Halo Mass Mh Research Articles

Warm Dark Matter Galaxies with Central Supermassive Black Holes

We generalize the Thomas–Fermi approach to galaxy structure to include central supermassive black holes and find, self-consistently and non-linearly, the gravitational potential of the galaxy plus the central black hole (BH) system. This approach naturally incorporates the quantum pressure of the fermionic warm dark matter (WDM) particles and shows its full power and clearness in the presence of supermassive black holes. We find the main galaxy and central black hole magnitudes as the halo radius rh, halo mass Mh, black hole mass MBH, velocity dispersion σ, and phase space density, with their realistic astrophysical values, masses and sizes over a wide galaxy range. The supermassive black hole masses arise naturally in this framework. Our extensive numerical calculations and detailed analytic resolution of the Thomas–Fermi equations show that in the presence of the central BH, both DM regimes—classical (Boltzmann dilute) and quantum (compact)—do necessarily co-exist generically in any galaxy, from the smaller and compact galaxies to the largest ones. The ratio R(r) of the particle wavelength to the average interparticle distance shows consistently that the transition, R≃1, from the quantum to the classical region occurs precisely at the same point rA where the chemical potential vanishes. A novel halo structure with three regions shows up: in the vicinity of the BH, WDM is always quantum in a small compact core of radius rA and nearly constant density; in the region rA<r<ri until the BH influence radius ri, WDM is less compact and exhibits a clear classical Boltzmann-like behavior; for r>ri, the WDM gravity potential dominates, and the known halo galaxy shows up with its astrophysical size. DM is a dilute classical gas in this region. As an illustration, three representative families of galaxy plus central BH solutions are found and analyzed: small, medium and large galaxies with realistic supermassive BH masses of 105M⊙, 107M⊙ and 109M⊙, respectively. In the presence of the central BH, we find a minimum galaxy size and mass Mhmin≃107M⊙, larger (2.2233×103 times) than the one without BH, and reached at a minimal non-zero temperature Tmin. The supermassive BH heats up the DM and prevents it from becoming an exactly degenerate gas at zero temperature. Colder galaxies are smaller, and warmer galaxies are larger. Galaxies with a central black hole have large masses Mh>107M⊙>Mhmin; compact or ultracompact dwarf galaxies in the range 104M⊙<Mh<107M⊙ cannot harbor central BHs. We find novel scaling relations MBH=DMh38 and rh=CMBH43, and show that the DM galaxy scaling relations Mh=bΣ0rh2 and Mh=aσh4/Σ0 hold too in the presence of the central BH, Σ0 being the constant surface density scale over a wide galaxy range. The galaxy equation of state is derived: pressure P(r) takes huge values in the BH vicinity region and then sharply decreases entering the classical region, following consistently a self-gravitating perfect gas P(r)=σ2ρ(r) behavior.

A universal relation between the properties of supermassive black holes, galaxies, and dark matter haloes

ABSTRACT We study the relations between the mass of the central black hole (BH) MBH, the dark matter halo mass Mh, and the stellar-to-halo mass fraction f⋆∝M⋆/Mh in a sample of 55 nearby galaxies with dynamically measured $M_{\rm BH}\gt 10^6\, {\rm M}_\odot$ and $M_{\rm h}\gt 5\times 10^{11}\, {\rm M}_\odot$. The main improvement with respect to previous studies is that we consider both early- and late-type systems for which Mh is determined either from globular cluster dynamics or from spatially resolved rotation curves. Independently of their structural properties, galaxies in our sample build a well defined sequence in the MBH–Mh–f⋆ space. We find that: (i) Mh and MBH strongly correlate with each other and anticorrelate with f⋆; (ii) there is a break in the slope of the MBH–Mh relation at Mh of $10^{12}\, {\rm M}_\odot$, and in the f⋆–MBH relation at MBH of $\sim 10^7\!-\!10^8\, {\rm M}_\odot$; (iii) at a fixed MBH, galaxies with a larger f⋆ tend to occupy lighter haloes and to have later morphological types. We show that the observed trends can be reproduced by a simple equilibrium model in the ΛCDM framework where galaxies smoothly accrete dark and baryonic matter at a cosmological rate, having their stellar and BH build-up regulated both by the cooling of the available gas reservoir and by the negative feedback from star formation and active galactic nuclei (AGNs). Feature (ii) arises as the BH population transits from a rapidly accreting phase to a more gentle and self-regulated growth, while scatter in the AGN feedback efficiency can account for feature (iii).

