and redshift dependence remain under debate. Several recent works support a relation in the local universe steeper than previously thought. Based on comparisons with a variety of data on massive central galaxies, we show that this steepening holds up to z ∼ 1 for stellar masses M {sub star} ≳ 2 × 10{sup 11} M {sub ☉}. Specifically, we find significant evidence for a high-mass end slope of β ≳ 0.35-0.70 instead of the usual β ≲ 0.20-0.30 reported by a number of previous results. When including the independent constraints from the recent Baryon Oscillation Spectroscopic Survey clustering measurements, the data, independent of any systematic errors in stellar masses, tend to favor a model with a very small scatter (≲ 0.15 dex) in stellar mass at fixed halo mass, in the redshift range z < 0.8 and for M {sub star} > 3 × 10{sup 11} M {sub ☉}, suggesting a close connection between massive galaxies and host halos even at relatively recent epochs. We discuss the implications of our results with respect to the evolution of the most massive galaxies since z ∼ 1.

  9. Halo mass distribution reconstruction across the cosmic web

    CERN Document Server

    Zhao, Cheng; Chuang, Chia-Hsun; Prada, Francisco; Yepes, Gustavo; Tao, Charling

    2015-01-01

    We study the relation between halo mass and its environment from a probabilistic perspective. We find that halo mass depends not only on local dark matter density, but also on non-local quantities such as the cosmic web environment and the halo-exclusion effect. Given these accurate relations, we have developed the HADRON-code (Halo mAss Distribution ReconstructiON), a technique which permits us to assign halo masses to a distribution of haloes in three-dimensional space. This can be applied to the fast production of mock galaxy catalogues, by assigning halo masses, and reproducing accurately the bias for different mass cuts. The resulting clustering of the halo populations agree well with that drawn from the BigMultiDark $N$-body simulation: the power spectra are within 1-$\\sigma$ up to scales of $k=0.2\\,h\\,{\\rm Mpc}^{-1}$, when using augmented Lagrangian perturbation theory based mock catalogues. Only the most massive haloes show a larger deviation. For these, we find evidence of the halo-exclusion effect. ...

  10. Accurate mass and velocity functions of dark matter haloes

    Science.gov (United States)

    Comparat, Johan; Prada, Francisco; Yepes, Gustavo; Klypin, Anatoly

    2017-08-01

    N-body cosmological simulations are an essential tool to understand the observed distribution of galaxies. We use the MultiDark simulation suite, run with the Planck cosmological parameters, to revisit the mass and velocity functions. At redshift z = 0, the simulations cover four orders of magnitude in halo mass from ˜1011M⊙ with 8783 874 distinct haloes and 532 533 subhaloes. The total volume used is ˜515 Gpc3, more than eight times larger than in previous studies. We measure and model the halo mass function, its covariance matrix w.r.t halo mass and the large-scale halo bias. With the formalism of the excursion-set mass function, we explicit the tight interconnection between the covariance matrix, bias and halo mass function. We obtain a very accurate (model of the distinct halo mass function. We also model the subhalo mass function and its relation to the distinct halo mass function. The set of models obtained provides a complete and precise framework for the description of haloes in the concordance Planck cosmology. Finally, we provide precise analytical fits of the Vmax maximum velocity function up to redshift z occupation distribution using Vmax. The data and the analysis code are made publicly available in the Skies and Universes data base.

  11. Planck Intermediate Results. XI: The gas content of dark matter halos: the Sunyaev-Zeldovich-stellar mass relation for locally brightest galaxies

    CERN Document Server

    Ade, P A R; Arnaud, M; Ashdown, M; Atrio-Barandela, F; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Barrena, R; Bartlett, J G; Battaner, E; Benabed, K; Bernard, J -P; Bersanelli, M; Bikmaev, I; Böhringer, H; Bonaldi, A; Bond, J R; Borrill, J; Bouchet, F R; Bourdin, H; Burenin, R; Burigana, C; Butler, R C; Chamballu, A; Chary, R -R; Chiang, L -Y; Chon, G; Christensen, P R; Clements, D L; Colafrancesco, S; Colombi, S; Colombo, L P L; Comis, B; Coulais, A; Crill, B P; Cuttaia, F; Da Silva, A; Dahle, H; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Démoclès, J; Diego, J M; Dole, H; Donzelli, S; Doré, O; Douspis, M; Dupac, X; Enßlin, T A; Finelli, F; Flores-Cacho, I; Frailis, M; Franceschi, E; Frommert, M; Galeotta, S; Ganga, K; Génova-Santos, R T; Giard, M; Giraud-Héraud, Y; González-Nuevo, J; Górski, K M; Gregorio, A; Gruppuso, A; Hansen, F K; Harrison, D; Hernández-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Hobson, M; Holmes, W A; Hornstrup, A; Hovest, W; Huffenberger, K M; Hurier, G; Jaffe, T R; Jaffe, A H; Jones, W C; Juvela, M; Keihänen, E; Keskitalo, R; Khamitov, I; Kisner, T S; Kneissl, R; Knoche, J; Kunz, M; Kurki-Suonio, H; Lähteenmäki, A; Lamarre, J -M; Lasenby, A; Lawrence, C R; Jeune, M Le; Leonardi, R; Lilje, P B; Linden-Vørnle, M; López-Caniego, M; Lubin, P M; Luzzi, G; Macías-Pérez, J F; MacTavish, C J; Maffei, B; Maino, D; Mandolesi, N; Maris, M; Marleau, F; Marshall, D J; Martínez-González, E; Masi, S; Massardi, M; Matarrese, S; Mazzotta, P; Mei, S; Melchiorri, A; Melin, J -B; Mendes, L; Mennella, A; Mitra, S; Miville-Deschênes, M -A; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Munshi, D; Murphy, J A; Naselsky, P; Nati, F; Natoli, P; Nørgaard-Nielsen, H U; Noviello, F; Novikov, D; Novikov, I; Osborne, S; Oxborrow, C A; Pajot, F; Paoletti, D; Perotto, L; Perrotta, F; Piacentini, F; Piat, M; Pierpaoli, E; Piffaretti, R; Plaszczynski, S; Pointecouteau, E; Polenta, G; Popa, L; Poutanen, T; Pratt, G W; Prunet, S; Puget, J -L; Rachen, J P; Rebolo, R; Reinecke, M; Remazeilles, M; Renault, C; Ricciardi, S; Ristorcelli, I; Rocha, G; Roman, M; Rosset, C; Rossetti, M; Rubiño-Martín, J A; Rusholme, B; Sandri, M; Savini, G; Scott, D; Spencer, L; Starck, J -L; Stolyarov, V; Sudiwala, R; Sunyaev, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Valenziano, L; Van Tent, B; Vielva, P; Villa, F; Vittorio, N; Wade, L A; Wandelt, B D; Wang, W; Welikala, N; Weller, J; White, S D M; White, M; Zacchei, A; Zonca, A

    2012-01-01

    We present the scaling relation between Sunyaev-Zeldovich (SZ) signal and stellar mass for almost 260,000 locally brightest galaxies (LBGs) selected from the Sloan Digital Sky Survey (SDSS). These are predominantly the central galaxies of their dark matter halos. We calibrate the stellar-to-halo mass conversion using realistic mock catalogues based on the Millennium Simulation. Applying a multi-frequency matched filter to the Planck data for each LBG, and averaging the results in bins of stellar mass, we measure the mean SZ signal down to $M_\\ast\\sim 2\\times 10^{11} \\Msolar$, with a clear indication of signal at even lower stellar mass. We derive the scaling relation between SZ signal and halo mass by assigning halo properties from our mock catalogues to the real LBGs and simulating the Planck observation process. This relation shows no evidence for deviation from a power law over a halo mass range extending from rich clusters down to $M_{500}\\sim 2\\times 10^{13} \\Msolar$, and there is a clear indication of s...

  12. The stellar mass-halo mass relation of isolated field dwarfs: a critical test of $\\Lambda$CDM at the edge of galaxy formation

    CERN Document Server

    Read, J I; Agertz, O; Fraternali, F

    2016-01-01

    We fit the rotation curves of isolated dwarf galaxies to directly measure the stellar mass-halo mass relation ($M_*-M_{200}$) over the mass range $5 \\times 10^5 < M_{*}/{\\rm M}_\\odot < 10^{8}$. By accounting for cusp-core transformations due to stellar feedback, we find a monotonic relation with remarkably little scatter. Such monotonicity implies that abundance matching should yield a similar $M_*-M_{200}$ if the cosmological model is correct. Using the 'field galaxy' stellar mass function from the Sloan Digital Sky Survey (SDSS) and the halo mass function from the $\\Lambda$ Cold Dark Matter Bolshoi simulation, we find remarkable agreement between the two. This holds down to $M_{200} \\sim 5 \\times 10^9$ M$_\\odot$, and to $M_{200} \\sim 5 \\times 10^8$ M$_\\odot$ if we assume a power law extrapolation of the SDSS stellar mass function below $M_* \\sim 10^7$ M$_\\odot$. However, if instead of SDSS we use the stellar mass function of nearby galaxy groups, then the agreement is poor. This occurs because the gro...

  13. Mass Function of Low Mass Dark Halos

    CERN Document Server

    Yahagi, H; Yoshii, Y; Yahagi, Hideki; Nagashima, Masahiro; Yoshii, Yuzuru

    2004-01-01

    The mass function of dark halos in a Lambda-dominated cold dark matter (LambdaCDM) universe is investigated. 529 output files from five runs of N-body simulations are analyzed using the friends-of-friends cluster finding algorithm. All the runs use 512^3 particles in the box size of 35 h^{-1}Mpc to 140 h^{-1}Mpc. Mass of particles for 35 h^{-1} Mpc runs is 2.67 times 10^7 h^{-1} M_{solar}. Because of the high mass resolution of our simulations, the multiplicity function in the low-mass range, where the mass is well below the characteristic mass and $\

  14. Evolution of the luminosity-to-halo mass relation of LRGs from a combined SDSS-DR10+RCS2 analysis

    CERN Document Server

    van Uitert, Edo; Hoekstra, Henk; Herbonnet, Ricardo

    2015-01-01

    We study the evolution of the luminosity-to-halo mass relation of Luminous Red Galaxies (LRGs). We select a sample of 52 000 LOWZ and CMASS LRGs from the Baryon Oscillation Spectroscopic Survey (BOSS) SDSS-DR10 in the ~450 deg^2 that overlaps with imaging data from the second Red-sequence Cluster Survey (RCS2), group them into bins of absolute magnitude and redshift and measure their weak lensing signals. The source redshift distribution has a median of 0.7, which allows us to study the lensing signal as a function of lens redshift. We interpret the lensing signal using a halo model, from which we obtain the halo masses as well as the normalisations of the mass-concentration relations. We find that the concentration of haloes that host LRGs is consistent with dark matter only simulations once we allow for miscentering or satellites in the modelling. The slope of the luminosity-to-halo mass relation has a typical value of 1.4 and does not change with redshift, but we do find evidence for a change in amplitude:...

  15. The evolution of the stellar mass versus halo mass relationship

    CERN Document Server

    Mitchell, Peter; Baugh, Carlton; Cole, Shaun

    2015-01-01

    We present an analysis of the predictions made by the Galform semi-analytic galaxy formation model for the evolution of the relationship between stellar mass and halo mass. We show that for the standard implementations of supernova feedback and gas reincorporation used in semi-analytic models, this relationship is predicted to evolve weakly over the redshift range 0mass versus halo mass (SHM) relationship implicitly requires that, at fixed halo mass, the efficiency of stellar mass assembly must be almost constant with cosmic time. We show that in our model, this behaviour can be understood in simple terms as a result of a constant efficiency of gas reincorporation, and an efficiency of SNe feedback that is, on average, constant at fixed halo mass. We present a simple explanation of how feedback from active galactic nuclei (AGN) acts in our model to introduce a break in the SHM relation whose location is predicted to evolve only modestly. Finally, we show that...

  16. Halo Shape and its Relation to Environment

    Science.gov (United States)

    Gottlöber, S.; Turchaninov, V.

    Using high resolution DM simulations we study the shape of dark matter halos. Halos become more spherical with decreasing mass. This trend is even more pronounced for the inner part of the halo. Angular momentum and shape are correlated. The angular momenta of neighboring halos are correlated.

  17. Halo Shapes and their Relation to Environment

    CERN Document Server

    Gottlöber, S; Gottloeber, Stefan; Turchaninov, Victor

    2005-01-01

    Using high resolution DM simulations we study the shape of dark matter halos. Halos become more spherical with decreasing mass. This trend is even more pronounced for the inner part of the halo. Angular momentum and shape are correlated. The angular momenta of neighboring halos are correlated.

  18. The stellar mass-halo mass relation of isolated field dwarfs: a critical test of ΛCDM at the edge of galaxy formation

    Science.gov (United States)

    Read, J. I.; Iorio, G.; Agertz, O.; Fraternali, F.

    2017-01-01

    We fit the rotation curves of isolated dwarf galaxies to directly measure the stellar mass-halo mass relation (M★ - M200) over the mass range 5 {×} 10^5 ≲ M_{*} / M_⊙ ≲ 108. By accounting for cusp-core transformations due to stellar feedback, we find a monotonic relation with little scatter. Such monotonicity implies that abundance matching should yield a similar M★ - M200 if the cosmological model is correct. Using the `field galaxy' stellar mass function from the Sloan Digital Sky Survey (SDSS) and the halo mass function from the Λ Cold Dark Matter Bolshoi simulation, we find remarkable agreement between the two. This holds down to M200 ˜ 5 × 109 M⊙, and to M200 ˜ 5 × 108 M⊙ if we assume a power law extrapolation of the SDSS stellar mass function below M★ ˜ 107 M⊙. However, if instead of SDSS we use the stellar mass function of nearby galaxy groups, then the agreement is poor. This occurs because the group stellar mass function is shallower than that of the field below M★ ˜ 109 M⊙, recovering the familiar `missing satellites' and `too big to fail' problems. Our result demonstrates that both problems are confined to group environments and must, therefore, owe to `galaxy formation physics' rather than exotic cosmology. Finally, we repeat our analysis for a Λ Warm Dark Matter cosmology, finding that it fails at 68% confidence for a thermal relic mass of mWDM < 1.25 keV, and mWDM < 2 keV if we use the power law extrapolation of SDSS. We conclude by making a number of predictions for future surveys based on these results.

  19. The Mass-Discrepancy Acceleration Relation: a Natural Outcome of Galaxy Formation in CDM halos

    CERN Document Server

    Ludlow, Aaron D; Schaller, Matthieu; Theuns, Tom; Frenk, Carlos S; Bower, Richard; Schaye, Joop; Crain, Robert A; Navarro, Julio F; Fattahi, Azadeh; Oman, Kyle A

    2016-01-01

    We analyze the total and baryonic acceleration profiles of a set of well-resolved galaxies identified in the EAGLE suite of hydrodynamic simulations. Our runs start from the same initial conditions but adopt different subgrid models for stellar and AGN feedback, resulting in diverse populations of galaxies by the present day. Some of them reproduce observed galaxy scaling relations, while others do not. However, regardless of the feedback implementation, all of our galaxies follow closely a simple relationship between the total and baryonic acceleration profiles, consistent with recent observations of rotationally supported galaxies. The relation has small scatter: different feedback processes -- which produce different galaxy populations -- mainly shift galaxies along the relation, rather than perpendicular to it. Furthermore, galaxies exhibit a single characteristic acceleration, $g_{\\dagger}$, above which baryons dominate the mass budget, as observed. These observations have been hailed as evidence for mod...

  20. The Impact of Theoretical Uncertainties in the Halo Mass Function and Halo

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Hao-Yi; Zentner, Andrew R.; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC /Pittsburgh U. /KIPAC, Menlo Park /SLAC

    2010-06-04

    We study the impact of theoretical uncertainty in the dark matter halo mass function and halo bias on dark energy constraints from imminent galaxy cluster surveys. We find that for an optical cluster survey like the Dark Energy Survey, the accuracy required on the predicted halo mass function to make it an insignificant source of error on dark energy parameters is {approx}1%. The analogous requirement on the predicted halo bias is less stringent ({approx}5%), particularly if the observable-mass distribution can be well constrained by other means. These requirements depend upon survey area but are relatively insensitive to survey depth. The most stringent requirements are likely to come from a survey over a significant fraction of the sky that aims to observe clusters down to relatively low mass, M{sub th}{approx} 10{sup 13.7} h{sup -1} M{sub sun}; for such a survey, the mass function and halo bias must be predicted to accuracies of {approx}0.5% and {approx}1%, respectively. These accuracies represent a limit on the practical need to calibrate ever more accurate halo mass and bias functions. We find that improving predictions for the mass function in the low-redshift and low-mass regimes is the most effective way to improve dark energy constraints.

  1. Cosmology and cluster halo scaling relations

    NARCIS (Netherlands)

    Araya-Melo, Pablo A.; van de Weygaert, Rien; Jones, Bernard J. T.

    2009-01-01

    We explore the effects of dark matter and dark energy on the dynamical scaling properties of galaxy clusters. We investigate the cluster Faber-Jackson (FJ), Kormendy and Fundamental Plane (FP) relations between the mass, radius and velocity dispersion of cluster-sized haloes in cosmological N-body s

  2. Reionization Histories of Milky Way Mass Halos

    OpenAIRE

    Li, Tony Y.; Alvarez, Marcelo A.; Wechsler, Risa H.; Abel, Tom

    2013-01-01

    We investigate the connection between the epoch of reionization and the present day universe, by examining the extended mass reionization histories of dark matter halos identified at z=0. We combine an N-body dark matter simulation of a 600 Mpc volume with a three-dimensional, seminumerical reionization model. This provides reionization redshifts for each particle, which can then be connected with the properties of their halos at the present time. We find that the vast majority of present-day...

  3. GAS REGULATION OF GALAXIES: THE EVOLUTION OF THE COSMIC SPECIFIC STAR FORMATION RATE, THE METALLICITY-MASS-STAR-FORMATION RATE RELATION, AND THE STELLAR CONTENT OF HALOS

    Energy Technology Data Exchange (ETDEWEB)

    Lilly, Simon J.; Carollo, C. Marcella; Pipino, Antonio; Peng Yingjie [Institute for Astronomy, Department of Physics, ETH Zurich, CH-8093 Zurich (Switzerland); Renzini, Alvio [Department of Physics and Astronomy Galileo Galilei, Universita degli Studi di Padova, via Marzolo 8, I-35131 Padova (Italy)

    2013-08-01

    A very simple physical model of galaxies is one in which the formation of stars is instantaneously regulated by the mass of gas in a reservoir with mass loss scaling with the star-formation rate (SFR). This model links together three different aspects of the evolving galaxy population: (1) the cosmic time evolution of the specific star-formation rate (sSFR) relative to the growth of halos, (2) the gas-phase metallicities across the galaxy population and over cosmic time, and (3) the ratio of the stellar to dark matter mass of halos. The gas regulator is defined by the gas consumption timescale ({epsilon}{sup -1}) and the mass loading {lambda} of the wind outflow {lambda}{center_dot}SFR. The simplest regulator, in which {epsilon} and {lambda} are constant, sets the sSFR equal to exactly the specific accretion rate of the galaxy; more realistic situations lead to an sSFR that is perturbed from this precise relation. Because the gas consumption timescale is shorter than the timescale on which the system evolves, the metallicity Z is set primarily by the instantaneous operation of the regulator system rather than by the past history of the system. The metallicity of the gas reservoir depends on {epsilon}, {lambda}, and sSFR, and the regulator system therefore naturally produces a Z(m{sub star}, SFR) relation if {epsilon} and {lambda} depend on the stellar mass m{sub star}. Furthermore, this relation will be the same at all epochs unless the parameters {epsilon} and {lambda} themselves change with time. A so-called fundamental metallicity relation is naturally produced by these conditions. The overall mass-metallicity relation Z(m{sub star}) directly provides the fraction f{sub star}(m{sub star}) of incoming baryons that are being transformed into stars. The observed Z(m{sub star}) relation of Sloan Digital Sky Survey (SDSS) galaxies implies a strong dependence of stellar mass on halo mass that reconciles the different faint-end slopes of the stellar and halo mass

  4. Galaxy and Mass Assembly (GAMA): halo formation times and halo assembly bias on the cosmic web

    Science.gov (United States)

    Tojeiro, Rita; Eardley, Elizabeth; Peacock, John A.; Norberg, Peder; Alpaslan, Mehmet; Driver, Simon P.; Henriques, Bruno; Hopkins, Andrew M.; Kafle, Prajwal R.; Robotham, Aaron S. G.; Thomas, Peter; Tonini, Chiara; Wild, Vivienne

    2017-09-01

    We present evidence for halo assembly bias as a function of geometric environment (GE). By classifying Galaxy and Mass Assembly (GAMA) galaxy groups as residing in voids, sheets, filaments or knots using a tidal tensor method, we find that low-mass haloes that reside in knots are older than haloes of the same mass that reside in voids. This result provides direct support to theories that link strong halo tidal interactions with halo assembly times. The trend with GE is reversed at large halo mass, with haloes in knots being younger than haloes of the same mass in voids. We find a clear signal of halo downsizing - more massive haloes host galaxies that assembled their stars earlier. This overall trend holds independently of GE. We support our analysis with an in-depth exploration of the L-Galaxies semi-analytic model, used here to correlate several galaxy properties with three different definitions of halo formation time. We find a complex relationship between halo formation time and galaxy properties, with significant scatter. We confirm that stellar mass to halo mass ratio, specific star formation rate (SFR) and mass-weighed age are reasonable proxies of halo formation time, especially at low halo masses. Instantaneous SFR is a poor indicator at all halo masses. Using the same semi-analytic model, we create mock spectral observations using complex star formation and chemical enrichment histories, which approximately mimic GAMA's typical signal-to-noise ratio and wavelength range. We use these mocks to assert how well potential proxies of halo formation time may be recovered from GAMA-like spectroscopic data.

  5. The Dependence of Galaxy Type on Host Halo Mass

    CERN Document Server

    Weinmann, S M; Yang, X; Mo, H J; Weinmann, Simone M.; Bosch, Frank C. van den; Yang, Xiaohu

    2006-01-01

    We examine the relation between galaxy properties and environment in the SDSS DR2, quantifying environment in terms of the mass of the host halo, which is obtained with a new iterative group finder. We find that galaxy type fractions scale strongly and smoothly with halo mass, but, at fixed mass, not with luminosity. We compare these findings with the semi-analytical galaxy formation model of Croton et al. (2006). The discrepancies we find can be explained with an oversimplified implementation of strangulation, the neglect of tidal stripping, and shortcomings in the treatments of dust extinction and/or AGN feedback.

  6. Why are halo coronal mass ejections faster?

    Institute of Scientific and Technical Information of China (English)

    Qing-Min Zhang; Yang Guo; Peng-Fei Chen; Ming-De Ding; Cheng Fang

    2010-01-01

    Halo coronal mass ejections(CMEs)have been to be significantly faster than normal CMEs,which is a long-standing puzzle.In order to solve the puzzle,we first investigate the observed properties of 31 limb CMEs that clearly display loopshaped frontal loops.The observational results show a strong tendency that slower CMEs are weaker in white-light intensity.Then,we perform a Monte Carlo simulation of 20000 artificial limb CMEs that have an average velocity of~523 km s-1.The Thomson scattering of these events is calculated when they are assumed to be observed as limb and halo events,respectively.It is found that the white-light intensity of many slow CMEs becomes remarkably reduced when they turn from being viewed as a limb event to being viewed as a halo event.When the intensity is below the background solar wind fluctuation,it is assumed that they would be missed by coronagraphs.The average velocity of"detectable"halo CMEs is~922 km s-1,very close to the observed value.This also indicates that wider events are more likely to be recorded.The results soundly suggest that the higher average velocity of halo CMEs is due to that a majority of slow events and some of narrow fast events carrying less material are so faint that they are blended with the solar wind fluctuations,and therefore are not observed.

  7. The Relation Between Halo Shape, Velocity Dispersion and Formation Time

    CERN Document Server

    Ragone-Figueroa, C; Merchan, M; Gottlober, S; Yepes, G

    2010-01-01

    We use dark matter haloes identified in the MareNostrum Universe and galaxy groups identified in the Sloan Data Release 7 galaxy catalogue, to study the relation between halo shape and halo dynamics, parametrizing out the mass of the systems. A strong shape-dynamics, independent of mass, correlation is present in the simulation data, which we find it to be due to different halo formation times. Early formation time haloes are, at the present epoch, more spherical and have higher velocity dispersions than late forming-time haloes. The halo shape-dynamics correlation, albeit weaker, survives the projection in 2D (ie., among projected shape and 1-D velocity dispersion). A similar shape-dynamics correlation, independent of mass, is also found in the SDSS DR7 groups of galaxies and in order to investigate its cause we have tested and used, as a proxy of the group formation time, a concentration parameter. We have found, as in the case of the simulated haloes, that less concentrated groups, corresponding to late fo...

  8. Coupled Quintessence and the Halo Mass Function

    CERN Document Server

    Tarrant, Ewan R M; Copeland, Edmund J; Green, Anne M

    2011-01-01

    A sufficiently light scalar field slowly evolving in a potential can account for the dark energy that presently dominates the universe. This quintessence field is expected to couple directly to matter components, unless some symmetry of a more fundamental theory protects or suppresses it. Such a coupling would leave distinctive signatures in the background expansion history of the universe and on cosmic structure formation, particularly at galaxy cluster scales. Using semi--analytic expressions for the CDM halo mass function, we make predictions for halo abundance in models where the quintessence scalar field is coupled to cold dark matter, for a variety of quintessence potentials. We evaluate the linearly extrapolated density contrast at the redshift of collapse using the spherical collapse model and we compare this result to the corresponding prediction obtained from the non--linear perturbation equations in the Newtonian limit. For all the models considered in this work, if there is a continuous flow of en...

  9. Dark matter scaling relations in intermediate z haloes

    CERN Document Server

    Cardone, V F

    2010-01-01

    We investigate scaling relations between the dark matter (DM) halo model parameters for a sample of intermediate redshift early - type galaxies (ETGs) resorting to a combined analysis of Einstein radii and aperture velocity dispersions. Modeling the dark halo with a Navarro - Frenk - White profile and assuming a Salpeter initial mass function (IMF) to estimate stellar masses, we find that the column density ${\\cal{S}}$ and the Newtonian acceleration within the halo characteristic radius $r_s$ and effective radius $R_{eff}$ are not universal quantities, but correlate with the luminosity $L_V$, the stellar mass $M_{\\star}$ and the halo mass $M_{200}$, contrary to recent claims in the literature. We finally discuss a tight correlation among the DM mass $M_{DM}(R_{eff})$ within the effective radius $R_{eff}$, the stellar mass $M_{\\star}(R_{eff})$ and $R_{eff}$ itself. The slopes of the scaling relations discussed here strongly depend, however, on the DM halo model and the IMF adopted so that these ingredients hav...

  10. All about baryons: revisiting SIDM predictions at small halo masses

    CERN Document Server

    Fry, A Bastidas; Pontzen, A; Quinn, T; Tremmel, M; Anderson, L; Menon, H; Brooks, A M; Wadsley, J

    2015-01-01

    We use cosmological hydrodynamic simulations to consistently compare the assembly of dwarf galaxies in both $\\Lambda$ dominated, Cold (CDM) and Self--Interacting (SIDM) dark matter models. The SIDM model adopts a constant cross section of 2 $cm^{2}/g$, a relatively large value to maximize its effects. These are the first SIDM simulations that are combined with a description of stellar feedback that naturally drives potential fluctuations able to create dark matter cores. Remarkably, SIDM fails to significantly lower the central dark matter density at halo peak velocities V$_{max}$ $<$ 30 Km/s. This is due to the fact that the central regions of very low--mass field halos have relatively low central velocity dispersion and densities, leading to time scales for SIDM collisions greater than a Hubble time. CDM halos with V$_{max}$ $<$ 30 km/s have inefficient star formation, and hence weak supernova feedback. Thus, both CDM and SIDM halos at these low masses have cuspy dark matter density profiles. At large...

  11. The chosen few: the low mass halos that host faint galaxies

    CERN Document Server

    Sawala, Till; Fattahi, Azadeh; Navarro, Julio F; Theuns, Tom; Bower, Richard G; Crain, Robert A; Furlong, Michelle; Jenkins, Adrian; Schaller, Matthieu; Schaye, Joop

    2014-01-01

    Since reionization prevents star formation in most halos below 3 x 10^9 solar masses, dwarf galaxies only populate a fraction of existing dark matter halos. We use hydrodynamic cosmological simulations of the Local Group to study the discriminating factors for galaxy formation in the early Universe and connect them to the present-day properties of galaxies and halos. A combination of selection effects related to reionization, and the subsequent evolution of halos in different environments, introduces strong biases between the population of halos that host dwarf galaxies, and the total halo population. Halos that host galaxies formed earlier and are more concentrated. In addition, halos more affected by tidal stripping are more likely to host a galaxy for a given mass or maximum circular velocity, vmax, today. Consequently, satellite halos are populated more frequently than field halos, and satellite halos of 10^8 - 10^9 solar masses or vmax of 12 - 20 km/s, similar to the Local Group dwarf spheroidals, have e...

  12. Constraining the halo mass function with observations

    CERN Document Server

    Castro, Tiago; Quartin, Miguel

    2016-01-01

    The abundances of matter halos in the universe are described by the so-called halo mass function (HMF). It enters most cosmological analyses and parametrizes how the linear growth of primordial perturbations is connected to these abundances. Interestingly, this connection can be made approximately cosmology independent. This made it possible to map in detail its near-universal behavior through large-scale simulations. However, such simulations may suffer from systematic effects, especially if baryonic physics is included. In this paper we ask how well observations can constrain directly the HMF. The observables we consider are galaxy cluster number counts, galaxy cluster power spectrum and lensing of type Ia supernovae. Our results show that DES is capable of putting the first meaningful constraints, while both Euclid and J-PAS can give constraints on the HMF parameters which are comparable to the ones from state-of-the-art simulations. We also find that an independent measurement of cluster masses is even mo...

  13. Constraining the halo mass function with observations

    Science.gov (United States)

    Castro, Tiago; Marra, Valerio; Quartin, Miguel

    2016-12-01

    The abundances of dark matter haloes in the universe are described by the halo mass function (HMF). It enters most cosmological analyses and parametrizes how the linear growth of primordial perturbations is connected to these abundances. Interestingly, this connection can be made approximately cosmology independent. This made it possible to map in detail its near-universal behaviour through large-scale simulations. However, such simulations may suffer from systematic effects, especially if baryonic physics is included. In this paper, we ask how well observations can constrain directly the HMF. The observables we consider are galaxy cluster number counts, galaxy cluster power spectrum and lensing of Type Ia supernovae. Our results show that Dark Energy Survey is capable of putting the first meaningful constraints on the HMF, while both Euclid and J-PAS (Javalambre-Physics of the Accelerated Universe Astrophysical Survey) can give stronger constraints, comparable to the ones from state-of-the-art simulations. We also find that an independent measurement of cluster masses is even more important for measuring the HMF than for constraining the cosmological parameters, and can vastly improve the determination of the HMF. Measuring the HMF could thus be used to cross-check simulations and their implementation of baryon physics. It could even, if deviations cannot be accounted for, hint at new physics.

  14. Connecting stellar mass and star-formation rate to dark matter halo mass out to z ˜ 2

    Science.gov (United States)

    Wang, L.; Farrah, D.; Oliver, S. J.; Amblard, A.; Béthermin, M.; Bock, J.; Conley, A.; Cooray, A.; Halpern, M.; Heinis, S.; Ibar, E.; Ilbert, O.; Ivison, R. J.; Marsden, G.; Roseboom, I. G.; Rowan-Robinson, M.; Schulz, B.; Smith, A. J.; Viero, M.; Zemcov, M.

    2013-05-01

    We have constructed an extended halo model (EHM) which relates the total stellar mass and star-formation rate (SFR) to halo mass (Mh). An empirical relation between the distribution functions of total stellar mass of galaxies and host halo mass, tuned to match the spatial density of galaxies over 0 EHM with the halo accretion histories from numerical simulations, we trace the stellar mass growth and star-formation history in haloes spanning a range of masses. We find that: (1) the intensity of the star-forming activity in haloes in the probed mass range has steadily decreased from z ˜ 2 to 0; (2) at a given epoch, haloes in the mass range between a few times 1011 M⊙ and a few times 1012 M⊙ are the most efficient at hosting star formation; (3) the peak of SFR density shifts to lower mass haloes over time; and (4) galaxies that are forming stars most actively at z ˜ 2 evolve into quiescent galaxies in today's group environments, strongly supporting previous claims that the most powerful starbursts at z ˜ 2 are progenitors of today's elliptical galaxies.

  15. A Study of Halo Coronal Mass Ejections and Related Flare and Radio Burst Observations in Solar Cycle 23

    CERN Document Server

    Georgiou, M; Pothitakis, G; Hillaris, A; Preka-Papadema, P; Moussas, X; 10.1063/1.2347981

    2010-01-01

    We present a statistical study of dynamical and kinetic characteristics of CMEs which show temporal and spatial association with flares and type II radio bursts or complex radio events of type II bursts and type IV continua. This study is based on a set of earth-directed full halo CMEs occurring during the present solar cycle, with data from the Large Angle Spectrometric Coronagraphs (LASCO) and Extreme-Ultraviolet Imaging Telescope (EIT) aboard the Solar and Heliospheric Observatory (SOHO) mission and the Magnetic Fields Investigation (MFI) and 3-D Plasma and Energetic Particle Analyzer Investigation experiment on board the WIND spacecraft.

  16. The Mass Function of Unprocessed Dark Matter Halos and Merger Tree Branching Rates

    CERN Document Server

    Benson, Andrew J

    2016-01-01

    A common approach in semi-analytic modeling of galaxy formation is to construct Monte Carlo realizations of merger histories of dark matter halos whose masses are sampled from a halo mass function. Both the mass function itself, and the merger rates used to construct merging histories are calibrated to N-body simulations. Typically, "backsplash" halos (those which were once subhalos within a larger halo, but which have since moved outside of the halo) are counted in both the halo mass function, and in the merger rates (or, equivalently, progenitor mass functions). This leads to a double-counting of mass in Monte Carlo merger histories which will bias results relative to N-body results. We measure halo mass functions and merger rates with this double-counting removed in a large, cosmological N-body simulation with cosmological parameters consistent with current constraints. Furthermore, we account for the inherently noisy nature of N-body halo mass estimates when fitting functions to N-body data, and show that...

  17. STELLAR MASS-GAP AS A PROBE OF HALO ASSEMBLY HISTORY AND CONCENTRATION: YOUTH HIDDEN AMONG OLD FOSSILS

    Energy Technology Data Exchange (ETDEWEB)

    Deason, A. J.; Conroy, C. [Department of Astronomy and Astrophysics, University of California Santa Cruz, Santa Cruz, CA 95064 (United States); Wetzel, A. R. [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); Tinker, J. L., E-mail: alis@ucolick.org [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY 10013 (United States)

    2013-11-10

    We investigate the use of the halo mass-gap statistic—defined as the logarithmic difference in mass between the host halo and its most massive satellite subhalo—as a probe of halo age and concentration. A cosmological N-body simulation is used to study N ∼ 25, 000 group/cluster-sized halos in the mass range 10{sup 12.5} < M{sub halo}/M{sub ☉} < 10{sup 14.5}. In agreement with previous work, we find that halo mass-gap is related to halo formation time and concentration. On average, older and more highly concentrated halos have larger halo mass-gaps, and this trend is stronger than the mass-concentration relation over a similar dynamic range. However, there is a large amount of scatter owing to the transitory nature of the satellite subhalo population, which limits the use of the halo mass-gap statistic on an object-by-object basis. For example, we find that 20% of very large halo mass-gap systems (akin to {sup f}ossil groups{sup )} are young and have likely experienced a recent merger between a massive satellite subhalo and the central subhalo. We relate halo mass-gap to the observable stellar mass-gap via abundance matching. Using a galaxy group catalog constructed from the Sloan Digital Sky Survey Data Release 7, we find that the star formation and structural properties of galaxies at fixed mass show no trend with stellar mass-gap. This is despite a variation in halo age of ≈2.5 Gyr over ≈1.2 dex in stellar mass-gap. Thus, we find no evidence to suggest that the halo formation history significantly affects galaxy properties.

  18. The mass profile and accretion history of cold dark matter haloes

    Science.gov (United States)

    Ludlow, Aaron D.; Navarro, Julio F.; Boylan-Kolchin, Michael; Bett, Philip E.; Angulo, Raúl E.; Li, Ming; White, Simon D. M.; Frenk, Carlos; Springel, Volker

    2013-06-01

    We use the Millennium Simulation series to investigate the relation between the accretion history and mass profile of cold dark matter (CDM) haloes. We find that the mean inner density within the scale radius, r-2 (where the halo density profile has isothermal slope), is directly proportional to the critical density of the Universe at the time when the virial mass of the main progenitor equals the mass enclosed within r-2. Scaled to these characteristic values of mass and density, the average mass accretion history, expressed in terms of the critical density of the Universe, M(ρcrit(z)), resembles that of the enclosed density profile, M(), at z = 0. Both follow closely the Navarro, Frenk & White (NFW) profile, which suggests that the similarity of halo mass profiles originates from the mass-independence of halo accretion histories. Support for this interpretation is provided by outlier haloes whose accretion histories deviate from the NFW shape; their mass profiles show correlated deviations from NFW and are better approximated by Einasto profiles. Fitting both M() and M(ρcrit) with either NFW or Einasto profiles yield concentration and shape parameters that are correlated, confirming and extending earlier work that has linked the concentration of a halo with its accretion history. These correlations also confirm that halo structure is insensitive to initial conditions: only haloes whose accretion histories differ greatly from the NFW shape show notable deviations from NFW in their mass profiles. As a result, the NFW profile provides acceptable fits to hot dark matter haloes, which do not form hierarchically, and for fluctuation power spectra other than CDM. Our findings, however, predict a subtle but systematic dependence of mass profile shape on accretion history which, if confirmed, would provide strong support for the link between accretion history and halo structure we propose here.

  19. The f(Script R) halo mass function in the cosmic web

    Science.gov (United States)

    von Braun-Bates, F.; Winther, H. A.; Alonso, D.; Devriendt, J.

    2017-03-01

    An important indicator of modified gravity is the effect of the local environment on halo properties. This paper examines the influence of the local tidal structure on the halo mass function, the halo orientation, spin and the concentration-mass relation. We use the excursion set formalism to produce a halo mass function conditional on large-scale structure. Our simple model agrees well with simulations on large scales at which the density field is linear or weakly non-linear. Beyond this, our principal result is that f(Script R) does affect halo abundances, the halo spin parameter and the concentration-mass relationship in an environment-independent way, whereas we find no appreciable deviation from \\text{ΛCDM} for the mass function with fixed environment density, nor the alignment of the orientation and spin vectors of the halo to the eigenvectors of the local cosmic web. There is a general trend for greater deviation from \\text{ΛCDM} in underdense environments and for high-mass haloes, as expected from chameleon screening.

  20. Estimating the dark matter halo mass of our Milky Way using dynamical tracers

    Science.gov (United States)

    Wang, Wenting; Han, Jiaxin; Cooper, Andrew P.; Cole, Shaun; Frenk, Carlos; Lowing, Ben

    2015-10-01

    The mass of the dark matter halo of the Milky Way can be estimated by fitting analytical models to the phase-space distribution of dynamical tracers. We test this approach using realistic mock stellar haloes constructed from the Aquarius N-body simulations of dark matter haloes in the Λ cold dark matter cosmology. We extend the standard treatment to include a Navarro-Frenk-White potential and use a maximum likelihood method to recover the parameters describing the simulated haloes from the positions and velocities of their mock halo stars. We find that the estimate of halo mass is highly correlated with the estimate of halo concentration. The best-fitting halo masses within the virial radius, R200, are biased, ranging from a 40 per cent underestimate to a 5 per cent overestimate in the best case (when the tangential velocities of the tracers are included). There are several sources of bias. Deviations from dynamical equilibrium can potentially cause significant bias; deviations from spherical symmetry are relatively less important. Fits to stars at different galactocentric radii can give different mass estimates. By contrast, the model gives good constraints on the mass within the half-mass radius of tracers even when restricted to tracers within 60 kpc. The recovered velocity anisotropies of tracers, β, are biased systematically, but this does not affect other parameters if tangential velocity data are used as constraints.

  1. Halo Mass of Three-Dimension Milky Way

    Institute of Scientific and Technical Information of China (English)

    PENG Fang; PENG Qiu He

    2000-01-01

    We emphasize the effects of several factors on halo mass for our Galaxy, such as the disk thickness, the local surface density, and the shape of the rotation curve. By fitting the observed rotation curve of our Galaxy with the five-component model, we deduce a halo with a mass of 6.62× 1011 M within 50 kpc and a local density of 0.009M pc-3. It is found that the realistic Galaxy needs only about half of the halo mass that the Galaxy with n infinitesmally thin disk requires.

  2. Galaxy Mergers and Dark Matter Halo Mergers in LCDM: Mass, Redshift, and Mass-Ratio Dependence

    CERN Document Server

    Stewart, Kyle R; Barton, Elizabeth J; Wechsler, Risa H

    2008-01-01

    We employ a high-resolution LCDM N-body simulation to present merger rate predictions for dark matter halos and investigate how common merger-related observables for galaxies--such as close pair counts, starburst counts, and the morphologically disturbed fraction--likely scale with luminosity, stellar mass, merger mass ratio, and redshift from z=0 to z=4. We provide a simple 'universal' fitting formula that describes our derived merger rates for dark matter halos a function of dark halo mass, merger mass ratio, and redshift, and go on to predict galaxy merger rates using number density-matching to associate halos with galaxies. For example, we find that the instantaneous merger rate of m/M>0.3 mass ratio events into typical L > f L* galaxies follows the simple relation dN/dt=0.03(1+f)(1+z)^2.1 Gyr^-1. Despite the rapid increase in merger rate with redshift, only a small fraction of >0.4 L* high-redshift galaxies (~3% at z=2) should have experienced a major merger (m/M >0.3) in the very recent past (t0.3) in t...

  3. A Second-order bias model for the Logarithmic Halo Mass Density

    CERN Document Server

    Jee, Inh; Kim, Juhan; Choi, Yun-Young; Kim, Sungsoo S

    2012-01-01

    We present an analytic model for the local bias of dark matter halos in a LCDM universe. The model uses the halo mass density instead of the halo number density and is searched for various halo mass cuts, smoothing lengths, and redshift epoches. We find that, when the logarithmic density is used, the second-order polynomial can fit the numerical relation between the halo mass distribution and the underlying matter distribution extremely well. In this model the logarithm of the dark matter density is expanded in terms of log halo mass density to the second order. The model remains excellent for all halo mass cuts (from M_{cut}=3\\times10^{11}$ to $3\\times10^{12}h^{-1}M_{\\odot}$), smoothing scales (from $R=5h^{-1}$Mpc to $50h^{-1}$Mpc), and redshift ranges (from z=0 to 1.0) considered in this study. The stochastic term in the relation is found not entirely random, but a part of the term can be determined by the magnitude of the shear tensor.

  4. Estimating the dark matter halo mass of our Milky Way using dynamical tracers

    CERN Document Server

    Wang, Wenting; Cooper, Andrew; Cole, Shaun; Frenk, Carlos; Cai, Yanchuan; Lowing, Ben

    2015-01-01

    The mass of the dark matter halo of the Milky Way can be estimated by fitting analytical models to the phase space distribution of dynamical tracers. We test this approach using realistic mock stellar halos constructed from the Aquarius N-body simulations of dark matter halos in the $\\Lambda$CDM cosmology. We extend the standard treatment to include a Navarro-Frenk-White (NFW) potential and use a maximum likelihood method to recover the parameters describing the simulated halos from the positions and velocities of their mock halo stars. We find that the estimate of halo mass is degenerate with the estimate of halo concentration. The best-fit halo masses within the virial radius, $R_{200}$, are biased, ranging from a 40% underestimate to a 5% overestimate in the best case (when the tangential velocities of the tracers are included). There are several sources of bias. Deviations from dynamical equilibrium can potentially cause significant bias; deviations from spherical symmetry are relatively less important. F...

  5. The effects of baryons on the halo mass function

    CERN Document Server

    Cui, Weiguang; Dolag, Klaus; Murante, Giuseppe; Tornatore, Luca

    2011-01-01

    We present an analysis of the effects of baryon physics on the halo mass function. The analysis is based on simulations of a cosmological volume. Besides a Dark Matter (DM) only simulation, we also carry out two other hydrodynamical simulations. We identified halos using a spherical overdensity algorithm and their masses are computed at three different overdensities (with respect to the critical one), $\\Delta_c=200$, 500 and 1500. We find the fractional difference between halo masses in the hydrodynamical and in the DM simulations to be almost constant, at least for halos more massive than $\\log (M_{\\Delta_c} / \\hMsun)\\geq 13.5$. In this range, mass increase in the hydrodynamical simulations is of about 4-5 per cent at $\\Delta_c=500$ and $\\sim 1$ - 2 per cent at $\\Delta_c=200$. Quite interestingly, these differences are nearly the same for both radiative and non-radiative simulations. Such variations of halo masses induce corresponding variations of the halo mass function (HMF). At $z=0$, the HMFs for GH and ...

  6. Constraints on the evolution of the relationship between HI mass and halo mass in the last 12 Gyr

    CERN Document Server

    Padmanabhan, Hamsa

    2016-01-01

    The neutral hydrogen (HI) content of dark matter haloes forms an intermediate state in the baryon cycle that connects the hot shock-heated gas and cold star-forming gas in haloes. Measurement of the relationship between HI mass and halo mass therefore puts important constraints on galaxy formation models. We combine radio observations of HI in emission at low redshift ($z\\sim 0$) with optical/UV observations of HI in absorption at high redshift ($1mass halo-mass (HIHM) relation from redshift $z=4$ to $z=0$. We model the evolution of the HIHM relation in a manner similar to that of the stellar-halo mass (SHM) relation. Combining this parameterisation with a redshift- and mass-dependent modified Navarro-Frenk-White (NFW) profile for the HI density within a halo, we draw constraints on the evolution of the HIHM relation from the observed HI column density, incidence rate, and clustering bias at high redshift. We find that the peak HI mass fraction mod...

  7. Large Geomagnetic Storms Associated with Limb Halo Coronal Mass Ejections

    CERN Document Server

    Gopalswamy, Nat; Xie, Hong; Akiyama, Sachiko; Makela, Pertti

    2009-01-01

    Solar cycle 23 witnessed the observation of hundreds of halo coronal mass ejections (CMEs), thanks to the high dynamic range and extended field of view of the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO) mission. More than two thirds of halo CMEs originating on the front side of the Sun have been found to be geoeffective (Dst = 45deg) have a 20% shorter delay time on the average. It was suggested that the geomagnetic storms due to limb halos must be due to the sheath portion of the interplanetary CMEs (ICMEs) so that the shorter delay time can be accounted for. We confirm this suggestion by examining the sheath and ejecta portions of ICMEs from Wind and ACE data that correspond to the limb halos. Detailed examination showed that three pairs of limb halos were interacting events. Geomagnetic storms following five limb halos were actually produced by other disk halos. The storms followed by four isolated limb halos and the ones associated with interact...

  8. Observational probes of the connection between Star Formation Efficiency and Dark Matter halo mass of galaxies

    Science.gov (United States)

    Kalinova, Veselina; Colombo, Dario; Rosolowsky, Erik

    2015-08-01

    Modern simulations predict that the stellar mass and the star formation efficiency of a galaxy are tightly linked to the dark matter (DM) halo mass of that galaxy. This prediction relies on a specific model of galaxy evolution and so testing this prediction directly tests our best models of galaxy formation and evolution. Recent DM numerical studies propose relationships between star formation efficiency and the DM halo mass with two domains based on SF feedback (low-mass) vs. AGN feedback (high-mass), see Moster et al. (2013). The observational probe of such parameters in the relationship imply globally important physics that are fundamental as, e.g., the star formation law (e.g., Kennicutt et al., 1998), the universal depletion time (Leroy et al. 2008), and the origin of the cold gas phase with respect to the stellar disc (Davis et al.2011). Thus, we can directly measure whether this parameterization is correct by estimating the stellar mass, star formation efficiency and dynamical (DM) mass for a set of galaxies at strategically selected points to test if they fall on the predicted relationship.We use CO data from the Extragalactic Database for Galaxy Evolution survey (EDGE) in conjunction with archival 21-cm data and spectroscopic data from Calar Alto Legacy Integral Field spectroscopy Area survey (CALIFA) to measure the stellar vs. halo mass and star-formation-efficiency vs. halo mass relations of the galaxies. We also analyze archival 21-cm spectra to estimate rotation speeds, atomic gas masses and halo masses for a set of EDGE galaxies. Data from CALIFA are used for high quality star formation efficiency and stellar mass measurements. By linking these three parameters - stellar mass, star formation efficiency (SFE) and DM halo mass - we can test the simulation models of how the gas is cooling in the potential wells of the dark matter halos and then forms stars.

  9. Alignments of Dark Matter Halos with Large-scale Tidal Fields: Mass and Redshift Dependence

    Science.gov (United States)

    Chen, Sijie; Wang, Huiyuan; Mo, H. J.; Shi, Jingjing

    2016-07-01

    Large-scale tidal fields estimated directly from the distribution of dark matter halos are used to investigate how halo shapes and spin vectors are aligned with the cosmic web. The major, intermediate, and minor axes of halos are aligned with the corresponding tidal axes, and halo spin axes tend to be parallel with the intermediate axes and perpendicular to the major axes of the tidal field. The strengths of these alignments generally increase with halo mass and redshift, but the dependence is only on the peak height, ν \\equiv {δ }{{c}}/σ ({M}{{h}},z). The scaling relations of the alignment strengths with the value of ν indicate that the alignment strengths remain roughly constant when the structures within which the halos reside are still in a quasi-linear regime, but decreases as nonlinear evolution becomes more important. We also calculate the alignments in projection so that our results can be compared directly with observations. Finally, we investigate the alignments of tidal tensors on large scales, and use the results to understand alignments of halo pairs separated at various distances. Our results suggest that the coherent structure of the tidal field is the underlying reason for the alignments of halos and galaxies seen in numerical simulations and in observations.

  10. Halo-Independent Direct Detection Analyses Without Mass Assumptions

    CERN Document Server

    Anderson, Adam J; Kahn, Yonatan; McCullough, Matthew

    2015-01-01

    Results from direct detection experiments are typically interpreted by employing an assumption about the dark matter velocity distribution, with results presented in the $m_\\chi-\\sigma_n$ plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the $v_{min}-\\tilde{g}$ plane, but these in turn require an assumption on the dark matter mass. Here we present an extension of these halo-independent methods for dark matter direct detection which does not require a fiducial choice of the dark matter mass. With a change of variables from $v_{min}$ to nuclear recoil momentum ($p_R$), the full halo-independent content of an experimental result for any dark matter mass can be condensed into a single plot as a function of a new halo integral variable, which we call $\\tilde{h}(p_R)$. The entire family of conventional halo-independent $\\tilde{g}(v_{min})$ plots for all DM masses are directly found from the single $\\tilde{h}(p_R)$ plot through a simple re...

  11. Mapping stellar content to dark matter haloes - II. Halo mass is the main driver of galaxy quenching

    Science.gov (United States)

    Zu, Ying; Mandelbaum, Rachel

    2016-04-01

    We develop a simple yet comprehensive method to distinguish the underlying drivers of galaxy quenching, using the clustering and galaxy-galaxy lensing of red and blue galaxies in Sloan Digital Sky Survey. Building on the iHOD framework developed by Zu & Mandelbaum, we consider two quenching scenarios: (1) a `halo' quenching model in which halo mass is the sole driver for turning off star formation in both centrals and satellites; and (2) a `hybrid' quenching model in which the quenched fraction of galaxies depends on their stellar mass, while the satellite quenching has an extra dependence on halo mass. The two best-fitting models describe the red galaxy clustering and lensing equally well, but halo quenching provides significantly better fits to the blue galaxies above 1011 h-2 M⊙. The halo quenching model also correctly predicts the average halo mass of the red and blue centrals, showing excellent agreement with the direct weak lensing measurements of locally brightest galaxies. Models in which quenching is not tied to halo mass, including an age-matching model in which galaxy colour depends on halo age at fixed M*, fail to reproduce the observed halo mass for massive blue centrals. We find similar critical halo masses responsible for the quenching of centrals and satellites (˜1.5 × 1012 h-1 M⊙), hinting at a uniform quenching mechanism for both, e.g. the virial shock heating of infalling gas. The success of the iHOD halo quenching model provides strong evidence that the physical mechanism that quenches star formation in galaxies is tied principally to the masses of their dark matter haloes rather than the properties of their stellar components.

  12. Not enough stellar Mass Machos in the Galactic Halo

    CERN Document Server

    Lasserre, T; Albert, J N; Andersen, J; Ansari, R; Aubourg, E; Bareyre, P; Bauer, F; Beaulieu, J P; Blanc, G; Bouquet, A; Char, S; Charlot, X; Couchot, F; Coutures, C; Derue, F; Ferlet, R; Glicenstein, J F; Goldman, B; Gould, A; Graff, D; Gros, M H; Haïssinski, J; Hamilton, J C; Hardin, D; De Kat, J; Kim, A; Lesquoy, E; Loup, C; Magneville, C; Mansoux, B; Marquette, J B; Maurice, E; Milshtein, A I; Moniez, M; Palanque-Delabrouille, Nathalie; Perdereau, O; Prévôt, L; Regnault, N; Rich, J; Spiro, Michel; Vidal-Madjar, A; Vigroux, L; Zylberajch, S

    2000-01-01

    We combine new results from the search for microlensing towards the LargeMagellanic Cloud (LMC) by EROS2 (Experience de Recherche d'Objets Sombres) withlimits previously reported by EROS1 and EROS2 towards both Magellanic Clouds.The derived upper limit on the abundance of stellar mass MACHOs rules out suchobjects as an important component of the Galactic halo if their mass is smallerthan 1 solar mass.

  13. The overdensity and masses of the friends-of-friends halos and universality of the halo mass function

    CERN Document Server

    More, Surhud; Dalal, Neal; Gottlöber, Stefan

    2011-01-01

    The friends-of-friends algorithm (hereafter, FOF) is a percolation algorithm which is routinely used to identify dark matter halos from N-body simulations. We use results from percolation theory to show that the boundary of FOF halos does not correspond to a single density threshold but to a range of densities close to a critical value that depends upon the linking length parameter, b. We show that for the commonly used choice of b = 0.2, this critical density is equal to 81.62 times the mean matter density. Consequently, halos identified by the FOF algorithm enclose an average overdensity which depends on their density profile (concentration) and therefore changes with halo mass contrary to the popular belief that the average overdensity is ~180. We derive an analytical expression for the overdensity as a function of the linking length parameter b and the concentration of the halo. Results of tests carried out using simulated and actual FOF halos identified in cosmological simulations show excellent agreemen...

  14. On the relation between Solar Filament disappearances and Halo CME

    Science.gov (United States)

    Shaltout, Mosalam; Hussein, Magda

    On the relation between solar filament disappearances and Halo CME M.M. Hussein(1) Abstract Filament eruptions, flares, and coronal mass ejections (CMEs) are the most important solar events as far as space weather effects are concerned, linking solar eruptions, major interplanetary disturbances, and geomagnetic storms. A halo CME, which is usually associated with activity near the solar disk center, has great influence on space weather because an Earthward halo CME is indicative of coronal mass and magnetic fields moving out toward the Earth, therefore likely to cause geoeffective disturbances. The majority of previous statistical studies regarding the connection between filament eruptions and CMEs because they could be detected, observed, and measured against the dark sky background. In this paper we present a comprehensive study of filament disappearances from 1996 to 2008, and Hallo CME data for the same period that presents solar cycle 23, to predict Hallo CME for the next ten years by using different statistical tools. 1. Assistant researcher Solar and Space researches Department in the National Research Institute of Astronomy and Geophysics (NRIAG)

  15. Stellar mass-gap as a probe of halo assembly history and concentration: youth hidden among old fossils

    CERN Document Server

    Deason, Alis J; Wetzel, Andrew R; Tinker, Jeremy L

    2013-01-01

    We investigate the use of the mass-gap statistic --- defined as the logarithmic difference in mass between the host halo and its most massive satellite subhalo --- as a probe of halo age and concentration. A cosmological N-body simulation is used to study N ~ 25,000 group/cluster sized halos in the mass range 10^12.5 < M_halo/M_sun < 10^14.5. In agreement with previous work, we find that mass-gap is related to halo formation time and concentration. On average, older and more highly concentrated halos have larger mass-gaps, and this trend is stronger than the mass-concentration relation over a similar dynamic range. However, there is a large amount of scatter owing to the transitory nature of the satellite population, which limits the use of the mass-gap statistic on an object-by-object basis. For example, we find that 20% of very large mass-gap systems (akin to "fossil groups") are young, and have likely experienced a recent merger between a massive satellite and the central galaxy. We relate halo mass-...

  16. A Filament-Associated Halo Coronal Mass Ejection

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    There are only a few observations published so far that show the initiation of a coronal mass ejection (CME) and illustrate the magnetic changes in the surface origin of a CME. Any attempt to connect a CME with its local solar activities is meaningful. In this paper we present a clear instance of a halo CME initiation. A careful analysis of magnetograms shows that the only obvious magnetic changes in the surface region of the CME is a magnetic flux cancellation underneath a quiescent filament. The early disturbance was seen as the slow upward motion in segments of the quiescent filament. Four hours later, the filament was accelerated to about 50 km s-1 and erupted. While a small part of the material in the filament was ejected into the upper corona, most of the mass was transported to a nearby region. About forty minutes later, the transported mass was also ejected partially to the upper corona. The eruption of the filament triggered a two-ribbon flare, with post-flare loops connecting the flare ribbons. A halo CME, which is inferred to be associated with the eruptive filament, was observed from LASCO/C2 and C3. The halo CME contained two CME events, each event corresponded to a partial mass ejection of the filament. We suggest that the magnetic reconnection at the lower atmosphere is responsible for the filament eruption and the halo CME.

  17. CFHTLenS: The relation between galaxy dark matter haloes and baryons from weak gravitational lensing

    CERN Document Server

    Velander, Malin; Hoekstra, Henk; Coupon, Jean; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Kitching, Thomas D; Mellier, Yannick; Miller, Lance; Van Waerbeke, Ludovic; Bonnett, Christopher; Fu, Liping; Giodini, Stefania; Hudson, Michael J; Kuijken, Konrad; Rowe, Barnaby; Schrabback, Tim; Semboloni, Elisabetta

    2013-01-01

    We present a study of the relation between dark matter halo mass and the baryonic content of host galaxies, quantified through luminosity and stellar mass. Our investigation uses 154 deg2 of Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) lensing and photometric data, obtained from the CFHT Legacy Survey. We employ a galaxy-galaxy lensing halo model which allows us to constrain the halo mass and the satellite fraction, and our analysis is limited to lenses at redshifts between 0.2 and 0.4. We express the relationship between halo mass and baryonic observable as a power law. For the luminosity-halo mass relation we find a slope of 1.56+0.04-0.06 and a normalisation of 1.26+0.07-0.06x10^13 h70^-1 Msun for red galaxies, while for blue galaxies the best-fit slope is 0.73+0.09-0.08 and the normalisation is 0.16+/-0.03x10^13 h70^-1 Msun. Similarly, we find a best-fit slope of 1.49+0.06-0.04 and a normalisation of 1.30+0.05-0.09x10^13 h70^-1 Msun for the stellar mass-halo mass relation of red galaxies, whil...

  18. The baryonic mass assembly of low-mass halos in a Lambda-CDM Universe

    CERN Document Server

    De Rossi, Maria E; Tissera, Patricia B; Gonzalez-Samaniego, Alejandro; Pedrosa, Susana

    2014-01-01

    We analyse the dark, gas, and stellar mass assembly histories of low-mass halos (Mvir ~ 10^10.3 - 10^12.3 M_sun) identified at redshift z = 0 in cosmological numerical simulations. Our results indicate that for halos in a given present-day mass bin, the gas-to-baryon fraction inside the virial radius does not evolve significantly with time, ranging from ~0.8 for smaller halos to ~0.5 for the largest ones. Most of the baryons are located actually not in the galaxies but in the intrahalo gas; for the more massive halos, the intrahalo gas-to-galaxy mass ratio is approximately the same at all redshifts, z, but for the least massive halos, it strongly increases with z. The intrahalo gas in the former halos gets hotter with time, being dominant at z = 0, while in the latter halos, it is mostly cold at all epochs. The multiphase ISM and thermal feedback models in our simulations work in the direction of delaying the stellar mass growth of low-mass galaxies.

  19. Relation between halo spin and cosmic-web filaments at z ≃ 3

    Science.gov (United States)

    González, Roberto E.; Prieto, Joaquin; Padilla, Nelson; Jimenez, Raul

    2017-02-01

    We investigate the spin evolution of dark matter haloes and their dependence on the number of connected filaments from the cosmic web at high redshift (spin-filament relation hereafter). To this purpose, we have simulated 5000 haloes in the mass range 5 × 109 h-1 M⊙ to 5 × 1011 h-1 M⊙ at z = 3 in cosmological N-body simulations. We confirm the relation found by Prieto et al. (2015) where haloes with fewer filaments have larger spin. We also found that this relation is more significant for higher halo masses, and for haloes with a passive (no major mergers) assembly history. Another finding is that haloes with larger spin or with fewer filaments have their filaments more perpendicularly aligned with the spin vector. Our results point to a picture in which the initial spin of haloes is well described by tidal torque theory and then gets subsequently modified in a predictable way because of the topology of the cosmic web, which in turn is given by the currently favoured Lambda cold dark matter (LCDM) model. Our spin-filament relation is a prediction from LCDM that could be tested with observations.

  20. Dynamical virial masses of Lyman-break galaxy haloes at z= 3

    Science.gov (United States)

    Weatherley, Stephen J.; Warren, Stephen J.

    2005-10-01

    We improve on our earlier dynamical estimate of the virial masses of the haloes of Lyman-break galaxies (LBGs) at redshift z= 3 by accounting for the effects of seeing, slit width and observational uncertainties. From an analysis of the small number of available rotation curves for LBGs we determine a relation Vc7= (1.9 +/- 0.2)σ between circular velocity at a radius of 7 kpc, Vc7, and central line velocity width, σ. We use this relation to transform the measured velocity widths of 32 LBGs to the distribution of circular velocities, Vc7, for the population of LBGs brighter than . We compare this distribution against the predicted distribution for the `massive-halo' model in which LBGs pinpoint all of the highest mass dark matter haloes at that epoch. The observed LBG circular velocities are smaller than the predicted circular velocities by a factor of >1.4 +/- 0.15. This is a lower limit, as we have ignored any increase of circular velocity caused by baryonic dissipation. The massive-halo model predicts a median halo virial mass of 1012.3Msolar, and a small spread of circular velocities, Vc7. Our median estimated dynamical mass is <1011.6+/-0.3Msolar, which is significantly smaller; furthermore, the spread of our derived circular velocities is much larger than the massive-halo prediction. These results are consistent with a picture which leaves some of the most massive haloes available for occupation by other populations which do not meet the LBG selection criteria. Our new dynamical mass limit is a factor of 3 larger than our earlier estimate which neglected the effects of seeing and slit width. The median halo mass recently estimated by Adelberger et al. from the measured clustering of LBGs is 1011.86+/-0.3Msolar. Our dynamical analysis appears to favour lower masses and to be more in line with the median mass predicted by the collisional starburst model of Somerville et al., which is 1011.3Msolar.

  1. Galaxy Mergers and Dark Matter Halo Mergers in LCDM: Mass, Redshift, and Mass-Ratio Dependence

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, Kyle R.; Bullock, James S.; Barton, Elizabeth J.; /UC, Irvine; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC

    2009-08-03

    We employ a high-resolution LCDM N-body simulation to present merger rate predictions for dark matter halos and investigate how common merger-related observables for galaxies - such as close pair counts, starburst counts, and the morphologically disturbed fraction - likely scale with luminosity, stellar mass, merger mass ratio, and redshift from z = 0 to z = 4. We provide a simple 'universal' fitting formula that describes our derived merger rates for dark matter halos a function of dark halo mass, merger mass ratio, and redshift, and go on to predict galaxy merger rates using number density-matching to associate halos with galaxies. For example, we find that the instantaneous merger rate of m/M > 0.3 mass ratio events into typical L {approx}> fL{sub *} galaxies follows the simple relation dN/dt {approx_equal} 0.03(1+f)Gyr{sup -1} (1+z){sup 2.1}. Despite the rapid increase in merger rate with redshift, only a small fraction of > 0.4L{sub *} high-redshift galaxies ({approx} 3% at z = 2) should have experienced a major merger (m/M > 0.3) in the very recent past (t < 100 Myr). This suggests that short-lived, merger-induced bursts of star formation should not contribute significantly to the global star formation rate at early times, in agreement with observational indications. In contrast, a fairly high fraction ({approx} 20%) of those z = 2 galaxies should have experienced a morphologically transformative merger within a virial dynamical time. We compare our results to observational merger rate estimates from both morphological indicators and pair-fraction based determinations between z = 0-2 and show that they are consistent with our predictions. However, we emphasize that great care must be made in these comparisons because the predicted observables depend very sensitively on galaxy luminosity, redshift, overall mass ratio, and uncertain relaxation timescales for merger remnants. We show that the majority of bright galaxies at z = 3 should have undergone a

  2. The scaling relations and the fundamental plane for radio halos and relics of galaxy clusters

    CERN Document Server

    Yuan, Z S; Wen, Z L

    2015-01-01

    Diffuse radio emission in galaxy clusters is known to be related to cluster mass and cluster dynamical state. We collect the observed fluxes of radio halos, relics and mini-halos for a sample of galaxy clusters from literature, and calculate their radio powers. We then obtain the values of cluster mass or mass proxies from previous observations, and also obtain the various dynamical parameters of these galaxy clusters from optical and X-ray data. The radio power of relics, halos and mini-halos are correlated with the cluster masses or mass proxies, as found by previous authors, with the correlations concerning giant radio halos being, in general, the strongest ones. We found that the inclusion of dynamical parameters as the third dimension can significantly reduce the data scatter for the scaling relations, especially for radio halos. We therefore conclude that the substructures in X-ray images of galaxy clusters and the irregular distributions of optical brightness of member galaxies can be used to quantitat...

  3. Relation between halo spin and cosmic web filaments at z~3

    CERN Document Server

    Gonzalez, Roberto E; Padilla, Nelson; Jimenez, Raul

    2016-01-01

    We investigate the spin evolution of dark matter haloes and their dependence on the number of connected filaments from the cosmic web at high redshift (spin-filament relation hereafter). To this purpose, we have simulated $5000$ haloes in the mass range $5\\times10^{9}h^{-1}M_{\\odot}$ to $5\\times10^{11}h^{-1}M_{\\odot}$ at $z=3$ in cosmological N-body simulations. We confirm the relation found by Prieto et al. 2015 where haloes with fewer filaments have larger spin. We also found that this relation is more significant for higher halo masses, and for haloes with a passive (no major mergers) assembly history. Another finding is that haloes with larger spin or with fewer filaments have their filaments more perpendicularly aligned with the spin vector. Our results point to a picture in which the initial spin of haloes is well described by tidal torque theory and then gets subsequently modified in a predictable way because of the topology of the cosmic web, which in turn is given by the currently favoured LCDM model...

