We present a spectroscopic analysis based on measurements of two mainly age-dependent spectrophotometric indices in the 4000A rest frame region, i.e. H+K(CaII) and Delta4000, for a sample of 15 ...early-type galaxies (ETGs) at 0.7 < z_{spec} < 1.1, morphologically selected in the GOODS-South field. Ages derived from the two different indices by means of the comparison with stellar population synthesis models, are not consistent with each other for at least nine galaxies (60 per cent of the sample), while for the remaining six galaxies, the ages derived from their global spectral energy distribution (SED) fitting are not consistent with those derived from the two indices. We then hypothesized that the stellar content of many galaxies is made of two stellar components with different ages. The double-component analysis, performed by taking into account both the index values and the observed SED, fully explains the observational data and improves the results of the standard one-component SED fitting in 9 out of the 15 objects, i.e. those for which the two indices point towards two different ages. In all of them, the bulk of the mass belongs to rather evolved stars, while a small mass fraction is many Gyr younger. In some cases, thanks to the sensitivity of the H+K(CaII) index, we find that the minor younger component reveals signs of recent star formation. The distribution of the ages of the younger stellar components appears uniformly in time and this suggests that small amounts of star formation could be common during the evolution of high-z ETGs. We argue the possibility that these new star formation episodes could be frequently triggered by internal causes due to the presence of small gas reservoir.
The upcoming new generation of optical spectrographs on four-meter-class telescopes will provide invaluable information for reconstructing the history of star formation in individual galaxies up to ...redshifts of about 0.7. We aim at defining simple but robust and meaningful physical parameters that can be used to trace the coexistence of widely diverse stellar components: younger stellar populations superimposed on the bulk of older ones. We produce spectra of galaxies closely mimicking data from the forthcoming Stellar Populations at intermediate redshifts Survey (StePS), a survey that uses the WEAVE spectrograph on the William Herschel Telescope. First, we assess our ability to reliably measure both ultraviolet and optical spectral indices in galaxies of different spectral types for typically expected signal-to-noise levels. Then, we analyze such mock spectra with a Bayesian approach, deriving the probability density function of r- and u-band light-weighted ages as well as of their difference. We find that the ultraviolet indices significantly narrow the uncertainties in estimating the r- and u-band light-weighted ages and their difference in individual galaxies. These diagnostics, robustly retrievable for large galaxy samples even when observed at moderate signal-to-noise ratios, allow us to identify secondary episodes of star formation up to an age of ~0.1 Gyr for stellar populations older than ~1.5 Gyr, pushing up to an age of ~1 Gyr for stellar populations older than ~5 Gyr. The difference between r-band and u-band light-weighted ages is shown to be a powerful diagnostic to characterize and constrain extended star-formation histories and the presence of young stellar populations on top of older ones. This parameter can be used to explore the interplay between different galaxy star-formation histories and physical parameters such as galaxy mass, size, morphology, and environment.
The aim of our analysis is twofold. On the one hand we are interested in addressing whether a sample of ETGs morphologically selected differs from a sample of passive galaxies in terms of galaxy ...statistics. On the other hand we study how the relative abundance of galaxies, the number density and the stellar mass density for different morphological types change over the redshift range 0.6<z<2.5. From the 1302 galaxies brighter than Ks=22 selected from the GOODS-MUSIC catalogue, we classified the ETGs on the basis of their morphology and the passive galaxies on the basis of their sSFR. We proved how the definition of passive galaxy depends on the IMF adopted in the models and on the assumed sSFR threshold. We find that ETGs cannot be distinguished from the other morphological classes on the basis of their low sSFR, irrespective of the IMF adopted in the models. Using the sample of 1302 galaxies morphologically classified into spheroidal galaxies (ETGs) and not spheroidal galaxies (LTGs), we find that their fractions are constant over the redshift range 0.6<z<2.5 (20-30% ETGs vs 70-80% LTGs). However, at z<1 these fractions change among the population of the most massive (M*>=10^(11) M_sol) galaxies, with the fraction of massive ETGs rising up to 40% and the fraction of massive LTGs decreasing down to 60%. Moreover, we find that the number density and the stellar mass density of the whole population of massive galaxies increase almost by a factor of ~10 between 0.6<z<2.5, with a faster increase of these densities for the ETGs than for the LTGs. Finally, we find that the number density of the highest-mass galaxies (M*>3-4x10^(11) M_sol) both ETGs and LTGs do not increase since z~2.5, contrary to the lower mass galaxies. This suggests that the population of the most massive galaxies formed at z>2.5-3 and that the assembly of such high-mass galaxies is not effective at lower redshift.
