The Effect of Environment on Milky Way-mass galaxies in a Constrained Simulation of the Local Group

1.1 MB·English

by  Peter Creasey

Draft version January 14, 2015
PreprinttypesetusingLATEXstyleemulateapjv.08/13/06
THE EFFECT OF ENVIRONMENT ON MILKY WAY-MASS GALAXIES IN A CONSTRAINED SIMULATION
OF THE LOCAL GROUP
Peter Creasey1, Cecilia Scannapieco1, Sebastia´n E. Nuza1, Gustavo Yepes2, Stefan Gottlo¨ber1, and Matthias
Steinmetz1
Draft version January 14, 2015
ABSTRACT
In this letter we present, for the first time, a study of star formation rate, gas fraction and galaxy
5 morphology of a constrained simulation of the Milky Way (MW) and Andromeda (M31) galaxies,
1 compared to other MW-mass galaxies. By combining with unconstrained simulations we cover a
0 sufficient volume to compare these galaxies environmental densities ranging from the field to that of
2 the Local Group (LG). This is particularly relevant as it has been shown that, quite generally, galaxy
propertiesdependintimatelyupontheirenvironment, mostprominentlywhengalaxiesinclusters are
n
compared to those in the field. For galaxies in loose groups such as the LG, however, environmental
a
J effects have been less clear. We consider the galaxy’s environmental density in spheres of 1200 kpc
(comoving) and find that whilst environment does not appear to directly affect morphology, there is
3
a positive trend with star formation rates. This enhancement in star formation occurs systematically
1
forgalaxiesinhigherdensityenvironments,regardlesswhethertheyarepartoftheLGorinfilaments.

] OursimulationssuggestthatthericherenvironmentatMpc-scalesmayhelpreplenishthestar-forming
A gas, allowing higher specific star formation rates in galaxies such as the MW.
G Subject headings: galaxies: formation - galaxies: evolution - cosmology: theory - methods: numerical
.
h
p 1. INTRODUCTION Toomre & Toomre 1972), and could be responsible for
- at least some of the observed trends of galaxy properties
o During the last decades, observational studies found
with environment.
r indications that the environment where galaxies form
t Our MW lives in a rich group environment, known as
s plays an important role on the determination of their fi-
a nal properties. For example, elliptical galaxies are more the “Local Group” (LG). Andromeda (M31), the other
[ large spiral in the LG, has a similar mass to the MW,
strongly clustered than spirals (e.g. Dressler 1980; Her-

1 mit et al. 1996; Guzzo et al. 1997); and correlations be- andliesatlessthanaMpcaway. Suchspiralgalaxiesare
prevalent in the Universe, and thus a fundamental test
v tween environment and the photometric colour or lumi-
oftheΛCDMcosmologicalframeworkisthatneitherthe
3 nosityofagalaxyhavealsobeenmeasured(Blantonetal.
local universe (e.g. Nuza et al. 2014a) nor the MW and
8 2003). The suppression of star formation in clustered
M31 should be extremely improbable objects.
0 environments also extends to groups (Lewis et al. 2002;
3 Coendaetal.2014)andthemorphologytrends,i.e. that The numerical simulation of MW-like galaxies is an
0 early type galaxies lie closer to halo centres, extend as active area of research, with zoom-in techniques (Katz
1. a continuum to group scales (Girardi et al. 2003), al- & White 1993) allowing the collisionless and collisional
components of cosmological density fluctuations to be
0 though at stellar masses closer to that of the MW this
followed over almost the full 13.7 billion years of cos-
5 is more controversial (Ziparo et al. 2013) and some au-
mic time. Modern computers enable simulations that
1 thors suggest large scale features such as filaments may
describe the internal properties of galaxies so that time
: be more important than the group (e.g. Bah´e et al.
v variations due to mergers, interactions and infall can in-
2013). Group galaxies also appear deficient in cold gas
i deed be quantified using an acceptable number of reso-
X (Hess&Wilcots2013),althoughMcGeeetal.(2008)find
lution elements.
r that whilst the disc fraction depends on the group envi-
a ronment, theotherpropertiesofthediscsappearlargely Thepreciseinitialconditions(ICs)toproducelatetype
galaxiessuchastheMWandM31arenotbelievedtobe
unaffected.