  4. A mass-dependent density profile for dark matter haloes including the influence of galaxy formation

    CERN Document Server

    Di Cintio, Arianna; Dutton, Aaron A; Macciò, Andrea V; Stinson, Greg S; Knebe, Alexander

    2014-01-01

    We introduce a mass dependent density profile to describe the distribution of dark matter within galaxies, which takes into account the stellar-to-halo mass dependence of the response of dark matter to baryonic processes. The study is based on the analysis of hydrodynamically simulated galaxies from dwarf to Milky Way mass, drawn from the MaGICC project, which have been shown to match a wide range of disk scaling relationships. We find that the best fit parameters of a generic double power-law density profile vary in a systematic manner that depends on the stellar-to-halo mass ratio of each galaxy. Thus, the quantity Mstar/Mhalo constrains the inner ($\\gamma$) and outer ($\\beta$) slopes of dark matter density, and the sharpness of transition between the slopes($\\alpha$), reducing the number of free parameters of the model to two. Due to the tight relation between stellar mass and halo mass, either of these quantities is sufficient to describe the dark matter halo profile including the effects of baryons. The ...

  5. Dynamical virial masses of Lyman-break galaxy haloes at z=3

    CERN Document Server

    Weatherley, S J; Weatherley, Stephen J.; Warren, Stephen J.

    2005-01-01

    We improve on our earlier dynamical estimate of the virial masses of the haloes of Lyman-break galaxies (LBGs) at redshift z=3 by accounting for the effects of seeing, slit width, and observational uncertainties. From an analysis of the small number of available rotation curves for LBGs we determine a relation Vc7=(1.9+/-0.2)sigma between circular velocity at a radius of 7kpc, and central line velocity width. We use this relation to transform the measured velocity widths of 32 LBGs to the distribution of circular velocities, for the population of LBGs brighter than R=25.5. We compare this distribution against the predicted distribution for the 'massive-halo' model in which LBGs pinpoint all of the highest mass dark matter haloes at that epoch. The observed LBG circular velocities are smaller than the predicted circular velocities by a factor >1.4+/-0.15. This is a lower limit as we have ignored any increase of circular velocity caused by baryonic dissipation. The massive-halo model predicts a median halo viri...

  6. Is Main Sequence Galaxy Star Formation Controlled by Halo Mass Accretion?

    CERN Document Server

    Rodriguez-Puebla, Aldo; Behroozi, Peter; Faber, S M

    2015-01-01

    It is known that the galaxy stellar-to-halo mass ratio (SHMR) is nearly independent of redshift from z=0-4. This motivates us to construct a toy model in which we assume that the SMHR for central galaxies measured at redshift z~0 is independent of redshift, which implies that the star formation rate (SFR) is determined by the halo mass accretion rate, a phenomenon we call Stellar-Halo Accretion Rate Coevolution (SHARC). Moreover, we show here that the ~0.3 dex dispersion of the halo mass accretion rate (MAR) is similar to the observed dispersion of the SFR on the main sequence. In the context of bathtub-type models of galaxy formation, SHARC leads to mass-dependent constraints on the relation between SFR and MAR. The SHARC assumption is no doubt over-simplified, but we expect it to be possibly valid for central galaxies with stellar masses of 10^9 - 10^10.5 M_sol that are on the star formation main sequence. Such galaxies represent most of the life history of M_* galaxies, and therefore most of the star forma...

  7. The Dependence of the Mass Assembly History of Cold Dark Matter Halos on Environment

    CERN Document Server

    Maulbetsch, C; Colin, Pierre; Gottlöber, S; Khalatyan, A; Steinmetz, M

    2006-01-01

    We show by means of a high-resolution N-body simulation how the mass assembly histories of galaxy-size cold dark matter (CDM) halos depend on environment. Halos in high density environments form earlier and a higher fraction of their mass is assembled in major mergers,compared to low density environments. The distribution of the present--day specific mass aggregation rate is bimodal and strongly dependent on environment. While in low density environments only ~20% of the halos are not accreting mass at the present epoch, this fraction rises to ~80% at high densities. At z=1 the median of the specific aggregation rate is ~4 times larger than at z=0 and almost independent on environment. All the dependences on environment found here are critically enhanced by local processes associated to subhalos because the fraction of subhalos increases as the environment gets denser. The distribution of the halo specific mass aggregation rate as well as its dependence on environment resemble the relations for the specific s...

  8. Testing feedback-modified dark matter haloes with galaxy rotation curves: estimation of halo parameters and consistency with ΛCDM scaling relations

    Science.gov (United States)

    Katz, Harley; Lelli, Federico; McGaugh, Stacy S.; Di Cintio, Arianna; Brook, Chris B.; Schombert, James M.

    2017-04-01

    Cosmological N-body simulations predict dark matter (DM) haloes with steep central cusps (e.g. NFW). This contradicts observations of gas kinematics in low-mass galaxies that imply the existence of shallow DM cores. Baryonic processes such as adiabatic contraction and gas outflows can, in principle, alter the initial DM density profile, yet their relative contributions to the halo transformation remain uncertain. Recent high-resolution, cosmological hydrodynamic simulations by Di Cintio et al. (DC14) predict that inner density profiles depend systematically on the ratio of stellar-to-DM mass (M*/Mhalo). Using a Markov Chain Monte Carlo approach, we test the NFW and the M*/Mhalo-dependent DC14 halo models against a sample of 147 galaxy rotation curves from the new Spitzer Photometry and Accurate Rotation Curves data set. These galaxies all have extended H I rotation curves from radio interferometry as well as accurate stellar-mass-density profiles from near-infrared photometry. The DC14 halo profile provides markedly better fits to the data compared to the NFW profile. Unlike NFW, the DC14 halo parameters found in our rotation-curve fits naturally fall within two standard deviations of the mass-concentration relation predicted by Λ cold dark matter (ΛCDM) and the stellar mass-halo mass relation inferred from abundance matching with few outliers. Halo profiles modified by baryonic processes are therefore more consistent with expectations from ΛCDM cosmology and provide better fits to galaxy rotation curves across a wide range of galaxy properties than do halo models that neglect baryonic physics. Our results offer a solution to the decade long cusp-core discrepancy.

  9. The Effect of Gas Physics on the Halo Mass Function

    CERN Document Server

    Stanek, R; Evrard, A E

    2008-01-01

    Cosmological tests based on cluster counts require accurate calibration of the space density of massive halos, but most calibrations to date have ignored complex gas physics associated with halo baryons. We explore the sensitivity of the halo mass function to baryon physics using two pairs of gas-dynamic simulations that are likely to bracket the true behavior. Each pair consists of a baseline model involving only gravity and shock heating, and a refined physics model aimed at reproducing the observed scaling of the hot, intracluster gas phase. One pair consists of billion-particle re-simulations of the original 500 Mpc/h Millennium Simulation of Springel et al. (2005), run with the SPH code Gadget-2 and using a refined physics treatment approximated by preheating (PH) at high redshift. The other pair are high-resolution simulations from the adaptive-mesh refinement code ART, for which the refined treatment includes cooling, star formation, and supernova feedback (CSF). We find that, although the mass functio...

  10. The accretion history of dark matter halos II: The connections with the mass power spectrum and the density profile

    CERN Document Server

    Correa, Camila A; Schaye, Joop; Duffy, Alan R

    2015-01-01

    We explore the relation between the structure and mass accretion histories of dark matter halos using a suite of cosmological simulations. We confirm that the formation time, defined as the time when the virial mass of the main progenitor equals the mass enclosed within the scale radius, correlates strongly with concentration. We provide a semi-analytic model for halo mass history that combines analytic relations with fits to simulations. This model has the functional form, $M(z) = M_{0}(1+z)^{\\alpha}e^{\\beta z}$, where the parameters $\\alpha$ and $\\beta$ are directly correlated with concentration. We then combine this model for the halo mass history with the analytic relations between $\\alpha$, $\\beta$ and the linear power spectrum derived by Correa et al. (2014) to establish the physical link between halo concentration and the initial density perturbation field. Finally, we provide fitting formulas for the halo mass history as well as numerical routines, we derive the accretion rate as a function of halo ma...

  11. The Eating Habits of Milky Way-mass Halos: Destroyed Dwarf Satellites and the Metallicity Distribution of Accreted Stars

    Science.gov (United States)

    Deason, Alis J.; Mao, Yao-Yuan; Wechsler, Risa H.

    2016-04-01

    We study the mass spectrum of destroyed dwarfs that contribute to the accreted stellar mass of Milky Way (MW)-mass (Mvir ˜ 1012.1 M⊙) halos using a suite of 45 zoom-in dissipationless simulations. Empirical models are employed to relate (peak) subhalo mass to dwarf stellar mass, and we use constraints from z = 0 observations and hydrodynamical simulations to estimate the metallicity distribution of the accreted stellar material. The dominant contributors to the accreted stellar mass are relatively massive dwarfs with Mstar ˜ 108-1010M⊙. Halos with more quiescent accretion histories tend to have lower mass progenitors (108-109 M⊙), and lower overall accreted stellar masses. Ultra-faint mass (Mstar 108 M⊙ can contribute a considerable fraction (˜20%-60%) of metal-poor stars if their metallicity distributions have significant metal-poor tails. Finally, we find that the generic assumption of a quiescent assembly history for the MW halo seems to be in tension with the mass spectrum of its surviving dwarfs. We suggest that the MW could be a “transient fossil” a quiescent halo with a recent accretion event(s) that disguises the preceding formation history of the halo.

  12. Mapping stellar content to dark matter halos. II. Halo mass is the main driver of galaxy quenching

    CERN Document Server

    Zu, Ying

    2015-01-01

    We develop a simple yet comprehensive method to distinguish the underlying drivers of galaxy quenching, using the clustering and galaxy-galaxy lensing of red and blue galaxies in SDSS. Building on the iHOD framework developed by Zu & Mandelbaum (2015a), we consider two quenching scenarios: 1) a "halo" quenching model in which halo mass is the sole driver for turning off star formation in both centrals and satellites; and 2) a "hybrid" quenching model in which the quenched fraction of galaxies depends on their stellar mass while the satellite quenching has an extra dependence on halo mass. The two best-fit models describe the red galaxy clustering and lensing equally well, but halo quenching provides significantly better fits to the blue galaxies above $10^{11} M_\\odot/h^2$. The halo quenching model also correctly predicts the average halo mass of the red and blue centrals, showing excellent agreement with the direct weak lensing measurements of locally brightest galaxies. Models in which quenching is not ...

  13. The dependence of AGN activity on stellar and halo mass in Semi-Analytic Models

    CERN Document Server

    Fontanot, Fabio; De Lucia, Gabriella; Bosch, Frank C van den; Somerville, Rachel S; Kang, Xi

    2010-01-01

    AGN feedback is believed to play an important role in shaping a variety of observed galaxy properties, as well as the evolution of their stellar masses and star formation rates. In particular, in the current theoretical paradigm of galaxy formation, AGN feedback is believed to play a crucial role in regulating the levels of activity in galaxies, in relatively massive halos at low redshift. Only in recent years, however, detailed statistical information on the dependence of galaxy activity on stellar mass, parent halo mass and hierarchy has become available. In this paper, we compare the fractions of galaxies belonging to different activity classes (star-forming, AGN and radio active) with predictions from four different and independently developed semi-analytical models. We adopt empirical relations to convert physical properties into observables (H_alpha emission lines, OIII line strength and radio power). We demonstrate that all models used in this study reproduce the overall distributions of galaxies belon...

  14. The (dark) halo-to-stellar mass ratio in the Spitzer Survey of Stellar Structure in Galaxies (S$^4$G)

    CERN Document Server

    Díaz-García, Simón; Laurikainen, Eija; Leaman, Ryan

    2016-01-01

    We use 3.6 $\\mu$m photometry for 1154 disk galaxies ($i<65^{\\circ}$) in the Spitzer Survey of Stellar Structure in Galaxies (S$^{4}$G, Sheth et al. 2010) to obtain the stellar component of the circular velocity. By combining the disk+bulge rotation curves with HI line width measurements from the literature, we estimate the ratio of the halo-to-stellar mass ($M_{\\rm halo}/M_{\\ast}$) within the optical disk, and compare it to the total stellar mass ($M_{\\ast}$). We find the $M_{\\rm halo}/M_{\\ast}$-$M_{\\ast}$ relation in good agreement with the best-fit model at z$\\approx$0 in $\\Lambda$CDM cosmological simulations (e.g. Moster et al. 2010), assuming that the dark matter halo within the optical radius comprises a constant fraction ($\\sim4\\%$) of its total mass.

  15. Galaxy and Mass Assembly (GAMA): The halo mass of galaxy groups from maximum-likelihood weak lensing

    CERN Document Server

    Han, Jiaxin; Frenk, Carlos S; Mandelbaum, Rachel; Norberg, Peder; Schneider, Michael D; Peacock, John A; Jing, Yipeng; Baldry, Ivan; Bland-Hawthorn, Joss; Brough, Sarah; Brown, Michael J I; Loveday, Jon

    2014-01-01

    We present a maximum-likelihood weak lensing analysis of the mass distribution in optically selected spectroscopic Galaxy Groups (G3Cv1) in the Galaxy And Mass Assembly (GAMA) survey, using background Sloan Digital Sky Survey (SDSS) photometric galaxies. The scaling of halo mass, $M_h$, with various group observables is investigated. Our main results are: 1) the measured relations of halo mass with group luminosity, virial volume and central galaxy stellar mass, $M_\\star$, agree very well with predictions from mock group catalogues constructed from a GALFORM semi-analytical galaxy formation model implemented in the Millennim $\\Lambda$CDM N-body simulation; 2) the measured relations of halo mass with velocity dispersion and projected half-abundance radius show weak tension with mock predictions, hinting at problems in the mock galaxy dynamics and their small scale distribution; 3) the median $M_h|M_\\star$ measured from weak lensing depends more sensitively on the dispersion in $M_\\star$ at fixed $M_h$ than it ...

  16. Predicting weak lensing statistics from halo mass reconstructions - Final Paper

    Energy Technology Data Exchange (ETDEWEB)

    Everett, Spencer [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-08-20

    As dark matter does not absorb or emit light, its distribution in the universe must be inferred through indirect effects such as the gravitational lensing of distant galaxies. While most sources are only weakly lensed, the systematic alignment of background galaxies around a foreground lens can constrain the mass of the lens which is largely in the form of dark matter. In this paper, I have implemented a framework to reconstruct all of the mass along lines of sight using a best-case dark matter halo model in which the halo mass is known. This framework is then used to make predictions of the weak lensing of 3,240 generated source galaxies through a 324 arcmin² field of the Millennium Simulation. The lensed source ellipticities are characterized by the ellipticity-ellipticity and galaxy-mass correlation functions and compared to the same statistic for the intrinsic and ray-traced ellipticities. In the ellipticity-ellipticity correlation function, I and that the framework systematically under predicts the shear power by an average factor of 2.2 and fails to capture correlation from dark matter structure at scales larger than 1 arcminute. The model predicted galaxy-mass correlation function is in agreement with the ray-traced statistic from scales 0.2 to 0.7 arcminutes, but systematically underpredicts shear power at scales larger than 0.7 arcminutes by an average factor of 1.2. Optimization of the framework code has reduced the mean CPU time per lensing prediction by 70% to 24 ± 5 ms. Physical and computational shortcomings of the framework are discussed, as well as potential improvements for upcoming work.

  17. THE CONTRIBUTION OF HALOS WITH DIFFERENT MASS RATIOS TO THE OVERALL GROWTH OF CLUSTER-SIZED HALOS

    Energy Technology Data Exchange (ETDEWEB)

    Lemze, Doron; Ford, Holland C.; Medezinski, Elinor [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Postman, Marc; Koekemoer, Anton [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208 (United States); Genel, Shy [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Balestra, Italo; Nonino, Mario; Biviano, Andrea [INAF/Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, I-34143 Trieste (Italy); Donahue, Megan [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-2320 (United States); Kelson, Daniel; Voit, G. Mark [Carnegie Institute for Science, Carnegie Observatories, Pasadena, CA (United States); Mercurio, Amata [INAF/Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli (Italy); Rosati, Piero [European Southern Observatory, Karl-Schwarzschild Strasse 2, D-85748 Garching (Germany); Umetsu, Keiichi [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Sand, David [Department of Physics, Texas Tech University, Box 41051, Lubbock, TX 79409-1051 (United States); Meneghetti, Massimo [INAF, Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Melchior, Peter [Center for Cosmology and Astro-Particle Physics, The Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210 (United States); Newman, Andrew B. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States); Bhatti, Waqas A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); and others

    2013-10-20

    We provide a new observational test for a key prediction of the ΛCDM cosmological model: the contributions of mergers with different halo-to-main-cluster mass ratios to cluster-sized halo growth. We perform this test by dynamically analyzing 7 galaxy clusters, spanning the redshift range 0.13 < z{sub c} < 0.45 and caustic mass range 0.4-1.5 10{sup 15} h{sub 0.73}{sup -1} M{sub ☉}, with an average of 293 spectroscopically confirmed bound galaxies to each cluster. The large radial coverage (a few virial radii), which covers the whole infall region, with a high number of spectroscopically identified galaxies enables this new study. For each cluster, we identify bound galaxies. Out of these galaxies, we identify infalling and accreted halos and estimate their masses and their dynamical states. Using the estimated masses, we derive the contribution of different mass ratios to cluster-sized halo growth. For mass ratios between ∼0.2 and ∼0.7, we find a ∼1σ agreement with ΛCDM expectations based on the Millennium simulations I and II. At low mass ratios, ∼< 0.2, our derived contribution is underestimated since the detection efficiency decreases at low masses, ∼2 × 10{sup 14} h{sub 0.73}{sup -1} M{sub ☉}. At large mass ratios, ∼> 0.7, we do not detect halos probably because our sample, which was chosen to be quite X-ray relaxed, is biased against large mass ratios. Therefore, at large mass ratios, the derived contribution is also underestimated.

  18. The Correlation Between Halo Mass and Stellar Mass for the Most Massive Galaxies in the Universe

    CERN Document Server

    Tinker, Jeremy L; Guo, Hong; Leauthaud, Alexie; Maraston, Claudia; Masters, Karen; Montero-Dorta, Antonio D; Thomas, Daniel; Tojeiro, Rita; Weiner, Benjamin; Zehavi, Idit; Olmstead, Matthew D

    2016-01-01

    We present measurements of the clustering of galaxies as a function of their stellar mass in the Baryon Oscillation Spectroscopic Survey. We compare the clustering of samples using 12 different methods for estimating stellar mass, isolating the method that has the smallest scatter at fixed halo mass. In this test, the stellar mass estimate with the smallest errors yields the highest amplitude of clustering at fixed number density. We find that the PCA stellar masses of Chen etal (2012) clearly have the tightest correlation with halo mass. The PCA masses use the full galaxy spectrum, differentiating them from other estimates that only use optical photometric information. Using the PCA masses, we measure the large-scale bias as a function of Mgal for galaxies with logMgal>=11.4, correcting for incompleteness at the low-mass end of our measurements. Using the abundance-matching ansatz to connect dark matter halo mass to stellar mass, we construct theoretical models of b(Mgal) that match the same stellar mass fun...

  19. Alignments of dark matter halos with large-scale tidal fields: mass and redshift dependence

    CERN Document Server

    Chen, Sijie; Mo, H J; Shi, Jingjing

    2016-01-01

    Large scale tidal field estimated directly from the distribution of dark matter halos is used to investigate how halo shapes and spin vectors are aligned with the cosmic web. The major, intermediate and minor axes of halos are aligned with the corresponding tidal axes, and halo spin axes tend to be parallel with the intermediate axes and perpendicular to the major axes of tidal field. The strengths of these alignments generally increase with halo mass and redshift, but the dependencies are only through the peak height, {\

  20. Development of a Full Ice-cream Cone Model for Halo Coronal Mass Ejections

    Science.gov (United States)

    Na, Hyeonock; Moon, Y.-J.; Lee, Harim

    2017-04-01

    It is essential to determine three-dimensional parameters (e.g., radial speed, angular width, and source location) of coronal mass ejections (CMEs) for the space weather forecast. In this study, we investigate which cone type represents a halo CME morphology using 29 CMEs (12 Solar and Heliospheric Observatory (SOHO)/Large Angle and Spectrometric Coronagraph (LASCO) halo CMEs and 17 Solar Terrestrial Relations Observatory (STEREO)/Sun-Earth Connection Coronal and Heliospheric Investigation COR2 halo CMEs) from 2010 December to 2011 June. These CMEs are identified as halo CMEs by one spacecraft (SOHO or one of STEREO A and B) and limb ones by the other spacecraft (One of STEREO A and B or SOHO). From cone shape parameters of these CMEs, such as their front curvature, we find that the CME observational structures are much closer to a full ice-cream cone type than a shallow ice-cream cone type. Thus, we develop a full ice-cream cone model based on a new methodology that the full ice-cream cone consists of many flat cones with different heights and angular widths to estimate the three-dimensional parameters of the halo CMEs. This model is constructed by carrying out the following steps: (1) construct a cone for a given height and angular width, (2) project the cone onto the sky plane, (3) select points comprising the outer boundary, and (4) minimize the difference between the estimated projection speeds with the observed ones. By applying this model to 12 SOHO/LASCO halo CMEs, we find that 3D parameters from our method are similar to those from other stereoscopic methods (i.e., a triangulation method and a Graduated Cylindrical Shell model).

  1. Understanding the core-halo relation of quantum wave dark matter from 3D simulations.

    Science.gov (United States)

    Schive, Hsi-Yu; Liao, Ming-Hsuan; Woo, Tak-Pong; Wong, Shing-Kwong; Chiueh, Tzihong; Broadhurst, Tom; Hwang, W-Y Pauchy

    2014-12-31

    We examine the nonlinear structure of gravitationally collapsed objects that form in our simulations of wavelike cold dark matter, described by the Schrödinger-Poisson (SP) equation with a particle mass ∼10(-22)  eV. A distinct gravitationally self-bound solitonic core is found at the center of every halo, with a profile quite different from cores modeled in the warm or self-interacting dark matter scenarios. Furthermore, we show that each solitonic core is surrounded by an extended halo composed of large fluctuating dark matter granules which modulate the halo density on a scale comparable to the diameter of the solitonic core. The scaling symmetry of the SP equation and the uncertainty principle tightly relate the core mass to the halo specific energy, which, in the context of cosmological structure formation, leads to a simple scaling between core mass (Mc) and halo mass (Mh), Mc∝a(-1/2)Mh(1/3), where a is the cosmic scale factor. We verify this scaling relation by (i) examining the internal structure of a statistical sample of virialized halos that form in our 3D cosmological simulations and by (ii) merging multiple solitons to create individual virialized objects. Sufficient simulation resolution is achieved by adaptive mesh refinement and graphic processing units acceleration. From this scaling relation, present dwarf satellite galaxies are predicted to have kiloparsec-sized cores and a minimum mass of ∼10(8)M⊙, capable of solving the small-scale controversies in the cold dark matter model. Moreover, galaxies of 2×10(12)M⊙ at z=8 should have massive solitonic cores of ∼2×10(9)M⊙ within ∼60  pc. Such cores can provide a favorable local environment for funneling the gas that leads to the prompt formation of early stellar spheroids and quasars.

  2. The Contribution of Halos with Different Mass Ratios to the Overall Growth of Cluster-Sized Halos

    CERN Document Server

    Lemze, Doron; Genel, Shy; Ford, Holland C; Balestra, Italo; Donahue, Megan; Kelson, Daniel; Nonino, Mario; Mercurio, Amata; Biviano, Andrea; Rosati, Piero; Umetsu, Keiichi; Sand, David; Koekemoer, Anton; Meneghetti, Massimo; Melchior, Peter; Newman, Andrew B; Bhatti, Waqas A; Voit, G Mark; Medezinski, Elinor; Zitrin, Adi; Zheng, Wei; Broadhurst, Tom; Bartelmann, Matthias; Benitez, Narciso; Bouwens, Rychard; Bradley, Larry; Coe, Dan; Graves, Genevieve; Grillo, Claudio; Infante, Leopoldo; Jimenez-Teja, Yolanda; Jouvel, Stephanie; Lahav, Ofer; Maoz, Dan; Merten, Julian; Molino, Alberto; Moustakas, John; Moustakas, Leonidas; Ogaz, Sara; Scodeggio, Marco; Seitz, Stella

    2013-01-01

    We provide a new observational test for a key prediction of the \\Lambda CDM cosmological model: the contributions of mergers with different halo-to-main-cluster mass ratios to cluster-sized halo growth. We perform this test by dynamically analyzing seven galaxy clusters, spanning the redshift range $0.13 < z_c < 0.45$ and caustic mass range $0.4-1.5$ $10^{15} h_{0.73}^{-1}$ M$_{\\odot}$, with an average of 293 spectroscopically-confirmed bound galaxies to each cluster. The large radial coverage (a few virial radii), which covers the whole infall region, with a high number of spectroscopically identified galaxies enables this new study. For each cluster, we identify bound galaxies. Out of these galaxies, we identify infalling and accreted halos and estimate their masses and their dynamical states. Using the estimated masses, we derive the contribution of different mass ratios to cluster-sized halo growth. For mass ratios between ~0.2 and ~0.7, we find a ~1 $\\sigma$ agreement with \\Lambda CDM expectations ...

  3. The Faber-Jackson relation and Fundamental Plane from halo abundance matching

    Science.gov (United States)

    Desmond, Harry; Wechsler, Risa H.

    2017-02-01

    The Fundamental Plane (FP) describes the relation between the stellar mass, size, and velocity dispersion of elliptical galaxies; the Faber-Jackson relation (FJR) is its projection on to {mass, velocity} space. In this work, we re-deploy and expand the framework of Desmond & Wechsler to ask whether abundance matching-based Λ-cold dark matter models which have shown success in matching the spatial distribution of galaxies are also capable of explaining key properties of the FJR and FP, including their scatter. Within our framework, agreement with the normalization of the FJR requires haloes to expand in response to disc formation. We find that the tilt of the FP may be explained by a combination of the observed non-homology in galaxy structure and the variation in mass-to-light ratio produced by abundance matching with a universal initial mass function, provided that the anisotropy of stellar motions is taken into account. However, the predicted scatter around the FP is considerably increased by situating galaxies in cosmologically motivated haloes due to the variations in halo properties at fixed stellar mass and appears to exceed that of the data. This implies that additional correlations between galaxy and halo variables may be required to fully reconcile these models with elliptical galaxy scaling relations.

  4. Cluster abundance in chameleon f(R) gravity I: toward an accurate halo mass function prediction

    Science.gov (United States)

    Cataneo, Matteo; Rapetti, David; Lombriser, Lucas; Li, Baojiu

    2016-12-01

    We refine the mass and environment dependent spherical collapse model of chameleon f(R) gravity by calibrating a phenomenological correction inspired by the parameterized post-Friedmann framework against high-resolution N-body simulations. We employ our method to predict the corresponding modified halo mass function, and provide fitting formulas to calculate the enhancement of the f(R) halo abundance with respect to that of General Relativity (GR) within a precision of lesssim 5% from the results obtained in the simulations. Similar accuracy can be achieved for the full f(R) mass function on the condition that the modeling of the reference GR abundance of halos is accurate at the percent level. We use our fits to forecast constraints on the additional scalar degree of freedom of the theory, finding that upper bounds competitive with current Solar System tests are within reach of cluster number count analyses from ongoing and upcoming surveys at much larger scales. Importantly, the flexibility of our method allows also for this to be applied to other scalar-tensor theories characterized by a mass and environment dependent spherical collapse.

  5. Cluster abundance in chameleon $f(R)$ gravity I: toward an accurate halo mass function prediction

    CERN Document Server

    Cataneo, Matteo; Lombriser, Lucas; Li, Baojiu

    2016-01-01

    We refine the mass and environment dependent spherical collapse model of chameleon $f(R)$ gravity by calibrating a phenomenological correction inspired by the parameterized post-Friedmann framework against high-resolution $N$-body simulations. We employ our method to predict the corresponding modified halo mass function, and provide fitting formulas to calculate the fractional enhancement of the $f(R)$ halo abundance with respect to that of General Relativity (GR) within a precision of $\\lesssim 5\\%$ from the results obtained in the simulations. Similar accuracy can be achieved for the full $f(R)$ mass function on the condition that the modeling of the reference GR abundance of halos is accurate at the percent level. We use our fits to forecast constraints on the additional scalar degree of freedom of the theory, finding that upper bounds competitive with current Solar System tests are within reach of cluster number count analyses from ongoing and upcoming surveys at much larger scales. Importantly, the flexi...

  6. Galaxy Mass Models: MOND versus Dark Matter Halos

    CERN Document Server

    Randriamampandry, Toky

    2014-01-01

    Mass models of 15 nearby dwarf and spiral galaxies are presented. The galaxies are selected to be homogeneous in terms of the method used to determine their distances, the sampling of their rotation curves (RCs) and the mass-to-light ratio (M/L) of their stellar contributions, which will minimize the uncertainties on the mass model results. Those RCs are modeled using the MOdified Newtonian Dynamics (MOND) prescription and the observationally motivated pseudo-isothermal (ISO) dark matter (DM) halo density distribution. For the MOND models with fixed (M/L), better fits are obtained when the constant a$_{0}$ is allowed to vary, giving a mean value of (1.13 $\\pm$ 0.50) $\\times$ 10$^{-8}$ cm s$^{-2}$, compared to the standard value of 1.21 $\\times$ 10$^{-8}$ cm s$^{-2}$. Even with a$_{0}$ as a free parameter, MOND provides acceptable fits (reduced $\\chi^{2}_{r}$ $<$ 2) for only 60% (9/15) of the sample. The data suggest that galaxies with higher central surface brightnesses tend to favor higher values of the c...

  7. Full Halo Coronal Mass Ejections: Arrival at the Earth

    CERN Document Server

    Shen, Chenglong; Pan, Zonghao; Miao, Bin; Ye, Pinzhong; Wang, S

    2014-01-01

    A geomagnetic storm is mainly caused by a front-side coronal mass ejection (CME) hitting the Earth and then interacting with the magnetosphere. However, not all front-side CMEs can hit the Earth. Thus, which CMEs hit the Earth and when they do so are important issues in the study and forecasting of space weather. In our previous work (Shen et al., 2013), the de-projected parameters of the full-halo coronal mass ejections (FHCMEs) that occurred from 2007 March 1 to 2012 May 31 were estimated, and there are 39 front-side events could be fitted by the GCS model. In this work, we continue to study whether and when these front-side FHCMEs (FFHCMEs) hit the Earth. It is found that 59\\% of these FFHCMEs hit the Earth, and for central events, whose deviation angles $\\epsilon$, which are the angles between the propagation direction and the Sun-Earth line, are smaller than 45 degrees, the fraction increases to 75\\%. After checking the deprojected angular widths of the CMEs, we found that all of the Earth-encountered CM...

  8. Dark matter haloes determine the masses of supermassive black holes

    CERN Document Server

    Booth, C M

    2009-01-01

    The energy and momentum deposited by the radiation from accretion onto the supermassive black holes (BHs) that reside at the centres of virtually all galaxies can halt or even reverse gas inflow, providing a natural mechanism for supermassive BHs to regulate their growth and to couple their properties to those of their host galaxies. However, it remains unclear whether this self-regulation occurs on the scale at which the BH is gravitationally dominant, on that of the stellar bulge, the galaxy, or that of the entire dark matter halo. To answer this question, we use self-consistent simulations of the co-evolution of the BH and galaxy populations that reproduce the observed correlations between the masses of the BHs and the properties of their host galaxies. We first confirm unambiguously that the BHs regulate their growth: the amount of energy that the BHs inject into their surroundings remains unchanged when the fraction of the accreted rest mass energy that is injected, is varied by four orders of magnitude....

  9. Mergers and mass accretion for infalling halos both end well outside cluster virial radii

    Energy Technology Data Exchange (ETDEWEB)

    Behroozi, Peter S. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Wechsler, Risa H.; Lu, Yu; Busha, Michael T. [Physics Department, Stanford University, Department of Particle and Particle Astrophysics, SLAC National Accelerator Laboratory, Kavli Institute for Particle Astrophysics and Cosmology Stanford, CA 94305 (United States); Hahn, Oliver [Institute for Astronomy, ETH Zurich, 8093-CH Zurich (Switzerland); Klypin, Anatoly [Astronomy Department, New Mexico State University, Las Cruces, NM 88003 (United States); Primack, Joel R., E-mail: behroozi@stsci.edu [Department of Physics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States)

    2014-06-01

    We find that infalling dark matter halos (i.e., the progenitors of satellite halos) begin losing mass well outside the virial radius of their eventual host halos. The peak mass occurs at a range of clustercentric distances, with median and 68th percentile range of 1.8{sub −1.0}{sup +2.3} R{sub vir,host} for progenitors of z = 0 satellites. The peak circular velocity for infalling halos occurs at significantly larger distances (3.7{sub −2.2}{sup +3.3} R{sub vir,host} at z = 0). This difference arises because different physical processes set peak circular velocity (typically, ∼1:5 and larger mergers which cause transient circular velocity spikes) and peak mass (typically, smooth accretion) for infalling halos. We find that infalling halos also stop having significant mergers well before they enter the virial radius of their eventual hosts. Mergers larger than a 1:40 ratio in halo mass end for infalling halos at similar clustercentric distances (∼1.9 R {sub vir,} {sub host}) as the end of overall mass accretion. However, mergers larger than 1:3 typically end for infalling halos at more than four virial radial away from their eventual hosts. This limits the ability of mergers to affect quenching and morphology changes in clusters. We also note that the transient spikes which set peak circular velocity may lead to issues with abundance matching on that parameter, including unphysical galaxy stellar mass growth profiles near clusters; we propose a simple observational test to check if a better halo proxy for galaxy stellar mass exists.

  10. Mergers and mass accretion for infalling halos both end well outside cluster virial radii

    Energy Technology Data Exchange (ETDEWEB)

    Behroozi, Peter S.; Wechsler, Risa H.; Lu, Yu; Hahn, Oliver; Busha, Michael T.; Klypin, Anatoly; Primack, Joel R.

    2014-05-14

    We find that infalling dark matter halos (i.e., the progenitors of satellite halos) begin losing mass well outside the virial radius of their eventual host halos. The peak mass occurs at a range of clustercentric distances, with median and 68th percentile range of $1.8^{+2.3}_{-1.0} \\,R_\\mathrm{vir,host}$ for progenitors of z = 0 satellites. The peak circular velocity for infalling halos occurs at significantly larger distances ($3.7^{+3.3}_{-2.2} \\,R_\\mathrm{vir,host}$ at z = 0). This difference arises because different physical processes set peak circular velocity (typically, ~1:5 and larger mergers which cause transient circular velocity spikes) and peak mass (typically, smooth accretion) for infalling halos. We find that infalling halos also stop having significant mergers well before they enter the virial radius of their eventual hosts. Mergers larger than a 1:40 ratio in halo mass end for infalling halos at similar clustercentric distances (~1.9 R vir, host) as the end of overall mass accretion. However, mergers larger than 1:3 typically end for infalling halos at more than four virial radial away from their eventual hosts. This limits the ability of mergers to affect quenching and morphology changes in clusters. We also note that the transient spikes which set peak circular velocity may lead to issues with abundance matching on that parameter, including unphysical galaxy stellar mass growth profiles near clusters; we propose a simple observational test to check if a better halo proxy for galaxy stellar mass exists.

  11. The Warm DM halo mass function below the cut-off scale

    CERN Document Server

    Angulo, Raul E; Abel, Tom

    2013-01-01

    Warm Dark Matter (WDM) cosmologies are a viable alternative to the Cold Dark Matter (CDM) scenario. Unfortunately, an accurate scrutiny of the WDM predictions with N-body simulations has proven difficult due to numerical artifacts. Here, we report on cosmological simulations that, for the first time, are devoid of those problems, and thus, are able to accurately resolve the WDM halo mass function well below the cut-off. We discover a complex picture, with perturbations at different evolutionary stages populating different ranges in the halo mass function. On the smallest mass scales we can resolve, identified objects are typically centres of filaments that are starting to collapse. On intermediate mass scales, objects typically correspond to fluctuations that have collapsed and are in the process of relaxation, whereas the high mass end is dominated by objects similar to haloes identified in CDM simulations. When explicitly show how the formation of low-mass haloes is suppressed, which translates into a stron...

  12. The Dark Matter Halos of Moderate Luminosity X-ray AGN as Determined from Weak Gravitational Lensing and Host Stellar Masses

    CERN Document Server

    Leauthaud, A; Civano, F; Coil, A L; Bundy, K; Massey, R; Schramm, M; Schulze, A; Capak, P; Elvis, M; Kulier, A; Rhodes, J

    2014-01-01

    Understanding the relationship between galaxies hosting active galactic nuclei (AGN) and the dark matter halos in which they reside is key to constraining how black-hole fueling is triggered and regulated. Previous efforts have relied on simple halo mass estimates inferred from clustering, weak gravitational lensing, or halo occupation distribution modeling. In practice, these approaches remain uncertain because AGN, no matter how they are identified, potentially live a wide range of halo masses with an occupation function whose general shape and normalization are poorly known. In this work, we show that better constraints can be achieved through a rigorous comparison of the clustering, lensing, and cross-correlation signals of AGN hosts to a fiducial stellar-to-halo mass relation (SHMR) derived for all galaxies. Our technique exploits the fact that the global SHMR can be measured with much higher accuracy than any statistic derived from AGN samples alone. Using 382 moderate luminosity X-ray AGN at z<1 fro...

  13. Stellar Mass-gap as a Probe of Halo Assembly History and Concentration: Youth Hidden among Old Fossils

    Science.gov (United States)

    Deason, A. J.; Conroy, C.; Wetzel, A. R.; Tinker, J. L.

    2013-11-01

    We investigate the use of the halo mass-gap statistic—defined as the logarithmic difference in mass between the host halo and its most massive satellite subhalo—as a probe of halo age and concentration. A cosmological N-body simulation is used to study N ~ 25, 000 group/cluster-sized halos in the mass range 1012.5 history significantly affects galaxy properties.

  14. A relationship between halo mass, cooling, active galactic nuclei heating and the co-evolution of massive black holes

    Science.gov (United States)

    Main, R. A.; McNamara, B. R.; Nulsen, P. E. J.; Russell, H. R.; Vantyghem, A. N.

    2017-02-01

    We derive X-ray mass, luminosity, and temperature profiles for 45 galaxy clusters to explore relationships between halo mass, active galactic nuclei (AGN) feedback, and central cooling time. We find that radio-mechanical feedback power (referred to here as `AGN power') in central cluster galaxies correlates with halo mass as Pmech ∝ M1.55 ± 0.26, but only in haloes with central atmospheric cooling times shorter than 1 Gyr. The trend of AGN power with halo mass is consistent with the scaling expected from a self-regulating AGN feedback loop, as well as with galaxy and central black hole co-evolution along the MBH-σ relation. AGN power in clusters with central atmospheric cooling times longer than ˜1 Gyr typically lies two orders of magnitude below those with shorter central cooling times. Galaxies centred in clusters with long central cooling times nevertheless experience ongoing and occasionally powerful AGN outbursts. We further investigate the impact of feedback on cluster scaling relations. We find L-T and M-T relations in clusters with direct evidence of feedback which are steeper than self-similar, but not atypical compared to previous studies of the full cluster population. While the gas mass rises, the stellar mass remains nearly constant with rising total mass, consistent with earlier studies. This trend is found regardless of central cooling time, implying tight regulation of star formation in central galaxies as their haloes grew, and long-term balance between AGN heating and atmospheric cooling. Our scaling relations are presented in forms that can be incorporated easily into galaxy evolution models.

  15. The Eating Habits of Milky Way Mass Halos: Destroyed Dwarf Satellites and the Metallicity Distribution of Accreted Stars

    CERN Document Server

    Deason, Alis J; Wechsler, Risa H

    2016-01-01

    We study the mass spectrum of destroyed dwarfs that contribute to the accreted stellar mass of Milky Way (MW) mass M_vir ~ 10^12.1 M_sun) halos using a suite of 45 zoom-in, dissipationless simulations. Empirical models are employed to relate (peak) subhalo mass to dwarf stellar mass, and we use constraints from z=0 observations and hydrodynamical simulations to estimate the metallicity distribution of the accreted stellar material. The dominant contributors to the accreted stellar mass are relatively massive dwarfs with M_star ~ 10^8-10^10 M_sun. Halos with more quiescent accretion histories tend to have lower mass progenitors (10^8-10^9 M_sun), and lower overall accreted stellar masses. Ultra-faint mass (M_star 10^8 M_sun can contribute a considerable fraction (~20-60 %) of metal-poor stars if their metallicity distributions have significant metal-poor tails. Finally, we find that the generic assumption of a quiescent assembly history for the MW halo seems to be in tension with the mass spectrum of its surv...

  16. AGN Feedback, Host Halo Mass and Central Cooling Time: Implications for Galaxy Formation Efficiency and $M_{BH} - \\sigma$

    CERN Document Server

    Main, Robert; Nulsen, Paul; Russell, Helen; Vantyghem, Adrian

    2015-01-01

    We derive X-ray mass, luminosity, and temperature profiles for 45 galaxy clusters to explore relationships between halo mass, AGN feedback, and central cooling time. We find that radio--mechanical feedback power (referred to here as "AGN power") in central cluster galaxies correlates with halo mass, but only in halos with central atmospheric cooling times shorter than 1 Gyr. This timescale corresponds approximately to the cooling time (entropy) threshold for the onset of cooling instabilities and star formation in central galaxies (Rafferty et al. 2008). No correlation is found in systems with central cooling times greater than 1 Gyr. The trend with halo mass is consistent with self-similar scaling relations assuming cooling is regulated by feedback. The trend is also consistent with galaxy and central black hole co-evolution along the $M_{BH} - \\sigma $ relation. AGN power further correlates with X-ray gas mass and the host galaxy's K-band luminosity. AGN power in clusters with central atmospheric cooling ti...

  17. The Clustering and Halo Masses of Star Forming Galaxies at z<1

    CERN Document Server

    Dolley, Tim; Weiner, Benjamin J; Brodwin, Mark; Kochanek, C S; Pimbblet, Kevin A; Palamara, David P; Jannuzi, Buell T; Dey, Arjun; Atlee, David W; Beare, Richard

    2014-01-01

    We present clustering measurements and halo masses of star forming galaxies at 0.2 0.4 our sample is dominated by luminous infrared galaxies (LIRGs, L_TIR > 10^11 Lsun) and is comprised entirely of LIRGs and ultra-luminous infrared galaxies (ULIRGs, L_TIR > 10^12 Lsun) at z > 0.6. We observe weak clustering of r_0 = 3-6 Mpc/h for almost all of our star forming samples. We find that the clustering and halo mass depend on L_TIR at all redshifts, where galaxies with higher L_TIR (hence higher SFRs) have stronger clustering. Galaxies with the highest SFRs at each redshift typically reside within dark matter halos of M_halo ~ 10^12.9 Msun/h. This is consistent with a transitional halo mass, above which star formation is largely truncated, although we cannot exclude that ULIRGs reside within higher mass halos. By modeling the clustering evolution of halos, we connect our star forming galaxy samples to their local descendants. Most star forming galaxies at z 10^11.7 Lsun) at 0.6

  18. Simulations of isolated dwarf galaxies formed in dark matter halos with different mass assembly histories

    CERN Document Server

    González-Samaniego, A; Avila-Reese, V; Rodríguez-Puebla, A; Valenzuela, O

    2013-01-01

    We present high-resolution N-body/Hydrodynamics simulations of dwarf galaxies formed in isolated CDM halos with the same virial mass, Mv~2.5x10^10 Msun at z=0, in order to (1) study the mass assembly histories (MAHs) of the halo, stars, and gas components, and (2) explore the effects of the halo MAHs on the stellar/baryonic assembly of the simulated dwarfs and on their z~0 properties. Overall, the simulated dwarfs are roughly consistent with observations. Our main results are: a) The stellar-to-halo mass ratio is ~0.01 and remains roughly constant since z~1 (the stellar MAHs follow closely the halo MAHs), with a smaller value at higher z's for those halos that assemble their mass later. b) The evolution of the galaxy gas fraction, fg, is episodic and higher, most of the time, than the stellar fraction. When fg decreases (increases), the gas fraction in the halo typically increases (decreases), showing that the SN driven outflows play an important role in regulating the gas fractions -and hence the SFR- of the...

  19. Dark Matter Halos: Velocity Anisotropy -- Density Slope Relation

    CERN Document Server

    Zait, Amir; Shlosman, Isaac

    2007-01-01

    Dark matter (DM) halos formed in CDM cosmologies seem to be characterized by a power law phase-space density profile. The density of the DM halos is often fitted by the NFW profile but a better fit is provided by the Sersic fitting formula. These relations are empirically derived from cosmological simulations of structure formation but have not yet been explained on a first principle basis. Here we solve the Jeans equation under the assumption of a spherical DM halo in dynamical equilibrium, that obeys a power law phase space density and either the NFW-like or the Sersic density profile. We then calculate the velocity anisotropy, beta(r), analytically. Our main result is that for the NFW-like profile the beta - gamma relation is not a linear one (where gamma is the logarithmic derivative of the density rho[r]). The shape of beta(r) depends mostly on the ratio of the gravitational to kinetic energy within the NFW scale radius R_s. For the Sersic profile a linear beta - gamma relation is recovered, and in parti...

  20. RESOLVE and ECO: The Halo Mass-Dependent Shape of Galaxy Stellar and Baryonic Mass Functions

    CERN Document Server

    Eckert, Kathleen D; Stark, David V; Moffett, Amanda J; Berlind, Andreas A; Norris, Mark A

    2016-01-01

    In this work, we present galaxy stellar and baryonic (stars plus cold gas) mass functions (SMF and BMF) and their halo mass dependence for two volume-limited data sets. The first, RESOLVE-B, coincides with the Stripe 82 footprint and is extremely complete down to baryonic mass Mbary ~ 10^9.1 Msun, probing the gas-rich dwarf regime below Mbary ~ 10^10 Msun. The second, ECO, covers a ~40 times larger volume (containing RESOLVE-A) and is complete to Mbary ~ 10^9.4 Msun. To construct the SMF and BMF we implement a new "cross-bin sampling" technique with Monte Carlo sampling from the full likelihood distributions of stellar or baryonic mass. Our SMFs exhibit the "plateau" feature starting below Mstar ~ 10^10 Msun that has been described in prior work. However, the BMF fills in this feature and rises as a straight power law below ~10^10 Msun, as gas-dominated galaxies become the majority of the population. Nonetheless, the low-mass slope of the BMF is not as steep as that of the theoretical dark matter halo MF. Mor...

  1. Connecting Galaxies with Halos Across Cosmic Time: Stellar mass assembly distribution modeling of galaxy statistics

    CERN Document Server

    Becker, Matthew R

    2015-01-01

    In this work, I explore an empirically motivated model for investigating the relationship between galaxy stellar masses, star formation rates and their halo masses and mass accretion histories. The core statistical quantity in this model is the stellar mass assembly distribution, $P(dM_{*}/dt|\\mathbf{X},a)$, which specifies the probability density distribution of stellar mass assembly rates given a set of halo properties $\\mathbf{X}$ and epoch $a$. Predictions from this model are obtained by integrating the stellar mass assembly distribution (SMAD) over halo merger trees, easily obtained from modern, high-resolution $N$-body simulations. Further properties of the galaxies hosted by the halos can be obtained by post-processing the stellar mass assembly histories with stellar population synthesis models. In my particular example implementation of this model, I use the \\citet{behroozi13a} constraint on the median stellar mass assembly rates of halos as a function of their mass and redshift to construct an exampl...

  2. Constraining quasar host halo masses with the strength of nearby Lyman-alpha forest absorption

    CERN Document Server

    Kim, Y R; Kim, Young-Rae; Croft, Rupert

    2006-01-01

    Using cosmological hydrodynamic simulations we measure the mean transmitted flux in the Lyman alpha forest for quasar sightlines that pass near a foreground quasar. We find that the trend of absorption with pixel-quasar separation distance can be fitted using a simple power law form including the usual correlation function parameters r_{0} and \\gamma so that ( = \\sum exp(-tau_eff*(1+(r/r_{0})^(-\\gamma)))). From the simulations we find the relation between r_{0} and quasar mass and formulate this as a way to estimate quasar host dark matter halo masses, quantifying uncertainties due to cosmological and IGM parameters, and redshift errors. With this method, we examine data for ~3000 quasars from the Sloan Digital Sky Survey (SDSS) Data Release 3, assuming that the effect of ionizing radiation from quasars (the so-called transverse proximity effect) is unimportant (no evidence for it is seen in the data.) We find that the best fit host halo mass for SDSS quasars with mean redshift z=3 and absolute G band magnitu...

  3. Dark-matter haloes and the M-σ relation for supermassive black holes

    Science.gov (United States)

    Larkin, Adam C.; McLaughlin, Dean E.

    2016-10-01

    We develop models of two-component spherical galaxies to establish scaling relations linking the properties of spheroids at z = 0 (total stellar masses, effective radii Re and velocity dispersions within Re) to the properties of their dark-matter haloes at both z = 0 and higher redshifts. Our main motivation is the widely accepted idea that the accretion-driven growth of supermassive black holes (SMBHs) in protogalaxies is limited by quasar-mode feedback and gas blow-out. The SMBH masses, MBH, should then be connected to the dark-matter potential wells at the redshift zqso of the blow-out. We specifically consider the example of a power-law dependence on the maximum circular speed in a protogalactic dark-matter halo: M_{BH}∝ V^4_{d,pk}, as could be expected if quasar-mode feedback were momentum-driven. For haloes with a given Vd,pk at a given zqso ≥ 0, our model scaling relations give a typical stellar velocity dispersion σap(Re) at z = 0. Thus, they transform a theoretical MBH-Vd,pk relation into a prediction for an observable MBH-σap(Re) relation. We find the latter to be distinctly non-linear in log-log space. Its shape depends on the generic redshift evolution of haloes in a Λ cold dark matter cosmology and the systematic variation of stellar-to-dark matter mass fraction at z = 0, in addition to any assumptions about the physics underlying the MBH-Vd,pk relation. Despite some clear limitations of the form we use for MBH versus Vd,pk, and even though we do not include any SMBH growth through dry mergers at low redshift, our results for MBH-σap(Re) compare well to data for local early types if we take zqso ˜ 2-4.

  4. ARE HALO-LIKE SOLAR CORONAL MASS EJECTIONS MERELY A MATTER OF GEOMETRIC PROJECTION EFFECTS?

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Ryun-Young; Zhang, Jie [School of Physics, Astronomy and Computational Sciences, George Mason University, 4400 University Drive, MSN 6A2, Fairfax, VA 22030, USA. (United States); Vourlidas, Angelos, E-mail: ryunyoung.kwon@gmail.com [The Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723, USA. (United States)

    2015-02-01

    We investigated the physical nature of halo coronal mass ejections (CMEs) based on the stereoscopic observations from the two STEREO spacecraft, Ahead and Behind (hereafter A and B), and the SOHO spacecraft. Sixty-two halo CMEs occurred as observed by SOHO LASCO C2 for the three-year period from 2010 to 2012 during which the separation angles between SOHO and STEREO were nearly 90°. In such quadrature configuration, the coronagraphs of STEREO, COR2-A and -B, showed the side view of those halo CMEs seen by C2. It has been widely believed that the halo appearance of a CME is caused by the geometric projection effect, i.e., a CME moves along the Sun-observer line. In other words, it would appear as a non-halo CME if viewed from the side. However, to our surprise, we found that 41 out of 62 events (66%) were observed as halo CMEs by all coronagraphs. This result suggests that a halo CME is not just a matter of the propagating direction. In addition, we show that a CME propagating normal to the line of sight can be observed as a halo CME due to the associated fast magnetosonic wave or shock front. We conclude that the apparent width of CMEs, especially halos or partial halos is driven by the existence and the extent of the associated waves or shocks and does not represent an accurate measure of the CME ejecta size. This effect needs to be taken into careful consideration in space weather predictions and modeling efforts.

  5. The impact of the dusty torus on obscured quasar halo mass measurements

    Science.gov (United States)

    DiPompeo, M. A.; Runnoe, J. C.; Hickox, R. C.; Myers, A. D.; Geach, J. E.

    2016-07-01

    Recent studies have found that obscured quasars cluster more strongly and are thus hosted by dark matter haloes of larger mass than their unobscured counterparts. These results pose a challenge for the simplest unification models, in which obscured objects are intrinsically the same as unobscured sources but seen through a dusty line of sight. There is general consensus that a structure like a `dusty torus' exists, meaning that this intrinsic similarity is likely the case for at least some subset of obscured quasars. However, the larger host halo masses of obscured quasars imply that there is a second obscured population that has an even higher clustering amplitude and typical halo mass. Here, we use simple assumptions about the host halo mass distributions of quasars, along with analytical methods and cosmological N-body simulations to isolate the signal from this population. We provide values for the bias and halo mass as a function of the fraction of the `non-torus-obscured' population. Adopting a reasonable value for this fraction of ˜25 per cent implies a non-torus-obscured-quasar bias that is much higher than the observed obscured quasar bias, because a large fraction of the obscured population shares the same clustering strength as the unobscured objects. For this non-torus-obscured population, we derive a bias of ˜3, and typical halo masses of ˜3 × 1013 M⊙ h-1 at z = 1. These massive haloes are likely the descendants of high-mass unobscured quasars at high redshift, and will evolve into members of galaxy groups at z = 0.

  6. THE EATING HABITS OF MILKY WAY-MASS HALOS: DESTROYED DWARF SATELLITES AND THE METALLICITY DISTRIBUTION OF ACCRETED STARS

    Energy Technology Data Exchange (ETDEWEB)

    Deason, Alis J.; Mao, Yao-Yuan; Wechsler, Risa H., E-mail: adeason@stanford.edu [Kavli Institute for Particle Astrophysics and Cosmology and Physics Department, Stanford University, Stanford, CA 94305 (United States)

    2016-04-10

    We study the mass spectrum of destroyed dwarfs that contribute to the accreted stellar mass of Milky Way (MW)-mass (M{sub vir} ∼ 10{sup 12.1} M{sub ⊙}) halos using a suite of 45 zoom-in dissipationless simulations. Empirical models are employed to relate (peak) subhalo mass to dwarf stellar mass, and we use constraints from z = 0 observations and hydrodynamical simulations to estimate the metallicity distribution of the accreted stellar material. The dominant contributors to the accreted stellar mass are relatively massive dwarfs with M{sub star} ∼ 10{sup 8}–10{sup 10}M{sub ⊙}. Halos with more quiescent accretion histories tend to have lower mass progenitors (10{sup 8}–10{sup 9} M{sub ⊙}), and lower overall accreted stellar masses. Ultra-faint mass (M{sub star} < 10{sup 5} M{sub ⊙}) dwarfs contribute a negligible amount (≪1%) to the accreted stellar mass and, despite having low average metallicities, supply a small fraction (∼2%–5%) of the very metal-poor stars with [Fe/H] < −2. Dwarfs with masses 10{sup 5} < M{sub star}/M{sub ⊙} < 10{sup 8} provide a substantial amount of the very metal-poor stellar material (∼40%–80%), and even relatively metal-rich dwarfs with M{sub star} > 10{sup 8} M{sub ⊙} can contribute a considerable fraction (∼20%–60%) of metal-poor stars if their metallicity distributions have significant metal-poor tails. Finally, we find that the generic assumption of a quiescent assembly history for the MW halo seems to be in tension with the mass spectrum of its surviving dwarfs. We suggest that the MW could be a “transient fossil”; a quiescent halo with a recent accretion event(s) that disguises the preceding formation history of the halo.

  7. The Impact of the Dusty Torus on Obscured Quasar Halo Mass Measurements

    CERN Document Server

    DiPompeo, Michael A; Hickox, Ryan C; Myers, Adam D; Geach, James E

    2016-01-01

    Recent studies have found that obscured quasars cluster more strongly and are thus hosted by dark matter haloes of larger mass than their unobscured counterparts. These results pose a challenge for the simplest unification models, in which obscured objects are intrinsically the same as unobscured sources but seen through a dusty line of sight. There is general consensus that a structure like a "dusty torus" exists, meaning that this intrinsic similarity is likely the case for at least some subset of obscured quasars. However, the larger host halo masses of obscured quasars implies that there is a second obscured population that has an even higher clustering amplitude and typical halo mass. Here, we use simple assumptions about the host halo mass distributions of quasars, along with analytical methods and cosmological $N$-body simulations to isolate the signal from this population. We provide values for the bias and halo mass as a function of the fraction of the "non-torus obscured" population. Adopting a reas...

  8. Density Profiles of Dark Halos from their Mass Accretion Histories

    Directory of Open Access Journals (Sweden)

    M. A. Alvarez

    2003-01-01

    Full Text Available Utilizando la historia universal de acrecion de masa derivada de simulaciones de formacion de halos en el modelo de materia oscura fria (CDM analizamos la formacion y crecimiento de un halo individual. Derivamos el pefil de densidad utilizando tres aproximaciones de menor grado sucesivamente: equilibrio, orbitas radiales, y una aproximacion de fluido. En el modelo de equilibrio, el pefil de densidad se ajusta bien por un pefil de NFW o por un pefil de Moore sobre un rango limitado de radios y factores de escala. En el modelo de orbitas radiales encontramos un pefil mas empinado que el de NFW, con una pendiente logaritmica en la parte interior cercana a -2, consistente con un sistema no colisional puramente radial. En la proximacion de fluido encontramos concordancia con los pefiles de Moore y NFW para radios resueltos por las simulaciones de N-cuerpos (r/r200 > 0.01 y una evolucion de los parametros de concentracion casi identica a la que se encuentra en dichas simulaciones. Por lo tanto, la evolucion de la estructura de halos cosmologicos se entiende mejor como un efecto de la tasa de acrecion variante en el tiempo sobre un fuido no colisional, isotropico y de distribucion suave.

  9. Halo mass dependence of H I and O VI absorption: evidence for differential kinematics

    Energy Technology Data Exchange (ETDEWEB)

    Mathes, Nigel L.; Churchill, Christopher W.; Nielsen, Nikole M.; Trujillo-Gomez, Sebastian [New Mexico State University, Las Cruces, NM 88003 (United States); Kacprzak, Glenn G. [Swinburne University of Technology, Victoria 3122 (Australia); Charlton, Jane; Muzahid, Sowgat [The Pennsylvania State University, University Park, PA 16802 (United States)

    2014-09-10

    We studied a sample of 14 galaxies (0.1 < z < 0.7) using HST/WFPC2 imaging and high-resolution HST/COS or HST/STIS quasar spectroscopy of Lyα, Lyβ, and O VI λλ1031, 1037 absorption. The galaxies, having 10.8 ≤ log (M {sub h}/M {sub ☉}) ≤ 12.2, lie within D = 300 kpc of quasar sightlines, probing out to D/R {sub vir} = 3. When the full range of M {sub h} and D/R {sub vir} of the sample are examined, ∼40% of the H I absorbing clouds can be inferred to be escaping their host halo. The fraction of bound clouds decreases as D/R {sub vir} increases such that the escaping fraction is ∼15% for D/R {sub vir} < 1, ∼45% for 1 ≤ D/R {sub vir} < 2, and ∼90% for 2 ≤ D/R {sub vir} < 3. Adopting the median mass log M {sub h}/M {sub ☉} = 11.5 to divide the sample into 'higher' and 'lower' mass galaxies, we find a mass dependency for the hot circumgalactic medium kinematics. To our survey limits, O VI absorption is found in only ∼40% of the H I clouds in and around lower mass halos as compared to ∼85% around higher mass halos. For D/R {sub vir} < 1, lower mass halos have an escape fraction of ∼65%, whereas higher mass halos have an escape fraction of ∼5%. For 1 ≤ D/R {sub vir} < 2, the escape fractions are ∼55% and ∼35% for lower mass and higher mass halos, respectively. For 2 ≤ D/R {sub vir} < 3, the escape fraction for lower mass halos is ∼90%. We show that it is highly likely that the absorbing clouds reside within 4R {sub vir} of their host galaxies and that the kinematics are dominated by outflows. Our finding of 'differential kinematics' is consistent with the scenario of 'differential wind recycling' proposed by Oppenheimer et al. We discuss the implications for galaxy evolution, the stellar to halo mass function, and the mass-metallicity relationship of galaxies.

  10. Toward a halo mass function for precision cosmology: the limits of universality

    CERN Document Server

    Tinker, Jeremy L; Klypin, Anatoly; Abazajian, Kevork; Warren, Michael S; Yepes, Gustavo; Gottlober, Stefan; Holz, Daniel E

    2008-01-01

    We measure the mass function of dark matter halos in a large set of collisionless cosmological simulations of flat LCDM cosmology and investigate its evolution at z<~2. Halos are identified as isolated density peaks, and their masses are measured within a series of radii enclosing specific overdensities. We argue that these spherical overdensity masses are more directly linked to cluster observables than masses measured using the friends-of-friends algorithm (FOF), and are therefore preferable for accurate forecasts of halo abundances. Our simulation set allows us to calibrate the mass function at z=0 for virial masses in the range 10^{11} Msol/h < M < 10^{15} Msol/h, to <~ 5%. We derive fitting functions for the halo mass function in this mass range for a wide range of overdensities, both at z=0 and earlier epochs. In addition to these formulae, which improve on previous approximations by 10-20%, our main finding is that the mass function cannot be represented by a universal fitting function at t...

  11. Sub-millimetre galaxies reside in dark matter halos with masses greater than 3x10^11 solar masses

    CERN Document Server

    Amblard, Alexandre; Serra, Paolo; Altieri, B; Arumugam, V; Aussel, H; Blain, A; Bock, J; Boselli, A; Buat, V; Castro-Rodriguez, N; Cava, A; Chanial, P; Chapin, E; Clements, D L; Conley, A; Conversi, L; Dowell, C D; Dwek, E; Eales, S; Elbaz, D; Farrah, D; Franceschini, A; Gear, W; Glenn, J; Griffin, M; Halpern, M; Hatziminaoglou, E; Ibar, E; Isaak, K; Ivison, R J; Khostovan, A A; Lagache, G; Levenson, L; Lu, N; Madden, S; Maffei, B; Mainetti, G; Marchetti, L; Marsden, G; Mitchell-Wynne, K; Nguyen, H T; O'Halloran, B; Oliver, S J; Omont, A; Page, M J; Panuzzo, P; Papageorgiou, A; Pearson, C P; Perez-Fournon, I; Pohlen, M; Rangwala, N; Roseboom, I G; Rowan-Robinson, M; Portal, M Sanchez; Schulz, B; Scott, Douglas; Seymour, N; Shupe, D L; Smith, A J; Stevens, J A; Symeonidis, M; Trichas, M; Tugwell, K; Vaccari, M; Valiante, E; Valtchanov, I; Vieira, J D; Vigroux, L; Wang, L; Ward, R; Wright, G; Xu, C K; Zemcov, M

    2011-01-01

    The extragalactic background light at far-infrared wavelengths originates from optically-faint, dusty, star-forming galaxies in the universe with star-formation rates at the level of a few hundred solar masses per year. Due to the relatively poor spatial resolution of far-infrared telescopes, the faint sub-millimetre galaxies are challenging to study individually. Instead, their average properties can be studied using statistics such as the angular power spectrum of the background intensity variations. A previous attempt at measuring this power spectrum resulted in the suggestion that the clustering amplitude is below the level computed with a simple ansatz based on a halo model. Here we report a clear detection of the excess clustering over the linear prediction at arcminute angular scales in the power spectrum of brightness fluctuations at 250, 350, and 500 microns. From this excess, we find that sub-millimetre galaxies are located in dark matter halos with a minimum mass of log[M_min/M_sun ]= 11.5^+0.7_-0....

  12. Understanding the Core-Halo Relation of Quantum Wave Dark Matter, $\\psi$DM, from 3D Simulations

    CERN Document Server

    Schive, Hsi-Yu; Woo, Tak-Pong; Wong, Shing-Kwong; Chiueh, Tzihong; Broadhurst, Tom; Hwang, W-Y Pauchy

    2014-01-01

    We examine the nonlinear structure of gravitationally collapsed objects that form in our simulations of wavelike cold dark matter ($\\psi$DM), described by the Schr\\"odinger-Poisson (SP) equation. A distinct gravitationally self-bound solitonic core is found at the center of every halo, with a profile quite different from cores modeled in the warm or self-interacting dark matter scenarios. Furthermore, we show that each solitonic core is surrounded by an extended halo composed of large fluctuating dark matter granules which modulate the halo density on a scale comparable to the diameter of the solitonic core. The scaling symmetry of the SP equation and the uncertainty principle tightly relate the core mass to the halo specific energy, which, in the context of cosmological structure formation, leads to a simple scaling between core mass ($M_c$) and halo mass ($M_h$), $M_c \\propto a^{-1/2} M_h^{1/3}$, where $a$ is the cosmic scale factor. We verify this scaling relation by (i) examining the internal structure of...

  13. Using Dark Matter Haloes to Learn about Cosmic Acceleration: A New Proposal for a Universal Mass Function

    Science.gov (United States)

    Prescod-Weinstein, Chanda; Afshordi, Niayesh

    2011-01-01

    Structure formation provides a strong test of any cosmic acceleration model because a successful dark energy model must not inhibit or overpredict the development of observed large-scale structures. Traditional approaches to studies of structure formation in the presence of dark energy or a modified gravity implement a modified Press-Schechter formalism, which relates the linear overdensities to the abundance of dark matter haloes at the same time. We critically examine the universality of the Press-Schechter formalism for different cosmologies, and show that the halo abundance is best correlated with spherical linear overdensity at 94% of collapse (or observation) time. We then extend this argument to ellipsoidal collapse (which decreases the fractional time of best correlation for small haloes), and show that our results agree with deviations from modified Press-Schechter formalism seen in simulated mass functions. This provides a novel universal prescription to measure linear density evolution, based on current and future observations of cluster (or dark matter) halo mass function. In particular, even observations of cluster abundance in a single epoch will constrain the entire history of linear growth of cosmological of perturbations.

  14. Stochastic Star Formation & Feedback: Mapping Low-Mass Galaxies to Dark Matter Haloes

    CERN Document Server

    Power, Chris; Robotham, Aaron S G; Lewis, Geraint F; Wilkinson, Mark I

    2014-01-01

    Comparison of observed satellite galaxies of the Milky Way (hereafter MW) with dark matter subhaloes in cosmological $N$-body simulations of MW-mass haloes suggest that such subhaloes, if they exist, are occupied by satellites in a stochastic fashion. We examine how inefficient massive star formation and associated supernova feedback in high-redshift progenitors of present-day low-mass subhaloes might contribute to this stochasticity. Using a Monte Carlo approach to follow the assembly histories of present-day low-mass haloes with $10^7 \\lesssim M \\leq 10^{10}$ ${\\rm M}_{\\odot}$, we identify when cooling and star formation is likely to proceed, and observe that haloes with present-day masses $\\lesssim 10^9 {\\rm M}_{\\odot}$ never grow sufficiently massive to support atomic hydrogen line cooling. Noting that the star formation timescale decreases sharply with stellar mass as $t_{\\rm PMS} \\propto m_{\\ast}^{-2.5}$, we argue that, should the conditions for high mass star formation arise in low-mass haloes, the ens...

  15. A Population of Relic Intermediate-Mass Black Holes in the Halo of the Milky Way

    CERN Document Server

    Rashkov, Valery

    2013-01-01

    If "seed" central black holes were common in the subgalactic building blocks that merged to form present-day massive galaxies, then relic intermediate-mass black holes (IMBHs) should be present in the Galactic bulge and halo. We use a particle tagging technique to dynamically populate the N-body Via Lactea II high-resolution simulation with black holes, and assess the size, properties, and detectability of the leftover population. The method assigns a black hole to the most tightly bound central particle of each subhalo at infall according to an extrapolation of the M_BH-sigma_* relation, and self-consistently follows the accretion and disruption of Milky Way progenitor dwarfs and their holes in a cosmological "live" host from high redshift to today. We show that, depending on the minimum stellar velocity dispersion, sigma_m, below which central black holes are assumed to be increasingly rare, as many as ~2000 (sigma_m=3 km/s) or as few as ~70 (sigma_m=12 km/s) IMBHs may be left wandering in the halo of the M...

