43 research outputs found
Lacerna in Vlachernä
No full textThe author attempts to map the stages through which the Latin appellative lacerna, ‘an open
cloak fastened at the shoulder’, passed to eventually serve as a toponym Βλαχέρναι. In the
bilingual times of the Eastern part of the Roman Empire, lacerna was not only known but
also adopted into Greek as λακέρνα / λαχέρνα. Having been used during the life span of two
generations to designate one of the main relics of the sacred precinct in the north-west of
Constantinople — the Ἐσθής, or, rather Ἐσθῆτα, the Robe of the Blessed Virgin, λαχέρνα
shed both its Latin origin and precise meaning in the memory lane of a Greek speaker; in a
situation of ever diminishing bilingualism, the word came to be used as some kind of a vague
proper name for the famous church with its relic. Very soon the word made a step further in
the same direction becoming an umbrella place-name for the whole sacred precinct. In the
process of adaptation, the beginning of the word underwent a phonetic change to become
Βλαχέρναι, with the emerging sound having virtually no palpable cause, be it even that certain
parallels for such can be provided. As the name of the district in the capital of Eastern Rome,
the word made its return into Latin in the form Vlachernae and due to the significance and
celebrity of the place came to enjoy worldwide renown
On the evolution of low-mass central galaxies in the vicinity of massive structures
No full textFil: Palma, Daniela. Universidad de Atacama. Instituto de Astronomía y Ciencias Planetarias de Atacama; Chile.Fil: Lacerna, Ivan. Universidad de Atacama. Instituto de Astronomía y Ciencias Planetarias de Atacama; Chile.Fil: Lacerna, Ivan. Millennium Institute of Astrophysics; Chile.Fil: Artale, Maria Celeste. Universidad Andres Bello. Facultad de Ciencias Exactas. Departamento de Ciencias Físicas. Instituto de Astrofísica; Chile.Fil: Montero Dorta, Antonio David. Universidad Técnica Federico Santa Maria. Departamento de Física; Chile.Fil: Ruiz, Andrés Nicolás. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Ruiz, Andrés Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Astronomía Teórica y Experimental; Argentina.Fil: Cora, Sofía Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Astrofísica de La Plata; Argentina.Fil: Cora, Sofía Alejandra. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina.Fil: Rodriguez, Facundo. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Rodriguez, Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Astronomía Teórica y Experimental; Argentina.Fil: Pallero, Diego. Universidad Técnica Federico Santa María. Departamento de Física; Chile.Fil: O’Mill, Ana. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: O’Mill, Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Astronomía Teórica y Experimental; Argentina.Fil: Choque-Challapa, Nelvy. Universidad de Atacama. Instituto de Astronomía y Ciencias Planetarias de Atacama; Chile.Fil: Choque-Challapa, Nelvy. Universidad Técnica Federico Santa Maria. Departamento de Física; Chile.We investigate low-mass central galaxies with Mstar = 109.5−1010 Msun/h, located near massive groups and galaxy clusters using the TNG300 and MDPL2-SAG simulations. We set out to study their evolution, aiming to find hints about the large-scale conformity signal they produce. We also use a control sample of low-mass central galaxies located far away from massive structures. For both samples, we find a sub-population of galaxies that were accreted by another halo in the past but are now considered central galaxies; we refer to these objects as former satellites. The fraction of former satellites is higher for quenched central galaxies near massive systems: 45% in TNG300 and 17% in MDPL2-SAG. Our results in TNG300 show that former satellites were typically hosted by massive dark matter halos (M200 ≥1013 Msun/h) at z∼0.3, followed by a drop in halo mass at lower redshifts. In addition, we find a strong drop in the total gas mass at z≤1 for quenched central galaxies near galaxy groups and clusters produced by these former satellites as well. By removing former satellites, the evolution of quenched central galaxies is fairly similar to those of the quenched control galaxies, showing small differences at low-z. For MDPL2-SAG, former satellites were hosted by less massive halos, with a mean halo mass around 1011 Msun/h, and the evolution remains equal before and after removing former satellites. We also measure the two-halo conformity, i.e., the correlation in the specific SFR between low-mass central galaxies and their neighbors at Mpc scales, and how former satellites contribute to the signal at z=0, 0.3, and 1. The conformity signal decreases from z=0 to z=1 in MDPL2-SAG but it increases in TNG300. However, after removing former satellites in TNG300, the signal is strongly reduced but almost does not change at z≤0.3, and it disappears at z=1 (abridged).info:eu-repo/semantics/acceptedVersionFil: Palma, Daniela. Universidad de Atacama. Instituto de Astronomía y Ciencias Planetarias de Atacama; Chile.Fil: Lacerna, Ivan. Universidad de Atacama. Instituto de Astronomía y Ciencias Planetarias de Atacama; Chile.Fil: Lacerna, Ivan. Millennium Institute of Astrophysics; Chile.Fil: Artale, Maria Celeste. Universidad Andres Bello. Facultad de Ciencias Exactas. Departamento de Ciencias Físicas. Instituto de Astrofísica; Chile.Fil: Montero Dorta, Antonio David. Universidad Técnica Federico Santa Maria. Departamento de Física; Chile.Fil: Ruiz, Andrés Nicolás. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Ruiz, Andrés Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Astronomía Teórica y Experimental; Argentina.Fil: Cora, Sofía Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Astrofísica de La Plata; Argentina.Fil: Cora, Sofía Alejandra. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina.Fil: Rodriguez, Facundo. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Rodriguez, Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Astronomía Teórica y Experimental; Argentina.Fil: Pallero, Diego. Universidad Técnica Federico Santa María. Departamento de Física; Chile.Fil: O’Mill, Ana. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: O’Mill, Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Astronomía Teórica y Experimental; Argentina.Fil: Choque-Challapa, Nelvy. Universidad de Atacama. Instituto de Astronomía y Ciencias Planetarias de Atacama; Chile.Fil: Choque-Challapa, Nelvy. Universidad Técnica Federico Santa Maria. Departamento de Física; Chile
The manifestation of secondary bias on the galaxy population from IllustrisTNG300
No full textWe use the improved IllustrisTNG300 magnetohydrodynamical cosmological simulation to revisit the effect that secondary halo bias has on the clustering of the central galaxy population. With a side length of 205 h−1 Mpc and significant improvements on the subgrid model with respect to previous Illustris simulations, IllustrisTNG300 allows us to explore the dependencies of galaxy clustering over a large cosmological volume and halo mass range. We show at high statistical significance that the halo assembly bias signal (i.e. the secondary dependence of halo bias on halo formation redshift) manifests itself on the clustering of the galaxy population when this is split by stellar mass, colour, specific star formation rate, and surface density. A significant signal is also found for galaxy size: at fixed halo mass, larger galaxies are more tightly clustered than smaller galaxies. This effect, in contrast to the rest of the dependencies, seems to be uncorrelated with halo formation time, with some small correlation only detected for halo spin. We also explore the transmission of the spin bias signal, i.e. the secondary dependence of halo bias on halo spin. Although galaxy spin retains little information about the total halo spin, the correlation is enough to produce a significant galaxy spin bias signal. We discuss possible ways to probe this effect with observations.Fil: Montero Dorta, Antonio D.. Universidade de Sao Paulo; BrasilFil: Artale, Maria Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Innsbruck; AustriaFil: Abramo, L. Raul. Universidade de Sao Paulo; BrasilFil: Tucci, Beatriz. Universidade de Sao Paulo; BrasilFil: Padilla, Nelson David. Pontificia Universidad Católica de Chile; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sato Polito, Gabriela. University Johns Hopkins; Estados UnidosFil: Lacerna, Ivan. Universidad de Atacama.; ChileFil: Rodriguez, Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Angulo, Raul E.. Donostia International Physics Center; Españ
The nature of assembly bias - I. Clues from a ΛCDM cosmology
No full textWe present a new proxy for the overdensity peak height for which the large-scale clustering of haloes of a given mass does not vary significantly with the assembly history. The peak height, usually taken to be well represented by the virial mass, can instead be approximated by the mass inside spheres of different radii, which in some cases can be larger than the virial radius and therefore include mass outside the individual host halo. The sphere radii are defined as where delta(t) is the age relative to the typical age of galaxies hosted by haloes with virial mass M-vir, M-nl is the non-linear mass, and a = 0.2 and b = -0.02 are the free parameters adjusted to trace the assembly bias effect. Note that r depends on both halo mass and age. In this new approach, some of the objects which were initially considered low-mass peaks (i.e. which had low virial masses) belong to regions with higher overdensities. At large scales, i.e. in the two-halo regime, this model properly recovers the simple prescription where the bias responds to the height of the mass peak alone, in contrast to the usual definition (virial mass) that shows a