strict as spiral galaxies are the most abundant type in
Ontheotherhand,theoreticalstudiesinthecontextof
our Universe. In most modern studies (e.g. Scanna-
Λ-ColdDarkMatter(ΛCDM)showthatthemergerrate
pieco et al. 2009; Guedes et al. 2011; Aumer et al. 2013;
of galaxies depends on environment, such that galaxies
Stinson et al. 2013; Vogelsberger et al. 2014) the ICs are
in intermediate and high-density regions have the high-
chosenashalosofMWmassandisolatedfromothermas-
est fractions of mergers (e.g. Maulbetsch et al. 2007; de
sivehalosthatcandestroydiscsatlatetimes. Indeedthe
Ravel et al. 2009; Darg et al. 2010; Ellison et al. 2010;
primary uncertainty of such simulations lies in the unre-
Fakhouri et al. 2010; Lin et al. 2010; Tonnesen & Cen
solvedbaryonicphysicsthatresultinstarformationand
2012; Jian et al. 2012). Mergers are indeed known to
feedback(seeCreaseyetal.2011),anddifferentcodesap-
induce morphological transformations of galaxies (e.g.
plied to the same halo can produce substantial variation
1Leibniz-Institutfu¨rAstrophysikPotsdam(AIP),AnderStern- in the stellar component (Scannapieco et al. 2012).
warte16,D-14482,Potsdam,Germany Whilst the interaction of the M31-MW pair is not yet
2Grupo de Astrof´ısica, Universidad Aut´onoma de Madrid, expected to affect internal galaxy properties as they are
MadridE-28049,Spain still too distant, their environments on Mpc scales have
2
merged, and this overdense environment may affect the The ICs use the zoom-in technique, where particles
pair. One method to test such effects is to identify anal- are placed in a periodic box of 91Mpc on a side and our
ogous pairs produced by cosmological ICs, and compare high-resolution region is of 10 Mpc radius at z =0, with
to more isolated systems. Following this approach, Few amassresolutionof2.8×106M and5.6×105M indark
(cid:12) (cid:12)
et al. (2012) found that for simulated MW-mass galax- matterandgasparticlesrespectively,andagravitational
ies the difference between the field and loose groups ap- softening length of 0.7kpc, fixed in physical coordinates
pearsmarginal,andinfacttheydetectednovisiblediffer- since z = 3 and fixed in comoving coordinates at earlier
encebetweenMW-likefieldgalaxiesandthosethatreside times. The IC phases are the same as for Nuza et al.
in loose groups. Garrison-Kimmel et al. (2014) find no (2014b), but the zoom region is slightly larger, causing
difference in concentrations or stellar masses within the some variation in the simulated evolution.
virial radius, but do find an increased number of ‘back- TheAquariussimulationsthatweusetocomparewith
splash’ galaxies (see e.g. Knebe et al. 2011) - those that our LG galaxies are the eight galaxies first presented
haveescapedthevirialradius-forpairssuchastheMW in S09. These are the hydrodynamical counterparts of
and M31. the galaxies of the Aquarius Project, selected to have
Althoughthosesimulationsallowassessmentoftheef- formed in isolated environments by requiring that they
fectsofenvironmentontheformationofMW-massgalax- have no neighbour exceeding half their mass within a
ies, they do not fully exploit the detailed constraints we sphere of 1.4Mpc at z = 0. The cosmological parame-
have from the present-day dynamics of our local uni- ters are slightly different to those used in our LG simu-
verse. One method to ameliorate this is to utilise the lation: Ω = 0.25, Ω = 0.75, Ω = 0.04, h = 0.73,
M Λ bar
power of constrained ICs that reproduce the observed andσ =0.9. Themassresolutionandsofteninglengths
8
dynamical properties of the LG in combination with hy- adopted are however similar in the two samples, and we
drodynamicalsimulations,whichhasnotpreviouslybeen have used the same set of input parameters for star for-
attempted. Thisprovidesapertinenttesttoquantifythe mationandfeedback. Thedifferentcosmologicalparam-
influence of environment, as well as allowing us to dis- etersusedarenotexpectedtocompromiseourresultsas
cern directly the physical processes in play during the theadjustmenttothecosmologyisratherminorincom-
formation of galaxies in a LG-like environment. parison with the dispersion in the evolutionary trends.