  16. A Stellar Feedback Origin for Neutral Hydrogen in High-Redshift Quasar-Mass Halos

    CERN Document Server

    Faucher-Giguere, C -A; Quataert, E; Keres, D; Hopkins, P F; Murray, N

    2016-01-01

    Observations of quasar pairs reveal that quasar host halos at z~2 have large covering fractions of cool dense gas (>~60% for Lyman limit systems within a projected virial radius). Most simulations have so far failed to explain these large observed covering fractions. We analyze a new set of 15 simulated massive halos with explicit stellar feedback from the FIRE project, covering the halo mass range M_h~2x10^12-10^13 Msun at z=2. This extends our previous analysis of the circum-galactic medium of high-redshift galaxies to more massive halos. Feedback from active galactic nuclei (AGN) is not included in these simulations. We find covering fractions consistent with those observed around z~2 quasars. The large HI covering fractions arise from star formation-driven galactic winds, including winds from low-mass satellite galaxies that interact with the cosmological infalling filaments in which they are typically embedded. The simulated covering fractions increase with both halo mass and redshift over the ranges cov...

  17. Diverse Stellar Haloes in Nearby Milky Way-Mass Disc Galaxies

    CERN Document Server

    Harmsen, Benjamin; Bell, Eric F; de Jong, Roelof S; Bailin, Jeremy; Radburn-Smith, David J; Holwerda, Benne W

    2016-01-01

    We have examined the resolved stellar populations at large galactocentric distances along the minor axis (from 10 kpc up to between 40 and 75 kpc), with limited major axis coverage, of six nearby highly-inclined Milky Way-mass disc galaxies using HST data from the GHOSTS survey. We select red giant branch stars to derive stellar halo density profiles. The projected minor axis density profiles can be approximated by power laws with projected slopes of between $-2$ and $-3.7$ and a diversity of stellar halo masses of $1-6\\times 10^{9}M_{\\odot}$, or $2-14\\%$ of the total galaxy stellar masses. The typical intrinsic scatter around a smooth power law fit is $0.05-0.1$ dex owing to substructure. By comparing the minor and major axis profiles, we infer projected axis ratios $c/a$ at $\\sim 25$ kpc between $0.4-0.75$. The GHOSTS stellar haloes are diverse, lying between the extremes charted out by the (rather atypical) haloes of the Milky Way and M31. We find a strong correlation between the stellar halo metallicities...

  18. The Effect of Halo Mass on the HI Content of Galaxies in Groups and Clusters

    CERN Document Server

    Yoon, Ilsang

    2015-01-01

    We combine data from the Sloan Digital Sky Survey (SDSS) and the Arecibo Legacy Fast ALFA Survey (ALFALFA) to study the cold atomic gas content of galaxies in groups and clusters in local universe. A careful cross-matching of galaxies in the SDSS, ALFALFA and SDSS group catalogs provides a sample of group galaxies with stellar masses $10^{8.4} M_{\\odot} \\le M_{*} \\le 10^{10.6} M_{\\odot}$ and group halo masses $10^{12.5} h^{-1} M_{\\odot} \\le M_h \\le 10^{15.0} h^{-1} M_{\\odot}$. Controlling our sample in stellar mass and redshift, we find no significant radial variation in the galaxy \\hi\\ gas-to-stellar mass ratio for the halo mass range in our sample. However, the fraction of galaxies detected in ALFALFA declines steadily towards the centers of groups with the effect being most prominent in the most massive halos. In the outskirts of massive halos a hint of a depressed detection fraction for low mass galaxies suggests pre-processing that decreases the \\hi\\ in these galaxies before they fall into massive cluste...

  19. Simulations of galaxies formed in warm dark matter halos of masses at the filtering scale

    CERN Document Server

    Colin, Pedro; Gonzalez-Samaniego, Alejandro; Velazquez, Hector

    2014-01-01

    We present zoom-in N-body + Hydrodynamic simulations of dwarf central galaxies formed in Warm Dark Matter (WDM) halos with masses at present-day of $2-4\\times 10^{10}$ \\msun. Two different cases are considered, the first one when halo masses are close to the corresponding half-mode filtering scale \\Mhm\\ (\\mwdm =1.2 keV), and the second when they are 20 to 30 times the corresponding \\Mhm\\ (\\mwdm = 3.0 keV). The WDM simulations are compared with the respective Cold Dark Matter (CDM) simulations. The dwarfs formed in halos of masses (20-30)\\Mhm have roughly similar properties and evolution than their CDM counterparts; on the contrary, those formed in halos of masses around \\Mhm, are systematically different from their CDM counterparts. As compared to the CDM dwarfs, they assemble the dark and stellar masses later, having mass-weighted stellar ages 1.4--4.8 Gyr younger; their circular velocity profiles are shallower, with maximal velocities 20--60% lower; their stellar distributions are much less centrally concen...

  20. Milky Way Mass and Potential Recovery Using Tidal Streams in a Realistic Halo

    CERN Document Server

    Bonaca, Ana; Kuepper, Andreas H W; Diemand, Juerg; Johnston, Kathryn V; Hogg, David W

    2014-01-01

    We present a new method for determining the Galactic gravitational potential based on forward modeling of tidal stellar streams. We use this method to test the performance of smooth and static analytic potentials in representing realistic dark matter halos, which have substructure and are continually evolving by accretion. Our FAST-FORWARD method uses a Markov Chain Monte Carlo algorithm to compare, in 6D phase space, an "observed" stream to models created in trial analytic potentials. We analyze a large sample of streams evolved in the Via Lactea II (VL2) simulation, which represents a realistic Galactic halo potential. The recovered potential parameters are in agreement with the best fit to the global, present-day VL2 potential. However, merely assuming an analytic potential limits the dark matter halo mass measurement to an accuracy of 5 to 20%, depending on the choice of analytic parametrization. Collectively, mass estimates using streams from our sample reach this fundamental limit, but individually they...

  1. The masses and density profiles of halos in a LCDM galaxy formation simulation

    CERN Document Server

    Schaller, Matthieu; Bower, Richard G; Theuns, Tom; Jenkins, Adrian; Schaye, Joop; Crain, Robert A; Furlong, Michelle; Vecchia, Claudio Dalla; McCarthy, I G

    2014-01-01

    We investigate the internal structure and density profiles of halos of mass $10^{10}-10^{14}~M_\\odot$ in the Evolution and Assembly of Galaxies and their Environment (EAGLE) simulations. These follow the formation of galaxies in a $\\Lambda$CDM Universe and include a treatment of the baryon physics thought to be relevant. The EAGLE simulations reproduce the observed present-day galaxy stellar mass function, as well as many other properties of the galaxy population as a function of time. We find significant differences between the masses of halos in the EAGLE simulations and in simulations that follow only the dark matter component. Nevertheless, halos are well described by the Navarro-Frenk-White (NFW) density profile at radii larger than ~5% of the virial radius but, closer to the centre, the presence of stars can produce cuspier profiles. Central enhancements in the total mass profile are most important in halos of mass $10^{12}-10^{13}M_\\odot$, where the stellar fraction peaks. Over the radial range where t...

  2. Velocity and Mass Functions of Galactic Halos Evolution and Environmental Dependence

    CERN Document Server

    Sigad, Y; Bullock, J S; Kravtsov, A V; Klypin, A A; Primack, Joel R; Dekel, A; Sigad, Yair; Kolatt, Tsafrir S.; Bullock, James S.; Kravtsov, Andrey V.; Klypin, Anatoly A.; Primack, Joel R.; Dekel, Avishai

    2000-01-01

    We study the distribution functions of mass and circular velocity for dark matter halos in N-body simulations of the $\\Lambda$CDM cosmology, addressing redshift and environmental dependence. The dynamical range enables us to resolve subhalos and distinguish them from "distinct" halos. The mass function is compared to analytic models, and is used to derive the more observationally relevant circular velocity function. The distribution functions in the velocity range 100--500 km/s are well fit by a power-law with two parameters, slope and amplitude. We present the parameter dependence on redshift and provide useful fitting formulae. The amplitudes of the mass functions decrease with z, but, contrary to naive expectation, the comoving density of halos of a fixed velocity ~200 km/s actually increases out to z=5. This is because high-z halos are denser, so a fixed velocity corresponds to a smaller mass. The slope of the velocity function at z=0 is as steep as ~ -4, and the mass and velocity functions of distinct ha...

  3. Formation of In Situ Stellar Haloes in Milky Way-Mass Galaxies

    CERN Document Server

    Cooper, Andrew P; Lowing, Ben; Cole, Shaun; Frenk, Carlos

    2015-01-01

    We study the formation of stellar haloes in three Milky Way-mass galaxies using cosmological SPH simulations, focusing on the subset of halo stars that form in situ, as opposed to those accreted from satellites. In situ stars in our simulations dominate the stellar halo out to 20 kpc and account for 30 - 40 per cent of its total mass. We separate in situ halo stars into three straightforward, physically distinct categories according to their origin: stars scattered from the disc of the main galaxy ("heated disc"), stars formed from gas smoothly accreted onto the halo ("smooth"-gas) and stars formed in streams of gas stripped from infalling satellites ("stripped"-gas). We find that most belong to this latter category. Those originating in smooth gas outside the disc tend to form at the same time and place as the stripped-gas population, suggesting that their formation is associated with the same gas-rich accretion events. The scattered disc star contribution is negligible overall but significant in the Solar n...

  4. Revisiting scaling relations for giant radio halos in galaxy clusters

    CERN Document Server

    Cassano, R; Brunetti, G; Giacintucci, S; Pratt, G W; Venturi, T; Kale, R; Dolag, K; Markevitch, M

    2013-01-01

    Many galaxy clusters host Megaparsec-scale radio halos, generated by ultrarelativistic electrons in the magnetized intracluster medium. Correlations between the power of radio halos and the thermal properties of the hosting clusters were established in the last decade, including the connection between the presence of a halo and cluster mergers. The X-ray luminosity and redshift limited Extended GMRT Radio Halo Survey provides a rich and unique dataset for statistical studies of the halos. We uniformly analyze the radio and X-ray data for the GMRT cluster sample, and use the new Planck SZ catalog, to revisit the correlations between the power of halos and the thermal properties of galaxy clusters. We find that the radio power of halos at 1.4 GHz scales with the cluster X-ray (0.1--2.4 keV) luminosity computed within R_500 as P_1.4 L_500^2.0. Our bigger and more homogenous sample confirms that the X-ray luminous (L_500 > 5x10^44 erg/s) clusters branch into two populations --- radio halos lie on the correlation,...

  5. Modification of the halo mass function by kurtosis associated with primordial non-Gaussianity

    NARCIS (Netherlands)

    Yokoyama, Shuichiro; Sugiyama, Naoshi; Zaroubi, Saleem; Silk, Joseph

    2011-01-01

    We study the halo mass function in the presence of a kurtosis type of primordial non-Gaussianity. The kurtosis corresponds to the trispectrum as defined in Fourier space. The primordial trispectrum is commonly characterized by two parameters, tNL and gNL. We focus on tNL which is an important

  6. Earth-mass haloes and the emergence of NFW density profiles

    CERN Document Server

    Angulo, Raul E; Ludlow, Aaron; Bonoli, Silvia

    2016-01-01

    We report results from simulations of neutralino dark matter ($\\chi$DM) haloes. We follow them from their emergence at one earth mass to a final mass of a few percent solar. We show that the density profiles of the first haloes are well described by a $\\sim r^{-1.5}$ power-law. As haloes grow in mass, their density profiles evolve significantly. In the central regions, they become shallower and reach on average $\\sim r^{-1}$, the asymptotic form of an NFW profile. However, the profile of individual haloes can show non-monotonic density slopes, and be shallower than $-1$ in some cases. We investigate the transformation of cuspy power-law profiles using a series of non-cosmological simulations of equal-mass mergers. Contrary to previous findings, we observe that temporal variations in the gravitational potential caused by mergers lead to a shallowing of the inner profile, an effect which is stronger for shallower initial profiles and for mergers that involve a higher number of systems. Depending on the merger d...

  7. Submillimetre galaxies reside in dark matter haloes with masses greater than 3 × 10(11) solar masses.

    Science.gov (United States)

    Amblard, Alexandre; Cooray, Asantha; Serra, Paolo; Altieri, B; Arumugam, V; Aussel, H; Blain, A; Bock, J; Boselli, A; Buat, V; Castro-Rodríguez, N; Cava, A; Chanial, P; Chapin, E; Clements, D L; Conley, A; Conversi, L; Dowell, C D; Dwek, E; Eales, S; Elbaz, D; Farrah, D; Franceschini, A; Gear, W; Glenn, J; Griffin, M; Halpern, M; Hatziminaoglou, E; Ibar, E; Isaak, K; Ivison, R J; Khostovan, A A; Lagache, G; Levenson, L; Lu, N; Madden, S; Maffei, B; Mainetti, G; Marchetti, L; Marsden, G; Mitchell-Wynne, K; Nguyen, H T; O'Halloran, B; Oliver, S J; Omont, A; Page, M J; Panuzzo, P; Papageorgiou, A; Pearson, C P; Pérez-Fournon, I; Pohlen, M; Rangwala, N; Roseboom, I G; Rowan-Robinson, M; Portal, M Sánchez; Schulz, B; Scott, Douglas; Seymour, N; Shupe, D L; Smith, A J; Stevens, J A; Symeonidis, M; Trichas, M; Tugwell, K; Vaccari, M; Valiante, E; Valtchanov, I; Vieira, J D; Vigroux, L; Wang, L; Ward, R; Wright, G; Xu, C K; Zemcov, M

    2011-02-24

    The extragalactic background light at far-infrared wavelengths comes from optically faint, dusty, star-forming galaxies in the Universe with star formation rates of a few hundred solar masses per year. These faint, submillimetre galaxies are challenging to study individually because of the relatively poor spatial resolution of far-infrared telescopes. Instead, their average properties can be studied using statistics such as the angular power spectrum of the background intensity variations. A previous attempt at measuring this power spectrum resulted in the suggestion that the clustering amplitude is below the level computed with a simple ansatz based on a halo model. Here we report excess clustering over the linear prediction at arcminute angular scales in the power spectrum of brightness fluctuations at 250, 350 and 500 μm. From this excess, we find that submillimetre galaxies are located in dark matter haloes with a minimum mass, M(min), such that log(10)[M(min)/M(⊙)] = 11.5(+0.7)(-0.2) at 350 μm, where M(⊙) is the solar mass. This minimum dark matter halo mass corresponds to the most efficient mass scale for star formation in the Universe, and is lower than that predicted by semi-analytical models for galaxy formation.

  8. On the shoulders of giants: properties of the stellar halo and the Milky Way mass distribution

    Energy Technology Data Exchange (ETDEWEB)

    Kafle, Prajwal Raj; Sharma, Sanjib; Lewis, Geraint F.; Bland-Hawthorn, Joss, E-mail: p.kafle@physics.usyd.edu.au [Sydney Institute for Astronomy, School of Physics A28, The University of Sydney, NSW 2006 (Australia)

    2014-10-10

    Halo stars orbit within the potential of the Milky Way, and hence their kinematics can be used to understand the underlying mass distribution. However, the inferred mass distribution depends sensitively on assumptions made on the density and the velocity anisotropy profiles of the tracer population. Also, there is a degeneracy between the parameters of the halo and those of the disk or bulge. Most previous attempts that use halo stars have made arbitrary assumptions about these. In this paper, we decompose the Galaxy into three major components—a bulge, a Miyamoto-Nagai disk, and a Navarro-Frenk-White dark matter halo - and then model the kinematic data of the halo blue horizontal branch and K-giant stars from the Sloan Extension for Galactic Understanding and Exploration. Additionally, we use the gas terminal velocity curve and the Sgr A* proper motion. With the distance of the Sun from the center of the Galaxy R {sub ☉} = 8.5 kpc, our kinematic analysis reveals that the density of the stellar halo has a break at 17.2{sub −1.0}{sup +1.1} kpc and an exponential cutoff in the outer parts starting at 97.7{sub −15.8}{sup +15.6} kpc. Also, we find that the tracer velocity anisotropy is radially biased with β {sub s} = 0.4 ± 0.2 in the outer halo. We measure halo virial mass M {sub vir} to be 0.80{sub −0.16}{sup +0.31}×10{sup 12} M{sub ⊙}, concentration c to be 21.1{sub −8.3}{sup +14.8}, disk mass to be 0.95{sub −0.30}{sup +0.24}×10{sup 11} M{sub ⊙}, disk scale length to be 4.9{sub −0.4}{sup +0.4} kpc, and bulge mass to be 0.91{sub −0.38}{sup +0.31}×10{sup 10} M{sub ⊙}. The halo mass is found to be small, and this has important consequences. The giant stars reveal that the outermost halo stars have low velocity dispersion, but interestingly this suggests a truncation of the stellar halo density rather than a small overall mass of the Galaxy. Our estimates of local escape velocity v{sub esc}=550.9{sub −22.1}{sup +32.4} km s{sup −1} and

  9. The early gaseous and stellar mass assembly of Milky Way-type galaxy halos

    Science.gov (United States)

    Hensler, Gerhard; Petrov, Mykola

    2016-08-01

    How the Milky Way has accumulated its mass over the Hubble time, whether significant amounts of gas and stars were accreted from satellite galaxies, or whether the Milky Way has experienced an initial gas assembly and then evolved more-or-less in isolation is one of the burning questions in modern astronomy, because it has consequences for our understanding of galaxy formation in the cosmological context. Here we present the evolutionary model of a Milky Way-type satellite system zoomed into a cosmological large-scale simulation. Embedded into Dark Matter halos and allowing for baryonic processes these chemo-dynamical simulations aim at studying the gas and stellar loss from the satellites to feed the Milky Way halo and the stellar chemical abundances in the halo and the satellite galaxies.

  10. The early gaseous and stellar mass assembly of Milky Way-type galaxy halos

    CERN Document Server

    Hensler, Gerhard

    2016-01-01

    How the Milky Way has accumulated its mass over the Hubble time, whether significant amounts of gas and stars were accreted from satellite galaxies, or whether the Milky Way has experienced an initial gas assembly and then evolved more-or-less in isolation is one of the burning questions in modern astronomy, because it has consequences for our understanding of galaxy formation in the cosmological context. Here we present the evolutionary model of a Milky Way-type satellite system zoomed into a cosmological large-scale simulation. Embedded into Dark Matter halos and allowing for baryonic processes these chemo-dynamical simulations aim at studying the gas and stellar loss from the satellites to feed the Milky Way halo and the stellar chemical abundances in the halo and the satellite galaxies.

  11. Halo Mass Dependence of HI and OVI Absorption: Evidence for Differential Kinematics

    CERN Document Server

    Mathes, Nigel L; Kacprzak, Glenn G; Nielsen, Nikole M; Trujillo-Gomez, Sebastian; Charlton, Jane; Muzahid, Sowgat

    2014-01-01

    We studied a sample of 14 galaxies (0.1 < z < 0.7) using HST/WFPC2 imaging and high-resolution HST/COS or HST/STIS quasar spectroscopy of Lya, Lyb, OVI1031, and OVI1037 absorption. The galaxies, having 10.8 < log(M/M_solar) < 12.2, lie within D = 300 kpc of quasar sightlines, probing out to D/R_vir = 3. When the full range of galaxy virial masses and D/R_vir of the sample are examined, 40% of the HI absorbing clouds can be inferred to be escaping their host halo. The fraction of bound clouds decreases as D/R_vir increases such that the escaping fraction is around 15% for D/R_vir < 1, around 45% for 1 < D/R_vir < 2, and around 90% for 2 < D/R_vir < 3. Adopting the median mass log(M/M_solar) = 11.5 to divide the sample into "higher" and "lower" mass galaxies, we find mass dependency for the hot CGM kinematics. To our survey limits, OVI absorption is found in only 40% of the HI clouds in and around lower mass halos as compared to 85% around higher mass halos. For D/R < 1, lower mass...

  12. The minimum halo mass for star formation at z = 6-8

    Science.gov (United States)

    Finlator, Kristian; Prescott, Moire K. M.; Oppenheimer, B. D.; Davé, Romeel; Zackrisson, E.; Livermore, R. C.; Finkelstein, S. L.; Thompson, Robert; Huang, Shuiyao

    2017-01-01

    Recent analysis of strongly lensed sources in the Hubble Frontier Fields indicates that the rest-frame UV luminosity function of galaxies at z = 6-8 rises as a power law down to MUV = -15, and possibly as faint as -12.5. We use predictions from a cosmological radiation hydrodynamic simulation to map these luminosities on to physical space, constraining the minimum dark matter halo mass and stellar mass that the Frontier Fields probe. While previously published theoretical studies have suggested or assumed that early star formation was suppressed in haloes less massive than 109-1011 M⊙, we find that recent observations demand vigorous star formation in haloes at least as massive as (3.1, 5.6, 10.5) × 109 M⊙ at z = (6, 7, 8). Likewise, we find that Frontier Fields observations probe down to stellar masses of (8.1, 18, 32) × 106 M⊙: that is, they are observing the likely progenitors of analogues to Local Group dwarfs such as Pegasus and M32. Our simulations yield somewhat different constraints than two complementary models that have been invoked in similar analyses, emphasizing the need for further observational constraints on the galaxy-halo connection.

  13. Dependence of the outer density profiles of halos on their mass accretion rate

    Energy Technology Data Exchange (ETDEWEB)

    Diemer, Benedikt; Kravtsov, Andrey V., E-mail: bdiemer@oddjob.uchicago.edu [Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637 (United States)

    2014-07-01

    We present a systematic study of the density profiles of ΛCDM halos, focusing on the outer regions, 0.1 < r/R {sub vir} < 9. We show that the median and mean profiles of halo samples of a given peak height exhibit significant deviations from the universal analytic profiles discussed previously in the literature, such as the Navarro-Frenk-White and Einasto profiles, at radii r ≳ 0.5R {sub 200m}. In particular, at these radii the logarithmic slope of the median density profiles of massive or rapidly accreting halos steepens more sharply than predicted. The steepest slope of the profiles occurs at r ≈ R {sub 200m}, and its absolute value increases with increasing peak height or mass accretion rate, reaching slopes of –4 and steeper. Importantly, we find that the outermost density profiles at r ≳ R {sub 200m} are remarkably self-similar when radii are rescaled by R {sub 200m}. This self-similarity indicates that radii defined with respect to the mean density are preferred for describing the structure and evolution of the outer profiles. However, the inner density profiles are most self-similar when radii are rescaled by R {sub 200c}. We propose a new fitting formula that describes the median and mean profiles of halo samples selected by their peak height or mass accretion rate with accuracy ≲ 10% at all radii, redshifts, and masses we studied, r ≲ 9R {sub vir}, 0 < z < 6, and M {sub vir} > 1.7 × 10{sup 10} h {sup –1} M {sub ☉}. We discuss observational signatures of the profile features described above and show that the steepening of the outer profile should be detectable in future weak-lensing analyses of massive clusters. Such observations could be used to estimate the mass accretion rate of cluster halos.

  14. Revisiting Scaling Relations for Giant Radio Halos in Galaxy Clusters

    Science.gov (United States)

    Cassano, R.; Ettori, S.; Brunetti, G.; Giacintucci, S.; Pratt, G. W.; Venturi, T.; Kale, R.; Dolag, K.; Markevitch, Maxim L.

    2013-01-01

    Many galaxy clusters host megaparsec-scale radio halos, generated by ultrarelativistic electrons in the magnetized intracluster medium. Correlations between the synchrotron power of radio halos and the thermal properties of the hosting clusters were established in the last decade, including the connection between the presence of a halo and cluster mergers. The X-ray luminosity and redshift-limited Extended GMRT Radio Halo Survey provides a rich and unique dataset for statistical studies of the halos. We uniformly analyze the radio and X-ray data for the GMRT cluster sample, and use the new Planck Sunyaev-Zel'dovich (SZ) catalog to revisit the correlations between the power of radio halos and the thermal properties of galaxy clusters. We find that the radio power at 1.4 GHz scales with the cluster X-ray (0.1-2.4 keV) luminosity computed within R(sub 500) as P(sub 1.4) approx. L(2.1+/-0.2) - 500). Our bigger and more homogenous sample confirms that the X-ray luminous (L(sub 500) > 5 × 10(exp 44) erg/s)) clusters branch into two populations-radio halos lie on the correlation, while clusters without radio halos have their radio upper limits well below that correlation. This bimodality remains if we excise cool cores from the X-ray luminosities. We also find that P(sub 1.4) scales with the cluster integrated SZ signal within R(sub 500), measured by Planck, as P(sub 1.4) approx. Y(2.05+/-0.28) - 500), in line with previous findings. However, contrary to previous studies that were limited by incompleteness and small sample size, we find that "SZ-luminous" Y(sub 500) > 6×10(exp -5) Mpc(exp 2) clusters show a bimodal behavior for the presence of radio halos, similar to that in the radio-X-ray diagram. Bimodality of both correlations can be traced to clusters dynamics, with radio halos found exclusively in merging clusters. These results confirm the key role of mergers for the origin of giant radio halos, suggesting that they trigger the relativistic particle acceleration.

  15. The characteristic halo masses of half-a-million WISE-selected quasars

    Science.gov (United States)

    DiPompeo, M. A.; Hickox, R. C.; Eftekharzadeh, S.; Myers, A. D.

    2017-08-01

    Recent work has found evidence for a difference in the bias and dark matter halo masses of WISE (Wide-field Infrared Survey Explorer)-selected obscured and unobscured quasars, implying a distinction between these populations beyond random line-of-sight effects. However, the significance of this difference in the most up-to-date measurements is relatively weak, at ˜2σ for individual measurements, but bolstered by agreement from different techniques, including angular clustering and cross-correlations with cosmic microwave background lensing maps. Here, we expand the footprint of previous work, aiming to improve the precision of both methods. In this larger area, we correct for position-dependent selection effects, in particular fluctuations of the WISE-selected quasar density as a function of Galactic latitude. We also measure the cross-correlation of the obscured and unobscured samples and confirm that they are well matched in redshift, both centred at z = 1. Combined with very similar detection fractions and magnitude distributions in the long-wavelength WISE bands, this redshift match strongly supports the fact that infrared selection identifies obscured and unobscured quasars of similar bolometric luminosity. Finally, we perform cross-correlations with confirmed spectroscopic quasars, again confirming the results from other methods - obscured quasars reside in haloes a factor of 3 times more massive than unobscured quasars. This difference is significant at the ˜5σ level when the measurements are combined, providing strong support for the idea that obscuration in at least some quasars is tied to the larger environment, and may have an evolutionary component.

  16. THE CLUSTERING AND HALO MASSES OF STAR-FORMING GALAXIES AT z < 1

    Energy Technology Data Exchange (ETDEWEB)

    Dolley, Tim; Brown, Michael J. I.; Pimbblet, Kevin A.; Palamara, David P.; Beare, Richard [School of Physics and Astronomy, Monash University, Clayton, Victoria 3800 (Australia); Weiner, Benjamin J.; Jannuzi, Buell T. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Brodwin, Mark [Department of Physics and Astronomy, University of Missouri, Kansas City, MO 64110 (United States); Kochanek, C. S. [Department of Astronomy, The Ohio State University, Columbus, OH 43210 (United States); Dey, Arjun; Atlee, David W., E-mail: Tim.Dolley@monash.edu [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States)

    2014-12-20

    We present clustering measurements and halo masses of star-forming galaxies at 0.2 < z < 1.0. After excluding active galactic nuclei (AGNs), we construct a sample of 22,553 24 μm sources selected from 8.42 deg{sup 2} of the Spitzer MIPS AGN and Galaxy Evolution Survey of Boötes. Mid-infrared imaging allows us to observe galaxies with the highest star formation rates (SFRs), less biased by dust obscuration afflicting the optical bands. We find that the galaxies with the highest SFRs have optical colors that are redder than typical blue cloud galaxies, with many residing within the green valley. At z > 0.4 our sample is dominated by luminous infrared galaxies (LIRGs, L {sub TIR} > 10{sup 11} L {sub ☉}) and is composed entirely of LIRGs and ultraluminous infrared galaxies (ULIRGs, L {sub TIR} > 10{sup 12} L {sub ☉}) at z > 0.6. We observe weak clustering of r {sub 0} ≈ 3-6 h {sup –1} Mpc for almost all of our star-forming samples. We find that the clustering and halo mass depend on L {sub TIR} at all redshifts, where galaxies with higher L {sub TIR} (hence higher SFRs) have stronger clustering. Galaxies with the highest SFRs at each redshift typically reside within dark matter halos of M {sub halo} ≈ 10{sup 12.9} h {sup –1} M {sub ☉}. This is consistent with a transitional halo mass, above which star formation is largely truncated, although we cannot exclude that ULIRGs reside within higher mass halos. By modeling the clustering evolution of halos, we connect our star-forming galaxy samples to their local descendants. Most star-forming galaxies at z < 1.0 are the progenitors of L ≲ 2.5 L {sub *} blue galaxies in the local universe, but star-forming galaxies with the highest SFRs (L {sub TIR} ≳ 10{sup 11.7} L {sub ☉}) at 0.6 < z < 1.0 are the progenitors of early-type galaxies in denser group environments.

  17. Milky Way mass and potential recovery using tidal streams in a realistic halo

    Energy Technology Data Exchange (ETDEWEB)

    Bonaca, Ana; Geha, Marla [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Küpper, Andreas H. W.; Johnston, Kathryn V. [Department of Astronomy, Columbia University, New York, NY 027 (United States); Diemand, Jürg [Institute for Computational Sciences, University of Zürich, 8057 Zurich (Switzerland); Hogg, David W., E-mail: ana.bonaca@yale.edu [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place # 424, New York, NY 10003 (United States)

    2014-11-01

    We present a new method for determining the Galactic gravitational potential based on forward modeling of tidal stellar streams. We use this method to test the performance of smooth and static analytic potentials in representing realistic dark matter halos, which have substructure and are continually evolving by accretion. Our FAST-FORWARD method uses a Markov Chain Monte Carlo algorithm to compare, in six-dimensional phase space, an 'observed' stream to models created in trial analytic potentials. We analyze a large sample of streams that evolved in the Via Lactea II (VL2) simulation, which represents a realistic Galactic halo potential. The recovered potential parameters are in agreement with the best fit to the global, present-day VL2 potential. However, merely assuming an analytic potential limits the dark matter halo mass measurement to an accuracy of 5%-20%, depending on the choice of analytic parameterization. Collectively, the mass estimates using streams from our sample reach this fundamental limit, but individually they can be highly biased. Individual streams can both under- and overestimate the mass, and the bias is progressively worse for those with smaller perigalacticons, motivating the search for tidal streams at galactocentric distances larger than 70 kpc. We estimate that the assumption of a static and smooth dark matter potential in modeling of the GD-1- and Pal5-like streams introduces an error of up to 50% in the Milky Way mass estimates.

  18. Overcooled haloes at z ≥ 10: a route to form low-mass first stars

    CERN Document Server

    Prieto, Joaquin; Verde, Licia

    2014-01-01

    It has been shown by Shchekinov & Vasiliev2006 (SV06) that HD molecules can be an important cooling agent in high redshift z >10 haloes if they undergo mergers under specific conditions so suitable shocks are created. Here we build upon Prieto et al. (2012) who studied in detail the merger-generated shocks, and show that the conditions for HD cooling can be studied by combining these results with a suite of dark-matter only simulations. We have performed a number of dark matter only simulations from cosmological initial conditions inside boxes with sizes from 1 to 4 Mpc. We look for haloes with at least two progenitors of which at least one has mass M > M_cr (z), where M_cr (z) is the SV06 critical mass for HD over-cooling. We find that the fraction of over-cooled haloes with mass between M_cr (z) and 10^{0.2} M_cr (z), roughly below the atomic cooling limit, can be as high as ~ 0.6 at z ~ 10 depending on the merger mass ratio. This fraction decreases at higher redshift reaching a value ~0.2 at z ~ 15. Fo...

  19. The Minimum Halo Mass for Star Formation at z = 6 - 8

    CERN Document Server

    Finlator, K; Oppenheimer, B D; Davé, R; Zackrisson, E; Livermore, R C; Finkelstein, S L; Thompson, R; Huang, S

    2016-01-01

    Recent analysis of strongly-lensed sources in the Hubble Frontier Fields indicates that the rest-frame UV luminosity function of galaxies at $z=$6--8 rises as a power law down to $M_\\mathrm{UV}=-15$, and possibly as faint as -12.5. We use predictions from a cosmological radiation hydrodynamic simulation to map these luminosities onto physical space, constraining the minimum dark matter halo mass and stellar mass that the Frontier Fields probe. While previously-published theoretical studies have suggested or assumed that early star formation was suppressed in halos less massive than $10^9$--$10^{11} M_\\odot$, we find that recent observations demand vigorous star formation in halos at least as massive as (3.1, 5.6, 10.5)$\\times10^9 M_\\odot$ at $z=(6,7,8)$. Likewise, we find that Frontier Fields observations probe down to stellar masses of (8.1, 18, 32)$\\times10^6 M_\\odot$; that is, they are observing the likely progenitors of analogues to Local Group dwarfs such as Pegasus and M32. Our simulations yield somewha...

  20. Determination of the globular cluster and halo stellar mass functions and stellar and brown dwarf densities

    CERN Document Server

    Chabrier, G; Chabrier, Gilles; Méra, Dominique

    1997-01-01

    We use recent low-mass star models, which reproduce accurately the observed sequences of various globular clusters, to convert the observed luminosity functions into bolometric luminosity functions and mass functions down to the bottom of the main sequence. These mass functions are well describedby a slowly rising power-law $dN/dm\\propto m^{-\\alpha}$, with $0.5\\wig < \\alpha \\wig < 1.5$, down to $\\sim 0.1 \\msol$, independently of the metallicity, suggesting a rather universal behaviour of the cluster initial mass functions. We predict luminosity functions in the NICMOS filters in the stellar and in the brown dwarf domains for different mass functions and metallicities. We apply these calculations to the determination, slope and normalization, of the mass function of the Galactic halo (spheroid and dark halo). The spheroid mass function is well described by the afore-mentioned power-law function with function below $\\sim 0.15 \\msol$ can not be excluded with the data presently available. Comparison with th...

  1. Hierarchical formation of Dark Matter Halos near the Free Streaming Scale, and Their Implications on Indirect Dark Matter Search

    Science.gov (United States)

    Ishiyama, Tomoaki

    2016-10-01

    The smallest dark matter halos are formed first in the early universe. According to recent studies, the central density cusp is much steeper in these halos than in larger halos and scales as ρ ~ r -(1.5-1.3). We present results of very large cosmological N-body simulations of the hierarchical formation and evolution of halos over a wide mass range, beginning from the formation of the smallest halos. We confirmed early studies that the inner density cusps are steeper in halos at the free streaming scale. The cusp slope gradually becomes shallower as the halo mass increases. The slope of halos 50 times more massive than the smallest halo is approximately -1.3. The concentration parameter is nearly independent of halo mass, and ruling out simple power law mass-concentration relations. The steeper inner cusps of halos near the free streaming scale enhance the annihilation luminosity of a Milky Way sized halo between 12 to 67%.

  2. The early gaseous and stellar mass assembly of Milky Way-type galaxy haloes

    Science.gov (United States)

    Hensler, Gerhard

    2015-08-01

    In cosmological simulations of Cold Dark Matter (CDM) structure formation a vast number of subhalos is expected around massive galaxies like the Milky Way (MW). These DM subhalos are filled with baryons, gas that forms stars very early as observed from the stellar populations in the MW satellite galaxies. Satellite galaxies evolve in the tidal field of their mature galaxy and suffer accretion to the major galaxy and their partly disruption. By this, their mass loss is expected to feed the galaxy halo with stars and gas.From the Via Lactea II simulations we select a massive DM halo with its satellite system which evolves in the simulations to a present-day MW-type galaxy. We follow its evolution from redshift 4.5 to 2.5, i.e. over almost 2 billion years of the most interesting epoch of mass assembly. A high mass resolution allows for even low-mass satellites down to 10^5 Msun, but limits their distance range to the innermost 240 satellites of the system only. The applied chemo-dynamical method includes star formation, stellar energetic and chemical feedback, and gas physical processes.After the onset of the simulation our models demonstrate the action of tidal effects and satellite merging on the star-formation rate of the satellites, their gas loss by means of hot-gas expansion, of ram-pressure and tidal stripping, and the tidal extraction of stars, leading to the formation of the stellar and gaseous galactic halo. We also analyze the evolution of the satellites’ mass function, their baryonic and DM mass distributions, chemical abundances, their compactness, their present-day appearance, etc. with respect to observations and present-day correlations.

  3. High Accuracy mass Measurement of the very Short-Lived Halo Nuclide $^{11}$Li

    CERN Multimedia

    Le scornet, G

    2002-01-01

    The archetypal halo nuclide $^{11}$Li has now attracted a wealth of experimental and theoretical attention. The most outstanding property of this nuclide, its extended radius that makes it as big as $^{48}$Ca, is highly dependent on the binding energy of the two neutrons forming the halo. New generation experiments using radioactive beams with elastic proton scattering, knock-out and transfer reactions, together with $\\textit{ab initio}$ calculations require the tightening of the constraint on the binding energy. Good metrology also requires confirmation of the sole existing precision result to guard against a possible systematic deviation (or mistake). We propose a high accuracy mass determintation of $^{11}$Li, a particularly challenging task due to its very short half-life of 8.6 ms, but one perfectly suiting the MISTRAL spectrometer, now commissioned at ISOLDE. We request 15 shifts of beam time.

  4. THE CLUSTERING OF ALFALFA GALAXIES: DEPENDENCE ON H I MASS, RELATIONSHIP WITH OPTICAL SAMPLES, AND CLUES OF HOST HALO PROPERTIES

    Energy Technology Data Exchange (ETDEWEB)

    Papastergis, Emmanouil; Giovanelli, Riccardo; Haynes, Martha P.; Jones, Michael G. [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States); Rodríguez-Puebla, Aldo, E-mail: papastergis@astro.cornell.edu, E-mail: riccardo@astro.cornell.edu, E-mail: haynes@astro.cornell.edu, E-mail: jonesmg@astro.cornell.edu, E-mail: apuebla@astro.unam.mx [Instituto de Astronomía, Universidad Nacional Autónoma de México, A. P. 70-264, 04510 México, D.F. (Mexico)

    2013-10-10

    We use a sample of ≈6000 galaxies detected by the Arecibo Legacy Fast ALFA (ALFALFA) 21 cm survey to measure the clustering properties of H I-selected galaxies. We find no convincing evidence for a dependence of clustering on galactic atomic hydrogen (H I) mass, over the range M{sub H{sub I}} ≈ 10{sup 8.5}-10{sup 10.5} M{sub ☉}. We show that previously reported results of weaker clustering for low H I mass galaxies are probably due to finite-volume effects. In addition, we compare the clustering of ALFALFA galaxies with optically selected samples drawn from the Sloan Digital Sky Survey (SDSS). We find that H I-selected galaxies cluster more weakly than even relatively optically faint galaxies, when no color selection is applied. Conversely, when SDSS galaxies are split based on their color, we find that the correlation function of blue optical galaxies is practically indistinguishable from that of H I-selected galaxies. At the same time, SDSS galaxies with red colors are found to cluster significantly more than H I-selected galaxies, a fact that is evident in both the projected as well as the full two-dimensional correlation function. A cross-correlation analysis further reveals that gas-rich galaxies 'avoid' being located within ≈3 Mpc of optical galaxies with red colors. Next, we consider the clustering properties of halo samples selected from the Bolshoi ΛCDM simulation. A comparison with the clustering of ALFALFA galaxies suggests that galactic H I mass is not tightly related to host halo mass and that a sizable fraction of subhalos do not host H I galaxies. Lastly, we find that we can recover fairly well the correlation function of H I galaxies by just excluding halos with low spin parameter. This finding lends support to the hypothesis that halo spin plays a key role in determining the gas content of galaxies.

  5. The Non-Parametric Model for Linking Galaxy Luminosity with Halo/Subhalo Mass: Are First Brightest Galaxies Special?

    CERN Document Server

    Vale, A

    2007-01-01

    We revisit the longstanding question of whether first brightest cluster galaxies are statistically drawn from the same distribution as other cluster galaxies or are "special", using the new non-parametric, empirically based model presented in Vale&Ostriker (2006) for associating galaxy luminosity with halo/subhalo masses. We introduce scatter in galaxy luminosity at fixed halo mass into this model, building a conditional luminosity function (CLF) by considering two possible models: a simple lognormal and a model based on the distribution of concentration in haloes of a given mass. We show that this model naturally allows an identification of halo/subhalo systems with groups and clusters of galaxies, giving rise to a clear central/satellite galaxy distinction. We then use these results to build up the dependence of brightest cluster galaxy (BCG) magnitudes on cluster luminosity, focusing on two statistical indicators, the dispersion in BCG magnitude and the magnitude difference between first and second bri...

  6. A statistical investigation of the mass discrepancy-acceleration relation

    Science.gov (United States)

    Desmond, Harry

    2017-02-01

    We use the mass discrepancy-acceleration relation (the correlation between the ratio of total-to-visible mass and acceleration in galaxies; MDAR) to test the galaxy-halo connection. We analyse the MDAR using a set of 16 statistics that quantify its four most important features: shape, scatter, the presence of a `characteristic acceleration scale', and the correlation of its residuals with other galaxy properties. We construct an empirical framework for the galaxy-halo connection in LCDM to generate predictions for these statistics, starting with conventional correlations (halo abundance matching; AM) and introducing more where required. Comparing to the SPARC data, we find that: (1) the approximate shape of the MDAR is readily reproduced by AM, and there is no evidence that the acceleration at which dark matter becomes negligible has less spread in the data than in AM mocks; (2) even under conservative assumptions, AM significantly overpredicts the scatter in the relation and its normalization at low acceleration, and furthermore positions dark matter too close to galaxies' centres on average; (3) the MDAR affords 2σ evidence for an anticorrelation of galaxy size and Hubble type with halo mass or concentration at fixed stellar mass. Our analysis lays the groundwork for a bottom-up determination of the galaxy-halo connection from relations such as the MDAR, provides concrete statistical tests for specific galaxy formation models, and brings into sharper focus the relative evidence accorded by galaxy kinematics to LCDM and modified gravity alternatives.

  7. Cosmology with velocity dispersion counts: an alternative to measuring cluster halo masses

    Science.gov (United States)

    Caldwell, C. E.; McCarthy, I. G.; Baldry, I. K.; Collins, C. A.; Schaye, J.; Bird, S.

    2016-11-01

    The evolution of galaxy cluster counts is a powerful probe of several fundamental cosmological parameters. A number of recent studies using this probe have claimed tension with the cosmology preferred by the analysis of the Planck primary cosmic microwave background (CMB) data, in the sense that there are fewer clusters observed than predicted based on the primary CMB cosmology. One possible resolution to this problem is systematic errors in the absolute halo mass calibration in cluster studies, which is required to convert the standard theoretical prediction (the halo mass function) into counts as a function of the observable (e.g. X-ray luminosity, Sunyaev-Zel'dovich flux, and optical richness). Here we propose an alternative strategy, which is to directly compare predicted and observed cluster counts as a function of the one-dimensional velocity dispersion of the cluster galaxies. We argue that the velocity dispersion of groups/clusters can be theoretically predicted as robustly as mass but, unlike mass, it can also be directly observed, thus circumventing the main systematic bias in traditional cluster counts studies. With the aid of the BAHAMAS suite of cosmological hydrodynamical simulations, we demonstrate the potential of the velocity dispersion counts for discriminating even similar Λ cold dark matter models. These predictions can be compared with the results from existing redshift surveys such as the highly complete Galaxy And Mass Assembly survey, and upcoming wide-field spectroscopic surveys such as the Wide Area Vista Extragalactic Survey and the Dark Energy Survey Instrument.

  8. Mass measurement of halo nuclides and beam cooling with the mass spectrometer Mistral; Mesure de masse de noyaux a halo et refroidissement de faisceaux avec l'experience MISTRAL

    Energy Technology Data Exchange (ETDEWEB)

    Bachelet, C

    2004-12-01

    Halo nuclides are a spectacular drip-line phenomenon and their description pushes nuclear theories to their limits. The most critical input parameter is the nuclear binding energy; a quantity that requires excellent measurement precision, since the two-neutron separation energy is small at the drip-line by definition. Moreover halo nuclides are typically very short-lived. Thus, a high accuracy instrument using a quick method of measurement is necessary. MISTRAL is such an instrument; it is a radiofrequency transmission mass spectrometer located at ISOLDE/CERN. In July 2003 we measured the mass of the Li{sup 11}, a two-neutron halo nuclide. Our measurement improves the precision by a factor 6, with an error of 5 keV. Moreover the measurement gives a two-neutron separation energy 20% higher than the previous value. This measurement has an impact on the radius of the nucleus, and on the state of the two valence neutrons. At the same time, a measurement of the Be{sup 11} was performed with an uncertainty of 4 keV, in excellent agreement with previous measurements. In order to measure the mass of the two-neutron halo nuclide Be{sup 14}, an ion beam cooling system is presently under development which will increase the sensitivity of the spectrometer. The second part of this work presents the development of this beam cooler using a gas-filled Paul trap. (author)

  9. The HI Mass Density in Galactic Halos, Winds, and Cold Accretion as Traced by MgII Absorption

    CERN Document Server

    Kacprzak, G G

    2011-01-01

    It is well established that MgII absorption lines detected in background quasar spectra arise from gas structures associated with foreground galaxies. The degree to which galaxy evolution is driven by the gas cycling through halos is highly uncertain because their gas mass density is poorly constrained. Fitting the MgII equivalent width (W) distribution with a Schechter function and applying the N(HI)-W correlation of Menard & Chelouche, we computed Omega(HI)_MgII ~ Omega(HI)_halo =(1.41 +0.75 -0.44)x10^-4 for 0.4halo comprises accreting and/or outflowing halo gas not locked up in cold neutral clouds. We deduce the cosmic HI gas mass density fraction in galactic halos traced by MgII absorption is Omega(HI)_halo/Omega(HI)_DLA=15% and Omega(HI)_halo/Omega_b=0.3%. Citing several lines of evidence, we propose infall/accretion material is sampled by small W whereas outflow/winds are sampled by large W, and find Omega(HI)_infall is consistent...

  10. RASS-SDSS Galaxy Cluster Survey. VII. On the Cluster Mass to Light ratio and the Halo Occupation Distribution

    CERN Document Server

    Popesso, P; Böhringer, Hans; Romaniello, M

    2006-01-01

    We explore the mass-to-light ratio in galaxy clusters and its relation to the cluster mass. We study the relations among the optical luminosity ($L_{op}$), the cluster mass ($M_{200}$) and the number of cluster galaxies within $r_{200}$ ($N_{gal}$) in a sample of 217 galaxy clusters with confirmed 3D overdensity. We correct for projection effects, by determining the galaxy surface number density profile in our cluster sample. This is best fitted by a cored King profile in low and intermediate mass systems. The core radius decreases with cluster mass, and, for the highest mass clusters, the profile is better represented by a generalized King profile or a cuspy Navarro, Frenk & White profile. We find a very tight proportionality between $L_{op}$ and $N_{gal}$, which, in turn, links the cluster mass-to-light ratio to the Halo Occupation Distribution $N_{gal}$ vs. $M_{200}$. After correcting for projection effects, the slope of the $L_{op}-M_{200}$ and $N_{gal}-M_{200}$ relations is found to be $0.92\\pm0.03$,...

  11. Galaxy-galaxy Lensing: Dissipationless Simulations Versus the Halo Model

    CERN Document Server

    Mandelbaum, R; Seljak, U; Kravtsov, A V; Wechsler, R H; Mandelbaum, Rachel; Tasitsiomi, Argyro; Seljak, Uros; Kravtsov, Andrey V.; Wechsler, Risa H.

    2004-01-01

    Galaxy-galaxy lensing is a powerful probe of the relation between galaxies and dark matter halos, but its theoretical interpretation requires a careful modeling of various contributions, such as the contribution from central and satellite galaxies. For this purpose, a phenomenological approach based on the halo model has been developed, allowing for fast exploration of the parameter space of models. In this paper, we investigate the ability of the halo model to extract information from the g-g weak lensing signal by comparing it to high-resolution dissipationless simulations that resolve subhalos. We find that the halo model reliably determines parameters such as the host halo mass of central galaxies, the fraction of galaxies that are satellites, and their radial distribution inside larger halos. If there is a significant scatter present in the central galaxy host halo mass distribution, then the mean and median mass of that distribution can differ significantly from one another, and the halo model mass dete...

  12. Cosmology with velocity dispersion counts: an alternative to measuring cluster halo masses

    CERN Document Server

    Caldwell, C E; Baldry, I K; Collins, C A; Schaye, J; Bird, S

    2016-01-01

    The evolution of galaxy cluster counts is a powerful probe of several fundamental cosmological parameters. A number of recent studies using this probe have claimed tension with the cosmology preferred by the analysis of the Planck primary CMB data, in the sense that there are fewer clusters observed than predicted based on the primary CMB cosmology. One possible resolution to this problem is systematic errors in the absolute halo mass calibration in cluster studies, which is required to convert the standard theoretical prediction (the halo mass function) into counts as a function of the observable (e.g., X-ray luminosity, Sunyaev-Zel'dovich flux, optical richness). Here we propose an alternative strategy, which is to directly compare predicted and observed cluster counts as a function of the one-dimensional velocity dispersion of the cluster galaxies. We argue that the velocity dispersion of groups/clusters can be theoretically predicted as robustly as mass but, unlike mass, it can also be directly observed, ...

  13. The Mass Dependance of Satellite Quenching in Milky Way-like Halos

    CERN Document Server

    Phillips, John I; Cooper, Michael C; Boylan-Kolchin, Michael; Bullock, James S; Tollerud, Erik

    2014-01-01

    Using the Sloan Digital Sky Survey, we examine the quenching of satellite galaxies around isolated Milky Way-like hosts in the local Universe. We find that the efficiency of satellite quenching around isolated galaxies is low and roughly constant over two orders of magnitude in satellite stellar mass ($M_{*}$ = $10^{8.5}-10^{10.5} \\, M_{\\odot}$), with only $\\sim~20\\%$ of systems quenched as a result of environmental processes. While largely independent of satellite stellar mass, satellite quenching does exhibit clear dependence on the properties of the host. We show that satellites of passive hosts are substantially more likely to be quenched than those of star-forming hosts, and we present evidence that more massive halos quench their satellites more efficiently. These results extend trends seen previously in more massive host halos and for higher satellite masses. Taken together, it appears that galaxies with stellar masses larger than about $10^{8}~M_{\\odot}$ are uniformly resistant to environmental quench...

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

    CERN Document Server

    Williams, A A

    2015-01-01

    We develop a flexible set of action-based distribution functions (DFs) for stellar halos. The DFs have five free parameters, controlling the inner and outer density slope, break radius, flattening and anisotropy respectively. The DFs generate flattened stellar halos 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 $\\ap...

  15. Cosmology with massive neutrinos I: towards a realistic modeling of the relation between matter, haloes and galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Villaescusa-Navarro, Francisco; Viel, Matteo [INAF - Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34143, Trieste (Italy); Marulli, Federico [Dipartimento di Fisica e Astronomia - Università di Bologna, viale Berti Pichat 6/2, I-40127 Bologna (Italy); Branchini, Enzo [Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma (Italy); Castorina, Emanuele [SISSA - International School For Advanced Studies, Via Bonomea, 265 34136 Trieste (Italy); Sefusatti, Emiliano [The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, 34151, Trieste (Italy); Saito, Shun, E-mail: villaescusa@oats.inaf.it, E-mail: federico.marulli3@unibo.it, E-mail: viel@oats.inaf.it, E-mail: branchin@fis.uniroma3.it, E-mail: ecastori@sissa.it, E-mail: esefusat@ictp.it, E-mail: shun.saito@ipmu.jp [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, The University of Tokyo, Chiba 277-8582 (Japan)

    2014-03-01

    By using a suite of large box-size N-body simulations that incorporate massive neutrinos as an extra set of particles, with total masses of 0.15, 0.30, and 0.60 eV, we investigate the impact of neutrino masses on the spatial distribution of dark matter haloes and on the distribution of galaxies within the haloes. We compute the bias between the spatial distribution of dark matter haloes and the overall matter and cold dark matter distributions using statistical tools such as the power spectrum and the two-point correlation function. Overall we find a scale-dependent bias on large scales for the cosmologies with massive neutrinos. In particular, we find that the bias decreases with the scale, being this effect more important for higher neutrino masses and at high redshift. However, our results indicate that the scale-dependence in the bias is reduced if the latter is computed with respect to the cold dark matter distribution only. We find that the value of the bias on large scales is reasonably well reproduced by the Tinker fitting formula once the linear cold dark matter power spectrum is used, instead of the total matter power spectrum. We also investigate whether scale-dependent bias really comes from purely neutrino's effect or from nonlinear gravitational collapse of haloes. For this purpose, we address the Ω{sub ν}-σ{sub 8} degeneracy and find that such degeneracy is not perfect, implying that neutrinos imprint a slight scale dependence on the large-scale bias. Finally, by using a simple halo occupation distribution (HOD) model, we investigate the impact of massive neutrinos on the distribution of galaxies within dark matter haloes. We use the main galaxy sample in the Sloan Digital Sky Survey (SDSS) II Data Release 7 to investigate if the small-scale galaxy clustering alone can be used to discriminate among different cosmological models with different neutrino masses. Our results suggest that different choices of the HOD parameters can reproduce the

  16. An Improved Calculation of the Non-Gaussian Halo Mass Function

    CERN Document Server

    D'Amico, Guido; Noreña, Jorge; Paranjape, Aseem

    2010-01-01

    The abundance of collapsed objects in the universe, or halo mass function, is an important theoretical tool in studying the effects of primordially generated non-Gaussianities on the large scale structure. The non-Gaussian mass function has been calculated by several authors in different ways, typically by exploiting the smallness of certain parameters which naturally appear in the calculation, to set up a perturbative expansion. We improve upon the existing results for the mass function by combining path integral methods and saddle point techniques (which have been separately applied in previous approaches). Additionally, we carefully account for the various scale dependent combinations of small parameters which appear. Some of these combinations in fact become of order unity for large mass scales and at high redshifts, and must therefore be treated non-perturbatively. Our approach allows us to do this, and to also account for multi-scale density correlations which appear in the calculation. We thus derive a...

  17. Blending bias impacts the host halo masses derived from a cross-correlation analysis of bright sub-millimetre galaxies

    CERN Document Server

    Cowley, William I; Baugh, Carlton M; Cole, Shaun; Wilkinson, Aaron

    2016-01-01

    Placing bright sub-millimetre galaxies (SMGs) within the broader context of galaxy formation and evolution requires accurate measurements of their clustering, which can constrain the masses of their host dark matter halos. Recent work has shown that the clustering measurements of these galaxies may be affected by a `blending bias,' which results in the angular correlation function of the sources extracted from single-dish imaging surveys being boosted relative to that of the underlying galaxies. This is due to confusion introduced by the coarse angular resolution of the single-dish telescope and could lead to the inferred halo masses being significantly overestimated. We investigate the extent to which this bias affects the measurement of the correlation function of SMGs when it is derived via a cross-correlation with a more abundant galaxy population. We find that the blending bias is essentially the same as in the auto-correlation case and conclude that the best way to reduce its effects is to calculate the...

  18. A new direction for dark matter research: intermediate mass compact halo objects

    CERN Document Server

    Axelrod, T; Dawson, W; Frampton, P H

    2016-01-01

    The failure to find evidence for elementary particles that could serve as the constituents of dark matter brings to mind suggestions that dark matter might consist of massive compact objects (MACHOs). In particular, it has recently been argued that MACHOs with masses > 15 solar masses may have been prolifically produced at the onset of the big bang. Although a variety of astrophysical signatures for primordial MACHOs with masses in this range have been discussed in the literature, we favor a strategy that uses the potential for gravitational microlensing of stars outside our galaxy to directly detect the presence of MACHOs in the halo of our galaxy. We point out that the effect of the motion of the Earth on the shape of the microlensing brightening curves provides a promising approach to confirming over the course of next several years that dark matter consists of MACHOs.

  19. A prescription for the conditional mass function of dark matter haloes

    CERN Document Server

    Rubiño-Martín, J A; Patiri, S

    2008-01-01

    [ABRIDGED] The unconditional mass function (UMF) of dark matter haloes has been determined accurately in the literature, showing excellent agreement with high resolution numerical simulations. However, this is not the case for the conditional mass function (CMF). We propose a simple analytical procedure to derive the CMF by rescaling the UMF to the constrained environment using the appropriate mean and variance of the density field at the constrained point. This method introduces two major modifications with respect to the standard re-scaling procedure. First of all, rather than using in the scaling procedure the properties of the environment averaged over all the conditioning region, we implement the re-scaling locally. We show that for high masses this modification may lead to substantially different results. Secondly, we modify the (local) standard re-scaling procedure in such a manner as to force normalisation, in the sense that when one integrates the CMF over all possible values of the constraint multip...

  20. Formation and Assembly History of Stellar Components in Galaxies as a Function of Stellar and Halo Mass

    Science.gov (United States)

    Lee, Jaehyun; Yi, Sukyoung K.

    2017-02-01

    Galaxy mass assembly is an end product of structure formation in the ΛCDM cosmology. As an extension of Lee & Yi, we investigate the assembly history of stellar components in galaxies as a function of halo environments and stellar mass using semi-analytic approaches. In our fiducial model, halo mass intrinsically determines the formation and assembly of the stellar mass. Overall, the ex situ fraction slowly increases in central galaxies with increasing halo mass but sharply increases for {log}{M}* /{M}ȯ ≳ 11. A similar trend is also found in satellite galaxies, which implies that mergers are essential to build stellar masses above {log}{M}* /{M}ȯ ∼ 11. We also examine the time evolution of the contribution of mass growth channels. Mergers become the primary channel in the mass growth of central galaxies when their host halo mass begins to exceed {log}{M}200/{M}ȯ ∼ 13. However, satellite galaxies seldom reach the merger-dominant phase despite their reduced star-formation activities due to environmental effects.

  1. On the stability of satellite planes - I. Effects of mass, velocity, halo shape and alignment

    Science.gov (United States)

    Fernando, Nuwanthika; Arias, Veronica; Guglielmo, Magda; Lewis, Geraint F.; Ibata, Rodrigo A.; Power, Chris

    2017-02-01

    The recently discovered vast thin plane of dwarf satellites orbiting the Andromeda Galaxy (M31) adds to the mystery of the small-scale distribution of the Local Group's galaxy population. Such well-defined planar structures are apparently rare occurrences in cold dark matter cosmological simulations, and we lack a coherent explanation of their formation and existence. In this paper, we explore the long-term survivability of thin planes of dwarfs in galactic haloes, focusing, in particular, on systems mimicking the observed Andromeda distribution. The key results show that, in general, planes of dwarf galaxies are fragile, sensitive to the shape of the dark matter halo and other perturbing effects. In fact, long-lived planes of satellites only exist in polar orbits in spherical dark matter haloes, presenting a challenge to the observed Andromeda plane that is significantly tilted with respect to the optical disc. Our conclusion is that, in the standard cosmological models, planes of satellites are generally short lived, and hence we must be located at a relatively special time in the evolution of the Andromeda Plane, lucky enough to see its coherent pattern.

  2. Galaxy halo masses and satellite fractions from galaxy-galaxy lensing in the SDSS: stellar mass, luminosity, morphology, and environment dependencies

    CERN Document Server

    Mandelbaum, R; Kauffmann, G; Hirata, C M; Brinkmann, J; Mandelbaum, Rachel; Seljak, Uros; Kauffmann, Guinevere; Hirata, Christopher M.; Brinkmann, Jonathan

    2006-01-01

    The relationship between galaxies and dark matter can be characterized by the halo mass of the central galaxy and the fraction of galaxies that are satellites. Here we present observational constraints from the SDSS on these quantities as a function of r-band luminosity and stellar mass using galaxy-galaxy weak lensing, with a total of 351,507 lenses. We use stellar masses derived from spectroscopy and virial halo masses derived from weak gravitational lensing to determine the efficiency with which baryons in the halo of the central galaxy have been converted into stars. We find that an L* galaxy with a stellar mass of 6x10^{10} M_{sun} is hosted by a halo with mass of 1.4x10^{12} M_{sun}/h, independent of morphology, yielding baryon conversion efficiencies of 17_{-5}^{+10} (early types) and 16_{-6}^{+15} (late types) per cent at the 95 per cent CL (statistical, not including systematic uncertainty due to assumption of a universal initial mass function, or IMF). We find that for a given stellar mass, the halo...

  3. A new direction for dark matter research: intermediate-mass compact halo objects

    Science.gov (United States)

    Chapline, George F.; Frampton, Paul H.

    2016-11-01

    The failure to find evidence for elementary particles that could serve as the constituents of dark matter brings to mind suggestions that dark matter might consist of massive compact objects (MACHOs). In particular, it has recently been argued that MACHOs with masses > 15Msolar may have been prolifically produced at the onset of the big bang. Although a variety of astrophysical signatures for primordial MACHOs with masses in this range have been discussed in the literature, we favor a strategy that uses the potential for magnification of stars outside our galaxy due to gravitational microlensing of these stars by MACHOs in the halo of our galaxy. We point out that the effect of the motion of the Earth on the shape of the micro-lensing brightening curves provides a promising approach to testing over the course of next several years the hypothesis that dark matter consists of massive compact objects.

  4. THE INFLUENCE OF DARK MATTER HALOS ON DYNAMICAL ESTIMATES OF BLACK HOLE MASS: 10 NEW MEASUREMENTS FOR HIGH-{sigma} EARLY-TYPE GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Rusli, S. P.; Thomas, J.; Saglia, R. P.; Fabricius, M.; Erwin, P.; Bender, R. [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Nowak, N. [Max-Planck-Institut fuer Physik, Foehringer Ring 6, D-80805 Muenchen (Germany); Lee, C. H.; Riffeser, A. [Universitaets-Sternwarte Muenchen, Scheinerstrasse 1, D-81679 Muenchen (Germany); Sharp, R. [Anglo-Australian Observatory, P.O. Box 296, Epping, NSW 1710 (Australia)

    2013-09-15

    Adaptive optics assisted SINFONI observations of the central regions of 10 early-type galaxies are presented. Based primarily on the SINFONI kinematics, 10 black hole (BH) masses occupying the high-mass regime of the M{sub BH}-{sigma} relation are derived using three-integral Schwarzschild models. The effect of dark matter (DM) inclusion on the BH mass is explored. The omission of a DM halo in the model results in a higher stellar mass-to-light ratio, especially when extensive kinematic data are used in the model. However, when the diameter of the sphere of influence-computed using the BH mass derived without a dark halo-is at least 10 times the point-spread function FWHM during the observations, it is safe to exclude a DM component in the dynamical modeling, i.e., the change in BH mass is negligible. When the spatial resolution is marginal, restricting the mass-to-light ratio to the right value returns the correct M{sub BH} although a dark halo is not present in the model. Compared to the M{sub BH}-{sigma} and M{sub BH}-L relations of McConnell et al., the 10 BHs are all more massive than expected from the luminosities and 7 BH masses are higher than expected from the stellar velocity dispersions of the host bulges. Using new fitted relations, which include the 10 galaxies, we find that the space density of the most massive BHs (M{sub BH} {approx}> 10{sup 9} M{sub Sun }) estimated from the M{sub BH}-L relation is higher than the estimate based on the M{sub BH}-{sigma} relation and the latter is higher than model predictions based on quasar counts, each by about an order of magnitude.

  5. The effect of feedback and reionization on star formation in low-mass dwarf galaxy haloes

    CERN Document Server

    Simpson, Christine M; Johnston, Kathryn V; Smith, Britton D; Mac Low, Mordecai-Mark; Sharma, Sanjib; Tumlinson, Jason

    2012-01-01

    We simulate the evolution of a 10^9 Msun dark matter halo in a cosmological setting with an adaptive-mesh refinement code as an analogue to local low luminosity dwarf irregular and dwarf spheroidal galaxies. The primary goal of our study is to investigate the roles of reionization and supernova feedback in determining the star formation histories of low mass dwarf galaxies. We include a wide range of physical effects, including metal cooling, molecular hydrogen formation and cooling, photoionization and photodissociation from a metagalactic background, a simple prescription for self-shielding, star formation, and a simple model for supernova driven energetic feedback. We carry out simulations excluding each major effect in turn. We find that reionization is primarily responsible for expelling most of the gas in our simulations, but that supernova feedback is required to disperse the dense, cold gas in the core of the halo. Moreover, we show that the timing of reionization can produce an order of magnitude dif...

  6. The Magellanic Stream Revisited - The Halo Mass of the Galaxy in the Range of 100 KPC

    Science.gov (United States)

    Murai, T.

    There is still a controversy on the mass of the Galaxy in the deep halo, some still advocates a conservative view where the rotation velocity ultimately decays as in accord with the Keplerian law at the distance of 50 kpc, while others become to consider that the rotation curve of the Milky Way, essentially, stays flat or is still increasing at the distance of the Magellanic Clouds and the Magellanic Stream. On the basis of the accurate observed data of the spatial location of the LMC, SMC and the Magellanic Stream and their radial velocity distribution, it is clarified that the halo of the Galaxy has a huge dark matter, resulting in a flat rotation curve with the terminal velocity of the order of 250 km/s. It is shown that the tidal interaction of the LMC and the SMC has produced a number of charcteristics, a series of burst of star formation, kinematic peculiarities within the both Clouds, collision-induced imprints, etc. All have, observationally, been revealed and interpreted as a result of at least two close encounters of the LMC and the SMC, which can occur only in the deep gravitational potential of dark matter as shown by a tidal simulation of Murai and Fujimoto (1980).

  7. The impact of baryons on massive galaxy clusters: halo structure and cluster mass estimates

    Science.gov (United States)

    Henson, Monique A.; Barnes, David J.; Kay, Scott T.; McCarthy, Ian G.; Schaye, Joop

    2017-03-01

    We use the BAHAMAS (BAryons and HAloes of MAssive Systems) and MACSIS (MAssive ClusterS and Intercluster Structures) hydrodynamic simulations to quantify the impact of baryons on the mass distribution and dynamics of massive galaxy clusters, as well as the bias in X-ray and weak lensing mass estimates. These simulations use the subgrid physics models calibrated in the BAHAMAS project, which include feedback from both supernovae and active galactic nuclei. They form a cluster population covering almost two orders of magnitude in mass, with more than 3500 clusters with masses greater than 1014 M⊙ at z = 0. We start by characterizing the clusters in terms of their spin, shape and density profile, before considering the bias in both weak lensing and hydrostatic mass estimates. Whilst including baryonic effects leads to more spherical, centrally concentrated clusters, the median weak lensing mass bias is unaffected by the presence of baryons. In both the dark matter only and hydrodynamic simulations, the weak lensing measurements underestimate cluster masses by ≈10 per cent for clusters with M200 ≤ 1015 M⊙ and this bias tends to zero at higher masses. We also consider the hydrostatic bias when using both the true density and temperature profiles, and those derived from X-ray spectroscopy. When using spectroscopic temperatures and densities, the hydrostatic bias decreases as a function of mass, leading to a bias of ≈40 per cent for clusters with M500 ≥ 1015 M⊙. This is due to the presence of cooler gas in the cluster outskirts. Using mass weighted temperatures and the true density profile reduces this bias to 5-15 per cent.

  8. Dark-matter halo mergers as a fertile environment for low-mass Population III star formation

    DEFF Research Database (Denmark)

    Bovino, S.; Latif, M. A.; Grassi, Tommaso

    2014-01-01

    While Population III (Pop III) stars are typically thought to be massive, pathways towards lower mass Pop III stars may exist when the cooling of the gas is particularly enhanced. A possible route is enhanced HD cooling during the merging of dark-matter haloes. The mergers can lead to a high ioni...... ionization degree catalysing the formation of HD molecules and may cool the gas down to the cosmic microwave background temperature. In this paper, we investigate the merging of mini-haloes with masses of a few 105 M⊙ and explore the feasibility of this scenario. We have performed three......-dimensional cosmological hydrodynamics calculations with the enzo code, solving the thermal and chemical evolution of the gas by employing the astrochemistry package krome. Our results show that the HD abundance is increased by two orders of magnitude compared to the no-merging case and the halo cools down to ∼60 K...

