scholarly journals Merger types forming the Virgo cluster in recent gigayears

2018 ◽  
Vol 614 ◽  
pp. A102 ◽  
Author(s):  
M. Olchanski ◽  
J. G. Sorce
Keyword(s):  
Galaxy Evolution ◽  
Past History ◽  
Local Environment ◽  
Mass Range ◽  
Virgo Cluster ◽  
Formation History ◽  
History Of ◽  
Galaxy Populations ◽  
Near Future ◽  
Selection Of

Context. As our closest cluster-neighbor, the Virgo cluster of galaxies is intensely studied by observers to unravel the mysteries of galaxy evolution within clusters. At this stage, cosmological numerical simulations of the cluster are useful to efficiently test theories and calibrate models. However, it is not trivial to select the perfect simulacrum of the Virgo cluster to fairly compare in detail its observed and simulated galaxy populations that are affected by the type and history of the cluster. Aims. Determining precisely the properties of Virgo for a later selection of simulated clusters becomes essential. It is still not clear how to access some of these properties, such as the past history of the Virgo cluster from current observations. Therefore, directly producing effective simulacra of the Virgo cluster is inevitable. Methods. Efficient simulacra of the Virgo cluster can be obtained via simulations that resemble the local Universe down to the cluster scale. In such simulations, Virgo-like halos form in the proper local environment and permit assessing the most probable formation history of the cluster. Studies based on these simulations have already revealed that the Virgo cluster has had a quiet merging history over the last seven gigayears and that the cluster accretes matter along a preferential direction. Results. This paper reveals that in addition such Virgo halos have had on average only one merger larger than about a tenth of their mass at redshift zero within the last four gigayears. This second branch (by opposition to main branch) formed in a given sub-region and merged recently (within the last gigayear). These properties are not shared with a set of random halos within the same mass range. Conclusions. This study extends the validity of the scheme used to produce the Virgo simulacra down to the largest sub-halos of the Virgo cluster. It opens up great prospects for detailed comparisons with observations, including substructures and markers of past history, to be conducted with a large sample of high resolution “Virgos” and including baryons, in the near future.

scholarly journals The past history of galaxy clusters told by their present neighbours

2020 ◽  
Vol 496 (4) ◽  
pp. 5139-5148
Author(s):  
Jenny G Sorce ◽  
Stefan Gottlöber ◽  
Gustavo Yepes
Keyword(s):  
Galaxy Clusters ◽  
Past History ◽  
Virgo Cluster ◽  
Coma Cluster ◽  
The Past ◽  
Formation History ◽  
History Of ◽  
Observable Data ◽  
The Mean ◽  
Mass Assembly

ABSTRACT Galaxy clusters can play a key role in modern cosmology, provided their evolution is properly understood. However, observed clusters give us only a single timeframe of their dynamical state. Therefore, finding present observable data of clusters that are well correlated to their assembly history constitutes an inestimable tool for cosmology. Former studies correlating environmental descriptors of clusters to their formation history are dominated by halo mass–environment relations. This paper presents a mass-free correlation between the present neighbour distribution of cluster-size haloes and the latter mass assembly history. From the Big Multidark simulation, we extract two large samples of random haloes with masses ranging from Virgo to Coma cluster sizes. Additionally, to find the main environmental culprit for the formation history of the Virgo cluster, we compare the Virgo-size haloes to 200 Virgo-like haloes extracted from simulations that resemble the local Universe. The number of neighbours at different cluster-centric distances permits discriminating between clusters with different mass accretion histories. Similarly to Virgo-like haloes, clusters with numerous neighbours within a distance of about two times their virial radius experience a transition at z ≈ 1 between an active period of mass accretion, relative to the mean, and a quiet history. In contrary, clusters with few neighbours share an opposite trend: from passive to active assembly histories. Additionally, clusters with massive companions within about four times their virial radius tend to have recent active merging histories. Therefore, the radial distribution of cluster neighbours provides invaluable insights into the past history of these objects.

scholarly journals Dissecting the Formation Histories of Galaxies with Stellar Populations Models

2009 ◽  
Vol 5 (S262) ◽  
pp. 153-163
Author(s):  
Ivo Labbé
Keyword(s):  
Star Formation ◽  
Current Knowledge ◽  
High Redshift ◽  
Local Environment ◽  
Stellar Populations ◽  
Current Data ◽  
Star Formation History ◽  
Spectral Energy ◽  
Formation History ◽  
History Of

AbstractHow did galaxies evolve from primordial fluctuations to the well-ordered but diverse population of disk and elliptical galaxies that we observe today? Stellar populations synthesis models have become a crucial tool in addressing this question by helping us to interpret the spectral energy distributions of present-day galaxies and their high redshift progenitors in terms of fundamental characteristics such as stellar mass and age. I will review our current knowledge on the evolution of stellar populations in early- and late type galaxies at z < 1 and the tantalizing – but incomplete – view of the stellar populations in galaxies at 1 < z < 3, during the global peak of star formation. Despite great progress, many fundamental questions remain: what processes trigger episodes of galaxy-scale star formation and what quenches them? To what degree does the star formation history of galaxies depend on the merger history, (halo) mass, or local environment? I will discuss some of the challenges posed in interpreting current data and what improved results might be expected from new observational facilities in the near- and more distant future.