Galaxy assembly bias of central galaxies in the Illustris simulation

ABSTRACT Galaxy assembly bias, the correlation between galaxy properties and halo properties at fixed halo mass, could be an important ingredient in halo-based modelling of galaxy clustering. We investigate the central galaxy assembly bias by studying the relation between various galaxy and halo properties in the Illustris hydrodynamic galaxy formation simulation. Galaxy stellar mass M* is found to have a tighter correlation with peak maximum halo circular velocity Vpeak than with halo mass Mh. Once the correlation with Vpeak is accounted for, M* has nearly no dependence on any other halo assembly variables. The correlations between galaxy properties related to star formation history and halo assembly properties also show a cleaner form as a function of Vpeak than as a function of Mh, with the main correlation being with halo formation time and to a less extent halo concentration. Based on the galaxy–halo relation, we present a simple model to relate the bias factors of a central galaxy sample and the corresponding halo sample, both selected based on assembly-related properties. It is found that they are connected by the correlation coefficient of the galaxy and halo properties used to define the two samples, which provides a reasonable description for the samples in the simulation and suggests a simple prescription to incorporate galaxy assembly bias into the halo model. By applying the model to the local galaxy clustering measurements in Lin et al., we infer that the correlation between star formation history or specific star formation rate and halo formation time is consistent with being weak.

Origins of scaling relations of globular cluster systems

ABSTRACT Globular cluster (GC) systems demonstrate tight scaling relations with the properties of their host galaxies. In previous work, we developed an analytic model for GC formation in a cosmological context that matches nearly all of these observed scaling relations. Here, we apply our model to investigate in detail the physical origins and evolution of these scaling relations. The ratio of the combined mass in GCs MGC to the host dark matter halo mass Mh is nearly constant at all redshifts, but its normalization evolves by a factor of ∼10 from birth to z = 0. The relation is steeper than linear at halo masses $M_{\mathrm{h}}\lesssim 10^{11.5}\, \mathrm{M}_{\odot }$, primarily due to non-linearity in the stellar mass–halo mass relation. The near constancy of the ratio MGC/Mh, combined with the shape of the stellar mass–halo mass relation, sets the characteristic U shape of the GC specific frequency as a function of host galaxy mass. The contribution of accreted satellite galaxies to the buildup of GC systems is a strong function of the host galaxy mass, ranging from ≈0 per cent at $M_{\mathrm{h}}\approx 10^{11} \, \mathrm{M}_{\odot }$ to 80 per cent at $M_{\mathrm{h}}\approx 10^{15} \, \mathrm{M}_{\odot }$. The metal-poor clusters are significantly more likely to form ex situ relative to the metal-rich clusters, but a substantial fraction of metal-poor clusters still form in situ in lower mass galaxies. Cluster formation occurs essentially continuously at high redshift, while at low redshift galactic mergers become increasingly important for cluster formation. Consequently, although major mergers form clusters efficiently, they are too rare to form most clusters.

The COSMOS-UltraVISTA stellar-to-halo mass relationship: new insights on galaxy formation efficiency out to z ∼ 5

Abstract Using precise galaxy stellar mass function measurements in the COSMOS field we determine the stellar-to-halo mass relationship (SHMR) using a parametric abundance matching technique. The unique combination of size and highly complete stellar mass estimates in COSMOS allows us to determine the SHMR over a wide range of halo masses from z ∼ 0.2 to 5. At z ∼ 0.2, the ratio of stellar-to-halo mass content peaks at a characteristic halo mass Mh = 1012M⊙ and declines at higher and lower halo masses. This characteristic halo mass increases with redshift reaching Mh = 1012.5M⊙ at z ∼ 2.3 and remaining flat up to z = 4. We considered the principal sources of uncertainty in our stellar mass measurements and also the variation in halo mass estimates in the literature. We show that our results are robust to these sources of uncertainty and explore likely explanation for differences between our results and those published in the literature. The steady increase in characteristic halo mass with redshift points to a scenario where cold gas inflows become progressively more important in driving star formation at high redshifts, but larger samples of massive galaxies are needed to rigorously test this hypothesis.