Inthisletter,wepresentresultsfromasimulationcon-
strained both to form a LG analogue and to match the 2.2. Simulation code
velocityfieldofthelocaluniverse. Thisallowsustocon- WeuseanextendedversionoftheTree-PMSmoothed
trast the properties of the simulated LG galaxies with ParticleHydrodynamics(SPH)codegadget3(Springel
other galaxies of similar stellar mass. For our LG sim- etal.2008)thatincludesmetal-dependentcooling,chem-
ulation we have taken (a version with slightly greater icalenrichmentandfeedbackfromTypeIIandIasuper-
coverage of) the ICs used to produce a MW-M31 pair novae (SNe), a multiphase gas model and a UV back-
in Nuza et al. (2014b) and Scannapieco et al. (submit- ground field (Haardt & Madau 1996). The model has
ted) in a volume resembling the distribution of matter been developed in Scannapieco et al. (2005, 2006) and is
of our local Universe. To enlarge and contrast our sam- the same code as for Nuza et al. (2014b).
pleweincludethe8galaxiesofScannapiecoetal.(2009, Inpreviouswork,wehaveshownthatourmodelisable
S09 hereafter) which use the same code. The latter sim- to reproduce the formation of galaxy discs from cosmo-
ulations are themselves resimulations of the 8 halos of logicalICs(Scannapiecoetal.2008,2009)andalleviates
theAquariusProject(Springeletal.2008)thatresultin the angular momentum problem. Some limitations ex-
isolated galaxies at z =0. ist, such as simulated galaxies tend to have overly mas-
This letter is organised as follows. In Section 2 we sive bulges (though see the implementation of Aumer
describe the simulation code that was used to evolve the et al. 2013 where the bulge mass is significantly reduced
ICsofboththeLGandAquarius,andthesampleofMW- via early stellar feedback), however discs do have real-
analogues that are produced. In Section 3 we analyse istic sizes and angular momentum content (Scannapieco
the evolution of the environment of these galaxies and et al. 2008, 2009, 2010, 2012), allowing studies of their
attempt to discern its effect on basic galaxy quantities formationandevolutioninrelationtothosestructureson
such as stellar mass, gas mass and star formation rate. larger scales. In a companion paper (Scannapieco et al.,
In Section 4 we discuss and conclude. submitted) we analyse the evolution of the distribution
ofthestellarcomponent,towhichwereferthereaderfor
2. SIMULATIONS
details of morphology classification.
2.1. Initial conditions
The ICs used for our LG simulations are part of 2.3. The Galaxy Sample
the CLUES (Constrained Local UniversE Simulations3) We choose a sample of galaxies with stellar masses in
Project. The ICs reproduce, by construction, the known the range 1010.5−11.5M , i.e. similar to the MW. For
(cid:12)
dynamical properties of our local environment at z = 0 our LG simulation this includes the M31 and MW can-
(Gottl¨ober et al. 2010; Yepes et al. 2014), and are con- didates4 G1 and G2 along with four other galaxies that
sistent with a ΛCDM universe with WMAP-5 parame- werefertoasG3-G6. Thesegalaxieshaveno‘contamina-
ters: ΩM = 0.279 (matter density), ΩΛ = 0.721 (dark tion’within1200comovingkpc(ckpc)fromtheircentres,
energy density), Ωbar = 0.046 (baryon density), H0 = i.e. they are sufficiently embedded inthe zoom region to
100hkms−1Mpc−1 with h = 0.7 (Hubble parameter), avoid low-resolution particles. The environment of these
and σ =0.8 (normalization of the power spectrum).
8
4 Note that in Nuza et al. (2014b) these galaxies were referred
3 http://www.clues-project.org/ toasM31c andMWc respectively.
3
ImagesofthesegalaxiescanbeseeninS09andforprevi-
ousstudiesoftheirformationhistoriesandpropertieswe
referthereadertoScannapiecoetal.(2009,2010,2011).