This paper aims at understanding if the normalization of the stellar initial mass function (IMF) of massive early-type galaxies (ETGs) varies with cosmic time and/or with mean stellar mass density ...Sigma (M*/2\pi Re^2). For this purpose we collected a sample of 18 dense (Sigma>2500 M_sun/pc^2) ETGs at 1.2<z<1.6 with available velocity dispersion sigma_e. We have constrained their mass-normalization by comparing their true stellar masses (M_true) derived through virial theorem, hence IMF independent, with those inferred through the fit of the photometry assuming a reference IMF (M_ref). Adopting the virial estimator as proxy of the true stellar mass, we have assumed for these ETGs zero dark matter (DM). However, dynamical models and numerical simulations of galaxy evolution have shown that the DM fraction within Re in dense high-z ETGs is negligible. We have considered the possible bias of virial theorem in recovering the total masses and have shown that for dense ETGs the virial masses are in agreement with those derived through more sophisticated dynamical models. The variation of the parameter Gamma = M_true/M_ref with sigma_e shows that, on average, dense ETGs at = 1.4 follow the same IMF-sigma_e trend of typical local ETGs, but with a lower mass-normalization. Nonetheless, once the IMF-sigma_e trend we have found for high-z dense ETGs is compared with that of local ETGs with similar Sigma and sigma_e, they turn out to be consistent. The similarity between the IMF-sigma_e trends of dense high-z and low-z ETGs over 9 Gyr of evolution and their lower mass-normalization with respect to the mean value of local ETGs suggest that, independently on formation redshift, the physical conditions characterizing the formation of a dense spheroid lead to a mass spectrum of new formed stars with an higher ratio of high- to low-mass stars with respect to the IMF of normal local ETGs.
Abridged We studied the size-surface brightness and the size-mass relations of a sample of 16 cluster elliptical galaxies in the mass range 10^{10}-2x10^{11} M_sun which were morphologically selected ...in the cluster RDCS J0848+4453 at z=1.27. Our aim is to assess whether they have completed their mass growth at their redshift or significant mass and/or size growth can or must take place until z=0 in order to understand whether elliptical galaxies of clusters follow the observed size evolution of passive galaxies. To compare our data with the local universe we considered the Kormendy relation derived from the early-type galaxies of a local Coma Cluster reference sample and the WINGS survey sample. The comparison with the local Kormendy relation shows that the luminosity evolution due to the aging of the stellar content already assembled at z=1.27 brings them on the local relation. Moreover, this stellar content places them on the size-mass relation of the local cluster ellipticals. These results imply that for a given mass, the stellar mass at z~1.3 is distributed within these ellipticals according to the same stellar mass profile of local ellipticals. We find that a pure size evolution, even mild, is ruled out for our galaxies since it would lead them away from both the Kormendy and the size-mass relation. If an evolution of the effective radius takes place, this must be compensated by an increase in the luminosity, hence of the stellar mass of the galaxies, to keep them on the local relations. We show that to follow the Kormendy relation, the stellar mass must increase as the effective radius. However, this mass growth is not sufficient to keep the galaxies on the size-mass relation for the same variation in effective radius. Thus, if we want to preserve the Kormendy relation, we fail to satisfy the size-mass relation and vice versa.
Abstract
The Hydra I cluster offers an excellent opportunity to study and compare the relic old stellar populations in the core of its two brightest galaxies. In addition, the differing kinematics of ...the two galaxies allows a test of the local validity of general scaling relations. In this work, we present a direct comparison employing full spectral fitting of new high-quality long-slit optical and near-infrared spectroscopic data. We retrieve age, metallicity, and 19 elemental abundances out to ∼12 kpc within each galaxy, as well as the Initial Mass Function (IMF) in their central regions. Our results suggest that the inner ∼5 kpc regions of both galaxies, despite their different masses, formed at the same time and evolved with a similar star formation timescale and chemical enrichment, confirming their early formation in the cluster buildup. Only the overall metallicity and IMF radial profiles show differences connected with their different velocity dispersion profiles. The radial trends of the IMF positively correlate with both Z/H and
σ
. While the trends of the IMF slope values with metallicity agree with a global trend for both galaxies, the trends with the velocity dispersion exhibit differences. The outer regions show signs of mixed stellar populations with large differences in chemical content compared to the centers, but with similarly old ages.
