The Infrared Telescope Facility (IRTF) spectral library: spectral diagnostics for cool stars

The near-infrared (NIR) wavelength range offers some unique spectral features, and it is less prone to the extinction than the optical one. Recently, the first flux calibrated NIR library of cool stars from the NASA Infrared Telescope Facility (IRTF) have become available, and it has not been fully exploited yet. We want to develop spectroscopic diagnostics for stellar physical parameters based on features in the wavelength range 1-5 micron. In this work we test the technique in the I and K bands. The study of the Y, J, H, and L bands will be presented in the following paper. An objective method for semi-empirical definition of spectral features sensitive to various physical parameters is applied to the spectra. It is based on sensitivity map--i.e., derivative of the flux in the spectra with respect to the stellar parameters at a fixed wavelength. New optimized indices are defined and their equivalent widths (EWs) are measured. A number of sensitive features to the effective temperature and surface gravity are re-identified or newly identified clearly showing the reliability of the sensitivity map analysis. The sensitivity map allows to identify the best bandpass limits for the line and nearby continuum. It reliably predicts the trends of spectral features with respect to a given physical parameter but not their absolute strengths. Line blends are easy to recognize when blended features have different behavior with respect to some physical stellar parameter. The use of sensitivity map is therefore complementary to the use of indices. We give the EWs of the new indices measured for the IRTF star sample. This new and homogeneous set of EWs will be useful for stellar population synthesis models and can be used to get element-by-element abundances for unresolved stellar population studies in galaxies.Comment: 46 pages, 27 figures, accepted for publication on Astronomy and Astrophysic

Modelo de edificação para a produção de leitões em cama sobreposta.

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Near-infrared spectroscopic indices for unresolved stellar populations: I. Template galaxy spectra

Context. A new generation of spectral synthesis models has been developed in recent years, but there is no matching set of template galaxy spectra, in terms of quality and resolution, for testing and refining the new models. Aims: Our main goal is to find and calibrate new near-infrared spectral indices along the Hubble sequence of galaxies which will be used to obtain additional constraints to the population analysis based on medium-resolution integrated spectra of galaxies. Methods: Spectra of previously studied and well-understood galaxies with relatively simple stellar populations (e.g., ellipticals or bulge dominated galaxies) are needed to provide a baseline data set for spectral synthesis models. Results: X-shooter spectra spanning the optical and infrared wavelengths (350-2400 nm) of bright nearby elliptical galaxies with a resolving power of R \u2dc 4000-5400 were obtained. Heliocentric systemic velocity, velocity dispersion, and Mg, Fe, and H\u3b2 line-strength indices are presented. Conclusions: We present a library of very-high-quality spectra of galaxies covering a large range of age, metallicity, and morphological type. Such a dataset of spectra will be crucial to addressing important questions of the modern investigation concerning galaxy formation and evolution

Comparing 17-β-estradiol supply strategies for applying the XVE-Cre/loxP system in grape gene transfer (Vitis vinifera L.)

Assays for enhancing the performance of 17-β-estradiol induction in the XVE-Cre/loxP system were performed on two transgenic 'Brachetto' plants obtained with the pX6-pKcpGVA construct, which is derived from the chemical-inducible pX6 vector carrying the neomycin phosphotransferase (nptII) gene and the XVE-Cre/loxP sequence. The 17-β-estradiol supply is expected to induce Cre recombinase expression resulting in nptII gene removal. We compared different hormone supply strategies during shoot organogenesis from meristematic proliferative tissue (MPT) or from the cut surface between leaf and petiole (SOLP) or during micropropagation from bud (MB). The effectiveness of the estradiol induction was evaluated on different tissues of the regenerated plantlets by means of nptII copy number quantification with Real time PCR. Results showed that the Cre/loxP inducible system functions effectively – however with different efficiencies- in both root and leaf tissues, and that micropropagation from buds combined with constant wetting with 17-β-estradiol is the most efficient and reproducible strategy for effective in vivo hormone induction.

Emission of correlated photon pairs from superluminal perturbations in dispersive media

We develop a perturbative theory that describes a superluminal refractive perturbation propagating in a dispersive medium and the subsequent excitation of the quantum vacuum zero-point fluctuations. We find a process similar to the anomalous Doppler effect: photons are emitted in correlated pairs and mainly within a Cerenkov-like cone, one on the forward and the other in backward directions. The number of photon pairs emitted from the perturbation increases strongly with the degree of superluminality and under realizable experimental conditions, it can reach up to ~0.01 photons per pulse. Moreover, it is in principle possible to engineer the host medium so as to modify the effective group refractive index. In the presence of "fast light" media, e.g. a with group index smaller than unity, a further ~10x enhancement may be achieved and the photon emission spectrum is characterized by two sharp peaks that, in future experiments would clearly identify the correlated emission of photon pairs.Comment: 9 pages, 7 figure

Kinematic and stellar population properties of the counter-rotating components in the S0 galaxy NGC 1366

Context. Many disk galaxies host two extended stellar components that rotate in opposite directions. The analysis of the stellar populations of the counter-rotating components provides constraints on the environmental and internal processes that drive their formation. Aims. The S0 NGC 1366 in the Fornax cluster is known to host a stellar component that is kinematically decoupled from the main body of the galaxy. Here we successfully separated the two counter-rotating stellar components to independently measure the kinematics and properties of their stellar populations. Methods. We performed a spectroscopic decomposition of the spectrum obtained along the galaxy major axis and separated the relative contribution of the two counter-rotating stellar components and of the ionized-gas component. We measured the line-strength indices of the two counter-rotating stellar components and modeled each of them with single stellar population models that account for the \u3b1/Fe overabundance. Results. We found that the counter-rotating stellar component is younger, has nearly the same metallicity, and is less \u3b1/Fe enhanced than the corotating component. Unlike most of the counter-rotating galaxies, the ionized gas detected in NGC 1366 is neither associated with the counter-rotating stellar component nor with the main galaxy body. On the contrary, it has a disordered distribution and a disturbed kinematics with multiple velocity components observed along the minor axis of the galaxy. Conclusions. The different properties of the counter-rotating stellar components and the kinematic peculiarities of the ionized gas suggest that NGC 1366 is at an intermediate stage of the acquisition process, building the counter-rotating components with some gas clouds still falling onto the galaxy. \ua9 ESO 2017

A regulative epigenetic circuit supervised by HDAC7 represses IGFBP6 and IGFBP7 expression to sustain mammary stemness

Background: In the breast, the pleiotropic epigenetic regulator HDAC7 can influence stemness. Materials & Methods: The authors used MCF10 cells knocked-out for HDAC7 to explore the contribution of HDAC7 to IGF1 signaling. Results: HDAC7 buffers H3K27ac levels at the IGFBP6 and IGFBP7 genomic loci and influences their expression. In this manner, HDAC7 can tune IGF1 signaling to sustain stemness. In HDAC7 knocked-out cells, RXRA promotes the upregulation of IGFBP6/7 mRNAs. By contrast, HDAC7 increases FABP5 expression, possibly through repression of miR-218. High levels of FABP5 can reduce the delivery of all-trans-retinoic acid to RXRA. Accordingly, the silencing of FABP5 increases IGFBP6 and IGFBP7 expression and reduces mammosphere generation. Conclusion: The authors propose that HDAC7 controls the uptake of all-trans-retinoic acid, thus influencing RXRA activity and IGF1 signaling