  9. High-precision Penning trap mass measurements of 9,10Be and the one-neutron halo nuclide 11Be

    Science.gov (United States)

    Ringle, R.; Brodeur, M.; Brunner, T.; Ettenauer, S.; Smith, M.; Lapierre, A.; Ryjkov, V. L.; Delheij, P.; Drake, G. W. F.; Lassen, J.; Lunney, D.; Dilling, J.

    2009-05-01

    Penning trap mass measurements of 9Be, 10Be (t1 / 2 = 1.51 My), and the one-neutron halo nuclide 11Be (t1 / 2 = 13.8 s) have been performed using TITAN at TRIUMF. The resulting 11Be mass excess (ME = 20 177.60 (58) keV) is in agreement with the current Atomic Mass Evaluation (AME03) [G. Audi, et al., Nucl. Phys. A 729 (2003) 337] value, but is over an order of magnitude more precise. The precision of the mass values of 9,10Be have been improved by about a factor of four and reveal a ≈ 2 σ deviation from the AME mass values. Results of new atomic physics calculations are presented for the isotope shift of 11Be relative to 9Be, and it is shown that the new mass values essentially remove atomic mass uncertainties as a contributing factor in determining the relative nuclear charge radius from the isotope shift. The new mass values of 10,11Be also allow for a more precise determination of the single-neutron binding energy of the halo neutron in 11Be.

  10. Halo statistics in non-Gaussian cosmologies: the collapsed fraction, conditional mass function, and halo bias from the path-integral excursion set method

    CERN Document Server

    D'Aloisio, Anson; Jeong, Donghui; Shapiro, Paul R

    2012-01-01

    Characterizing the level of primordial non-Gaussianity (PNG) in the initial conditions for structure formation is one of the most promising ways to test inflation and differentiate among different scenarios. The scale-dependent imprint of PNG on the large-scale clustering of galaxies and quasars has already been used to place significant constraints on the level of PNG in our observed Universe. Such measurements depend upon an accurate and robust theory for how PNG affects the bias of galactic halos relative to the underlying matter density field. We improve upon previous work by employing a more general analytical method - the path-integral extension of the excursion set formalism - which is able to account for the non-Markovianity caused by PNG in the random-walk model used to identify halos in the initial density field. This non-Markovianity encodes information about environmental effects on halo formation which have so far not been taken into account in analytical bias calculations. We compute both scale-...

  11. On the Origin of the Inner Structure of Halos

    CERN Document Server

    Manrique, A; Salvador-Solé, E; Sanchis, T; Solanes, J M; Manrique, Alberto; Raig, Andreu; Salvador-Sole, Eduard; Sanchis, Teresa; Solanes, Jose M.

    2003-01-01

    We calculate by means of the Press-Schechter formalism the density profile developed by dark-matter halos during accretion, i.e., the continuous aggregation of small clumps. We find that the shape of the predicted profile is similar to that shown by halos in high-resolution cosmological simulations. Furthermore, the mass-concentration relation is correctly reproduced at any redshift in all the hierarchical cosmologies analyzed, except for very large halo masses. The role of major mergers, which can cause the rearrangement of the halo structure through violent relaxation, is also investigated. We show that, as a result of the boundary conditions imposed by the matter continuously infalling into the halo during the violent relaxation process, the shape of the density profile emerging from major mergers is essentially identical to the shape the halo would have developed through pure accretion. This result explains why, according to high-resolution cosmological simulations, relaxed halos of a given mass have the ...

  12. Satellite Quenching in Relation to Galaxy Inner Density and the Halo Environment

    CERN Document Server

    Woo, J; Faber, S M; Dekel, A; Tacchella, S

    2016-01-01

    Using the Sloan Digital Sky Survey, we adopt the sSFR-$\\Sigma_{1kpc}$ diagram as a diagnostic tool to understand the nature of quenching in different environments. sSFR is the specific star formation rate, and $\\Sigma_{1kpc}$ is the stellar surface density in the inner kpc. Although both the host halo mass and group-centric distance affect the satellite population, we find that these two properties can be characterised by a single number, the quenched fraction, such that key features of the sSFR-$\\Sigma_{1kpc}$ diagram vary smoothly with this proxy for the "environment". Particularly, the sSFR of star-forming galaxies decreases smoothly with the quenched fraction of a given environment. Furthermore, the location of the transition galaxies (i.e., the "green valley" or GV) in the sSFR-$\\Sigma_{1kpc}$ diagram also varies smoothly with the environment, $\\Sigma_{1kpc}$ being lower for satellites than the field, and lower for satellites in larger halos and at smaller radial distances within the same-mass halos. We ...

  13. Very Low-Mass Stars with Extremely Low Metallicity in the Milky Way's Halo

    Science.gov (United States)

    Aoki, Wako; Beers, Timothy C.; Suda, Takuma; Honda, Satoshi; Lee, Young Sun

    2016-08-01

    Large surveys and follow-up spectroscopic studies in the past few decades have been providing chemical abundance data for a growing number of very metal-poor ([Fe/H] LTE model atmospheres has obtained self-consistent chemical abundances for these objects, assuming small values of micro-turbulent velocities compared with giants and turn-off stars. The low temperature of the atmospheres of these objects enables us to measure their detailed chemical abundances. Interestingly, two of the four stars have extreme chemical-abundance patterns: one has the largest excesses of heavy neutron-capture elements associated with the r-process abundance pattern known to date (Aoki et al. 2010), and the other exhibits low abundances of the α-elements and odd-Z elements, suggested to be signatures of the yields of very massive stars (> 100 solar masses; Aoki et al. 2014). Although the sample size is still small, these results indicate the potential of very low-mass stars as probes to study the early stages of the Milky Way's halo formation.

  14. RADIAL AND AZIMUTHAL OSCILLATIONS OF HALO CORONAL MASS EJECTIONS IN THE SUN

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Harim; Moon, Y.-J.; Nakariakov, V. M., E-mail: harim@khu.ac.kr, E-mail: moonyj@khu.ac.kr, E-mail: V.Nakariakov@warwick.ac.uk [School of Space Research, Kyung Hee University, Yongin 446-701 (Korea, Republic of)

    2015-04-10

    We present the first observational detection of radial and azimuthal oscillations in full halo coronal mass ejections (HCMEs). We analyze nine HCMEs well-observed by the Large Angle and Spectrometric Coronagraph (LASCO) from 2011 February to June. Using the LASCO C3 running difference images, we estimated the instantaneous apparent speeds of the HCMEs in different radial directions from the solar disk center. We find that the development of all these HCMEs is accompanied by quasi-periodic variations of the instantaneous radial velocity with the periods ranging from 24 to 48 minutes. The amplitudes of the instant speed variations reach about a half of the projected speeds. The amplitudes are found to anti-correlate with the periods and correlate with the HCME speed, indicating the nonlinear nature of the process. The oscillations have a clear azimuthal structure in the heliocentric polar coordinate system. The oscillations in seven events are found to be associated with distinct azimuthal wave modes with the azimuthal wave number m = 1 for six events and m = 2 for one event. The polarization of the oscillations in these seven HCMEs is broadly consistent with those of their position angles with the mean difference of 43°. The oscillations may be connected with natural oscillations of the plasmoids around a dynamical equilibrium, or self-oscillatory processes, e.g., the periodic shedding of Alfvénic vortices. Our results indicate the need for an advanced theory of oscillatory processes in coronal mass ejections.

  15. CFHTLenS: The Environmental Dependence of Galaxy Halo Masses from Weak Lensing

    CERN Document Server

    Gillis, Bryan R; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Hoekstra, Henk; Kitching, Thomas D; Mellier, Yannick; Miller, Lance; van Waerbeke, Ludovic; Bonnett, Christopher; Coupon, Jean; Fu, Liping; Hilbert, Stefan; Rowe, Barnaby T P; Schrabback, Tim; Semboloni, Elisabetta; van Uitert, Edo; Velander, Malin

    2013-01-01

    We use weak gravitational lensing to analyse the dark matter halos around satellite galaxies in galaxy groups in the CFHTLenS dataset. This dataset is derived from the CFHTLS-Wide survey, and encompasses 154 sq. deg of high-quality shape data. Using the photometric redshifts, we divide the sample of lens galaxies with stellar masses in the range 10^9 Msun to 10^10.5 Msun into those likely to lie in high-density environments (HDE) and those likely to lie in low-density environments (LDE). Through comparison with galaxy catalogues extracted from the Millennium Simulation, we show that the sample of HDE galaxies should primarily (~61%) consist of satellite galaxies in groups, while the sample of LDE galaxies should consist of mostly (~87%) non-satellite (field and central) galaxies. Comparing the lensing signals around samples of HDE and LDE galaxies matched in stellar mass, the lensing signal around HDE galaxies clearly shows a positive contribution from their host groups on their lensing signals at radii of ~5...

  16. On the occurrence of Radio Halos in galaxy clusters - Insight from a mass-selected sample

    CERN Document Server

    Cuciti, V; Brunetti, G; Dallacasa, D; Kale, R; Ettori, S; Venturi, T

    2015-01-01

    Giant radio halos (RH) are diffuse Mpc-scale synchrotron sources detected in a fraction of massive and merging galaxy clusters. An unbiased study of the statistical properties of RHs is crucial to constrain their origin and evolution. We aim at investigating the occurrence of RHs and its dependence on the cluster mass in a SZ-selected sample of galaxy clusters, which is as close as possible to be a mass-selected sample. Moreover, we analyse the connection between RHs and merging clusters. We select from the Planck SZ catalogue (Planck Collaboration XXIX 2014) clusters with $M\\geq 6\\times10^{14} M_\\odot$ at z=0.08-0.33 and we search for the presence of RHs using the NVSS for z<0.2 and the GMRT RH survey (GRHS, Venturi et al. 2007, 2008) and its extension (EGRHS, Kale et al. 2013, 2015) for 0.2

  17. Connecting Galaxies, Halos, and Star Formation Rates Across Cosmic Time

    CERN Document Server

    Conroy, Charlie

    2008-01-01

    A simple, observationally-motivated model is presented for understanding how halo masses, galaxy stellar masses, and star formation rates are related, and how these relations evolve with time. The relation between halo mass and galaxy stellar mass is determined by matching the observed spatial abundance of galaxies to the expected spatial abundance of halos at multiple epochs -- i.e. more massive galaxies are assigned to more massive halos at each epoch. Halos at different epochs are connected by halo mass accretion histories estimated from N-body simulations. The halo--galaxy connection at fixed epochs in conjunction with the connection between halos across time provides a connection between observed galaxies across time. With approximations for the impact of merging and accretion on the growth of galaxies, one can then directly infer the star formation histories of galaxies as a function of stellar and halo mass. This model is tuned to match both the observed evolution of the stellar mass function and the n...

  18. Dark matter halo occupation: environment and clustering

    CERN Document Server

    Croft, Rupert; Khandai, Nishikanta; Springel, Volker; Jana, Anirban; Gardner, Jeffrey

    2011-01-01

    We use a large dark matter simulation of a LambdaCDM model to investigate the clustering and environmental dependence of the number of substructures in a halo. Focusing on redshift z=1, we find that the halo occupation distribution is sensitive at the tens of percent level to the surrounding density and to a lesser extent to asymmetry of the surrounding density distribution. We compute the autocorrelation function of halos as a function of occupation, building on the finding of Wechsler et al. (2006) and Gao and White (2007) that halos (at fixed mass) with more substructure are more clustered. We compute the relative bias as a function of occupation number at fixed mass, finding a strong relationship. At fixed mass, halos in the top 5% of occupation can have an autocorrelation function ~ 1.5-2 times higher than the mean. We also compute the bias as a function of halo mass, for fixed halo occupation. We find that for group and cluster sized halos, when the number of subhalos is held fixed, there is a strong an...

  19. Constrainig the mass-concentration relation through weak lensing peak function

    CERN Document Server

    Mainini, Roberto

    2014-01-01

    Halo masses and concentrations have been studied extensively, by means of N-body simulations as well as observationally, during the last decade. Nevertheless, the exact form of the mass-concentration relation is still widely debated. One of the most promising method to estimate masses and concentrations relies on gravitational lensing from massive halos. Here we investigate the impact of the mass-concentration relation on halo peak abundance in weak lensing shear maps relying on the aperture mass method for peak detections. After providing a prescription to take into account the concentration dispersion (always neglected in previous works) in peak number counts predictions, we assess their power to constrain the mass-concentration relation by means of Fisher matrix technique. We find that, when combined with different cosmological probes, peak statistics information from near-future weak lensing surveys provides an interesting and complementary alternative method to lessen the long standing controversy about ...

  20. Near-Infrared Properties of Moderate-Redshift Galaxy Clusters: Halo Occupation Number, Mass-to-Light Ratios and Omega(M)

    Energy Technology Data Exchange (ETDEWEB)

    Muzzin, Adam; Yee, H.K.C.; /Toronto U., Astron. Dept.; Hall, Patrick B.; /York U., Canada; Lin, Huan; /Fermilab

    2007-03-01

    Using K-band imaging for 15 of the Canadian Network for Observational Cosmology (CNOC1) clusters we examine the near-infrared properties of moderate-redshift (0.19 < z < 0.55) galaxy clusters. We find that the number of K-band selected cluster galaxies within R{sub 500} (the Halo Occupation Number, HON) is well-correlated with the cluster dynamical mass (M{sub 500}) and X-ray Temperature (T{sub x}); however, the intrinsic scatter in these scaling relations is 37% and 46% respectively. Comparison with clusters in the local universe shows that the HON-M{sub 500} relation does not evolve significantly between z = 0 and z {approx} 0.3. This suggests that if dark matter halos are disrupted or undergo significant tidal-stripping in high-density regions as seen in numerical simulations, the stellar mass within the halos is tightly bound, and not removed during the process. The total K-band cluster light (L{sub 200},K) and K-band selected richness (parameterized by B{sub gc,K}) are also correlated with both the cluster T{sub x} and M{sub 200}. The total (intrinsic) scatter in the L{sub 200,K}-M{sub 200} and B{sub gc,K}-M{sub 200} relations are 43%(31%) and 35%(18%) respectively and indicates that for massive clusters both L{sub 200,K} and B{sub gc,K} can predict M{sub 200} with similar accuracy as T{sub x}, L{sub x} or optical richness (B{sub gc}). Examination of the mass-to-light ratios of the clusters shows that similar to local clusters, the K-band mass-to-light ratio is an increasing function of halo mass. Using the K-band mass-to-light ratios of the clusters, we apply the Oort technique and find {Omega}{sub m,0} = 0.22 {+-} 0.02, which agrees well with recent combined concordance cosmology parameters, but, similar to previous cluster studies, is on the low-density end of preferred values.

  1. THE ORIGIN AND DISTRIBUTION OF COLD GAS IN THE HALO OF A MILKY-WAY-MASS GALAXY

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, Ximena; Joung, M. Ryan; Putman, Mary E. [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States)

    2012-04-20

    We analyze an adaptive mesh refinement hydrodynamic cosmological simulation of a Milky-Way-sized galaxy to study the cold gas in the halo. H I observations of the Milky Way and other nearby spirals have revealed the presence of such gas in the form of clouds and other extended structures, which indicates ongoing accretion. We use a high-resolution simulation (136-272 pc throughout) to study the distribution of cold gas in the halo, compare it with observations, and examine its origin. The amount ({approx}10{sup 8} M{sub Sun} in H I), covering fraction, and spatial distribution of the cold halo gas around the simulated galaxy at z = 0 are consistent with existing observations. At z = 0, the H I mass accretion rate onto the disk is 0.2 M{sub Sun} yr{sup -1}. We track the histories of the 20 satellites that are detected in H I in the redshift interval 0.5 > z > 0 and find that most of them are losing gas, with a median mass-loss rate per satellite of 3.1 Multiplication-Sign 10{sup -3} M{sub Sun} yr{sup -1}. This stripped gas is a significant component of the H I gas seen in the simulation. In addition, we see filamentary material coming into the halo from the intergalactic medium at all redshifts. Most of this gas does not make it directly to the disk, but part of the gas in these structures is able to cool and form clouds. The metallicity of the gas allows us to distinguish between filamentary flows and satellite gas. We find that the former accounts for at least 25%-75% of the cold gas in the halo seen at any redshift analyzed here. Placing constraints on cloud formation mechanisms allows us to better understand how galaxies accrete gas and fuel star formation at z = 0.

  2. Comparison of Asymmetric and Ice-cream Cone Models for Halo Coronal Mass Ejections

    Science.gov (United States)

    Na, H.; Moon, Y.

    2011-12-01

    Halo coronal mass ejections (HCMEs) are major cause of the geomagnetic storms. To minimize the projection effect by coronagraph observation, several cone models have been suggested: an ice-cream cone model, an asymmetric cone model etc. These models allow us to determine the three dimensional parameters of HCMEs such as radial speed, angular width, and the angle between sky plane and central axis of the cone. In this study, we compare these parameters obtained from different models using 48 well-observed HCMEs from 2001 to 2002. And we obtain the root mean square error (RMS error) between measured projection speeds and calculated projection speeds for both cone models. As a result, we find that the radial speeds obtained from the models are well correlated with each other (R = 0.86), and the correlation coefficient of angular width is 0.6. The correlation coefficient of the angle between sky plane and central axis of the cone is 0.31, which is much smaller than expected. The reason may be due to the fact that the source locations of the asymmetric cone model are distributed near the center, while those of the ice-cream cone model are located in a wide range. The average RMS error of the asymmetric cone model (85.6km/s) is slightly smaller than that of the ice-cream cone model (87.8km/s).

  3. The clustering of Lyman alpha emitters at z=7: implications for reionization and host halo masses

    CERN Document Server

    Sobacchi, Emanuele

    2015-01-01

    The Ly$\\alpha$ line of high-redshift galaxies has emerged as a powerful probe of both early galaxy evolution and the epoch of reionization (EoR). Motivated by the upcoming wide-field survey with the Subaru Hyper Supreme-Cam (HSC), we study the angular correlation function (ACF) of narrow-band selected, $z\\approx7$ LAEs. The clustering of LAEs is determined by both: (i) their typical host halo masses, $\\bar{M}_{\\rm h}$; (ii) the absorption due to a patchy EoR, characterized by an average neutral fraction of the IGM, $\\bar{x}_{\\rm HI}$. We bracket the allowed LAE ACF by exploring extreme scenarios for both the intrinsic Ly$\\alpha$ emission and the morphology of cosmic ionized patches in physical EoR models. Current LAE ACF measurements imply that the Universe is mostly ionized at $z\\approx7$, with $\\bar{x}_{\\rm HI}\\lesssim0.5$ (1-$\\sigma$) even for an extremely conservative model of intrinsic emission. The upcoming Ultra Deep campaign with the HSC could improve on these constraints by tens of percent, or $\\bar{...

  4. Tracing Galaxy Formation with Stellar Halos. II. Relating Substructure in Phase and Abundance Space to Accretion Histories

    Science.gov (United States)

    Johnston, Kathryn V.; Bullock, James S.; Sharma, Sanjib; Font, Andreea; Robertson, Brant E.; Leitner, Samuel N.

    2008-12-01

    This paper explores the mapping between the observable properties of a stellar halo in phase and abundance space and the parent galaxy's accretion history in terms of the characteristic epoch of accretion and mass and orbits of progenitor objects. The study utilizes a suite of 11 stellar halo models constructed within the context of a standard ΛCDM cosmology. The results demonstrate that coordinate-space studies are sensitive to the recent (0-8 Gyr ago) merger histories of galaxies (this timescale corresponds to the last few percent to tens of percent of mass accretion for a Milky Way-type galaxy). Specifically, the frequency, sky coverage, and fraction of stars in substructures in the stellar halo as a function of surface brightness are indicators of the importance of recent merging and of the luminosity function of infalling dwarfs. The morphology of features serves as a guide to the orbital distribution of those dwarfs. Constraints on the earlier merger history (>8 Gyr ago) can be gleaned from the abundance patterns in halo stars: within our models, dramatic differences in the dominant epoch of accretion or luminosity function of progenitor objects leave clear signatures in the [α/Fe] and [Fe/H] distributions of the stellar halo; halos dominated by very early accretion have higher average [α/Fe], while those dominated by high-luminosity satellites have higher [Fe/H]. This insight can be applied to reconstruct much about the merger histories of nearby galaxies from current and future data sets.

  5. Building Halos by Digesting Satellites

    Science.gov (United States)

    Kohler, Susanna

    2016-05-01

    recently.Dwarfs destroyed and accreted early on are typically low-metallicity as would be expected, since metallicity was lower in the early universe. Dwarfs accreted later in the simulation are typically higher metallicity. So host halos with recent accretion events are not only likely to have accreted more stellar mass, but also probably higher-metallicity stars.Though ultra-faint, low-mass dwarfs have lower average metallicities than the larger classical dwarfs, classical dwarfs contribute more of the very metal-poor stars accreted by host halos (40-80%, compared to the 2-5% from ultra-faint dwarfs).Halos that have relatively quiescent accretion histories tend to have lower-mass surviving dwarfs today.A Transient Fossil?This last point has interesting implications for our own galaxy. The Milky Way is generally though to have a quiescent formation history, and yet it contains two high-mass surviving dwarfs: the Large and Small Magellanic Clouds. The authors suggest that this inconsistency could be resolved if the Milky Way is a transient fossil a halo with a quiescent formation history masked by its recent acquisition of the Large and Small Magellanic Clouds.The outcomes from this suite of simulations provide important clues for better understanding how our own galaxy and galaxies like ours have formed and evolved.CitationAlis J. Deason et al 2016 ApJ 821 5. doi:10.3847/0004-637X/821/1/5

  6. Expanded haloes, abundance matching and too-big-to-fail in the Local Group

    CERN Document Server

    Brook, Chris B

    2014-01-01

    Observed kinematical data of 40 Local Group members are used to derive the dark matter halo mass of such galaxies. Haloes are selected from the theoretically expected Local Group mass function and two different density profiles are assumed, the standard NFW model and a mass dependent profile which accounts for the effects of baryons in modifying the dark matter distribution within galaxies. The resulting relations between stellar and halo mass are compared with expectations from abundance matching. Using the NFW profile, the ensemble of Local Group galaxies is generally fit in relatively low mass haloes, leaving dark many massive haloes of Mhalo>10^10Msun: this reflects the "too big to fail" problem in the Local Group and results in a Mstar-Mhalo relation that differs from abundance matching predictions. Moreover, the star formation efficiency of isolated Local Group galaxies increases with decreasing halo mass when adopting a NFW model. By contrast, using the mass dependent density profile, relatively high s...

  7. Scaling Evolution of Universal Dark-Matter Halo Density Profiles

    CERN Document Server

    Raig, A; Salvador-Solé, E

    1998-01-01

    Dark-matter halos show a universal density profile with a scaling such that less massive systems are typically denser. This mass-density relation is well described by a proportionality between the characteristic density of halos and the mean cosmic density at halo formation time. It has recently been shown that this proportionality could be the result of the following simple evolutionary picture. Halos form in major mergers with essentially the same, cosmogony-dependent, dimensionless profile, and then grow inside-outside, as a consequence of accretion. Here we verify the consistency of this picture and show that it predicts the correct zero point of the mass-density relation.

  8. Dark-matter halo mergers as a fertile environment for low-mass Population III star formation

    CERN Document Server

    Bovino, S; Grassi, T; Schleicher, D R G

    2014-01-01

    While Population III stars are typically thought to be massive, pathways towards lower-mass Pop III stars may exist when the cooling of the gas is particularly enhanced. A possible route is enhanced HD cooling during the merging of dark-matter halos. The mergers can lead to a high ionization degree catalysing the formation of HD molecules and may cool the gas down to the cosmic microwave background (CMB) temperature. In this paper, we investigate the merging of mini-halos with masses of a few 10$^5$~M$_\\odot$ and explore the feasibility of this scenario. We have performed three-dimensional cosmological hydrodynamics calculations with the ENZO code, solving the thermal and chemical evolution of the gas by employing the astrochemistry package KROME. Our results show that the HD abundance is increased by two orders of magnitude compared to the no-merging case and the halo cools down to $\\sim$60 K triggering fragmentation. Based on Jeans estimates the expected stellar masses are about 10 M$_\\odot$. Our findings s...

  9. A giant radio halo in a low-mass SZ-selected galaxy cluster: ACT-CL J0256.5+0006

    CERN Document Server

    Knowles, Kenda; Baker, Andrew J; Bond, J Richard; Cress, Catherine; Gupta, Neeraj; Hajian, Amir; Hilton, Matt; Hincks, Adam D; Hlozek, Renée; Hughes, Jack P; Lindner, Robert; Marriage, Tobias A; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael D; Reese, Erik D; Sievers, Jonathan; Sifón, Cristóbal; Srianand, Raghunathan; Wollack, Edward J

    2015-01-01

    We present the detection of a giant radio halo (GRH) in the Sunyaev-Zel'dovich (SZ)-selected merging galaxy cluster ACT-CL J0256.5+0006 ($z = 0.363$), observed with the Giant Metrewave Radio Telescope at 325 MHz and 610 MHz. We find this cluster to host a faint ($S_{610} = 5.6 \\pm 1.4$ mJy) radio halo with an angular extent of 2.6 arcmin, corresponding to 0.8 Mpc at the cluster redshift, qualifying it as a GRH. J0256 is one of the lowest-mass systems, $M_{\\rm 500,SZ} = (5.0 \\pm 1.2) \\times 10^{14} M_\\odot$, found to host a GRH. We measure the GRH at lower significance at 325 MHz ($S_{325} = 10.3 \\pm 5.3$ mJy), obtaining a spectral index measurement of $\\alpha^{610}_{325} = 1.0^{+0.7}_{-0.9}$. This result is consistent with the mean spectral index of the population of typical radio halos, $\\alpha = 1.2 \\pm 0.2$. Adopting the latter value, we determine a 1.4 GHz radio power of $P_{1.4\\text{GHz}} = (1.0 \\pm 0.3) \\times 10^{24}$ W Hz$^{-1}$, placing this cluster within the scatter of known scaling relations. Vari...

  10. The Local Group in LCDM - Shapes and masses of dark halos

    Science.gov (United States)

    Vera-Ciro, Carlos Andrés

    2013-01-01

    In dit proefschrift bestuderen we de eigenschappen van donkere materie halo's in het LCDM paradigma. Het eerste deel richt zich op de vorm van de massadistributie van dergelijke objecten. We hebben gevonden dat de vorm van ge"isoleerde Melkweg-achtige donkere materie halo's significant afwijkt van bolsymmetrie. De lokale omgeving heeft invloed op de halo's en deze worden daarbij sterk be"invloed door de manier waarop massa aangroeit. We hebben ook de structuur en de baanstructuur van de satellieten van dergelijke halo's in detail onderzocht. In het algemeen zijn deze objecten sferischer dan de halo's zelf. Ze vertonen ook duidelijke afdrukken van getijdenwerking in zowel hun geometrische vorm als in de baanstructuur. Daarna gebruiken we het aantal massieve objecten rond de Melkweg om limieten te zetten op de totale massa van de donkere materie halo van de Melkweg. De eigenschappen van de massaverdeling van de Melkweg worden verder onderzocht in het laatste hoofdstuk. Daar maken we gebruik van de Sagittarius sterstroom om de vorm van de galactische potentiaal beter te bepalen. We komen met een nieuw model dat rekening houdt met de galactische schijf en de invloed van satellietstelsels en die bovendien consistent is met het LCDM paradigma.

  11. Models of thin discs and spheroidal haloes with masses in a linear relationship: mass estimates for NGC4389 and UGC6969

    CERN Document Server

    González, Guillermo A; Reina, Jerson I

    2011-01-01

    A family of models of thin discs and spheroidal haloes with masses in a linear relationship is presented. The models are obtained by considering the gravitational potential as the superposition of two independent components, a potential generated by the thin galactic disc and a potential generated by the spheroidal halo. The models leads to an expression for the circular velocity that can be adjusted very accurately to the observed rotation curves of some specific galaxies, in such a way that the models are stable against radial and vertical perturbations. Two particular models for galaxies NGC4389 and UGC6969 are obtained by adjusting the circular velocity with data taken from the recent paper by Verheijen & Sancici (2001). The values of the halo mass, the disc mass and the total mass for these two galaxies are computed in such a way that we obtain a very narrow interval of values for these quantities. Furthermore, the values of masses here obtained are in perfect agreement with the expected order of mag...

  12. Dark matter density profiles of the halos embedding early-type galaxies: characterizing halo contraction and dark matter annihilation strength

    CERN Document Server

    Chae, Kyu-Hyun; Frieman, Joshua A; Bernardi, Mariangela

    2012-01-01

    Identifying dark matter and characterizing its distribution in the inner region of halos embedding galaxies are inter-related problems of broad importance. We devise a new procedure of determining dark matter distribution in halos. We first make a self-consistent bivariate statistical match of stellar mass and velocity dispersion with halo mass as demonstrated here for the first time. Then, selecting early-type galaxy-halo systems we perform Jeans dynamical modeling with the aid of observed statistical properties of stellar mass profiles and velocity dispersion profiles. Dark matter density profiles derived specifically using Sloan Digital Sky Survey galaxies and halos from up-to-date cosmological dissipationless simulations deviate significantly from the dissipationless profle of Navarro-Frenk-White or Einasto in terms of inner density slope and/or concentration. From these dark matter profiles we find that dark matter density is enhanced in the inner region of most early-type galactic halos providing an ind...

  13. Signature of primordial non-Gaussianity of phi^3-type in the mass function and bias of dark matter haloes

    CERN Document Server

    Desjacques, Vincent

    2009-01-01

    We explore the effect of a cubic correction gnl*phi^3 on the mass function and bias of dark matter haloes extracted from a series of large N-body simulations and compare it to theoretical predictions. Such cubic terms can be motivated in scenarios like the curvaton model, in which a large cubic correction can be produced while simultaneously keeping the quadratic fnl*phi^2 correction small. The deviation from the Gaussian halo mass function is in reasonable agreement with the theoretical predictions. The scale-dependent bias correction Delta b_kappa(k,gnl) measured from the auto- and cross-power spectrum of haloes, is similar to the correction in fnl models, but the amplitude is lower than theoretical expectations. Using the complication of LSS data in Slosar et al. (2008), we obtain for the first time a limit on gnl of -3.5*10^5 < gnl < +8.2*10^5 (at 95% CL). This limit will improve with the future LSS data by 1-2 orders of magnitude, which should test many of the scenarios of this type.

  14. Inferring Gravitational Potentials from Mass Densities in Cluster-sized Halos

    Science.gov (United States)

    Miller, Christopher J.; Stark, Alejo; Gifford, Daniel; Kern, Nicholas

    2016-05-01

    We use N-body simulations to quantify how the escape velocity in cluster-sized halos maps to the gravitational potential in a ΛCDM universe. Using spherical density-potential pairs and the Poisson equation, we find that the matter density inferred gravitational potential profile predicts the escape velocity profile to within a few percent accuracy for group and cluster-sized halos (10{}13\\lt {M}200\\lt {10}15 M {}⊙ , with respect to the critical density). The accuracy holds from just outside the core to beyond the virial radius. We show the importance of explicitly incorporating a cosmological constant when inferring the potential from the Poisson equation. We consider three density models and find that the Einasto and Gamma profiles provide a better joint estimate of the density and potential profiles than the Navarro, Frenk, and White profile, which fails to accurately represent the escape velocity. For individual halos, the 1σ scatter between the measured escape velocity and the density-inferred potential profile is small (<5%). Finally, while the sub-halos show 15% biases in their representation of the particle velocity dispersion profile, the sub-halo escape velocity profile matches the dark matter escape velocity profile to high accuracy with no evidence of velocity bias outside 0.4r 200.

  15. The COS-Halos survey: physical conditions and baryonic mass in the low-redshift circumgalactic medium

    Energy Technology Data Exchange (ETDEWEB)

    Werk, Jessica K.; Prochaska, J. Xavier; Tejos, Nicolas [UCO/Lick Observatory, University of California, Santa Cruz, CA (United States); Tumlinson, Jason; Peeples, Molly S.; Fox, Andrew J.; Thom, Christopher; Bordoloi, Rongmon [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD (United States); Tripp, Todd M.; Katz, Neal [Department of Astronomy, University of Massachusetts, Amherst, MA (United States); Lehner, Nicolas [Department of Physics and Astronomy, University of Notre Dame, South Bend, IN (United States); O' Meara, John M. [Department of Chemistry and Physics, Saint Michael' s College, Colchester, VT (United States); Ford, Amanda Brady [Astronomy Department, University of Arizona, Tucson, AZ 85721 (United States); Oppenheimer, Benjamin D. [Leiden Observatory, Leiden University, NL-2300 RA Leiden (Netherlands); Davé, Romeel [University of the Western Cape, Bellville, Cape Town 7535 (South Africa); Weinberg, David H., E-mail: jwerk@ucolick.org [Department of Astronomy, The Ohio State University, Columbus, OH (United States)

    2014-09-01

    We analyze the physical conditions of the cool, photoionized (T ∼10{sup 4} K) circumgalactic medium (CGM) using the COS-Halos suite of gas column density measurements for 44 gaseous halos within 160 kpc of L ∼ L* galaxies at z ∼ 0.2. These data are well described by simple photoionization models, with the gas highly ionized (n {sub H} {sub II}/n {sub H} ≳ 99%) by the extragalactic ultraviolet background. Scaling by estimates for the virial radius, R {sub vir}, we show that the ionization state (tracked by the dimensionless ionization parameter, U) increases with distance from the host galaxy. The ionization parameters imply a decreasing volume density profile n {sub H} = (10{sup –4.2±0.25})(R/R {sub vir}){sup –0.8±0.3}. Our derived gas volume densities are several orders of magnitude lower than predictions from standard two-phase models with a cool medium in pressure equilibrium with a hot, coronal medium expected in virialized halos at this mass scale. Applying the ionization corrections to the H I column densities, we estimate a lower limit to the cool gas mass M{sub CGM}{sup cool}>6.5×10{sup 10} M {sub ☉} for the volume within R < R {sub vir}. Allowing for an additional warm-hot, O VI-traced phase, the CGM accounts for at least half of the baryons purported to be missing from dark matter halos at the 10{sup 12} M {sub ☉} scale.

  16. THE SPACE MOTION OF LEO I: THE MASS OF THE MILKY WAY'S DARK MATTER HALO

    Energy Technology Data Exchange (ETDEWEB)

    Boylan-Kolchin, Michael; Bullock, James S. [Center for Cosmology, Department of Physics and Astronomy, University of California, 4129 Reines Hall, Irvine, CA 92697 (United States); Sohn, Sangmo Tony; Van der Marel, Roeland P. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Besla, Gurtina, E-mail: m.bk@uci.edu [Department of Astronomy, Columbia University, New York, NY 10027 (United States)

    2013-05-10

    We combine our Hubble Space Telescope measurement of the proper motion of the Leo I dwarf spheroidal galaxy (presented in a companion paper) with the highest resolution numerical simulations of Galaxy-size dark matter halos in existence to constrain the mass of the Milky Way's dark matter halo (M{sub vir,MW}). Despite Leo I's large Galactocentric space velocity (200 km s{sup -1}) and distance (261 kpc), we show that it is extremely unlikely to be unbound if Galactic satellites are associated with dark matter substructure, as 99.9% of subhalos in the simulations are bound to their host. The observed position and velocity of Leo I strongly disfavor a low-mass Milky Way: if we assume that Leo I is the least bound of the Milky Way's classical satellites, then we find that M{sub vir,MW} > 10{sup 12} M{sub Sun} at 95% confidence for a variety of Bayesian priors on M{sub vir,MW}. In lower mass halos, it is vanishingly rare to find subhalos at 261 kpc moving as fast as Leo I. Should an additional classical satellite be found to be less bound than Leo I, this lower limit on M{sub vir,MW} would increase by 30%. Imposing a mass-weighted {Lambda}CDM prior, we find a median Milky Way virial mass of M{sub vir,MW} = 1.6 Multiplication-Sign 10{sup 12} M{sub Sun }, with a 90% confidence interval of [1.0-2.4] Multiplication-Sign 10{sup 12} M{sub Sun }. We also confirm a strong correlation between subhalo infall time and orbital energy in the simulations and show that proper motions can aid significantly in interpreting the infall times and orbital histories of satellites.

  17. On the Stability of Satellite Planes I: Effects of Mass, Velocity, Halo Shape and Alignment

    CERN Document Server

    Fernando, Nuwanthika; Guglielmo, Magda; Lewis, Geraint F; Ibata, Rodrigo A; Power, Chris

    2016-01-01

    The recently discovered vast thin plane of dwarf satellites orbiting the Andromeda Galaxy (M31) adds to the mystery of the small scale distribution of the Local Group's galaxy population. Such well defined planar structures are apparently rare occurrences in cold dark matter cosmological simulations, and we lack a coherent explanation of their formation and existence. In this paper, we explore the long-term survivability of thin planes of dwarfs in galactic halos, focusing, in particular, on systems mimicking the observed Andromeda distribution. The key results show that, in general, planes of dwarf galaxies are fragile, sensitive to the shape of the dark matter halo and other perturbing effects. In fact, long lived planes of satellites only exist in polar orbits in spherical dark matter halos, presenting a challenge to the observed Andromeda plane which is significantly tilted with respect to the optical disk. Our conclusion is that, in standard cosmological models, planes of satellites are generally short l...

  18. The dependence on environment of Cold Dark Matter Halo properties

    CERN Document Server

    Avila-Reese, V; Gottlöber, S; Firmani, C; Maulbetsch, C

    2005-01-01

    High-resolution LCDM cosmological N-body simulations are used to study the properties of galaxy-size dark halos in different environments (cluster, void, and "field"). Halos in clusters and their surroundings have a median spin parameter ~1.3 times lower, and tend to be more spherical and to have less aligned internal angular momentum than halos in voids and the field. For halos in clusters the concentration parameters decrease on average with mass with a slope of ~0.1; for halos in voids these concentrations do not change with mass. For masses <5 10^11 M_sh^-1, halos in clusters are on average ~30-40% more concentrated and have ~2 times higher central densities than halos in voids. When comparing only parent halos, the differences are less pronounced but they are still significant. The Vmax-and Vrms-mass relations are shallower and more scattered for halos in clusters than in voids, and for a given Vmax or Vrms, the mass is smaller at z=1 than at z=0 in all the environments. At z=1, the differences in the...

  19. A giant radio halo in a low-mass SZ-selected galaxy cluster: ACT-CL J0256.5+0006

    Science.gov (United States)

    Knowles, K.; Intema, H. T.; Baker, A. J.; Bharadwaj, V.; Bond, J. R.; Cress, C.; Gupta, N.; Hajian, A.; Hilton, M.; Hincks, A. D.; Hlozek, R.; Hughes, J. P.; Lindner, R. R.; Marriage, T. A.; Menanteau, F.; Moodley, K.; Niemack, M. D.; Reese, E. D.; Sievers, J.; Sifón, C.; Srianand, R.; Wollack, E. J.

    2016-07-01

    We present the detection of a giant radio halo (GRH) in the Sunyaev-Zel'dovich (SZ)-selected merging galaxy cluster ACT-CL J0256.5+0006 (z = 0.363), observed with the Giant Metrewave Radio Telescope at 325 and 610 MHz. We find this cluster to host a faint (S610 = 5.6 ± 1.4 mJy) radio halo with an angular extent of 2.6 arcmin, corresponding to 0.8 Mpc at the cluster redshift, qualifying it as a GRH. J0256 is one of the lowest mass systems, M500, SZ = (5.0 ± 1.2) × 1014 M⊙, found to host a GRH. We measure the GRH at lower significance at 325 MHz (S325 = 10.3 ± 5.3 mJy), obtaining a spectral index measurement of α ^{610}_{325} = 1.0^{+0.7}_{-0.9}. This result is consistent with the mean spectral index of the population of typical radio haloes, α = 1.2 ± 0.2. Adopting the latter value, we determine a 1.4 GHz radio power of P1.4 GHz = (1.0 ± 0.3) × 1024 W Hz-1, placing this cluster within the scatter of known scaling relations. Various lines of evidence, including the intracluster medium morphology, suggest that ACT-CL J0256.5+0006 is composed of two subclusters. We determine a merger mass ratio of 7:4, and a line-of-sight velocity difference of v⊥ = 1880 ± 210 km s-1. We construct a simple merger model to infer relevant time-scales in the merger. From its location on the P1.4 GHz-LX scaling relation, we infer that we observe ACT-CL J0256.5+0006 just before first core crossing.

  20. A Parameter-free Statistical Measurement of Halos with Power Spectra

    CERN Document Server

    He, P; Fang, L Z; He, Ping; Feng, Long-Long; Fang, Li-Zhi

    2005-01-01

    We show that, in the halo model of large-scale structure formation, the difference between the Fourier and the DWT (discrete wavelet transform) power spectra provides a statistical measurement of the halos. This statistical quantity is free from parameters related to the shape of the mass profile and the identification scheme of halos. That is, the statistical measurement is invariant in the sense that models with reasonably defined and selected parameters of the halo models should yield the same difference of the Fourier and DWT spectra. This feature is useful to extract ensemble averaged properties of halos, which cannot be obtained with the identification of individual halo. To demonstrate this point, we show with WIGEON hydrodynamical simulation samples that the spectrum difference provides a quantitative measurement of the discrepancy of the distribution of baryonic gas from that of the underlying dark matter field within halos. We also show that the mass density profile of halos in physical space can be...

  1. Skyrme–Hartree–Fock approach to the change of level occupancy of low mass halo nuclei

    Indian Academy of Sciences (India)

    Rupayan Bhattacharya

    2000-02-01

    With a new parameterization of potential parameters which reproduces the ground state properties of shell closed nuclei fairly accurately, the role of occupancy of 21/2 level in determining the halo structures of 17O, 16N, 15C, 14B, 13Be have been investigated. The results show interesting cross over of level occupancies which may explain the increase in interaction radii.

  2. Tracing the Galactic Halo: Obtaining Bayesian mass estimates of the Galaxy in the presence of incomplete data

    Science.gov (United States)

    Eadie, Gwendolyn; Harris, William; Widrow, Lawrence; Springford, Aaron

    2016-08-01

    The mass and cumulative mass profile of the Galaxy are its most fundamental properties. Estimating these properties, however, is not a trivial problem. We rely on the kinematic information from Galactic satellites such as globular clusters and dwarf galaxies, and this data is incomplete and subject to measurement uncertainty. In particular, the complete 3D velocity vectors of objects are sometimes unavailable, and there may be selection biases due to both the distribution of objects around the Galaxy and our measurement position. On the other hand, the uncertainties of these data are fairly well understood. Thus, we would like to incorporate these uncertainties and the incomplete data into our estimate of the Milky Way's mass. The Bayesian paradigm offers a way to deal with both the missing kinematic data and measurement errors using a hierarchical model. An application of this method to the Milky Way halo mass profile, using the kinematic data for globular clusters and dwarf satellites, is shown.

  3. Dependence of GAMA galaxy halo masses on the cosmic web environment from 100 deg2 of KiDS weak lensing data

    Science.gov (United States)

    Brouwer, Margot M.; Cacciato, Marcello; Dvornik, Andrej; Eardley, Lizzie; Heymans, Catherine; Hoekstra, Henk; Kuijken, Konrad; McNaught-Roberts, Tamsyn; Sifón, Cristóbal; Viola, Massimo; Alpaslan, Mehmet; Bilicki, Maciej; Bland-Hawthorn, Joss; Brough, Sarah; Choi, Ami; Driver, Simon P.; Erben, Thomas; Grado, Aniello; Hildebrandt, Hendrik; Holwerda, Benne W.; Hopkins, Andrew M.; de Jong, Jelte T. A.; Liske, Jochen; McFarland, John; Nakajima, Reiko; Napolitano, Nicola R.; Norberg, Peder; Peacock, John A.; Radovich, Mario; Robotham, Aaron S. G.; Schneider, Peter; Sikkema, Gert; van Uitert, Edo; Verdoes Kleijn, Gijs; Valentijn, Edwin A.

    2016-11-01

    Galaxies and their dark matter haloes are part of a complex network of mass structures, collectively called the cosmic web. Using the tidal tensor prescription these structures can be classified into four cosmic environments: voids, sheets, filaments and knots. As the cosmic web may influence the formation and evolution of dark matter haloes and the galaxies they host, we aim to study the effect of these cosmic environments on the average mass of galactic haloes. To this end we measure the galaxy-galaxy lensing profile of 91 195 galaxies, within 0.039 < z < 0.263, from the spectroscopic Galaxy And Mass Assembly survey, using {˜ }100 ° ^2 of overlapping data from the Kilo-Degree Survey. In each of the four cosmic environments we model the contributions from group centrals, satellites and neighbouring groups to the stacked galaxy-galaxy lensing profiles. After correcting the lens samples for differences in the stellar mass distribution, we find no dependence of the average halo mass of central galaxies on their cosmic environment. We do find a significant increase in the average contribution of neighbouring groups to the lensing profile in increasingly dense cosmic environments. We show, however, that the observed effect can be entirely attributed to the galaxy density at much smaller scales (within 4 h-1 Mpc), which is correlated with the density of the cosmic environments. Within our current uncertainties we find no direct dependence of galaxy halo mass on their cosmic environment.

  4. Measuring the Halo Mass of z=3 Damped Ly-alpha Absorbers from the Absorber-Galaxy Cross-correlation

    CERN Document Server

    Bouche, N; Weinberg, D H; Katz, N; Davé, R; Lowenthal, J D; Bouche, Nicolas; Gardner, Jeffrey P.; Weinberg, David H.; Katz, Neal; Dave, Romeel; Lowenthal, James D.

    2005-01-01

    [Abridged] We test the reliability of a method to measure the mean halo mass of Damped Ly-alpha absorbers (DLAs). The method is based on measuring the ratio of the cross-correlation between DLAs and galaxies to the auto-correlation of the galaxies themselves ($w_{\\rm dg}/w_{\\rm gg}$), which is (in linear theory) the ratio of their bias factor. This is shown to be true irrespective of the galaxy redshift distribution, provided that one uses the same galaxies for the two correlation functions. The method is applicable to all redshifts. Here, we focus on z=3 DLAs and we demonstrate that the method robustly constrains the mean DLA halo mass using smoothed particle hydrodynamics (SPH) cosmological simulations. If we use the bias formalism of Mo & White (2002) with the DLA and galaxy mass distributions of these simulations, we predict a bias ratio of 0.771. Direct measurement from the simulations of $w_{\\rm dg}/w_{\\rm gg}$ st yields a ratio of 0.73+/-0.08, in excellent agreement with that prediction. Equivalent...

  5. Dwarf Dark Matter Halos

    CERN Document Server

    Colin, Pierre; Valenzuela, O; Gottlöber, S

    2003-01-01

    We use N-body simulations to study properties of dwarf halos with virial masses in the range 10^7-10^9 Msun/h. Unlike recent reported results, we find that the density profiles of relaxed dwarf halos are well fitted by the NFW profile and do not have cores. We estimate the distribution of concentrations for halos in mass range that covers six orders of magnitude from 10^7 Msun/h to 10^13 Msun/h, and find that the data are well reproduced by the model of Bullock et al. (2001). We predict that present-day isolated dwarf halos should have a very large median concentration of ~ 35. For halos with masses that range from 4.6 x 10^9 Msun/h to 10^13 Msun/h we measure the subhalo circular velocity function and find that they are similar when normalized to the circular velocity of the parent halo. We compute the halo mass function and the halo spin parameter distribution and find that the former is very well reproduced by the Sheth and Tormen model while the latter is well fitted by a lognormal distribution with lambda...

  6. A statistical investigation of the mass discrepancy-acceleration relation

    CERN Document Server

    Desmond, Harry

    2016-01-01

    We use the mass discrepancy-acceleration relation (the correlation between the ratio of dark-to-visible mass and acceleration in galaxies; MDAR) to test the galaxy-halo connection. We analyse the MDAR using a set of 14 statistics which quantify its four most important features: its shape, its scatter, the presence of a "characteristic acceleration scale," and the correlation of its residuals with other galaxy properties. We construct an empirical framework for the galaxy-halo connection in $\\Lambda$CDM to generate predictions for these statistics, starting with conventional correlations (halo abundance matching; AM) and introducing more where required. Comparing to the SPARC data (Lelli, McGaugh & Schombert 2016), we find: 1) The approximate shape of the MDAR is readily reproduced by AM, and there is no evidence that the acceleration at which dark matter becomes negligible has less spread in the data than in AM mocks; 2) Even under conservative assumptions, AM significantly overpredicts the scatter in the...

  7. Numerical Simulations in Cosmology; 3, Dark Matter Halos

    CERN Document Server

    Klypin, A A

    2000-01-01

    Properties of dark matter halos are reviewed. Taken from different publications, we present results on (1) the mass and velocity functions, (2) density and velocity profiles, and (3) concentration of halos. In the range of radii r=(0.005-1)rvir the density profile for a quiet isolated halo is very accurately approximated by a fit suggested by Moore etal (1997): rho=1/x^1.5(1+x^1.5), where x=r/rs and rs is a characteristic radius. The fit suggested by Navarro et al (1995) rho= 1/x(1+x)^2, also gives a very satisfactory approximation with relative errors of about 10% for radii not smaller than 1% of the virial radius. The mass function of z=0 halos with mass below 10^{13}Msun/h is approximated by a power law with slope alpha =-1.85. The slope increases with the redshift. The velocity function of halos with Vmax< 500km/s is also a power law with the slope beta= -3.8-4. The power-law extends to halos at least down to 10km/s. It is also valid for halos inside larger virialized halos. The concentration of halos ...

  8. Halo occupation distribution of massive galaxies since z= 1

    Science.gov (United States)

    Matsuoka, Y.; Masaki, S.; Kawara, K.; Sugiyama, N.

    2011-01-01

    We present a clustering analysis of ˜60 000 massive (stellar mass M★ > 1011 M⊙) galaxies out to z= 1 drawn from 55.2 deg2 of the UKIRT Infrared Deep Sky Survey (UKIDSS) and the Sloan Digital Sky Survey (SDSS) II Supernova Survey. Strong clustering is detected for all the subsamples of massive galaxies characterized by different stellar masses (M★= 1011.0-11.5 M⊙, 1011.5-12.0 M⊙) or rest-frame colours (blue: U-V 1.0). We find that more mature (more massive or redder) galaxies are more clustered, which implies that the more mature galaxies have started stellar-mass assembly earlier within the highly biased region where the structure formation has also started earlier. By means of halo occupation distribution (HOD) models fitted to the observed angular correlation function, we infer the properties of the underlying host dark haloes. We find that the estimated bias factors and host halo masses are systematically larger for galaxies with larger stellar masses, which is consistent with the general agreement that the capability of hosting massive galaxies depends strongly on halo mass. The estimated effective halo masses are ˜1014 M⊙, which gives the stellar-mass to halo-mass ratios of ˜0.003. The observed evolution of bias factors indicates rapid evolution of spatial distributions of cold dark matter relative to those traced by the massive galaxies, while the transition of host halo masses might imply that the fractional mass growth rate of haloes is less than those of stellar systems. The inferred halo masses and high fractions of central galaxies indicate that the massive galaxies in the current sample are possibly equivalent to central galaxies of galaxy clusters.

  9. Linking galaxies to dark matter haloes at $z\\sim1$ : dependence of galaxy clustering on stellar mass and specific star formation rate

    CERN Document Server

    Kim, Jae-Woo; Lee, Seong-Kook; Edge, Alastair C; Wake, David A; Merson, Alexander I; Jeon, Yiseul

    2015-01-01

    We study the dependence of angular two-point correlation functions on stellar mass ($M_{*}$) and specific star formation rate (sSFR) of $M_{*}>10^{10}M_{\\odot}$ galaxies at $z\\sim1$. The data from UKIDSS DXS and CFHTLS covering 8.2 deg$^{2}$ sample scales larger than 100 $h^{-1}$Mpc at $z\\sim1$, allowing us to investigate the correlation between clustering, $M_{*}$, and star formation through halo modeling. Based on halo occupation distributions (HODs) of $M_{*}$ threshold samples, we derive HODs for $M_{*}$ binned galaxies, and then calculate the $M_{*}/M_{\\rm halo}$ ratio. The ratio for central galaxies shows a peak at $M_{\\rm halo}\\sim10^{12}h^{-1}M_{\\odot}$, and satellites predominantly contribute to the total stellar mass in cluster environments with $M_{*}/M_{\\rm halo}$ values of 0.01--0.02. Using star-forming galaxies split by sSFR, we find that main sequence galaxies ($\\rm log\\,sSFR/yr^{-1}\\sim-9$) are mainly central galaxies in $\\sim10^{12.5} h^{-1}M_{\\odot}$ haloes with the lowest clustering amplitu...

  10. The low-mass end of the baryonic Tully-Fisher relation

    CERN Document Server

    Sales, Laura V; Oman, Kyle; Fattahi, Azadeh; Ferrero, Ismael; Abadi, Mario G; Bower, Richard; Crain, Robert A; Frenk, Carlos S; Sawala, Till; Schaller, Matthieu; Schaye, Joop; Theuns, Tom; White, Simon D M

    2016-01-01

    The scaling of disk galaxy rotation velocity with baryonic mass (the "Baryonic Tully-Fisher" relation, BTF) has long confounded galaxy formation models. It is steeper than the M ~ V^3 scaling relating halo virial masses and circular velocities and its zero point implies that galaxies comprise a very small fraction of available baryons. Such low galaxy formation efficiencies may in principle be explained by winds driven by evolving stars, but the tightness of the BTF relation argues against the substantial scatter expected from such vigorous feedback mechanism. We use the APOSTLE/EAGLE simulations to show that the BTF relation is well reproduced in LCDM simulations that match the size and number of galaxies as a function of stellar mass. In such models, galaxy rotation velocities are proportional to halo virial velocity and the steep velocity-mass dependence results from the decline in galaxy formation efficiency with decreasing halo mass needed to reconcile the CDM halo mass function with the galaxy luminosit...

  11. Kinematics of the Stellar Halo and the Mass Distribution of the Milky Way Using Blue Horizontal Branch Stars

    Science.gov (United States)

    Kafle, Prajwal R.; Sharma, Sanjib; Lewis, Geraint F.; Bland-Hawthorn, Joss

    2012-12-01

    Here, we present a kinematic study of the Galactic halo out to a radius of ~60 kpc, using 4664 blue horizontal branch stars selected from the SDSS/SEGUE survey to determine key dynamical properties. Using a maximum likelihood analysis, we determine the velocity dispersion profiles in spherical coordinates (σ r , σθ, σphi) and the anisotropy profile (β). The radial velocity dispersion profile (σ r ) is measured out to a galactocentric radius of r ~ 60 kpc, but due to the lack of proper-motion information, σθ, σphi, and β could only be derived directly out to r ~ 25 kpc. From a starting value of β ≈ 0.5 in the inner parts (9 Jeans equation, we compute the stellar rotation curve (v circ) of the Galaxy out to r ~ 25 kpc. The mass of the Galaxy within r <~ 25 kpc is determined to be 2.1 × 1011 M ⊙, and with a three-component fit to v circ(r), we determine the virial mass of the Milky Way dark matter halo to be M vir = 0.9+0.4 -0.3 × 1012 M ⊙ (R vir = 249+34 -31 kpc).

  12. KINEMATICS OF THE STELLAR HALO AND THE MASS DISTRIBUTION OF THE MILKY WAY USING BLUE HORIZONTAL BRANCH STARS

    Energy Technology Data Exchange (ETDEWEB)

    Kafle, Prajwal R.; Sharma, Sanjib; Lewis, Geraint F.; Bland-Hawthorn, Joss, E-mail: p.kafle@physics.usyd.edu.au [Sydney Institute for Astronomy, School of Physics, A28, University of Sydney, NSW 2006 (Australia)

    2012-12-20

    Here, we present a kinematic study of the Galactic halo out to a radius of {approx}60 kpc, using 4664 blue horizontal branch stars selected from the SDSS/SEGUE survey to determine key dynamical properties. Using a maximum likelihood analysis, we determine the velocity dispersion profiles in spherical coordinates ({sigma}{sub r}, {sigma}{sub {theta}}, {sigma}{sub {phi}}) and the anisotropy profile ({beta}). The radial velocity dispersion profile ({sigma}{sub r}) is measured out to a galactocentric radius of r {approx} 60 kpc, but due to the lack of proper-motion information, {sigma}{sub {theta}}, {sigma}{sub {phi}}, and {beta} could only be derived directly out to r {approx} 25 kpc. From a starting value of {beta} Almost-Equal-To 0.5 in the inner parts (9 < r/kpc < 12), the profile falls sharply in the range r Almost-Equal-To 13-18 kpc, with a minimum value of {beta} = -1.2 at r = 17 kpc, rising sharply at larger radius. In the outer parts, in the range 25 < r/kpc < 56, we predict the profile to be roughly constant with a value of {beta} Almost-Equal-To 0.5. The newly discovered kinematic anomalies are shown not to arise from halo substructures. We also studied the anisotropy profile of simulated stellar halos formed purely by accretion and found that they cannot reproduce the sharp dip seen in the data. From the Jeans equation, we compute the stellar rotation curve (v{sub circ}) of the Galaxy out to r {approx} 25 kpc. The mass of the Galaxy within r {approx}< 25 kpc is determined to be 2.1 Multiplication-Sign 10{sup 11} M{sub Sun }, and with a three-component fit to v{sub circ}(r), we determine the virial mass of the Milky Way dark matter halo to be M{sub vir} = 0.9{sup +0.4}{sub -0.3} Multiplication-Sign 10{sup 12} M{sub Sun} (R{sub vir} = 249{sup +34}{sub -31} kpc).

  13. The statistics of Λ CDM halo concentrations

    Science.gov (United States)

    Neto, Angelo F.; Gao, Liang; Bett, Philip; Cole, Shaun; Navarro, Julio F.; Frenk, Carlos S.; White, Simon D. M.; Springel, Volker; Jenkins, Adrian

    2007-11-01

    We use the Millennium Simulation (MS) to study the statistics of Λ cold dark matter (ΛCDM) halo concentrations at z = 0. Our results confirm that the average halo concentration declines monotonically with mass; the concentration-mass relation is well fitted by a power law over three decades in mass, up to the most massive objects that form in a ΛCDM universe (~ 1015h-1Msolar). This is in clear disagreement with the predictions of the model proposed by Bullock et al. for these rare objects, and agrees better with the original predictions of Navarro, Frenk & White. The large volume surveyed, together with the unprecedented numerical resolution of the MS, allows us to estimate with confidence the distribution of concentrations and, consequently, the abundance of systems with unusual properties. About one in a hundred cluster haloes (M200 >~ 3 × 1014h-1Msolar) have concentrations exceeding c200 = 7.5, a result that may be useful in interpreting the likelihood of unusually strong massive gravitational lenses, such as Abell 1689, in the ΛCDM cosmogony. A similar fraction of about 1 per cent of galaxy-sized haloes (M200 ~ 1012h-1Msolar) have c200 < 4.5 and this could be relevant to models that attempt to reconcile the ΛCDM cosmology with rotation curves of low surface brightness galaxies by appealing to haloes of unexpectedly low concentration. We find that halo concentrations are independent of spin once haloes manifestly out of equilibrium have been removed from the sample. Compared to their relaxed brethren, the concentrations of out-of-equilibrium haloes tend to be lower and have more scatter, while their spins tend to be higher. A number of previously noted trends within the halo population are induced primarily by these properties of unrelaxed systems. Finally, we compare the result of predicting halo concentrations using the mass assembly history of the main progenitor with predictions based on simple arguments regarding the assembly time of all progenitors

  14. Evolution of the atomic and molecular gas content of galaxies in dark matter haloes

    NARCIS (Netherlands)

    Popping, Gergö; Behroozi, Peter S.; Peeples, Molly S.

    2015-01-01

    We present a semi-empirical model to infer the atomic and molecular hydrogen content of galaxies as a function of halo mass and time. Our model combines the star formation rate (SFR)-halo mass-redshift relation (constrained by galaxy abundances) with inverted SFR-surface density relations to infer g

  15. The Concentration Dependence of the Galaxy-Halo Connection

    CERN Document Server

    Lehmann, Benjamin V; Becker, Matthew R; Skillman, Samuel W; Wechsler, Risa H

    2015-01-01

    Empirical methods for connecting galaxies to their dark matter halos have become essential in interpreting measurements of the spatial statistics of galaxies. Among the most successful of these methods is the technique of subhalo abundance matching, which has to date been used to associate galaxy properties with a small set of halo properties. We generalize this set of halo properties to allow variable dependence on halo concentration, and parameterize the degree of concentration dependence with a single parameter. This parameter provides a smooth interpolation between abundance matching to peak halo mass and to peak halo circular velocity. We characterize the influence of this parameter on two-point clustering, the satellite fraction, and the degree of galaxy assembly bias. We also evaluate the degeneracies between the concentration dependence and the scatter in the abundance matching relation. We show that low redshift clustering measurements from SDSS prefer a moderate amount of concentration dependence --...

  16. On the physics of radio haloes in galaxy clusters: scaling relations and luminosity functions

    NARCIS (Netherlands)

    Zandanel, F.; Pfrommer, C.; Prada, F.

    2014-01-01

    The underlying physics of giant and mini radio haloes in galaxy clusters is still an open question. We find that mini haloes (such as in Perseus and Ophiuchus) can be explained by radio-emitting electrons that are generated in hadronic cosmic ray (CR) interactions with protons of the intracluster me

  17. A Giant Radio Halo in a Low-Mass SZ-Selected Galaxy Cluster: ACT-CL J0256.5+0006

    Science.gov (United States)

    Knowles, K.; Intema, H. T.; Baker, A. J.; Bharadwaj, V.; Bond, J. R.; Cress, C.; Gupta, N.; Hajian, A.; Hilton, M.; Hincks, A. D.; Hlozek, R.; Hughes, J. P.; Lindner, R. R.; Marriage, T. A.; Menanteau, F.; Moodley, K.; Niemack, M. D.; Reese, E. D.; Sievers, J.; Sifon, C.; Srianand, R.; Wollack, Edward J.

    2016-01-01

    We present the detection of a giant radio halo (GRH) in the Sunyaev-Zel'dovich (SZ)-selected merging galaxy cluster ACT-CL J0256.5+0006 (zeta = 0.363), observed with the Giant Metrewave Radio Telescope at 325 MHz and 610 MHz. We find this cluster to host a faint (S(sub 610) = 5.6 +/- 1.4 mJy) radio halo with an angular extent of 2.6 arcmin, corresponding to 0.8 Mpc at the cluster redshift, qualifying it as a GRH. J0256 is one of the lowest-mass systems, M(sub 500,SZ) = (5.0 +/- 1.2) x 10(sup14) solar mass foud to host a GRH. We measure the GRH at lower significance at 325 MHz (S(sub 325) = 10.3 +/- 5.3 mJy), obtaining a spectral index measurement of alpha sup 610 sub 325 = 1.0(sup +0.7)(sub 0.9). This result is consistent with the mean spectral index of the population of typical radio halos, alpha = 1.2 +/- 0.2. Adopting the latter value, we determine a 1.4 GHz radio power of P(sub 1.4GHz) = (1.0 +/- 03) x 10(sup 24) W Hz(sup -1), placing this cluster within the scatter of known scaling relations. Various lines of evidence, including the ICM morphology, suggest that ACT-CL J0256.5+0006 is composed of two subclusters. We determine a merger mass ratio of 7:4, and a line-of-sight velocity difference of perpendicular = 1880 +/- 210 km s(sup -1). We construct a simple merger model of infer relevant time-scales in the merger. From its location on the P1.4GHz-L(sub x) scaling relation, we infer that we observe ACT-CL J0256.5+0006 just before first core crossing.

  18. Low-mass X-ray binaries in the outer halo of NGC 4472: a consequence of natal kicks?

    Science.gov (United States)

    Van Haaften, Lennart M.; Maccarone, Thomas J.; Sell, Paul; Mihos, Chris; Sand, David J.; Kundu, Arunav; Zepf, Stephen

    2017-01-01

    We present new Chandra observations of the outer halo of the giant elliptical galaxy NGC 4472 (M49) in the Virgo Cluster. The data extend to 130 kpc (28'), and have a total exposure time of 150 ks. After eliminating background active galactic nuclei and globular cluster (GC) sources, and correcting for completeness, we find that the number of field low-mass X-ray binaries (LMXBs) per unit stellar light increases significantly with galactocentric radius. The excess of field LMXBs at large galactocentric radii may be a consequence of natal kicks on neutron stars and black holes in binary systems in the inner part of the galaxy. These systems, some of which will become LMXBs, will generally move into wider galactic orbits. Since the metallicity in the halo of NGC 4472 strongly decreases towards larger galactocentric radii, the number of field LMXBs is anti-correlated with metallicity, in contrast to GCs. An alternative to natal kicks to explain the spatial distribution of field LMXBs is therefore a reversed metallicity effect.

  19. Faint Submillimeter Galaxies identified through their optical/near-infrared colours I: spatial clustering and halo masses

    CERN Document Server

    Chen, Chian-Chou; Swinbank, A M; Simpson, James M; Almaini, Omar; Conselice, Christopher J; Hartley, Will G; Mortlock, Alice; Simpson, Chris; Wilkinson, Aaron

    2016-01-01

    The properties of submillimeter galaxies (SMGs) that are fainter than the confusion limit of blank-field single-dish surveys ($S_{850} \\lesssim$ 2 mJy) are poorly constrained. Using a newly developed color selection technique, Optical-Infrared Triple Color (OIRTC), that has been shown to successfully {select} such faint SMGs, we identify a sample of 2938 OIRTC-selected galaxies, dubbed Triple Color Galaxies (TCGs), in the UKIDSS-UDS field. We show that these galaxies have a median 850 $\\mu$m flux of S$_{850} = 0.96\\pm0.04$ mJy (equivalent to a star-formation rate SFR $\\sim60-100$ M$_\\odot$ yr$^{-1}$ based on SED fitting), representing the first large sample of faint SMGs that bridges the gap between bright SMGs and normal star-forming galaxies in S$_{850}$ and $L_{\\rm IR}$. We assess the basic properties of TCGs and their relationship with other galaxy populations at $z\\sim2$. We measure the two-point autocorrelation function for this population and derive a typical halo mass of log$_{10}$(M$_{\\rm halo}$) $=1...

  20. Connecting Galaxies, Halos, and Star Formation Rates Across Cosmic Time

    Energy Technology Data Exchange (ETDEWEB)

    Conroy, Charlie; Wechsler, Risa H.

    2008-06-02

    A simple, observationally-motivated model is presented for understanding how halo masses, galaxy stellar masses, and star formation rates are related, and how these relations evolve with time. The relation between halo mass and galaxy stellar mass is determined by matching the observed spatial abundance of galaxies to the expected spatial abundance of halos at multiple epochs--i.e. more massive galaxies are assigned to more massive halos at each epoch. This 'abundance matching' technique has been shown previously to reproduce the observed luminosity- and scale-dependence of galaxy clustering over a range of epochs. Halos at different epochs are connected by halo mass accretion histories estimated from N-body simulations. The halo-galaxy connection at fixed epochs in conjunction with the connection between halos across time provides a connection between observed galaxies across time. With approximations for the impact of merging and accretion on the growth of galaxies, one can then directly infer the star formation histories of galaxies as a function of stellar and halo mass. This model is tuned to match both the observed evolution of the stellar mass function and the normalization of the observed star formation rate--stellar mass relation to z {approx} 1. The data demands, for example, that the star formation rate density is dominated by galaxies with M{sub star} {approx} 10{sup 10.0-10.5} M{sub {circle_dot}} from 0 < z < 1, and that such galaxies over these epochs reside in halos with M{sub vir} {approx} 10{sup 11.5-12.5} M{sub {circle_dot}}. The star formation rate--halo mass relation is approximately Gaussian over the range 0 < z < 1 with a mildly evolving mean and normalization. This model is then used to shed light on a number of issues, including (1) a clarification of 'downsizing', (2) the lack of a sharp characteristic halo mass at which star formation is truncated, and (3) the dominance of star formation over merging to the stellar

  1. A Lower Limit on the Halo Mass to form Supermassive Black Holes

    CERN Document Server

    Dotan, Calanit; Shaviv, Nir J

    2011-01-01

    We consider a scenario where supermassive black holes form through direct accumulation of gas at the centre of proto-galaxies. In the first stage, the accumulated gas forms a super-massive star whose core collapses when the nuclear fuel is exhausted, forming a black hole of $M_{\\rm BH} \\approx 100 M_{\\sun}$. As the black hole starts accreting, it inflates the surrounding dense gas into an almost hydrostatic self-gravitating envelope, with at least 10-100 times the mass of the hole. We find that these "quasistars" suffer extremely high rates of mass loss through winds from their envelopes, in analogy to very massive stars such as eta-Carinae. Only for envelope masses greater than 2.8 \\times 10^{5} (M_{\\rm BH}/100 M_{\\sun})^{9/11} is the envelope evaporation time-scale longer than the accretion time-scale of the black hole. This relation thus constitutes a "threshold growth line" above which quasistars can grow their internal black holes. Accretion rates can be 10 to 100 times the Eddington rate. The quasistars...

