Spectral decomposition of starbursts and AGNs in 5-8 micron Spitzer IRS spectra of local ULIRGs

We present an analysis of the 5-8 micron Spitzer-IRS spectra of a sample of 68 local Ultraluminous Infrared Galaxies (ULIRGs). Our diagnostic technique allows a clear separation of the active galactic nucleus (AGN) and starburst (SB) components in the observed mid-IR emission, and a simple analytic model provides a quantitative estimate of the AGN/starburst contribution to the bolometric luminosity. We show that AGNs are ~30 times brighter at 6 micron than starbursts with the same bolometric luminosity, so that even faint AGNs can be detected. Star formation events are confirmed as the dominant power source for extreme infrared activity, since ~85% of ULIRG luminosity arises from the SB component. Nonetheless an AGN is present in the majority (46/68) of our sources.Comment: 5 Pages, 3 figures. MNRAS Letters, Accepte

Hyperosmotic priming of arabidopsis seedlings establishes a long-term somatic memory accompanied by specific changes of the epigenome

<p>Background: In arid and semi-arid environments, drought and soil salinity usually occur at the beginning and end of a plant's life cycle, offering a natural opportunity for the priming of young plants to enhance stress tolerance in mature plants. Chromatin marks, such as histone modifications, provide a potential molecular mechanism for priming plants to environmental stresses, but whether transient exposure of seedlings to hyperosmotic stress leads to chromatin changes that are maintained throughout vegetative growth remains unclear.</p> <p>Results: We have established an effective protocol for hyperosmotic priming in the model plant Arabidopsis, which includes a transient mild salt treatment of seedlings followed by an extensive period of growth in control conditions. Primed plants are identical to non-primed plants in growth and development, yet they display reduced salt uptake and enhanced drought tolerance after a second stress exposure. ChIP-seq analysis of four histone modifications revealed that the priming treatment altered the epigenomic landscape; the changes were small but they were specific for the treated tissue, varied in number and direction depending on the modification, and preferentially targeted transcription factors. Notably, priming leads to shortening and fractionation of H3K27me3 islands. This effect fades over time, but is still apparent after a ten day growth period in control conditions. Several genes with priming-induced differences in H3K27me3 showed altered transcriptional responsiveness to the second stress treatment.</p> <p>Conclusion: Experience of transient hyperosmotic stress by young plants is stored in a long-term somatic memory comprising differences of chromatin status, transcriptional responsiveness and whole plant physiology.</p&gt

The circumnuclear environment of IRAS 20551-4250 a case study of AGN/Starburst connection for JWST

We present a general review of the current knowledge of IRAS 20551-4250 and its circumnuclear environment. This Ultraluminous Infrared Galaxy is one of the most puzzling sources of its class in the nearby Universe: the near-IR spectrum is typical of a galaxy experiencing a very intense starburst, but a highly obscured active nucleus is identified beyond 5 micron and possibly dominates the mid-IR energy output of the system. At longer wavelengths star formation is again the main driver of the global spectral shape and features. We interpret all the available IR diagnostics in the framework of simultaneous black hole growth and star formation, and discuss the key properties that make this source an ideal laboratory for the forthcoming James Webb Space Telescope.Comment: 19 pages, 7 figures, 2 tables. Accepted for pubblication in Advances in Astronomy. To appear in the special issue: "Seeking for the Leading Actor on the Cosmic Stage: Galaxies versus Supermassive Black Holes

The blue sky of GJ3470b: the atmosphere of a low-mass planet unveiled by ground-based photometry

GJ3470b is a rare example of a "hot Uranus" transiting exoplanet orbiting a nearby M1.5 dwarf. It is of crucial interest for atmospheric studies because it is one of the most inflated low-mass planets known, bridging the boundary between "super-Earths" and Neptunian planets. We present two new ground-based light curves of GJ3470b gathered by the LBC camera at the Large Binocular Telescope. Simultaneous photometry in the ultraviolet (lambda_c = 357.5 nm) and optical infrared (lambda_c = 963.5 nm) allowed us to detect a significant change of the effective radius of GJ3470b as a function of wavelength. This can be interpreted as a signature of scattering processes occurring in the planetary atmosphere, which should be cloud-free and with a low mean molecular weight. The unprecedented accuracy of our measurements demonstrates that the photometric detection of Earth-sized planets around M dwarfs is achievable using 8-10m size ground-based telescopes. We provide updated planetary parameters, and a greatly improved orbital ephemeris for any forthcoming study of this planet.Comment: 8 pages, 6 figures, 1 table; accepted for publication in A&