THE RESOLVE SURVEY ATOMIC GAS CENSUS AND ENVIRONMENTAL INFLUENCES ON GALAXY GAS RESERVOIRS

ABSTRACT We present the H i mass inventory for the REsolved Spectroscopy Of a Local VolumE (RESOLVE) survey, a volume-limited, multi-wavelength census of >1500 z = 0 galaxies spanning diverse environments and complete in baryonic mass down to dwarfs of ∼109 . This first 21 cm data release provides robust detections or strong upper limits (1.4M H i < 5%–10% of stellar mass M *) for ∼94% of RESOLVE. We examine global atomic gas-to-stellar mass ratios (G/S) in relation to galaxy environment using several metrics: group dark matter halo mass M h, central/satellite designation, relative mass density of the cosmic web, and distance to the nearest massive group. We find that at fixed M *, satellites have decreasing G/S with increasing M h starting clearly at M h ∼ 1012 , suggesting the presence of starvation and/or stripping mechanisms associated with halo gas heating in intermediate-mass groups. The analogous relationship for centrals is uncertain because halo abundance matching builds in relationships between central G/S, stellar mass, and halo mass, which depend on the integrated group property used as a proxy for halo mass (stellar or baryonic mass). On larger scales G/S trends are less sensitive to the abundance matching method. At fixed M h ≤ 1012 , the fraction of gas-poor centrals increases with large-scale structure density. In overdense regions, we identify a rare population of gas-poor centrals in low-mass (M h < 1011.4 ) halos primarily located within ∼1.5× the virial radius of more massive (M h > 1012 ) halos, suggesting that gas stripping and/or starvation may be induced by interactions with larger halos or the surrounding cosmic web. We find that the detailed relationship between G/S and environment varies when we examine different subvolumes of RESOLVE independently, which we suggest may be a signature of assembly bias.

Dependence of galaxy quenching on halo mass and distance from its centre

We study the dependence of star-formation quenching on galaxy mass and environment, in the SDSS (z~0.1) and the AEGIS (z~1). It is crucial that we define quenching by low star-formation rate rather than by red colour, given that one third of the red galaxies are star forming. We address stellar mass M*, halo mass Mh, density over the nearest N neighbours deltaN, and distance to the halo centre D. The fraction of quenched galaxies appears more strongly correlated with Mh at fixed M* than with M* at fixed Mh, while for satellites quenching also depends on D. We present the M*-Mh relation for centrals at z~1. At z~1, the dependence of quenching on M* at fixed Mh is somewhat more pronounced than at z~0, but the quenched fraction is low (10%) and the haloes are less massive. For satellites, M*-dependent quenching is noticeable at high D, suggesting a quenching dependence on sub-halo mass for recently captured satellites. At small D, where satellites likely fell in more than a few Gyr ago, quenching strongly depends on Mh, and not on M*. The Mh-dependence of quenching is consistent with theoretical wisdom where virial shock heating in massive haloes shuts down accretion and triggers ram-pressure stripping, causing quenching. The interpretation of deltaN is complicated by the fact that it depends on the number of observed group members compared to N, motivating the use of D as a better measure of local environment.

ENVIRONMENTAL DEPENDENCE OF THE GALAXY MERGER RATE IN A ΛCDM UNIVERSE

We make use of four galaxy catalogs based on four different semi-analytical models (SAMs) implemented in the Millennium simulation to study the environmental effects and the model dependence of galaxy merger rate. We begin the analyses by finding that galaxy merger rate in the SAMs has mild redshift evolution, consistent with results of previous works. To study the environmental dependence of galaxy merger rate, we adopt two estimators, the local overdensity (1+{\delta}n) defined as the surface density from the nth-nearest-neighbor (n = 6 is chosen in this study) and the host halo mass Mh. We find that galaxy merger rate Fmg shows strong dependence on the local overdensity (1+{\delta}n) and the dependence is similar at all redshifts. For the overdensity estimator, the merger rate Fmg is found about twenty times larger in the densest regions than in under-dense ones in two of the four models while it is roughly four times higher in the other two. In other words, the discrepancies of the merger rate difference between two extremes can differ by a factor of ~ five depending on the SAMs adopted. On the other hand for the halo mass estimator, Fmg does not monotonically increase with the host halo mass Mh, but peaks in the $M_h$ range between 10^12 and 10^13 h-1 M{\Theta}, which corresponds to group environments. High merger rate in high local density regions corresponds primarily to the high merge rate in group environments......

Are strong z ≃ 0.5 MgII absorbers the signature of super-winds?