In crosses between the proline-deficient mutant homozygous for p5cs1 and heterozygous for p5cs2 (p5cs1 p5cs2/P5CS2), used as male, and different Arabidopsis mutants, used as females, the p5cs2 mutant ...allele was rarely transmitted to the outcrossed progeny, suggesting that the fertility of the male gametophyte carrying mutations in both P5CS1 and P5CS2 is severely compromised.
To confirm the fertility defects of pollen from p5cs1 p5cs2/P5CS2 mutants, transmission of mutant alleles through pollen was tested in two ways. First, the number of progeny inheriting a dominant sulfadiazine resistance marker linked to p5cs2 was determined. Second, the number of p5cs2/p5cs2 embryos was determined. A ratio of resistant to susceptible plantlets close to 50%, and the absence of aborted embryos were consistent with the hypothesis that the male gametophyte carrying both p5cs1 and p5cs2 alleles is rarely transmitted to the offspring. In addition, in reciprocal crosses with wild type, about 50% of the p5cs2 mutant alleles were transmitted to the sporophytic generation when p5cs1 p5cs2/P5CS2 was used as a female, while less than 1% of the p5cs2 alleles could be transmitted to the outcrossed progeny when p5cs1 p5cs2/P5CS2 was used as a male. Morphological and functional analysis of mutant pollen revealed a population of small, degenerated, and unviable pollen grains, indicating that the mutant homozygous for p5cs1 and heterozygous for p5cs2 is impaired in pollen development, and suggesting a role for proline in male gametophyte development. Consistent with these findings, we found that pollen from p5cs1 homozygous mutants, display defects similar to, but less pronounced than pollen from p5cs1 p5cs2/P5CS2 mutants. Finally, we show that pollen from p5cs1 p5cs2/P5CS2 plants contains less proline than wild type and that exogenous proline supplied from the beginning of another development can partially complement both morphological and functional pollen defects.
Our data show that the development of the male gametophyte carrying mutations in both P5CS1 and P5CS2 is severely compromised, and indicate that proline is required for pollen development and transmission.
Inflammatory bowel diseases (IBDs) including Crohn’s disease (CD), ulcerative colitis (UC) and inflammatory bowel disease unclassified (IBD-U) are chronic inflammatory disorders which can affect the ...gastrointestinal tract. Anti-tumor necrosis factors antibodies (anti-TNFα) such as infliximab (IFX) and adalimumab (ADA) are the first line biological therapy for severe or complicated IBDs in pediatric age. Second line therapeutic options as vedolizumab (VDZ) and ustekinumab (UST) are currently used off-label in pediatric age. Furthermore, despite optimization of biologics, a great proportion of patients may fail to respond to biologic agents (up to 30%) or lose response over the time (around 50%) hence these patients may be left without another valid therapeutic option. Consequently, several efforts have been made in the last years in order to develop new drugs and to contrive new therapeutic strategies. Small molecule drugs (SMDs) and combination therapy with either two biologic agents or with a SMD and a biological agent have recently been proposed. Data on safety and efficacy of these new therapeutic options are limited. The objective of the present review is to summarize the most up-to-date available literature in pediatric IBD.
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Double minutes (dmin), homogeneously staining regions, and ring chromosomes are vehicles of gene amplification in cancer. The underlying mechanism leading to their formation as well as their ...structure and function in acute myeloid leukemia (AML) remain mysterious. We combined a range of high-resolution genomic methods to investigate the architecture and expression pattern of amplicons involving chromosome band 8q24 in 23 cases of AML (AML-amp). This revealed that different MYC-dmin architectures can coexist within the same leukemic cell population, indicating a step-wise evolution rather than a single event origin, such as through chromothripsis. This was supported also by the analysis of the chromothripsis criteria, that poorly matched the model in our samples. Furthermore, we found that dmin could evolve toward ring chromosomes stabilized by neocentromeres. Surprisingly, amplified genes (mainly PVT1) frequently participated in fusion transcripts lacking a corresponding DNA template. We also detected a significant overexpression of the circular RNA of PVT1 (circPVT1) in AML-amp cases versus AML with a normal karyotype. Our results show that 8q24 amplicons in AML are surprisingly plastic DNA structures with an unexpected association to novel fusion transcripts and circular RNAs.
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