strong dependence on additional halo properties such as formation time. The dependence on the age in the one-halo term is also remarkably reduced with the new definition. The population of galaxies whose 'peak height' changes with this new definition consists mainly of old stellar populations and are preferentially hosted by low-mass haloes located near more massive objects. The latter is in agreement with recent results which indicate that old, low-mass haloes would suffer truncation of mass accretion by nearby larger haloes or simply due to the high density of their surroundings, thus showing an assembly bias effect. The change in mass is small enough that the Sheth et al. mass function is still a good fit to the resulting distribution of new masses
SDSS-IV MaNGA : signatures of halo assembly in kinematically misaligned galaxies
No full textFunding: RT acknowledges support from the Science and Technology Facilities Council via an Ernest Rutherford Fellowship (grant number ST/K004719/1). VW acknowledges support of the European Research Council via the award of a starting grant (SED-Morph; P.I. V. Wild).We investigate the relationship of kinematically misaligned galaxies with their large-scale environment, in the context of halo assembly bias. According to numerical simulations, halo age at fixed halo mass is intrinsically linked to the large-scale tidal environment created by the cosmic web. We investigate the relationship between distances to various cosmic web features and present-time gas accretion rate. We select a sub-sample of ∼900 central galaxies from the MaNGA survey with defined global position angles (PA; angle at which velocity change is greatest) for their stellar and Hα gas components up to a minimum of 1.5 effective radii (Re). We split the sample by misalignment between the gas and stars as defined by the difference in their PA. For each central galaxy we find its distance to nodes and filaments within the cosmic web, and estimate the host halo’s age using the central stellar mass to total halo mass ratio M*/Mh. We also construct halo occupation distributions using a background subtraction technique for galaxy groups split using the central galaxy’s kinematic misalignment. We find, at fixed halo mass, no statistical difference in these properties between our kinematically aligned and misaligned galaxies. We suggest that the lack of correlation could be indicative of cooling flows from the hot halo playing a far larger role than ‘cold mode’ accretion from the cosmic web or a demonstration that the spatial extent of current large-scale integral field unit (IFU) surveys hold little information about large-scale environment extractable through this method.Peer reviewe
The growth of galactic bulges through mergers in Lambda cold dark matter haloes revisited - II. Morphological mix evolution
No full textOn the environmental influence of groups and clusters of galaxies beyond the virial radius: Galactic conformity at few Mpc scales
No full textThe environment within dark matter haloes can quench the star formation of galaxies. However, environmental effects beyond the virial radius of haloes (≳1 Mpc) are less evident. An example is the debated correlation between colour or star formation in central galaxies and neighbour galaxies in adjacent haloes at large separations of several Mpc, referred to as two-halo galactic conformity. We use two galaxy catalogues generated from different versions of the semi-analytic model sag applied to the mdpl2 cosmological simulation and the IllustrisTNG300 cosmological hydrodynamical simulation to study the two-halo conformity by measuring the quenched fraction of neighbouring galaxies as a function of the real-space distance from central galaxies. We find that low-mass central galaxies in the vicinity of massive systems (M200c ≥ 1013 h-1 M⊙) out to 5 h-1 Mpc are preferentially quenched compared to other central galaxies at fixed stellar mass M∗ or fixed host halo mass M200c at z ∼0. In all the galaxy catalogues is consistent that the low-mass (M∗ < 1010 h-1 M⊙ or M200c < 1011.8 h-1 M⊙) central galaxies in the vicinity of clusters and, especially, groups of galaxies mostly produce the two-halo galactic conformity. On average, the quenched low-mass central galaxies are much closer to massive haloes than star-forming central galaxies of the same mass (by a factor of ∼5). Our results agree with other works regarding the environmental influence of massive haloes that can extend beyond the virial radius and affect nearby low-mass central galaxies.Fil: Lacerna, Ivan. Universidad de Atacama.; ChileFil: Rodriguez, Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Montero Dorta, Antonio D.. Universidad Técnica Federico Santa María; ChileFil: O'Mill, Ana Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Cora, Sofia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Artale, Maria Celeste. Universidad de Innsbruck; Austria. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Ruiz, Andrés Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Hough, Tomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Vega Martínez, Cristian Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina. Universidad de La Serena; Chil