AbstractBACKGROUND: In the process of galaxy formation, super-nova driven feedback from low-mass galaxies is the process that most readily account for the galaxy mass-metallicity relation and for the shallower galaxy luminosity function (LF) compared to the halo mass function. Absorption-selected galaxies are prime candidates for the sites of starburst activity as (1) they probe the gaseous halos of galaxies up to ~50 kpc (Steidel 1995), and (2) galaxies on the faint end of the LF are likely dominating the statistics. Galaxies selected via their MgII λ2796/2803 doublet absorption against background QSOs are especially well suited as Mg is produced by type II supernova.GOAL: Our project was to constrain the physical models of the gaseous halos by measuring the dark matter halo-mass (Mh) of the MgII host-galaxies statistically, i.e. without identifying spectroscopically the host-galaxy.METHOD: We have used the cross-correlation w(rθ) (over co-moving scales rθ:0.05–13h−1Mpc) between our sample of 1800 z ≃ 0.5 MgII absorbers with equivalent w width W2796r−0.3 Å, and 250,000 Luminous Red Galaxies (LRGs), both selected from SDSS/DR3. The cross-correlation relies on the LRG photometric redshifts, but is not affected from contaminants such as stars or foreground and background galaxies as shown theoretically in Bouché et al. 2005 and empirically in Bouché et al. 2006.RESULTS: From the cross-correlation analysis, we found (Bouché et al. 2006) (i) that the absorber host-halo mean mass is 〈 log Mh (M⊙)〉 = 11.94 ±0.31(stat)+0.24−0.25(sys), i.e. about 1/2 L*, and (ii) an anti-correlation between halo mass Mh and equivalent width W2796r.INTERPRETATION: One SDSS MgII absorber (system) is made of several sub-components or clouds and the stronger the equivalent with of the absorber, the more clouds per system spread over a larger velocity range (Δv). This follows since each sub-component has a velocity width of ~ 5 kms s−1 (Churchill 1997). As result, the equivalent width W2796r is a measure of velocity width (Δv) as demonstrated by Ellison 2006. Together with our SDSS results, these relations imply a mass–velocity Mh–Δv anti-correlation. If the clouds in the host-halos were virialized, velocity and mass would have been correlated.CONCLUSION: Therefore, our Mh–Δv anti-correlation shows that the clouds are not virialized in the gaseous halos of the hosts. This conclusion is best understood in the context of starburst driven outflows where the velocity Δv is related to bulk motion. This opens the possibility to study M82-analogs up to z ~ 2.0 using the MgII selection.

Density profiles of dark matter haloes: diversity and dependence on environment

We study the outer density profiles of dark matter haloes predicted by a generalized secondary infall model and observed in a dissipationless cosmological simulation of a low-density flat cold dark matter model with the cosmological constant. We find substantial systematic variations in shapes and concentrations of the halo profiles as well as a strong correlation of the profiles with the environment in which the haloes are embedded. In the N-body simulation, the average outer slope of the density profiles, β(ρ∝r-β), of isolated haloes is β≈2.9, and 68 per cent of these haloes have values of β between 2.5 and 3.8. Haloes in dense environments of clusters are more concentrated and exhibit a broad distribution of β with an average value higher than the average β for isolated haloes. For haloes located within half the virial radius of the cluster from the centre values β≈4 are very common. Contrary to what one may expect, the haloes contained within groups and galaxy systems are less concentrated and have flatter outer density profiles than the isolated haloes: the distribution of β peaks at ≈2.3–2.7. The slope β weakly anticorrelates with the halo mass Mh. The concentration decreases with Mh, but its scatter is roughly equal to the whole variation of this parameter in the galaxy halo mass range. The mass and circular velocity of the haloes are strongly correlated, , with α≈3.3 and ≈3.5 for the isolated haloes and haloes in clusters, respectively. For Mh≈1012 h-1 M⊙ the rms deviations from these relations are Δ log Mh=0.12 and 0.18, respectively. Approximately 30 per cent of the haloes are contained within larger haloes or have massive companions within three virial radii. The companions are allowed to have masses larger than ∼0.3 times the mass of the current halo. The remaining 70 per cent of the haloes are isolated objects. We find that the distribution of β as well as the concentration–mass and Mh–Vm relations for the isolated haloes agree very well with the predictions of our seminumerical approach, which is based on a generalization of the secondary infall model and on the extended Press–Schechter formalism.