Thousands of milky ways: Galaxy satellites and building blocks

A semi-analytic model of galaxy formation with and without active galactic nuclei feedback is used to study the nature of possible building blocks (BBs) of z = 0 galaxies, including those of Milky-Way types. We find that BBs can show an important range of properties arising from environmental variables such as host halo mass, and whether a galaxy is a satellite within its host halo; the stellar formation histories are comparatively faster and the chemical enrichment is more efficient in BBs than in surviving satellites, in accordance with recent metallicity measurements for the Milky Way. These results can be used in combination with observational constraints to continue probing the ability of the cold dark-matter scenario to reproduce the history of galaxy demography in the Universe.Instituto de Astrofísica de La Plat

Cytogenetic Analysis of Primary Cultures and Cell Lines: Generalities, Applications and Protocols

"La citogenética constituye una importante herramienta diagnóstica para determinar y/o confirmar síndromes específicos en la actualidad; su uso se dirige a la selección de tratamientos y monitorización de pacientes mediante diferentes procedimientos. Estos últimos se realizan con el fin de obtener un cariotipo a partir de sangre periférica o varias biopsias de tejido (p.ej. biopsias de pacientes con melanoma, cáncer de mama, biopsias de piel, muestras de prepucio, productos de aborto, entre otros). Sin embargo, el estudio de las anomalías cromosómicas en las células de cultivo se ha visto limitado por procesos complejos como lograr el crecimiento celular y un buen número de metafases, que a su vez dificulta la posibilidad de obtener un número útil de propagación de la metafase con el fin de llevar a cabo un análisis citogenético adecuado, que debe ser capaz de mostrar una buena morfología una dispersión adecuada y una banda correcta. Las líneas celulares son ampliamente utilizadas en diferentes campos de investigación, particularmente en modelos invitro para la investigación del cáncer. (Burdall et al., 2003)""Cytogenetics constitutes an important diagnostic tool to determine and/or confirm specific syndromes nowadays; its use is directed towards the selection of treatments and monitoring of patients using different procedures. These latter are carried out in order to obtain a karyotype from peripheral blood or several tissue biopsies (e.g. biopsies from patients with melanoma, breast cancer, skin biopsies, foreskin samples, abortion products, among others). However, the study of chromosomal abnormalities in culture cells has been limited by complex processes such as achieving cell growth and a good number of metaphases, which in turn hampers the chance to obtain a useful number of metaphase spreads in order to carry out a proper cytogenetic analysis, that should be able to display a good morphology, an adequate dispersion and a correct banding. Cell lines are widely used in different research fields, particularly in invitro models for cancer research. (Burdall et al., 2003)

New insights in the cytogenetic practice: Karyotypic chaos, non-clonal chromosomal alterations and chromosomal instability in human cancer and therapy response

Recently, non-clonal chromosomal alterations previously unappreciated are being proposed to be included in cytogenetic practice. The aim of this inclusion is to obtain a greater understanding of chromosomal instability (CIN) and tumor heterogeneity and their role in cancer evolution and therapy response. Although several genetic assays have allowed the evaluation of the variation in a population of cancer cells, these assays do not provide information at the level of individual cells, therefore limiting the information of the genomic diversity within tumors (heterogeneity). The karyotype is one of the few available cytogenetic techniques that allow us not only to identify the chromosomal alterations present within a single cell, but also allows us to profile both clonal (CCA) and non-clonal chromosomal alterations (NCCAs). A greater understanding of CIN and tumor heterogeneity in cancer could not only improve existing therapeutic regimens but could also be used as targets for the design of new therapeutic approaches. In this review we indicate the importance and significance of karyotypic chaos, NCCAs and CIN in the prognosis of human cancers. © 2017 by the authors. Licensee MDPI, Basel, Switzerland

Plasticity in organic composition maintains biomechanical performance in shells of juvenile scallops exposed to altered temperature and pH conditions