scholarly journals The star formation history of the Fornax dwarf spheroidal galaxy

2009 ◽  
Vol 5 (S262) ◽  
pp. 353-354
Author(s):  
Enrico V. Held ◽  
Eline Tolstoy ◽  
Luca Rizzi ◽  
Mary Cesetti ◽  
Andrew A. Cole ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Stellar Population ◽  
Main Sequence ◽  
Dwarf Galaxy ◽  
Star Formation History ◽  
Stellar Content ◽  
Formation History ◽  
First Results ◽  
History Of

AbstractWe present the first results of a comprehensive HST study of the star-formation history of Fornax dSph, based on WFPC2 imaging of 7 Fornax fields. Our observations reach the oldest main-sequence turnoffs, allowing us to address fundamental questions of dwarf galaxy evolution, such as the spatial variations in the stellar content, and whether the old stellar population is made up of stars formed in a very early burst or the result of a more continuous star formation.

scholarly journals CALIFA survey: The spatially resolved star formation history of massive galaxies

2012 ◽  
Vol 8 (S295) ◽  
pp. 300-303
Author(s):  
Rosa González Delgado ◽  
Enrique Pérez ◽  
Roberto Cid Fernandes ◽  
Rubén García-Benito ◽  
André de Amorim ◽  
...  
Keyword(s):  
Growth Rate ◽  
Star Formation ◽  
Galaxy Evolution ◽  
Local Density ◽  
Spectral Synthesis ◽  
Mass Density ◽  
Stellar Mass ◽  
Star Formation History ◽  
Formation History ◽  
History Of

AbstractThe Calar Alto Legacy Integral Field Area (CALIFA) project is an ongoing 3D spectroscopic survey of 600 nearby galaxies of all kinds. This pioneer survey is providing valuable clues on how galaxies form and evolve. Processed through spectral synthesis techniques, CALIFA datacubes allow us to, for the first time, spatially resolve the star formation history of galaxies spread across the color-magnitude diagram. The richness of this approach is already evident from the results obtained for the first ~ 1/6 of the sample. Here we show how the different galactic spatial sub-components (“bulge” and “disk”) grow their stellar mass over time. We explore the results stacking galaxies in mass bins, finding that, except at the lowest masses, galaxies grow inside-out, and that the growth rate depends on a galaxy's mass. The growth rate of inner and outer regions differ maximally at intermediate masses. We also find a good correlation between the age radial gradient and the stellar mass density, suggesting that the local density is a main driver of galaxy evolution.

scholarly journals The KMOS Galaxy Clusters Project

2014 ◽  
Vol 10 (S311) ◽  
pp. 110-115
Author(s):  
Roger L. Davies ◽  
A. Beifiori ◽  
R. Bender ◽  
M. Cappellari ◽  
J. Chan ◽  
...  
Keyword(s):  
Galaxy Clusters ◽  
Galaxy Evolution ◽  
Star Formation History ◽  
Cluster Galaxies ◽  
V Band ◽  
Spectral Bands ◽  
Formation History ◽  
The Status ◽  
History Of ◽  
Integral Field

AbstractKMOS is a cryogenic infrared spectrograph fed by twentyfour deployable integral field units that patrol a 7.2 arcminute diameter field of view at the Nasmyth focus of the ESO VLT. It is well suited to the study of galaxy clusters at 1 < z < 2 where the well understood features in the restframe V-band are shifted into the KMOS spectral bands. Coupled with HST imagining, KMOS offers a window on the critical epoch for galaxy evolution, 7-10 Gyrs ago, when the key properties of cluster galaxies were established. We aim to investigate the size, mass, morphology and star formation history of galaxies in the clusters. Here we describe the instrument, discuss the status of the observations and report some preliminary results.

scholarly journals Preservation of Biological Diversity of Domestic Animals in Hungary

2002 ◽  
pp. 18-29
Author(s):  
Imre Bodó
Keyword(s):  
Mating Systems ◽  
Biological Diversity ◽  
Domestic Animals ◽  
Domestic Animal ◽  
Ex Situ ◽  
The World ◽  
History Of ◽  
Near Future ◽  
Selection Of