  2. The MUSIC of CLASH: Predictions on the Concentration-Mass Relation

    Science.gov (United States)

    Meneghetti, M.; Rasia, E.; Vega, J.; Merten, J.; Postman, M.; Yepes, G.; Sembolini, F.; Donahue, M.; Ettori, S.; Umetsu, K.; Balestra, I.; Bartelmann, M.; Benítez, N.; Biviano, A.; Bouwens, R.; Bradley, L.; Broadhurst, T.; Coe, D.; Czakon, N.; De Petris, M.; Ford, H.; Giocoli, C.; Gottlöber, S.; Grillo, C.; Infante, L.; Jouvel, S.; Kelson, D.; Koekemoer, A.; Lahav, O.; Lemze, D.; Medezinski, E.; Melchior, P.; Mercurio, A.; Molino, A.; Moscardini, L.; Monna, A.; Moustakas, J.; Moustakas, L. A.; Nonino, M.; Rhodes, J.; Rosati, P.; Sayers, J.; Seitz, S.; Zheng, W.; Zitrin, A.

    2014-12-01

    We present an analysis of the MUSIC-2 N-body/hydrodynamical simulations aimed at estimating the expected concentration-mass relation for the CLASH (Cluster Lensing and Supernova Survey with Hubble) cluster sample. We study nearly 1,400 halos simulated at high spatial and mass resolution. We study the shape of both their density and surface-density profiles and fit them with a variety of radial functions, including the Navarro-Frenk-White (NFW), the generalized NFW, and the Einasto density profiles. We derive concentrations and masses from these fits. We produce simulated Chandra observations of the halos, and we use them to identify objects resembling the X-ray morphologies and masses of the clusters in the CLASH X-ray-selected sample. We also derive a concentration-mass relation for strong-lensing clusters. We find that the sample of simulated halos that resembles the X-ray morphology of the CLASH clusters is composed mainly of relaxed halos, but it also contains a significant fraction of unrelaxed systems. For such a heterogeneous sample we measure an average two-dimensional concentration that is ~11% higher than is found for the full sample of simulated halos. After accounting for projection and selection effects, the average NFW concentrations of CLASH clusters are expected to be intermediate between those predicted in three dimensions for relaxed and super-relaxed halos. Matching the simulations to the individual CLASH clusters on the basis of the X-ray morphology, we expect that the NFW concentrations recovered from the lensing analysis of the CLASH clusters are in the range [3-6], with an average value of 3.87 and a standard deviation of 0.61.

  3. The music of clash: predictions on the concentration-mass relation

    Energy Technology Data Exchange (ETDEWEB)

    Meneghetti, M. [INAF, Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Rasia, E. [Physics Department, University of Michigan, 450 Church Avenue, Ann Arbor, MI 48109 (United States); Vega, J.; Yepes, G.; Sembolini, F. [Departamento de Fsica Terica, Universidad Autnoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Merten, J.; Ettori, S. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Postman, M.; Coe, D. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208 (United States); Donahue, M. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Umetsu, K.; Czakon, N. [Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, Taipei 10617, Taiwan (China); Balestra, I. [INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, I-80131 Napoli (Italy); Bartelmann, M. [Institut fur Theoretische Astrophysik, Universität Heidelberg, Zentrum für Astronomie, Philosophenweg 12, D-69120 Heidelberg (Germany); Benítez, N. [Instituto de Astrofísica de Andalucía (CSIC), E-18080 Granada (Spain); Biviano, A. [INAF/Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, I-34143 Trieste (Italy); Bouwens, R. [Leiden Observatory, Leiden University, PO Box 9513, NL-2333 Leiden (Netherlands); Bradley, L. [Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Broadhurst, T. [Department of Theoretical Physics and History of Science, University of the Basque Country UPV/EHU, PO Box 644, E-48080 Bilbao (Spain); De Petris, M. [Dipartimento di Fisica, Sapienza Universit di Roma, Piazzale Aldo Moro 5, I-00185 Roma (Italy); and others

    2014-12-10

    We present an analysis of the MUSIC-2 N-body/hydrodynamical simulations aimed at estimating the expected concentration-mass relation for the CLASH (Cluster Lensing and Supernova Survey with Hubble) cluster sample. We study nearly 1,400 halos simulated at high spatial and mass resolution. We study the shape of both their density and surface-density profiles and fit them with a variety of radial functions, including the Navarro-Frenk-White (NFW), the generalized NFW, and the Einasto density profiles. We derive concentrations and masses from these fits. We produce simulated Chandra observations of the halos, and we use them to identify objects resembling the X-ray morphologies and masses of the clusters in the CLASH X-ray-selected sample. We also derive a concentration-mass relation for strong-lensing clusters. We find that the sample of simulated halos that resembles the X-ray morphology of the CLASH clusters is composed mainly of relaxed halos, but it also contains a significant fraction of unrelaxed systems. For such a heterogeneous sample we measure an average two-dimensional concentration that is ∼11% higher than is found for the full sample of simulated halos. After accounting for projection and selection effects, the average NFW concentrations of CLASH clusters are expected to be intermediate between those predicted in three dimensions for relaxed and super-relaxed halos. Matching the simulations to the individual CLASH clusters on the basis of the X-ray morphology, we expect that the NFW concentrations recovered from the lensing analysis of the CLASH clusters are in the range [3-6], with an average value of 3.87 and a standard deviation of 0.61.

  4. The Dual Origin of Galactic Stellar Halos

    Science.gov (United States)

    Zolotov, Adi

    2011-01-01

    Accreted stellar halos are a natural consequence of galaxy formation in a Lambda-CDM Universe, and contain unique fossil records of hierarchical galaxy formation. The properties of local Milky Way halo stars, however, suggest that the Galaxy's halo is composed of at least two distinct stellar populations, each exhibiting different spatial distributions, orbits, and metallicities. This observed dichotomy is the result of the assembly history of the halo, which likely formed through a process more complex than pure hierarchical accretions. In this talk I will describe the formation of stellar halos surrounding Milky Way-massed disk galaxies simulated using high-resolution cosmological Smooth Particle Hydrodynamics + N-Body simulations. We find that two competing physical processes - accretion of dwarf galaxies and in situ star formation - contribute to the formation of every stellar halo. While the outer regions (r > 20 kpc) of the halos were assembled solely through the accretion and disruption of satellites, in situ star formation supplements accretion in the formation of inner halos. The relative contribution of each stellar population to a halo is shown to be a function of a galaxy's merging history. Galaxies with recent mergers, like M31, will host relatively few in situ stars, while galaxies with more quiescent recent histories, like the Milky Way, will likely have a larger population of such stars. We show how the chemical abundance trends ([Fe/H] vs. [alpha/Fe]) of accreted and in situ stars diverge at the high [Fe/H] end of the metallicity distribution function, and discuss how such trends can be used to study and identify the observable imprints of the Milky Way's formation history.

  5. Dependence of GAMA galaxy halo masses on the cosmic web environment from 100 square degrees of KiDS weak lensing data

    CERN Document Server

    Brouwer, Margot M; Dvornik, Andrej; Eardley, Lizzie; Heymans, Catherine; Hoekstra, Henk; Kuijken, Konrad; McNaught-Roberts, Tamsyn; Sifón, Cristóbal; Viola, Massimo; Alpaslan, Mehmet; Bilicki, Maciej; Bland-Hawthorn, Joss; Brough, Sarah; Choi, Ami; Driver, Simon P; Erben, Thomas; Grado, Aniello; Hildebrandt, Hendrik; Holwerda, Benne W; Hopkins, Andrew M; de Jong, Jelte T A; Liske, Jochen; McFarland, John; Nakajima, Reiko; Napolitano, Nicola R; Norberg, Peder; Peacock, John A; Radovich, Mario; Robotham, Aaron S G; Schneider, Peter; Sikkema, Gert; van Uitert, Edo; Kleijn, Gijs Verdoes

    2016-01-01

    Galaxies and their dark matter haloes are part of a complex network of mass structures, collectively called the cosmic web. Using the tidal tensor prescription these structures can be classified into four cosmic environments: voids, sheets, filaments and knots. As the cosmic web may influence the formation and evolution of dark matter haloes and the galaxies they host, we aim to study the effect of these cosmic environments on the average mass of galactic haloes. To this end we measure the galaxy-galaxy lensing profile of 91,195 galaxies, within 0.039 < z < 0.263, from the spectroscopic Galaxy And Mass Assembly (GAMA) survey, using ~100 square degrees of overlapping data from the Kilo-Degree Survey (KiDS). In each of the four cosmic environments we model the contributions from group centrals, satellites and neighbouring groups to the stacked galaxy-galaxy lensing profiles. After correcting the lens samples for differences in the stellar mass distribution, we find no dependence of the average halo mass o...

  6. The orbital PDF: the dynamical state of Milky Way sized haloes and the intrinsic uncertainty in the determination of their masses

    CERN Document Server

    Han, Jiaxin; Cole, Shaun; Frenk, Carlos S

    2015-01-01

    Using realistic cosmological simulations of Milky Way sized haloes, we study their dynamical state and the accuracy of inferring their mass profiles with steady-state models of dynamical tracers. We use a new method that describes the phase-space distribution of a steady-state tracer population in a spherical potential without any assumption regarding the distribution of their orbits. Applying the method to five haloes from the Aquarius $\\Lambda$CDM N-body simulation, we find that dark matter particles are an accurate tracer that enables the halo mass and concentration parameters to be recovered with an accuracy of $5\\%$. Assuming a potential profile of the NFW form does not significantly affect the fits in most cases, except for halo A whose density profile differs significantly from the NFW form, leading to a $30\\%$ bias in the dynamically fitted parameters. The existence of substructures in the dark matter tracers only affects the fits by $\\sim 1\\%$. Applying the method to mock stellar haloes generated by ...

  7. The MUSIC of CLASH: predictions on the concentration-mass relation

    CERN Document Server

    Meneghetti, M; Vega, J; Merten, J; Postman, M; Yepes, G; Sembolini, F; Donahue, M; Ettori, S; Umetsu, K; Balestra, I; Bartelmann, M; Benitez, N; Biviano, A; Bouwens, R; Bradley, L; Broadhurst, T; Coe, D; Czakon, N; De Petris, M; Ford, H; Giocoli, C; Gottloeber, S; Grillo, C; Infante, L; Jouvel, S; Kelson, D; Koekemoer, A; Lahav, O; Lemze, D; Medezinski, E; Melchior, P; Mercurio, A; Molino, A; Moscardini, L; Monna, A; Moustakas, J; Moustakas, L A; Nonino, M; Rhodes, J; Rosati, P; Sayers, J; Seitz, S; Zheng, W; Zitrin, A

    2014-01-01

    We present the results of a numerical study based on the analysis of the MUSIC-2 simulations, aimed at estimating the expected concentration-mass relation for the CLASH cluster sample. We study nearly 1400 halos simulated at high spatial and mass resolution, which were projected along many lines-of-sight each. We study the shape of both their density and surface-density profiles and fit them with a variety of radial functions, including the Navarro-Frenk-White, the generalised Navarro-Frenk-White, and the Einasto density profiles. We derive concentrations and masses from these fits and investigate their distributions as a function of redshift and halo relaxation. We use the X-ray image simulator X-MAS to produce simulated Chandra observations of the halos and we use them to identify objects resembling the X-ray morphologies and masses of the clusters in the CLASH X-ray selected sample. We also derive a concentration-mass relation for strong-lensing clusters. We find that the sample of simulated halos which re...

  8. A Universal Angular Momentum Profile for Dark Matter Halos

    Science.gov (United States)

    Liao, Shihong; Chen, Jianxiong; Chu, M.-C.

    2017-07-01

    The angular momentum distribution in dark matter halos and galaxies is a key ingredient in understanding their formation. Specifically, the internal distribution of angular momenta is closely related to the formation of disk galaxies. In this article, we use halos identified from a high-resolution simulation, the Bolshoi simulation, to study the spatial distribution of specific angular momenta, j(r,θ ). We show that by stacking halos with similar masses to increase the signal-to-noise ratio, the profile can be fitted as a simple function, j{(r,θ )={j}s{\\sin }2{(θ /{θ }s)(r/{r}s)}2/(1+r/{r}s)}4, with three free parameters, {j}s,{r}s, and {θ }s. Specifically, j s correlates with the halo mass M vir as {j}s\\propto {M}{vir}2/3, r s has a weak dependence on the halo mass as {r}s\\propto {M}{vir}0.040, and {θ }s is independent of M vir. This profile agrees with that from a rigid shell model, though its origin is unclear. Our universal specific angular momentum profile j(r,θ ) is useful in modeling the angular momenta of halos. Furthermore, by using an empirical stellar mass-halo mass relation, we can infer the average angular momentum distribution of a dark matter halo. The specific angular momentum-stellar mass relation within a halo computed from our profile is shown to share a similar shape as that from the observed disk galaxies.

  9. A Universal SFDM Halo Mass for the Andromeda and Milky Way’s dSphs?

    Science.gov (United States)

    Lora, V.

    2015-07-01

    Dwarf spheroidal galaxies are the most common type of galaxies, and are the most dark matter (DM) dominated objects in the universe. Therefore, they are ideal laboratories to test any DM model. The Bose-Einstein condensate/scalar field DM model considers that the DM is composed by spinless-ultra-light particles which can be described by a scalar field. This model is an alternative to the Λ-cold DM model. In this work I study the kinematics of the dwarf spheroidal satellite galaxies of the Milky Way and Andromeda, under the scalar field/BEC dark matter Paradigm in two limits: when the self-interacting parameter is equal to zero, and when the self-interacting parameter is \\gg 1. I find that dwarf spheroidal galaxies with very high mass-to-light ratios (M/L; higher than 100) are in better agreement with an Navarro-Frenk-White mass density profile. On the other hand, dwarf spheroidal galaxies with relatively low M/L and high luminosities are better described with the SFDM model. Such results are very encouraging to further test alternative DM models using the dynamics of dwarf galaxies as a tool.

  10. Dependence of GAMA galaxy halo masses on the cosmic web environment from 100 deg2 of KiDS weak lensing data

    NARCIS (Netherlands)

    Brouwer, Margot M.; Cacciato, Marcello; Dvornik, Andrej; Eardley, Lizzie; Heymans, Catherine; Hoekstra, Henk; Kuijken, Konrad; McNaught-Roberts, Tamsyn; Sifón, Cristóbal; Viola, Massimo; Alpaslan, Mehmet; Bilicki, Maciej; Bland-Hawthorn, Joss; Brough, Sarah; Choi, Ami; Driver, Simon P.; Erben, Thomas; Grado, Aniello; Hildebrandt, Hendrik; Holwerda, Benne W.; Hopkins, Andrew M.; de Jong, Jelte T. A.; Liske, Jochen; McFarland, John; Nakajima, Reiko; Napolitano, Nicola R.; Norberg, Peder; Peacock, John A.; Radovich, Mario; Robotham, Aaron S. G.; Schneider, Peter; Sikkema, Gert; van Uitert, Edo; Verdoes Kleijn, Gijs; Valentijn, Edwin A.

    2016-01-01

    Galaxies and their dark matter haloes are part of a complex network of mass structures, collectively called the cosmic web. Using the tidal tensor prescription these structures can be classified into four cosmic environments: voids, sheets, filaments and knots. As the cosmic web may influence the fo

  11. La abundancia de galaxias y halos de materia oscura en el universo CDM

    Science.gov (United States)

    Abadi, M. G.; Benítez-Llambay, A.; Ferrero, I.

    A long-standing puzzle of CDM cosmological model concerns to the different shape of the galaxy stellar mass function and the halo mass function on dwarf galaxy scales. Dwarf galaxies are much less numerous than halos massive enough to host them; suggesting a complex non-linear relation between the mass of a galaxy and the mass of its surrounding halo. Usually; this is reconciled by appealing to baryonic processes that can reduce the efficiency of galaxy formation in low-mass halos. Recent work applying the abundance matching technique require that virtually no dwarf galaxies form in halos with virial mass below . We use rotation curves of dwarf galaxies compiled from the literature to explore whether their total enclosed mass is consistent with these constraints. Almost one-half of the dwarfs in our sample are at odds with this restriction; they are in halos with masses substantially below . Using a cosmological simulation of the formation of the Local Group of galaxies we found that ram-pressure stripping against the cosmic web removes baryons from low-mass halos without appealing to feedback or reionization. This mechanism may help to explain the scarcity of dwarf galaxies compared with the numerous low-mass halos expected in CDM and the large diversity of star formation histories and morphologies characteristic of faint galaxies. FULL TEXT IN SPANISH

  12. The velocity shear tensor: tracer of halo alignment

    CERN Document Server

    Libeskind, Noam I; Forero-Romero, Jaime; Gottlöber, Stefan; Knebe, Alexander; Steinmetz, Matthias; Klypin, Anatoly

    2012-01-01

    The alignment of DM halos and the surrounding large scale structure (LSS) is examined in the context of the cosmic web. Halo spin, shape and the orbital angular momentum of subhaloes is investigated relative to the LSS using the eigenvectors of the velocity shear tensor evaluated on a grid with a scale of 1 Mpc/h, deep within the non-linear regime. Knots, filaments, sheets and voids are associated with regions that are collapsing along 3, 2, 1 or 0 principal directions simultaneously. Each halo is tagged with a web classification (i.e. knot halo, filament halo, etc) according to the nature of the collapse at the halo's position. The full distribution of shear eigenvalues is found to be substantially different from that tagged to haloes, indicating that the observed velocity shear is significantly biased. We find that larger mass haloes live in regions where the shear is more isotropic, namely the expansion or collapse is more spherical. A correlation is found between the halo's shape and the eigenvectors of t...

  13. The orbital PDF: the dynamical state of Milky Way sized haloes and the intrinsic uncertainty in the determination of their masses

    Science.gov (United States)

    Han, Jiaxin; Wang, Wenting; Cole, Shaun; Frenk, Carlos S.

    2016-02-01

    Using realistic cosmological simulations of Milky Way sized haloes, we study their dynamical state and the accuracy of inferring their mass profiles with steady-state models of dynamical tracers. We use a new method that describes the phase-space distribution of a steady-state tracer population in a spherical potential without any assumption regarding the distribution of their orbits. Applying the method to five haloes from the Aquarius Λ cold dark matter (ΛCDM) N-body simulation, we find that dark matter particles are an accurate tracer that enables the halo mass and concentration parameters to be recovered with an accuracy of 5 per cent. Assuming a potential profile of the Navarro, Frenk & White (NFW) form does not significantly affect the fits in most cases, except for halo A whose density profile differs significantly from the NFW form, leading to a 30 per cent bias in the dynamically fitted parameters. The existence of substructures in the dark matter tracers only affects the fits by ˜1 per cent. Applying the method to mock stellar haloes generated by a particle-tagging technique, we find the stars are farther from equilibrium than dark matter particles, yielding a systematic bias of ˜20 per cent in the inferred mass and concentration parameter. The level of systematic biases obtained from a conventional distribution function fit to stars is comparable to ours, while similar fits to dark matter tracers are significantly biased in contrast to our fits. In line with previous studies, the mass bias is much reduced near the tracer half-mass radius.

  14. The different baryonic Tully-Fisher relations at low masses

    Science.gov (United States)

    Brook, Chris B.; Santos-Santos, Isabel; Stinson, Greg

    2016-06-01

    We compare the Baryonic Tully-Fisher relation (BTFR) of simulations and observations of galaxies ranging from dwarfs to spirals, using various measures of rotational velocity Vrot. We explore the BTFR when measuring Vrot at the flat part of the rotation curve, Vflat, at the extent of H I gas, Vlast, and using 20 per cent (W20) and 50 per cent (W50) of the width of H I line profiles. We also compare with the maximum circular velocity of the parent halo, V_max^DM, within dark matter only simulations. The different BTFRs increasingly diverge as galaxy mass decreases. Using Vlast one obtains a power law over four orders of magnitude in baryonic mass, with slope similar to the observed BTFR. Measuring Vflat gives similar results as Vlast when galaxies with rising rotation curves are excluded. However, higher rotation velocities would be found for low-mass galaxies if the cold gas extended far enough for Vrot to reach a maximum. W20 gives a similar slope as Vlast but with slightly lower values of Vrot for low-mass galaxies, although this may depend on the extent of the gas in your galaxy sample. W50 bends away from these other relations towards low velocities at low masses. By contrast, V_max^DM bends towards high velocities for low-mass galaxies, as cold gas does not extend out to the radius at which haloes reach V_max^DM. Our study highlights the need for careful comparisons between observations and models: one needs to be consistent about the particular method of measuring Vrot, and precise about the radius at which velocities are measured.

  15. Breaking the degeneracy between anisotropy and mass The dark halo of the E0 galaxy NGC 6703

    CERN Document Server

    Gerhard, O E; Saglia, R P; Bender, R; Gerhard, Ortwin; Jeske, Gunther; Bender, Ralf

    1997-01-01

    (abridged) We have measured line-of-sight velocity profiles (VPs) in the E0 galaxy NGC 6703 out to 2.6 R_e. From these data we constrain the mass distribution and the anisotropy of the stellar orbits in this galaxy. We have developed a non-parametric technique to determine the DF f(E,L^2) directly from the kinematic data. From Monte Carlo tests using the spatial extent, sampling, and error bars of the NGC 6703 data we find that smooth underlying DFs can be recovered to an rms accuracy of 12%, and the anisotropy parameter beta(r) to an accuracy of 0.1, in a given potential. An asymptotically constant halo circular velocity v_0 can be determined with an accuracy of +- \\lta 50km/s. For NGC 6703 we determine the true circular velocity at 2.6 R_e to be 250 +- 40km/s at 95% c.l., corresponding to a total mass in NGC 6703 inside 78'' (13.5 h_50^-1 kpc), of 1.6-2.6 x 10^11 h_50^-1 Msun. No model without dark matter will fit the data; however, a maximum stellar mass model in which the luminous component provides nearl...

  16. Kinematics of the stellar halo and the mass distribution of the Milky Way using BHB stars

    CERN Document Server

    Kafle, Prajwal R; Lewis, Geraint F; Bland-Hawthorn, Joss

    2012-01-01

    Here we present a kinematic study of the Galactic halo out to a radius of $\\sim$ 60 kpc, using 4664 blue horizontal branch (BHB) stars selected from the SDSS/SEGUE survey, to determine key dynamical properties. Using a maximum likelihood analysis, we determine the velocity dispersion profiles in spherical coordinates ($\\sigma_{r}$, $\\sigma_{\\theta}$, $\\sigma_{\\phi}$) and the anisotropy profile ($\\beta$). The radial velocity dispersion profile ($\\sigma_{r}$) is measured out to a galactocentric radius of $r \\sim 60$ kpc, but due to the lack of proper-motion information, $\\sigma_{\\theta}$, $\\sigma_{\\phi}$ and $\\beta$ could only be derived directly out to $r \\sim25$ kpc. From a starting value of $\\beta\\approx 0.5$ in the inner parts ($9

  17. The Effect of Halo Assembly Bias on Self Calibration in Galaxy Cluster Surveys

    CERN Document Server

    Wu, Hao-Yi; Wechsler, Risa H

    2008-01-01

    Self-calibration techniques for analyzing cluster counts rely on using the abundance and the clustering amplitude of clusters to simultaneously constrain cosmological parameters and the relation between halo mass and its observable mass tracer. It was recently discovered that the clustering amplitude of halos depends not only on halo mass, but also on various secondary variables such as halo formation time and concentration; these dependences are collectively termed ``assembly bias.'' Using a modified Fisher matrix formalism, we explore whether these secondary variables have a significant impact on studying the properties of dark energy with self calibration in current (SDSS) and near future (DES, SPT, and LSST) cluster surveys. We find that for an SDSS-like survey, secondary dependences of halo bias are insignificant given the expected large statistical uncertainties in dark energy parameters. For SPT- or DES-like survey volumes, we find that the dependence of halo bias on secondary variables is not a signif...

  18. Models for the mass function and assembly histories of dark halos: an approach to inventory isolated overdense regions in random fields

    CERN Document Server

    Firmani, C

    2013-01-01

    In order to attain a statistical description of the evolution of cosmic density fluctuations in agreement with results from the numerical simulations, we introduce a probability conditional formalism (CF) based on an inventory of isolated overdense regions in a density random field. This formalism is a useful tool for describing at the same time the mass function (MF) of dark haloes, their mass aggregation histories (MAHs) and merging rates (MRs). The CF focuses on virialized regions in a self-consistent way rather than in mass elements, and it offers an economical description for a variety of random fields. Within the framework of the CF, we confirm that, for a Gaussian field, it is not possible to reproduce at the same time the MF, MAH, and MR of haloes, both for a constant and moving barrier. Then, we develop an inductive method for constraining the cumulative conditional probability from a given halo MF description, and thus, using the CF, we calculate the halo MAHs and MRs. By applying this method to the...

  19. On the Physics of Radio Halos in Galaxy Clusters: Scaling Relations and Luminosity Functions

    CERN Document Server

    Zandanel, Fabio

    2014-01-01

    The underlying physics of giant and mini radio halos in galaxy clusters is still an open question. We find that mini halos (such as in Perseus and Ophiuchus) can be explained by radio-emitting electrons that are generated in hadronic cosmic ray (CR) interactions with protons of the intracluster medium. By contrast, the hadronic model either fails to explain the extended emission of giant radio halos (as in Coma at low frequencies) or would require a flat CR profile, which can be realized through outward streaming and diffusion of CRs (in Coma and A2163 at 1.4 GHz). We suggest that a second, leptonic component could be responsible for the missing flux in the outer parts of giant halos within a new hybrid scenario and we describe its possible observational consequences. To study the hadronic emission component of the radio halo population statistically, we use a cosmological mock galaxy cluster catalog built from the MultiDark simulation. Because of the properties of CR streaming and the different scalings of t...

  20. Minimizing the Stochasticity of Halos in Large-Scale Structure Surveys

    CERN Document Server

    Hamaus, Nico; Desjacques, Vincent; Smith, Robert E; Baldauf, Tobias

    2010-01-01

    In recent work (Seljak, Hamaus and Desjacques 2009) it was found that weighting central halo galaxies by halo mass can significantly suppress their stochasticity relative to the dark matter, well below the Poisson model expectation. In this paper we extend this study with the goal of finding the optimal mass-dependent halo weighting and use $N$-body simulations to perform a general analysis of halo stochasticity and its dependence on halo mass. We investigate the stochasticity matrix, defined as $C_{ij}\\equiv$, where $\\delta_m$ is the dark matter overdensity in Fourier space, $\\delta_i$ the halo overdensity of the $i$'th halo mass bin and $b_i$ the halo bias. In contrast to the Poisson model predictions we detect non-vanishing correlations between different mass bins. We also find the diagonal terms to be sub-Poissonian for the highest mass halos. The diagonalization of this matrix results in one large and one low eigenvalue, with the remaining eigenvalues close to the Poisson prediction $1/\\bar{n}$, where $\\...

  1. First detection of a low-mass stellar halo around the young open cluster Eta Chamaeleontis

    CERN Document Server

    Murphy, Simon J; Bessell, Michael S

    2010-01-01

    We have identified several lithium-rich low-mass (0.08Mass Function deficient in low-mass objects. Candidates were selected on the basis of DENIS and 2MASS photometry, NOMAD astrometry and extensive follow-up spectroscopy.

  2. On the Structure of Hot Gas in Halos: Implications for the Lx-Tx Relation & Missing Baryons

    CERN Document Server

    Sharma, Prateek; Parrish, Ian J; Quataert, Eliot

    2012-01-01

    We present one-dimensional models of the hot gas in dark-matter halos, which both predict the existence of cool cores and explain their structure. Our models are directly applicable to semi-analytic models (SAMs) of galaxy formation. We have previously argued that filaments of cold (~10^4 K) gas condense out of the intracluster medium (ICM) in hydrostatic and thermal equilibrium when the ratio of the thermal instability timescale to the free-fall time $t_{TI}/t_{ff}$ falls below 5-10. This criterion corresponds to an upper limit on the density of the ICM and motivates a model in which a density core forms wherever $t_{TI}/t_{ff} \\lesssim 10$. Consistent with observations and numerical simulations, this model predicts larger and more tenuous cores for lower-mass halos---while the core density in a cluster may be as large as ~ 0.1 cm^{-3}, the core density in the Galactic halo should not exceed ~ 10^{-4} cm^{-3}. Our models produce a favorable match to the observational X-ray luminosity-temperature (Lx-Tx) rela...

  3. Enhanced Acoustic Emission in Relation to the Acoustic Halo Surrounding Active Region 11429

    CERN Document Server

    Hanson, Chris S; Leka, K D

    2015-01-01

    The use of acoustic holography in the high-frequency $p$-mode spectrum can resolve the source distributions of enhanced acoustic emissions within halo structures surrounding active regions. In doing so, statistical methods can then be applied to ascertain relationships with the magnetic field. This is the focus of this study. The mechanism responsible for the detected enhancement of acoustic sources around solar active regions has not yet been explained. Furthermore the relationship between the magnetic field and enhanced acoustic emission has not yet been comprehensively examined. We have used vector magnetograms from the \\Helioseismic and Magnetic Imager (HMI) on-board the Solar Dynamics Observatory (SDO) to image the magnetic-field properties in the halo. We have studied the acoustic morphology of an active region, with a complex halo and "glories," and we have linked some acoustic properties to the magnetic-field configuration. In particular, we find that acoustic sources are significantly enhanced in reg...

  4. Discovery of solar system-size halos around young stars

    Science.gov (United States)

    Beckwith, S.; Skrutskie, M. F.; Zuckerman, B.; Dyck, H. M.

    1984-01-01

    Near-infrared speckle interferometric observations of five pre-main-sequence stars reveal a core-halo structure around two of these stars: HL Tau and R Mon. The halo light distribution is shown to arise from scattered light from small circumstellar particles. Halo sizes of 320 x 200 AU (alpha x delta FWHM) and 1300 x 1300 AU are deduced for HL Tau and R Mon, respectively, and the halo light is substantially bluer than the stellar light. The minimum mass of small particles in the scattering regions is comparable to the earth's mass in HL Tau and ten times greater in R Mon. Mass loss from the stars is almost certainly insufficient to produce the halo matter. The halos probably consist of relatively slowly moving matter bound gravitationally to the stars. From the size and mass of the circumstellar matter, it appears likely that these halos are in the early stage in the formation of planet-forming disks around the young stars.

  5. Relativity, potential energy, and mass

    Science.gov (United States)

    Hecht, Eugene

    2016-11-01

    This paper is an exploration of the concept of energy, illuminated by the transformative insights of the special theory of relativity. Focusing on potential energy (PE), it will be shown that PE as presently defined is in conflict with the tenets of special relativity. Even though PE remains an indispensable theoretical device its actual physicality is questionable. Moreover its ontological status is quite different from that of both kinetic energy and mass, a significant point that is not widely appreciated. We will establish that PE is a theoretical concept as opposed to an empirical one; it is a descriptor of mass-energy without a detectable physical presence of its own. PE is a measure of energy stored, it is not the energy stored.

  6. HI Velocity Dispersions and Flaring : Disk Masses and the Shape of Dark Matter Halos

    NARCIS (Netherlands)

    van der Kruit, P. C.; O'Brien, J. C.; Freeman, K. C.; Debattista, VP; Popescu, CC

    2010-01-01

    I briefly review the use of measurements of the HI velocity dispersion and gas layer flaring in galaxy disks to determine the baryonic mass of the disks. I compare that to results from stellar dynamics. In systems with low-mass disks, flaring can also provide information on the flattening of the

  7. Some like it triaxial: the universality of dark matter halo shapes and their evolution along the cosmic time

    CERN Document Server

    Despali, Giulia; Tormen, Giuseppe

    2014-01-01

    We present a detailed analysis of dark matter halo shapes, studying how the distributions of ellipticity, prolateness and axial ratios evolve as a function of time and mass. With this purpose in mind, we analysed the results of three cosmological simulations, running an ellipsoidal halo finder to measure triaxial halo shapes. The simulations have different scales, mass limits and cosmological parameters, which allows us to ensure a good resolution and statistics in a wide mass range, and to investigate the dependence of halo properties on the cosmological model. We confirm the tendency of haloes to be prolate at all times, even if they become more triaxial going to higher redshifts. Regarding the dependence on mass, more massive haloes are also less spherical at all redshifts, since they are the most recent forming systems and so still retain memory of their original shape at the moment of collapse. We then propose a rescaling of the shape-mass relations, using the variable $\

  8. Gaseous Galaxy Halos

    CERN Document Server

    Putman, M E; Joung, M R

    2012-01-01

    Galactic halo gas traces inflowing star formation fuel and feedback from a galaxy's disk and is therefore crucial to our understanding of galaxy evolution. In this review, we summarize the multi-wavelength observational properties and origin models of Galactic and low redshift spiral galaxy halo gas. Galactic halos contain multiphase gas flows that are dominated in mass by the ionized component and extend to large radii. The densest, coldest halo gas observed in neutral hydrogen (HI) is generally closest to the disk ( 10^5.5 K) and cold mode in simulations, with the compressed material close to the disk the coldest and densest, in agreement with observations. There is evidence in halo gas observations for radiative and mechanical feedback mechanisms, including escaping photons from the disk, supernova-driven winds, and a galactic fountain. Satellite accretion also leaves behind abundant halo gas. This satellite gas interacts with the existing halo medium, and much of this gas will become part of the diffuse h...

  9. Counting Dark Sub-halos with Star Stream Gaps

    CERN Document Server

    Carlberg, Raymond G

    2012-01-01

    The Cold Dark Matter paradigm predicts vast numbers of dark matter sub-halos to be orbiting in galactic halos. The sub-halos are detectable through the gaps they create gaps in stellar streams. The gap-rate is an integral over the density of sub-halos, their mass function, velocity distribution and the dynamical age of the stream. The rate of visible gap creation is a function of the width of the stream. The available data for four streams: the NW stream of M31, the Pal~5 stream, the Orphan Stream and the Eastern Banded Structure, are compared to the LCDM predicted relation. We find a remarkably good agreement, although there remains much to be done to improve the quality of the result. The narrower streams require that there is a total population of order 10^5 sub-halos above 10^5 M_sun to create the gaps.

  10. Resonant Trapping in the Galactic Disc and Halo and its Relation with Moving Groups

    CERN Document Server

    Moreno, Edmundo; Schuster, William

    2015-01-01

    With the use of a detailed Milky Way nonaxisymmetric potential, observationally and dynamically constrained, the e?ects of the bar and the spiral arms in the Galaxy are studied in the disc and in the stellar halo. Especially the trapping of stars in the disc and Galactic halo by resonances on the Galactic plane, induced by the Galactic bar, has been analysed in detail. To this purpose, a new method is presented to delineate the trapping regions using empirical diagrams of some orbital properties obtained in the Galactic potential. In these diagrams we plot in the inertial Galactic frame a characteristic orbital energy versus a characteristic orbital angular momentum, or versus the orbital Jacobi constant in the reference frame of the bar, when this is the only nonaxisymmetric component in the Galactic potential. With these diagrams some trapping regions are obtained in the disc and halo using a sample of disc stars and halo stars in the solar neighbourhood. We compute several families of periodic orbits on th...

  11. Coronal Mass Ejections, Interplanetary Shocks In Relation With Forbush Decreases Associated With Intense Geomagnetic Storms

    Science.gov (United States)

    Verma, P. L.; Patel, Nand Kumar; Prajapati, Mateswari

    2014-05-01

    Coronal mass ejections (CMEs} are the most energetic solar events in which large amount of solar plasma materials are ejected from the sun into heliosphere, causing major disturbances in solar wind plasma, Interplanetary shocks, Forbush decrease(Fds) in cosmic ray intensity and geomagnetic storms. We have studied Forbush decreases associated with intense geomagnetic storms observed at Oulu super neutron monitor, during the period of May 1998-Dec 2006 with coronal mass ejections (CMEs), X-ray solar flares and interplanetary shocks. We have found that all the (100%) Forbush decreases associated with intense geomagnetic storms are associated with halo and partial halo coronal mass ejections (CMEs). The association rate between halo and partial halo coronal mass ejections are found 96.00%and 04.00% respectively. Most of the Forbush decreases associated with intense geomagnetic storms (96.29%) are associated with X-ray solar flares of different categories . The association rates for X-Class, M-Class, and C- Class X -ray solar flares are found 34.62%, 50.00% and 15.38% respectively .Further we have concluded that majority of the Forbush decrease associated with intense geomagnetic storms are related to interplanetary shocks (92.30 %) and the related shocks are forward shocks. We have found positive co-relation with co-relation co-efficient .7025 between magnitudes of Forbush decreases associated with intense geomagnetic storms and speed of associated coronal mass ejections. Positive co-relation with co-relation co-efficient 0.48 has also been found between magnitudes of intense geomagnetic storms and speed of associated coronal mass ejections.

  12. Cosmic Web Type Dependence of Halo Clustering

    CERN Document Server

    Fisher, J D

    2016-01-01

    We use the Millennium simulation to show that halo clustering varies significantly with cosmic web type. Halos are classified as node, filament, sheet and void halos based on the eigenvalue decomposition of the velocity shear tensor. This classification allows us to examine the clustering of halos as a function of web type in different mass ranges. We find that node halos show positive bias for all mass ranges probed, even for 10^11 and 10^12 Msun/h mass bins where the clustering of the entire halo sample is anti-biased. In all mass bins filament halos show negligible bias, whereas void and sheet halos are anti-biased. The zero-crossing of the void and sheet correlation functions occur at much smaller scales Mpc/h when compared to 5the same correlation functions for the entire halo sample. Our results suggest that the mass dependence of halo clustering is rooted in the composition of web types in the mass bin. The substantial fraction of node type halos for halo masses 2 x 10^13 Msun/h leads to positive bias....

  13. Radiative feedback and the low efficiency of galaxy formation in low-mass halos at high redshift

    CERN Document Server

    Ceverino, Daniel; Klimek, Elizabeth; Trujillo-Gomez, Sebastian; Churchill, Christopher W; Primack, Joel

    2013-01-01

    Any successful model of galaxy formation needs to explain the low rate of star formation in the small progenitors of today's normal galaxies. The low efficiency of star formation is necessary for reproducing the low stellar-to-halo mass fractions, as suggested by current abundance matching models. We found that the main driver of this low efficiency is the radiation pressure exerted by ionizing photons from massive and young stars. We model the effect of radiation pressure in cosmological, zoom-in galaxy formation simulations, as a non-thermal pressure that acts locally around dense and optically thick star-forming regions. We also include the effect of photoionization and photoheating on the gas cooling and heating rates. In some conditions, the full photoionization of HI reduces the HI peak of the cooling curve, effectively preventing cooling in the 10^4-10^4.5 K regime. We also consider a simple model for the boosting of radiation pressure due to the trapping of infrared radiation. The main effect of the l...

  14. More than just halo mass: Modelling how the red galaxy fraction depends on multiscale density in a HOD framework

    CERN Document Server

    Phleps, Stefanie; Zibetti, Stefano; Budavári, Tamás

    2013-01-01

    The fraction of galaxies with red colours depends sensitively on environment, and on the way in which environment is measured. To distinguish competing theories for the quenching of star formation, a robust and complete description of environment is required, to be applied to a large sample of galaxies. The environment of galaxies can be described using the density field of neighbours on multiple scales - the multiscale density field. We are using the Millennium simulation and a simple HOD prescription which describes the multiscale density field of Sloan Digital Sky Survey DR7 galaxies to investigate the dependence of the fraction of red galaxies on the environment. Using a volume limited sample where we have sufficient galaxies in narrow density bins, we have more dynamic range in halo mass and density for satellite galaxies than for central galaxies. Therefore we model the red fraction of central galaxies as a constant while we use a functional form to describe the red fraction of satellites as a function ...

  15. MultiDark simulations: the story of dark matter halo concentrations and density profiles

    Science.gov (United States)

    Klypin, Anatoly; Yepes, Gustavo; Gottlöber, Stefan; Prada, Francisco; Heß, Steffen

    2016-04-01

    Predicting structural properties of dark matter haloes is one of the fundamental goals of modern cosmology. We use the suite of MultiDark cosmological simulations to study the evolution of dark matter halo density profiles, concentrations, and velocity anisotropies. We find that in order to understand the structure of dark matter haloes and to make 1-2 per cent accurate predictions for density profiles, one needs to realize that halo concentration is more complex than the ratio of the virial radius to the core radius in the Navarro-Frenk-White (NFW) profile. For massive haloes, the average density profile is far from the NFW shape and the concentration is defined by both the core radius and the shape parameter α in the Einasto approximation. We show that haloes progress through three stages of evolution. They start as rare density peaks and experience fast and nearly radial infall that brings mass closer to the centre, producing a highly concentrated halo. Here, the halo concentration increases with increasing halo mass and the concentration is defined by the α parameter with a nearly constant core radius. Later haloes slide into the plateau regime where the accretion becomes less radial, but frequent mergers still affect even the central region. At this stage, the concentration does not depend on halo mass. Once the rate of accretion and merging slows down, haloes move into the domain of declining concentration-mass relation because new accretion piles up mass close to the virial radius while the core radius is staying constant. Accurate analytical fits are provided.

  16. A break in the high-redshift stellar mass Tully-Fisher relation

    Science.gov (United States)

    Christensen, Lise; Hjorth, Jens

    2017-09-01

    We investigate the stellar-mass Tully-Fisher relation (TFR) between the stellar mass and the integrated gas velocity dispersion, quantified by the kinematic estimator S0.5 measured from strong emission lines in spectra of galaxies at 0 law slope and normalization of the TFR are independent of redshift out to z ∼ 3. The scatter in the TFR is 3, the scatter increases and the existence of a correlation is not obvious. The high-luminosity sample exhibits a flatter slope of 1.5 ± 0.2 at z natural consequence of galaxy models with a mass-dependent stellar-to-halo mass ratio.

  17. Detection of a Nearby Halo Debris Stream in the WISE and 2MASS Surveys

    CERN Document Server

    Grillmair, Carl J; Masci, Frank J; Conroy, Tim; Sesar, Branimir; Eisenhardt, Peter R M; Wright, Edward L

    2013-01-01

    Combining the Wide-Field Infrared Survey Explorer All-Sky Release with the 2MASS Point Source Catalog, we detect a nearby, moderately metal-poor stellar debris stream spanning 24 degrees across the southern sky. The stream, which we designate Alpheus, is at an estimated distance of ~1.9 kpc. Its position, orientation, width, estimated metallicity, and to some extent its distance, are in approximate agreement with what one might expect of the leading tidal tail of the southern globular cluster NGC 288.

  18. Ortho effect in electron ionization mass spectrometry of N-acylanilines bearing a proximal halo substituent.

    Science.gov (United States)

    Jariwala, Freneil B; Figus, Margaret; Attygalle, Athula B

    2008-08-01

    Electron ionization (EI) mass spectra are not very helpful for characterizing ortho, meta, and para isomers of underivatized haloanilines since their spectra are virtually identical. In contrast, when the amino group of chloro-, bromo-, or iodoanilines is transformed to an N-formyl, N-acetyl, or N-benzoyl derivative, the spectra of the derivatives reveal a highly dramatic loss of a halogen radical, instead of an HX elimination usually expected from an "ortho effect." For example, the spectra of N-formyl, N-acetyl, and N-benzoyl derivatives of ortho isomers of chloro-, bromo-, and iodoanilines show a very prominent peak at m/z 120, 134, and 196, respectively, for the loss of the corresponding halogen atom.

  19. Ultra-Flat Galaxies Selected from RFGC Catalog. II. Orbital Estimates of Halo Masses

    CERN Document Server

    Karachentsev, I D; Kudrya, Yu N

    2016-01-01

    We used the Revised Flat Galaxy Catalog (RFGC) to select 817 ultra-flat (UF) edge-on disk galaxies with blue and red apparent axial ratios of $(a/b)_B > 10.0$ and $(a/b)_R > 8.5$. The sample covering the whole sky, except the Milky Way zone, contains 490 UF galaxies with measured radial velocities. Our inspection of the neighboring galaxies around them revealed only 30 companions with radial velocity difference of $\\mid\\Delta V\\mid<500$ km s$^{-1}$ inside the projected separation of $R_p < 250$ kpc. Wherein, the wider area around the UF galaxy within $R_p < 750$ kpc contains no other neighbors brighter than the UF galaxy itself in the same velocity span. The resulting sample galaxies mostly belong to the morphological types Sc, Scd, Sd. They have a moderate rotation velocity curve amplitude of about $120$ km s$^{-1}$ and a moderate K-band luminosity of about $10^{10}L_{\\odot}$. The median difference of radial velocities of their companions is $87$ km s$^{-1}$, yielding the median orbital mass estimat...

  20. NEW MESON MASS RELATION AND LOWEST PSEUDOSCALAR GLUEBALL MASS

    Institute of Scientific and Technical Information of China (English)

    WU NING; RUAN TU-NAN; ZHENG ZHI-PENG

    2001-01-01

    After considering its mixing with the glueball, we give a new mass relation for the meson nonet. According to this mass relation and the predicted mass of the pseudoscalar glueball given by lattice calculations and the effective Hamiltonian, the expected mass of the mixed pseudoscalar glueball is about 1.7 GeV. This result is helpful in the experimental search for the mixed isoscalar pseudoscalar glueball. η(1760) is discussed as a possible candidate for this type of particle.

  1. THE BLACK HOLE–DARK MATTER HALO CONNECTION

    Energy Technology Data Exchange (ETDEWEB)

    Sabra, Bassem M. [Department of Physics and Astronomy, Notre Dame University-Louaize, P.O. Box 72 Zouk Mikael, Zouk Mosbeh (Lebanon); Saliba, Charbel; Akl, Maya Abi; Chahine, Gilbert, E-mail: bsabra@ndu.edu.lb [Department of Physics, Lebanese University II, Fanar (Lebanon)

    2015-04-10

    We explore the connection between the central supermassive black holes (SMBH) in galaxies and the dark matter halo through the relation between the masses of the SMBHs and the maximum circular velocities of the host galaxies, as well as the relationship between stellar velocity dispersion of the spheroidal component and the circular velocity. Our assumption here is that the circular velocity is a proxy for the mass of the dark matter halo. We rely on a heterogeneous sample containing galaxies of all types. The only requirement is that the galaxy has a direct measurement of the mass of its SMBH and a direct measurement of its circular velocity and its velocity dispersion. Previous studies have analyzed the connection between the SMBH and dark matter halo through the relationship between the circular velocity and the bulge velocity dispersion, with the assumption that the bulge velocity dispersion stands in for the mass of the SMBH, via the well-established SMBH mass–bulge velocity dispersion relation. Using intermediate relations may be misleading when one is studying them to decipher the active ingredients of galaxy formation and evolution. We believe that our approach will provide a more direct probe of the SMBH and the dark matter halo connection. We find that the correlation between the mass of SMBHs and the circular velocities of the host galaxies is extremely weak, leading us to state the dark matter halo may not play a major role in regulating the black hole growth in the present Universe.

  2. THE AVERAGE STAR FORMATION HISTORIES OF GALAXIES IN DARK MATTER HALOS FROM z = 0-8

    Energy Technology Data Exchange (ETDEWEB)

    Behroozi, Peter S.; Wechsler, Risa H. [Kavli Institute for Particle Astrophysics and Cosmology, Stanford, CA 94305 (United States); Conroy, Charlie [Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States)

    2013-06-10

    We present a robust method to constrain average galaxy star formation rates (SFRs), star formation histories (SFHs), and the intracluster light (ICL) as a function of halo mass. Our results are consistent with observed galaxy stellar mass functions, specific star formation rates (SSFRs), and cosmic star formation rates (CSFRs) from z = 0 to z = 8. We consider the effects of a wide range of uncertainties on our results, including those affecting stellar masses, SFRs, and the halo mass function at the heart of our analysis. As they are relevant to our method, we also present new calibrations of the dark matter halo mass function, halo mass accretion histories, and halo-subhalo merger rates out to z = 8. We also provide new compilations of CSFRs and SSFRs; more recent measurements are now consistent with the buildup of the cosmic stellar mass density at all redshifts. Implications of our work include: halos near 10{sup 12} M{sub Sun} are the most efficient at forming stars at all redshifts, the baryon conversion efficiency of massive halos drops markedly after z {approx} 2.5 (consistent with theories of cold-mode accretion), the ICL for massive galaxies is expected to be significant out to at least z {approx} 1-1.5, and dwarf galaxies at low redshifts have higher stellar mass to halo mass ratios than previous expectations and form later than in most theoretical models. Finally, we provide new fitting formulae for SFHs that are more accurate than the standard declining tau model. Our approach places a wide variety of observations relating to the SFH of galaxies into a self-consistent framework based on the modern understanding of structure formation in {Lambda}CDM. Constraints on the stellar mass-halo mass relationship and SFRs are available for download online.

  3. Quasilocal mass in general relativity.

    Science.gov (United States)

    Wang, Mu-Tao; Yau, Shing-Tung

    2009-01-16

    There have been many attempts to define the notion of quasilocal mass for a spacelike two surface in spacetime by the Hamilton-Jacobi analysis. The essential difficulty in this approach is to identify the right choice of the background configuration to be subtracted from the physical Hamiltonian. Quasilocal mass should be non-negative for surfaces in general spacetime and zero for surfaces in flat spacetime. In this Letter, we propose a new definition of gauge-independent quasilocal mass and prove that it has the desired properties.

  4. CLASH: The Concentration-Mass Relation of Galaxy Clusters

    CERN Document Server

    Merten, J; Postman, M; Umetsu, K; Zitrin, A; Medezinski, E; Nonino, M; Koekemoer, A; Melchior, P; Gruen, D; Moustakas, L A; Bartelmann, M; Host, O; Donahue, M; Coe, D; Molino, A; Jouvel, S; Monna, A; Seitz, S; Czakon, N; Lemze, D; Balestra, I; Rosati, P; Benítez, N; Biviano, A; Bouwens, R; Bradley, L; Broadhurst, T; Carrasco, M; Ford, H; Grillo, C; Infante, L; Kelson, D; Lahav, O; Massey, R; Moustakas, J; Rasia, E; Rhodes, J; Vega, J; Zheng, W

    2014-01-01

    We present a new determination of the concentration-mass relation for galaxy clusters based on our comprehensive lensing analysis of 19 X-ray selected galaxy clusters from the Cluster Lensing and Supernova Survey with Hubble (CLASH). Our sample spans a redshift range between 0.19 and 0.89. We combine weak lensing constraints from the Hubble Space Telescope (HST) and from ground-based wide field data with strong lensing constraints from HST. The result are reconstructions of the surface-mass density for all CLASH clusters on multi-scale grids. Our derivation of NFW parameters yields virial masses between 0.53 x 10^15 and 1.76 x 10^15 M_sol/h and the halo concentrations are distributed around c_200c ~ 3.7 with a 1-sigma significant negative trend with cluster mass. We find an excellent 4% agreement between our measured concentrations and the expectation from numerical simulations after accounting for the CLASH selection function based on X-ray morphology. The simulations are analyzed in 2D to account for possib...

  5. On the Relative Ages of the $\\alpha$-Rich and $\\alpha$-Poor Stellar Populations in the Galactic Halo

    CERN Document Server

    Hawkins, Keith; Gilmore, Gerry; Masseron, Thomas

    2014-01-01

    We study the ages of $\\alpha$-rich and $\\alpha$-poor stars in the halo using a sample of F and G dwarfs from the Sloan Digital Sky Survey (SDSS). To separate stars based on [$\\alpha$/Fe], we have developed a new semi-empirical spectral-index based method and applied it to the low-resolution, moderate signal-to-noise SDSS spectra. The method can be used to estimate the [$\\alpha$/Fe] directly providing a new and widely applicable way to estimate [$\\alpha$/Fe] from low-resolution spectra. We measured the main-sequence turnoff temperature and combined it with the metallicities and a set of isochrones to estimate the age of the $\\alpha$-rich and $\\alpha$-poor populations in our sample. We found all stars appear to be older than 8 Gyr confirming the idea that the Galactic halo was formed very early on. A bifurcation appears in the age-metallicity relation such that in the low metallicity regime the $\\alpha$-rich and $\\alpha$-poor populations are coeval while in the high metallicity regime the $\\alpha$-rich populati...

  6. The Blackhole-Dark Matter Halo Connection

    CERN Document Server

    Sabra, Bassem M; Akl, Maya Abi; Chahine, Gilbert

    2015-01-01

    We explore the connection between the central supermassive blackholes (SMBH) in galaxies and the dark matter halo through the relation between the masses of the SMBHs and the maximum circular velocities of the host galaxies, as well as the relationship between stellar velocity dispersion of the spheroidal component and the circular velocity. Our assumption here is that the circular velocity is a proxy for the mass of the dark matter halo. We rely on a heterogeneous sample containing galaxies of all types. The only requirement is that the galaxy has a direct measurement of the mass of its SMBH and a direct measurement of its circular velocity and its velocity dispersion. Previous studies have analyzed the connection between the SMBH and dark matter halo through the relationship between the circular velocity and the bulge velocity dispersion, with the assumption that the bulge velocity dispersion stands in for the mass of the SMBH, via the well{}-established SMBH mass{}-bulge velocity dispersion relation. Using...

  7. Radial velocity moments of dark matter haloes

    CERN Document Server

    Wojtak, R; Gottlöber, S; Mamon, G A; Wojtak, Radoslaw; Lokas, Ewa L.; Gottloeber, Stefan; Mamon, Gary A.

    2005-01-01

    Using cosmological N-body simulations we study the radial velocity distribution in dark matter haloes focusing on the lowest-order even moments, dispersion and kurtosis. We determine the properties of ten massive haloes in the simulation box approximating their density distribution by the NFW formula characterized by the virial mass and concentration. We also calculate the velocity anisotropy parameter of the haloes and find it mildly radial and increasing with distance from the halo centre. The radial velocity dispersion of the haloes shows a characteristic profile with a maximum, while the radial kurtosis profile decreases with distance starting from a value close to Gaussian near the centre. We therefore confirm that dark matter haloes possess intrinsically non-Gaussian, flat-topped velocity distributions. We find that the radial velocity moments of the simulated haloes are very well reproduced by the solutions of the Jeans equations obtained for the halo parameters with the anisotropy measured in the simu...

  8. An Order Statistics Approach to the Halo Model for Galaxies

    CERN Document Server

    Paul, Niladri; Sheth, Ravi K

    2016-01-01

    We use the Halo Model to explore the implications of assuming that galaxy luminosities in groups are randomly drawn from an underlying luminosity function. We show that even the simplest of such order statistics models -- one in which this luminosity function $p(L)$ is universal -- naturally produces a number of features associated with previous analyses based on the `central plus Poisson satellites' hypothesis. These include the monotonic relation of mean central luminosity with halo mass, the Lognormal distribution around this mean, and the tight relation between the central and satellite mass scales. In stark contrast to observations of galaxy clustering, however, this model predicts $\\textit{no}$ luminosity dependence of large scale clustering. We then show that an extended version of this model, based on the order statistics of a $\\textit{halo mass dependent}$ luminosity function $p(L|m)$, is in much better agreement with the clustering data as well as satellite luminosities, but systematically under-pre...

  9. Global non-axisymmetric perturbation configurations in a composite disc system with an isopedic magnetic field: relation between dark matter halo and magnetic field

    CERN Document Server

    Xiang-Gruess, M; Duschl, W J

    2009-01-01

    We study global non-axisymmetric stationary perturbations of aligned and unaligned logarithmic spiral configurations in an axisymmetric composite differentially rotating disc system of scale-free stellar and isopedically magnetized gas discs coupled by gravity. The gas disc is threaded across by a vertical magnetic field $B_z$ with a constant dimensionless isopedic ratio $\\lambda\\equiv 2\\pi\\sqrt{G} \\Sigma^{(g)}/B_z$ of surface gas mass density $\\Sigma^{(g)}$ to $B_z$ with $G$ being the gravitational constant. Our exploration focuses on the relation between $\\lambda$ and the dark matter amount represented by a ratio $f\\equiv\\bar{\\Phi}/\\Phi$ in order to sustain stationary perturbation configurations, where $\\bar{\\Phi}$ is the gravitational potential of a presumed axisymmetric halo of dark matter and $\\Phi$ is the gravitational potential of the composite disc matter. High and low $\\lambda$ values correspond to relatively weak and strong magnetic fields given the same gas surface mass density, respectively. The m...

  10. The Connection between the Host Halo and the Satellite Galaxies of the Milky Way

    Science.gov (United States)

    Lu, Yu; Benson, Andrew; Mao, Yao-Yuan; Tonnesen, Stephanie; Peter, Annika H. G.; Wetzel, Andrew R.; Boylan-Kolchin, Michael; Wechsler, Risa H.

    2016-10-01

    Many properties of the Milky Way’s (MW) dark matter halo, including its mass-assembly history, concentration, and subhalo population, remain poorly constrained. We explore the connection between these properties of the MW and its satellite galaxy population, especially the implication of the presence of the Magellanic Clouds for the properties of the MW halo. Using a suite of high-resolution N-body simulations of MW-mass halos with a fixed final {M}{vir}˜ {10}12.1 {M}⊙ , we find that the presence of Magellanic Cloud-like satellites strongly correlates with the assembly history, concentration, and subhalo population of the host halo, such that MW-mass systems with Magellanic Clouds have lower concentration, more rapid recent accretion, and more massive subhalos than typical halos of the same mass. Using a flexible semi-analytic galaxy formation model that is tuned to reproduce the stellar mass function of the classical dwarf galaxies of the MW with Markov-Chain Monte-Carlo, we show that adopting host halos with different mass-assembly histories and concentrations can lead to different best-fit models for galaxy-formation physics, especially for the strength of feedback. These biases arise because the presence of the Magellanic Clouds boosts the overall population of high-mass subhalos, thus requiring a different stellar-mass-to-halo-mass ratio to match the data. These biases also lead to significant differences in the mass-metallicity relation, the kinematics of low-mass satellites, the number counts of small satellites associated with the Magellanic Clouds, and the stellar mass of MW itself. Observations of these galaxy properties can thus provide useful constraints on the properties of the MW halo.

  11. Weak lensing measurement of the mass-richness relation using the SDSS database

    CERN Document Server

    Johana, Gonzalez Elizabeth; Diego, García Lambas; Manuel, Merchán; Gael, Foëx; Martín, Chalela

    2016-01-01

    We study the mass-richness relation using galaxy catalogues and images from the Sloan Digital Sky Survey. We use two independent methods, in the first one, we calibrate the scaling relation with weak-lensing mass estimates. In the second procedure we apply a background subtraction technique to derive the probability distribution, $P(M \\mid N)$, that groups with $N$-members have a virialized halo mass $M$. Lensing masses are derived in different richness bins for two galaxy systems sets: the maxBCG catalogue and a catalogue based on a group finder algorithm developed by Yang et al. MaxBCG results are used to test the lensing methodology. The lensing mass-richness relation for the Yang et al. group sample shows a good agreement with $P(M \\mid N)$ obtained independently with a straightforward procedure.

  12. Weak-lensing measurement of the mass-richness relation using the SDSS data base

    Science.gov (United States)

    Gonzalez, Elizabeth Johana; Rodriguez, Facundo; García Lambas, Diego; Merchán, Manuel; Foëx, Gael; Chalela, Martín

    2017-02-01

    We study the mass-richness relation using galaxy catalogues and images from the Sloan Digital Sky Survey. We use two independent methods: In the first one, we calibrate the scaling relation with weak-lensing mass estimates. In the second procedure, we apply a background subtraction technique to derive the probability distribution, P(M∣N), that groups with N-members have a virialized halo mass M. Lensing masses are derived in different richness bins for two galaxy systems sets: the maxBCG catalogue and a catalogue based on a group finder algorithm developed by Yang et al. Results of maxBCG are used to test the lensing methodology. The lensing mass-richness relation for the Yang et al. group sample shows a good agreement with P(M∣N) obtained independently with a straightforward procedure.

  13. The Magellanic Stream to Halo Interface: Processes that shape our nearest gaseous Halo Stream

    CERN Document Server

    Nigra, Lou; Gallagher, J S; Lockman, Felix J; Nidever, David L; Majewski, Steven R

    2009-01-01

    Understanding the hydrodynamical processes and conditions at the interface between the Magellanic Stream (MS) and the Galactic halo is critical to understanding the MS and by extension, gaseous tails in other interacting galaxies. These processes operate on relatively small scales and not only help shape this clumpy stream, but also affect the neutral gas dynamics and transfer of mass from the stream to the halo, thus affecting metal enrichment and gas replenishment of the Galaxy. We describe an observational program to place constraints on these processes through high-resolution measurements of HI emission, HI absorption and Halpha emission with unprecedented sensitivity. Methods will include structural analysis, searching for cold gas cores in clumps and analyzing gas kinematics as it transitions to the halo. The latter method includes sophisticated spatial integration techniques to deeply probe the neutral gas, which we apply to a new HI map obtained from the Green Bank Telescope with the highest sensitivi...

  14. Haloes gone MAD: The Halo-Finder Comparison Project

    Science.gov (United States)

    Knebe, Alexander; Knollmann, Steffen R.; Muldrew, Stuart I.; Pearce, Frazer R.; Aragon-Calvo, Miguel Angel; Ascasibar, Yago; Behroozi, Peter S.; Ceverino, Daniel; Colombi, Stephane; Diemand, Juerg; Dolag, Klaus; Falck, Bridget L.; Fasel, Patricia; Gardner, Jeff; Gottlöber, Stefan; Hsu, Chung-Hsing; Iannuzzi, Francesca; Klypin, Anatoly; Lukić, Zarija; Maciejewski, Michal; McBride, Cameron; Neyrinck, Mark C.; Planelles, Susana; Potter, Doug; Quilis, Vicent; Rasera, Yann; Read, Justin I.; Ricker, Paul M.; Roy, Fabrice; Springel, Volker; Stadel, Joachim; Stinson, Greg; Sutter, P. M.; Turchaninov, Victor; Tweed, Dylan; Yepes, Gustavo; Zemp, Marcel

    2011-08-01

    We present a detailed comparison of fundamental dark matter halo properties retrieved by a substantial number of different halo finders. These codes span a wide range of techniques including friends-of-friends, spherical-overdensity and phase-space-based algorithms. We further introduce a robust (and publicly available) suite of test scenarios that allow halo finder developers to compare the performance of their codes against those presented here. This set includes mock haloes containing various levels and distributions of substructure at a range of resolutions as well as a cosmological simulation of the large-scale structure of the universe. All the halo-finding codes tested could successfully recover the spatial location of our mock haloes. They further returned lists of particles (potentially) belonging to the object that led to coinciding values for the maximum of the circular velocity profile and the radius where it is reached. All the finders based in configuration space struggled to recover substructure that was located close to the centre of the host halo, and the radial dependence of the mass recovered varies from finder to finder. Those finders based in phase space could resolve central substructure although they found difficulties in accurately recovering its properties. Through a resolution study we found that most of the finders could not reliably recover substructure containing fewer than 30-40 particles. However, also here the phase-space finders excelled by resolving substructure down to 10-20 particles. By comparing the halo finders using a high-resolution cosmological volume, we found that they agree remarkably well on fundamental properties of astrophysical significance (e.g. mass, position, velocity and peak of the rotation curve). We further suggest to utilize the peak of the rotation curve, vmax, as a proxy for mass, given the arbitrariness in defining a proper halo edge. Airport code for Madrid, Spain

  15. What size halos do local LIRGs live in?

    CERN Document Server

    Tekola, Abiy G; Vaisanen, Petri

    2013-01-01

    This work investigates the preferred environment of local Luminous IR Galaxies (LIRGs) in terms of the host halos that they inhabit, and in comparison to a control galaxy sample. The LIRGs are drawn from the IRAS Point Source Catalogue redshift survey (PSCz), while the control sample is drawn from the 2MASS redshift survey (2MRS). A friends-of-friends algorithm was run on the 2MRS sample to identify galaxies living in the same dark matter halos and the PSCz galaxies were then associated with these identified halos. We show that the relative probability of finding local LIRGs with respect to 2MASS galaxies is largest in approximately group size halos (Mhalo~10^13M_sun), and declines both in the cluster regime and in smaller halos. This confirms, using a different technique than in previous work, that local LIRGs are indeed more abundant in group environments than elsewhere. We also find a trend between the LIR values of LIRGs and their location within their host dark matter halos, such that the average locatio...

  16. Comparing halo bias from abundance and clustering

    CERN Document Server

    Hoffmann, Kai; Gaztanaga, Enrique

    2015-01-01

    We model the abundance of haloes in the $\\sim(3 \\ \\text{Gpc}/h)^3$ volume of the MICE Grand Challenge simulation by fitting the universal mass function with an improved Jack-Knife error covariance estimator that matches theory predictions. We present unifying relations between different fitting models and new predictions for linear ($b_1$) and non-linear ($c_2$ and $c_3$) halo clustering bias. Different mass function fits show strong variations in their overall poor performance when including the low mass range ($M_h \\lesssim 3 \\ 10^{12} \\ M_{\\odot}/h$) in the analysis, which indicates noisy friends-of-friends halo detection given the MICE resolution ($m_p \\simeq 3 \\ 10^{10} \\ M_{\\odot}$/h). Together with fits from the literature we find an overall variance in the amplitudes of around $10%$ in the low mass and up to $50%$ in the high mass (galaxy cluster) range ($M_h > 10^{14} \\ M_{\\odot}/h$). These variations propagate into a $10%$ change in $b_1$ predictions and a $50%$ change in $c_2$ or $c_3$. Despite the...

  17. Cross-correlation Weak Lensing of SDSS galaxy Clusters II: Cluster Density Profiles and the Mass--Richness Relation

    CERN Document Server

    Johnston, David E; Wechsler, Risa H; Rozo, Eduardo; Koester, Benjamin P; Frieman, Joshua A; McKay, Timothy A; Evrard, August E; Becker, Matthew R; Annis, James

    2007-01-01

    We interpret and model the statistical weak lensing measurements around 130,000 groups and clusters of galaxies in the Sloan Digital Sky Survey presented by Sheldon et al. 2007 (Paper I). We present non-parametric inversions of the 2D shear profiles to the mean 3D cluster density and mass profiles in bins of both optical richness and cluster i-band luminosity. We correct the inferred 3D profiles for systematic effects, including non-linear shear and the fact that cluster halos are not all precisely centered on their brightest galaxies. We also model the measured cluster shear profile as a sum of contributions from the brightest central galaxy, the cluster dark matter halo, and neighboring halos. We infer the relations between mean cluster virial mass and optical richness and luminosity over two orders of magnitude in cluster mass; the virial mass at fixed richness or luminosity is determined with a precision of 13% including both statistical and systematic errors. We also constrain the halo concentration para...