Table 1 summarises the main properties of the LG and
Aquarius galaxies at z = 0 inside their respective virial
radii R , where the density is 200 times the critical
200
density ρ at the corresponding redshift.
c
TheLGgalaxieshavestellarcomponentsthatallshow
some measure of rotational support, however when we
examine the components of angular momenta (e.g. as
in S09) we see that only half, G2, G3 and G4, have
a significant fraction (> 17%) of the stellar mass in
a rotationally-supported disk. Nevertheless, all these
galaxies exhibit extended gas discs and star formation
at redshift zero. In the case of the Aquarius simulations
eachgalaxywasabletogrowextendeddiscsduringtheir
evolution,butagainonlyhalfcansurviveuntilz =0,Aq-
C,Aq-D,Aq-EandAq-G.Inbothcaseswefindthesur-
vivalordestructionofdiscsintheS09samplewasfound
to depend primarily on the occurrence of major mergers
and the alignment between the angular momenta of the
stars and gas in the inner regions (see also Scannapieco
et al., submitted).
Fig. 1.—Columndensityofgas(blue)overlaidwithstarforming
gas(orange-white)forthezoomregionatz=0. Redcirclesdelimit 3. ENVIRONMENTAL EFFECTS
theR200 foreachgalaxyofasimilarstellarmasstotheMW(G1-
G6),andthelabelledinsetsenlargetheseregions. 1200kpcisthe The constrained nature of our simulation allows us to
radiusofourenvironmentmeasure,andthewidthoftheimageis explore the possibility that environment plays a role in
20Mpc.
the determination of the properties of galaxies like our
MW.Inthissection,weinvestigatethisbycomparingthe
propertiesoftheLGandAquariusgalaxies. Wecompare
TABLE 1 properties that are expected to depend on environment
Main properties of the LG and Aquarius galaxies at z=0: (gas mass, stellar mass, star formation rate), to a mea-
virial radius (R200), virial mass (M200), and masses in sure of the environment. We note that the number of
stars, gas and star-forming gas (Mstar, Mgas and MSF), galaxies in our samples is too small to determine quan-
within the virial radius.
titative trends, but that systematic differences may still
be visible within the sample.
R200 M200 Mstar Mgas MSF For our environmental measure we use the ratio of the
[kpc] [1010M(cid:12)] [1010M(cid:12)] [1010M(cid:12)] [1010M(cid:12)] mean density of matter within 1200 ckpc to the mean
G1 245 168 8.1 6.6 0.479 density of matter of the universe, i.e.
G2 219 120 6.4 5.2 0.369
(cid:104)ρ (cid:105)
G3 211 108 6.8 3.6 0.078 δ ≡ M r<1200ckpc , (1)
G4 166 52 3.3 1.8 0.146 1200 Ω (z)ρ (z)
M c
G5 177 63 4.4 1.8 0.151
To give some physical reference, this radius corresponds
G6 174 60 3.7 1.5 0.090
to how far a baryon travelling at 100kms−1 traverses in
Aq-A 232 149 9.2 4.9 0.153
12Gyr(ignoringcosmologicalexpansion),approximately
Aq-B 181 71 4.0 1.7 0.033
identifyingthecosmologicalneighbourhoodwhichcanaf-
Aq-C 237 161 11.0 3.8 0.119
fect a MW-mass halo. This scale was also used as proxy
Aq-D 233 149 8.4 3.5 0.005
for the ‘local volume’ by Garrison-Kimmel et al. (2014),
Aq-E 206 108 8.4 2.6 0.048
and in the case of the LG simulation is large enough to
Aq-F 196 91 7.7 1.8 0.012 includethehalosofbothG1andG2atthepresenttime,
Aq-G 180 68 4.5 1.6 0.061 butforallothergalaxiesformsdisjointvolumes. Wehave
Aq-H 182 74 6.5 0.6 0.011 considered scales from 600-1500ckpc and found this to
give the least stochastic results.
Fig. 2 compares the environments of our galaxies as
a function of redshift, giving us a measure of the en-
galaxiesingasandstar-forminggasisprojectedinFig.1,
vironmental ‘assembly’, although we would stress that
along with insets to enlarge the properties within the
at these large radii we are not seeing halo mergers but
virial radius. All the galaxies in the LG sample are well
rather a growth in the richness of the environment. Ap-
separated(>3Mpc),excepttheG1-G2pairat770kpc.5
parent is that although all the galaxies inhabit similar
The eight Aquarius galaxies (denoted AqA-H) inhabit
environments at z ∼ 2-3, the three galaxies G1, G2 and
disjointenvironmentsandwereresimulatedindividually.