This study was funded by PIA ANID ACT 172037 for international collaborative research among Chile (NAL, MAL, JV, CG-H, CD) and Spain (ARN, CG). Author also acknowledges support from Fondecyt 1190444 (MAL), Fondecyt 1210171 (CAV) and ANID - Millennium Science Initiative Program - ICN2019_015 (SECOS) (NAL, MAL and CAV). ANID doctoral scholarhip #21210012 to SB. ANID PFCHA / Doctorados Becas Chile Chile/2019-CEL00011051 to AA-O and DICYT from USACH to AA-O and CG-H during the execution of sample processing and analysis. We also acknowledge to Anita Quiroga, Jhonny Rojas for their support in lab procedures, and the staff at BIO-CT Lab (Universidad de Chile). We are grateful to B. Broitman and two anonymous reviewers who provided valuable comments on previous version of the manuscript.The exposure to environmental variations in pH and temperature has proven impacts on benthic ectotherms calcifiers, as evidenced by tradeoffs between physiological processes. However, how these stressors affect structure and functionality of mollusk shells has received less attention. Episodic events of upwelling of deep cold and low pH waters are well documented in eastern boundary systems and may be stressful to mollusks, impairing both physiological and biomechanical performance. These events are projected to become more intense, and extensive in time with ongoing global warming. In this study, we evaluate the independent and interactive effects of temperature and pH on the biomineral and biomechanical properties of Argopecten purpuratus scallop shells. Total organic matter in the shell mineral increased under reduced pH (~ 7.7) and control conditions (pH ~ 8.0). The periostracum layer coating the outer shell surface showed increased protein content under low pH conditions but decreasing sulfate and polysaccharides content. Reduced pH negatively impacts shell density and increases the disorder in the orientation of calcite crystals. At elevated temperatures (18 °C), shell microhardness increased. Other biomechanical properties were not affected by pH/ temperature treatments. Thus, under a reduction of 0.3 pH units and low temperature, the response of A. purpuratus was a tradeoff among organic compounds (biopolymer plasticity), density, and crystal organization (mineral plasticity) to maintain shell biomechanical performance, while increased temperature ameliorated the impacts on shell hardness. Biopolymer plasticity was associated with ecophysiological performance, indicating that, under the influence of natural fluctuations in pH and temperature, energetic constraints might be critical in modulating the long-term sustainability of this compensatory mechanism.PIA ANID ACT 172037Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 1190444 1210171ANID - Millennium Science Initiative Program ICN2019_015ANID doctoral scholarhip 21210012ANID PFCHA / Doctorados Becas Chile Chile/2019-CEL0001105

Effects of AGN feedback on ΛCDM galaxies

We study the effects of active galactic nuclei (AGN) feedback on the formation and evolution of galaxies by using a combination of a cosmological N-body simulation of the concordance Lambda cold dark matter (ΛCDM) paradigm and a semi-analytic model of galaxy formation. This model is an improved version of the one described by Cora (2006), which now considers the growth of black holes (BHs) as driven by (i) gas accretion during merger-driven starbursts and mergers with other BHs, (ii) accretion during starbursts triggered by disc instabilities and (iii) accretion of gas cooled from quasi-hydrostatic hot gas haloes. It is assumed that feedback from AGN operates in the last case. The model has been calibrated in order to reproduce observational correlations between BH mass and mass, velocity dispersion and absolute magnitudes of the galaxy bulge. AGN feedback has a strong impact on reducing or even suppressing gas cooling, an effect that becomes important at lower redshifts. This phenomenon helps to reproduce the observed galaxy luminosity function (LF) in the optical and near-infrared bands at z = 0, and the cosmic star formation rate and stellar mass functions over a wide redshift range (0 ≲ z ≲ 5). It also allows us to have a population of massive galaxies already in place at z ≳ 1, which are mostly early-type and have older and redder stellar populations than lower mass galaxies, reproducing the observed bimodality in the galaxy colour distribution, and the morphological fractions. The evolution of the optical QSO LF is also reproduced, provided that the presence of a significant fraction of obscured QSOs is assumed. We explore the effects of AGN feedback during starbursts finding that, in order to obtain a good agreement with observations, these need to be strong enough to expel the reheated gas away from the galaxy halo. We also test new, recent prescriptions for dynamical friction time-scales, and find that they produce an earlier formation of elliptical galaxies, and a larger amount of disc instabilities, which compensate the change in the merger frequency such that the properties of z = 0 galaxies remain almost unaffected.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Effects of AGN feedback on ΛCDM galaxies