New insights into the Triangulum Australis supercluster of galaxies
No full textThe Triangulum Australis cluster is one of about a dozen nearby massive cluster systems which contribute to the gravitational pull behind the so-called Great Attractor that is dominated by the nearby Shapley Supercluster mass, which conforms the galaxy velocity flows observed in that general direction. Here, we study the structure and dynamical mass of the Triangulum Australis cluster together with the neighbouring cluster AS0794. We present a set of 131 velocities collected in the regions of the two clusters with the 2.5 m Du Pont telescope at Las Campanas Observatory (Chile). For the Triangulum Australis cluster we find a dynamical mass of about Mv = 4.2 (±1.3) × 1015 M⊙ and for AS0794 a value of about Mv = 1.7 (±1.3) × 1013 M⊙. These values are consistent with the observed X-ray luminosities of these clusters. Combined with velocities already known we reanalyse the structure and dynamics of this general region, finding that both clusters, together with at least eight other ones, form a large supercluster, centered on TriAus (which dominates in terms of mass). We find that this supercluster is part of a large-scale structure filament linked to the Shapley supercluster (SSC). Uncertainties remain on the richness and detailed structure of this filament and the TriAus supercluster because parts of it remain hidden behind the Galaxy disk
Abell548: A rich cluster of galaxies in the making
No full textWe performed an in-depth study of the complex structure of the galaxy cluster A548, based on 108 spectroscopic galaxy velocities reported in this paper. This analysis includes 80 new redshifts, along with velocity data from the literature and a reanalysis of X-ray observations. We find that the cluster is in a merging phase of at least six components. These belong to two sheets, or clouds, of galaxies with a mean velocity difference of 1100–1300 km s−1. Each cloud has broken into three concentrations, with a relative separation between their centres of approximately ∼1° on the plane of the sky and velocity separations of nearly 1000 km s−1, all visible in the X-ray maps. The western component (CID36) is primarily composed of a single, small concentration, the middle component (A548W) has two principal substructures, with the largest being in an advanced merging state, involving two secondary components centred on a dominant dumbbell galaxy. The far-eastern component (A548E) is the merger of two corresponding substructures. There is a further extension to the NE, which is not observed in X-rays. This extension is divided into two sub-clumps with velocities corresponding to those in the clouds and located in front of A3367. Consequently, the two clouds have a large coherence length along the plane of the sky. The entire region can be considered as the ongoing phases of a rich cluster formation, which will have a central dumbbell as its central galaxy
The spatial distribution of dwarf and giant galaxies in and around the Virgo cluster
No full textThe Virgo cluster is one of the closest clusters to us where we can further study the evolution of galaxies, with several infalling substructures and several filaments around it that have been reported. Therefore, it makes this cluster and its surrounding area an interesting place to study the spatial distribution of the population of dwarf and bright giant galaxies. We analysed the dwarf fraction (DF) in different regions of the cluster, inside the virial radius, in its surrounding area, and in the filamentary structure surrounding it using available catalogues with the aim of measuring whether the DF changes in different environments. Although the total dwarf fraction within the cluster is ∼0.8, significant local variations are measured throughout the cluster; there are regions with a relatively higher concentration of giant or dwarf galaxies. The fact that Virgo is embedded in a rich environment surrounded by several filaments that feed the cluster with new substructures could imply changes in the DF locally. When we analysed the DF variation at further distances from the cluster we observe some regions with few or no giant galaxies at all, with a local DF ranging from 0.8−1.0. Additionally, when comparing the dwarf fraction in different environments, overall the DF is larger in regions further away from denser regions such as the Virgo cluster and its filamentary structure surrounding it. When comparing the filament and the cluster area, the DF is slightly higher in the filaments, but from filament to filament, the DF changes depending on the presence of groups