  18. Dynamical family properties and dark halo scaling relations of giant elliptical galaxies

    CERN Document Server

    Gerhard, O E; Saglia, R P; Bender, R; Gerhard, Ortwin; Kronawitter, Andi; Bender, Ralf

    2001-01-01

    Based on a uniform dynamical analysis of line-profile shapes for 21 luminous round elliptical galaxies, we have investigated the dynamical family relations of ellipticals: (i) The circular velocity curves (CVCs) of elliptical galaxies are flat to within ~10% for R>~0.2R_e. (ii) Most ellipticals are moderately radially anisotropic; their dynamical structure is surprisingly uniform. (iii) Elliptical galaxies follow a Tully-Fisher (TF) relation, with v_c^max=300 km/s for an L_B^* galaxy. At given v_c^max, they are ~1 mag fainter in B and appear to have slightly lower baryonic mass than spirals even for maximum M/L_B. (iv) The luminosity dependence of M/L_B is confirmed. The tilt of the Fundamental Plane is not caused by dynamical non-homology, nor only by an increasing dark matter fraction with L. It is, however, consistent with stellar population models based on published metallicities and ages. The main driver is therefore probably metallicity, and a secondary population effect is needed to explain the K-band ...

  19. Galaxy Groups in the SDSS DR4: II. halo occupation statistics

    CERN Document Server

    Yang, Xiaohu; Bosch, Frank C van den

    2007-01-01

    We investigate various halo occupation statistics using a large galaxy group catalogue constructed from the SDSS DR4 with an adaptive halo-based group finder. The conditional luminosity function (CLF) is measured separately for all, red and blue galaxies, as well as in terms of central and satellite galaxies. The CLFs for central and satellite galaxies can be well modelled with a log-normal distribution and a modified Schechter form, respectively. About 85% of the central galaxies and about 80% of the satellite galaxies in halos with masses $M_h\\ga 10^{14}\\msunh$ are red galaxies. These numbers decrease to 50% and 40%, respectively, in halos with $M_h \\sim 10^{12}\\msunh$. For halos of a given mass, the distribution of the luminosities of central galaxies, $L_c$, has a dispersion of about 0.15 dex. The mean luminosity (stellar mass) of the central galaxies scales with halo mass as $L_c\\propto M_h^{0.17}$ ($M_{*,c}\\propto M_h^{0.22}$) for halos with masses $M\\gg 10^{12.5}\\msunh$, and both relations are signific...

  20. Cross-correlation Weak Lensing of SDSS galaxy Clusters II: Cluster Density Profiles and the Mass--Richness Relation

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, David E.; Sheldon, Erin S.; Wechsler, Risa H.; Rozo, Eduardo; Koester, Benjamin P.; Frieman, Joshua A.; McKay, Timothy A.; Evrard, August E.; Becker, Matthew; Annis, James

    2007-09-28

    We interpret and model the statistical weak lensing measurements around 130,000 groups and clusters of galaxies in the Sloan Digital Sky Survey presented by Sheldon et al. (2007). We present non-parametric inversions of the 2D shear profiles to the mean 3D cluster density and mass profiles in bins of both optical richness and cluster i-band luminosity. Since the mean cluster density profile is proportional to the cluster-mass correlation function, the mean profile is spherically symmetric by the assumptions of large-scale homogeneity and isotropy. We correct the inferred 3D profiles for systematic effects, including non-linear shear and the fact that cluster halos are not all precisely centered on their brightest galaxies. We also model the measured cluster shear profile as a sum of contributions from the brightest central galaxy, the cluster dark matter halo, and neighboring halos. We infer the relations between mean cluster virial mass and optical richness and luminosity over two orders of magnitude in cluster mass; the virial mass at fixed richness or luminosity is determined with a precision of {approx} 13% including both statistical and systematic errors. We also constrain the halo concentration parameter and halo bias as a function of cluster mass; both are in good agreement with predictions from N-body simulations of LCDM models. The methods employed here will be applicable to deeper, wide-area optical surveys that aim to constrain the nature of the dark energy, such as the Dark Energy Survey, the Large Synoptic Survey Telescope and space-based surveys.

  1. First results from the Dragonfly Telephoto Array: the apparent lack of a stellar halo in the massive spiral galaxy M101

    CERN Document Server

    van Dokkum, Pieter; Merritt, Allison

    2014-01-01

    We use a new telescope concept, the Dragonfly Telephoto Array, to study the low surface brightness outskirts of the spiral galaxy M101. The radial surface brightness profile is measured down to mu_g ~ 32 mag/arcsec^2, a depth that approaches the sensitivity of star count studies in the Local Group. We convert surface brightness to surface mass density using the radial g-r color profile. The mass density profile shows no significant upturn at large radius and is well-approximated by a simple bulge + disk model out to R = 70 kpc, corresponding to 18 disk scale lengths. Fitting a bulge + disk + halo model we find that the best-fitting halo mass M_halo ~ 1.7 x 10^8 M_sun. The total stellar mass of M101 is M_tot,* ~ 5.3 x 10^10 Msun, and we infer that the halo mass fraction f_halo = M_halo / M_tot,* ~ 0.003. This mass fraction is lower than that of the Milky Way (f_halo ~ 0.02) and M31 (f_halo ~ 0.04). All three galaxies fall below the f_halo - M_tot,* relation predicted by recent cosmological simulations that tra...

  2. Conformal theory of galactic halos

    CERN Document Server

    Nesbet, R K

    2011-01-01

    Current cosmological theory describes an isolated galaxy as an observable central galaxy, surrounded by a large spherical halo attributed to dark matter. Galaxy formation by condensation of mass-energy out of a primordial uniform background is shown here to leave a scar, observed as a centripetal gravitational field halo in anomalous galactic rotation and in gravitational lensing. Conformal theory accounts for the otherwise counterintuitive centripetal effect.

  3. The Large Scale Bias of Dark Matter Halos: Numerical Calibration and Model Tests

    CERN Document Server

    Tinker, Jeremy L; Kravtsov, Andrey V; Klypin, Anatoly; Warren, Michael S; Yepes, Gustavo; Gottlober, Stefan

    2010-01-01

    We measure the clustering of dark matter halos in a large set of collisionless cosmological simulations of the flat LCDM cosmology. Halos are identified using the spherical overdensity algorithm, which finds the mass around isolated peaks in the density field such that the mean density is Delta times the background. We calibrate fitting functions for the large scale bias that are adaptable to any value of Delta we examine. We find a ~6% scatter about our best fit bias relation. Our fitting functions couple to the halo mass functions of Tinker et. al. (2008) such that bias of all dark matter is normalized to unity. We demonstrate that the bias of massive, rare halos is higher than that predicted in the modified ellipsoidal collapse model of Sheth, Mo, & Tormen (2001), and approaches the predictions of the spherical collapse model for the rarest halos. Halo bias results based on friends-of-friends halos identified with linking length 0.2 are systematically lower than for halos with the canonical Delta=200 o...

  4. The rates and modes of gas accretion on to galaxies and their gaseous haloes

    CERN Document Server

    van de Voort, Freeke; Booth, C M; Haas, Marcel R; Vecchia, Claudio Dalla

    2010-01-01

    (Abridged) We study the rate at which gas accretes on to galaxies and haloes and investigate whether the accreted gas was shocked to high temperatures before reaching a galaxy. For this purpose we use a suite of large cosmological, hydrodynamical simulations from the OWLS project. We improve on previous work by considering a wider range of halo masses and redshifts, by distinguishing accretion on to haloes and galaxies, by including important feedback processes, and by comparing simulations with different physics. The specific rate of gas accretion on to haloes is, like that for dark matter, only weakly dependent on halo mass. For halo masses Mhalo>>10^11 Msun it is relatively insensitive to feedback processes. In contrast, accretion rates on to galaxies are determined by radiative cooling and by outflows driven by supernovae and active galactic nuclei. Galactic winds increase the halo mass at which the central galaxies grow the fastest by about two orders of magnitude to Mhalo~10^12 Msun. Gas accretion is bi...

  5. Fingerprints of the initial conditions on the density profiles of cold and warm dark matter haloes

    CERN Document Server

    Polisensky, E

    2015-01-01

    We use N-body simulations of dark matter haloes in cold dark matter (CDM) and a large set of different warm dark matter (WDM) cosmologies to demonstrate that the spherically averaged density profile of dark matter haloes has a shape that depends on the power spectrum of matter perturbations. Density profiles are steeper in WDM but become shallower at scales less than one percent of the virial radius. Virialization isotropizes the velocity dispersion in the inner regions of the halo but does not erase the memory of the initial conditions in phase space. The location of the observed deviations from CDM in the density profile and in phase space can be directly related to the ratio between the halo mass and the filtering mass and are most evident in small mass haloes, even for a 34 keV thermal relic WDM. The rearrangement of mass within the haloes supports analytic models of halo structure that include angular momentum. We also find evidence of a dependence of the slope of the inner density profile in CDM cosmolo...

  6. How far do they go? The outer structure of dark matter halos

    CERN Document Server

    Prada, F; Simonneau, E; Betancort-Rijo, J; Patiri, S G; Gottlöber, S; Sanchez-Conde, M A

    2005-01-01

    We study the density profiles of collapsed galaxy-size dark matter halos with masses 1e11-5e12 Msun focusing mostly on the halo outer regions from the formal virial radius Rvir up to 5-7Rvir. We find that isolated halos in this mass range extend well beyond Rvir exhibiting all properties of virialized objects up to 2-3Rvir: relatively smooth density profiles and no systematic infall velocities. The dark matter halos in this mass range do not grow as one naively may expect through a steady accretion of satellites, i.e., on average there is no mass infall. This is strikingly different from more massive halos, which have large infall velocities outside of the virial radius. We provide accurate fit for the density profile of these galaxy-size halos. For a wide range (0.01-2)Rvir of radii the halo density profiles are fit with the approximation rho=rho_s exp(-2n[x^{1/n}-1])+rho_m, where x=r/r_s, rho_m is the mean matter density of the Universe, and the index n is in the range n=6-7.5. These profiles do not show a ...

  7. Ultraviolet Halos Around Spiral Galaxies. I. Morphology

    CERN Document Server

    Hodges-Kluck, Edmund; Bregman, Joel

    2016-01-01

    We examine ultraviolet halos around a sample of highly inclined galaxies within 25 Mpc to measure their morphology and luminosity. Despite contamination from galactic light scattered into the wings of the point-spread function, we find that UV halos occur around each galaxy in our sample. Around most galaxies the halos form a thick, diffuse disk-like structure, but starburst galaxies with galactic superwinds have qualitatively different halos that are more extensive and have filamentary structure. The spatial coincidence of the UV halos above star-forming regions, the lack of consistent association with outflows or extraplanar ionized gas, and the strong correlation between the halo and galaxy UV luminosity suggest that the UV light is an extragalactic reflection nebula. UV halos may thus represent 1-10 million solar masses of dust within 2-10 kpc of the disk, whose properties may change with height in starburst galaxies.

  8. Feedback-regulated star formation and escape of LyC photons from mini-haloes during reionisation

    Science.gov (United States)

    Kimm, Taysun; Katz, Harley; Haehnelt, Martin; Rosdahl, Joakim; Devriendt, Julien; Slyz, Adrianne

    2017-01-01

    Reionisation in the early Universe is likely driven by dwarf galaxies. Using cosmological radiation-hydrodynamic simulations, we study star formation and the escape of Lyman continuum (LyC) photons from mini-haloes with M_halo ≲ 10^8 M_⊙. Our simulations include a new thermo-turbulent star formation model, non-equilibrium chemistry, and relevant stellar feedback processes (photoionisation by young massive stars, radiation pressure, and mechanical supernova explosions). We find that feedback reduces star formation very efficiently in mini-haloes, resulting in the stellar mass consistent with the slope and normalisation reported in Kimm & Cen (2014) and the empirical stellar mass-to-halo mass relation derived in the local Universe. Because star formation is stochastic and dominated by a few gas clumps, the escape fraction in mini-haloes is generally determined by radiation feedback (heating due to photo-ionisation), rather than supernova explosions. We also find that the photon number-weighted mean escape fraction in mini-haloes is higher (˜20-40%) than that in atomic-cooling haloes, although the instantaneous fraction in individual haloes varies significantly. The escape fraction from Pop III stars is found to be significant (≳ 10%) only when the mass is greater than ˜100 M_⊙. Based on simple analytic calculations, we show that LyC photons from mini-haloes are, despite their high escape fractions, of minor importance for reionisation due to inefficient star formation. We confirm previous claims that stars in atomic-cooling haloes with masses 10^8 M_⊙ ≲ M_halo ≲ 10^{11} M_⊙ are likely to be the most important source of reionisation.

  9. Weak-lensing-inferred scaling relations of galaxy clusters in the RCS2: mass-richness, mass-concentration, mass-bias and more

    CERN Document Server

    van Uitert, Edo; Hoekstra, Henk; Semboloni, Elisabetta; Gladders, Michael D; Yee, H K C

    2016-01-01

    We study a sample of ~10^4 galaxy clusters in the redshift range 0.2 5x10^13 h_70^-1 M_sun, discovered in the second Red-sequence Cluster Survey (RCS2). The depth and excellent image quality of the RCS2 enable us to detect the cluster-mass cross-correlation up to z~0.7. To obtain cluster masses, concentrations and halo biases, we fit a cluster halo model simultaneously to the lensing signal and to the projected density profile of red-sequence cluster members, as the latter provides tight constraints on the cluster miscentring distribution. We parametrise the mass-richness relation as M_200 = A x (N_200/20)^alpha, and find A = (16.7 +- 1.2) x 10^13 h_70^-1 M_sun and alpha = 0.73 +- 0.09 at low redshift (0.2

  10. A universal angular momentum profile for dark matter haloes

    CERN Document Server

    Liao, Shihong; Chu, M -C

    2016-01-01

    The angular momentum distribution in dark matter haloes and galaxies is a key ingredient in understanding their formation. Especially, the internal distribution of angular momenta is closely related to the formation of disk galaxies. In this article, we use haloes identified from a high-resolution simulation, the Bolshoi simulation, to study the spatial distribution of specific angular momenta, $j(r,\\theta)$. We show that by stacking haloes with similar masses to increase the signal-to-noise ratio, the profile can be fitted as a simple function, $j(r,\\theta)=j_s \\sin^2(\\theta/\\theta_s) (r/r_s)^2/(1+r/r_s)^4 $, with three free parameters, $j_s, r_s$, and $\\theta_s$. Specifically, $j_s$ correlates with the halo mass $M_\\mathrm{vir}$ as $j_s\\propto M_\\mathrm{vir}^{2/3}$, $r_s$ has a weak dependence on the halo mass as $r_s \\propto M_\\mathrm{vir}^{0.040}$, and $\\theta_s$ is independent of $M_\\mathrm{vir}$. This profile agrees with that from a rigid shell model, though its origin is unclear. Our universal specific...

  11. The Halos and Environments of Nearby Galaxies (HERON) Survey

    CERN Document Server

    Rich, R Michael; Bullock, James; Burkert, Andreas; Collins, Michelle; de Groot, Laura; Kennefick, Julia; Koch, Andreas; Longstaff, Francis; Sales, Laura

    2016-01-01

    We have used dedicated 0.7m telescopes in California and Israel to image the halos of ~200 galaxies in the Local Volume to 29 mag/sq arcsec, the sample mainly drawn from the 2MASS Large Galaxy Atlas (LGA). We supplement the LGA sample with dwarf galaxies and more distant giant ellipticals. Low surface brightness halos exceeding 50 kpc in diameter are found only in galaxies more luminous than L* and classic interaction signatures are relatively infrequent. Halo diameter is correlated with total galaxy luminosity. Extended low surface brightness halos are present even in galaxies as faint as M_V=-18. Edge-on galaxies with boxy bulges tend to lack extended spheroidal halos, while those with large classical bulges exhibit extended round halos, supporting the notions that boxy or barlike bulges originate from disks. Most face-on spiral galaxies present features that appear to be irregular extensions of spiral arms, although rare cases show smooth boundaries with no sign of star formation. Although we serendipitous...

  12. Unbound particles in dark matter halos

    Energy Technology Data Exchange (ETDEWEB)

    Behroozi, Peter S.; Wechsler, Risa H. [Kavli Institute for Particle Astrophysics and Cosmology, Physics Department, Stanford University and SLAC National Accelerator Laboratory 2575 Sand Hill Road, Menlo Park, CA (United States); Loeb, Abraham, E-mail: behroozi@stanford.edu, E-mail: aloeb@cfa.harvard.edu, E-mail: rwechsler@stanford.edu [Department of Astronomy, Harvard University 60 Garden St, Cambridge, MA (United States)

    2013-06-01

    We investigate unbound dark matter particles in halos by tracing particle trajectories in a simulation run to the far future (a = 100). We find that the traditional sum of kinetic and potential energies is a very poor predictor of which dark matter particles will eventually become unbound from halos. We also study the mass fraction of unbound particles, which increases strongly towards the edges of halos, and decreases significantly at higher redshifts. We discuss implications for dark matter detection experiments, precision calibrations of the halo mass function, the use of baryon fractions to constrain dark energy, and searches for intergalactic supernovae.

  13. Unbound particles in dark matter halos

    Energy Technology Data Exchange (ETDEWEB)

    Behroozi, Peter S.; Loeb, Abraham; Wechsler, Risa H.

    2013-06-13

    We investigate unbound dark matter particles in halos by tracing particle trajectories in a simulation run to the far future (a = 100). We find that the traditional sum of kinetic and potential energies is a very poor predictor of which dark matter particles will eventually become unbound from halos. We also study the mass fraction of unbound particles, which increases strongly towards the edges of halos, and decreases significantly at higher redshifts. We discuss implications for dark matter detection experiments, precision calibrations of the halo mass function, the use of baryon fractions to constrain dark energy, and searches for intergalactic supernovae.

  14. Weak Lensing with the Hyper Suprime-Cam Survey: Connecting the Mass Profiles of Massive Galaxies with their Dark Matter Halos

    Science.gov (United States)

    Leauthaud, Alexie; HSC Survey Collaboration

    2017-01-01

    The HSC survey is an ambitious multi-wavelength (g,r,i,z,y) weak-lensing program to map out 1400 square degrees of the sky with the 8.2m Subaru Telescope to a 5 sigma point-source depth of i~26 mag. This is a truly unique combination of deep imaging over a wide area which makes this a well suited data-set for studying the mass profiles and assembly histories of the most rare and massive galaxies in the universe. Furthermore, the lensing capabilities of HSC means that we can tie the luminous properties of massive galaxies to the properties of their dark matter halos. With 240 deg^2 of excellent quality imaging data already in hand, I will show that HSC can simultaneously map the light profiles of massive galaxies out to 100 kpc and characterize the profiles of their host dark matter halos to radii greater than 10 Mpc. By comparing with modern hydrodynamic simulations of galaxy formation, I will show that the combination of these two measurements provides strong observational constraints on the strength of feedback mechanisms in massive galaxies.

  15. Dynamical Constraints On The Galaxy-Halo Connection

    Science.gov (United States)

    Desmond, Harry

    2017-07-01

    Dark matter halos comprise the bulk of the universe's mass, yet must be probed by the luminous galaxies that form within them. A key goal of modern astrophysics, therefore, is to robustly relate the visible and dark mass, which to first order means relating the properties of galaxies and halos. This may be expected not only to improve our knowledge of galaxy formation, but also to enable high-precision cosmological tests using galaxies and hence maximise the utility of future galaxy surveys. As halos are inaccessible to observations - as galaxies are to N-body simulations - this relation requires an additional modelling step.The aim of this thesis is to develop and evaluate models of the galaxy-halo connection using observations of galaxy dynamics. In particular, I build empirical models based on the technique of halo abundance matching for five key dynamical scaling relations of galaxies - the Tully-Fisher, Faber-Jackson, mass-size and mass discrepancy-acceleration relations, and Fundamental Plane - which relate their baryon distributions and rotation or velocity dispersion profiles. I then develop a statistical scheme based on approximate Bayesian computation to compare the predicted and measured values of a number of summary statistics describing the relations' important features. This not only provides quantitative constraints on the free parameters of the models, but also allows absolute goodness-of-fit measures to be formulated. I find some features to be naturally accounted for by an abundance matching approach and others to impose new constraints on the galaxy-halo connection; the remainder are challenging to account for and may imply galaxy-halo correlations beyond the scope of basic abundance matching.Besides providing concrete statistical tests of specific galaxy formation theories, these results will be of use for guiding the inputs of empirical and semi-analytic galaxy formation models, which require galaxy-halo correlations to be imposed by hand. As

  16. The Dragonfly nearby Galaxies Survey. I. Substantial Variation in the Diffuse Stellar Halos around Spiral Galaxies

    Science.gov (United States)

    Merritt, Allison; van Dokkum, Pieter; Abraham, Roberto; Zhang, Jielai

    2016-10-01

    Galaxies are thought to grow through accretion; as less massive galaxies are disrupted and merge over time, their debris results in diffuse, clumpy stellar halos enveloping the central galaxy. Here we present a study of the variation in the stellar halos of galaxies, using data from the Dragonfly Nearby Galaxies Survey (DNGS). The survey consists of wide field, deep ({μ }g\\gt 31 mag arcsec‑2) optical imaging of nearby galaxies using the Dragonfly Telephoto Array. Our sample includes eight spiral galaxies with stellar masses similar to that of the Milky Way, inclinations of 16-19 degrees and distances between 7-18 Mpc. We construct stellar mass surface density profiles from the observed g-band surface brightness in combination with the g ‑ r color as a function of radius, and compute the halo fractions from the excess stellar mass (relative to a disk+bulge fit) beyond 5 half-mass radii. We find a mean halo fraction of 0.009 ± 0.005 and a large rms scatter of {1.01}-0.26+0.9 dex. The peak-to-peak scatter of the halo fraction is a factor of \\gt 100—while some galaxies feature strongly structured halos resembling that of M31, three of the eight have halos that are completely undetected in our data. We conclude that spiral galaxies as a class exhibit a rich variety in stellar halo properties, implying that their assembly histories have been highly non-uniform. We find no convincing evidence for an environmental or stellar mass dependence of the halo fraction in the sample.

  17. The statistics of LCDM Halo Concentrations

    CERN Document Server

    Neto, Angelo F; Bett, Philip; Cole, Shaun; Navarro, Julio F; Frenk, Carlos S; White, Simon D M; Springel, Volker; Jenkins, Adrian

    2007-01-01

    We use the Millennium Simulation (MS) to study the statistics of LCDM halo concentrations at z = 0. Our results confirm that the average halo concentration declines monotonically with mass; a power-law fits well the concentration-mass relation for over 3 decades in mass, up to the most massive objects to form in a LCDM universe (~ 10^15 h^-1 Msol). This is in clear disagreement with the predictions of the model proposed by Bullock et al. for these rare objects, and agrees better with the original predictions of Navarro, Frenk, & White. The large volume surveyed, together with the unprecedented numerical resolution of the MS, allow us to estimate with confidence the distribution of concentrations and, consequently, the abundance of systems with unusual properties. About one in a hundred cluster haloes (M200 >~ 3x10^14 h^-1 Msol) have concentrations exceeding c200 = 7.5, a result that may be used to interpret the likelihood of unusually strong massive gravitational lenses, such as Abell 1689, in the LCDM co...

  18. Measurement of the abundance of stellar mass compact objects in the galactic halo by detecting micro-lenses in the Large Magellanic Cloud; Mesure de l'abondance des astres sombres de masse stellaire dans le halo galactique par la recherche de phenomenes de microlentilles vers les nuages de magellan

    Energy Technology Data Exchange (ETDEWEB)

    Lasserre, Th

    2000-05-09

    Many experimental and theoretical results lead to the conclusion that at least 80 percent of the mass of our Galaxy is dark. Part of this so-called dark matter could be in the form of stellar mass compact objects, called MACHOS; these could be detected using the gravitational microlensing effect. The first generation experiments EROS1 and MACHO have strongly constrained the galactic abundance of objects lighter than 0.01 solar mass to less than 10 percent of the total mass. In parallel, the observation by the MACHO group of massive candidates (half the Sun's mass), numerous enough to constitute 50 percent of galactic dark matter, was a further motivation for the EROS group to extend this search to stellar mass objects in a second phase, EROS2. The present work deals with the analysis of 25 million stellar light curves in the Large Magellanic Cloud, observed for three years in order to extract the rare microlensing candidates and to measure the galactic halo mass fraction in the form of compact objects. After recalling the motivations of this search and the theoretical context, I describe the EROS2 experiment. The observational strategy and the photometric reduction procedures needed to deal with the 1.2 To of data are then presented. A new method to detect micro-lenses is detailed, as well as a discussion of background light curves, poorly known. We do not find enough microlensing candidates to explain the galactic rotation curve; this confirms, and improve on previous EROS1 and EROS2 results. Combining all results from EROS allows to exclude that MACHOS with a mass between 10 e-7 and 10 solar mass are important constituents of the galactic halo. This statement agrees with recent results from the MACHO group, although our interpretations differ, namely on the topics of the location of the lenses, and of a possible contamination of the microlensing ample by background phenomena. (author)

  19. Bar instability in disk-halo systems

    CERN Document Server

    Sellwood, J A

    2016-01-01

    We show that the exponential growth rate of a bar in a stellar disk is substantially greater when the disk is embedded in a live halo than in a rigid one having the same mass distribution. We also find that the vigor of the instability in disk-halo systems varies with the shape of the halo velocity ellipsoid. Disks in rigid halos that are massive enough to be stable by the usual criteria, quickly form bars in isotropic halos and much greater halo mass is needed to avoid a strong bar; thus stability criteria derived for disks in rigid halos do not apply when the halo is responsive. The study presented here is of an idealized family of models with near uniform central rotation and that lack an extended halo; we present more realistic models with extended halos in a companion paper. The puzzle presented by the absence of strong bars in some galaxies having gently rising inner rotation curves is compounded by the results presented here.

  20. Bars in Cuspy Dark Halos

    CERN Document Server

    Dubinski, John; Shlosman, Isaac

    2008-01-01

    We examine the bar instability in models with an exponential disk and a cuspy NFW-like dark matter (DM) halo inspired by cosmological simulations. Bar evolution is studied as a function of numerical resolution in a sequence of models spanning 10K to 100M DM particles - including a multi-mass model with an effective resolution of 10G. The goal is to find convergence in dynamical behaviour. We characterize the bar growth, the buckling instability, pattern speed decay through resonant transfer of angular momentum, and possible destruction of the DM halo cusp. Overall, most characteristics converge in behaviour in detail for halos containing more than 10M particles. Notably, the formation of the bar does not destroy the density cusp in this case. These higher resolution simulations clearly illustrate the importance of discrete resonances in transporting angular momentum from the bar to the halo.

  1. On the mass-luminosity relation.

    Science.gov (United States)

    Mccluskey, G. E., Jr.; Kondo, Y.

    1972-01-01

    The results of a least-squares study of the mass-luminosity relation for eclipsing and visual binary stars consisting of main sequence components are presented. Two methods are discussed. First, the values of the coefficients A and B in the relation log M = A + BM sub BOL are determined. Then a technique which permits the determination of alpha and beta in the relation M = alpha L beta, when only the sum of the masses, and not the individual masses of each component, is known. The results and a comparison of the two methods are discussed. It is found that the following mass-luminosity relation represents the observational data satisfactorily: log M = 0.504 - 0.103 M sub BOL, -8 less than or equal to M sub BOL less than or equal to +10.5. A discussion of the data and of the possibility that separate mass-luminosity relations may exist for visual and eclipsing binaries is given. The possibility that more than one mass-luminosity relation is required in the range -8 less than or equal to M sub BOL less than or equal to +13 is also discussed.

  2. HaloSat - A CubeSat to Study the Hot Galactic Halo

    Science.gov (United States)

    Kaaret, Philip

    2017-08-01

    Observations of the nearby universe fail to locate about half of the normal matter (baryons) observed in the early universe. The missing baryons may be in hot galactic halos. HaloSat is a CubeSat designed to map oxygen line emission (O VII and O VIII) around the Milky Way in order to constrain the mass and spatial distribution of hot gas in the halo. HaloSat has a grasp competitive with current X-ray observatories. Its observing program will be optimized to minimize contributions from solar wind charge exchange (SWCX) emission that limit the accuracy of current measurements. We describe the current status of HaloSat.

  3. On the shape of dark matter halos from MultiDark Planck simulations

    CERN Document Server

    Vega, Jesús; Gottlöber, Stefan

    2016-01-01

    The halo shape plays a central role in determining important observational properties of the halos such as mass, concentration and lensing cross sections. The triaxiality of lensing galaxy clusters has a substantial impact on the distribution of the largest Einstein radii, while weak lensing techniques are sensitive to the intrinsic halo ellipticity. In this work, we provide scaling relations for the shapes of dark matter halos as a function of mass (peak height) and redshift over more than four orders of magnitude in halo masses, namely from $10^{11.5} h^{-1}$M$_\\odot$ to $10^{15.8}h^{-1}$M$_\\odot$. We have analysed four dark matter only simulations from the MultiDark cosmological simulation suite with more than 56 billion particles within boxes of 4.0, 2.5, 1.0 and 0.4 $h^{-1}$Gpc size assuming Planck cosmology. The dark matter halos have been identified in the simulations using the RockStar halo finder, which also determines the axis ratios in terms of the diagonalisation of the inertia tensor. The minor-t...

  4. GRAVITATIONALLY CONSISTENT HALO CATALOGS AND MERGER TREES FOR PRECISION COSMOLOGY

    Energy Technology Data Exchange (ETDEWEB)

    Behroozi, Peter S.; Wechsler, Risa H.; Wu, Hao-Yi [Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics, Stanford University, Stanford, CA 94305 (United States); Busha, Michael T. [Institute for Theoretical Physics, University of Zurich, CH-8006 Zurich (Switzerland); Klypin, Anatoly A. [Astronomy Department, New Mexico State University, Las Cruces, NM 88003 (United States); Primack, Joel R., E-mail: behroozi@stanford.edu, E-mail: rwechsler@stanford.edu [Department of Physics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States)

    2013-01-20

    We present a new algorithm for generating merger trees and halo catalogs which explicitly ensures consistency of halo properties (mass, position, and velocity) across time steps. Our algorithm has demonstrated the ability to improve both the completeness (through detecting and inserting otherwise missing halos) and purity (through detecting and removing spurious objects) of both merger trees and halo catalogs. In addition, our method is able to robustly measure the self-consistency of halo finders; it is the first to directly measure the uncertainties in halo positions, halo velocities, and the halo mass function for a given halo finder based on consistency between snapshots in cosmological simulations. We use this algorithm to generate merger trees for two large simulations (Bolshoi and Consuelo) and evaluate two halo finders (ROCKSTAR and BDM). We find that both the ROCKSTAR and BDM halo finders track halos extremely well; in both, the number of halos which do not have physically consistent progenitors is at the 1%-2% level across all halo masses. Our code is publicly available at http://code.google.com/p/consistent-trees. Our trees and catalogs are publicly available at http://hipacc.ucsc.edu/Bolshoi/.

  5. Gravitationally Consistent Halo Catalogs and Merger Trees for Precision Cosmology

    Science.gov (United States)

    Behroozi, Peter S.; Wechsler, Risa H.; Wu, Hao-Yi; Busha, Michael T.; Klypin, Anatoly A.; Primack, Joel R.

    2013-01-01

    We present a new algorithm for generating merger trees and halo catalogs which explicitly ensures consistency of halo properties (mass, position, and velocity) across time steps. Our algorithm has demonstrated the ability to improve both the completeness (through detecting and inserting otherwise missing halos) and purity (through detecting and removing spurious objects) of both merger trees and halo catalogs. In addition, our method is able to robustly measure the self-consistency of halo finders; it is the first to directly measure the uncertainties in halo positions, halo velocities, and the halo mass function for a given halo finder based on consistency between snapshots in cosmological simulations. We use this algorithm to generate merger trees for two large simulations (Bolshoi and Consuelo) and evaluate two halo finders (ROCKSTAR and BDM). We find that both the ROCKSTAR and BDM halo finders track halos extremely well; in both, the number of halos which do not have physically consistent progenitors is at the 1%-2% level across all halo masses. Our code is publicly available at http://code.google.com/p/consistent-trees. Our trees and catalogs are publicly available at http://hipacc.ucsc.edu/Bolshoi/.

  6. Statistics of Dark Matter Substructure: III. Halo-to-Halo Variance

    CERN Document Server

    Jiang, Fangzhou

    2016-01-01

    We present a study of unprecedented statistical power regarding the halo-to-halo variance of dark matter substructure. Using a combination of N-body simulations and a semi-analytical model, we investigate the variance in subhalo mass fractions and subhalo occupation numbers, with an emphasis on how these statistics scale with halo formation time. We demonstrate that the subhalo mass fraction, f_sub, is mainly a function of halo formation time, with earlier forming haloes having less substructure. At fixed formation redshift, the average f_sub is virtually independent of halo mass, and the mass dependence of f_sub is therefore mainly a manifestation of more massive haloes assembling later. We compare observational constraints on f_sub from gravitational lensing to our model predictions and simulation results. Although the inferred f_sub are substantially higher than the median LCDM predictions, they fall within the 95th percentile due to halo-to-halo variance. We show that while the halo occupation distributio...

  7. The Redshift Evolution of LCDM Halo Parameters

    CERN Document Server

    Muñoz-Cuartas, J C; Gottlöber, Stefan; Dutton, Aaron

    2011-01-01

    We study the mass and redshift dependence of the concentration parameter in Nbody simulations spanning masses from $10^{10} \\hMsun$ to $10^{15} \\hMsun$ and redshifts from 0 to 2. We present a series of fitting formulas that accurately describe the time evolution of the concentration-mass relation since z=2. Using arguments based on the spherical collapse model we study the behaviour of the scale length of the density profile during the assembly history of haloes, obtaining physical insights on the origin of the observed time evolution of the concentration mass relation. We present preliminary results of the implementation of this model in the prediction of the values of the concentration parameter for different masses and redshifts.

  8. Relations between the Sizes of Galaxies and Their Dark Matter Halos at Redshifts 0 < z < 3

    Science.gov (United States)

    Huang, Kuang-Han; Fall, S. Michael; Ferguson, Henry C.; van der Wel, Arjen; Grogin, Norman; Koekemoer, Anton; Lee, Seong-Kook; Pérez-González, Pablo G.; Wuyts, Stijn

    2017-03-01

    We derive relations between the effective radii R eff of galaxies and the virial radii R 200c of their dark matter halos over the redshift range 0 purpose, we derive a new SMHM relation based on the same selection criteria and other assumptions as for our sample of galaxies with size measurements. As a check on the robustness of our results, we also derive R eff–R 200c relations for three independent SMHM relations from the literature. We find that galaxy R eff is proportional on average to halo R 200c , confirming and extending to high redshifts the z = 0 results of Kravtsov. Late-type galaxies (with low Sérsic index and high specific star formation rate (sSFR)) follow a linear R eff–R 200c relation, with effective radii at 0.5 < z < 3 close to those predicted by simple models of disk formation; at z < 0.5, the sizes of late-type galaxies appear to be slightly below this prediction. Early-type galaxies (with high Sérsic index and low sSFR) follow a roughly parallel R eff–R 200c relation, ∼0.2–0.3 dex below the one for late-type galaxies. Our observational results, reinforced by recent hydrodynamical simulations, indicate that galaxies grow quasi-homologously with their dark matter halos.

  9. Constraining a halo model for cosmological neutral hydrogen

    Science.gov (United States)

    Padmanabhan, Hamsa; Refregier, Alexandre

    2017-02-01

    We describe a combined halo model to constrain the distribution of neutral hydrogen (H I) in the post-reionization universe. We combine constraints from the various probes of H I at different redshifts: the low-redshift 21-cm emission line surveys, intensity mapping experiments at intermediate redshifts, and the Damped Lyman-Alpha (DLA) observations at higher redshifts. We use a Markov Chain Monte Carlo approach to combine the observations and place constraints on the free parameters in the model. Our best-fitting model involves a relation between neutral hydrogen mass M_{H I} and halo mass M with a non-unit slope, and an upper and a lower cutoff. We find that the model fits all the observables but leads to an underprediction of the bias parameter of DLAs at z ˜ 2.3. We also find indications of a possible tension between the H I column density distribution and the mass function of H I-selected galaxies at z ˜ 0. We provide the central values of the parameters of the best-fitting model so derived. We also provide a fitting form for the derived evolution of the concentration parameter of H I in dark matter haloes, and discuss the implications for the redshift evolution of the H I-halo mass relation.

  10. Star Streams in Triaxial Isochrone Potentials with Sub-Halos

    CERN Document Server

    Carlberg, Raymond G

    2015-01-01

    The velocity, position, and action variable evolution of a tidal stream drawn out of a star cluster in a triaxial isochrone potential containing a sub-halo population reproduces many of the orbital effects of more general cosmological halos but allows easy calculation of orbital actions. We employ a spherical shell code which we show accurately reproduces the results of a tree gravity code for a collisionless star cluster. Streams from clusters on high eccentricity orbits, $e\\gtrsim 0.6$, can spread out so much that the amount of material at high enough surface density to stand out on the sky may be only a few percent of the stream's total mass. Low eccentricity streams remain more spatially coherent, but sub-halos both broaden the stream and displace the centerline with details depending on the orbits allowed within the potential. Overall, the majority of stream particles have changes in their total actions of only 1-2\\%, leaving the mean stream relatively undisturbed. A halo with 1\\% of the mass in sub-halo...

  11. The clustering of ALFALFA galaxies: dependence on HI mass, relationship to optical samples & clues on host halo properties

    CERN Document Server

    Papastergis, Emmanouil; Haynes, Martha P; Rodríguez-Puebla, Aldo; Jones, Michael G

    2013-01-01

    We use a sample of ~6000 galaxies detected by the Arecibo Legacy Fast ALFA (ALFALFA) 21cm survey, to measure the clustering properties of HI-selected galaxies. We find no convincing evidence for a dependence of clustering on the galactic atomic hydrogen (HI) mass, over the range M_HI ~ 10^{8.5} - 10^{10.5} M_sun. We show that previously reported results of weaker clustering for low-HI mass galaxies are probably due to finite-volume effects. In addition, we compare the clustering of ALFALFA galaxies with optically selected samples drawn from the Sloan Digital Sky Survey (SDSS). We find that HI-selected galaxies cluster more weakly than even relatively optically faint galaxies, when no color selection is applied. Conversely, when SDSS galaxies are split based on their color, we find that the correlation function of blue optical galaxies is practically indistinguishable from that of HI-selected galaxies. At the same time, SDSS galaxies with red colors are found to cluster significantly more than HI-selected gala...

  12. ZENS IV. Similar Morphological Changes associated with Mass- and Environment-Quenching, and the Relative importance of Bulge Growth versus the Fading of Disks

    CERN Document Server

    Carollo, C M; Lilly, S J; Pipino, A; Bonoli, S; Finoguenov, A; Miniati, F; Norberg, P; Silverman, J D

    2014-01-01

    We use ZENS data at low redshift to study the dependence of the quenched satellite fraction and of the morphological mix of these quenched satellites, on three different environmental parameters: group halo mass, halo-centric distance and large-scale structure over-density. The fraction of quenched satellites is independent of halo mass and the surrounding large-scale overdensity, but increases towards the centres of the haloes, as previously found. The morphological mix is, however, constant with radial position, indicating that the well-known morphology-density relation results from the increasing fraction of quenched galaxies towards the centres of haloes. The constancy of the morphological outcome suggests that mass-quenching and satellite quenching have the same effect on the morphologies of the galaxies. The quenched satellites have larger B/T and smaller half-light radii than the star-forming satellites. These are mostly due to differences in the disks. The bulges in quenched satellites have very simil...

  13. Halo-coronal mass ejections near the 23rd solar minimum: lift-off, inner heliosphere, and in situ (1 AU signatures

    Directory of Open Access Journals (Sweden)

    D. B. Berdichevsky

    Full Text Available The extreme ultraviolet (EUV signatures of a solar lift-off, decametric and kilometric radio burst emissions and energetic particle (EP inner heliospheric signatures of an interplanetary shock, and in situ identification of its driver through solar wind observations are discussed for 12 isolated halo coronal mass ejections (H-CMEs occurring between December 1996 and 1997. For the aforementioned twelve and the one event added in the discussion, it is found that ten passed several necessary conditions for being a "Sun-Earth connection". It is found that low corona EUV and Ha chromospheric signatures indicate filament eruption as the cause of H-CME. These signatures indicate that the 12 events can be divided into two major subsets, 7 related to active regions (ARs and 5 unrelated or related to decayed AR. In the case of events related to AR, there is indication of a faster lift-off, while a more gradual lift-off appears to characterize the second set. Inner heliospheric signatures – the presence of long lasting enhanced energetic particle flux and/or kilometric type II radio bursts – of a driven shock were identified in half of the 12 events. The in situ (1 AU analyses using five different solar wind ejecta signatures and comparisons with the bidirectional flow of suprathermal particles and Forbush decreases result in indications of a strong solar wind ejecta signatures for 11 out of 12 cases. From the discussion of these results, combined with work by other authors for overlapping events, we conclude that good Sun-Earth connection candidates originate most likely from solar filament eruptions with at least one of its extremities located closer to the central meridian than ~ 30° E or ~ 35° W with a larger extension in latitudinal location possible. In seven of the twelve cases it appears that the encountered ejecta was driving a shock at 1 AU. Support for this interpretation is found on the approximately equal

  14. Effective field theory for halo nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Hagen, Philipp Robert

    2014-02-19

    such systems. We apply our model to some known and suspected halo nuclei, namely the light isotopes {sup 11}Li, {sup 14}Be and {sup 22}C and the hypothetical heavy atomic nucleus {sup 62}Ca. In particular, we calculate charge form factors, relative electric charge radii and dipole strengths as well as general dependencies of these observables on masses and one- and two-neutron separation energies. Our analysis of the {sup 62}Ca system provides evidence of Efimov physics along the Calcium isotope chain. Experimental key observables that facilitate a test of our findings are discussed.

  15. On the integrability of halo dipoles in gravity

    OpenAIRE

    Vieira, Werner M.; Letelier, Patricio S.

    1997-01-01

    We stress that halo dipole components are nontrivial in core-halo systems in both Newton's gravity and General Relativity. To this end, we extend a recent exact relativistic model to include also a halo dipole component. Next, we consider orbits evolving in the inner vacuum between a monopolar core and a pure halo dipole and find that, while the Newtonian dynamics is integrable, its relativistic counterpart is chaotic. This shows that chaoticity due only to halo dipoles is an intrinsic relati...

  16. Testing Feedback-Modified Dark Matter Haloes with Galaxy Rotation Curves: Estimation of Halo Parameters and Consistency with $\\Lambda$CDM

    CERN Document Server

    Katz, Harley; McGaugh, Stacy S; Di Cintio, Arianna; Brook, Chris B; Schombert, James M

    2016-01-01

    Cosmological N-body simulations predict dark matter (DM) haloes with steep central cusps (e.g. NFW), which contradicts observations of gas kinematics in low mass galaxies that imply the existence of shallow DM cores. Baryonic processes such as adiabatic contraction and gas outflows can, in principle, alter the initial DM density profile, yet their relative contributions to the halo transformation remain uncertain. Recent high resolution, cosmological hydrodynamic simulations (Di Cintio et al. 2014, DC14) predict that inner density profiles depend systematically on the ratio of stellar to DM mass (M$_*$/M$_{\\rm halo}$). Using a Markov Chain Monte Carlo approach, we test the NFW and the M$_*$/M$_{\\rm halo}$-dependent DC14 halo models against a sample of 147 galaxy rotation curves from the new SPARC data set. These galaxies all have extended HI rotation curves from radio interferometry as well as accurate stellar mass density profiles from near-infrared photometry. The DC14 halo profile provides markedly better ...

  17. Remark on the dilaton mass relation

    CERN Document Server

    Kasai, Aya; Suzuki, Hiroshi

    2016-01-01

    Recently, Golterman and Shamir presented an effective field theory which is supposed to describe the low-energy physics of the pion and the dilaton in an $SU(N_c)$ gauge theory with $N_f$ Dirac fermions in the fundamental representation. By employing this formulation with a slight but important modification, we derive a relation between the dilaton mass squared~$m_\\tau^2$, with and without the fermion mass~$m$, and the pion mass squared~$m_\\pi^2$ to the leading order of the chiral logarithm. This is analogous to a similar relation obtained by Matsuzaki and~Yamawaki on the basis of a somewhat different low-energy effective field theory. Our relation reads $m_\\tau^2=m_\\tau^2|_{m=0}+KN_f\\Hat{f}_\\pi^2m_\\pi^2/(2\\Hat{f}_\\tau^2)+O(m_\\pi^4\\ln m_\\pi^2)$ with~$K=9$, where $\\Hat{f}_\\pi$ and~$\\Hat{f}_\\tau$ are decay constants of the pion and the dilaton, respectively. This mass relation differs from the one derived by Matsuzaki and~Yamawaki on the points that $K=(3-\\gamma_m)(1+\\gamma_m)$, where $\\gamma_m$ is the mass ano...

  18. The COS-Halos Survey: Physical Conditions and Baryonic Mass in the Low-Redshift Circumgalactic Medium

    CERN Document Server

    Werk, Jessica K; Tumlinson, Jason; Peeples, Molly S; Tripp, Todd M; Fox, Andrew J; Lehner, Nicolas; Thom, Christopher; O'Meara, John M; Ford, Amanda Brady; Bordoloi, Rongmon; Katz, Neal; Tejos, Nicolas; Oppenheimer, Benjamin D; Davé, Romeel; Weinberg, David H

    2014-01-01

    We analyze the physical conditions of the cool (T ~ 10^4 K) circumgalactic medium (CGM) using the COS-Halos suite of gas column density measurements taken along 38 quasar sightlines passing within 160 kpc of L ~ L* galaxies at z~0.2. These data are well described by simple photoionization models, with the gas highly ionized (n_HII/n_H > 99%) by the extragalactic ultraviolet background (EUVB). Scaling by estimates for the virial radius, R_vir, we show that the ionization state (tracked by the dimensionless ionization parameter, U) increases with distance from the host galaxy. This correlation has a power-law form of U = (0.006 +/- 0.003)(R/R_vir)^(0.8 +/- 0.3), with significant scatter. The ionization parameters imply a decreasing volume density profile n_ H = 10^(-4.2 +/- 0.25) (R/R_vir)^(-0.8 +/-0.3). Our derived gas volume densities are several orders of magnitude lower than predictions from standard two-phase models with a cool medium in pressure equilibrium with a hot, diffuse medium. Applying the ionizat...

  19. PAndAS IN THE MIST: THE STELLAR AND GASEOUS MASS WITHIN THE HALOS OF M31 AND M33

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Geraint F. [Sydney Institute for Astronomy, School of Physics A28, The University of Sydney, NSW 2006 (Australia); Braun, Robert [CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia); McConnachie, Alan W. [Dominion Astrophysical Observatory, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Irwin, Michael J.; Chapman, Scott C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Ibata, Rodrigo A.; Martin, Nicolas F. [Observatoire de Strasbourg, 11, rue de l' Universite, F-67000 Strasbourg (France); Ferguson, Annette M. N. [Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Fardal, Mark [Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305 (United States); Dubinski, John [Department of Astronomy and Astrophysics, 50 St. George Street, University of Toronto, ON M5S 3H4 (Canada); Widrow, Larry [Department of Physics, Queen' s University, 99 University Avenue, Kingston, ON K7L 3N6 (Canada); Mackey, A. Dougal [Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Cotter Road, Weston Creek, ACT 2611 (Australia); Babul, Arif [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 3P6 (Canada); Tanvir, Nial R. [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Rich, Michael, E-mail: geraint.lewis@sydney.edu.au [Division of Astronomy, University of California, 8979 Math Sciences, Los Angeles, CA 90095-1562 (United States)

    2013-01-20

    Large-scale surveys of the prominent members of the Local Group have provided compelling evidence for the hierarchical formation of massive galaxies, revealing a wealth of substructure that is thought to be the debris from ancient and ongoing accretion events. In this paper, we compare two extant surveys of the M31-M33 subgroup of galaxies: the Pan-Andromeda Archaeological Survey of the stellar structure, and a combination of observations of the H I gaseous content, detected at 21 cm. Our key finding is a marked lack of spatial correlation between these two components on all scales, with only a few potential overlaps between stars and gas. The paucity of spatial correlation significantly restricts the analysis of kinematic correlations, although there does appear to be H I kinematically associated with the Giant Stellar Stream where it passes the disk of M31. These results demonstrate that different processes must significantly influence the dynamical evolution of the stellar and H I components of substructures, such as ram pressure driving gas away from a purely gravitational path. Detailed modeling of the offset between the stellar and gaseous substructures will provide a determination of the properties of the gaseous halos of M31 and M33.

  20. Halo abundances and shear in void models

    DEFF Research Database (Denmark)

    Alonso, David; García-Bellido, Juan; Haugbølle, Troels

    2012-01-01

    We study the non-linear gravitational collapse of dark matter into halos through numerical N-body simulations of Lemaitre-Tolman-Bondi void models. We extend the halo mass function formalism to these models in a consistent way. This extension not only compares well with the simulated data at all ...

  1. Halo abundances and shear in void models

    DEFF Research Database (Denmark)

    Alonso, David; García-Bellido, Juan; Haugbølle, Troels;

    2012-01-01

    We study the non-linear gravitational collapse of dark matter into halos through numerical N-body simulations of Lemaitre-Tolman-Bondi void models. We extend the halo mass function formalism to these models in a consistent way. This extension not only compares well with the simulated data at all...

  2. Galaxy power spectrum in redshift space: combining perturbation theory with the halo model

    CERN Document Server

    Okumura, Teppei; Seljak, Uros; Vlah, Zvonimir; Desjacques, Vincent

    2015-01-01

    Theoretical modeling of the redshift-space power spectrum of galaxies is crucially important to correctly extract cosmological information from redshift surveys. The task is complicated by the nonlinear biasing and redshift space distortion effects, which change with halo mass, and by the wide distribution of halo masses and their occupations by galaxies. One of the main modeling challenges is the existence of satellite galaxies that have both radial distribution and large virial velocities inside halos, a phenomenon known as the Finger-of-God effect. We present a model for the galaxy power spectrum of in which we decompose a given galaxy sample into central and satellite galaxies and relate different contributions to 1- and 2-halo terms in a halo model. Our primary goal is to ensure that any parameters that we introduce have physically meaningful values, and are not just fitting parameters. For the 2-halo terms we use the previously developed RSD modeling of halos in the context of distribution function and ...

  3. Evolution of Stellar-to-Halo Mass Ratio at z=0-7 Identified by Clustering Analysis with the Hubble Legacy Imaging and Early Subaru/Hyper Suprime-Cam Survey Data

    CERN Document Server

    Harikane, Yuichi; Ono, Yoshiaki; More, Surhud; Saito, Shun; Lin, Yen-Ting; Coupon, Jean; Shimasaku, Kazuhiro; Shibuya, Takatoshi; Price, Paul A; Lin, Lihwai; Hsieh, Bau-Ching; Ishigaki, Masafumi; Komiyama, Yutaka; Silverman, John; Takata, Tadafumi; Tamazawa, Hiroko; Toshikawa, Jun

    2015-01-01

    We present clustering analysis results from 10,540 Lyman break galaxies (LBGs) at z~4-7 that are identified in a combination of the Hubble legacy deep imaging and the complimentary large-area Subaru/Hyper Suprime-Cam data taken very recently. We measure angular correlation functions of these LBGs at z~4, 5, 6, and 7, and fit these measurements using halo occupation distribution (HOD) models that provide the estimates of halo masses, M_h~(1-20)x10^11 Msun. Our M_h estimates agree with those obtained by previous clustering studies in a UV-magnitude vs. M_h plane, and allow us to calculate stellar-to-halo mass ratios (SHMRs) of the LBGs. By comparison with the z~0 SHMR given by SDSS, we identify evolution of the SHMR from z~0 to z~4, and z~4 to z~7 at the >98% confidence levels. The SHMR decreases by a factor of ~3 from z~0 to 4, and increase by a factor of ~5 from z~4 to 7. We obtain the baryon conversion efficiency (BCE) of our LBGs at z~4, and find that the BCE increases with increasing dark matter halo mass....

  4. A Speeding Binary in the Galactic Halo

    Science.gov (United States)

    Kohler, Susanna

    2016-04-01

    The recent discovery of a hyper-velocity binary star system in the halo of the Milky Way poses a mystery: how was this system accelerated to its high speed?Accelerating StarsUnlike the uniform motion in the Galactic disk, stars in the Milky Ways halo exhibit a huge diversity of orbits that are usually tilted relative to the disk and have a variety of speeds. One type of halo star, so-called hyper-velocity stars, travel with speeds that can approach the escape velocity of the Galaxy.How do these hyper-velocity stars come about? Assuming they form in the Galactic disk, there are multiple proposed scenarios through which they could be accelerated and injected into the halo, such as:Ejection after a close encounter with the supermassive black hole at the Galactic centerEjection due to a nearby supernova explosionEjection as the result of a dynamical interaction in a dense stellar population.Further observations of hyper-velocity stars are necessary to identify the mechanism responsible for their acceleration.J1211s SurpriseModels of J1211s orbit show it did not originate from the Galactic center (black dot). The solar symbol shows the position of the Sun and the star shows the current position of J1211. The bottom two panels show two depictions(x-y plane and r-z plane) of estimated orbits of J1211 over the past 10 Gyr. [Nmeth et al. 2016]To this end, a team of scientists led by Pter Nmeth (Friedrich Alexander University, Erlangen-Nrnberg) recently studied the candidate halo hyper-velocity star SDSS J121150.27+143716.2. The scientists obtained spectroscopy of J1211 using spectrographs at the Keck Telescope in Hawaii and ESOs Very Large Telescope in Chile. To their surprise, they discovered the signature of a companion in the spectra: J1211 is actually a binary!Nmeth and collaborators found that J1211, located roughly 18,000 light-years away, is moving at a rapid ~570 km/s relative to the galactic rest frame. The binary system consists of a hot (30,600 K) subdwarf and a

  5. An Order Statistics Approach to the Halo Model for Galaxies

    Science.gov (United States)

    Paul, Niladri; Paranjape, Aseem; Sheth, Ravi K.

    2017-01-01

    We use the Halo Model to explore the implications of assuming that galaxy luminosities in groups are randomly drawn from an underlying luminosity function. We show that even the simplest of such order statistics models - one in which this luminosity function p(L) is universal - naturally produces a number of features associated with previous analyses based on the `central plus Poisson satellites' hypothesis. These include the monotonic relation of mean central luminosity with halo mass, the Lognormal distribution around this mean, and the tight relation between the central and satellite mass scales. In stark contrast to observations of galaxy clustering, however, this model predicts no luminosity dependence of large scale clustering. We then show that an extended version of this model, based on the order statistics of a halo mass dependent luminosity function p(L|m), is in much better agreement with the clustering data as well as satellite luminosities, but systematically under-predicts central luminosities. This brings into focus the idea that central galaxies constitute a distinct population that is affected by different physical processes than are the satellites. We model this physical difference as a statistical brightening of the central luminosities, over and above the order statistics prediction. The magnitude gap between the brightest and second brightest group galaxy is predicted as a by-product, and is also in good agreement with observations. We propose that this order statistics framework provides a useful language in which to compare the Halo Model for galaxies with more physically motivated galaxy formation models.

  6. Two distinct halo populations in the solar neighborhood. IV

    DEFF Research Database (Denmark)

    Nissen, P. E.; Schuster, W. J.

    2012-01-01

    We investigate if there is a difference in the lithium abundances of stars belonging to two halo populations of F and G main-sequence stars previously found to differ in [alpha/Fe] for the metallicity range -1.4 ...-resolution spectra using MARCS model atmospheres. Furthermore, masses of the stars are determined from the logTeff - logg diagram by interpolating between Yonsei-Yale evolutionary tracks. There is no significant systematic difference in the lithium abundances of high- and low-alpha halo stars. For the large majority...... predicted from standard Big Bang nucleosynthesis calculations and the WMAP baryon density. The relation, however, does not apply to stars with [Fe/H] halo stars were formed with a Li abundance close to the primordial value, and that lithium in their atmospheres has been...

  7. Borromean halo, Tango halo, and halo isomers in atomic nuclei

    Science.gov (United States)

    Izosimov, Igor

    2016-01-01

    Structure of the ground and excited states in halo-like nuclei is discussed. Both the Borromean and tango halo types can be observed for n-p configurations of atomic nuclei.Structure of the halo may be different for the different levels and resonances in atomic nuclei. Isobar analog, double isobar analog, configuration, and double configuration states can simultaneously have n-n, n-p, and p-p halo components in their wave functions. When the halo structure of the excited state differs from that of the ground state, or the ground state has non-halo structure, the γ-transition from the excited state to the ground state can be essentially hindered, i.e. the formation of a specific type of isomers (halo isomers) becomes possible. B(Mγ) and B(Eγ) values for γ-transitions in 6,7,8Li, 8,9,10Be, 8,10,11B, 10,11,12,13,14C, 13,14,15,16,17N, 15,16,17,19O, and 17F are analyzed. Special attention is given to nuclei which ground state does not exhibit halo structure but the excited state (halo isomer) may have one.

  8. The Initial-Final Mass Relation

    Science.gov (United States)

    Kalirai, Jason; Hansen, Brad; Kelson, Daniel; Reitzel, David; Rich, Michael; Richer, Harvey

    2015-08-01

    It is well known that the stellar life cycle is dominated by queiscent phases such as the hydrogen-burning stage and the eventual remnant white dwarf cooling phase. However, between these two stages, stars dramatically transform themselves by losing the bulk of their mass. Planetary nebulae provide a powerful clue to the physical processes involved in this transformation, however, our understanding of the detailed phasing, dependency to metallicity and other properties, and total amount of the source mass loss is still highly uncertain. Over the past 10 years, a new wave of space- and ground-based imaging and spectroscopy programs have uncovered the remnants of the planetary nebula evolutionary stage, white dwarfs, in a wide range of well measured environments. With knowledge of the host stellar population properties (e.g., ages of star clusters), we can map the masses and temperatures of the stellar remnants to the properties of their progenitors. This work has now led to the first global mapping of the initial-final mass relation from 0.8 Msun to 6 Msun. The resulting relation is a fundamental input into our understanding of the stellar evolution process for low and intermediate-mass stars that produce planetary nebulae and has a wide range of applications to interpret stellar populations in distant galaxies.

  9. The first halos

    CERN Document Server

    Schwarz, D J

    2006-01-01

    The size and time of formation of the first gravitationally bound objects in the Universe is set by the microphysical properties of the dark matter. It is argued that observations seem to favour cold and thermal candidates for the main contribution to the dark matter. For that type of dark matter, the size and time of formation of the first halos is determined by the elastic cross sections and mass of the CDM particles. Consequently, the astrophysics of CDM might allow us to measure some of the fundamental parameters of CDM particles. Essential for observations is the survival rate and spatial distribution of the very first objetcs, which are currently under debate.

  10. The mass-discrepancy acceleration relation in early-type galaxies: extended mass profiles and the phantom menace to MOND

    CERN Document Server

    Janz, Joachim; Romanowsky, Aaron J; Ciotti, Luca; Alabi, Adebusola; Forbes, Duncan A

    2016-01-01

    The dark matter (DM) haloes around spiral galaxies appear to conspire with their baryonic content: empirically, significant amounts of DM are inferred only below a universal characteristic acceleration scale. Moreover, the discrepancy between the baryonic and dynamical mass, which is usually interpreted as the presence of DM, follows a very tight mass discrepancy acceleration (MDA) relation. Its universality, and its tightness in spiral galaxies, poses a challenge for the DM interpretation and was used to argue in favour of MOdified Newtonian Dynamics (MOND). Here, we test whether or not this applies to early-type galaxies. We use the dynamical models of fast-rotator early-type galaxies by Cappellari et al. based on ATLAS$^{3D}$ and SLUGGS data, which was the first homogenous study of this kind, reaching ~4 $R_e$, where DM begins to dominate the total mass budget. We find the early-type galaxies to follow a MDA relation similar to spiral galaxies, but systematically offset. Also, while the slopes of the mass ...

  11. Beyond the Halo: Redefining environment with unbound matter in N-body simulations

    CERN Document Server

    Shattow, Genevieve M

    2015-01-01

    Approximately half of the matter in the Universe is "unbound" at z = 0, according to N-body simulations such as the Millennium Run. Here, we use the milli-Millennium simulation to examine the distribution of unbound matter in relation to the dark matter halos which host galaxies. We measure the unbound matter within two types of windows, using a halo dependent radius and a fixed radius at several different scales. We also consider the timescales over which a halo can accrete the local unbound matter at z = 2 and z = 0. Finally, we compare the unbound matter to observable properties of galaxies, such as local galaxy count environment and stellar mass. We find that halos at z = 2 can accrete far more of the nearby unbound matter over a Hubble time than halos at z = 0 and that 78% of particles within 5 $R_{vir}$ of a halo at z = 2 will be accreted by z = 0, compared to 36% of particles within 5 $h^{-1}$ Mpc of the halo. We also find that galaxy count environment is closely related to the amount of nearby unbound...

  12. Correlating galaxy colour and halo concentration: A tunable Halo Model of galactic conformity

    OpenAIRE

    Paranjape, Aseem; Kovac, Katarina; Hartley, William G.; Pahwa, Isha

    2015-01-01

    We extend the Halo Occupation Distribution (HOD) framework to generate mock galaxy catalogs exhibiting varying levels of "galactic conformity", which has emerged as a potentially powerful probe of environmental effects in galaxy evolution. Our model correlates galaxy colours in a group with the concentration of the common parent dark halo through a "group quenching efficiency" $\\rho$ which makes older, more concentrated halos $\\textit{at fixed mass}$ preferentially host redder galaxies. We fi...

  13. Properties of galaxy halos in Clusters and Voids

    CERN Document Server

    Antonuccio-Delogu, V; Pagliaro, A; Van Kampen, E; Colafrancesco, Sergio; Germaná, A; Gambera, M

    2000-01-01

    We use the results of a high resolution N-body simulation to investigate the role of the environment on the formation and evolution of galaxy-sized halos. Starting from a set of constrained initial conditions, we have produced a final configuration hosting a double cluster in one octant and a large void extending over two octants of the simulation box. In this paper we concentrate on {\\em gravitationally bound} galaxy-sized halos extracted from the two regions. Exploiting the high mass resolution of our simulation ($m_{body} = 2.1\\times 10^{9} h^{-1} M_{\\odot}$), we focus on halos with a relatively small mass: $5\\times 10^{10} \\leq M \\leq 2\\times 10^{12} M_{\\odot}$. We present results for two statistics: the relationship between 1-D velocity dispersion and mass and the probability distribution of the spin parameter $P(\\lambda)$. We do find a clear difference between halos lying in overdense regions and in voids. The \\svm relationship is well described by the Truncated Isothermal Sphere (TIS) model introduced ...

  14. Mass and Motion in General Relativity

    CERN Document Server

    Blanchet, Luc; Whiting, Bernard

    2011-01-01

    From the infinitesimal scale of particle physics to the cosmic scale of the universe, research is concerned with the nature of mass. While there have been spectacular advances in physics during the past century, mass still remains a mysterious entity at the forefront of current research. Our current perspective on gravitation has arisen over millennia, through the contemplation of falling apples, lift thought experiments and notions of stars spiraling into black holes.  In this volume, the world’s leading scientists offer a multifaceted approach to mass by giving a concise and introductory presentation based on insights from their respective fields of research on gravity. The main theme is mass and its motion within general relativity and other theories of gravity, particularly for compact bodies. Within this framework, all articles are tied together coherently, covering post-Newtonian and related methods as well as the self-force approach to the analysis of motion in curved space-time, closing with an ove...

  15. An accurate tool for the fast generation of dark matter halo catalogs

    CERN Document Server

    Monaco, P; Borgani, S; Crocce, M; Fosalba, P; Sheth, R K; Theuns, T

    2013-01-01

    We present a new parallel implementation of the PINpointing Orbit Crossing-Collapsed HIerarchical Objects (PINOCCHIO) algorithm, a quick tool, based on Lagrangian Perturbation Theory, for the hierarchical build-up of Dark Matter halos in cosmological volumes. To assess its ability to predict halo correlations on large scales, we compare its results with those of an N-body simulation of a 3 Gpc/h box sampled with 2048^3 particles taken from the MICE suite, matching the same seeds for the initial conditions. Thanks to the FFTW libraries and to the relatively simple design, the code shows very good scaling properties. The CPU time required by PINOCCHIO is a tiny fraction (~1/2000) of that required by the MICE simulation. Varying some of PINOCCHIO numerical parameters allows one to produce a universal mass function that lies in the range allowed by published fits, although it underestimates the MICE mass function of FoF halos in the high mass tail. We compare the matter-halo and the halo-halo power spectra with t...

  16. SCORCH I: The Galaxy-Halo Connection in the First Billion Years

    CERN Document Server

    Trac, Hy; Mansfield, Philip

    2015-01-01

    SCORCH (Simulations and Constructions of the Reionization of Cosmic Hydrogen) is a new project to study the Epoch of Reionization (EoR). In this first paper, we probe the connection between observed high-redshift galaxies and simulated dark matter halos in order to better understand the abundance and evolution of the primary source of ionizing radiation. A series of high-resolution N-body simulations is run to quantify the abundance of dark matter halos as a function of mass $M$, accretion rate $\\dot{M}$, and redshift $z$. A new fit for the halo mass function $dn/dM$ is $\\approx 20\\%$ more accurate at the high-mass end where bright galaxies are expected to reside. A novel approach is used to fit the halo accretion rate function $dn/d\\dot{M}$ in terms of the halo mass function. Abundance matching against the observed galaxy luminosity function is used to estimate the luminosity-mass relation and the luminosity-accretion-rate relation. The inferred star formation efficiency is not monotonic with $M$ nor $\\dot{M...

  17. Revealing the Chamaeleon: First detection of a low-mass stellar halo around the young open cluster Eta Chamaeleontis

    CERN Document Server

    Murphy, Simon J; Bessell, Michael S

    2010-01-01

    We have identified several lithium-rich low-mass (0.08MASS photometry, NOMAD astrometry and extensive follow-up spectroscopy. Several of these stars show substantial variation in their H-alpha emission line strengths on timescales of days to months, with at least one event attributable to accretion from a circumstellar disk. These findings are consistent with a dynamical origin for the current configuration of the cluster, without the need to invoke an abnormally top-heavy Initial Mass Function, as proposed by some authors.

  18. Relative Molecular Mass Distribution of BG Resins

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Benzoguanamine-formaldehyde (BG-F) resins are a class of amino resins, which are important cross-linking agents for epoxy, alkyol and acrylic resins, etc. The cross-linking performance is the best one when the polymerization degree is 2-4. This paper discusses the effects of the pH value for polycondensation and the formaldehyde to benzoguanamine mole ratio in a methanol system, and compares the relative molecular mass distribution using the Flory statistics method.

  19. The relation between mass and concentration in X-ray galaxy clusters at high redshift

    Science.gov (United States)

    Amodeo, S.; Ettori, S.; Capasso, R.; Sereno, M.

    2016-05-01

    Context. Galaxy clusters are the most recent, gravitationally bound products of the hierarchical mass accretion over cosmological scales. How the mass is concentrated is predicted to correlate with the total mass in the halo of the cluster, wherein systems at higher mass are less concentrated at given redshift and, for any given mass, systems with lower concentration are found at higher redshifts. Aims: Through a spatial and spectral X-ray analysis, we reconstruct the total mass profile of 47 galaxy clusters observed with Chandra in the redshift range 0.4 0.4, and is well suited to providing the first constraint on the concentration-mass relation at z> 0.7 from X-ray analysis. Methods: Under the assumption that the distribution of the X-ray emitting gas is spherically symmetric and in the hydrostatic equilibrium with the underlined gravitational potential, we combine the deprojected gas density and spectral temperature profiles through the hydrostatic equilibrium equation to recover the parameters that describe a Navarro-Frenk-White total mass distribution. The comparison with results from weak-lensing analysis reveals a very good agreement both for masses and concentrations. The uncertainties are however too large to make any robust conclusion about the hydrostatic bias of these systems. Results: The distribution of concentrations is well approximated by a log-normal function in all the mass and redshift ranges investigated. The relation is well described by the form c ∝ MB(1 + z)C with B = -0.50 ± 0.20, C = 0.12 ± 0.61 (at 68.3% confidence). This relation is slightly steeper than that predicted by numerical simulations (B ~ -0.1) and does not show any evident redshift evolution. We obtain the first constraints on the properties of the concentration-mass relation at z> 0.7 from X-ray data, showing a reasonable good agreement with recent numerical predictions.