A gas-rich AGN near the centre of a galaxy cluster at z ~ 1.4

The formation of the first virialized structures in overdensities dates back to ~9 Gyr ago, i.e. in the redshift range z ~ 1.4 - 1.6. Some models of structure formation predict that the star formation activity in clusters was high at that epoch, implying large reservoirs of cold molecular gas. Aiming at finding a trace of this expected high molecular gas content in primeval clusters, we searched for the 12CO(2-1) line emission in the most luminous active galactic nucleus (AGN) of the cluster around the radio galaxy 7C 1756+6520 at z ~ 1.4, one of the farthest spectroscopic confirmed clusters. This AGN, called AGN.1317, is located in the neighbourhood of the central radio galaxy at a projected distance of ~780 kpc. The IRAM Plateau de Bure Interferometer was used to investigate the molecular gas quantity in AGN.1317, observing the 12CO(2-1) emission line. We detect CO emission in an AGN belonging to a galaxy cluster at z ~ 1.4. We measured a molecular gas mass of 1.1 x 10^10 Msun, comparable to that found in submillimeter galaxies. In optical images, AGN.1317 does not seem to be part of a galaxy interaction or merger.We also derived the nearly instantaneous star formation rate (SFR) from Halpha flux obtaining a SFR ~65 Msun/yr. This suggests that AGN.1317 is actively forming stars and will exhaust its reservoir of cold gas in ~0.2-1.0 Gyr.Comment: 5 pages, 3 figures, accepted for publication in Astronomy & Astrophysic

The HH34 outflow as seen in [FeII]1.64um by LBT-LUCI

Dense atomic jets from young stars copiously emit in [FeII] IR lines, which can, therefore, be used to trace the immediate environments of embedded protostars. We want to investigate the morphology of the bright [FeII] 1.64um line in the jet of the source HH34 IRS and compare it with the most commonly used optical tracer [SII]. We analyse a 1.64um narrow-band filter image obtained with the Large Binocular Telescope (LBT) LUCI instrument, which covers the HH34 jet and counterjet. A Point Spread Function (PSF) deconvolution algorithm was applied to enhance spatial resolution and make the IR image directly comparable to a [SII] HST image of the same source. The [FeII] emission is detected from both the jet, the (weak) counter-jet, and from the HH34-S and HH34-N bow shocks. The deconvolved image allows us to resolve jet knots close to about 1\arcsec from the central source. The morphology of the [FeII] emission is remarkably similar to that of the [SII] emission, and the relative positions of [FeII] and [SII] peaks are shifted according to proper motion measurements, which were previously derived from HST images. An analysis of the [FeII]/[SII] emission ratio shows that Fe gas abundance is much lower than the solar value with up to 90% of Fe depletion in the inner jet knots. This confirms previous findings on dusty jets, where shocks are not efficient enough to remove refractory species from grains.Comment: 5 pages, 4 figures, note accepted by A&

Informed pair selection for self-paced metric learning in Siamese neural networks.

Siamese Neural Networks (SNNs) are deep metric learners that use paired instance comparisons to learn similarity. The neural feature maps learnt in this way provide useful representations for classification tasks. Learning in SNNs is not reliant on explicit class knowledge; instead they require knowledge about the relationship between pairs. Though often ignored, we have found that appropriate pair selection is crucial to maximising training efficiency, particularly in scenarios where examples are limited. In this paper, we study the role of informed pair selection and propose a 2-phased strategy of exploration and exploitation. Random sampling provides the needed coverage for exploration, while areas of uncertainty modeled by neighbourhood properties of the pairs drive exploitation. We adopt curriculum learning to organise the ordering of pairs at training time using similarity knowledge as a heuristic for pair sorting. The results of our experimental evaluation show that these strategies are key to optimising training