G4 exhibit stronger evolution after z ≈ 2 and are the
5 A visualisation of a revolution of this structure and the envi- galaxies with the highest overdensity δ1200 at z =0, ap-
ronmentselectionsisavailablehere. proximately twice as overdense as the Aquarius galaxies
4
11.0
G1 Aq-A
) 10.8 G2 Aq-B
(cid:12)
M 10.6 G3 Aq-C
(gas 10.4 GG45 AAqq--DE
M 10.2 G6 Aq-F
10 10.0 Aq-G
log 9.8 Aq-H
9.6
) 9.5 log10Mstar(M(cid:12)) 1)− 0.0
(cid:12) r
M y
(F 9.0 M(cid:12)−0.5
S (
M 8.5 R 1.0
10 SF −
log 8.0 g10 −1.5
o
7.5 l 2.0
1)− 0.0 log10Mstar(M(cid:12)) 1)− −1.5 log10δ1200
yr yr −
Fig. 2.— Environmental overdensity δ1200 vs. redshift for the M(cid:12)−0.5 (G −2.0
galaxiesintheLGandAquariussamples. ( R
R 1.0 F 2.5
F − S −
S S
andtheremainingLGgalaxies. Additionallythesethree log10 −21..05 log10 −33..50
all inhabit gaseous filaments, the former two reside in − 10.6 10.8 11.0 − 0.8 1.0 1.2 1.4
thefilamentidentifiedbyNuzaetal.(2014b)andforthe log10Mstar(M ) log10δ1200
latter can be seen in the animated (online) version of (cid:12)
Fig. 1. Such structures have previously been implicated Fig. 3.—Comparisonbetweenthepropertiesofthegalaxysam-
as affecting SF in groups (Bah´e et al. 2013). Since these plesatz=0. Leftcolumn fromtoptobottomshowsthegasmass
three galaxies recur as outliers later we denote them the (Mgas), the star forming gas mass (MSF) and the star formation
rate(SFR),allasafunctionofstellarmass(Mstar). Rightcolumn
‘rich sample’ and by contrast the remaining 11 as the shows the SFR and the specific star formation rate (SSFR) with
‘poor sample’. We note that this evolution of δ1200 im- δ1200 respectively. Filled symbols indicate the galaxies that have
pliesimprintsduetoenvironmentontherichsamplewill stellardisc,diamonds arethoseintherichsampleandgrey-shaded
disappear at early epochs (z (cid:38)1), before they were out- regions, where present, indicate the significant linear regressions
with 1σ errors.
liers. ±
In the left hand column of Fig. 3 we compare the dis-
tribution of three fundamental properties of the galaxies
at z = 0: the gas mass (M ) and the star forming borne out by classification with environmental overden-
gas
gasmass(M )withinR ,andthestarformationrate sity (Fig. 3 RHS). The SFR vs. overdensity has signifi-
SF 200
(SFR) for material within 30kpc averaged over the last cantcorrelation,rejectingthenullhypothesisat3.8σ. To
500Myr. Thesequantitiesareallplottedasafunctionof accountforcomorbidityofδ withM ,weaddition-
1200 star
the present-day stellar masses (M ) and we addition- ally considered the specific star formation rate (SSFR,
star
ally mark the galaxies with stellar discs. for which we simply use SFR/M ) and M vs. δ
star star 1200
The cosmological trend of M to rise with M is (notshown). ThesignificanceoftheSSFRtrendislower
gas star
visible even within this restricted stellar mass sample, (2.6σ), though both are more significant than the cor-
and indeed the significance of the trend shown is 4.4σ. relation of δ -M (0.8σ), i.e. environment is a bet-
1200 star
ForM andSFRthetrendsareinsignificant,partlydue ter indicator of SFR than stellar mass. The correlation
SF
to the higher stochasticity of these quantities (note the between M and SFR is also poor as the virial mass
200
dynamic range of M and the SFR is much higher than closely traces M .
SF star
justforthegas)thatobscuresthetrendinsuchalimited HavingseenaneffectofenvironmentonSFRforMW-
sample, both in terms of small number and restricted mass galaxies at z = 0 it is interesting to consider
stellar mass range. More interestingly, perhaps, is that whether this exists for their progenitors at higher red-
two of the rich sample (G1 and G2) are the outliers in shifts. Our simulations also provide evidence here, al-
M , M and SFR, and if we only consider SFR then though we must be somewhat cautious as galaxies are
gas SF
the entire rich sample is extremal. This suggests the correlated with their progenitors. In Fig. 4 we plot the
possibility that the richer environments of these galaxies SSFR vs δ for our 14 galaxies at z = 2, 1 and 0.5.