  20. The relation between mass and concentration in X-ray galaxy clusters at high redshift

    CERN Document Server

    Amodeo, Stefania; Capasso, Raffaella; Sereno, Mauro

    2016-01-01

    Galaxy clusters are the most recent, gravitationally-bound products of the hierarchical mass accretion over cosmological scales. How the mass is concentrated is predicted to correlate with the total mass in the cluster's halo, with systems at higher mass being less concentrated at given redshift and for any given mass, systems with lower concentration are found at higher redshifts. Through a spatial and spectral X-ray analysis, we reconstruct the total mass profile of 47 galaxy clusters observed with Chandra in the redshift range $0.40.4$, and is well suited to provide the first constraint on the concentration--mass relation at $z>0.7$ from X-ray analysis. Under the assumptions that the distribution of the X-ray emitting gas is spherically symmetric and in hydrostatic equilibrium, we combine the deprojected gas density and spectral temperature profiles through the hydrostatic equilibrium equation to recover the parameters that describe a NFW total mass distribution. The comparison with results from weak lensi...

  1. Lambda-Cold Dark Matter, Stellar Feedback, and the Galactic Halo Abundance Pattern

    CERN Document Server

    Robertson, B; Font, A S; Johnston, K V; Hernquist, L; Robertson, Brant; Bullock, James S.; Font, Andreea S.; Johnston, Kathryn V.; Hernquist, Lars

    2005-01-01

    (Abridged) The hierarchical formation scenario for the stellar halo requires the accretion and disruption of dwarf galaxies, yet low-metallicity halo stars are enriched in alpha-elements compared to similar, low-metallicity stars in dwarf spheroidal (dSph) galaxies. We address this primary challenge for the hierarchical formation scenario for the stellar halo by combining chemical evolution modelling with cosmologically-motivated mass accretion histories for the Milky Way dark halo and its satellites. We demonstrate that stellar halo and dwarf galaxy abundance patterns can be explained naturally within the LCDM framework. Our solution relies fundamentally on the LCDM model prediction that the majority of the stars in the stellar halo were formed within a few relatively massive, ~5 x 10^10 Msun, dwarf irregular (dIrr)-size dark matter halos, which were accreted and destroyed ~10 Gyr in the past. These systems necessarily have short-lived, rapid star formation histories, are enriched primarily by Type II supern...

  2. Where are the Luminous Red Galaxies (LRGs)? Using correlation measurements and lensing to relate LRGs to dark matter halos

    CERN Document Server

    Hikage, Chiaki; Takada, Masahiro; Spergel, David N

    2012-01-01

    Nonlinear redshift-space distortions, the Finger-of-God (FoG) effect, can complicate the interpretation of the galaxy power spectrum. Here, we demonstrate the method proposed by Hikage et al. (2012) to use complimentary observations to directly constrain this effect on the data. We use catalogs of Luminous Red Galaxies (LRGs) and photometric galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) to measure the redshift-space power spectrum of LRGs, the cross-correlation of LRGs with the shapes of background photometric galaxies (galaxy-galaxy weak lensing), and the projected cross-correlation of LRGs with photometric galaxies having similar photometric redshifts to the LRG spectroscopic redshift. All of these measurements use a reconstructed halo field. While we use the position of each LRG for single LRG systems, we compare the measurements using different halo-center proxies for multiple-LRG systems (4.5 per cent of all the halos): the brightest LRG position (BLRG), the faintest LRG position...

  3. Large-scale bias of dark matter halos

    CERN Document Server

    Valageas, Patrick

    2010-01-01

    We build a simple analytical model for the bias of dark matter halos that applies to objects defined by an arbitrary density threshold, $200\\leq\\delta\\leq 1600$, and that provides accurate predictions from low-mass to high-mass halos. We point out that it is possible to build simple and efficient models, with no free parameter for the halo bias, by using integral constraints that govern the behavior of low-mass and typical halos, whereas the properties of rare massive halos are derived through explicit asymptotic approaches. We also describe how to take into account the impact of halo motions on their bias, using their linear displacement field. We obtain a good agreement with numerical simulations for the halo mass functions and large-scale bias at redshifts $0\\leq z \\leq 2.5$, for halos defined by nonlinear density threshold $200\\leq\\delta\\leq 1600$. We also evaluate the impact on the halo bias of two common approximations, i) neglecting halo motions, and ii) linearizing the halo two-point correlation.

  4. Historical halo displays as past weather indicator

    Science.gov (United States)

    Neuhäuser, Dagmar; Neuhäuser, Ralph

    2017-04-01

    Certain halo displays like the 22° circle were known to indicate specific weather pattern since millennia - as specified in Babylonian omina, Aristotle's Meteorology, farmers' weather lore, etc. Today, it is known that halo phenomena are due to refraction and reflection of sun and moon light in ice crystals in cirrus and cirrostratus, so that halo observations do indicate atmospheric conditions like temperature, humidity, pressure etc. in a few km height. The Astronomical Diaries of Babylonia have recorded both halo phenomena (circles, parhelia, etc.) and weather conditions (rain, clouds, etc.), so that we can use them to show statistically, whether, which and how fast halo phenomena are related to weather - for the last few centuries BC for Babylonia. We can then also compare the observations of Babylonian priests in the given BC epoch (without air and light pollution) with the last few decades of the modern epoch (with air and light pollution), where amateur halo observers have systematically recorded such phenomena (in Europe). Weather and climate are known to be partly driven by solar activity. Hence, one could also consider whether there is an indirect relation between halo displays as weather proxy and aurorae as solar activity proxy - if low solar activity leads to low pressure systems, one could expect more halos, preliminary studies show such a hint. For the last few decades, we have many halo observations, satellite imaging of the aurora oval, and many data on solar activity. A statistically sufficient amount of aurora and halo observations should be available for the historic time to investigate such a possible connection: halos were recorded very often in antiquity and the medieval times (as found in chronicles etc.), and modern scholarly catalogs of aurorae also often contain unrecognized halo displays.

  5. Evolutionary models for metal-poor low-mass stars lower main sequence of globular clusters and halo field stars

    CERN Document Server

    Baraffe, I; Allard, F; Hauschildt, P H; Baraffe, Isabelle; Chabrier, Gilles; Allard, France; Hauschildt, Peter

    1997-01-01

    We have performed evolutionary calculations of very-low-mass stars from 0.08 to 0.8 $\\msol$ for different metallicites from [M/H]= -2.0 to -1.0 and we have tabulated the mechanical, thermal and photometric characteristics of these models. The calculations include the most recent interior physics and improved non-grey atmosphere models. The models reproduce the entire main sequences of the globular clusters observed with the Hubble Space Telescope over the afore-mentioned range of metallicity. Comparisons are made in the WFPC2 Flight system including the F555, F606 and F814 filters, and in the standard Johnson-Cousins system. We examine the effects of different physical parameters, mixing-length, $\\alpha$-enriched elements, helium fraction, as well as the accuracy of the photometric transformations of the HST data into standard systems. We derive mass-effective temperature and mass-magnitude relationships and we compare the results with the ones obtained with different grey-like approximations. These latter ar...

  6. Statistical properties of the dark matter haloes of dwarf galaxies and correlations with the environment

    CERN Document Server

    Del Popolo, A

    2012-01-01

    According to the now strongly supported concordance $\\Lambda$CDM model, galaxies may be grossly described as a luminous component embedded in a dark matter halo. The density profile of these mass dominating haloes may be determined by N - body simulations which mimic the evolution of the tiny initial density perturbations during the process leading to the structures we observe today. Unfortunately, when the effect of baryons is taken into account, the situation gets much more complicated due to the difficulties in simulating their physics. As a consequence, a definitive prediction of how dark matter haloes should presently look like is still missing. We revisit here this issue from an observational point of view devoting our attention to dwarf galaxies. Being likely dark matter dominated, these systems are ideal candidates to investigate the present day halo density profiles and check whether dark matter related quantities correlate with the stellar ones or the environment. By fitting a large sample of well m...

  7. The response of dark matter haloes to elliptical galaxy formation: a new test for quenching scenarios

    CERN Document Server

    Dutton, Aaron A; Stinson, Gregory S; Gutcke, Thales A; Penzo, Camilla; Buck, Tobias

    2015-01-01

    We use cosmological hydrodynamical zoom-in simulations with the SPH code gasoline of four haloes of mass M_{200} \\sim 10^{13}\\Msun to study the response of the dark matter to elliptical galaxy formation. At z=2 the progenitor galaxies have stellar to halo mass ratios consistent with halo abundance matching, assuming a Salpeter initial mass function. However by z=0 the standard runs suffer from the well known overcooling problem, overpredicting the stellar masses by a factor of > 4. To mimic a suppressive halo quenching scenario, in our forced quenching (FQ) simulations, cooling and star formation are switched off at z=2. The resulting z=0 galaxies have stellar masses, sizes and circular velocities close to what is observed. Relative to the control simulations, the dark matter haloes in the FQ simulations have contracted, with central dark matter density slopes d\\log\\rho/d\\log r \\sim -1.5, showing that dry merging alone is unable to fully reverse the contraction that occurs at z>2. Simulations in the literatur...

  8. Stellar dynamics in the strong-lensing central galaxy of Abell 1201: a low stellar mass-to-light ratio, a large central compact mass and a standard dark matter halo

    Science.gov (United States)

    Smith, Russell J.; Lucey, John R.; Edge, Alastair C.

    2017-10-01

    We analyse the stellar kinematics of the z = 0.169 brightest cluster galaxy in Abell 1201, using integral field observations acquired with the Multi-Unit Spectroscopic Explorer on the Very Large Telescope. This galaxy has a gravitationally lensed arc located at unusually small radius (∼5 kpc), allowing us to constrain the mass distribution using lensing and stellar dynamical information over the same radial range. We measure a velocity dispersion profile which is nearly flat at σ ≈ 285 km s-1 in the inner ∼5 kpc, and then rises steadily to σ ≈ 360 km s-1 at ∼30 kpc. We analyse the kinematics using axisymmetric Jeans models, finding that the data require both a significant dark matter halo (to fit the rising outer profile) and a compact central component, with mass Mcen ≈ 2.5 × 1010 M⊙ (to fit the flat σ in the inner regions). The latter component could represent a supermassive black hole, in which case it would be among the largest known to date. Alternatively Mcen could describe excess mass associated with a gradient in the stellar mass-to-light ratio. Imposing a standard Navarro-Frenk-White (NFW) dark matter density profile, we recover a stellar mass-to-light ratio ϒ, which is consistent with a Milky Way-like initial mass function (IMF). By anchoring the models using the lensing mass constraint, we break the degeneracy between ϒ and the inner slope γ of the dark matter profile, finding γ = 1.0 ± 0.1, consistent with the NFW form. We show that our results are quite sensitive to the treatment of the central mass in the models. Neglecting Mcen biases the results towards both a heavier-than-Salpeter IMF and a shallower-than-NFW dark matter slope (γ ≈ 0.5).

  9. Halo formation and evolution: unifying physical properties with structure

    Science.gov (United States)

    Ernest, Alllan David; Collins, Matthew P.

    2015-08-01

    The assembly of matter in the universe proliferates a variety of structures with diverse properties. For example, massive halos of clusters of galaxies have temperatures often an order of magnitude or more higher than the individual galaxy halos within the cluster, or the temperatures of isolated galaxy halos. Giant spiral galaxies contain large quantities of both dark matter and hot gas while other structures like globular clusters appear to have little or no dark matter or gas. Still others, like the dwarf spheroidal galaxies have low gravity and little hot gas, but ironically contain some of the largest fractions of dark matter in the universe. Star forming rates (SFRs) also vary: compare for example the SFRs of giant elliptical galaxies, globular clusters, spiral and starburst galaxies. Furthermore there is evidence that the various structure types have existed over a large fraction of cosmic history. How can this array of variation in properties be reconciled with galaxy halo formation and evolution?We propose a model of halo formation [1] and evolution [2] that is consistent with both primordial nucleosynthesis (BBN) and the isotropies in the cosmic microwave background (CMB). The model uses two simple parameters, the total mass and size of a structure, to (1) explain why galaxies have the fractions of dark matter that they do (including why dwarf spheroidals are so dark matter dominated despite their weak gravity), (2) enable an understanding of the black hole-bulge/black hole-dark halo relations, (3) explain how fully formed massive galaxies can occur so early in cosmic history, (4) understand the connection between spiral and elliptical galaxies (5) unify the nature of globular clusters, dwarf spheroidal galaxies and bulges and (6) predict the temperatures of hot gas halos and understand how cool galaxy halos can remain stable in the hot environments of cluster-galaxy halos.[1] Ernest, A. D., 2012, in Prof. Ion Cotaescu (Ed) Advances in Quantum Theory, pp

  10. Red Galaxy Growth and the Halo Occupation Distribution

    CERN Document Server

    Brown, Michael J I; White, Martin; Dey, Arjun; Jannuzi, Buell T; Benson, Andrew J; Brand, Kate; Brodwin, Mark; Croton, Darren J

    2008-01-01

    We have traced the past 7 Gyr of red galaxy stellar mass growth within dark matter halos. We have determined the halo occupation distribution, which describes how galaxies reside within dark matter halos, using the observed luminosity function and clustering of 40,696 0.2halos host a red central galaxy, and this fraction increases with increasing halo mass. We do not observe any evolution of the relationship between red galaxy stellar mass and host halo mass, although we expect both galaxy stellar masses and halo masses to evolve over cosmic time. We find that the stellar mass contained within the red population has doubled since z=1, with the stellar mass within red satellite galaxies tripling over this redshift range. In cluster mass halos most of the stellar mass resides within satellite galaxies and the intra-cluster light, with a minority of the stellar mass residing within central galaxies. The stellar masses of the most luminous red central ...

  11. Effects of Angular Momentum on Halo Profiles

    CERN Document Server

    Lentz, Erik W; Rosenberg, Leslie J

    2016-01-01

    The near universality of DM halo density profiles provided by N-body simulations has proven to be robust against changes in total mass density, power spectrum, and some forms of initial velocity dispersion. In this letter we study the effects of coherently spinning up an isolated DM-only progenitor on halo structure. Halos with spins within several standard deviations of the simulated mean ($\\lambda \\lesssim 0.20$) produce profiles with negligible deviations from the universal form. Only when the spin becomes quite large ($\\lambda \\gtrsim 0.20$) do departures become evident. The angular momentum distribution also exhibits a near universal form, which is also independent of halo spin up to $\\lambda \\lesssim 0.20$. A correlation between these epidemic profiles and the presence of a strong bar in the virialized halo is also observed. These bar structures bear resemblance to the radial orbit instability in the rotationless limit.

  12. Conditions for halo occurrence

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, A.S.; Riisager, K.; Fedorov, D.V. [Inst. of Physics and Astronomy, Univ. of Arhus (Denmark); Garrido, E. [Inst. de Estructura de la Materia, CSIC, Madrid (Spain)

    2003-07-01

    We define quantum halos and apply the definition on many-body systems arriving at the conclusions that halos must have few cluster partitions, small binding energy, low angular momentum, small charge, low excitation energy. (orig.)

  13. The Redshift Evolution of LCDM Halo Parameters: Concentration, Spin, and Shape

    CERN Document Server

    Muñoz-Cuartas, J C; Gottlöber, S; Dutton, A A

    2010-01-01

    We present a detailed study of the redshift evolution of dark matter halo structural parameters in a LambdaCDM cosmology. We study the mass and redshift dependence of the concentration, shape and spin parameter in Nbody simulations spanning masses from 10^{10} Msun/h to 10^{15} Msun/h and redshifts from 0 to 2. We present a series of fitting formulas that accurately describe the time evolution of the concentration-mass relation since z=2. Using arguments based on the spherical collapse model we study the behaviour of the scale length of the density profile during the assembly history of haloes, obtaining physical insights on the origin of the observed time evolution of the concentration mass relation. We also investigate the evolution with redshift of dark matter halo shape and its dependence on mass. Within the studied redshift range the relation between halo shape and mass can be well fitted by a power law. Finally we show that although for z=0 the spin parameter is practically mass independent, at increasi...

  14. Mass and Angular Momentum in General Relativity

    CERN Document Server

    Jaramillo, J L

    2010-01-01

    We present an introduction to mass and angular momentum in General Relativity. After briefly reviewing energy-momentum for matter fields, first in the flat Minkowski case (Special Relativity) and then in curved spacetimes with or without symmetries, we focus on the discussion of energy-momentum for the gravitational field. We illustrate the difficulties rooted in the Equivalence Principle for defining a local energy-momentum density for the gravitational field. This leads to the understanding of gravitational energy-momentum and angular momentum as non-local observables that make sense, at best, for extended domains of spacetime. After introducing Komar quantities associated with spacetime symmetries, it is shown how total energy-momentum can be unambiguously defined for isolated systems, providing fundamental tests for the internal consistency of General Relativity as well as setting the conceptual basis for the understanding of energy loss by gravitational radiation. Finally, several attempts to formulate q...

  15. The Origin and Evolution of the Galaxy Mass-Metallicity Relation

    CERN Document Server

    Ma, Xiangcheng; Faucher-Giguere, Claude-Andre; Zolman, Nick; Muratov, Alexander L; Keres, Dusan; Quataert, Eliot

    2015-01-01

    We use high-resolution cosmological zoom-in simulations from the Feedback in Realistic Environment (FIRE) project to study the galaxy mass-metallicity relations (MZR) from z=0-6. These simulations include explicit models of the multi-phase ISM, star formation, and stellar feedback. The simulations cover halo masses Mhalo=10^9-10^13 Msun and stellar mass Mstar=10^4-10^11 Msun at z=0 and have been shown to produce many observed galaxy properties from z=0-6. For the first time, our simulations agree reasonably well with the observed mass-metallicity relations at z=0-3 for a broad range of galaxy masses. We predict the evolution of the MZR from z=0-6 as log(Zgas/Zsun)=12+log(O/H)-9.0=0.35[log(Mstar/Msun)-10]+0.93 exp(-0.43 z)-1.05 and log(Zstar/Zsun)=[Fe/H]-0.2=0.40[log(Mstar/Msun)-10]+0.67 exp(-0.50 z)-1.04, for gas-phase and stellar metallicity, respectively. Our simulations suggest that the evolution of MZR is associated with the evolution of stellar/gas mass fractions at different redshifts, indicating the ex...

  16. Theoretical Models of the Halo Occupation Distribution: Separating Central and Satellite Galaxies

    CERN Document Server

    Zheng, Z; Weinberg, D H; Benson, A J; Baugh, C M; Cole, S; Davé, R; Frenk, C S; Katz, N; Lacey, C G; Zheng, Zheng; Weinberg, David H; Benson, Andrew J; Baugh, Carlton M; Cole, Shaun; Dave, Romeel; Frenk, Carlos S; Katz, Neal; Lacey, Cedric G

    2004-01-01

    The halo occupation distribution (HOD) describes the relation between galaxies and dark matter at the level of individual dark matter halos. The properties of galaxies residing at the centers of halos differ from those of satellite galaxies because of differences in their formation histories. Using a smoothed particle hydrodynamics (SPH) simulation and a semi-analytic (SA) galaxy formation model, we examine the separate contributions of central and satellite galaxies to the HOD, more specifically to the probability P(N|M) that a halo of virial mass M contains N galaxies of a particular class. In agreement with earlier results for dark matter subhalos, we find that the mean occupation function for galaxies above a baryonic mass threshold can be approximated by a step function for central galaxies plus a power law for satellites, and that the distribution of satellite numbers is close to Poisson at fixed halo mass. For galaxy samples defined by different baryonic mass thresholds, there is a nearly linear relat...

  17. The formation of spiral galaxies: adiabatic compression with Young's algorithm and the relation of dark matter haloes to their primordial antecedents

    NARCIS (Netherlands)

    Katz, Harley; McGaugh, Stacy S.; Sellwood, J. A.; de Blok, W. J. G.

    We utilize Young's algorithm to model the adiabatic compression of the dark matter haloes of galaxies in the THINGS survey to determine the relationship between the halo fit to the rotation curve and the corresponding primordial halo prior to compression. Young's algorithm conserves radial action

  18. The evolution of the galaxy content of dark matter haloes

    CERN Document Server

    Contreras, S; Baugh, C M; Padilla, N; Norberg, P

    2016-01-01

    We use the halo occupation distribution (HOD) framework to characterise the predictions from two independent galaxy formation models for the galactic content of dark matter haloes and its evolution with redshift. Our galaxy samples correspond to a range of fixed number densities defined by stellar mass and span $0 \\le z \\le 3$. We find remarkable similarities between the model predictions. Differences arise at low galaxy number densities which are sensitive to the treatment of heating of the hot halo by active galactic nuclei. The evolution of the form of the HOD can be described in a relatively simple way, and we model each HOD parameter using its value at $z=0$ and an additional evolutionary parameter. In particular, we find that the ratio between the characteristic halo masses for hosting central and satellite galaxies can serve as a sensitive diagnostic for galaxy evolution models. Our results can be used to test and develop empirical studies of galaxy evolution and can facilitate the construction of mock...

  19. The evolution of the galaxy content of dark matter haloes

    Science.gov (United States)

    Contreras, S.; Zehavi, I.; Baugh, C. M.; Padilla, N.; Norberg, P.

    2017-03-01

    We use the halo occupation distribution (HOD) framework to characterize the predictions from two independent galaxy formation models for the galactic content of dark matter haloes and its evolution with redshift. Our galaxy samples correspond to a range of fixed number densities defined by stellar mass and span 0 ≤ z ≤ 3. We find remarkable similarities between the model predictions. Differences arise at low galaxy number densities which are sensitive to the treatment of heating of the hot halo by active galactic nuclei. The evolution of the form of the HOD can be described in a relatively simple way, and we model each HOD parameter using its value at z = 0 and an additional evolutionary parameter. In particular, we find that the ratio between the characteristic halo masses for hosting central and satellite galaxies can serve as a sensitive diagnostic for galaxy evolution models. Our results can be used to test and develop empirical studies of galaxy evolution, and can facilitate the construction of mock galaxy catalogues for future surveys.

  20. Halo detection via large-scale Bayesian inference

    Science.gov (United States)

    Merson, Alexander I.; Jasche, Jens; Abdalla, Filipe B.; Lahav, Ofer; Wandelt, Benjamin; Jones, D. Heath; Colless, Matthew

    2016-08-01

    We present a proof-of-concept of a novel and fully Bayesian methodology designed to detect haloes of different masses in cosmological observations subject to noise and systematic uncertainties. Our methodology combines the previously published Bayesian large-scale structure inference algorithm, HAmiltonian Density Estimation and Sampling algorithm (HADES), and a Bayesian chain rule (the Blackwell-Rao estimator), which we use to connect the inferred density field to the properties of dark matter haloes. To demonstrate the capability of our approach, we construct a realistic galaxy mock catalogue emulating the wide-area 6-degree Field Galaxy Survey, which has a median redshift of approximately 0.05. Application of HADES to the catalogue provides us with accurately inferred three-dimensional density fields and corresponding quantification of uncertainties inherent to any cosmological observation. We then use a cosmological simulation to relate the amplitude of the density field to the probability of detecting a halo with mass above a specified threshold. With this information, we can sum over the HADES density field realisations to construct maps of detection probabilities and demonstrate the validity of this approach within our mock scenario. We find that the probability of successful detection of haloes in the mock catalogue increases as a function of the signal to noise of the local galaxy observations. Our proposed methodology can easily be extended to account for more complex scientific questions and is a promising novel tool to analyse the cosmic large-scale structure in observations.

  1. The relation between star formation rate and stellar mass of galaxies at z $\\sim$ 1-4

    CERN Document Server

    Katsianis, A; Wyithe, J S B

    2015-01-01

    The relation between the Star Formation Rate (SFR) and stellar mass (${\\rm M}_{\\star}$) of galaxies represents a fundamental constraint on galaxy formation. However, the observed amplitude of the star formation rate - stellar mass relation has not been successfully reproduced in simulations, indicating either that the halo accretion history and baryonic physics are poorly understood or that observations contain biases. In this paper, we examine the evolution of the SFR$-{\\rm M}_{\\star}$ relation of $z\\sim 1-4 $ galaxies and display the inconsistency between observed relations that are obtained using different techniques. We employ cosmological hydrodynamic simulations from various groups and compare these with a range of observations. The comparison suggests that using Spectral Energy Distributions (SEDs) to estimate star formation rates, dust corrections and stellar masses produces the most reliable SFR$-{\\rm M}_{\\star}$ relations. On the contrary, the combination of IR and UV luminosities (UV+IR) overpredic...

  2. A general relativistic approach to the Navarro Frenk White galactic halos

    Science.gov (United States)

    Matos, Tonatiuh; Núñez, Darío; Sussman, Roberto A.

    2004-11-01

    Although galactic dark matter halos are basically Newtonian structures, the study of their interplay with large-scale cosmic evolution and with relativistic effects, such as gravitational lenses, quintessence sources or gravitational waves, makes it necessary to obtain adequate relativistic descriptions for these self-gravitating systems. With this purpose in mind, we construct a post-Newtonian fluid framework for the 'Navarro Frenk White' (NFW) models of galactic halos that follow from N-body numerical simulations. Since these simulations are unable to resolve regions very near the halo centre, the extrapolation of the fitting formula leads to a spherically averaged 'universal' density profile that diverges at the origin. We remove this inconvenient feature by replacing a small central region of the NFW halo with an interior Schwarzschild solution with constant density, continuously matched to the remaining NFW spacetime. A model of a single halo, as an isolated object with finite mass, follows by smoothly matching the NFW spacetime to a Schwarzschild vacuum exterior along the virial radius, the physical 'cut-off' customarily imposed, as the mass associated with NFW profiles diverges asymptotically. Numerical simulations assume weakly interacting collisionless particles, hence we suggest that NFW halos approximately satisfy an 'ideal gas' type of equation of state, where mass-density is the dominant rest-mass contribution to matter-energy, with the internal energy contribution associated with an anisotropic kinetic pressure. We show that, outside the central core, this pressure and the mass density roughly satisfy a polytropic relation. Since stellar polytropes are the equilibrium configurations in Tsallis' non-extensive formalism of statistical mechanics, we argue that NFW halos might provide a rough empirical estimate of the free parameter q of Tsallis' formalism.

  3. PAHs in the Halo of NGC 5529

    CERN Document Server

    Irwin, J A; Parkin, T; Madden, S

    2007-01-01

    We present sensitive ISO $\\lambda 6.7 \\mu$m observations of the edge-on galaxy, NGC 5529, finding an extensive MIR halo around NGC 5529. The emission is dominated by PAHs in this band. The PAH halo has an exponential scale height of 3.7 kpc but can still be detected as far as $\\approx 10$ kpc from the plane to the limits of the high dynamic range (1770/1) data. This is the most extensive PAH halo yet detected in a normal galaxy. This halo shows substructure and the PAHs likely originate from some type of disk outflow. PAHs are long-lived in a halo environment and therefore continuous replenishment from the disk is not required (unless halo PAHs are also being destroyed or removed), consistent with the current low SFR of the galaxy. The PAHs correlate spatially with halo H$\\alpha$ emission, previously observed by Miller & Veilleux (2003); both components are likely excited/ionized by in-disk photons that are leaking into the halo. The presence of halo gas may be related to the environment of NGC 5529 which...

  4. Progress in understanding halo current at JET

    Science.gov (United States)

    Riccardo, V.; Arnoux, G.; Beaumont, P.; Hacquin, S.; Hobirk, J.; Howell, D.; Huber, A.; Joffrin, E.; Koslowski, R.; Lam, N.; Leggate, H.; Rachlew, E.; Sergienko, G.; Stephen, A.; Todd, T.; Zerbini, M.; Delogu, R.; Grando, L.; Marcuzzi, D.; Peruzzo, S.; Pomaro, N.; Sonato, P.; JET EFDA Contributors

    2009-05-01

    The poloidal distribution of the halo current density on the top dump plate in JET can now be measured thanks to a new set of Rogowskii coils. These are the first measurements in JET able to offer an insight in the width of the halo current interaction with the wall. Therefore they offer both validation of the assumption made for JET disruption design criteria and one additional point in the extrapolation of the expected halo current width, and hence halo current density (and related local electro-mechanical loads on in-vessel components) for ITER. During upward events, the measured current density is consistent with the measured total poloidal halo current. The halo footprint extends over most of the upper dump plate, converting to a halo current flux tube width of ~100 mm. A set of four toridal field pick-up coils installed 90° apart now allows a more accurate measurement of the poloidal halo current, in particular its toroidal peaking factor, and direct comparison between halo and plasma asymmetries.

  5. Analytical halo model of galactic conformity

    Science.gov (United States)

    Pahwa, Isha; Paranjape, Aseem

    2017-09-01

    We present a fully analytical halo model of colour-dependent clustering that incorporates the effects of galactic conformity in a halo occupation distribution framework. The model, based on our previous numerical work, describes conformity through a correlation between the colour of a galaxy and the concentration of its parent halo, leading to a correlation between central and satellite galaxy colours at fixed halo mass. The strength of the correlation is set by a tunable 'group quenching efficiency', and the model can separately describe group-level correlations between galaxy colour (1-halo conformity) and large-scale correlations induced by assembly bias (2-halo conformity). We validate our analytical results using clustering measurements in mock galaxy catalogues, finding that the model is accurate at the 10-20 per cent level for a wide range of luminosities and length-scales. We apply the formalism to interpret the colour-dependent clustering of galaxies in the Sloan Digital Sky Survey (SDSS). We find good overall agreement between the data and a model that has 1-halo conformity at a level consistent with previous results based on an SDSS group catalogue, although the clustering data require satellites to be redder than suggested by the group catalogue. Within our modelling uncertainties, however, we do not find strong evidence of 2-halo conformity driven by assembly bias in SDSS clustering.

  6. Estimating the geoeffectiveness of halo CMEs from associated solar and IP parameters using neural networks

    Directory of Open Access Journals (Sweden)

    J. Uwamahoro

    2012-06-01

    Full Text Available Estimating the geoeffectiveness of solar events is of significant importance for space weather modelling and prediction. This paper describes the development of a neural network-based model for estimating the probability occurrence of geomagnetic storms following halo coronal mass ejection (CME and related interplanetary (IP events. This model incorporates both solar and IP variable inputs that characterize geoeffective halo CMEs. Solar inputs include numeric values of the halo CME angular width (AW, the CME speed (Vcme, and the comprehensive flare index (cfi, which represents the flaring activity associated with halo CMEs. IP parameters used as inputs are the numeric peak values of the solar wind speed (Vsw and the southward Z-component of the interplanetary magnetic field (IMF or Bs. IP inputs were considered within a 5-day time window after a halo CME eruption. The neural network (NN model training and testing data sets were constructed based on 1202 halo CMEs (both full and partial halo and their properties observed between 1997 and 2006. The performance of the developed NN model was tested using a validation data set (not part of the training data set covering the years 2000 and 2005. Under the condition of halo CME occurrence, this model could capture 100% of the subsequent intense geomagnetic storms (Dst ≤ −100 nT. For moderate storms (−100 < Dst ≤ −50, the model is successful up to 75%. This model's estimate of the storm occurrence rate from halo CMEs is estimated at a probability of 86%.

  7. How are galaxies assigned to halos? Searching for assembly bias in the SDSS galaxy clustering

    CERN Document Server

    Vakili, Mohammadjavad

    2016-01-01

    Clustering of dark matter halos has been shown to depend on halo properties beyond mass such as halo concentration, a phenomenon referred to as halo assembly bias. Standard halo occupation modeling (HOD) in large scale structure studies assumes that halo mass alone is sufficient in characterizing the connection between galaxies and halos. Modeling of galaxy clustering can face systematic effects if the number or properties of galaxies are correlated with other halo properties. Using the Small MultiDark-Planck high resolution $N$-body simulation and the measurements of the projected two-point correlation function and the number density of Sloan Digital Sky Survey (SDSS) DR7 main galaxy sample, we investigate the extent to which the dependence of halo occupation on halo concentration can be constrained, and to what extent allowing for this dependence can improve our modeling of galaxy clustering. Given the SDSS clustering data, our constraints on HOD with assembly bias, suggests that satellite population is not...

  8. GalICS II: the [alpha/Fe]-mass relation in elliptical galaxies

    CERN Document Server

    Pipino, A; Thomas, D; Silk, J; Kaviraj, S

    2008-01-01

    We aim at reproducing the mass- and sigma-[alpha/Fe] relations in the stellar populations of early-type galaxies by means of a cosmologically motivated assembly history for the spheroids. We implement a detailed treatment for the chemical evolution of H, He, O and Fe in GalICS, a semi-analytical model for galaxy formation which successfully reproduces basic low- and high-redshift galaxy properties. The contribution of supernovae (both type Ia and II) as well as low- and intermediate-mass stars to chemical feedback are taken into account. We find that this chemically improved GalICS does not produce the observed mass- and sigma-[alpha/Fe] relations. The slope is too shallow and scatter too large, in particular in the low and intermediate mass range. The model shows significant improvement at the highest masses and velocity dispersions, where the predicted [alpha/Fe] ratios are now marginally consistent with observed values. We show that this result comes from the implementation of AGN (plus halo) quenching of ...

  9. On the statistical characteristics of radio-loud and radio-quiet halo coronal mass ejections and their associated flares during solar cycles 23 and 24

    Science.gov (United States)

    Mittal, Nishant; Sharma, Joginder; Verma, Virendar Kumar; Garg, Vijay

    2016-08-01

    We have studied the characteristics of radio-loud (RL) and radio-quiet (RQ) front side halo coronal mass ejections (HCMEs) (angular width 360°) observed between the time period years 1996-2014. RL-HCMEs are associated with type II radio bursts, while RQ-HCMEs are not associated with type II radio bursts. CMEs near the Sun in the interplanetary medium associated with radio bursts also affect the magnetosphere. The type II radio burst data was observed by WIND/WAVES instrument and HCMEs were observed by LASCO/ SOHO instruments. In our study, we have examined the properties of RL-HCMEs and RQ-HCMEs and found that RL-HCMEs follow the solar cycle variation. Our study also shows that the 26% of slow speed HCMEs and 82% of fast speed HCMEs are RL. The average speed of RL-HCMEs and RQ-HCMEs are 1370 km/s and 727 km/s, respectively. Most of the RQ-HCMEs occur around the solar disc center while most of RL-HCMEs are uniformly distributed across the solar disc. The mean value of acceleration of RL-HCMEs is more than twice that of RQ-HCMEs and mean value of deceleration of RL- HCMEs is very small compare to RQ-HCMEs events. It is also found that RQ-HCMEs events are associated with C- and M-class of SXR flares, while RL-HCMEs events are associated with M and X-class of SXR flares, which indicates that the RQ-HCMEs are less energetic than the RL-HCMEs. We have also discussed the various results obtained in present investigation in view of recent scenario of solar physics.

  10. Detection of the Splashback Radius and Halo Assembly Bias of Massive Galaxy Clusters

    Science.gov (United States)

    More, Surhud; Miyatake, Hironao; Takada, Masahiro; Diemer, Benedikt; Kravtsov, Andrey V.; Dalal, Neal K.; More, Anupreeta; Murata, Ryoma; Mandelbaum, Rachel; Rozo, Eduardo; Rykoff, Eli S.; Oguri, Masamune; Spergel, David N.

    2016-07-01

    We show that the projected number density profiles of Sloan Digital Sky Survey photometric galaxies around galaxy clusters display strong evidence for the splashback radius, a sharp halo edge corresponding to the location of the first orbital apocenter of satellite galaxies after their infall. We split the clusters into two subsamples with different mean projected radial distances of their members, , at fixed richness and redshift. The sample with smaller has a smaller ratio of the splashback radius to the traditional halo boundary {R}{{200m}} than the subsample with larger , indicative of different mass accretion rates for these subsamples. The same subsamples were recently used by Miyatake et al. to show that their large-scale clustering differs despite their similar weak lensing masses, demonstrating strong evidence for halo assembly bias. We expand on this result by presenting a 6.6σ difference in the clustering amplitudes of these samples using cluster-photometric galaxy cross-correlations. This measurement is a clear indication that halo clustering depends on parameters other than halo mass. If is related to the mass assembly history of halos, the measurement is a manifestation of the halo assembly bias. However, our measured splashback radii are smaller, while the strength of the assembly bias signal is stronger, than the predictions of collisionless Λ cold dark matter simulations. We show that dynamical friction, cluster mis-centering, or projection effects are not likely to be the sole source of these discrepancies. However, further investigations regarding unknown catastrophic weak lensing or cluster identification systematics are warranted.

  11. Smooth halos in the cosmic web

    CERN Document Server

    Gaite, Jose

    2014-01-01

    Dark matter halos can be defined as smooth distributions of dark matter placed in a non-smooth cosmic web structure. This definition of halos demands a precise definition of smoothness and a characterization of the manner in which the transition from smooth halos to the cosmic web takes place. We introduce entropic measures of smoothness, related to measures of equality previously used in economy and with the advantage of being connected with standard methods of multifractal analysis already used for characterizing the cosmic web structure in $N$-body simulations. These entropic measures provide us with a quantitative description of the transition from the small scales portrayed as a distribution of halos to the larger scales portrayed as a cosmic web and, therefore, allow us to assign definite sizes to halos. However, these "smoothness sizes" have no direct relation to the virial radii.

  12. Swirling around filaments: are large-scale structure vortices spinning up dark haloes?

    Science.gov (United States)

    Laigle, C.; Pichon, C.; Codis, S.; Dubois, Y.; Le Borgne, D.; Pogosyan, D.; Devriendt, J.; Peirani, S.; Prunet, S.; Rouberol, S.; Slyz, A.; Sousbie, T.

    2015-01-01

    The kinematic analysis of dark matter and hydrodynamical simulations suggests that the vorticity in large-scale structure is mostly confined to, and predominantly aligned with, their filaments, with an excess of probability of 20 per cent to have the angle between vorticity and filaments direction lower than 60° relative to random orientations. The cross-sections of these filaments are typically partitioned into four quadrants with opposite vorticity sign, arising from multiple flows, originating from neighbouring walls. The spins of haloes embedded within these filaments are consistently aligned with this vorticity for any halo mass, with a stronger alignment for the most massive structures up to an excess of probability of 165 per cent. The global geometry of the flow within the cosmic web is therefore qualitatively consistent with a spin acquisition for smaller haloes induced by this large-scale coherence, as argued in Codis et al. In effect, secondary anisotropic infall (originating from the vortex-rich filament within which these lower-mass haloes form) dominates the angular momentum budget of these haloes. The transition mass from alignment to orthogonality is related to the size of a given multi-flow region with a given polarity. This transition may be reconciled with the standard tidal torque theory if the latter is augmented so as to account for the larger scale anisotropic environment of walls and filaments.

  13. Mapping stellar content to dark matter halos using galaxy clustering and galaxy-galaxy lensing in the SDSS DR7

    CERN Document Server

    Zu, Ying

    2015-01-01

    The mapping between the distributions of the observed galaxy stellar mass and the underlying dark matter halos provides the crucial link from theories of large-scale structure formation to interpreting the complex phenomena of galaxy formation and evolution. We develop a novel statistical method, based on the Halo Occupation Distribution model (HOD), to solve for this mapping by jointly fitting the galaxy clustering and the galaxy-galaxy lensing measured from the Sloan Digital Sky Survey (SDSS). The method, called the iHOD model, extracts maximum information from the survey by including ~80% more galaxies than the traditional HOD methods, and takes into account the incompleteness of the stellar mass samples in a statistically consistent manner. The derived stellar-to-halo mass relation not only explains the clustering and lensing of SDSS galaxies over almost four decades in stellar mass, but also successfully predicts the stellar mass functions observed in SDSS. Due to its capability of modelling significantl...

  14. The shapes and alignments of dark matter halos

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Michael D. [Lawrence Livermore National Laboratory, P.O. Box 808 L-210, Livermore, CA 94551-0808 (United States); Frenk, Carlos S.; Cole, Shaun, E-mail: schneider42@llnl.gov, E-mail: c.s.frenk@durham.ac.uk, E-mail: shaun.cole@durham.ac.uk [Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham, DH1 3LE (United Kingdom)

    2012-05-01

    We present measurements of the triaxial dark matter halo shapes and alignment correlation functions in the Millennium and Millennium-2 dark matter N-body simulations. These two simulations allow us to measure the distributions of halo shapes down to 10% of the virial radius over a halo mass range of 6 × 10{sup 9}–2 × 10{sup 14} h{sup −1}M{sub s}un. We largely confirm previous results on the distributions of halo axis ratios as a function of halo mass, but we find that the median angle between halo major axes at different halo radii can vary by a factor of 2 between the Millennium-1 and 2 simulations because of the different mass resolution. Thus, error in the shape determinations from limited resolution is potentially degenerate with the misalignment of halo inner and outer shapes used to constrain Brightest Cluster Galaxy alignments in previous works. We also present simplifying parameterizations for the 3-D halo-mass alignment correlation functions that are necessary ingredients for triaxial halo models of large-scale structure and models of galaxy intrinsic alignments as contaminants for cosmic shear surveys. We measure strong alignments between halos of all masses and the surrounding dark matter overdensities out to several tens of h{sup −1} Mpc, in agreement with observed shear-galaxy and cluster shape correlations. We use these measurements to forecast the contribution to the weak lensing signal around galaxy clusters from correlated mass along the line-of-sight. For prolate clusters with major axes aligned with the line-of-sight the fraction of the weak lensing signal from mass external to the cluster can be twice that predicted if the excess halo alignment correlation is assumed to be zero.

  15. Halo and subhalo demographics with Planck cosmological parameters: Bolshoi-Planck and MultiDark-Planck simulations

    Science.gov (United States)

    Rodríguez-Puebla, Aldo; Behroozi, Peter; Primack, Joel; Klypin, Anatoly; Lee, Christoph; Hellinger, Doug

    2016-10-01

    We report and provide fitting functions for the abundance of dark matter haloes and subhaloes as a function of mass, circular velocity, and redshift from the new Bolshoi-Planck and MultiDark-Planck ΛCDM cosmological simulations, based on the Planck parameters. We also report halo mass accretion rates and concentrations. We show that the higher cosmological matter density of the Planck parameters compared with the WMAP parameters leads to higher abundance of massive haloes at high redshifts. We find that the median halo spin parameter {λ _B}= J(√{2}M_virR_virV_vir)^{-1} is nearly independent of redshift, leading to predicted evolution of galaxy sizes that is consistent with observations, while the significant decrease with redshift in median {λ _P}= J|E|^{-1/2}G^{-1}M^{-5/2} predicts more decrease in galaxy sizes than is observed. Using the Tully-Fisher and Faber-Jackson relations between galaxy velocity and mass, we show that a simple model of how galaxy velocity is related to halo maximum circular velocity leads to increasing overprediction of cosmic stellar mass density as redshift increases beyond z ˜ 1, implying that such velocity-mass relations must change at z ≳ 1. By making a realistic model of how observed galaxy velocities are related to halo circular velocity, we show that recent optical and radio observations of the abundance of galaxies are in good agreement with our ΛCDM simulations. Our halo demographics are based on updated versions of the ROCKSTAR and CONSISTENT TREES codes, and this paper includes appendices explaining all of their outputs. This paper is an introduction to a series of related papers presenting other analyses of the Bolshoi-Planck and MultiDark-Planck simulations.

  16. Major Mergers Going Notts: Challenges for Modern Halo Finders

    CERN Document Server

    Behroozi, Peter; Pearce, Frazer R; Elahi, Pascal; Han, Jiaxin; Lux, Hanni; Mao, Yao-Yuan; Muldrew, Stuart I; Potter, Doug; Srisawat, Chaichalit

    2015-01-01

    Merging haloes with similar masses (i.e., major mergers) pose significant challenges for halo finders. We compare five halo finding algorithms' (AHF, HBT, Rockstar, SubFind, and VELOCIraptor) recovery of halo properties for both isolated and cosmological major mergers. We find that halo positions and velocities are often robust, but mass biases exist for every technique. The algorithms also show strong disagreement in the prevalence and duration of major mergers, especially at high redshifts (z>1). This raises significant uncertainties for theoretical models that require major mergers for, e.g., galaxy morphology changes, size changes, or black hole growth, as well as for finding Bullet Cluster analogues. All finders not using temporal information also show host halo and subhalo relationship swaps over successive timesteps, requiring careful merger tree construction to avoid problematic mass accretion histories. We suggest that future algorithms should combine phase-space and temporal information to avoid the...

  17. Comparison of clustering properties of observed objects and dark matter halos on different mass and spatial scales

    CERN Document Server

    Tikhonov, A V; Gottlöber, S; Yepes, G

    2008-01-01

    We investigate the large-scale distribution of galaxy clusters taken from several X-ray catalogs. Different statistics of clustering like the conditional correlation function (CCF) and the minimal spanning tree (MST) as well as void statistics were used. Clusters show two distinct regimes of clustering: 1) on scales of superclusters (~40/h Mpc) the CCF is represented by a power law; 2) on larger scales a gradual transition to homogeneity (~100/h Mpc) is observed. We also present the correlation analysis of the galaxy distribution taken from DR6 SDSS main galaxy database. In case of galaxies the limiting scales of the different clustering regimes are 1)10-15/h Mpc; 2) 40-50/h Mpc. The differences in the characteristic scales and scaling exponents of the cluster and galaxy distribution can be naturally explained within the theory of biased structure formation. We compared the density contrasts of inhomogeneities in the cluster and galaxy distributions in the SDSS region. The estimation of the relative cluster-g...

  18. A halo model for cosmological neutral hydrogen : abundances and clustering

    CERN Document Server

    Padmanabhan, Hamsa; Amara, Adam

    2016-01-01

    We extend the results of previous analyses towards constraining the abundance and clustering of post-reionization ($z \\sim 0-5$) neutral hydrogen (HI) systems using a halo model framework. We work with a comprehensive HI dataset including the small-scale clustering, column density and mass function of HI galaxies at low redshifts, intensity mapping measurements at intermediate redshifts and the UV/optical observations of Damped Lyman Alpha (DLA) systems at higher redshifts. We use a Markov Chain Monte Carlo (MCMC) approach to constrain the parameters of the best-fitting models, both for the HI-halo mass relation and the HI radial density profile. We find that a radial exponential profile results in a good fit to the low-redshift HI observations, including the clustering and the column density distribution. The form of the profile is also found to match the high-redshift DLA observations, when used in combination with a three-parameter HI-halo mass relation and a redshift evolution in the HI concentration. The...

  19. Evolution of the atomic and molecular gas content of galaxies in dark matter haloes

    CERN Document Server

    Popping, G; Peeples, M S

    2014-01-01

    We present a semi-empirical model to infer the atomic and molecular hydrogen content of galaxies as a function of halo mass and time. Our model combines the SFR-halo mass-redshift relation (constrained by galaxy abundances) with inverted SFR-surface density relations to infer galaxy H I and H2 masses. We present gas scaling relations, gas fractions, and mass functions from z = 0 to z = 3 and the gas properties of galaxies as a function of their host halo masses. Predictions of our work include: 1) there is a ~ 0.2 dex decrease in the H I mass of galaxies as a function of their stellar mass since z = 1.5, whereas the H2 mass of galaxies decreases by > 1 dex over the same period. 2) galaxy cold gas fractions and H2 fractions decrease with increasing stellar mass and time. Galaxies with M* > 10^10 Msun are dominated by their stellar content at z < 1, whereas less-massive galaxies only reach these gas fractions at z = 0. We find the strongest evolution in relative gas content at z < 1.5. 3) the SFR to gas m...

  20. Neutron Star Mergers as the Origin of r-Process Elements in the Galactic Halo Based on the Sub-halo Clustering Scenario

    CERN Document Server

    Ishimaru, Yuhri; Prantzos, Nikos

    2015-01-01

    Binary mergers (NSMs) of double neutron star (and black hole-neutron star) systems are suggested to be major sites of r-process elements in the Galaxy by recent hydrodynamical and nucleosynthesis studies. It has been pointed out, however, that the estimated long lifetimes of neutron star binaries are in conflict with the presence of r-process-enhanced halo stars at metallicities as low as [Fe/H] ~ -3. To resolve this problem, we examine the role of NSMs in the early Galactic chemical evolution on the assumption that the Galactic halo was formed from merging sub-halos. We present simple models for the chemical evolution of sub-halos with total final stellar masses between 10^4 M_solar and 2 x 10^8 M_solar. Typical lifetimes of compact binaries are assumed to be 100 Myr (for 95% of their population) and 1 Myr (for 5%), according to recent binary population synthesis studies. The resulting metallcities of sub-halos and their ensemble are consistent with the observed mass-metallicity relation of dwarf galaxies in...

  1. Inhomogeneous chemical enrichment in the Galactic Halo

    Science.gov (United States)

    Kobayashi, Chiaki

    2016-08-01

    In a galaxy, chemical enrichment takes place in an inhomogeneous fashion, and the Galactic Halo is one of the places where the inhomogeneous effects are imprinted and can be constrained from observations. I show this using my chemodynamical simulations of Milky Way type galaxies. The scatter in the elemental abundances originate from radial migration, merging/accretion of satellite galaxies, local variation of star formation and chemical enrichment, and intrinsic variation of nucleosynthesis yields. In the simulated galaxies, there is no strong age-metallicity relation. This means that the most metal-poor stars are not always the oldest stars, and can be formed in chemically unevolved clouds at later times. The long-lifetime sources of chemical enrichment such as asymptotic giant branch stars or neutron star mergers can contribute at low metallicities. The intrinsic variation of yields are important in the early Universe or metal-poor systems such as in the Galactic halo. The carbon enhancement of extremely metal-poor (EMP) stars can be best explained by faint supernovae, the low [α/Fe] ratios in some EMP stars naturally arise from low-mass (~ 13 - 15M ⊙) supernovae, and finally, the [α/Fe] knee in dwarf spheroidal galaxies can be produced by subclasses of Type Ia supernovae such as SN 2002cx-like objects and sub-Chandrasekhar mass explosions.

  2. Weak lensing measurement of the mass-richness relation of SDSS redMaPPer clusters

    Science.gov (United States)

    Simet, Melanie; McClintock, Tom; Mandelbaum, Rachel; Rozo, Eduardo; Rykoff, Eli; Sheldon, Erin; Wechsler, Risa H.

    2017-04-01

    We perform a measurement of the mass-richness relation of the redMaPPer galaxy cluster catalogue using weak lensing data from the Sloan Digital Sky Survey (SDSS). We have carefully characterized a broad range of systematic uncertainties, including shear calibration errors, photo-z biases, dilution by member galaxies, source obscuration, magnification bias, incorrect assumptions about cluster mass profiles, cluster centring, halo triaxiality and projection effects. We also compare measurements of the lensing signal from two independently produced shear and photometric redshift catalogues to characterize systematic errors in the lensing signal itself. Using a sample of 5570 clusters from 0.1 ≤ z ≤ 0.33, the normalization of our power-law mass versus λ relation is log10[M200m/h-1 M⊙] = 14.344 ± 0.021 (statistical) ±0.023 (systematic) at a richness λ = 40, a 7 per cent calibration uncertainty, with a power-law index of 1.33^{+0.09}_{-0.10} (1σ). The detailed systematics characterization in this work renders it the definitive weak lensing mass calibration for SDSS redMaPPer clusters at this time.

  3. A Halo Model of Local IRAS Galaxies Selected at 60 Micron Using Conditional Luminosity Functions

    CERN Document Server

    Wang, Lingyu; Oliver, Seb

    2010-01-01

    Using conditional luminosity functions (CLFs) which encode the luminosity distribution of galaxies as a function of halo mass, we construct a halo model of IRAS galaxies selected at 60 micron. An abundance matching technique is used to link galaxy luminosity to the host halo mass. The shape of the mass - light relation at 60 micron is different from those derived at r-, K- and B-band. This is because the 60 micron LF can not be fitted by a Schechter function with a sharp exponential cutoff. We then seek the parameters in the CLFs that best fit the LF and power spectrum. We find that the predicted galaxy bias as a function of L60 from the best-fit model agrees well with the clustering measurements. At the faint end of the LF where quiescent star-forming galaxies dominate, most IRAS galaxies are central galaxies in halos of M >~ 10^{10} h^{-1} M_sun but a non-negligible fraction are satellites typically hosted in more massive halos. The majority of IRAS galaxies with L60 >~ 10^{10} h^{-2} L_sun are M82 type sta...

  4. The initial conditions and evolution of isolated galaxy models: effects of the hot gas halo

    CERN Document Server

    Hwang, Jeong-Sun; Choi, Jun-Hwan

    2013-01-01

    We construct several Milky Way-like galaxy models containing a gas halo (as well as gaseous and stellar disks, a dark matter halo, and a stellar bulge) following either an isothermal or an NFW density profile with varying mass and initial spin. In addition, galactic winds associated with star formation are tested in some of the simulations. We evolve these isolated galaxy models using the GADGET-3 $N$-body/hydrodynamic simulation code, paying particular attention to the effects of the gas halo on the evolution. We find that the evolution of the models is strongly affected by the adopted gas halo component. The model without a gas halo shows an increasing star formation rate (SFR) at the beginning of the simulation for some hundreds of millions of years and then a continuously decreasing rate to the end of the run at 3 Gyr. On the other hand, the SFRs in the models with a gas halo emerge to be either relatively flat throughout the simulations or increasing over a gigayear and then decreasing to the end. The mo...

  5. The ROCKSTAR Phase-space Temporal Halo Finder and the Velocity Offsets of Cluster Cores

    Science.gov (United States)

    Behroozi, Peter S.; Wechsler, Risa H.; Wu, Hao-Yi

    2013-01-01

    We present a new algorithm for identifying dark matter halos, substructure, and tidal features. The approach is based on adaptive hierarchical refinement of friends-of-friends groups in six phase-space dimensions and one time dimension, which allows for robust (grid-independent, shape-independent, and noise-resilient) tracking of substructure; as such, it is named ROCKSTAR (Robust Overdensity Calculation using K-Space Topologically Adaptive Refinement). Our method is massively parallel (up to 105 CPUs) and runs on the largest current simulations (>1010 particles) with high efficiency (10 CPU hours and 60 gigabytes of memory required per billion particles analyzed). A previous paper has shown ROCKSTAR to have excellent recovery of halo properties; we expand on these comparisons with more tests and higher-resolution simulations. We show a significant improvement in substructure recovery compared to several other halo finders and discuss the theoretical and practical limits of simulations in this regard. Finally, we present results that demonstrate conclusively that dark matter halo cores are not at rest relative to the halo bulk or substructure average velocities and have coherent velocity offsets across a wide range of halo masses and redshifts. For massive clusters, these offsets can be up to 350 km s-1 at z = 0 and even higher at high redshifts. Our implementation is publicly available at http://code.google.com/p/rockstar.

  6. Mass relations among quarks and/or leptons

    CERN Document Server

    Gilani, A H S

    2005-01-01

    The mass relations among respective quark family members are predicted and similar mass relation for the lepton family member are obtained. The volume of the volume element is also calculated which is (3/2)^(1/2).

  7. Mass-radius relations of white dwarfs at finite temperatures

    OpenAIRE

    Boshkayev, Kuantay; Rueda, Jorge A.; Ruffini, Remo; Zhami, Bakytzhan; Kalymova, Zhanerke; Balgimbekov, Galymdin

    2016-01-01

    We construct mass-radius relations of white dwarfs taking into account the effects of rotation and finite temperatures. We compare and contrast the theoretical mass-radius relations with observational data.

  8. Negative Point Mass Singularities in General Relativity

    CERN Document Server

    Robbins, Nicholas

    2010-01-01

    First we review the definition of a negative point mass singularity. Then we examine the gravitational lensing effects of these singularities in isolation and with shear and convergence from continuous matter. We review the Inverse Mean Curvature Flow and use this flow to prove some new results about the mass of a singularity, the ADM mass of the manifold, and the capacity of the singularity. We describe some particular examples of these singularities that exhibit additional symmetries.

  9. HaloSat - A CubeSat to Study the Hot Galactic Halo

    Science.gov (United States)

    Kaaret, Philip

    2017-01-01

    Observations of the nearby universe fail to locate about half of the baryons observed in the early universe. The missing baryons may be in hot galactic halos. HaloSat is a CubeSat designed to map oxygen line emission (O VII and O VIII) around the Milky Way in order to constrain the mass and spatial distribution of hot gas in the halo. HaloSat has a grasp competitive with current X-ray observatories. Its observing program will be optimized to minimize contributions from solar wind charge exchange (SWCX) emission that limit the accuracy of current measurements. We will describe the HaloSat mission concept, progress towards its implementation, and plans for archiving and distribution of the data.

  10. Mass relations among family members of quarks and leptons

    CERN Document Server

    Gilani, A H S

    2005-01-01

    The various mass relations among members of quark and lepton families are given. Three mass relations for the charm, beauty, and top quark family members are given and three mass relations for the electron, muon, and tau lepton family members are presented.

  11. Strong lensing in the inner halo of galaxy clusters

    Science.gov (United States)

    Saez, C.; Campusano, L. E.; Cypriano, E. S.; Sodré, L.; Kneib, J.-P.

    2016-08-01

    We present an axially symmetric formula to calculate the probability of finding gravitational arcs in galaxy clusters, being induced by their massive dark matter haloes, as a function of clusters redshifts and virial masses. The formula includes the ellipticity of the clusters dark matter potential by using a pseudo-elliptical approximation. The probabilities are calculated and compared for two dark matter halo profiles, the Navarro, Frenk and White (NFW) and the non-singular-isothermal-sphere (NSIS). We demonstrate the power of our formulation through a Kolmogorov-Smirnov (KS) test on the strong lensing statistics of an X-ray bright sample of low-redshift Abell clusters. This KS test allows us to establish limits on the values of the concentration parameter for the NFW profile (c_Δ) and the core radius for the NSIS profile (rc), which are related to the lowest cluster redshift (zcut) where strong arcs can be observed. For NFW dark matter profiles, we infer cluster haloes with concentrations that are consistent to those predicted by ΛCDM simulations. As for NSIS dark matter profiles, we find only upper limits for the clusters core radii and thus do not rule out a purely SIS model. For alternative mass profiles, our formulation provides constraints through zcut on the parameters that control the concentration of mass in the inner region of the clusters haloes. We find that zcut is expected to lie in the 0.0-0.2 redshift, highlighting the need to include very low-z clusters in samples to study the clusters mass profiles.

  12. Simulating Halos with the Caterpillar Project

    Science.gov (United States)

    Kohler, Susanna

    2016-04-01

    The Caterpillar Project is a beautiful series of high-resolution cosmological simulations. The goal of this project is to examine the evolution of dark-matter halos like the Milky Ways, to learn about how galaxies like ours formed. This immense computational project is still in progress, but the Caterpillar team is already providing a look at some of its first results.Lessons from Dark-Matter HalosWhy simulate the dark-matter halos of galaxies? Observationally, the formation history of our galaxy is encoded in galactic fossil record clues, like the tidal debris from disrupted satellite galaxies in the outer reaches of our galaxy, or chemical abundance patterns throughout our galactic disk and stellar halo.But to interpret this information in a way that lets us learn about our galaxys history, we need to first test galaxy formation and evolution scenarios via cosmological simulations. Then we can compare the end result of these simulations to what we observe today.This figure illustrates the difference that mass resolution makes. In the left panel, the mass resolution is 1.5*10^7 solar masses per particle. In the right panel, the mass resolution is 3*10^4 solar masses per particle [Griffen et al. 2016]A Computational ChallengeDue to how computationally expensive such simulations are, previous N-body simulations of the growth of Milky-Way-like halos have consisted of only one or a few halos each. But in order to establish a statistical understanding of how galaxy halos form and find out whether the Milky Ways halo is typical or unusual! it is necessary to simulate a larger number of halos.In addition, in order to accurately follow the formation and evolution of substructure within the dark-matter halos, these simulations must be able to resolve the smallest dwarf galaxies, which are around a million solar masses. This requires an extremely high mass resolution, which adds to the computational expense of the simulation.First OutcomesThese are the challenges faced by

  13. LOW-MASS SUPPRESSION OF THE SATELLITE LUMINOSITY FUNCTION DUE TO THE SUPERSONIC BARYON-COLD-DARK-MATTER RELATIVE VELOCITY

    Energy Technology Data Exchange (ETDEWEB)

    Bovy, Jo; Dvorkin, Cora [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States)

    2013-05-01

    We study the effect of the supersonic baryon-cold-dark-matter (CDM) flow, which has recently been shown to have a large effect on structure formation during the dark ages 10 {approx}< z {approx}< 1000, on the abundance of luminous, low-mass satellite galaxies around galaxies like the Milky Way. As the supersonic baryon-CDM flow significantly suppresses both the number of halos formed and the amount of baryons accreted onto such halos of masses 10{sup 6} < M{sub halo}/M{sub Sun} < 10{sup 8} at z {approx}> 10, a large effect results on the stellar luminosity function before reionization. As halos of these masses are believed to have very little star formation after reionization due to the effects of photoheating by the ultraviolet background, this effect persists to the present day. We calculate that the number of low-mass 10{sup 6} < M{sub halo}/M{sub Sun} < 5 Multiplication-Sign 10{sup 7} halos that host luminous satellite galaxies today is typically suppressed by 50%, with values ranging up to 90% in regions where the initial supersonic velocity is high. We show that this previously ignored cosmological effect resolves some of the tension between the observed and predicted number of low-mass satellites in the Milky Way, reducing the need for other mass-dependent star-formation suppression before reionization.

  14. Properties of Dark Matter Halos as a Function of Local Environment Density

    CERN Document Server

    Lee, Christoph T; Behroozi, Peter; Rodriguez-Puebla, Aldo; Hellinger, Doug; Dekel, Avishai

    2016-01-01

    We study how properties of discrete dark matter halos depend on halo environment, characterized by the mass density around the halos on scales from 0.5 to 16 $\\hmpc$. We find that low mass halos (those less massive than the characteristic mass $M_{\\rm C}$ of halos collapsing at a given epoch) in high-density environments have lower accretion rates, lower spins, higher concentrations, and rounder shapes than halos in median density environments. Halos in median and low-density environments have similar accretion rates and concentrations, but halos in low density environments have lower spins and are more elongated. Halos of a given mass in high-density regions accrete material earlier than halos of the same mass in lower-density regions. All but the most massive halos in high-density regions are losing mass (i.e., being stripped) at low redshifts, which causes artificially lowered NFW scale radii and increased concentrations. Tidal effects are also responsible for the decreasing spins of low mass halos in high...

  15. A Weak Lensing Study of X-ray Groups in the COSMOS survey: Form and Evolution of the Mass-Luminosity Relation

    CERN Document Server

    Leauthaud, A; Taylor, J E; Massey, R; Rhodes, J; Ilbert, O; Bundy, K; Tinker, J; George, M R; Capak, P; Koekemoer, A M; Johnston, D E; Cappelluti, N; Ellis, Richard S; Elvis, M; Heymans, C; Le Fèvre, O; Lilly, S; McCraken, H J; Mellier, Y; Réfrégier, A; Salvato, M; Scoville, N; Smoot, G; Tanaka, M; Van Waerbeke, L; Wolk, M

    2009-01-01

    Measurements of X-ray scaling laws are critical for improving cosmological constraints derived with the halo mass function and for understanding the physical processes that govern the heating and cooling of the intracluster medium. In this paper, we use a sample of 206 X-ray selected galaxy groups to investigate the scaling relation between X-ray luminosity (Lx) and halo mass (M00) where M200 is derived via stacked weak gravitational lensing. This work draws upon a broad array of multi-wavelength COSMOS observations including 1.64 square degrees of contiguous imaging with the Advanced Camera for Surveys (ACS) and deep XMM-Newton/Chandra imaging. The combined depth of these two data-sets allows us to probe the lensing signals of X-ray detected structures at both higher redshifts and lower masses than previously explored. Weak lensing profiles and halo masses are derived for nine sub-samples, narrowly binned in luminosity and redshift. The COSMOS data alone are well fit by a power law, M200 ~ Lx^a, with a slope...

  16. Galaxy Halo Occupation at High Redshift

    CERN Document Server

    Bullock, J S; Somerville, R S; Bullock, James S.; Wechsler, Risa H.; Somerville, Rachel S.

    2002-01-01

    We discuss how current and future data on the clustering and number density of z~3 Lyman-break galaxies (LBGs) can be used to constrain their relationship to dark matter haloes. We explore a three-parameter model in which the number of LBGs per dark halo scales like a power-law in the halo mass: N(M) = (M/M_1)^S for M>M_m. Here, M_m is the minimum mass halo that can host an LBG, M_1 is a normalization parameter, associated with the mass above which haloes host more than one observed LBG, and S determines the strength of the mass dependence. We show how these three parameters are constrained by three observable properties of LBGs: the number density, the large-scale bias, and the fraction of objects in close pairs. Given these three quantities, the three unknown model parameters may be estimated analytically, allowing a full exploration of parameter space. As an example, we assume an LCDM cosmology and consider the observed properties of a recent sample of spectroscopically confirmed LBGs. We find that the fav...

  17. Weak Lensing Measurement of the Mass--Richness Relation of SDSS redMaPPer Clusters

    CERN Document Server

    Simet, Melanie; Mandelbaum, Rachel; Rozo, Eduardo; Rykoff, Eli; Sheldon, Erin; Wechsler, Risa H

    2016-01-01

    We perform a measurement of the mass--richness relation of the redMaPPer galaxy cluster catalogue using weak lensing data from the Sloan Digital Sky Survey. We have carefully characterized a broad range of systematic uncertainties, including shear calibration errors, photo-$z$ biases, dilution by member galaxies, source obscuration, magnification bias, incorrect assumptions about cluster mass profiles, cluster centering, halo triaxiality, and projection effects. We also compare measurements of the lensing signal from two independently-produced shear and photometric redshift catalogues to characterize systematic errors in the lensing signal itself. Using a sample of 5,570 clusters from $0.1\\le z\\le 0.33$, the normalization of our power-law mass vs.\\ $\\lambda$ relation is $\\log_{10}[M_{200m}/h^{-1}\\ M_{\\odot}]$ = $14.344 \\pm 0.021$ (statistical) $\\pm 0.023$ (systematic) at a richness $\\lambda=40$, a 7 per cent calibration uncertainty, with a power-law index of $1.33^{+0.09}_{-0.10}$ ($1\\sigma$). The detailed sy...

  18. A look to the inside of haloes: a characterisation of the halo shape as a function of overdensity in the Planck cosmology

    CERN Document Server

    Despali, Giulia; Bonamigo, Mario; Limousin, Marceau; Tormen, Giuseppe

    2016-01-01

    In this paper we study the triaxial properties of dark matter haloes of a wide range of masses extracted from a set of cosmological N-body simulations. We measure the shape at different distances from the halo center (characterised by different overdensity thresholds), both in three and in two dimensions, discussing how halo triaxiality increases with (i) mass, (ii) redshift and (iii) overdensity. We also examine how the orientation of the different ellipsoidal shells are aligned with each other and what is the gradient in internal shapes for halos with different virial configurations. Our findings highlight that the internal part of the halo retains memory of the violent formation process keeping the major axis oriented toward the preferential direction of the infalling material while the outer part becomes rounder due to continuous isotropic merging events; this effect is clearly evident in high mass haloes - which formed recently - while it is more blurred in low mass haloes. We present simple distribution...

  19. The Dark Side of the Halo Occupation Distribution

    CERN Document Server

    Kravtsov, A V; Wechsler, R H; Klypin, A A; Gottlöber, S; Allgood, B; Primack, J R; Kravtsov, Andrey V.; Berlind, Andreas A.; Wechsler, Risa H.; Klypin, Anatoly A.; Gottloeber, Stefan; Allgood, Brandon; Primack, Joel R.