We study the effects of active galactic nuclei (AGN) feedback on the formation and evolution of galaxies by using a combination of a cosmological N-body simulation of the concordance Lambda cold dark matter (ΛCDM) paradigm and a semi-analytic model of galaxy formation. This model is an improved version of the one described by Cora (2006), which now considers the growth of black holes (BHs) as driven by (i) gas accretion during merger-driven starbursts and mergers with other BHs, (ii) accretion during starbursts triggered by disc instabilities and (iii) accretion of gas cooled from quasi-hydrostatic hot gas haloes. It is assumed that feedback from AGN operates in the last case. The model has been calibrated in order to reproduce observational correlations between BH mass and mass, velocity dispersion and absolute magnitudes of the galaxy bulge. AGN feedback has a strong impact on reducing or even suppressing gas cooling, an effect that becomes important at lower redshifts. This phenomenon helps to reproduce the observed galaxy luminosity function (LF) in the optical and near-infrared bands at z = 0, and the cosmic star formation rate and stellar mass functions over a wide redshift range (0 ≲ z ≲ 5). It also allows us to have a population of massive galaxies already in place at z ≳ 1, which are mostly early-type and have older and redder stellar populations than lower mass galaxies, reproducing the observed bimodality in the galaxy colour distribution, and the morphological fractions. The evolution of the optical QSO LF is also reproduced, provided that the presence of a significant fraction of obscured QSOs is assumed. We explore the effects of AGN feedback during starbursts finding that, in order to obtain a good agreement with observations, these need to be strong enough to expel the reheated gas away from the galaxy halo. We also test new, recent prescriptions for dynamical friction time-scales, and find that they produce an earlier formation of elliptical galaxies, and a larger amount of disc instabilities, which compensate the change in the merger frequency such that the properties of z = 0 galaxies remain almost unaffected.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Cosmic queuing: Galaxy satellites, building blocks and the hierarchical clustering paradigm

We study the properties of building blocks (BBs; i.e. accreted satellites) and surviving satellites of present-day galaxies using the semi-analytic model of galaxy formation SAG ('semi-analytic galaxies') in the context of a concordance Λ cold dark matter (ΛCDM) cosmology. We consider large number of dark matter (DM) halo merger trees spanning a wide range of masses (~1 × 1010-2.14 × 1015 M⊙). We find higher metallicities for BBs with respect to surviving satellites, an effect produced by the same processes behind the build up of the mass-metallicity relation. We prove that these metallicity differences arise from the higher peak height in the density fluctuation field occupied by BBs and central galaxies which have collapsed into a single object earlier than surviving satellites. BBs start to form stars earlier, during the peak 3/13/2011 ΛCDM, and build up half of their final stellar mass (measured at the moment of disruption) up to four times faster than surviving satellites. Surviving satellites keep increasing their stellar masses rather quiescently down to z ≃ 1. The difference between the metallicities of satellites, BBs and central galaxies depends on the host DM halo mass, in a way that can be used as a further test for the concordance cosmology.Facultad de Ciencias Astronómicas y Geofísica

