Aldo Rodríguez-Puebla

THE STELLAR-SUBHALO MASS RELATION OF SATELLITE GALAXIES

We extend the abundance matching technique (AMT) to infer the satellite-subhalo and central-halo mass relations (MRs) of local galaxies as well as the corresponding satellite conditional mass functions (CSMFs). We use as inputs the observed galaxy stellar mass function (GSMF) decomposed into centrals and satellites and the ΛCDM distinct halo and subhalo mass functions. We explore the effects of defining the subhalo mass, m sub, at the time of (sub)halo accretion (m acc sub) versus defining it at the time of observation (m obs sub); we also test the standard assumption that centrals and satellites follow the same MRs. We show that this assumption leads to predictions in disagreement with observations, especially when m obs sub is used. We find that when the satellite-subhalo MRs are constrained by the satellite GSMF, they are always different from the central-halo MR: The smaller the stellar mass, the less massive the subhalo of satellites as compared to the halo of centrals of the same stellar mass. This difference is more dramatic when m obs sub is used instead of m acc sub. On average, for stellar masses lower than ~2 × 1011 M ☉, the dark mass of satellites decreased by 60%-65% with respect to their masses at accretion time. We find that MRs for both definitions of subhalo mass yield CSMFs in agreement with observations. Also, when these MRs are used in a halo occupation model, the predicted two-point correlation functions at different stellar mass bins agree with observations. The average stellar-halo MR is close to the MR of central galaxies alone, and conceptually this average MR is equivalent to abundance matching the cumulative total GSMF to the halo + subhalo mass function (the standard AMT). We show that the use of m obs sub leads to less uncertain MRs than m acc sub and discuss some implications of the obtained satellite-subhalo MR. For example, we show that the tension between abundance and dynamics of Milky Way satellites in the ΛCDM cosmogony gives a value of ~ – 1.6 in the faint-end slope of the GSMF upturns.

The Stellar-to-halo Mass Relation of Local Galaxies Segregates by Color

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 11.3<logMh<15 range. 3) The fraction of halos 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 (likely through shock virial heating and AGN feedback), but group richness also plays an important role: central galaxies living in less dense environments quenched their star formation later or did not quench it yet. At low masses, processes that delay star formation without invoking too strong supernova-driven outflows could explain the high Ms/Mh ratios of blue centrals as compared to those of the scarce red centrals.

The Galaxy-Halo/Subhalo connection: Mass relations and implications for some satellite occupational distributions

We infer the local stellar-to-halo/subhalo mass relations (MRs) for central and satellite galaxies separately. Our statistical method is an extension of the abundance matching, halo occupation distribution, and conditional stellar mass function formalisms. We constrain the model using several combinations of observational data, consisting of the total galaxy stellar mass function (GSMF), its decomposition into centrals and satellites, and the projected two-point correlation functions (2PCFs) measured in different stellar mass (M *) bins. In addition, we use the ΛCDM halo and subhalo mass functions. The differences among the resulting MRs are within the model-fit uncertainties (which are very small, smaller than the intrinsic scatter between galaxy and halo mass), no matter what combination of data are used. This shows that matching abundances or occupational numbers is equivalent, and that the GSMFs and 2PCFs are tightly connected. We also constrain the values of the intrinsic scatter around the central-halo (CH) and satellite-subhalo (SS) MRs assuming them to be constant: σ c = 0.168 ± 0.051 dex and σ s = 0.172 ± 0.057 dex, respectively. The CH and SS MRs are actually different, in particular when we take the subhalo mass at the present-day epoch instead of at their accretion time. When using the MRs for studying the satellite population (e.g., in the Milky Way, MW), the SS MR should be chosen instead of the average one. Our model allows one to calculate several population statistics. We find that the central galaxy M * is not on average within the mass distribution of the most massive satellite, even for cluster-sized halos, i.e., centrals are not a mere realization of the high end of the satellite mass function; however for >3 × 1013 M ☉ halos, ~15% of centrals could be. We also find that the probabilities of MW-sized halos of having N Magellanic Cloud (MC) sized satellites agree well with observational measures; for a halo mass of 2 × 1012 M ☉, the probability to have two MCs is 5.4%, but if we exclude those systems with satellites larger than the MCs, then the probability decreases to <2.2%.