    2003-01-01

    We analyze the halo occupation distribution (HOD), the probability for a halo of mass M to host a number of subhalos N, and two-point correlation function of galaxy-size dark matter halos using high-resolution dissipationless simulations of the concordance flat LCDM model. The halo samples include both the host halos and the subhalos, distinct gravitationally-bound halos within the virialized regions of larger host systems. We find that the first moment of the HOD, (M), has a complicated shape consisting of a step, a shoulder, and a power law high-mass tail. The HOD can be described by a Poisson statistics at high halo masses but becomes sub-Poisson for (M). We find that ~M^b with b~1 for a wide range of number densities, redshifts, and different power spectrum normalizations. This formulation provides a simple but accurate model for the halo occupation distribution found in simulations. At z=0, the two-point correlation function (CF) of galactic halos can be well fit by a power law down to ~100/h kpc with an...

  20. CoMaLit-IV. Evolution and self-similarity of scaling relations with the galaxy cluster mass

    CERN Document Server

    Sereno, Mauro

    2015-01-01

    The scaling of observable properties of galaxy clusters with mass evolves with time. Assessing the role of the evolution is crucial to study the formation and evolution of massive halos and to avoid biases in the calibration. We present a general method to infer the mass and the redshift dependence, and the time-evolving intrinsic scatter of the mass-observable relations. The procedure self-calibrates the redshift dependent completeness function of the sample. The intrinsic scatter in the mass estimates used to calibrate the relation is considered too. We apply the method to the scaling of mass M_Delta versus line of sight galaxy velocity dispersion sigma_v, optical richness, X-ray luminosity, L_X, and Sunyaev-Zel'dovich signal. Masses were calibrated with weak lensing measurements. The measured relations are in good agreement with time and mass dependencies predicted in the self-similar scenario of structure formation. The lone exception is the L_X-M_Delta relation whose time evolution is negative in agreeme...

  1. A theoretical study of the mass temperature relation for clusters of galaxies

    CERN Document Server

    Popolo, A D

    2002-01-01

    I derive the mass-temperature relation and its time evolution for clusters of galaxies in different cosmologies by means of two different models. The first one is a modification and improvement of a model by Del Popolo & Gambera(1999), namely based upon a modification of the top-hat model in order to take account of angular momentum acquisition by protostructures and of an external pressure term in the virial theorem. The second one is based on the merging-halo formalism of Lacey & Cole (1993), accounting for the fact that massive clusters accrete matter quasi-continuously, and is an improvement of a model proposed by Voit (2000). The final result is that, in both models, the M-T relation shows a break at T \\sim 3-4 keV. The behavior of the M-T relation is as usual, M \\propto T^{3/2}, at the high mass end, and M \\propto T^{\\gamma}, with a value of \\gamma>3/2 depending on the chosen cosmology. The evolution of the M-T relation, for a given M_{\\rm vir}, is more modest both in flat and open universes in ...

  2. Velocity moments of dark matter haloes

    CERN Document Server

    Wojtak, R; Gottlöber, S; Mamon, G A; Wojtak, Radoslaw; Lokas, Ewa L.; Gottloeber, Stefan; Mamon, Gary A.

    2006-01-01

    Using cosmological N-body simulations we study the line-of-sight velocity distribution of dark matter haloes focusing on the lowest-order even moments, dispersion and kurtosis, and their application to estimate the mass profiles of cosmological structures. For each of the ten massive haloes selected from the simulation box we determine the virial mass, concentration and the anisotropy parameter. In order to emulate observations from each halo we choose randomly 300 particles and project their velocities and positions along the line of sight and on the surface of the sky, respectively. After removing interlopers we calculate the profiles of the line-of-sight velocity moments and fit them with the solutions of the Jeans equations. The estimates of virial mass, concentration parameter and velocity anisotropy obtained in this way are in good agreement with the values found from the full 3D analysis.

  3. The mass-luminosity relation for stars of mass 1.0 to 0.08 solar mass

    Science.gov (United States)

    Henry, Todd J.; Mccarthy, Donald W., Jr.

    1993-01-01

    Mass-luminosity relations determined at IR wavelengths are presented for stars with masses 1.0 to 0.08 solar mass. Using IR speckle imaging techniques on a sample of nearby binaries, we have been able to concentrate on the lower main sequence, for which an accurate mass-luminosity calibration has remained problematic. In addition, the mass-visual luminosity relation for stars with 2.0-0.08 solar mass is produced by implementing new photometric relations linking V to JHK wavelengths for the nearby stars, supplemented with eclipsing binary information. These relations predict that objects with masses of about 0.08 solar mass have M(K) of about 10 and M(V) of about 18.

  4. Spin alignment of dark matter haloes in filaments and walls

    CERN Document Server

    Arag'on-Calvo, M A; Jones, B J T; Van der Hulst, T; Arag\\'on-Calvo, Miguel A.; Weygaert, Rien van de; Jones, Bernard J. T.

    2006-01-01

    The MMF technique is used to segment the cosmic web as seen in a cosmological N-body simulation into wall-like and filament-like structures. We find that the spins and shapes of dark matter haloes are significantly correlated with each other and with the orientation of their host structures. The shape orientation is such that the halo minor axes tend to lie perpendicular to the host structure, be it a wall or filament. The orientation of the halo spin vector is mass dependent. Low mass haloes in walls and filaments have a tendency to have their spins oriented within the parent structure, while higher mass haloes in filaments have spins that tend to lie perpendicular to the parent structure.

  5. Self-consistent massive disks in triaxial dark matter halos

    CERN Document Server

    Bailin, Jeremy; Bolatto, Alberto D; Gibson, Brad K; Power, Chris

    2007-01-01

    Galactic disks in triaxial dark matter halos become deformed by the elliptical potential in the plane of the disk in such a way as to counteract the halo ellipticity. We develop a technique to calculate the equilibrium configuration of such a disk in the combined disk-halo potential, which is based on the method of Jog (2000) but accounts for the radial variation in both the halo potential and the disk ellipticity. This crucial ingredient results in qualitatively different behavior of the disk: the disk circularizes the potential at small radii, even for a reasonably low disk mass. This effect has important implications for proposals to reconcile cuspy halo density profiles with low surface brightness galaxy rotation curves using halo triaxiality. The disk ellipticities in our models are consistent with observational estimates based on two-dimensional velocity fields and isophotal axis ratios.

  6. Relation Between the Pole Mass and MS Mass of Top Quark in Supersymmetric QCD

    Institute of Scientific and Technical Information of China (English)

    CHEN Shao-Long; FENG Tai-Fu; LI Xue-Qian

    2001-01-01

    We discuss the relation between the pole mass and MS mass of top quark in the framework of the supersymmetric QCD. We find that the supersymmetric contributions are comparable to those of the standard model.

  7. Relation Between the Pole Mass and MS Mass of Top Quark in Supersymmetric QCD

    Institute of Scientific and Technical Information of China (English)

    CHENShao-Long; FENGTai-Fu; 等

    2001-01-01

    We discuss the relation between the pole mass and MS mass of top quark in the framework of the supersymmetric QCD.We find that the supersymmetric contributions are comparable to those of the standard model.

  8. The diversity and similarity of simulated cold dark matter haloes

    NARCIS (Netherlands)

    Navarro, Julio F.; Ludlow, Aaron; Springel, Volker; Wang, Jie; Vogelsberger, Mark; White, Simon D. M.; Jenkins, Adrian; Frenk, Carlos S.; Helmi, Amina

    2010-01-01

    We study the mass, velocity dispersion and anisotropy profiles of Lambda cold dark matter (Lambda CDM) haloes using a suite of N-body simulations of unprecedented numerical resolution. The Aquarius Project follows the formation of six different galaxy-sized haloes simulated several times at varying

  9. The diversity and similarity of simulated cold dark matter haloes

    NARCIS (Netherlands)

    Navarro, Julio F.; Ludlow, Aaron; Springel, Volker; Wang, Jie; Vogelsberger, Mark; White, Simon D. M.; Jenkins, Adrian; Frenk, Carlos S.; Helmi, Amina

    2010-01-01

    We study the mass, velocity dispersion and anisotropy profiles of Λ cold dark matter (ΛCDM) haloes using a suite of N-body simulations of unprecedented numerical resolution. The Aquarius Project follows the formation of six different galaxy-sized haloes simulated several times at varying numerical r

  10. Binary white dwarfs in the halo of the Milky Way

    NARCIS (Netherlands)

    van Oirschot, Pim; Nelemans, Gijs; Toonen, Silvia; Pols, Onno; Brown, Anthony G. A.; Helmi, Amina; Portegies Zwart, Simon

    2014-01-01

    Aims: We study single and binary white dwarfs in the inner halo of the Milky Way in order to learn more about the conditions under which the population of halo stars was born, such as the initial mass function (IMF), the star formation history, or the binary fraction. Methods: We simulate the evolut

  11. How well do cosmological simulations reproduce individual-halo properties?

    CERN Document Server

    Trenti, M; Hallman, E J; Skillman, S W; Shull, J M

    2010-01-01

    Cosmological simulations of galaxy formation often rely on prescriptions for star formation and feedback that depend on halo properties such as halo mass, central over-density, and virial temperature. In this paper we address the convergence of individual halo properties, based on their number of particles N, focusing in particular on the mass of halos near the resolution limit of a simulation. While it has been established that the halo mass function is sampled on average down to N~30 particles, we show that individual halo properties exhibit significant scatter, and some systematic biases, as one approaches the resolution limit. We carry out a series of cosmological simulations using the Gadget2 and Enzo codes with N_p=64^3 to N_p=1024^3 total particles, keeping the same large-scale structure in the simulation box. We consider boxes from l_{box} = 8 Mpc/h to l_{box} = 512 Mpc/h to probe different halo masses and formation redshifts. We cross-identify dark matter halos in boxes at different resolutions and m...

  12. The Tidal Origin of the Environment Dependence of Halo Assembly

    CERN Document Server

    Hahn, Oliver; Dekel, Avishai; Carollo, C Marcella

    2008-01-01

    We uncover the origin of the puzzling anti-correlation between the formation epoch of galactic dark-matter haloes and their environment density. This correlation has been revealed from cosmological N-body simulations and it is in conflict with the simple excursion-set model of halo clustering. Using similar simulations, we first quantify the straightforward association of an early formation epoch with a reduced mass growth rate at late times. We then find that the primary driver of suppressed growth, by accretion or mergers, is tidal effects dominated by a neighbouring massive halo. The tidal effects range from a slowdown of the assembly of haloes due to the shear along the large-scale filaments that feed the massive halo to actual mass loss in haloes that pass through the massive halo. Our results suggest that the dependence of formation epoch on environment density is a secondary effect induced by the enhanced density of haloes in filaments near massive haloes where the tides are strong. Our measures of ass...

  13. ALFA beam halo

    CERN Document Server

    Komarek, Tomas

    2014-01-01

    This note serves as a final report about CERN Summer Student Programme 2014 project. The beam halo is an undesired phenomenon for physics analyses on particle accelerators. It surrounds the beam core and constitutes an important part of background for signal measurements on some detectors, eg. in the forward region. In this study, the data from the ALFA detector were used, specifically from the run 191373 ($\\beta^*=90\\unit{m}$) and the run 213268 ($\\beta^*=1\\unit{km}$). Using the ROOT framework, a software for beam halo events selection was created and beam halo properties were examined. In the run 213268, excessive beam halo is suspected to be the reason for multiple beam scrapings that occurred. A kinematic reconstruction of beam halo particles is attempted in order to understand beam halo properties in the interaction point. Some further simulations are employed to find constraints for beam halo particles in order to survive in the accelerator for a longer time/many revolutions. This work represents a st...

  14. The Dragonfly Nearby Galaxies Survey. I. Substantial variation in the diffuse stellar halos around spiral galaxies

    CERN Document Server

    Merritt, Allison; Abraham, Roberto; Zhang, Jielai

    2016-01-01

    Galaxies are thought to grow through accretion; as less massive galaxies are disrupted and merge over time, their debris results in diffuse, clumpy stellar halos enveloping the central galaxy. Here we present a study of the variation in the stellar halos of galaxies, using data from the Dragonfly Nearby Galaxies Survey (DNGS). The survey consists of wide field, deep ($\\mu_{g} > 31$ mag arcsec$^{-2}$) optical imaging of nearby galaxies using the Dragonfly Telephoto Array. Our sample includes eight spiral galaxies with stellar masses similar to that of the Milky Way, inclinations of $16-90$ degrees and distances between $7-18$ Mpc. We construct stellar mass surface density profiles from the observed $g$-band surface brightness in combination with the $g-r$ color as a function of radius, and compute the halo fractions from the excess stellar mass (relative to a disk$+$bulge fit) beyond $5$ half-mass radii. We find a mean halo fraction of $0.009 \\pm 0.005$ and a large RMS scatter of $1.01^{+0.9}_{-0.26}$ dex. The...

  15. On the center of mass in general relativity

    CERN Document Server

    Huang, Lan-Hsuan

    2011-01-01

    The classical notion of center of mass for an isolated system in general relativity is derived from the Hamiltonian formulation and represented by a flux integral at infinity. In contrast to mass and linear momentum which are well-defined for asymptotically flat manifolds, center of mass and angular momentum seem less well-understood, mainly because they appear as the lower order terms in the expansion of the data than those which determine mass and linear momentum. This article summarizes some of the recent developments concerning center of mass and its geometric interpretation using the constant mean curvature foliation near infinity. Several equivalent notions of center of mass are also discussed.

  16. Hunting A Wandering Supermassive Black Hole in M31 Halo -- Hermitage of Black Hole

    CERN Document Server

    Miki, Yohei; Kawaguchi, Toshihiro; Saito, Yuriko

    2014-01-01

    In the hierarchical structure formation scenario, galaxies enlarge through multiple merging events with less massive galaxies. In addition, the Magorrian relation indicates that almost all galaxies are occupied by a central supermassive black hole (SMBH) of mass $10^{-3}$ of its spheroidal component. Consequently, SMBHs are expected to wander in the halos of their host galaxies following a galaxy collision, although evidence of this activity is currently lacking. We investigate a current plausible location of an SMBH wandering in the halo of the Andromeda galaxy (M31). According to theoretical studies of $N$-body simulations, some of the many substructures in the M31 halo are remnants of a minor merger occurring about 1 Gyr ago. First, to evaluate the possible parameter space of the infalling orbit of the progenitor, we perform numerous parameter studies using a Graphics Processing Unit (GPU) cluster. To reduce uncertainties in the predicted position of the expected SMBH, we then calculate the time evolution ...

  17. Swirling around filaments: are large-scale structure vortices spinning up dark halos?

    CERN Document Server

    Laigle, Clotilde; Codis, Sandrine; Dubois, Yohan; Borgne, Damien le; Pogosyan, Dmitri; Devriendt, Julien; Peirani, Sebastien; Prunet, Simon; Rouberol, Stephane; Slyz, Adrianne; Sousbie, Thierry

    2013-01-01

    The kinematic analysis of dark matter and hydrodynamical simulations suggests that the vorticity in large-scale structure is mostly confined to, and predominantly aligned with their filaments, with an excess of probability of 20 per cent to have the angle between vorticity and filaments direction lower than 60 degrees relative to random orientations. The cross sections of these filaments are typically partitioned into four quadrants with opposite vorticity sign, arising from multiple flows, originating from neighbouring walls. The spins of halos embedded within these filaments are consistently aligned with this vorticity for any halo mass, with a stronger alignment for the most massive structures up to an excess of probability of 165 per cent. On large scales, adiabatic/cooling hydrodynamical simulations display the same vorticity in the gas as in the dark matter. The global geometry of the flow within the cosmic web is therefore qualitatively consistent with a spin acquisition for smaller halos induced by th...

  18. Substructure of fuzzy dark matter halos

    CERN Document Server

    Du, Xiaolong; Niemeyer, Jens C

    2016-01-01

    We derive the halo mass function (HMF) for fuzzy dark matter (FDM) by solving the excursion set problem explicitly with a mass-dependent barrier function, which has not been done before. We find that compared to the naive approach of the Sheth-Tormen HMF for FDM the one we obtain has a higher cut off mass and the cut off mass change less strongly with redshifts. Using merger trees constructed with a modified version of the Lacey & Cole formalism that accounts for suppressed small scale power and the scale-dependent growth of FDM halos and the semi-analytic Galacticus code, we study the statistics of halo substructure including the effects from dynamical friction and tidal stripping. We find that if the dark matter is a mixture of cold dark matter (CDM) and FDM, there will be a suppression on the halo substructure on small scales which may be able to solve the Missing Satellites Problem faced by the pure CDM model. The suppression becomes stronger with increasing FDM fraction or decreasing FDM mass. Thus i...

  19. Substructure of fuzzy dark matter haloes

    Science.gov (United States)

    Du, Xiaolong; Behrens, Christoph; Niemeyer, Jens C.

    2017-02-01

    We derive the halo mass function (HMF) for fuzzy dark matter (FDM) by solving the excursion set problem explicitly with a mass-dependent barrier function, which has not been done before. We find that compared to the naive approach of the Sheth-Tormen HMF for FDM, our approach has a higher cutoff mass and the cutoff mass changes less strongly with redshifts. Using merger trees constructed with a modified version of the Lacey & Cole formalism that accounts for suppressed small-scale power and the scale-dependent growth of FDM haloes and the semi-analytic GALACTICUS code, we study the statistics of halo substructure including the effects from dynamical friction and tidal stripping. We find that if the dark matter is a mixture of cold dark matter (CDM) and FDM, there will be a suppression on the halo substructure on small scales which may be able to solve the missing satellites problem faced by the pure CDM model. The suppression becomes stronger with increasing FDM fraction or decreasing FDM mass. Thus, it may be used to constrain the FDM model.

  20. The properties of warm dark matter haloes

    Science.gov (United States)

    Lovell, Mark R.; Frenk, Carlos S.; Eke, Vincent R.; Jenkins, Adrian; Gao, Liang; Theuns, Tom

    2014-03-01

    Well-motivated elementary particle candidates for the dark matter, such as the sterile neutrino, behave as warm dark matter (WDM). For particle masses of the order of a keV, free streaming produces a cutoff in the linear fluctuation power spectrum at a scale corresponding to dwarf galaxies. We investigate the abundance and structure of WDM haloes and subhaloes on these scales using high resolution cosmological N-body simulations of galactic haloes of mass similar to the Milky Way's. On scales larger than the free-streaming cutoff, the initial conditions have the same power spectrum and phases as one of the cold dark matter (CDM) haloes previously simulated by Springel et al. as part of the Virgo consortium Aquarius project. We have simulated four haloes with WDM particle masses in the range 1.5-2.3 keV and, for one case, we have carried out further simulations at varying resolution. N-body simulations in which the power spectrum cutoff is resolved are known to undergo artificial fragmentation in filaments producing spurious clumps which, for small masses (Frenk-White or Einasto profiles. Their central densities are lower for lower WDM particle masses and none of the models we have considered suffering from the `too big to fail' problem recently highlighted by Boylan-Kolchin et al.

  1. Galaxy halo occupation at high redshift

    Science.gov (United States)

    Bullock, James S.; Wechsler, Risa H.; Somerville, Rachel S.

    2002-01-01

    We discuss how current and future data on the clustering and number density of z~3 Lyman-break galaxies (LBGs) can be used to constrain their relationship to dark matter haloes. We explore a three-parameter model in which the number of LBGs per dark halo scales like a power law in the halo mass: N(M)=(M/M1)S for M>Mmin. Here, Mmin is the minimum mass halo that can host an LBG, M1 is a normalization parameter, associated with the mass above which haloes host more than one observed LBG, and S determines the strength of the mass-dependence. We show how these three parameters are constrained by three observable properties of LBGs: the number density, the large-scale bias and the fraction of objects in close pairs. Given these three quantities, the three unknown model parameters may be estimated analytically, allowing a full exploration of parameter space. As an example, we assume a ΛCDM cosmology and consider the observed properties of a recent sample of spectroscopically confirmed LBGs. We find that the favoured range for our model parameters is Mmin~=(0.4-8)×1010h- 1Msolar, M1~=(6-10)×1012h- 1Msolar, and 0.9acceptable if the allowed range of bg is permitted to span all recent observational estimates. We also discuss how the observed clustering of LBGs as a function of luminosity can be used to constrain halo occupation, although because of current observational uncertainties we are unable to reach any strong conclusions. Our methods and results can be used to constrain more realistic models that aim to derive the occupation function N(M) from first principles, and offer insight into how basic physical properties affect the observed properties of LBGs.

  2. ANGULAR MOMENTUM ACQUISITION IN GALAXY HALOS

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, Kyle R. [Department of Natural and Mathematical Sciences, California Baptist University, 8432 Magnolia Ave., Riverside, CA 92504 (United States); Brooks, Alyson M. [Department of Astronomy, University of Wisconsin-Madison, 475 N. Charter St., Madison, WI 53706 (United States); Bullock, James S. [Center for Cosmology, Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697 (United States); Maller, Ariyeh H. [Department of Physics, New York City College of Technology, 300 Jay St., Brooklyn, NY 11201 (United States); Diemand, Juerg [Institute for Theoretical Physics, University of Zurich, 8057, Zurich (Switzerland); Wadsley, James [Department of Physics and Astronomy, McMaster University, Main Street West, Hamilton L85 4M1 (Canada); Moustakas, Leonidas A. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2013-05-20

    We use high-resolution cosmological hydrodynamic simulations to study the angular momentum acquisition of gaseous halos around Milky-Way-sized galaxies. We find that cold mode accreted gas enters a galaxy halo with {approx}70% more specific angular momentum than dark matter averaged over cosmic time (though with a very large dispersion). In fact, we find that all matter has a higher spin parameter when measured at accretion than when averaged over the entire halo lifetime, and is well characterized by {lambda} {approx} 0.1, at accretion. Combined with the fact that cold flow gas spends a relatively short time (1-2 dynamical times) in the halo before sinking to the center, this naturally explains why cold flow halo gas has a specific angular momentum much higher than that of the halo and often forms ''cold flow disks.'' We demonstrate that the higher angular momentum of cold flow gas is related to the fact that it tends to be accreted along filaments.

  3. What's a Halo?

    Science.gov (United States)

    ... soap and damp towel. Avoid using sponges that trap water and can easily leak onto the halo ... Nemours Foundation, iStock, Getty Images, Corbis, Veer, Science Photo Library, Science Source Images, Shutterstock, and Clipart.com

  4. Mass discrepancy-acceleration relation: A universal maximum dark matter acceleration and implications for the ultralight scalar dark matter model

    Science.gov (United States)

    Ureña-López, L. Arturo; Robles, Victor H.; Matos, T.

    2017-08-01

    Recent analysis of the rotation curves of a large sample of galaxies with very diverse stellar properties reveals a relation between the radial acceleration purely due to the baryonic matter and the one inferred directly from the observed rotation curves. Assuming the dark matter (DM) exists, this acceleration relation is tantamount to an acceleration relation between DM and baryons. This leads us to a universal maximum acceleration for all halos. Using the latter in DM profiles that predict inner cores implies that the central surface density μDM=ρsrs must be a universal constant, as suggested by previous studies of selected galaxies, revealing a strong correlation between the density ρs and scale rs parameters in each profile. We then explore the consequences of the constancy of μDM in the context of the ultralight scalar field dark matter model (SFDM). We find that for this model μDM=648 M⊙ pc-2 and that the so-called WaveDM soliton profile should be a universal feature of the DM halos. Comparing with the data from the Milky Way and Andromeda satellites, we find that they are all consistent with a boson mass of the scalar field particle of the order of 10-21 eV /c2, which puts the SFDM model in agreement with recent cosmological constraints.

  5. Mass--concentration relation of clusters of galaxies from CFHTLenS

    CERN Document Server

    Du, Wei; Shan, Huanyuan; Zhao, Gong-Bo; Covone, Giovanni; Fu, Liping; Kneib, Jean-Paul

    2015-01-01

    Based on CFHTLenS weak lensing observations, in this paper, we study the mass--concentration ($M$--$c$) relation for $\\sim 200$ redMaPPer clusters in the fields. We extract the $M$--$c$ relation by measuring the density profiles of individual clusters instead of using stacked weak lensing signals. By performing Monte Carlo simulations, we demonstrate that although the signal-to-noise ratio for each individual cluster is low, the unbiased $M$--$c$ relation can still be reliably derived from a large sample of clusters by carefully taking into account the impacts of shape noise, cluster center offset, dilution effect from member or foreground galaxies and the projection effect. Our results show that within error bars, the derived $M$--$c$ relation for redMaPPer clusters is in agreement with simulation predictions. There is a weak deviation that the halo concentrations calibrated by Monte Carlo simulations are somewhat higher than that predicted from ${\\it Planck}$ cosmology.

  6. Why are Halo Density Profiles Stable at Formation?

    CERN Document Server

    González-Casado, G; Salvador-Solé, E

    1998-01-01

    We analyze the physical justification of the picture proposed by Salvador-Sole et al. in these proceedings for the time evolution of the universal density profile of dark-matter halos. According to this picture, halos have at formation a stable (i.e. independent of mass and time) dimensionless density profile, the characteristic length and density scales of the profile depending on the underlying cosmogony. Subsequent evolution is driven by mass accretion onto the outskirts of halos and can be characterized simply by the increment of halo radius with time and the corresponding decrease of the critical density of the universe. We find this picture to be a reasonable good description of the expected evolution of halos in hierarchical models of structure formation.

  7. Halo vest instrumentation

    Science.gov (United States)

    Huston, Dryver R.; Krag, Martin

    1996-05-01

    The halo vest is a head and neck immobilization system that is often used on patients that are recovering from cervical trauma or surgery. The halo vest system consists of a rigid halo that is firmly attached to the skull, an upright support structure for stabilization and immobilization, and a torso-enveloping vest. The main purpose of this study was to measure the forces that are carried by the halo-vest structure as the subject undergoes various activities of daily living and external loading for different vest designs. A tethered strain gage load cell based instrumentation system was used to take these load measurements on ten different subjects. Three different halo-vest systems were evaluated. The primary difference between the vests was the amount of torso coverage and the use of shoulder straps. The loads were measured, analyzed and used to compare the vests and to create a model of halo-vest-neck mechanics. Future applications of this technology to standalone data logging, pin-load measuring and biofeedback applications are discussed.

  8. The dark matter distribution in z~0.5 clusters of galaxies. I : Determining scaling relations with weak lensing masses

    CERN Document Server

    Foëx, G; Pointecouteau, E; Arnaud, M; Limousin, M; Pratt, G W

    2012-01-01

    The total mass of clusters of galaxies is a key parameter to study massive halos. It relates to numerous gravitational and baryonic processes at play in the framework of large scale structure formation, thus rendering its determination important but challenging. From a sample of the 11 X-ray bright clusters selected from the excpres sample, we investigate the optical and X-ray properties of clusters with respect to their total mass derived from weak gravitational lensing. From multi-color wide field imaging obtained with MegaCam at CFHT, we derive the shear profile of each individual cluster of galaxies. We perform a careful investigation of all systematic sources related to the weak lensing mass determination. The weak lensing masses are then compared to the X-ray masses obtained from the analysis of XMM observations and assuming hydrostatic equilibrium. We find a good agreement between the two mass proxies although a few outliers with either perturbed morphology or poor quality data prevent to derive robust...

  9. The Halo Occupation Distribution of HI Galaxies

    CERN Document Server

    Wyithe, Stuart; Zwaan, Martin A; Meyer, Martin J

    2009-01-01

    We perform an analysis of the spatial clustering properties of HI selected galaxies from the HI Parkes All Sky Survey (HIPASS) using the formalism of the halo occupation distribution (HOD). The resulting parameter constraints show that the fraction of satellite galaxies (i.e. galaxies which are not the central member of their host dark matter halo) among HIPASS galaxies is <20%, and that satellite galaxies are therefore less common in HIPASS than in optically selected galaxy redshift surveys. Moreover the lack of fingers-of-god in the redshift space correlation function of HIPASS galaxies may indicate that the HI rich satellites which do exist are found in group mass rather than cluster mass dark matter halos. We find a minimum halo mass for HIPASS galaxies at the peak of the redshift distribution of M~10^11 solar masses, and show that less than 10% of baryons in HIPASS galaxies are in the form of HI. Quantitative constraints on HOD models from HIPASS galaxies are limited by uncertainties introduced throug...

  10. N-body Merger Trees and Halo Properties

    CERN Document Server

    Jiang, Lilian; Cole, Shaun; Frenk, Carlos S

    2013-01-01

    We present the Dhalo algorithm which analyses a series of cosmological N-body simulation snapshots to define a self-consistent set of dark matter haloes and merger trees describing their evolution. The advantage over the more common FoF haloes is that the Dhalo algorithm maintains as distinct haloes objects that can be prematurely linked into a single FoF group by tenuous bridges of particles or by the onset of the overlap of their outer diffuse haloes. It is important to understand the properties of the haloes defined by this new algorithm to ensure the assumptions made in galform are consistent with the simulation. We generate FoF and Dhalo catalogues for the Millennium Simulation II and compare their properties. About 90% of the Dhaloes have a bijective match with a FoF halo. The remaining 10% are typically secondary components of large FoF haloes. While a significant fraction FoF haloes are split into more than one Dhalo we find that there is little difference in their overall halo mass functions. Compare...

  11. FIRST RESULTS FROM THE DRAGONFLY TELEPHOTO ARRAY: THE APPARENT LACK OF A STELLAR HALO IN THE MASSIVE SPIRAL GALAXY M101

    Energy Technology Data Exchange (ETDEWEB)

    Van Dokkum, Pieter G.; Merritt, Allison [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Abraham, Roberto [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H8 (Canada)

    2014-02-20

    We use a new telescope concept, the Dragonfly Telephoto Array, to study the low surface brightness outskirts of the spiral galaxy M101. The radial surface brightness profile is measured down to μ {sub g} ∼ 32 mag arcsec{sup –2}, a depth that approaches the sensitivity of star count studies in the Local Group. We convert surface brightness to surface mass density using the radial g – r color profile. The mass density profile shows no significant upturn at large radius and is well-approximated by a simple bulge + disk model out to R = 70 kpc, corresponding to 18 disk scale lengths. Fitting a bulge + disk + halo model we find that the best-fitting halo mass M{sub halo}=1.7{sub −1.7}{sup +3.4}×10{sup 8} M {sub ☉}. The total stellar mass of M101 is M{sub tot,∗}=5.3{sub −1.3}{sup +1.7}×10{sup 10} M {sub ☉}, and we infer that the halo mass fraction f{sub halo}=M{sub halo}/M{sub tot,∗}=0.003{sub −0.003}{sup +0.006}. This mass fraction is lower than that of the Milky Way (f {sub halo} ∼ 0.02) and M31 (f {sub halo} ∼ 0.04). All three galaxies fall below the f {sub halo}-M {sub tot,} {sub *} relation predicted by recent cosmological simulations that trace the light of disrupted satellites, with M101's halo mass a factor of ∼10 below the median expectation. However, the predicted scatter in this relation is large, and more galaxies are needed to better quantify this possible tension with galaxy formation models. Dragonfly is well suited for this project: as integrated-light surface brightness is independent of distance, large numbers of galaxies can be studied in a uniform way.

  12. Axion mass bound in very special relativity

    Science.gov (United States)

    Bufalo, R.; Upadhyay, S.

    2017-09-01

    In this paper we propose a very special relativity (VSR)-inspired description of the axion electrodynamics. This proposal is based upon the construction of a proper study of the SIM(2)-VSR gauge-symmetry. It is shown that the VSR nonlocal effects give a health departure from the usual axion field theory. The axionic classical dynamics is analyzed in full detail, first by a discussion of its solution in the presence of an external magnetic field. Next, we compute photon-axion transition in VSR scenario by means of Primakoff interaction, showing the change of a linearly polarized light to a circular one. Afterwards, duality symmetry is discussed in the VSR framework.

  13. Super-massive black hole mass scaling relations

    CERN Document Server

    Graham, Alister W; Schombert, James

    2014-01-01

    Using black hole masses which span 10^5 to 10^(10) solar masses, the distribution of galaxies in the (host spheroid stellar mass)-(black hole mass) diagram is shown to be strongly bent. While the core-Sersic galaxies follow a near-linear relation, having a mean M_(bh)/M_(sph) mass ratio of ~0.5%, the Sersic galaxies follow a near-quadratic relation: M_bh~M_sph^(2.22+\\-0.58). This is not due to offset pseudobulges, but is instead an expected result arising from the long-known bend in the M_(sph)-sigma relation and the log-linear M_(bh)-sigma relation.

  14. Strong Lensing In The Inner Halo Of Galaxy Clusters

    CERN Document Server

    Saez, C; Cypriano, E S; Sodré, L; Kneib, J -P

    2016-01-01

    We present an axially symmetric formula to calculate the probability of finding gravitational arcs in galaxy clusters, being induced by their massive dark matter haloes, as a function of clusters redshifts and virial masses. The formula includes the ellipticity of the clusters dark matter potential by using a pseudo-elliptical approximation. The probabilities are calculated and compared for two dark-matter halo profiles, the Navarro, Frenk and White (NFW) and the Non-Singular-Isothermal-Sphere (NSIS). We demonstrate the power of our formulation through a Kolmogorov-Smirnov (KS) test on the strong lensing statistics of an X-ray bright sample of low redshift Abell clusters. This KS test allows to establish limits on the values of the concentration parameter for the NFW profile ($c_\\Delta$) and the core radius for the NSIS profile (\\rc), which are related to the lowest cluster redshift ($z_{\\rm cut}$) where strong arcs can be observed. For NFW dark matter profiles, we infer cluster haloes with concentrations tha...

  15. Dark matter halo assembly bias: environmental dependence in the non-Markovian excursion set theory

    CERN Document Server

    Zhang, Jun; Riotto, Antonio

    2013-01-01

    In the standard excursion set model for the growth of structure, the statistical properties of haloes are governed by the halo mass and are independent of the larger scale environment in which the haloes reside. Numerical simulations, however, have found the spatial distributions of haloes to depend not only on their mass but also on the details of their assembly history and environment. Here we present a theoretical framework for incorporating this "assembly bias" into the excursion set model. Our derivations are based on modifications of the path integral approach of Maggiore & Riotto (2010) that models halo formation as a non-Markovian random walk process. The perturbed density field is assumed to evolve stochastically with the smoothing scale and exhibits correlated walks in the presence of a density barrier. We write down conditional probabilities for multiple barrier crossings, and derive from them analytic expressions for descendant and progenitor halo mass functions and halo merger rates as a func...

  16. New detections of embedded clusters in the Galactic halo

    Science.gov (United States)

    Camargo, D.; Bica, E.; Bonatto, C.

    2016-09-01

    Context. Until recently it was thought that high Galactic latitude clouds were a non-star-forming ensemble. However, in a previous study we reported the discovery of two embedded clusters (ECs) far away from the Galactic plane (~ 5 kpc). In our recent star cluster catalogue we provided additional high and intermediate latitude cluster candidates. Aims: This work aims to clarify whether our previous detection of star clusters far away from the disc represents just an episodic event or whether star cluster formation is currently a systematic phenomenon in the Galactic halo. We analyse the nature of four clusters found in our recent catalogue and report the discovery of three new ECs each with an unusually high latitude and distance from the Galactic disc midplane. Methods: The analysis is based on 2MASS and WISE colour-magnitude diagrams (CMDs), and stellar radial density profiles (RDPs). The CMDs are built by applying a field-star decontamination procedure, which uncovers the cluster's intrinsic CMD morphology. Results: All of these clusters are younger than 5 Myr. The high-latitude ECs C 932, C 934, and C 939 appear to be related to a cloud complex about 5 kpc below the Galactic disc, under the Local arm. The other clusters are above the disc, C 1074 and C 1100 with a vertical distance of ~3 kpc, C 1099 with ~ 2 kpc, and C 1101 with ~1.8 kpc. Conclusions: According to the derived parameters ECs located below and above the disc occur, which gives evidence of widespread star cluster formation throughout the Galactic halo. This study therefore represents a paradigm shift, by demonstrating that a sterile halo must now be understood as a host for ongoing star formation. The origin and fate of these ECs remain open. There are two possibilities for their origin, Galactic fountains or infall. The discovery of ECs far from the disc suggests that the Galactic halo is more actively forming stars than previously thought. Furthermore, since most ECs do not survive the infant

  17. Mechanics of extended masses in general relativity

    CERN Document Server

    Harte, Abraham I

    2011-01-01

    The "external" or "bulk" motion of extended bodies is studied in general relativity. Material objects of arbitrary shape, spin, internal composition, and velocity are allowed as long as the metric remains near a vacuum solution (with a possible cosmological constant). Under this restriction, physically reasonable linear and angular momenta are proposed that evolve as though they were the momenta of an extended test body moving in an effective vacuum metric. This result holds to all multipole orders. The portion of the physical metric that does not directly affect the motion is a slightly generalized form of the Detweiler-Whiting S-field originally introduced in the context of self-force. This serves only to (finitely) renormalize the "bare" multipole moments of the object's stress-energy tensor. The MiSaTaQu expression for the gravitational self-force is recovered as a simple application. A gravitational self-torque is obtained as well. Lastly, a certain exact result is derived that may provide a basis for un...

  18. NIHAO III: the constant disc gas mass conspiracy

    Science.gov (United States)

    Stinson, G. S.; Dutton, A. A.; Wang, L.; Macciò, A. V.; Herpich, J.; Bradford, J. D.; Quinn, T. R.; Wadsley, J.; Keller, B.

    2015-11-01

    We show that the cool gas masses of galactic discs reach a steady state that lasts many Gyr after their last major merger in cosmological hydrodynamic simulations. The mass of disc gas, Mgas, depends mostly upon a galaxy virial mass and halo's spin, and less upon stellar feedback. Haloes with low spin have high star formation efficiency and lower disc gas mass. Similarly, lower stellar feedback leads to more star formation so the gas mass ends up being nearly the same regardless of stellar feedback strength. Rather than regulating cool gas mass, stellar feedback regulates the mass of stars that forms. Even considering spin, the Mgas relation with halo mass, M200 only shows a factor of 3 scatter. The simulated Mgas-M200 relation shows a break at M200 = 2 × 1011 M⊙ that corresponds to an observed break in the Mgas-M⋆ relation. The galaxies that maintain constant disc masses share a common halo gas density profile shape in all the simulated galaxies. In their outer regions, the profiles are isothermal. Where the profile rises above n = 10-3 cm-3, the gas readily cools and the profile steepens. Inside the disc, rotation supports gas with a flatter density profile. Energy injection from stellar feedback provides pressure support to the halo gas to prevent runaway cooling flows. The constant gas mass makes simpler models for galaxy formation possible, either using a `bathtub' model for star formation rates or when modelling chemical evolution.

  19. The Relation Between the Globular Cluster Mass and Luminosity Functions

    CERN Document Server

    Kruijssen, J M Diederik

    2009-01-01

    The relation between the globular cluster luminosity function (GCLF, dN/dlogL) and globular cluster mass function (GCMF, dN/dlogM) is considered. Due to low-mass star depletion, dissolving GCs have mass-to-light (M/L) ratios that are lower than expected from their metallicities. This has been shown to lead to an M/L ratio that increases with GC mass and luminosity. We model the GCLF and GCMF and show that the power law slopes inherently differ (1.0 versus 0.7, respectively) when accounting for the variability of M/L. The observed GCLF is found to be consistent with a Schechter-type initial cluster mass function and a mass-dependent mass-loss rate.

  20. The Age of the Milky Way Inner Halo

    CERN Document Server

    Kalirai, Jason

    2012-01-01

    The Milky Way galaxy is observed to have multiple components with distinct properties, such as the bulge, disk, and halo. Unraveling the assembly history of these populations provides a powerful test to the theory of galaxy formation and evolution, but is often restricted due to difficulties in measuring accurate stellar ages for low mass, hydrogen-burning stars. Unlike these progenitors, the "cinders" of stellar evolution, white dwarf stars, are remarkably simple objects and their fundamental properties can be measured with little ambiguity from spectroscopy. Here I report observations of newly formed white dwarf stars in the halo of the Milky Way, and a separate analysis of archival data on white dwarfs in the well-studied 12.5 billion year old globular cluster Messier 4. From this, I measure the mass distribution of the remnants and invert the stellar evolution process to develop a new relation that links this final stellar mass to the mass of their immediate progenitors, and therefore to the age of the pa...

  1. Theoretical reevaluations of black hole mass -- bulge mass relation - I. Influences of the seed black hole mass

    CERN Document Server

    Shirakata, Hikari; Okamoto, Takashi; Makiya, Ryu; Ishiyama, Tomoaki; Matsuoka, Yoshiki; Nagashima, Masahiro; Enoki, Motohiro; Oogi, Taira; Kobayashi, Masakazu A R

    2016-01-01

    We show influences of the mass of seed black holes on black hole mass -- bulge mass relation at z ~ 0 by using a semi-analytic model of galaxy formation combined with large cosmological N-body simulations. We constrain our model to reproduce observed properties of galaxies at z ~ 0. Similar to other semi-analytic models, we place a seed black hole immediately after a galaxy forms. When we set the seed black hole mass to 10^5 M_sun, we find that the model result becomes inconsistent with recent observational results of black hole mass -- bulge mass relation for dwarf galaxies. Namely, the model predicts that bulges with ~ 10^9 M_sun harbor black holes more massive than observed. On the other hand, when we employ seed black holes with 10^3 M_sun or randomly choose their masses in the range of 10^{3-5} M_sun, the black hole mass -- bulge mass relation obtained from these models are consistent with observational results including dispersions. We find that to obtain more stringent restrictions of the mass of seed ...

  2. Initial mass function of intermediate mass black hole seeds

    CERN Document Server

    Ferrara, A; Yue, B; Schleicher, D R G

    2014-01-01

    We study the Initial Mass Function (IMF) and host halo properties of Intermediate Mass Black Holes (IMBH, 10^{4-6} Msun) formed inside metal-free, UV illuminated atomic cooling haloes (virial temperature T_vir > 10^4 K) either via the direct collapse of the gas or via an intermediate Super Massive Star (SMS) stage. We achieve this goal in three steps: (a) we derive the gas accretion rate for a proto-SMS to undergo General Relativity instability and produce a direct collapse black hole (DCBH) or to enter the ZAMS and later collapse into a IMBH; (b) we use merger-tree simulations to select atomic cooling halos in which either a DCBH or SMS can form and grow, accounting for metal enrichment and major mergers that halt the growth of the proto-SMS by gas fragmentation. We derive the properties of the host halos and the mass distribution of black holes at this stage, and dub it the "Birth Mass Function"; (c) we follow the further growth of the DCBH due to accretion of leftover gas in the parent halo and compute the...

  3. The Origin of Angular Momentum in Dark Matter Halos

    Science.gov (United States)

    Vitvitska, Maya; Klypin, Anatoly A.; Kravtsov, Andrey V.; Wechsler, Risa H.; Primack, Joel R.; Bullock, James S.

    2002-12-01

    We propose a new explanation for the origin of angular momentum in galaxies and their dark halos, in which the halos obtain their spin through the cumulative acquisition of angular momentum from satellite accretion. In our model, the buildup of angular momentum is a random walk process associated with the mass assembly history of the halo's major progenitor. We assume no correlation between the angular momenta of accreted objects. The main role of tidal torques in this approach is to produce the random tangential velocities of merging satellites. Using the extended Press-Schechter approximation, we calculate the growth of mass, angular momentum, and spin parameter λ for many halos. Our random walk model reproduces the key features of the angular momentum of halos found in ΛCDM N-body simulations: a lognormal distribution in λ with an average of ~0.045 and dispersion σλ=0.56, independent of mass and redshift. The evolution of the spin parameter in individual halos in this model is quite different from the steady increase with time of angular momentum in the tidal torque picture. We find both in N-body simulations and in our random walk model that the value of λ changes significantly with time for a halo's major progenitor. It typically has a sharp increase due to major mergers and a steady decline during periods of gradual accretion of small satellites. The model predicts that, on average, the λ of ~1012 Msolar halos that had major mergers after redshift z=3 should be substantially larger than the λ of those that did not. Perhaps surprisingly, this suggests that halos that host later forming elliptical galaxies should rotate faster than halos of spiral galaxies.

  4. The properties of warm dark matter haloes

    CERN Document Server

    Lovell, Mark R; Eke, Vincent R; Jenkins, Adrian; Gao, Liang; Theuns, Tom

    2013-01-01

    Well-motivated elementary particle candidates for the dark matter, such as the sterile neutrino, behave as warm dark matter (WDM).For particle masses of order a keV, free streaming produces a cutoff in the linear fluctuation power spectrum at a scale corresponding to dwarf galaxies. We investigate the abundance and structure of WDM haloes and subhaloes on these scales using high resolution cosmological N-body simulations of galactic haloes of mass similar to the Milky Way's. On scales larger than the free-streaming cutoff, the initial conditions have the same power spectrum and phases as one of the cold dark matter (CDM) haloes previously simulated by Springel et al as part of the Virgo consortium Aquarius project. We have simulated four haloes with WDM particle masses in the range 1.4-2.3keV and, for one case, we have carried out further simulations at varying resolution. N-body simulations in which the power spectrum cutoff is resolved are known to undergo artificial fragmentation in filaments producing spu...

  5. Dark energy and extended dark matter halos

    Science.gov (United States)

    Chernin, A. D.; Teerikorpi, P.; Valtonen, M. J.; Dolgachev, V. P.; Domozhilova, L. M.; Byrd, G. G.

    2012-03-01

    The cosmological mean matter (dark and baryonic) density measured in the units of the critical density is Ωm = 0.27. Independently, the local mean density is estimated to be Ωloc = 0.08-0.23 from recent data on galaxy groups at redshifts up to z = 0.01-0.03 (as published by Crook et al. 2007, ApJ, 655, 790 and Makarov & Karachentsev 2011, MNRAS, 412, 2498). If the lower values of Ωloc are reliable, as Makarov & Karachentsev and some other observers prefer, does this mean that the Local Universe of 100-300 Mpc across is an underdensity in the cosmic matter distribution? Or could it nevertheless be representative of the mean cosmic density or even be an overdensity due to the Local Supercluster therein. We focus on dark matter halos of groups of galaxies and check how much dark mass the invisible outer layers of the halos are able to host. The outer layers are usually devoid of bright galaxies and cannot be seen at large distances. The key factor which bounds the size of an isolated halo is the local antigravity produced by the omnipresent background of dark energy. A gravitationally bound halo does not extend beyond the zero-gravity surface where the gravity of matter and the antigravity of dark energy balance, thus defining a natural upper size of a system. We use our theory of local dynamical effects of dark energy to estimate the maximal sizes and masses of the extended dark halos. Using data from three recent catalogs of galaxy groups, we show that the calculated mass bounds conform with the assumption that a significant amount of dark matter is located in the invisible outer parts of the extended halos, sufficient to fill the gap between the observed and expected local matter density. Nearby groups of galaxies and the Virgo cluster have dark halos which seem to extend up to their zero-gravity surfaces. If the extended halo is a common feature of gravitationally bound systems on scales of galaxy groups and clusters, the Local Universe could be typical or even

  6. An analytic model for the gravitational clustering of dark matter haloes

    CERN Document Server

    Mo, H J; Mo, H J; White, S D M

    1994-01-01

    We develop a simple analytic model for the gravitational clustering of dark haloes. The statistical properties of dark haloes are determined from the initial density field (assumed to be Gaussian) through an extension of the Press-Schechter formalism. Gravitational clustering is treated by a spherical model which describes the concentration of dark haloes in collapsing regions. We test this model against results from a variety of N-body simulations. The autocorrelation function of dark haloes in such simulations depends significantly on how haloes are identified. Our predictions agree well with results based on algorithms which break clusters into subgroups more efficiently than the standard friends-of-friends algorithm. The agreement is better than that found by assuming haloes to lie at the present positions of peaks of the linear density field. We use these techniques to study how the distribution of haloes is biased with respect to that of the mass. The initial (Lagrangian) positions of haloes identified ...

  7. Origins of Stellar Halos

    Science.gov (United States)

    Johnston, Kathryn V.

    2016-08-01

    This contribution reviews ideas about the origins of stellar halos. It includes discussion of the theoretical understanding of and observational evidence for stellar populations formed ``in situ'' (meaning formed in orbits close to their current ones), ``kicked-out'' (meaning formed in the inner galaxy in orbits unlike their current ones) and ``accreted'' (meaning formed in a dark matter halo other than the one they currently occupy). At this point there is general agreement that a significant fraction of any stellar halo population is likely ``accreted''. There is modest evidence for the presence of a ``kicked-out'' population around both the Milky Way and M31. Our theoretical understanding of and the observational evidence for an ``in situ'' population are less clear.

  8. The Impact of Baryonic Physics on the Structure of Dark Matter Halos: the View from the FIRE Cosmological Simulations

    Science.gov (United States)

    Keung Chan, Tsang; Keres, Dusan; Oñorbe, Jose; Hopkins, Philip F.; Muratov, Alexander; Faucher-Giguere, Claude-Andre; Quataert, Eliot

    2016-06-01

    We study the distribution of cold dark matter (CDM) in cosmological simulations from the FIRE (Feedback In Realistic Environments) project, which incorporates explicit stellar feedback in the multi-phase ISM, with energetics from stellar population models. We find that stellar feedback, without ``fine-tuned'' parameters, greatly alleviates small-scale problems in CDM. Feedback causes bursts of star formation and outflows, altering the DM distribution. As a result, the inner slope of the DM halo profile (α) shows a strong mass dependence: profiles are shallow at Mh ˜ 1010-1011 M⊙ and steepen at higher/lower masses. The resulting core sizes and slopes are consistent with observations. Because the star formation efficiency, Ms/Mh is strongly halo mass dependent, a rapid change in α occurs around Mh ˜1010M⊙, (Ms˜106-107M⊙) as sufficient feedback energy becomes available to perturb the DM. Large cores are not established during the period of rapid growth of halos because of ongoing DM mass accumulation. Instead, cores require several bursts of star formation after the rapid buildup has completed. Stellar feedback dramatically reduces circular velocities in the inner kpc of massive dwarfs; this could be sufficient to explain the ``Too Big To Fail'' problem without invoking non-standard DM. Finally, feedback and baryonic contraction in Milky Way-mass halos produce DM profiles slightly shallower than the Navarro-Frenk-White profile, consistent with the normalization of the observed Tully-Fisher relation.

  9. Scaling relations for galaxies prior to reionization

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Pengfei; Norman, Michael L.; Xu, Hao [CASS, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093 (United States); Wise, John H. [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, GA 30332 (United States); O' Shea, Brian W., E-mail: pec008@ucsd.edu, E-mail: mlnorman@ucsd.edu, E-mail: hxu@ucsd.edu, E-mail: jwise@gatech.edu, E-mail: oshea@msu.edu [Lyman Briggs College and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)

    2014-11-10

    The first galaxies in the universe are the building blocks of all observed galaxies. We present scaling relations for galaxies forming at redshifts z ≥ 15 when reionization is just beginning. We utilize the 'Rarepeak' cosmological radiation hydrodynamics simulation that captures the complete star formation history in over 3300 galaxies, starting with massive Population III stars that form in dark matter halos as small as ∼10{sup 6} M {sub ☉}. We make various correlations between the bulk halo quantities, such as virial, gas, and stellar masses and metallicities and their respective accretion rates, quantifying a variety of properties of the first galaxies up to halo masses of 10{sup 9} M {sub ☉}. Galaxy formation is not solely relegated to atomic cooling halos with virial temperatures greater than 10{sup 4} K, where we find a dichotomy in galaxy properties between halos above and below this critical mass scale. Halos below the atomic cooling limit have a stellar mass-halo mass relationship log M {sub *} ≅ 3.5 + 1.3log (M {sub vir}/10{sup 7} M {sub ☉}). We find a non-monotonic relationship between metallicity and halo mass for the smallest galaxies. Their initial star formation events enrich the interstellar medium and subsequent star formation to a median of 10{sup –2} Z {sub ☉} and 10{sup –1.5} Z {sub ☉}, respectively, in halos of total mass 10{sup 7} M {sub ☉}, which is then diluted by metal-poor inflows well beyond Population III pre-enrichment levels of 10{sup –3.5} Z {sub ☉}. The scaling relations presented here can be employed in models of reionization, galaxy formation, and chemical evolution in order to consider these galaxies forming prior to reionization.

  10. Statistics of Dark Matter Halos from the Excursion Set Approach

    CERN Document Server

    Lapi, A; Danese, L

    2013-01-01

    We exploit the excursion set approach in integral formulation to derive novel, accurate analytic approximations of the unconditional and conditional first crossing distributions, for random walks with uncorrelated steps and general shapes of the moving barrier; we find the corresponding approximations of the unconditional and conditional halo mass functions for Cold Dark Matter power spectra to represent very well the outcomes of state-of-the-art cosmological N-body simulations. In addition, we apply these results to derive and confront with simulations other quantities of interest in halo statistics, including the rates of halo formation and creation, the average halo growth history, and the halo bias. Finally, we discuss how our approach and main results change when considering random walks with correlated instead of uncorrelated steps, and Warm instead of Cold Dark Matter power spectra.

  11. Scale Radii and Aggregation Histories of Dark Haloes

    CERN Document Server

    Salvador-Solé, E; Solanes, J M; Salvador-Sole, Eduard; Manrique, Alberto; Solanes, Jose M.

    2005-01-01

    Relaxed dark-matter haloes are found to exhibit the same universal density profiles regardless of whether they form in hierarchical cosmologies or via spherical collapse. Likewise, the shape parameters of haloes formed hierarchically do not seem to depend on the epoch in which the last major merger took place. Both findings suggest that the density profile of haloes does not depend on their aggregation history. Yet, this possibility is apparently at odds with some correlations involving the scale radius r_s found in numerical simulations. Here we prove that the scale radius of relaxed, non-rotating, spherically symmetric haloes endowed with the universal density profile is determined exclusively by the current values of four independent, though correlated, quantities: mass, energy and their respective instantaneous accretion rates. Under this premise and taking into account the inside-out growth of haloes during the accretion phase between major mergers, we build a simple physical model for the evolution of r...

  12. Evolution of dark-matter halos in numerical models

    Science.gov (United States)

    Pilipenko, S. V.; Doroshkevich, A. G.; Gottlöber, S.

    2009-11-01

    The properties of gravitationally bound clouds (halos) of dark matter derived via numerical simulations of the distribution of dark matter in the Universe are investigated. The analysis makes use of a catalog of halos obtained in the European “MareNostrum Universe” project, which has achieved a better balance between resolution and representativeness than catalogs used earlier for similar studies. This has made it possible to refine the main tendencies displayed by the evolution of the halo masses and the angular velocities and density profiles of the halos. The results are compared with the newest available observational data and with known results obtained earlier in numerical simulations with lower resolution and using smaller samples of halos, making it possible to trace the influence of these factors on the results obtained. Disagreements between observations and numerical models obtained in earlier studies are confirmed, and possible ways to explain them discussed.

  13. Can Massive Dark Haloes Destroy the Disks of Dwarf Galaxies?

    CERN Document Server

    Fuchs, B

    2007-01-01

    Recent high-resolution simulations together with theoretical studies of the dynamical evolution of galactic disks have shown that contrary to wide-held beliefs a `live', dynamically responsive, dark halo surrounding a disk does not stabilize the disk against dynamical instabilities. We generalize Toomre's Q stability parameter for a disk-halo system and show that if a disk, which would be otherwise stable, is embedded in a halo, which is too massive and cold, the combined disk-halo system can become locally Jeans unstable. The good news is, on the other hand, that this will not happen in real dark haloes, which are in radial hydrostatic equilibrium. Even very low-mass disks are not prone to such dynamical instabilities.

  14. Halo Concentration and the Dark Matter Power Spectrum

    CERN Document Server

    Huffenberger, Kevin M; Huffenberger, Kevin M.; Seljak, Uros

    2003-01-01

    We explore the connection between halo concentration and the dark matter power spectrum using the halo model. We fit halo model parameters to non-linear power spectra over a large range of cosmological models. We find that the non-linear evolution of the power spectrum generically prefers the concentration at non-linear mass scale to decrease with the effective slope of the linear power spectrum, in agreement with the direct analysis of the halo structure in different cosmological models. Using these analyses, we compute the predictions for non-linear power spectrum beyond the current resolution of N-body simulations. We find that the halo model predictions are generically below the analytical non-linear models, suggesting that the latter may overestimate the amount of power on small scales.

  15. THE PANCHROMATIC HUBBLE ANDROMEDA TREASURY. II. TRACING THE INNER M31 HALO WITH BLUE HORIZONTAL BRANCH STARS

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Benjamin F.; Dalcanton, Julianne J.; Gilbert, Karoline M.; Rosenfield, Philip [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Bell, Eric F. [Department of Astronomy, University of Michigan, 550 Church St., Ann Arbor MI 48109 (United States); Guhathakurta, Puragra [UCO/Lick Observatory, Astronomy and Astrophysics Department, University of California, Santa Cruz, CA 95064 (United States); Lauer, Tod R. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Seth, Anil C. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Kalirai, Jason S. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Girardi, Leo, E-mail: ben@astro.washington.edu, E-mail: jd@astro.washington.edu, E-mail: kgilbert@astro.washington.edu, E-mail: philrose@astro.washington.edu, E-mail: ericbell@umich.edu, E-mail: raja@uco.lick.org, E-mail: lauer@noao.edu, E-mail: aseth@astro.utah.edu, E-mail: jkalirai@stsci.edu, E-mail: lgirardi@pd.astro.it [Osservatorio Astronomico di Padova-INAF, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy)

    2012-11-01

    We attempt to constrain the shape of M31's inner stellar halo by tracing the surface density of blue horizontal branch (BHB) stars at galactocentric distances ranging from 2 kpc to 35 kpc. Our measurements make use of resolved stellar photometry from a section of the Panchromatic Hubble Andromeda Treasury survey, supplemented by several archival Hubble Space Telescope observations. We find that the ratio of BHB to red giant stars is relatively constant outside of 10 kpc, suggesting that the BHB is as reliable a tracer of the halo population as the red giant branch. In the inner halo, we do not expect BHB stars to be produced by the high-metallicity bulge and disk, making BHB stars a good candidate to be a reliable tracer of the stellar halo to much smaller galactocentric distances. If we assume a power-law profile r {sup -{alpha}} for the two-dimensional (2D) projected surface density BHB distribution, we obtain a high-quality fit with a 2D power-law index of {alpha} = 2.6{sup +0.3} {sub -0.2} outside of 3 kpc, which flattens to {alpha} < 1.2 inside of 3 kpc. This slope is consistent with previous measurements but is anchored to a radial baseline that extends much farther inward. Finally, assuming azimuthal symmetry and a constant mass-to-light ratio, the best-fitting profile yields a total halo stellar mass of 2.1{sup +1.7} {sub -0.4} Multiplication-Sign 10{sup 9} M {sub Sun }. These properties are comparable with both simulations of stellar halo formation by satellite disruption alone and simulations that include some in situ formation of halo stars.

  16. Theoretical re-evaluations of the black hole mass-bulge mass relation - I. Effect of seed black hole mass

    Science.gov (United States)

    Shirakata, Hikari; Kawaguchi, Toshihiro; Okamoto, Takashi; Makiya, Ryu; Ishiyama, Tomoaki; Matsuoka, Yoshiki; Nagashima, Masahiro; Enoki, Motohiro; Oogi, Taira; Kobayashi, Masakazu A. R.

    2016-10-01

    We explore the effect of varying the mass of a seed black hole on the resulting black hole mass-bulge mass relation at z ˜ 0, using a semi-analytic model of galaxy formation combined with large cosmological N-body simulations. We constrain our model by requiring that the observed properties of galaxies at z ˜ 0 are reproduced. In keeping with previous semi-analytic models, we place a seed black hole immediately after a galaxy forms. When the mass of the seed is set at 105 M⊙, we find that the model results become inconsistent with recent observational results of the black hole mass-bulge mass relation for dwarf galaxies. In particular, the model predicts that bulges with ˜109 M⊙ harbour larger black holes than observed. On the other hand, when we employ seed black holes of 103 M⊙ or select their mass randomly within a 103-5 M⊙ range, the resulting relation is consistent with observation estimates, including the observed dispersion. We find that, to obtain stronger constraints on the mass of seed black holes, observations of less massive bulges at z ˜ 0 are a more powerful comparison than the relations at higher redshifts.

  17. Stellar populations across the black hole mass - velocity dispersion relation

    CERN Document Server

    Martín-Navarro, Ignacio; Bosch, Remco C E van den; Romanowsky, Aaron J; Forbes, Duncan A

    2016-01-01

    Coevolution between supermassive black holes (BHs) and their host galaxies is universally adopted in models for galaxy formation. In the absence of feedback from active galactic nuclei, simulated massive galaxies keep forming stars in the local Universe. From an observational point of view, however, such coevolution remains unclear. We present a stellar population analysis of galaxies with direct BH mass measurements and the BH mass-{\\sigma} relation as a working framework. We find that over-massive BH galaxies, i.e., galaxies lying above the best-fitting BH mass-{\\sigma} line, tend to be older and more {\\alpha}-element enhanced than under-massive BH galaxies. The scatter in the BH mass-{\\sigma}-[{\\alpha}/Fe] plane is significantly lower than in the standard BH mass-{\\sigma} relation. We interpret this trend as an imprint of active galactic nucleus feedback on the star formation histories of massive galaxies.

  18. Cookie-cutter halos: the remarkable constancy of the stellar mass function of satellite galaxies at 0.2

    CERN Document Server

    Tal, Tomer; Muzzin, Adam; Marchesini, Danilo; Stefanon, Mauro

    2014-01-01

    We present an observational study of the stellar mass function of satellite galaxies around central galaxies at 0.2mass distributions in four bins of central galaxy mass in three redshift ranges. Our results show that the stellar mass function of satellite galaxies increases with central galaxy mass, and that the distribution of satellite masses at fixed central mass is at most weakly dependent on redshift. We conclude that the average mass distribution of galaxies in groups is remarkably universal even out to z=1.2 and that it can be uniquely characterized by the group central galaxy mass. This further suggests that as central galaxies grow in stellar mass, they do so in tandem with the mass growth of their satellites. Finally, we classify all galaxies as either star forming or quiescent, and derive the mass functions of each subpopulation separately. We find that the mass distribution of both star for...

  19. Touching the void: A striking drop in stellar halo density beyond 50 kpc

    Energy Technology Data Exchange (ETDEWEB)

    Deason, A. J.; Rockosi, C. M. [Department of Astronomy and Astrophysics, University of California Santa Cruz, Santa Cruz, CA 95064 (United States); Belokurov, V.; Koposov, S. E., E-mail: alis@ucolick.org [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom)

    2014-05-20

    We use A-type stars selected from Sloan Digital Sky Survey data release 9 photometry to measure the outer slope of the Milky Way stellar halo density profile beyond 50 kpc. A likelihood-based analysis is employed that models the ugr photometry distribution of blue horizontal branch and blue straggler stars. In the magnitude range 18.5 < g < 20.5, these stellar populations span a heliocentric distance range of: 10 ≲ D {sub BS}/kpc ≲ 75, 40 ≲ D {sub BHB}/kpc ≲ 100. Contributions from contaminants, such as QSOs, and the effect of photometric uncertainties, are also included in our modeling procedure. We find evidence for a very steep outer halo profile, with power-law index α ∼ 6 beyond Galactocentric radii r = 50 kpc, and even steeper slopes favored (α ∼ 6-10) at larger radii. This result holds true when stars belonging to known overdensities, such as the Sagittarius stream, are included or excluded. We show that, by comparison to numerical simulations, stellar halos with shallower slopes at large distances tend to have more recent accretion activity. Thus, it is likely that the Milky Way has undergone a relatively quiet accretion history over the past several gigayears. Our measurement of the outer stellar halo profile may have important implications for dynamical mass models of the Milky Way, where the tracer density profile is strongly degenerate with total mass estimates.

  20. Orbital parameters of infalling satellite haloes in the hierarchical $\\Lambda$CDM model

    CERN Document Server

    Jiang, Lilian; Sawala, Till; Frenk, Carlos S

    2014-01-01

    We present distributions of orbital parameters of infalling satellites of $\\Lambda$CDM haloes in the mass range $10^{12}-10^{14}$M$_\\odot$, which represent the initial conditions for the subsequent evolution of substructures within the host halo. We use merger trees constructed in a high resolution cosmological N-body simulation to trace satellite haloes, and identify the time of infall. We find signficant trends in the distribution of orbital parameters with both the host halo mass and the ratio of satellite-to-host halo masses. For all host halo masses, satellites whose infall mass is a larger fraction of the host halo mass have more eccentric, radially biased orbits. At fixed satellite-to-host halo mass ratio, high mass haloes are biased towards accreting satellites on slightly more biased orbits. To charactise the orbital distributions fully requires fitting the correlated bivariate distribution of two chosen orbital parameters (e.g. radial and tangential velocity or energy and angular momentu). We provid...

  1. Satellite quenching, Galaxy inner density and the halo environment

    Science.gov (United States)

    Woo, Joanna; Carollo, C. M.; Faber, S. M.; Dekel, Avishai; Tacchella, Sandro

    2017-01-01

    Using the Sloan Digital Sky Survey, we adopt the specific star formation rate (sSFR)-Σ*,1kpc diagram as a diagnostic tool to understand quenching in different environments. sSFR is the specific star formation rate and Σ*,1kpc is the stellar surface density in the inner kpc. Although both the host halo mass and group-centric distance affect the satellite population, we find that these can be characterized by a single number, the quenched fraction, such that key features of the sSFR-Σ*,1kpc diagram vary smoothly with this proxy for the `environment'. Particularly, the sSFR of star-forming galaxies decreases smoothly with this quenched fraction, the sSFR of satellites being 0.1 dex lower than in the field. Furthermore, Σ*,1kpc of the transition galaxies (i.e. the `green valley' or GV) decreases smoothly with the environment by as much as 0.2 dex for M* = 109.75-10 from the field, and decreasing for satellites in larger haloes and at smaller radial distances within same-mass haloes. We interpret this shift as indicating the relative importance of today's field quenching track versus the cluster quenching track. These environmental effects in the sSFR-Σ*,1kpc diagram are most significant in our lowest mass range (9.75 < log M*/M⊙ < 10). One feature that is shared between all environments is that at a given M*, quenched galaxies have about 0.2-0.3 dex higher Σ*,1kpc than the star-forming population. These results indicate that either Σ*,1kpc increases (subsequent to satellite quenching), or Σ*,1kpc for individual galaxies remains unchanged, but the original M* or the time of quenching is significantly different from those now in the GV.

  2. ZOMG I: How the cosmic web inhibits halo growth and generates assembly bias

    CERN Document Server

    Borzyszkowski, Mikolaj; Romano-Diaz, Emilio; Garaldi, Enrico

    2016-01-01

    The clustering of dark-matter haloes with fixed mass depends on their formation history, an effect known as assembly bias. We investigate the origin of this phenomenon using zoom N-body simulations. We follow the formation of seven galaxy-sized haloes selected using a definition of collapse time that generates strong assembly bias. Haloes at redshift zero are classified according to the time in which the physical volume containing their final mass becomes stable. For `stalled' haloes this happens at z~1.5 while for `accreting' haloes this has not happened yet. The zoom simulations confirm that stalled haloes do not grow in mass while accreting haloes show a net inflow. The reason is that accreting haloes are located at the nodes of a network of thin filaments which feed them. Conversely, each stalled halo lies within a prominent filament that is thicker than the halo size. Infalling material from the surroundings becomes part of the filament while matter within it recedes from the halo. We conclude that assem...

  3. The Evolution of Dark Matter Halo Properties in Clusters, Filaments, Sheets and Voids

    CERN Document Server

    Hahn, Oliver; Porciani, Cristiano; Dekel, Avishai

    2007-01-01

    We use a series of N-body simulations of the LCDM cosmology to investigate the redshift evolution since z=1 of the properties and alignment with the large-scale structure of haloes in clusters, filaments, sheets and voids. We find that: (i) Once a rescaling of the halo mass with M*, the mass scale collapsing at redshift z, is performed, there is no further significant redshift dependence in the halo properties; (ii) The environment influences