Black hole spin and radio loudness in a Λ cold dark matter universe

We use a combination of a cosmological N-body simulation of the concordance Λ cold dark matter paradigm and a semi-analytic model of galaxy formation to investigate the spin development of central supermassive black holes (BHs) and its relation to the BH host galaxy properties. In order to compute BH spins, we use the α model of Shakura & Sunyaev and consider the King et al. warped disc alignment criterion. The orientation of the accretion disc is inferred from the angular momentum of the source of accreted material, which bears a close relationship to the large-scale structure in the simulation. We find that the final BH spin depends almost exclusively on the accretion history and only weakly on the warped disc alignment. The main mechanisms of BH spin-up are found to be gas cooling processes and disc instabilities, a result that is only partially compatible with Monte Carlo models where the main spin-up mechanisms are major mergers and disc instabilities; the latter results are reproduced when implementing randomly oriented accretion discs in our model. Regarding the BH population, we find that more massive BHs, which are hosted by massive ellipticals, have higher spin values than less massive BHs, hosted by spiral galaxies. We analyse whether gas accretion rates and BH spins can be used as tracers of the radio loudness of active galactic nuclei (AGN). We find that the current observational indications of an increasing trend of radio-loud AGN fractions with stellar and BH mass can be easily obtained when placing lower limits on the BH spin, with a minimum influence from limits on the accretion rates; a model with random accretion disc orientations is unable to reproduce this trend. Our results favour a scenario where the BH spin is a key parameter to separate the radio-loud and radio-quiet galaxy populations.Facultad de Ciencias Astronomicas y Geofisica

The nature of assembly bias - II. Halo spin

We study an assembly-type bias parametrized by the dimensionless spin parameter that affects massive structures. In numerical simulations higher spin haloes are more strongly clustered than lower spin haloes of equal mass. We detect a difference of over a 30 per cent in the clustering strength for dark matter haloes of 10^13-10^14 Msun, which is similar to the result of Bett et al. We explore whether the dependence of clustering strength on halo spin is removed if we apply the redefinition of overdensity peak height proposed by Lacerna & Padilla (Paper I) obtained using assembly ages. We find that this is not the case due to two reasons. Firstly, only a few objects of low-virial mass are moved into the mass range where the spin introduces an assembly bias after using this redefinition. Secondly, this formalism does not alter the mass of massive objects. We then repeat the process of finding the redefined peak height of Paper I but using the spin. In this case, the new masses show no spin-related assembly bias but they introduce a previously absent assembly bias with respect to relative age. From this result, we conclude that the assembly-type bias with respect to the halo spin has a different origin than with respect to assembly age. The former may be due to the material from filaments, which is accreted by massive haloes, that is enhanced in high-density environments, thus causing more extreme spin values without significantly changing the formation age of the halo. In addition, high-mass objects may correspond, in some cases, to a different peak height than that suggested by their mass in numerical simulations, providing a possible explanation for the assembly bias with respect to spin. (abridged)Comment: 5 pages, 5 figures. Accepted for publication in MNRAS letter

Revealing the properties of void galaxies and their assembly using the EAGLE simulation

We explore the properties of central galaxies living in voids using the EAGLE cosmological hydrodynamic simulations. Based on the minimum void-centric distance, we define four galaxy samples: inner void, outer void, wall, and skeleton. We find that inner void galaxies with host halo masses $<10^{12}M_\odot$ have lower stellar mass and stellar mass fractions than those in denser environments, and the fraction of galaxies with star formation (SF) activity and atomic hydrogen (HI) gas decreases with increasing void-centric distance, in agreement with observations. To mitigate the influence of stellar (halo) mass, we compare inner void galaxies to subsamples of fixed stellar (halo) mass. Compared to denser environments, inner void galaxies with $M_{*}= 10^{[9.0-9.5]}M_\odot$ have comparable SF activity and HI gas fractions, but the lowest quenched galaxy fraction. Inner void galaxies with $M_{*}= 10^{[9.5-10.5]}M_\odot$ have the lowest HI gas fraction, the highest quenched fraction and the lowest gas metallicities. On the other hand, inner void galaxies with $M_{*}>10^{10.5}M_\odot$ have comparable SF activity and HI gas fractions to their analogues in denser environments. They retain the highest metallicity gas that might be linked to physical processes that act with lower efficiency in underdense regions, such as AGN feedback. Furthermore, inner void galaxies have the lowest fraction of positive gas-phase metallicity gradients, which are typically associated with external processes or feedback events, suggesting they have more quiet merger histories than galaxies in denser environments. Our findings shed light on how galaxies are influenced by their large-scale environment.Comment: 20 pages,16 figures, revised version with a discussion section and edition in the text. Accepted to MNRA