1200
arecontributingtohigherstarformationratesthanthose At higher redshifts, the galaxies live in sparser environ-
found in the poor sample. There does not appear to be mentswithhigherSSFRs,andnoticeablytheδ -SSFR
1200
corresponding trends with the morphology (i.e. whether correlation fades towards earlier epochs.
the stellar component lies in a disc) as was also noted Comparing Figs. 2-4 we can see that from z (cid:46) 1 the
by Few et al. (2012), and indeed in Scannapieco et al. rich sample transitions to a denser environment with a
(submitted)wefindmorphologytobelargelydetermined modestdropinSSFRwhilstthepoorsamplehasamore
by the merger history. pronouncedfallinSSFRbutlessevolutioninδ . This
1200
These hints of an effect of the denser environment are suggests a possible explanation for the trends in Fig. 3:
5
4. CONCLUSIONS
z=2
In this letter we performed a hydrodynamical con-
0
strained simulation of the structures within 10 Mpc of
1 G1 the MW to search for Mpc-scale environmental effects
− G2
on galaxy properties. We compare the star formation
G3
2 rates, morphologies and gas fractions of 6 galaxies of
− G4
G5 MW-like stellar masses to 8 from unconstrained simula-
3
− G6 tions and find systematically higher star formation rates
1)− 0 z=1 log10δ1200 AqA itnhitshteregnadladxiidesntohtaetxltievnedintorimchoerrphenolvoigroiensm. ents, though
yr AqB Most notably the simulated MW and M31 candidates
(G 1 AqC are overabundant both in present-day SSFR and in en-
R − AqD
F AqE vironmental density, marking them as outliers compared
S 2
S − AqF to the remaining galaxies. These exceptional values dis-
10 AqG appear at earlier cosmological times, corresponding to
g 3
lo − AqH their environmental assembly. The third galaxy which
z=0.5 log10δ1200 displayed this trend inhabited the dense environment of
0 a filamentary structure.
Although the number of galaxies is small and larger
1
− samples are needed to confirm these trends, our results
suggest that galaxies of a given mass that live in richer
2
− environmentscouldmoreeasilyreplenishtheirgasreser-
3 voirs enabling higher star formation rates. This is con-
−
sistent with a picture where the morphologies of MW-
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 like galaxies are primarily set by their merger history,
log10δ1200 yet environment still plays a role in their star formation
histories. This demonstrates the need to understand in
Fig. 4.—AsforthelowerrightpanelofFig.3butforredshifts detail the effects of environment on galaxy properties if
z=2,1,0.5fromtoptobottom.
we are to understand the formation of our own galaxy.
thecoldgasisdrivenbytherichnessoftheenvironment,
i.e. theaccretionofdensestructuresallowsthestarform-
inggastoreplenishandhigherratesofstarformationto
continue to z = 0. In our simulations subhalos deposit
little of this due to their low gas content (Nuza et al.
ACKNOWLEDGMENTS
2014b), although they may trigger star-formation indi-
rectly. Intriguingly, our trends for SFRs and star form- The simulation was performed on the MareNostrum
ing gas masses are in opposition to that of clusters vs. cluster in Barcelona. CS and PC acknowledge sup-
thefield, wheresuppressionextendstogroupscales(e.g. portfromtheLeibnizGemeinschaftthroughgrantSAW-
McGee et al. 2008 though see also Ziparo et al. 2013). 2012-AIP-5 129. SEN acknowledges support from the
This may result from the density of those systems com- Deutsche Forschungsgemeinschaft under the grants MU
pared to our sample, and in the case of the LG galaxies 1020 16-1 and NU 332/2-1, and GY thanks MINECO
from the fact that the LG has a late assembly, and so (Spain) for supporting his research through different
environmental effects will be less pronounced compared projects: AYA2012-31101, FPA2012-34694 and Con-
to more evolved systems. solider Ingenio SyeC CSD2007-0050.
