1,193 research outputs found
A population of high-velocity absorption-line systems residing in the Local Group
Aims. We aim to investigate the ionisation conditions and distances of
Galactic high-velocity clouds (HVCs) in the Galactic halo and beyond in the
direction of the Local Group (LG) barycentre and anti-barycentre, by studying
spectral data of 29 extragalactic background sources obtained with Cosmic
Origins Spectropgraph (COS) installed on the Hubble Space Telescope (HST).
Methods. We model column-densities of low, intermediate, and high ions, such as
Si II, C II, Si III, Si IV, and C IV and use this to construct a set of Cloudy
ionisation models. Results. In total, we found 69 high-velocity absorption
components along the 29 lines of sight. The ones in the direction of the LG
barycentre span the entire range of studied velocities, 100 \lesssim
|v_{LSR}|\lesssim 400 km s^-1, while the anti-barycentre sample has velocities
up to about 300 km s^-1. For 49 components, we infer the gas densities. In the
direction of the LG barycentre, the gas densities exhibit a large range between
log n_H=-3.96 to -2.55, while in the anti-barycentre direction the densities
are systematically higher, log n_H>-3.25. The barycentre absorbers can be split
into two groups based on their density: a high density group with log
n_H>-3.54, which can be affected by the Milky Way radiation field, and a low
density group (log n_H \leq -3.54). The latter has very low thermal pressures
of P/k<7.3 K cm^-3. Conclusions. Our study shows that part of the absorbers in
the LG barycentre direction trace gas at very low gas densities and thermal
pressures. Such properties indicate that these absorbers are located beyond the
virial radius of the Milky Way. Our study also confirms results from earlier,
single-sightline studies, suggesting the presence of a metal-enriched
intragroup medium filling the LG near its barycentre.Comment: Accepted for publication in A&A. 12 pages, 11 figure
Building Blocks in Hierarchical Clustering Scenarios and their Connection with Damped Ly Systems
We carried out a comprehensive analysis of the chemical properties of the
interstellar medium (ISM) and the stellar population (SP) of current normal
galaxies and their progenitors in a hierarchical clustering scenario. We
compared the results with observations of Damped Lyman- systems (DLAs)
under the hypothesis that, at least, part of the observed DLAs could originate
in the building blocks of today normal galaxies. We used a hydrodynamical
cosmological code which includes star formation and chemical enrichment.
Galaxy-like objects are identified at and then followed back in time.
Random line-of-sights (LOS) are drawn through these structures in order to
mimic Damped Lyman systems. We then analysed the chemical properties
of the ISM and SP along the LOS. We found that the progenitors of current
galaxies in the field with mean and virial circular velocity of
could be the associated DLA galaxies. For these systems
we detected a trend for to increase with redshift.(Abridged)Comment: 15 pages, 11 Postscript figures. Accepted to MNRA
Dissecting the Mechanism of Action of Spiperoneâ A Candidate for Drug Repurposing for Colorectal Cancer
Temperature-dependent development of the cycad aulacaspis scale, aulacaspis yasumatsui (Hemiptera: Diaspididae)
Egg duration period, immature development time, and pre-oviposition period of the cycad aulacaspis scale, Aulacaspis yasumatsui Takagi, were measured at 9 constant temperatures in the laboratory. Egg duration period ranged from 15 d at 20°C to 7 d at 30°C. First instar development time was 30 d at 18°C but only 4 d at 35°C. No first instars completed development below 18°C or above 35°C. Development time of second instar females ranged from 19 d at 18 and 20°C to 9 d at 30°C. Development time of male second instar + pupa ranged from 15 d at 20°C to 910 d at 2532°C. Pre-oviposition period averaged 14 d at 20°C to 8 d at 25 32°C; no females laid eggs at 18 and 35°C. The lowest temperature threshold for all stages ranged from 8 to 12°C and 538 degree-days were required for female immature development in a linear model. Development rates of the scale are compared to those of 3 of its natural enemies, Cybocephalus nipponicus Endrdy-Younga, Rhyzobius lophanthae (Blaisdell), and Coccobius fulvus (Compere and Annecke)
Pengaruh Otonomi Daerah Terhadap Percepatan Pembangunan Infrastruktur Di Kabupaten Bolaang Mongondow Utara