The Massive Satellite Population of Milky-Way-sized Galaxies

Several occupational distributions for satellite galaxies more massive than m * 4 × 107 M ☉ around Milky-Way (MW)-sized hosts are presented and used to predict the internal dynamics of these satellites as a function of m *. For the analysis, a large galaxy group mock catalog is constructed on the basis of (sub)halo-to-stellar mass relations fully constrained with currently available observations, namely the galaxy stellar mass function decomposed into centrals and satellites, and the two-point correlation functions at different masses. We find that 6.6% of MW-sized galaxies host two satellites in the mass range of the Small and Large Magellanic Clouds (SMC and LMC, respectively). The probabilities of the MW-sized galaxies having one satellite equal to or larger than the LMC, two satellites equal to or larger than the SMC, or three satellites equal to or larger than Sagittarius (Sgr) are 0.26, 0.14, and 0.14, respectively. The cumulative satellite mass function of the MW, Ns (≥m *) , down to the mass of the Fornax dwarf is within the 1σ distribution of all the MW-sized galaxies. We find that MW-sized hosts with three satellites more massive than Sgr (as the MW) are among the most common cases. However, the most and second most massive satellites in these systems are smaller than the LMC and SMC by roughly 0.7 and 0.8 dex, respectively. We conclude that the distribution Ns (≥m *) for MW-sized galaxies is quite broad, the particular case of the MW being of low frequency but not an outlier. The halo mass of MW-sized galaxies correlates only weakly with Ns (≥m *). Then, it is not possible to accurately determine the MW halo mass by means of its Ns (≥m *); from our catalog, we constrain a lower limit of 1.38 × 1012 M ☉ at the 1σ level. Our analysis strongly suggests that the abundance of massive subhalos should agree with the abundance of massive satellites in all MW-sized hosts, i.e., there is not a missing (massive) satellite problem for the ΛCDM cosmology. However, we confirm that the maximum circular velocity, v max, of the subhalos of satellites smaller than m * ~ 108 M ☉ is systematically larger than the v max inferred from current observational studies of the MW bright dwarf satellites; different from previous works, this conclusion is based on an analysis of the overall population of MW-sized galaxies. Some pieces of evidence suggest that the issue could refer only to satellite dwarfs but not to central dwarfs, then environmental processes associated with dwarfs inside host halos combined with supernova-driven core expansion should be on the basis of the lowering of v max.

SIMULATIONS OF ISOLATED DWARF GALAXIES FORMED IN DARK MATTER HALOS WITH DIFFERENT MASS ASSEMBLY HISTORIES

We present zoom-in N-body/hydrodynamics resimulations of dwarf galaxies formed in isolated cold dark matter (CDM) halos with the same virial mass (Mv ≈ 2.5 × 1010 M ☉) at redshift z = 0. Our goals are to (1) study the mass assembly histories (MAHs) of the halo, stellar, and gaseous components; and (2) explore the effects of the halo MAHs on the stellar/baryonic assembly of simulated dwarfs. Overall, the dwarfs are roughly consistent with observations. More specific results include: (1) the stellar-to-halo mass ratio remains roughly constant since z ~ 1, i.e., the stellar MAHs closely follow halo MAHs. (2) The evolution of the galaxy gas fractions, fg , are episodic, showing that the supernova-driven outflows play an important role in regulating fg —and hence, the star formation rate (SFR)—however, in most cases, a large fraction of the gas is ejected from the halo. (3) The star formation histories are episodic with changes in the SFRs, measured every 100 Myr, of factors of 2-10 on average. (4) Although the dwarfs formed in late assembled halos show more extended SF histories, their z = 0 specific SFRs are still below observations. (5) The inclusion of baryons most of the time reduces the virial mass by 10%-20% with respect to pure N-body simulations. Our results suggest that rather than increasing the strength of the supernova-driven outflows, processes that reduce the star formation efficiency could help to solve the potential issues faced by CDM-based simulations of dwarfs, such as low values of the specific SFR and high stellar masses.

Properties of dark matter haloes as a function of local environment density

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

The Global and Radial Stellar Mass Assembly of Milky Way-sized Galaxies

h^{-1}{\rm Mpc}

Kinematic scaling relations of CALIFA galaxies: A dynamical mass proxy for galaxies across the Hubble sequence

. We find that low mass halos (those less massive than the characteristic mass

Tidal stripping and post-merger relaxation of dark matter haloes: causes and consequences of mass-loss

M_{\rm C}

SDSS IV MaNGA - An archaeological view of the Cosmic Star Formation History

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 density regions at low redshifts