Since the 1992 Rio de Janeiro UNO Congress domestic animals belong also officially to the genetic diversity of the world. Non commercial domestic animal breeds should be maintained for many cultural and technical reasons. Conservation and preservation of living beings is nowadays in the programme of many regional, national and international organizations.The preservation of domestic animals is possible in situ (at the original place and conditions) and ex situ (by cryogenic methods).There are three era in the history of preservation of domestic animals: the epoch of spontaneous maintenance, the period of sporadic national activities and the era of international programme.Some of the questions to be solved by scientific research: the principles of selection of the candidate populations for maintenance, the different degrees of endangeredness, the necessary population size to be subsidized, the problem of inbreeding, the best mating systems etc.In Hungary the maintenance of endangered domestic animal breeds is based upon the low.The following breeds are on the list of protected breeds:− the Hungarian Grey cattle,− the Lipizzan, Shagya, Nonius, Gidran, Furioso,Kisbér Halfbred, Murinsulaner and Hucul horses,− the Racka, Tsigai and Cikta sheep,− the Mangalitsa pig,− the Hungarian yellow, white, speckled and the Transsylvanian naked necked hen,− the Bronze Turkey,− the Frizzle Feathered goose.Hopefully in the near future the breeders of traditional domestic animal breeds will find the possible niches for their special products.

scholarly journals Star Cluster Encounters in the Magellanic Clouds

1999 ◽  
Vol 190 ◽  
pp. 443-444
Author(s):  
M.R. de Oliveria ◽  
H. Dottori ◽  
E. Bica
Keyword(s):  
Initial Conditions ◽  
Past History ◽  
Cluster Formation ◽  
Star Cluster ◽  
Magellanic Clouds ◽  
The Past ◽  
Sky Survey ◽  
History Of ◽  
Fundamental Insight ◽  
Selection Of

The study of star cluster pairs in the Magellanic Clouds (MCs) has been explored extensively in the past years (Bhatia & Hatzidimitriou 1988; Rodrigues et al. 1994; de Oliveira et al. 1998). The evolution of these pairs can provide fundamental insight into the past history of cluster formation in the MCs.We have selected MC clusters (Bica & Schmitt 1995; Bica et al. 1998) with morphologies resembling those of the present models. The images in this selection of pairs were obtained from the Digital Sky Survey (DSS). We have also performed N-body simulations of star cluster encounters under different initial conditions, with the total number of particles per simulation ranging from 1024 to 20480.

scholarly journals Pixel Lensing: The Key to the Universe

1996 ◽  
Vol 173 ◽  
pp. 365-370
Author(s):  
Andrew Gould
Keyword(s):  
Event Rate ◽  
Virgo Cluster ◽  
Star Formation History ◽  
Powerful Method ◽  
Suppression Factor ◽  
Photon Detection ◽  
Formation History ◽  
History Of ◽  
The Universe

Pixel lensing, the gravitational microlensing of unresolved stars, is potentially a powerful method for detecting and measuring microlensing events. Two groups are currently refining this method in observations toward M31. I show that the technique has wide application, from searching for intra-cluster Machos in the Virgo cluster, to improving the accuracy of follow-up observations of Galactic microlensing events, to measuring the star-formation history of the universe. I derive the equation for the pixel lensing event rate where Qmin is the minimum signal to noise for detection, τ is the optical depth, Nres is the number of telescope resolution elements in the field, is the photon detection rate from a fluctuation magnitude star, and ξ is a suppression factor.

scholarly journals Protist taxonomy: an ecological perspective

2004 ◽  
Vol 359 (1444) ◽  
pp. 599-610 ◽  
Author(s):  
Bland J. Finlay
Keyword(s):  
Sequence Similarity ◽  
Local Environment ◽  
Integrated Approach ◽  
Ecological Perspective ◽  
Ecological Niches ◽  
Freshwater Pond ◽  
Starting Point ◽  
The Status ◽  
History Of ◽  
Near Future

This is an exploration of contemporary protist taxonomy within an ecological perspective. As it currently stands, the ‘morphospecies’ does not accommodate the information that might support a truly ecological species concept for the protists. But the ‘morphospecies’ is merely a first step in erecting a taxonomy of the protists, and it is expected to become more meaningful in the light of genetic, physiological and ecological research in the near future. One possible way forward lies in the recognition that sexual and asexual protists may all be subject to forces of cohesion that result in (DNA) sequence–similarity clusters. A starting point would then be the detection of ‘ecotypes’—where genotypic and phenotypic clusters correspond; but for that we need better information regarding the extent of clonality in protists, and better characterization of ecological niches and their boundaries. There is some progress with respect to the latter. Using the example of a community of ciliated protozoa living in the stratified water column of a freshwater pond, it is shown to be possible to gauge the potential of protists to partition their local environment into ecological niches. Around 40 morphospecies can coexist in the superimposed water layers, which presumably represent different ecological niches, but we have yet to discover if these are discrete or continuously variable. It is a myth that taxonomic problems are more severe for protists than for animals and plants. Most of the fundamental problems associated with species concepts (e.g. asexuals, sibling species, phenotypic variation) are distributed across biota in general. The recent history of the status of Pfiesteria provides a model example of an integrated approach to solving what are essentially taxonomic problems.

Sign in / Sign up

Export Citation Format

Share Document