North Bolaang Mongondow Regency formed as a result of the nuances of reform and regional autonomy. North Bolaang Mongondow with its existence as an expansion are after the implementation of regional autonomy, the maters that were examined in this study was: how much influence among the variables of human resources, financial resources/funding, policy development to variable acceleration of infrastructure development in North Bolaang Mongondow. The research method used was research using both primary and secondary data, by dividing the questionnaire and secondary data collection agencies. Inference and descriptive statistics used in this research is simple regression and multiple regressions. Respondents totaled 75 people, drawn by simple random sampling. The results of this study show that there are significant human resource affect toward infrastructure acceleration; the higher the human resource, then, the better the acceleration of the development. there are significant financial resources impact on infrastructure acceleration; the higher the financial resources, then, the faster the infrastructure acceleration is. There are significant effects of the development policy toward the infrastructure acceleration; the higher the development policy, then, the better the infrastructure acceleration. It is advised that human resource should be improved and developed through civil service recruitment with accurate competition and qualification, technical tutor related to infrastructure acceleration, and incentive to existing employees. Besides, there should be researches done in relation to financial resources aspects in North Bolaang Mongondow Region in order to infrastructure development acceleration. There also should be further researches especially about divisions of development policies between the development done by both legislative and executive government
MicroRNA-mediated regulatory circuits: outlook and perspectives
MicroRNAs have been found to be necessary for regulating genes implicated in almost all signaling pathways, and consequently their dysfunction influences many diseases, including cancer. Understanding of the complexity of the microRNA-mediated regulatory network has grown in terms of size, connectivity and dynamics with the development of computational and, more recently, experimental high-throughput approaches for microRNA target identification. Newly developed studies on recurrent microRNA-mediated circuits in regulatory networks, also known as network motifs, have substantially contributed to addressing this complexity, and therefore to helping understand the ways by which microRNAs achieve their regulatory role. This review provides a summarizing view of the state-of-the-art, and perspectives of research efforts on microRNA-mediated regulatory motifs. In this review, we discuss the topological properties characterizing different types of circuits, and the regulatory features theoretically enabled by such properties, with a special emphasis on examples of circuits typifying their biological significance in experimentally validated contexts. Finally, we will consider possible future developments, in particular regarding microRNA-mediated circuits involving long non-coding RNAs and epigenetic regulators
Chemo-Archaeological Downsizing in a Hierarchical Universe: Impact of a Top Heavy IGIMF
We make use of a semi-analytical model of galaxy formation to investigate the
origin of the observed correlation between [a/Fe] abundance ratios and stellar
mass in elliptical galaxies. We implement a new galaxy-wide stellar initial
mass function (Top Heavy Integrated Galaxy Initial Mass Function, TH-IGIMF) in
the semi-analytic model SAG and evaluate its impact on the chemical evolution
of galaxies. The SFR-dependence of the slope of the TH-IGIMF is found to be key
to reproducing the correct [a/Fe]-stellar mass relation. Massive galaxies reach
higher [a/Fe] abundance ratios because they are characterized by more top-heavy
IMFs as a result of their higher SFR. As a consequence of our analysis, the
value of the minimum embedded star cluster mass and of the slope of the
embedded cluster mass function, which are free parameters involved in the
TH-IGIMF theory, are found to be as low as 5 solar masses and 2, respectively.
A mild downsizing trend is present for galaxies generated assuming either a
universal IMF or a variable TH-IGIMF. We find that, regardless of galaxy mass,
older galaxies (with formation redshifts > 2) are formed in shorter time-scales
(< 2 Gyr), thus achieving larger [a/Fe] values. Hence, the time-scale of galaxy
formation alone cannot explain the slope of the [a/Fe]-galaxy mass relation,
but is responsible for the big dispersion of [a/Fe] abundance ratios at fixed
stellar mass.We further test the hyphothesis of a TH-IGIMF in elliptical
galaxies by looking into mass-to-light ratios, and luminosity functions. Models
with a TH-IGIMF are also favoured by these constraints. In particular,
mass-to-light ratios agree with observed values for massive galaxies while
being overpredicted for less massive ones; this overprediction is present
regardless of the IMF considered.Comment: 24 pages, 15 figures, 2 tables. (Comments most welcome). Summited to
MNRA
Effects of AGN feedback on ÎCDM 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 (ÎCDM) 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 âČ z âČ 5). It also allows us to have a population of massive galaxies already in place at z âł 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 AstronĂłmicas y GeofĂsicasInstituto de AstrofĂsica de La Plat
Effects of AGN feedback on ÎCDM 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 (ÎCDM) 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 âČ z âČ 5). It also allows us to have a population of massive galaxies already in place at z âł 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 AstronĂłmicas y GeofĂsicasInstituto de AstrofĂsica de La Plat
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