REFERENCES
Aumer, M., White, S. D. M., Naab, T., & Scannapieco, C. 2013, Girardi, M., Rigoni, E., Mardirossian, F., & Mezzetti, M. 2003,
MNRAS,434,3142 A&A,406,403
Bah´e,Y.M.,McCarthy,I.G.,Balogh,M.L.,&Font,A.S.2013, Gottl¨ober, S., Hoffman, Y., & Yepes, G. 2010, ArXiv e-prints,
MNRAS,430,3017 arXiv:1005.2687
Blanton,M.R.,Eisenstein,D.J.,Hogg,D.W.,etal.2003,BAAS, Guedes,J.,Callegari,S.,Madau,P.,&Mayer,L.2011,ApJ,742,
36,589 76
Coenda, V., Muriel, H., & Mart´ınez, H. J. 2014, ArXiv e-prints, Guzzo,L.,Strauss,M.A.,Fisher,K.B.,Giovanelli,R.,&Haynes,
arXiv:1410.7780 M.P.1997,ApJ,489,37
Creasey, P., Theuns, T., Bower, R. G., & Lacey, C. G. 2011, Haardt,F.,&Madau,P.1996,ApJ,461,20
MNRAS,415,3706 Hermit,S.,Santiago,B.X.,Lahav,O.,etal.1996,MNRAS,283,
Darg,D.W.,Kaviraj,S.,Lintott,C.J.,etal.2010,MNRAS,401, 709
1043 Hess,K.M.,&Wilcots,E.M.2013,AJ,146,124
deRavel,L.,LeF`evre,O.,Tresse,L.,etal.2009,A&A,498,379 Jian,H.-Y.,Lin,L.,&Chiueh,T.2012,ApJ,754,26
Dressler,A.1980,ApJ,236,351 Katz,N.,&White,S.D.M.1993,ApJ,412,455
Ellison,S.L.,Patton,D.R.,Simard,L.,etal.2010,MNRAS,407, Knebe,A.,Libeskind,N.I.,Knollmann,S.R.,etal.2011,MNRAS,
1514 412,529
Fakhouri,O.,Ma,C.-P.,&Boylan-Kolchin,M.2010,MNRAS,406, Lewis, I., Balogh, M., De Propris, R., et al. 2002, MNRAS, 334,
2267 673
Few,C.G.,Gibson,B.K.,Courty,S.,etal.2012,A&A,547,A63 Lin,L.,Cooper,M.C.,Jian,H.-Y.,etal.2010,ApJ,718,1158
Garrison-Kimmel, S., Boylan-Kolchin, M., Bullock, J. S., & Lee, Maulbetsch, C., Avila-Reese, V., Col´ın, P., et al. 2007, ApJ, 654,
K.2014,MNRAS,438,2578 53
6
McGee, S. L., Balogh, M. L., Henderson, R. D. E., et al. 2008, —.2011,MNRAS,417,154
MNRAS,387,1605 Scannapieco,C.,Wadepuhl,M.,Parry,O.H.,etal.2012,MNRAS,
Nuza,S.E.,Kitaura,F.-S.,Heß,S.,Libeskind,N.I.,&Mu¨ller,V. 423,1726
2014a,MNRAS,445,988 Springel,V.,Wang,J.,Vogelsberger,M.,etal.2008,MNRAS,391,
Nuza,S.E.,Parisi,F.,Scannapieco,C.,etal.2014b,MNRAS,441, 1685
2593 Stinson,G.S.,Bovy,J.,Rix,H.-W.,etal.2013,MNRAS,436,625
Scannapieco, C., Gadotti, D. A., Jonsson, P., & White, S. D. M. Tonnesen,S.,&Cen,R.2012,MNRAS,425,2313
2010,MNRAS,407,L41 Toomre,A.,&Toomre,J.1972,ApJ,178,623
Scannapieco, C., Tissera, P. B., White, S. D. M., & Springel, V. Vogelsberger,M.,Genel,S.,Springel,V.,etal.2014,MNRAS,444,
2005,MNRAS,364,552 1518
—.2006,MNRAS,371,1125 Yepes,G.,Gottlo¨ber,S.,&Hoffman,Y.2014,NewARev.,58,1
—.2008,MNRAS,389,1137 Ziparo,F.,Popesso,P.,Biviano,A.,etal.2013,MNRAS,434,3089
Scannapieco, C., White, S. D. M., Springel, V., & Tissera, P. B.
2009,MNRAS,396,696(S09)